This is only a preview of the October 1988 issue of Silicon Chip. You can view 46 of the 100 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "High Performance FM Antenna":
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SERVICING -
HIFI -
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5-element
FM antenna
Matchbox crystal set
Hifi review:
Yamaha's brilliant
new CD player
- -
Plus - the Original & Best TV Serviceman, Vintage
Radio, The Way I See It, the Evolution of Electric
Railways
High Performance In
Your Shirt Pocket!
3 1/2 digit LCD Display
Ranes
Max Res Accurac
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0.5% + 1dig
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Built In Diode Check,
Lo-Power Ohms &
Continuity Test Beeper
Memory Function for
Relative Readings
(DM6235 & DM6335)
Autoranging
Manual Ranging
Over-Ride
(DM6235 & DM6335)
One Year Warrant
Hold Reading Function
(DM6335)
10A Range
Automatic
Current
Limiting
Overload Protected to
1000Vdc/750Vac
$88.80
$99.60
Look At The Low Pricesl
DM6135 Autoranging
3 1/2 digit 1OA ac/dc
DM6235 As above
with Memory
function and Range Hold
Prices include 9V Battery and High Quality Silicon
Rubber Test Leads with Screw-On Alligator Clips
DM6335 As above
with Data Hold
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Dealer enquiries welcome. Call (02)736 2243
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• Auto-Catt Industries 526 2222 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ebson 707 2111
• Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Pty Ltd 698 4776
• Petro-Ject 569 9655 • David Reid 267 1385 • Digitel 709 6511 • Geoff Wood 427 1676
N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999
QUEENSLAND Auslec (07) 854 1661 • G. Brown Group (0 7) 252 3876 • Petro -Ject (075) 91 4199
• St Lucia Electronics 52 7466 • Cliff Electronics 341 4655 • L.E.Boughen 369 1277
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• Thompson Instruments (Cairns) (070) 51 2404 • Nortek (Townsville)(077) 79 8600
S.AUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688
• J Blackwood & Sons 46 0391 • Petro-Ject 363 1353
TASMANIA George Harvey (003) 31 6533 (002) 34 2233
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W AUSTRALIA Atkins Carlyle 481 1233 • Debbie Instruments 276 8888 • Protronics 362 1044
OCTOBER 1 988
FEATURES
THIS STEREO FM transmitter
can broadcast your favourite
CDs to your personal portable or
to your car's AM/FM radio. It's
based on a single chip so that
it's easy to build. Details page 14.
4 Electronics & Brock's BMW Blaster by Leo Simpson
Sensors monitor the car's performance
20 Yamaha's Brilliant New CD Player by Leo Simpson
Uses 8-times oversampling for improved specs
76 The Evolution of Electric Railways by Bryan Maher
Pt.12: Queensland's powerful new electric locomotives
PROJECTS TO BUILD
14 Build an FM Stereo Transmitter by John Clarke
One IC lets you listen to CDs on your W alkman
28 High Performance FM Antenna by Bob Flynn
5-element design fa~ improved fringe area reception
52 The Classic Matchbox Crystal Set by Steve Payor
Super-sensitive circuit pulls in the stations
64 The Led-Light House Number by John Clarke
Turns on automatically at dusk
IF YOU CAN DO BASIC
metalwork you can build this
high-performance FM antenna.
It's a 5-element Yagi design
that's just the shot for fringe
area reception. See page 28.
_ _, . , _ _ , . _ _ _ _ A
> >
~ .,_,-i'::,~'
❖,_..,.
SPECIAL COLUMNS
8 Vintage Radio by John Hill
Checking out the power supply
36 The Way I See It by Neville Williams
Fly by wire: is it safe from electromagnetic interference?
44 Serviceman's Log by the original TV serviceman
Curing woolly pictures at Wollongong
84 Amateur Radio by Garry Cratt
Convert a CB radio to the 28MHz amateur band
¼i
...
~-~
~'•,-: .. _~--·~ ~t __ ,:
• - .- ,
~ "
~;;~
,+1V'N.'$"'#>'-"',ili;'/ ~
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P///<%%
YAMAHA'S NEW CDX-1110
CD player features 8-times
oversampling for unrivalled
linearity and brilliant signal-tonoise ratio. Our review starts on
page 20.
DEPARTMENTS
2 Publisher's Letter
3 Mailbag
61 Subscription Page
70 Circuit Notebook
81 Back Issues
90 Product Showcase
97 Ask Silicon Chip
99 Notes & Errata
100 Market Centre
YOUR HOUSE WILL BE easy to
find at night with this house
number. It uses LEDs that turn
on automatically at dusk and
then turn off again some four
hours later. Construction starts
on page 64.
OCTOBER 1988
1
SILICON CHIP
Publisher & Editor-in-Chief
Leo Simpson, B.Bus.
Editor
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Advertising Manager
Paul Buchtmann
Regular Contributors
Neville Williams, FIREE, VK2XV
Bryan Maher, M.E. B.Sc.
Jim Yalden, VK2YGY
Garry Cratt, VK2YBX
Jim Lawler, MTETIA
John Hill
David Whitby
Photography
Bob Donaldson
Editorial Advisory Panel
Philip Watson , VK2ZPW
Norman Marks
Steve Payor, B.Sc., B.E .
SILICON CHIP is published 1 2 times
a year by Silicon Chip Publications Pty Ltd. All material
copyright (c). No part of the contents of this publication may be
reproduced without prior written
consent of the publisher. Kitset
suppliers may not photostat articles without written permission
of the publisher.
Magazine
Printers Pty Ltd, Waterloo, NSW
2017 .
Printing: Masterprint Pty Ltd,
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Distribution: Network Distribution
Company.
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Australia. For overseas rates,
refer to the subscription page in
this issue .
Liability: Devices or circuits
described in SILICON CHIP may be
covered by patents. SILICON CHIP
disclaims any liability for the infringement of such patents by the
manufacturing or selling of any
such equipment.
Address all mail to: Silicon Chip
Publications Pty Ltd, PO Box
139, Collaroy Beach, NSW
2097. Phone (02) 982 3935.
ISSN 1030-2662
* Recommended and maximum
Australian price only.
2
SILICON CHIP
PUBLISHER'S LE't-lER
Those wonderful infrared
remote controls
Ever stopped to consider just how wonderful some electronic products are? My favourites are the remote controls for my VCR and TV
set. And I know that anyone who has a remote control for their TV set
loves it too. Don't like that program or that advert? Just zap it and
something else is on the screen.
Have you ever stopped to watch how people use their remotes?
Some people have it on the table in front of them and they stab the buttons viciously to erase the offending images. Others hold the remote
control in their hand and derisively thrust the unit at the TV as they
zap the program off the screen. Or perhaps they just casually render
the talking head voiceless so that adverts can be ignored.
And consider how handy it is to be able to "fast forward" through
the commercials when you are watching a videotape.
So attached to the remote am I that I become irritated if I can't immediately reach it while I am watching the Teev. But aside from the utter convenience, remote controls are a wonderful piece of technology.
First of all, they employ one or two infrared light emitting diodes
which are pulsed on and off at a rate of around 10kHz or so. The
pulses are actually a serial data stream corresponding to the button
you've pushed. Each button, and there may be 40 buttons or more on
some complex remotes, has its own special data code.
These pulses of infrared light from the remote transmitter (you
could almost think of them as pulses of heat) are received by an infrared detector (diode or phototransistor) inside the appliance and
converted to an electrical signal. This is fed to an amplifier which
filters out all the noise and then passes it to a decoder.
Normally the decoder is a dedicated microprocessor which puts out
digital signals in response to your commands. Some of these digital
signals will be converted to analog signals, to change the volume setting or the DC voltage to the varicap tuner in the VCR or TV set or to do
some other task.
All this happens within a few tens of milliseconds of you pressing a
button. And when you're not pressing a button, the encoder chip inside
the control is quiescent, draining perhaps only a fraction of a
microamp from the batteries. No wonder the batteries last a long time.
We've come to accept this wonderful technology as nothing special.
It's just one of the features of electronic appliances. But next time you
pick up your remote control to zap an advert, think about the complex
series of electronic events you set in motion as you push the button.
And we just take it all for granted.
Leo Simpson
MAILBAG
Non-serviceable appliances
Maybe even an advert in the
I sympathise with the comments classified section of this wonderful
electronics journal might be the way.
about non-serviceable appliances,
Please.
minor and major, in The Way I See It
Grant Lockie
(June 1988). It is evident these are
Mangakino, NZ
designed for the consumer throwSorry, but we really have sold out of
away market and that this market acthe January issue. If anyone has a
cepts such a philosophy.
spare copy, we'd be happy to pass it on
The label "no user-serviceable
to our reader (free of charge, of
parts inside" is perfectly honest, as
course).
they do not contain bulbs in bayonet
sockets. "Refer servicing to qualified
On aesthetics and attenuation
personnel" is positively a compliAs usual, another enjoyable issue
ment!
of SILICON CHIP has come out this
"Return to supplier for repair" is,
month. I gather from reading the
on the other hand, dishonest outside
Studio 200 Control Unit articles it
the warranty period for this breed of would be a superb piece of hifi gear
throw-aways as the exercise is, by but I was bit taken aback by the
definition, pointless. The genuine ex- starkness of the control markings on
ception relates to ionisation type (the the front panel. I feel a few abbreviabest) smoke detectors, although tions would have looked better (ie,
truthfully, they are not hazardous.
bal, mon, vol) and the Source label
"Not able to be repaired" or under the selector eliminated as this
similar appears occasionally and is
is self explanatory.
economically, but not usually
The same goes for the use of the
technically, honest.
tone defeat switch which is obvious
While glued assembly makes
simply by using it - why not label it
repair difficult as with the more ex- "defeat". Your logo would have lookotic "snap" construction, heat- ed nicer in a not-so-heavy block print
rivetting is fairly easy to undo and re- . or some other fancier writing and I
do and if one were able to find a real hate the line under the name.
engineering shop anymore, the
If I make this unit I will make my
"weird" screwdrivers are probably own front panel for sure as
obtainable. Also, a toolmaker could everything else is great. Hope you
supply one if a repairer wanted to use don't mind the criticism; it keeps you
it often enough.
on your toes.
You are probably closest to the
One other point: why don't you attruth when you consider the legal tenuate the CD input. If you have 2
aspect; ie, that of the manufacturer volts output from CDs and a line input
providing no "reasonable" ~eans of of 240mV, won't this mean that the
repair to exempt itself from any con- volume control would be turned down
sequent liability.
more for CD than for other inputs? I
realise you don't get overload with
P. B. Webster, VK2BZC
the volume control ahead of the rest
Lake Cathie, NSW
of the circuitry but one would have to
Craving for a January issue
remember to turn it down more for
· Thanks for your fast response to CDs.
my order for a subscription and back
Keep up the good work and looking
issues. I have now read them all and forward to next month's issue.
in a word, "cracker". Unfortunately,
Paul Gee
Orient Point, NSW
you were not able to supply a copy of
the January issue, so now it's time to
Nah, we don't mind criticism. Weigget on my knees and beg, grovel,
nore most of it anyway. We think the
plead and, if necessary, . prostrate labelling on most hifi equipment is far
myself and even pay unreasonable too small to be easily readable by most
of the population. Be honest now: can
amounts of hard-earned for maybe a
spare slightly dog-eared old office you read the control labels on most hifi
copy, or a return from a newsagent gear when at arm's length? If you can,
you are fortunate.
from the back of beyond.
SILICON CHIP,
PO Box 139,
Collaroy Beach 2097.
There is no need for attenuation of
CD signals. Remember that the 2 volt
RMS (2.B volts peak) output only occurs on very loud musical peaks; normal program levels are a great deal
lower. What this means is that there is
usually not much difference in volume
settings as you switch from phono to
tuner to CD and so on. It just isn't a
problem. And if you attenuate the
signal, there will inevitably be a
reduction. in the signal-to-noise ratio.
Commercial stereo amps normally
don't attenuate either.
Query on circuit diagrams
I was most impressed with the July
1988 issue of SILICON CHIP particularly the presentation of the Discolight. I
find the circuit diagrams in your
magazine well laid out and easy to
follow.
I have just one small quibble.
Shouldn't the inputs of the unused
CMOS gates be shown tied high or
low? I am sure they actually are tied
one way or the other on the printed
circuit board but possibly they should
be shown on the circuit too.
Keep up the good work.
A. Lackey
Collaroy Plateau, NSW
We agree that unused CMOS gate inputs must be tied high or low otherwise it is possible that they may
oscillate. They are tied on the printed
board of the Discolight. However, we
make a special effort to make the circuit diagrams uncluttered and easy
to follow. That means that we leave
out the more or less extraneous details,
such as unused CMOS gates. After all,
showing these gates would not aid
understanding of the circuit, would it?
UHF remote transmitter/receiver
Why does the UHF remote
transmitter/receiver operate on
304MHz? Perhaps I missed seeing it
but I found no information in your
magazine which explains this point
and, for example, discusses the
choice of 27.145MHz for commercial
garage door operators etc.
I suspect that the Department of
Communications and the Standards
Association of Australia have an influence and I would appreciate a
Continued on page 96
OCTOBER 1988
3
BROCK'S BMW:
ELECTRONICS UPDATES
On October 2nd, millions of Australians will watch
the motor racing at Bathurst. In particular, their
eyes will be on Peter Brock and his co-drivers.
Computers will be watching him too as he strives
to get the very best out of his BMW M3 sedan.
By LEO SIMPSON
Just how do you screw the very
maximum performance out of a racing sedan over a distance of
1000km without running the risk of
blowing it up before the finish?
That is a question which continually haunts racing drivers and their
backup teams as their cars hurtle
around the track. More than any
other driver, Peter Brock has
always managed to perform this
task to the optimum. They don't call
him "Peter Perfect" for nothing.
That he has won more races than
anyone else is a tribute to his
superb feeling for motor cars. He
has been able to judge just how
hard to push a car while still keeping enough in reserve to be able to
finish the race. In other words,
there is more to winning a race
than just being able to go fastest
around the track.
But as motor racing becomes
more competitive, even superlative
drivers like Peter Brock need more
than just the "seat of their pants"
to keep them out in front. And this is
where computers are being brought
into the picture.
Not that computers have not
been involved in motor racing for a
number of years. Most of the cars
circulating around the track at
Bathurst this year will have one or
more on-board computers in their
' ' engine management systems''.
These systems are used to control
the ignition timing and fuel injection.
The problem with existing engine
management systems in cars is that
they don't tell the driver anything
about the state of the engine. They
have been designed that way so
that they are as unobtrusive as
possible. But even if the engine
management system did provide
This diagram shows the main
components of the Netcomm Racing
Modem System. The system can
cope with more than 60 sensors on
the car.
PC
UHF RADIO
4
SILICON CHIP
feedback to the driver, he would
still want to know more, about the
state of the tyres, brakes, suspension and so on.
If racing drivers had this information about their cars' condition,
they could push them a lot harder.
In the meantime they have to err on
the side of caution if they are to
finish a race.
Overcoming this lack of information has been a joint project between leading data communications
manufacturer Netcomm Pty Ltd and
Peter Brock's BMW racing team.
Netcomm and Brock are in the
process of developing a comprehensive monitoring scheme which will
give real-time information about
virtually every aspect of the car
during a race. Called the Netcomm
Racing Modem System (RMS) it was
first featured in the car driven by
Murray Carter in the 1987 Bathurst
1000. This year it will be featured
in the Mobil BMW car driven by
Brock as well as Murray Carter's
Ford Sierra.
Racing Modem System
As the name suggests, the RMS is
based on modems but there is far
more to it than that. The basic rac-
DATA
.. CAR
COMPUTER
SENSOR
4FHE PIT CRE
Peter Brock in the BMW M3 sedan at Oran Park on Sunday 28th August. Brock won this race. Will the Racing Modem
System give him the edge to win at Bathurst in October? (Paul Buchtmann photo).
ing modem system consists of a
bank of sensors placed around the
car, an on-board computer, a
modem and a UHF (ultra high frequency) transceiver. The computer
converts all the signals from the
sensors into a digital data stream
which is fed via the modem into the
transceiver.
The transmitted information is
picked up at the pits by another
transceiver and modem and fed into
a computer where it is displayed on
a video monitor for constant
analysis by technicians.
As the race progresses, technicians can monitor every aspect of
the car and thereby are able to spot
problems before they become
disasters.
Sensor functions
Just to show how comprehensive
the monitoring is, the various sensors and their functions are listed,
as follows:
• Engine tachometer: measures
engine revolutions up to 9000 RPM.
This is one of the screen displays used on the Apple Macintosh to display car
sensor information. Note the thermometer displays for temperature readouts
and the dial displays for speedometer and tachometer readings.
(Paul Buchtmann photo).
OCTOBER 1988
5
A laptop computer can be used to replay data recorded during a practice or
race session using the Netcomm Racing Modem System. In this way, the driver
can optimise his performance on the track.
This photo shows how the Netcomm modem and UHF transceiver are
installed under the dash of peter Brock's BMW sedan. The modem
transmits at between 2400 and 9600 baud. (Paul Buchtmann photo).
• Speedometer: measures up to
300km/h.
• Backward/forward accelerometer: measures the acceleration
and braking forces on the car and
driver.
• Up/down force: measures the
downward force applied to the car
by the spoilers.
• Left/right accelerometer: measures the cornering forces on the car
and driver.
• Engine oil pressure.
6
SILICON CHIP
• Engine oil temperature.
• Fuel pressure: measures the
pressure of the fuel delivered to the
injection system.
• Fuel temperature: measures
temperature of the fuel to determine if vapourisation is occurring.
• Water temperature: measures
the temperature of the water as it
passes from the engine to the
radiator.
• Detonation: an acoustic sensor
monitors for the onset of this
critical condition. If detonation occurs at racing speeds it can destroy
the engine.
• Exhaust gas: measures the carbon monoxide content of the exhaust gas.
• Exhaust port temperature: each
cylinder exhaust port is measured.
This is another critical engine
parameter. The piston heads are
run at a temperature which is at
times just below melting point.
• Relative horsepower: a figure
obtained from the existing engine
management system on the BMW.
• Battery voltage.
• Battery current.
• Fuel pumps: monitors which
pump is operating.
• Fuel flow: measures the rate of
fuel consumption.
• Gearbox oil pump.
• Gearbox oil temperature.
• Engine bay temperature.
• Differential oil cooler pump.
• Brake temperature: brake discs
will glow red hot when braking at
the end of the straights. If the
calipers become too hot there is a
risk that the brake fluid will boil.
• Brake pedal pressure.
• Brake pad wear.
• Brake lockup: determines if the
wheels lockup under braking.
• Wheel spin: determines if the
rear wheels lose traction under
acceleration.
• Throttle position.
• Cabin temperature: air conditioning is not a feature of racing
sedans.
• Air temperature: measures the
ambient temperature around the
car.
• Humidity: measures the ambient humidity around the car.
• Air pressure: measures the atmospheric pressure.
• Driver temperature: measures
body temperature.
• Driver heart rate.
• Tyre temperature: the temperature of the tread casing of all
four tyres is measured. If it exceeds
a critical level, the tyre will
disintegrate.
• Tyre pressure.
• Shock absorber temperature:
each shock absorber is measured.
If shock absorbers get too hot they
cease to work properly and the
car's handling suffers accordingly.
This photo shows the prototype Netcomm system as used on Murray Carter's Nissan in 1987.
• Vibration: measures vibration
of the car body.
That adds up to more than 45
sensors although we understand
that some of these are not yet on the
car. Tyre pressure monitoring is a
particular problem; just how do you
measure pressure in a spinning
tyre? Netcomm weren't saying.
Tyre temperature, on the other
hand, is measured by infrared
pyrometers spaced a critical
distance away from each tyre. They
have to get the spacing just right.
Too far and sensitivity is degraded;
too close and the oscillating wheel
will rip out the sensor.
Many of the sensor functions are
already provided by the existing
engine management system on the
BMW and its anti-skid braking
system (ABS). But that still left a
great many others which have had
to be installed.
Processing the data
Signals from the sensors are fed
to a data acquisition computer
which can accept up to 66 inputs.
The computer is based on an 8-bit
microprocessor with 32K of ROM
(read only memory) and BK of RAM
(random access memory). The computer prescales the inputs (ie, attenuates or amplifies the signal for
optimum data transmission) and
then performs analog-to-digital
conversion.
The digital data is encoded with
a parity system for error correction
- most important in a telemetry
system of this complexity.
The resulting 8-bit parallel data
is then converted to a serial data
stream to pass via an RS232 port to
the Netcomm modem. The FSK (frequency shift keyed) signal from the
modem is then fed to a transceiver
(a combined transmitter and receiver) transmitting in the 470MHz
band.
The transmitted signal is picked
by another transceiver in the pits
area of the track and the detected
signal fed to another modem to produce an RS232 signal fed to the port
of a Apple Macintosh. This is
specially programmed to display
the information from the car
sensors.
Graphic displays
Rather than just display the information as numerical quantities,
the computer is programmed to
display the information graphically.
Hence, there are displays on the
screen, to depict a speedo,
tachometers, various thermometers
to show the many temperatures be-
ing monitored and so on.
In this way it is easier for the
technicians to monitor any changes
just by glancing at the pointers,
thermometer levels etc rather than
having to pick specific figures off
the screen.
Not only is all the sensor information able to be displayed on the
screen, it is stored in the computer
for later more detailed analysis.
Of course the Racing Modem
System is heavily used in practice
and training sessions. During these
times the drivers can really push
the car to the limits and beyond.
This enables the technicians to
build up comprehensive information about the onset of failure all
the car's systems.
It remains to be seen whether the
Netcomm Racing Modem System
gives Peter Brock and his team the
necessary edge to win at Bathurst.
But one thing is certain - it will be
used on more racing cars in the
future.
•~
Our thanks to Netcomm Australia Pty Ltd and Communications
Solutions Australia Pty Ltd for
their assistance in the preparation of this article.
OCTOBER 1988
7
VINTAGE RADIO
By JOHN HILL
Checking out the power supply
The power supply must be carefully checked out
before switching on a vintage radio. The
components most likely to be at fault are the
electrolytic capacitors, most of which should be
replaced as a matter of course.
Although only a few parts are involved, the power supply is a common source of problems in vintage
radios. It should be carefully checked out before power is applied, as a
fault here can quickly cause
damage to critical components.
Most mains-operated valve
radios have three separate secondary windings on the power
transformer. These secondary
voltages are used as follows: 5 volts
for the rectifier filaments, 6.3 volts
for the heaters in the other valves,
and a high tension (HT) winding
ranging from 285 to 385 volts a side
(equivalent to 570 volts, centretapped).
The 5V and 6.3V AC supplies are
wired straight from the transformer to the filaments and
heaters. However, the high tension
supply must be rectified to give a
high-tension DC supply for the
anodes and screens for the various
receiving and outpuf valves. A
vacuum tube rectifier of the full
wave type (two diodes in the one
envelope, with the cathodes joined
together) is used for this purpose.
Now the figures presented in the
preceding paragraphs work in with
a good many Australian-made sets
from the mid 1930s-1950 era. Fig.1
shows a typical circuit configuration but there are other variations.
For example, some rectifiers require a cathode voltage of 6.3V AC,
not 5V.
Similarly, not all radio valves use
6.3V heater supplies. There are
2.5V valves, 4V valves and 12V
valves in some late model sets. In
these radios, the low tension
voltages on the transformer will be
different - but that's about all.
The high tension voltage will still be
well in excess of 250 volts.
The output from the rectifier
valve will not be pure DC but does
contain some 100Hz hum. The
amount of hum will depend on the
degree of "smoothing" provided by
the following filter network. Whilst
mains hum can be eliminated completely, most radio manufacturers
settled for reducing it to a
reasonable level.
This smoothing of the rectifier
output was accomplished in several
ways. The most common method in
the older valve radios involved
filtering the rectified DC with a
choke and two high-voltage electrolytics, as shown in Fig, 1. Both
the choke and the capacitors help
to smooth out the ripple, which
reduces the intensity of the hum. In
later radio designs, a high-wattage
resistor was often used instead of
the choke.
Electrodynamic speakers
The heart of many an old set's high tension supply - a 5Y3G rectifier valve.
Other common rectifier valves lilcely to be found in vintage radio sets are the
5Y3GT, 280, 80, 5Z3, 5U4G, 6X4, 6X5GT, 83V and the 5V4G.
8
SILICON CHIP
Most radios made up to the late
1940s incorporated the high tension
choke in the loudspeaker, where it
served a dual purpose. As well as
smoothing out the rectified DC, the
current flowing through the choke
Sets from the late 1940s and early 1950s used a chassis mounted choke. Spare
chokes come in handy from time to time.
Many high tension chokes in early
valve sets doubled up as a field coil
in the loudspeaker.
This derelict electrodynamic speaker
shows the field winding to be a large
coil of fine wire.
provided the magnetic field for the
''electrodynamic'' loudspeaker .
This type of loudspeaker was used
before the devolpment of permanent magnet speakers.
Electrodynamic loudspeakers are
not without their problems, but
more about that some other time.
If a radio set has a permanent
magnet speaker, then the choke will
be bolted to the chassis somewhere.
A choke looks like a small
transformer but only has two connections. It is nothing more than a
large coil of wire with an iron core.
An open circuit choke, whether it
be in the field coil of the
loudspeaker or a separate choke
unit, is frequently a problem with a
40 or 50-year old radio. Often the
set has been stored unprotected for
years in an outdoor shed. This can
Fig.1: this power supply
configuration was standard in
many Australian valve radio sets.
Be wary of the rectified HT and
the high-voltage transformer
secondaries - these voltages are
potentially lethal.
CHOKE
'--- -- - --+-...r12·16 +
350VW!
HT
+250V
APPROX
12-16 +
350VW!
promote corrosion where the fine
wire of the choke coil joins the leadout wires, but this is not the only
mishap that can happen to a high
tension choke.
The point is, if the choke becomes
open, that effectively disconnects
the high tension supply to the valves
and a very mute set is the result.
A burnt-out winding is another
common cause of choke failure. I
remember once observing smoke
quietly pouring out of a choke
within a minute or so of switching
the radio on. The set seemed to be
working fairly well, yet the choke
was overheating enough to produce
visible smoke. If prolonged operation under these circumstances is
allowed, the choke will soon burn
out.
The cause of this problem is
usually a faulty capacitor; eg, a
faulty electrolytic on the choke output, or a faulty paper capacitor on
the HT line. As we've seen in a
previous episode, the waxed paper
dielectric that separates the two
layers of foil breaks down and
causes electrical leakage between
the plates of the capacitor. This
breakdown can result in anything
from slight leakage to a complete
short circuit.
The more current through a
leaky capacitor, the greater the
current flow through the choke.
Hence, a choke can be overloaded if
the set has defective capacitors. It
is good practice to replace all paper
and electrolytic capacitors when
restoring old valve radios - particularly those capacitors which
operate with high voltages across
them.
Replacing chokes
It will be fairly easy to replace a
choke that is attached to the
chassis, but the job will be more difficult if the choke forms part of the
loudspeaker. In the latter case, you
will have to replace the loudspeaker as well and that usually
means substituting a modern permanent magnet type unless you
happen to have a suitable spare.
So, before switching an old radio
on, it is a good idea to thoroughly
check out the high tension supply if there's a short somewhere, you
could wreck a perfectly good elecOCT0BER 1988
9
Replacing a power transformer is not difficult if it is clearly marked like the
one in the middle. In other cases, you will have to first identify the primary
winding, then locate the other windings by making voltage checks.
i
~
The speaker field coil can be mounted under the chassis if an old set is
converted to permag (permanent magnet) speaker operation. Make sure that
the choke is properly secured.
trodynamic loudspeaker.
If in doubt, put a milliamp meter
in the choke circuit and find out
what's going on. Most chokes that
are fitted to a 5-valve receiver are
rated at 60 milliamps . Remember, it
is quite normal for a choke or
speaker field coil to become warm
when in use but it is not normal for
it to become hot or to give off
smoke.
By the way, the HT voltage on the
output side of the choke should be
about 250 volts DC and this can be
10
SILICON CHIP
quickly confirmed using a multimeter. If the voltage is higher, it
may be caused by a non-standard
component replacement (eg, a
replacement choke or loudspeaker
of the wrong impedance) and
something should be done to correct
the situation. Adding a resistor to
the high tension line could solve this
problem.
Electrolytic capacitors
Electrolytic capacitors are an important part of the high tension sup-
ply. As previously mentioned, a
shorted electrolytic can soon wreck
the choke or the speaker field coil.
The rectifier valve could also be
damaged due to excessive power
dissipation - the anodes will get
red hot.
Although I recommend that all
electrolytic capacitors be replaced,
this may not be strictly necessary in
all cases. In post-war sets, you may
be able to get away with the
original capacitors. They should be
thoroughly checked though.
A visual inspection is a good starting point when checking electrolytic capacitors. It will be fairly
obvious if the fluid inside the
capacitor has been leaking: the seal
at the positive end of the capacitor
will be cracked or punctured in
some way. Any capacitor that
shows signs of leakage must be
replaced, even if the set still appears to be working OK.
Old electrolytics should also be
checked for electrical leakage and
this can be done using an ohmmeter
set to the tkn scale. When the test
probes are applied, a good electrolytic will initially cause the
meter needle to rise dramatically
(half scale deflection or more), then
fall back to almost zero as the
capacitor reaches full charge. A
reading of several megohms indicates a good electrolytic with
very little leakage.
However, old electrolytics that
have not been in use for many years
often show a much higher reading
on the meter. In many cases, this _
high degree of leakage is only temporary. Putting the capacitor back
into service helps to reform the
aluminium oxide dielectric inside
the capacitor and it often works
normally again.
You can check whether the
capacitor has been reformed by
another leakage check. After the
set has been running for five
minutes, turn it off, let the
capacitor discharge and do another
leakage check. If the leakage is still
high, the capacitor should be
replaced.
A final check for an old electrolytic is a capacitance test. Many
digital multimeters have a capacitance function up to 20µF or
thereabouts. Be warned though;
without the correct polarising
voltage, the measured capacitance
will only be a guide. Remember also
that old electrolytic capacitor
tolerances were very wide (typically + 100% to - 50%}.
It is a good idea to always
discharge the electrolytic capacitors before working on a set.
However, don't do this by directly
shorting the capacitor terminals
with a screwdriver blade or similar
instrument. Discharging a capacitor in this manner can cause internal damage due to the high
discharge current involved.
A far better method is to use a
lOkO resistor fitted with a couple of
probes. This will limit the current to
a safe value.
The rectifier valve
The rectifier valve itself must not
be overlooked in this discussion on
high tension. A rectifier may light
up OK but that doesn't mean that it
will work properly.
Filament type rectifiers have
specially coated filaments that give
off high electron emission at
relatively low temperatures (red
heat). This coating is easily seen by
looking into the glass envelope of
the valve. Such a visual inspection
is a reasonable way to determine
the general condition of the rectifier, excluding short circuits and
other nasties.
If the filament is white, the
coating is intact. If the filament is
bare and metallic looking, then the
coating has either burnt off or has
fallen off. In some cases, the filament coating can be seen in bits
and pieces drifting around inside
the glass envelope.
What the foregoing really means
is this: if the filament is bare, the
electron emission will fall to such a
low level that the rectifier will not
pass sufficient current for the set to
operate correctly. In many cases,
low volume in a valve receiver is
the result of abnormally low hightension voltage due to a worn-out
rectifier valve. Simply replacing the
rectifier will boost the volume
considerably.
Much the same can be said about
rectifiers with indirectly heated
cathodes. The cathode is coated
and, if this coating has cracked or
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OCT0BER1988
11
There are many high voltage connections underneath the chassis. Don't take
unnecessary risks when working on the high tension supply, as the voltages
are potentially lethal.
Old electrolytic capacitors can cause serious problems in the high tension
department. Their replacement is always a good move.
worn away, the performance of the
valve is suspect.
Naturally, a valve tester can
save a bit of guesswork in this
regard. However, a good many
restorers work without such an instrument and a visual inspection
followed by an in-circuit check will
do the job just as well.
Power transformers
Power transformers in old radios
are usually very reliable. However,
they do break down occasionally
and the usual problem is a burnt
out primary winding.
If the primary or any of the other
windings has broken down, the only
12
SILICON CHIP
solution is to replace the
transformer. This is another situation where it pays to have a good
supply of spare parts. Radio wrecking is a very important aspect of
vintage radio work and every
restorer should have a good range
of power transformers on hand to
cope with emergencies.
Changing a transformer over is a
fairly simple job if the connections
are clearly marked. However, in
many cases, there is nothing more
than a bunch of multi-coloured
wires emerging from the transformer. This means that a bit of circuit tracing is required to identify
the leads. This can be done by trac-
ing the leads back to the 240 volt
AC line, the rectifier filament (5
volts), the rectifier anodes (285
volts) and the valve heaters (6.3
volts).
The connections on the replacement transformer may also need
sorting out. The primary leads are
usually the leads closest to the core.
Once these have been identified,
the unit can be temporarily connected to the mains and the remaining windings identified using a
voltmeter. Note that, in most cases,
the high-voltage secondary winding
will be centre-tapped.
Take great care when making
these measurements. Both the
mains and HT secondary voltages
are dangerous and getting tangled
up with them could well be the last
thing you do on this earth.
In fact, it's a good idea to terminate all leads from the transfomer in a terminal block before applying power. It should only be installed in the chassis after the leads
have all been identified.
Another way of identifying
transformer leads is to apply an AC
test voltage to one of the lowvoltage' secondary windings (either
the 5V winding or the 6.3V winding). The leads to these windings
use stout single-strand copper wire,
so they're easy to identify. All you
have to do is to apply the test
voltage (say 6.3V AC) to one pair of
leads that have the same colour
code, then identify the remaining
leads using a multimeter.
It doesn't matter which lowvoltage secondary winding you feed
the test voltage into. If you guess
correctly and feed a 6.3V test
voltage into the 6.3V winding, then
all the other voltages will be correct. But if you pick the 5V winding,
all the other voltages will be high by
a factor of about 1.26 (ie, 6.3 + 5).
If you use a test voltage other
than 6.3V AC, the expected output
voltages will be scaled accordingly.
Finally, always remember to
disconnect the power supply and
discharge the electrolytics before
working on the set. If you follow this
simple safety routine you will live to
enjoy your hobby for some time to
come.
Next month's vintage radio topic
will be on loudspeakers.
~
The Mini-mitter is a miniature stereo FM
transmitter using just one integrated circuit and
powered by one 1.5V penlite cell. You can connect
your CD player to the Mini-mitter and then listen to
your favourite CDs anywhere in the house, via
your Walkman personal portable.
By JOHN CLARKE & LEO SIMPSON
How would you like to listen to
your favourite CDs and records via
headphones without being tethered
to your stereo system? Maybe you
want to wash the car, mow the
lawn or vacuum your house while
you listen to your favourite music.
Clearly, a Walkman-style cassette
player will let you listen via headphones while you work but who
wants to go to the trouble of dubbing a record to tape every time the
mood hits you.
Or maybe you have a portable CD
player and you'd like to listen to
CDs via your car radio. Most car
radios do not have connections for
an external program source so that
14
SILICON CHIP
can be a real problem.
If you have these problems, the
Mini-mitter is the answer. You can
connect it up to your stereo system
and broadcast your own stereo
music program on the FM band; ie,
88-108MHz. The Mini-mitter puts
out a flea-power signal (around 200
microwatts or so) but that is enough
to give clean stereo sound over the
average portable FM radio within a
range of 20 metres or so.
You can use it in your car with a
portable CD player, to avoid making
any connections to your car radio.
Just connect the CD player up to the
Mini-mitter and tune in your car
radio to the correct frequency to
hear the program of your choice.
The Mini-mitter is built into a
small case and powered from just a
single 1.5V AA size cell. Two RCA
sockets are provided at one end of
the case for the left and right audio
channels. At the other end, there is
a length of wire which is the
transmitting antenna and there is a
slide switch to turn the Mini-mitter
on or off.
Inside the case, there are a couple of trimpots to adjust the level of
the left and right channel audio
signals. These are important to obtain minimum audio distortion,
especially when listening to compact discs.
There are also internal adjustments to vary the transmitter
frequency anywhere within the 88
to 108MHz FM band. We'll talk
about these later.
As you can see from the specs,
battery cost will not be a problem.
A normal penlite cell should last for
many months even if you use it for
several hours every day.
A single IC provides all the
.......,,s
____*___*_________
.01
.01
'T'l41-t-pF__..._L2..,
i
.001
18
F
OUT
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LEFT IN
47pF
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IC1
BA1404
RIGHT
INPUT
~
1.5V
VR3 50k
LEFT
INPUT
er
t.J
ANTENNA
DSC lO
*
*
15pF
osc=----41
1 RIGHT IN
MPX
OUT
14
PILOT
OUT
13
10
+ JJOpF
16VW _ STYRO
...
4.7pFJ
'
AUDIO
BIAS
2
MOO
IN
12
10
DSC AUDIO RF
BIAS GNO
4
3
8
+
.,.
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15pFI 2·10pF
-:-
FREQUENCY
TRIM
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16VWJ .OOl+
L1 ,L2: 1.5T, 0.62mm DIA. ENAMELLED COPPER
WIRE ON 5mm FORMER WITH F16 CORE
.D1'i
* CERAMIC
FM STEREO TRANSMITTER
Fig.1: the key component in the circuit is the BA1404 FM stereo transmitter IC from Rohm Corporation.
This chip includes a 36kHz multiplexer plus all the necessary input amplifiers, mixers and oscillators
required for FM stereo transmission.
Specifications
Operating voltage ... ..... .... ..... .. ....... ... .... .. ..... ...... .... .......... ... 1.5V
Quiescent current ... ... ... .. .. .... .... .. .. ... .. .. .. ..... .. ..... ... .... ......... . 3mA
Harmonic distortion ..... .. ........ .. .. ..... .. ...... .. . 3% for 200mVp-p input
Stereo separation ........... ..... ......... .. .. ... ...... ... ... ... .... 45dB at 1 kHz
Frequency range ..... ........ ... .. ... .. ....... ... ......... .. 88 .1 to 107.9MHz
necessary functions for FM stereo
transmission. This includes input
amplifiers. 38kHz multiplexer. mixers and oscillators. Naturally there
are a number of passive external
components but the resulting circuit is very compact.
How it works
Fig.1 shows the complete circuit
of the Mini-mitter. It is based on a
BA1404 integrated circuit made by
the Rohm Corporation of Japan. The
circuit works as follows.
The left and right audio signals
from the program source (CD
player, tape player etc) are connected to trimpots VRl and VR2 to
set the input signal levels. These
are coupled via a parallel network
of a 47k0 resistor and .OOlµF
capacitor to provide the standard
50µs pre-emphasis applied to
Australian FM signals.
Put simply, pre-emphasis is a
defined amount of treble boost applied to the signal before it goes into
the transmitter. Then, when the
signal is received and demodulated,
an equivalent inverse order of treble cut, called de-emphasis, is applied before the audio signal is fed
to the tuner outputs. The result is
an improvement in the high frequency signal-to-noise ratio, which
means a reduction in audible hiss.
The pre-emphasised audio signals are then coupled via a series
4.7µF capacitor and 100 resistor to
the left and right inputs of the IC,
pins 18 and 1, respectively. The 100
resistor is there as a " stopper" to
prevent latch-up due to RF signals
on the input leads. The internal bias
supply for the audio input
amplifiers is filtered by a lOµF
capacitor connected to pin 2.
To provide the 38kHz multiplex
oscillator, a miniature 38kHz
crystal (same physical size as a
32kHz watch crystal) is coupled via
a lOpF capacitor between pins 5
and 6. The oscillator's bias supply
is decoupled by a l OOOpF (.OOlµF)
capacitor connected to pin 4. To
provide a balance setting for the
multiplexer, VR3 , a 50k0 trimpot,
connects between pins 16 and 17 of
the IC.
The multiplexer output from pin
14 and the 19kHz pilot signal at pin
13 are mixed using series resistors
and capacitors to set the correct
phase and level to the modulation
input at pin 12.
The modulator oscillator tuned
circuit components are those connected to pins 9 and 10; ie, L1 and
associated capacitors. Cl , a 2-lOpF
trimmer capacitor, provides fine
O CT0 BER 1988
15
The completed assembly mounts inside a small plastic case to give a really
compact assembly. The small trimmer capacitor (at end of pen) allows fine
tuning of the transmitter output frequency.
Fig.2: here's how to mount the parts on the PCB. Keep all leads as
short as possible and note that some of the parts are mounted endon to save space. The coil formers for Lt and L2 are installed from
the underside of the PCB.
adjustment for the oscillator
frequency.
Inductor 12 and a 47pF capacitor
at pin 7 form the tank circuit [ie, a
parallel tuned circuit) for the RF
amplifier. The output signal to the
antenna is coupled via a 4. 7pF
capacitor.
One of two antennas may be used. If the transmission path is very
short, you will find that a single
wire 15cm long will suffice. For a
more effective transmission, a simple dipole can be used, as described
later.
Construction
The Mini-mitter circuit is built
onto a small printed board (coded
SC06-1-1088-1) measuring 4 7 x
16
SILICON CHIP
60mm. The board is housed within
a plastic case measuring 83 x 54 x
28mm. A Scotchcal label can be attached to the lid of the case to indicate the controls.
Start construction by checking
that the PCB will neatly fit into the
case so that it is supported on the
stops of the PC guides. The stops
are provided for mounting a printed
board horizontally, as we have
done, but they need to be lowered
by a bout 4mm, to give sufficient
clearance for the battery and its
holder. You can achieve this by
judiciously cutting away the guides
with a pair of side cutters.
If the PCB is too wide it can be filed down to size until it fits neatly
into the case.
The PCB requires two 5mm holes
for the coil formers for 11 and 12.
These formers are installed from
the underside of the PCB and are
glued in position [using nail polish
or 5-minute epoxy).
You can now insert and solder
the IC as shown on the overlay
diagram [Fig.2). The 1.5-turn coils
can then be wound onto each
former. These are wound by first
stripping the enamel from one end
of the wire and soldering it in place.
Wind on 1.5 turns and insert the
free end of the wire into the PCB.
Cut it to length, strip off the enamel
insulation and solder. Both coils are
wound in the same way.
Once the coils have been wound,
the remaining parts can be installed as shown in Fig.2 . All the
resistors are installed end-on [ie,
vertically) and so is the 330pF
polystyrene capacitor. Ensure that
the four electrolytic capacitors are
oriented for correct polarity.
If you can't obtain a single AAcell holder you can make one by
cutting down a dual AA-cell holder.
The holder is cut in half longitudinally to provide a single holder.
The spring in the negative end is
soldered into the PCB while the
positive end is connected to the PCB
using a stiff piece of copper wire
looped over and soldered to the clip
socket.
Once the PCB is complete, install
it in the case and mark out positions
for screwdriver access holes for
the trimpots, VRl and VR2. You
should also mark out holes for the
panel RCA sockets and switch. The
switch is mounted very close to the
base of the case so that it does not
foul the PCB.
Drill holes for the sockets and
trimpot level adjustment holes. The
switch is mounted using small selftapping screws into the mounting
flanges. The frequency adjust hole
in the lid is found after attaching
the label artwork to the lid and
drilling at the hole position
provided.
Now wire up the switch, RCA
sockets and antenna. The antenna
can be a simple dipole [ie, an indoor
FM antenna) or a single length of
wire [about 15cm would be
suitable) connected to the antenna
terminal. For a dipole, the second
How an FM Stereo Transmitter Works
Fig.3 shows the block diagram
of a stereo transmitter as typified
by the Mini-mitter. The left and
right channel inputs are applied to
trimpots and then to 50µs preemphasis circuits (to provide treble boost above 3kHz, to the
Australian FM standard).
After pre-emphasis, the left and
right signals are fed to buffer
amplifiers and then to the
multiplexer which is driven at
38kHz. This produces a sum (L +
R) signal and a difference (L - R)
signal which is amplitude modulated on a 38kHz carrier. The
carrier is suppressed to provide a
double sideband suppressed carrier signal.
The (L + R) and (L - R) signals
are mixed with the 1 9kHz pilot
signal which is derived by dividing
down the 38kHz oscillator signal
by two. The resulting composite
signal is then frequency modulated
onto a carrier frequency in the FM
band. Once filtered and amplified
in the RF amplifier, the signal is
transmitted via the antenna.
Fig.4 shows the spectrum of the
composite stereo signal. The L +
R signal occupies the frequency
range between O and 1 5kHz. The
double sideband suppressed car-
ANTENNA
(L +R)+(L-R)coswst +Kcoswpt
MULTIPLEXER
PILOT
MIXER
.,.
RF MIXER
OSCILLATOR
Fig.3: block diagram of an FM stereo transmitter, as used in this project.
The accompanying text explains how it all works.
LEVEL
L+R
L-R
0
15 19 23
PILOT
L-R
38
53
FREQUENCY
(kHz)
Fig.4: frequency spectrum of the composite transmitted
stereo signal. Note the pilot tone at 19kHz.
rier signal (L - R) has a lower sideband which extends from
23-38kHz and an upper sideband
from 38-53kHz. There is no subcarrier at 38kHz.
The pilot carrier at 1 9kHz is also
shown. The pilot tone is used by
the receiver to reconstitute the
38kHz subcarrier so that the
stereo signal can be decoded .
connection goes to the earth track
adjacent to this antenna terminal
and is soldered to the underside of
the PCB.
You can buy a ready made dipole
antenna from Jaycar (Cat. 1 T-3002)
or Arista outlets (Cat. FMAl).
VR3 should initially be set to the
centre position. Now insert a 1.5V
AA cell into the battery holder and
check that there is 1.5V across pins
3 and 15 with a multimeter.
Initial checks
Operation can initially be checked with an FM tuner set to an unused frequency near the centre of the
band. Insert slugs into 11 and 12
and adjust both so that each slug is
about 2mm below the top of the
former. Now adjust the 11 slug until
the tuner receives the signal. This
can be detected by the level and/or
This close-up view clearly shows the winding details for L1 and L2. The PCB
clips into guides running down each side of the plastic case (see text).
OCT0BER1988
17
..I
L
+
ff!il~
SC 06-1-1088-1
+
ffl!HIHs
LEFT RIGHT
FREO.e
ADJ.
LEVEL LEFT
~~
ON
OFF
LEVEL RIGHT
.,
+
STEREO FM
TRANSMITTER
i
1~1~
+
r
Fig.5: actual-size artwork for the front panel.
Fig.6: actual size PCB artwork.
PARTS LIST
1 PCB, code SC06-1-1 088-1 ,
47 x 60mm
1 plastic case with plastic lid,
83 x 54 x 28mm
2 RCA chassis mounting
sockets
1 AA cell holder
1 1.5V AA battery
1 sub-miniature slider switch
2 Neosid 722/1 5mm coil
formers
2 Neosid F1 6 4mm ferrite
cores to suit formers
1 38kHz miniature crystal
1 BA 1 404 Rohm FM stereo
transmitter IC
1 1 00mm-length of 0.63mm
enamelled copper wire
Capacitors
The two small holes in the end of the case allow screwdriver access to the
level adjustment trimpots, VR1 and VR2. A third hole in the lid of the case
provides access to trimmer capacitor Cl for frequency adjustments.
tuning meter on the FM tuner
and/or by a stereo light indication.
The L2 slug is then adjusted for
maximum signal.
To set the transmitter on other
parts of the band, the slugs must be
low down into the coils for the low
frequency end of the band and conversely, higher for the high end of
the band. Note that both slugs
should be set in similar positions in
the former for best results. The
coils are slightly interactive so that
adjusting one will affect the other.
For fine tuning, use the trimmer
Cl. The slugs can be secured in
position using a very small amount
of candle wax. Alternatively, some
18
SILICON CHIP
dental floss inserted into the former
before the slug will help stop
movement.
To adjust the input level trimpots,
connect a program signal to the
RCA sockets and listen to the output
from the tuner, preferably via headphones. Adjust the trimpots so that
distortion is not present on loud
signals. This is easy to do because
when the distortion is present it
sounds awful.
If you have an AC millivoltmeter
and sine wave oscillator you can
also set trimpot VR3 for maximum
separaiion between channels. If
not, just leave VR3 centred as this
will be close to the optimum setting.
2
2
3
1
3
1
2
2
1
2
1
1 0µF 16VW PC electrolytic
4 . 7 µF 16VW PC electrolytic
.01 µF miniature ceramic
.0 1µF metallised polyester
.001 µF metallised polyester
330pF polystyrene
4 7pF miniature ceramic
1 5pF miniature ceramic
1 0pF miniature ceramic
4. ?pF miniature ceramic
2-1 0pF trimmer capacitor
(Philips 2222 808 11109)
Resistors (0.25W, 5%)
1 x 1 00kD, 2 x 47kD, 1 x 2. 7kD,
2 x 1 on, 1 x 50kD miniature vertical trimpot, 2 x 1 0kD miniature
vertical trimpots
Miscellaneous
Small self-tapping screws,
hookup wire, tinned copper wire.
<at>HITACHI
20MHz/lmV
$830
ExSa!esTax
$996 me tax
m···
Wouldn't you pay a bit more for
features like this?
So good we give the full Spee!
Display
CRT
Graticule
Quality Hitachi engineering
O Two year Warranty
o Includes two quality Hitachi probes
o Tough all metal case and front panel
Ideal for servicemen - small footprint and
light weight (31Ox37cJx130mm 6kg)
o Extensive triggering facilities including TV
sync and vertical mode for steady traces
when input frequencies differ widely
o Free 55 page operating manual with
circuit diagram
o
Poteritial
External Intensity
Modulation
Vertical Deflection
Sensitivity
Bandwidth
MAX. Input Voltage
Input Coupling
Input Impedance
Display Mode
CHl Vertical
Signal Output
X-Y Operation
Sensitivity
Bandwidth
Phase Difference
Horizorital Deflection
Sweep Time Range
Trigger
Trigger Mode
Trigger Source
Trigger Sensitivity
Order now. Call
Sydney
(02) 648 5455 32 Parramatta Rd, Lidcombe 2141
Fax (02)6471545 TelexAA24949 P.O.Box14Lidcombe2141
Melbourne (03) 480 0111 72-74 Chifley Drive, Preston 3072
Adelaide (08) 354 0588 Brisbane (07) 277 4422
Perth (09) 325 9333
I BB.L ]
Bell Test &
Measurement
The measure of quality
A Division of Bell-lRH Ltd (inc in N.S.W.)
Prices subject to change without notice
Internal , 8 x 10 div (1 div = 1 cm) , Horizontal and
vertica l center lines further marked in 0.2 div
increments, mark ing for measurement of rise tl me
Accelerating
Rise Time
o
6-inch recta ngular.
Trigger Coupling
Trigger Slope
Calibrator
Power Supply
Ambient Temperature
Dimensions
Weight
MTBF
Accessories Supplied
2 kV.
Voltage : 5V o r more.
Effect ive bandwidth : DC to 2 MHz.
Max . inpu t voltage: 30V (DC+ AC peak}.
5m V/di v to 5V/d iv in 10 calibrated steps ± 3%.
lmV/d iv, 2m V/d iv ± 5% when using
x 5 magnifier.
Uncalibra ted co nt inuous co ntrol between steps
1 : < 2 .5.
DC t o 20 MHz 1-3 dB).
DC to 7 MHz (- 3 dB) when using x5 magnifier.
17.5 ns.
50 ns when using x 5 magnifier .
300V {DC+ AC peak) or 500Vp-p AC at 1 kHz
AC,GND, DC.
1MS1 approx . 25 pF.
CH1, CH2 {n ormal o r invert), ALT. CHOP, ADD
Voltage : appro x . 20mV / div in t o 50!1
Bandwidth: 50 Hz t o 5 MH z (-3 dB) i nto 50!1.
CH1 : X-axi s. CH2 : Y-a xis.
5mV/ div to 5V /div.
1mV/div, 2mV /di v w hen using x 5 magnifier.
DC t o 500 kHz 1-3 dB ).
3° or less from DC to 50 kHz .
0.2 µs/ div t o 0 .2s/d iv in f9 ca librated steps e 3%.
100 ns ±5% w hen using x10 magnifier
(20 ns and 50 ns uncafib rated) .
Uncalibrated con ti nuous co ntrol between steps
1 : < 2.5.
Automatic {sweep runs in absence of a triggering
signa l and for signa l below 30 Hz), Normal {sweep
runs when triggered ), TV' V. TV-H.
CH1, CH2, V -MODE, External, Line.
20 Hz to 2MHz 12 MHz to
20MHz
I CH 1 and CH 2 i
0 .5 di v
I 1.5 div I
20mV
I E.x ternal
I
I BOOmV I
AC.
+ or Square w ave. Vo ltage : 0 .5V ± 3%.
Frequency: A pprox. 1kHz
V olt age
: 100/ 120/220/240 V ± 10%.
Frequency : 50/60 / 400 Hz.
Power consumpti on : approx . 30 W.
Rated range o f use : +10 to 35° C.
Limits of operation : 0 to 50° C.
Storage and transport : - 20 to 70°C.
310(W) x 130IH) x 370(D) mm.
12.2 X 5. 1 X 14.6 in.
Approx. 6 kg/ 13.2 lb.
20 ,000 hours for target value.
Two AT-1 0AJ 1.5 p ro bes, Fuse , Power cable ,
I
i
Operation manua l.
I
HIFI REVIEW
YAMAHXS BRILLIANT
COMPACT DISC PLAYER
You've heard of 2-times oversampling and 4-times
oversampling in CD players. Now there is 8-times
oversampling, as featured in Yamaha's top of the
range CD player, the CDX-1110. It provides
unrivalled linearity and a brilliant signal-to-noise
ratio as we found when putting the CDX-1110
through its paces.
By LEO SIMPSON
When CD players were first introduced five or so years ago, the
available 16-bit digital-to-analog
converters were pushing the very
limits of VLSI (very large scale integration) technology. Linearity
was a real problem, especially at
signal levels below - 60dB with
respect to the maximum output
level of 2V RMS. So much so, that
one of the biggest players, Philips,
elected to use a technique called
"oversampling" which enabled
them to use 14-bit D-A decoders.
Philips claimed (and reviewers
confirmed) that this technique gave
results as good or better than
available 16-bit decoders. Philips
also opted to use dual D-A decoders
20
SILICON CHIP
and thereby was able to claim an
advantage of no phase delay between channels at the higher frequencies. There was a further advantage in that the filtering required to remove the sampling
artefacts was less severe.
That was then. In the intervening
years, many manufacturers have
used the oversampling technique to
improve on the performance
available from 16-bit decoders.
Yamaha has used 2-times oversampling at 88.ZkHz while more
recently they and some other
manufacturers have employed
4-times oversampling, at 176.4kHz.
Now Yamaha have leapfrogged all
the rest by introducing their 8-bit
oversampling machines which run
at 352.BkHz.
Why so high? We're not going to
delve into all the technical background because it would make this
article too long but there are three
reasons to increase the sampling
rate to 352.BkHz. First, improved
linearity; second, better signal-tonoise ratio; and third, very low
sampling artefacts in the audio output of the player. There are a
number of other technical advantages but as far the user is concerned, those listed are the important
ones.
As spectacular an advance as
the jump to 8-times oversampling
may seem, that is not the whole
story as far as this new CD player
from Yamaha is concerned. It also
offers 18-bit D-A conversion and
digital control of the output level.
What's that you say? How can a
16-bit CD player have an 18-bit
decoder? We'll come to that later.
Presentation
The styling and presentation of
the latest CD player from Yamaha
is very much in the mould of
16-BIT NO OVERSAMPLING
/
"
\
V
SIGNAL
I
DIA
\
CONVE RTER
OU TPUT
I
WAVEFORM
AFTER
DIA CONVERSION
'-ERROR WAVEFORM
OF ABOVE SIGNAL
(DISTORTION)
HI-BIT 8 TIMES OVERSAMPLING AT 352 .8 kHz
SIGNAL
WAVEFORM
AFTER
DIA CONVERSION
DIA
CONVERTER
OUTPUT
ERROR WAVEFORM
OF ABOVE SIG NAL
Fig.1: these photos and diagrams show the difference between normal
16-bit sampling at 44.lkHz and 8-times oversampling at 352.BkHz. Notice
that the steps in the re-constituted audio waveform are much smaller
and sampling artefacts to be filtered out are greatly reduced.
Manufacturer's Specifications
Audio section
Frequency response ....... ... .. ....... .... .. 2Hz to 20kHz within ±0.3dB
Total harmonic distortion .. .. .......... .. ...................... less than .002%
Signal-to-noise ratio ... ... .. ... ...... ... ... ... .... .... ... ............... ..... 118dB
Dynamic range ....... ... .... ............ ..... ...... .. .... ...... more than 1 00dB
Wow & flutter .. ... ... ......... .... .... .. .... .. .. .. ..... .. ........ .. . unmeasureable
Channel separation .... .... ... ...... ..... more than 1 00dB (1 kHz , 20kHz)
Maximum output voltage .. .. ... ......... ... .. .. .. .... .... .. .. ... .. .. 2 volts RMS
Output impedance ...... ... ... ..... ..... .... .. ....... ........ ... ... ... .... . 4 7 ohms
Headphone output .... .. ........ .............................. 3 volts/150 ohms
Internal system
Optical pick-up .. ..... .......... ......... .... .......... ... ..... .. .... .. 3-beam laser
Error correction system ........................ ..... ............ .. .. .. .. .. ... CIRC
Digital-to-analog conversion ... ...... ....... ....... .... .. .. twin 1 8 -bit floating
Filtering ..... ... .. .... .. ........ .. .... : .... . hi-bit digital & 3rd order active filter
I
!
Volume control
General
Dimensions ...... ...... .. ...... ... ......... .. ............ 435 x 120.5 x 418mm
Power consumption .... ....... .. .... ........ ................. ...... ....... 30 watts
Weight .... .... ... .. ... ....... ... .... ........ ..... ... ......... ....... ... ........ . 14.2kg
previous models although it is
notably larger and heavier. In fact,
it is currently one of the largest and
heaviest CD players available.
It is made to look even larger by
its massive feet although they are
not quite as noticeable as they appear in our photograph. As can be
seen, the CDX-1110 offers comprehensive facilities although, for
remote control, you can directly
select any of the first 24 tracks of a
disc. For tracks above 24, you first
hit the 10 + button twice (or more)
and then a button between 1 and 9.
(some test discs have over 50
tracks).
If you've listened to a disc many
times and know it well, you can
"freshen" it up by listening in "random play" mode. Three repeat
modes are also available. You can
repeat a single track, the whole
disc or a track excerpt, as marked
by two pushes of the A - B button.
The latter repeat mode is very fast,
with almost no gap between the end
and start of the repeated passage.
This can be handy for music
students or when testing loudspeakers.
If you ' re taping a CD, the
CDX-1110 will insert a 3-second
gap between tracks. This makes it
easier for the tape player to subsequently find particular tracks (in
those machines with automatic
music selection). You can also program the order of play, up to 24
tracks.
And how many of you have CDs
on which there is a track you really
hate? The CDX-1110 copes with
that. By using the Delete button you
can program it to leave out the
track or tracks which are "on the
nose".
So much for the play facilities.
Most users will probably not use
the controls on the machine but use
those on the remote instead. It's
much easier and you don't need
20:20 vision to see the control
labelling.
the most part, these are in line with
those offered on previous Yamaha
models.
We'll just touch on the highlights
of the playing facilities, all of which
are also available on the infrared
remote control. As can be seen from
the photo, you can directly select
any of the first ten tracks via buttons on the front panel. On the
The Yamaha CDX-1110 is one of
the few machines on the market
with full volume control via the
remote handpiece. It's a beauty.
Yamaha make the point that the
digital volume control is more
precise, offers better tracking between channels and lower noise but
I just like it for the convenience. It
increases (or decreases) the signal
level in 0.4dB steps and has a total
range of more than 70dB.
The remote control has no less
than 44 buttons but it is still quite
easy to use although it would be
better with a bigger "Play" button.
OCT0BER1988
21
18-bit conversion
Inside the Yamaha CDX-1110: note the two transformers in the power supply
and the large player mechanism which has a locking lever for safe transport.
The same could be said of the buttons on the machine itself; the Play
button needs to be made bigger or
more obvious so that you don't have
to peer at the front panel to find it.
Output facilities
On the rear panel, the CDX-1110
has two pairs of RCA outputs, both
of which are variable in level via
the digital volume control. One set
of outputs is labelled "direct" while
the other is "filtered". The difference between the two is that the
latter has an analog low pass filter
to remove digital sampling artefacts (that is, noise at the sampling
frequency).
Yamaha state that they have pro_vided the choice of two outputs
because some people prefer the
"softer" sound of the filtered output while, on the other hand, the
direct outputs have the advantage
of minimum phase error.
In addition to these analog stereo
outputs, the CDX-1110 has two
digital outputs, for ultimate connection to a separate D-A converter,
should a better unit be available in
the future (perish the thought). One
22
SILICON CHIP
of these outputs is via a conventiomi.l RCA phono connector while
the other is via an optical fibre connector, for true isolation.
The mains supply connection is
via a sheathed two-core flex with
moulded two-pin plug. The unit is
double-insulated.
Interior details
Removing the lid of the CDX-1110
reveals a very busy interior with
lots of interconnecting wiring between the various printed boards.
The power supply is unusual in a
couple of respects. It has two power
transformers, both quaintly labelled "massive power supply" . The
other point is that the supply
employs shunt regulators instead of
the more usual series regulators.
Yamaha state that this is because the shunt regulators have
a lower output impedance than
series regulators, particularly at
high frequencies. The implication
we draw from this is that the shunt
regulators are better at suppressing digital "hash" and therefore
result in a better signal-to-noise
ratio.
Having covered the key features
of the CDX-1110, we still have yet to
explain how the unit manages to
employ an 18-bit D-A converter instead of a 16-bit converter, oversampling or not. In reality, Yamaha
has combined an 18-bit digital filter
(which performs the 8-times oversampling) in conjunction with two
16-bit D-A converters, one for each
audio channel. Yamaha has taken
advantage of the fact that the two
most significant bits from the 18-bit
filter are only present during the
loudest parts of the program signal.
Normally then, the top 16-bits of the
18-bit signal are fed direct to the
two 16-bit D-A converters.
When one or both of the two most
significant bits is not present,
operation is shifted to accommodate the two least significant
bits while the gain of the associated
audio amplifier is changed by a factor of 0.25 to compensate for the
change in signal level. The result is
a much improved signal to noise
ratio.
This clever scheme is shown in
Fig.2. We can vouch for the fact
that it works - the CDX-1110 has a
phenomenal signal-to-noise ratio. It
also has improved linearity at very
low signal levels.
Interestingly, the way in which
the 18-bits from the digital filter are
manipulated to make them compatible with the 16-bit D-A converters is
not the end of the story. Yamaha
use the same technique to provide
the remote volume control referred
to earlier. To change the signal
level, the signal is varied in level
while it is still in digital form, by
manipulating the bit levels. Very
tricky.
On test
In use, the CDX-1110 is great.
The transport mechanism works
very smoothly and quitely. And it
has the fastest access times we
have yet to come across. Switching
from track 1 to track 25 on a
25-track disc takes less than two
seconds. That's really fast.
Sound quality was absolutely
tops, from either the Direct or
Filtered audio outputs. The difference is very small although it is
discernible to the keen-eared
Th e top 16 bits are sent directly
to the DIA converter
DIA converter drops operat,on level by up to
two bits to accommodate digital filter output
j
j
:
114
L______ ___ J
l
Output
Gain lowered by 114
High Level Signal
Low Level Signal
Fig.2: these diagrams show how the 18-bit parallel signal from the
oversampling filter is switched to the 16-bit D-A converters (only
one shown). When the lower 16 bits are switched to the converter,
the output amplifier gain is reduced to compensate for the shifted
operation.
listener - but only when switching
directly between the two.
On the test bench, the CDX-1110
really shines. Paradoxically, it
presented us with less problems in
confirming its specifications than
many other CD machines we have
tested. The reason is that the digital
sampling artefacts are so high in
frequency that the normal 20Hz to
20kHz bandpass filter of our AC
millivoltmeter ignored them. As a
matter of interest, the 352.8kHz
residual signal is - 60dB with
reading being .005% at 20kHz in
one channel.
Verifying figures for channel
separation was no problem .
Yamaha specify - lO0dB. We
achieved around - 103dB or better
over the whole frequency range.
Signal-to-noise ratio
Signal-to-noise ratio is the big
one. Yamaha specify this at a stunning - 118dB. Six months ago there
was no way we could verify this,
respect to full output.
Yamaha quote the frequency
response as being flat from
2Hz-20kHz within ± 0.3dB. None of
our test discs go below 20Hz but
within the range 20Hz to 20kHz we
were able to confirm that the
Yamaha's unfiltered outputs were
considerably better than ± 0.3dB.
In fact, the response was only
.03dB down at 20kHz.
The filtered outputs were not
quite so precise but well within
Yamaha's spec of ± 0.3dB.
Yamaha's spec for harmonic
distortion is a little vague, a figure
of .002 % being quoted, with no
reference frequency. Our measurements yielded figures very close to
or equal to .002 % for most of the
frequency range, with the highest
All functions of the CDX-1110 player
can be selected by the infrared
remote control.
with available test equipment, commercial or otherwise. Now we can,
with our own AC Millivoltmeter.
For unweighted measurements
(band limited from 20Hz to 20kHz)
on the unfiltered outputs, we
measured -114dB and - 117dB
for the two channels. For "A"
weighted measurements, these
figures improved to - 116dB and
- 118dB respectively.
Strangely, the figures were not
quite as good for the filtered outputs: - 11 ldB and - 113dB
unweighted, and - 113dB and
-115dB "A" weighted. That slight
degradation may be due to the op
amps in the analog filter stages.
For those who have just read
those figures and find them a little
meaningless, let's put them in
perspective. That figure of - 118dB
with respect to the 2 volt RMS
reference signal represents a noise
signal of just 2.5 microvolts (2.5
millionths of a volt)! That makes the
Yamaha CDX-1110 the quietest
piece of audio equipment available,
that we know of. Unbelievable.
Linearity is another key test of
the Yamaha 18-bit technology. If it
doesn't come through here, it isn't
worth doing. Well it does. On the
linearity test tracks of the Technics
CD-001 test disc, we measured an
error of - 0.4dB at the - 80dB
level. At the - 90dB level, we
measured errors of between - ldB
and - 1.2dB, depending on whether
direct or filtered outputs were connected. These results are easily the
best we have ever measured.
No problems with tracking tests
were encountered as far as the test
disc was concerned. Nor did we expect any.
Well, how would you sum up the
Yamaha CDX-1110? Clearly, the objective measurements show it to be
one of the best machines available
today, regardless of price. And subjectively, it's right up there among
the top machines. You'd need to
own a really top amplifier and
loudspeakers to do it full justice.
Recommended retail price of the
Yamaha CDX-1110 is $1899. For
further information, consult your
local Yamaha retailer or Yamaha
Music Australia Pty Ltd, 17-33
Market Street, South Melbourne,
Victoria 3205. Phone (03) 699 2388. 16]
OCT0BER1988
23
Electronic Australia Kits
KA-1109 Electric Fence
KA-1115 30<1N amp module
KA-1116 30/JN power supply
KA-1117 30<1N speaker prntector
KA-1119 Transistor tester
KA-1220 Signal •acer
KA-1230 Zener diode tester
KA-1390 Freq. counter 50MHz
KA-1392 Prescaler 500M Hz
KA-1428 Funcion generator
KA-1430 Vocal canceller
KA-1505 TAI Han effect
KA-1506 Transistor asst ignition
KA-1508
KA-1522 "f:it~
KA-1535 ~itionkiUer
KA-1550
uxe car alarm
KA-1556 Ultra sonic move det.
KA-1500 Railmaster controner
KA-1574 30V 1Ara,wer supply
KA-1582 House arm
KA-1595 Ditta/ capacitance meter
KA-1598 40 inverter 121230V
KA-1610 300W inverter 121230V
KA-1630 12V lamp flasher
KA-1635 AM/FM stereo tuner
KA-1636 AM/FM remote control
KA-1650 Playmaster 60/60
KA-1652 Blueprint 60/60
KA-1660 Electric fence
KA-1670 Light saver
KA-1675 Saaecher car alarm
KA-1677 Audio oscillator (metered)
KA-1681 3 band short wave radio
KA-1682 Dual track power supply
KA-1683 Battery monitor
KA-1687 Electronic rain gauge
KA-1688 Electronic strotiosoope
KA-1689 Ex~. power supply
KA-1690 DI ox
KA-1691 TV colour bar/pattern gen
KA-1692 Voice operated relay
KA-1693 Metronome
KA-1694 VolUcontinuity test
KA-1695 AC/DC Millivoltmeter
KA-1696 Econ. Temp probe DMM
KA-1697 Utility timer
KA-1 698 Tran, FET, Zener lest
KA-1699 Bench amp- signal trace
KA-1700 Power transistor tester
KA-1701 RF detector r,.ooe
KA-1702 50MHz Dig req meter
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!i~~~n;i
Handy 100I. Will clip 10
and hold small nuts, bolts,
washers, etc.
Cat. TH-1842
WAS $6.50
If
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NOW $4.95
IC EXTRACTOR~ --~
One piece metal construction, ' Y )~
8 - 40 pins,
.' ;
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Cat. TH-1818
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NOW $2.95
SAVE $1.30
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;/ I
J/ J/
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j/
v·
Government
Instrumentalities, Schools,
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KA-1703
KA-1704
KA-1705
KA-1706
Line Filter
FM Receiver
Stroboscopic Tuner
Cheap capacitance meter
$39.95
$55.00
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$16.95
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KM-3015 LisleninJ post
KM-3030 Ultrafld ity preamp
KM-3040 Dual ~ed modem
KM-3042 Spee synthesiser
KM-3050 Workhorse amle
KM-3056 1OOW module ess MFets
KM-3061 Miaophonereeamp
KM-3063 Uo satellite ecoder
KM-3064 Octave EQ mod
KM-3065 RS true 232 interface
KM-3067 NiCadchar~
KM-3068 FMminder g
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KE-4014 Mixer preamp
KE-4023 Si~nal Spkr protector
KE-4029 Ni ad baltery,1aarger
KE-4033 Temperature obe
KE-4050 ETl480 50W amp module
KE-4052 ETl480 1OOW amp mod
KE-4048 ETl480 power supply
KE-4200 5000 power amp
KE-4204 5000 1(J octave ~aliser
KE-4220 ETl499150W Mos et amp
KE-4405 ETl581±i-15V power sup
KE-4666 RS232 Centronics inter/I
KE-4690 ETl342CDI
KE-4698 4 sector house alarm
KE-4711 Mini FM transmitter
KE-4722 RS232 Commodore
KE-4724 Parametric equaliser
KE-4725 Solder iron temp control
KE-4728 Ring tone customiser
KE-4729 Guitar preamp
KE-4730 Solar gen pisupply
KE-4733 Active Crossover
$39.50
$22.50
$14.95
$32.95
$27.50
$34.50
$29.50
$499.00
$219.00
$109.50
$27.50
$32.50
$79.50
$29.95
$9.95
$16.95
$23.50
$39.50
$29.95
$45.00
$12.95
$39.95
Silicon Chip Kits
KC-5010 Capacitance meter
KC-5012 Car radio power supply
KC-5013 1GHz Digi Freq meter
KC-5015 Telephone ringer
KC-5016 Speed control/dimmer
KC-5017 24 to 12V converter
KC-5019 100W amp module
KC-5021 Protector car alarm
KC-5023 Low ohms adapt DMM
KC-5027
KC-5028
KC-5029
KC-5031
KC-5032
KC-5033
KC-5034
KC-5035
KC-5036
KC-5037
KC-5038
KC-5039
KC-5040
Ph meter
Train controller
CD Hiphone amp
Optical tacho
DISCO Light
Srudio 200 Preamp
Remote for Car Alarm
Plasma discharge
Wireless doorbell TX
Wireless doorbell RX
Universal power supply
Vader Voice
Speaker phone
Jaycar Kits
KJ-6502 Syntom drum synlh
KJ-6504 8 channel mixer
KJ-6505 Console Psupply above
KJ-6531 2801 lfJ octave Eq.
KJ-6535 2010 1Oband stereo Eq.
KJ-6655 Hall EffectTrigger kit
KJ-7000 Red light Hasher
$49.95
$89.00
$24.95
$49.95
$159.50
$229.00
$79.50
$229.00
$16.95
$42.50
$12.95
$19.95
$89.00
$42.50
$595.00
$119.00
$239.00
$169.00
$49.95
$19.95
$27.95
$28.95
$299,00
$19.95
$18.95
$59.00
$38.95
$79.50
$29.95
FAMOUS
TOWERS
BOOKS FROM JAYCAR
TRANSISTOR SELECTOR
• Hardcover • Over 27,000 listings
Cat. BM-4554
'
JAYCAR
Soldering Kit
Designed for general purpose soldering .
This ktt includes a 30 watt 240V so
ing iron and quality metal stand ·
sponge, a !<lngth of solder all
solderwick.
$29.95,.
SAVE ~
$35
DIGITAL IC
SELECTOR
$29.95
DIODE &
SCRINDEX
Quartz Crystal
Clock Movement
• AA battery that lasts for 1 year
• ±15 seconds/month accuracy
• NEW MODEL
• Hook for wall mount
• On/off switch
SUPPLIED WITH 3 SETS OF HANDS
Cat.XC-0100
• 1CYs of 1000s of
SCR's, Triacs,
Diodes & DIACS
listed
Cat. BM-4560
$29.95
IC INDEX
• Reference book
for both linear and
digital IC's,
~ .
Cat. BM-4562
- ~ ...._
$29.95
OPAMP&
LINEAR
EPROM Eraser
• Over 5000 linear
IC's with specs etc.
Cat. BM-4556
~~
~
$29.95
Great replacement electret mic inserts for
tape recorders, etc. Handy for hobby
projects. Includes data sheet and
application circuit. Operated from a single
1.5V battery. 10mm diameter. 50Hz 15kHz.
Cat. AM-4010
$1.95
10+ $1 .65 ea
Ideal for the hobbyist
and handyman. Our
lowest price 240 volt
quality iron has a
stainless steel barrel
and is supplied wtth
free solder.
Spare tip
Cat. TS-1453 $4.95
Cat. TS-1450
ONLY
$16.95
• Spees on
13,000 IC's
Cat. BM-4558
11 you wish to purchase from us, simply
send us your official order and we will
give you a complimentary 30 day account.
''Hot stick"
Soldering
Iron
$12.95
e------l!
o----0
. . q BACK IN STOCK SPEAKER CLOTH
<!!!'!!!!!!!!!!I!!!
BNC Male 10 double
binding posts/Banana
sockets
Cat. PA-3666
$9.95 ea
10+ $9.50 ea
BNC Female to
Double Banana Plugs
Cat. PA-3668
$8.50 ea
10+ $8.00 ea
Up until now, if you wanted speaker
cloth you had the choice of black or
blackl We now have available brown
speaker cloth.
Top quality, acoustically transparent.
Cat. No Colour
Size
Price
CF-2751 Black
1 x 1m
$9.95
CF-2752 Black
1 x 1.7m $13.50
CJ:-2755
1 x 1.7m $13.50
SAVE ON GENUINE
CANNON
WE'RE OVERSTOCKED!!
3 Pin Line Male
Cat.PP-102~
$4
==I...~
-~
-~
~
SAVE $1.25
3 Pin Line Female
Rack Cabinets - see our catalogue Rack Frames - Seaourcataloguefor
full details
for full details
44mm
Natural
Cat. HB-5411
44mm
Black
Cat. HB-5410
88mm
Natural
Cat. HB-5413
88mm
Black
Cat. HB-5412
132mm Natural
Cat. HB-5415
132mm Black
Cat. HB-5414
132mm Economy Black Cat. HB-5402
each
$65.00
$65.00
$75.00
$85.00
$90.00
$95.00
$72.50
5+
$62.00
$62.00
$71.00
$80.00
$85.00
$90.00
$67.50
Cat.
Cat.
Cat.
Cat.
Cat.
Cat.
6 unit frame (370mm)
Panel set for 6 unit
18 unit frame (907mm)
Panel set for 18 unit
30 unit frame (1450mm)
Panel set for 30 unit
w-
Cat.PS-1032~ ~ ~ ~
3 Pin Chassis Plug
Portasol soldering
iron, bring it into
any Jaycar store for
a FREE gas refill
~I
PP-1020
SAVE $1.25
3 Pin Chassis
Cat. PS-1030
~
i
Socket
$4.50
SAVE $1.45
SAVE30%ON
BUG BOXES
DATAKPCB
PRODUCTION
Now available. Make printed circuit boards
from magazine pages or original artwork.
See our catalogue for full details.
KIT ONLY $99
$6.95
TAL 50 pieces Cat. RG-5003
es: (10 of each) 0.047, 0.056, 0.068, 0.082, 0.1
European Made MAINS
FILTER BARGAIN
10+$8.95ea
DIALDRUM/
EVER
ONLY $159
About 20 dial drums and 2.5 metres of dial
cord.
CORDPACK
All for only $5
Cat. HM-3130
~~-
NORMALLY $3.75 each
NOW ONLY $10 for 10 or
$1.50 each cat. LT-3020
BELOW NORMAL W HOLESALE PRICE
PRESS RELEASE
tJJearCustomer,
There are times when due
to circumstances beyond
our control some
advertised products may
not be in stock when our
a d s appear.
We suggest you phone to
check availability.
DIGITAL PANEL
METER
CATALOGUE
A brand new 18 page Lascar catalogue
is available from the Australian
representative, Jaycar Electronics. The
catalogue features the latest Surface
Mount Technology DPM's from Lascar •
■ the wo rld's leading DPM manufacturer.
Panel meters are available in both
liquid crystal and LED-type displays. All
DPM's come complete with snap-on
bezels. Full technical information Is
• 300 watts RMS into 4 ohms
provided for the 50-odd products
• 200 watts RMS into B ohms
described.
K~ includes PCB, heatslnk & components
Contact Jaycar branches or Head
Cat. KA-1115
Office for a free copy of the catalogue.
300 WATT
PLAYMASTER AMP KIT
SAVE $10 NOW $109.95
Telephone~ 300 WATT POWER
Diverter ~~ •SUPPLY
Includes transformer, rectifier and filter
caps .
NEWMODEL
Cat. KA-1116
This professional quality product will
automatically transfer Incoming calls to
another telephone number. Your
business will not lose any important calls
If you move, as incoming calls can be
diverted to your new office address. Two
telephone lines are required while the
_ _ _ _ _ _ _ _ _ _ _. . YT-6510 is not Telecom approved it is a
Outdoor Baluns • 300 to 75 ohm
complete with small length of cable to
attach antenna and F59.connecto, for
coax connection.
A GREAT
WAYTO
NEVER BE
OUT OF THAT
ODD
GREENCAP
AND SAVE A
PACKET AT
THE SAME
TIME
'------------J
CORDLESS PHONE
LOWEST PRICE
TV INSTALLERS
BARGAIN
$6.95
TAL 50 pieces Cat. RG-5002
lues: (10 of each) 0.018, 0.022, 0.027, 0.033, 0.039
I
•
$6.95
Values : (10of each) 0.0068, 0.0082, 0.01, 0.012, 0.015
$9.95
':/ ~t
$6.95
Values: (10 of each) 0.0027, 0.0033, 0.0039, 0.0047, 0.0056
• 4 amp 240V PCB mount
• For full details see last months ads
Cat. MS-4008
originally selling for $269
Don't ever run short of that greencap again. 5 easy to buy, low cost packs which
represents a considerable saving over individual prices.
Each pack contains 1o of each value and packs cover the complete range from
0.001 uF to 0.1 uF.
Values: (10 of each) 0.001, 0.0012, 0.0015, 0.0018, 0.0022
TOTAL 50 pieces Cat. RG-5001
BUG BOX Cat. HB-63
ONLY $4.15 SAV
LSI BUG BOX cat.
ONLY 5.55 SAV
BUG CASE Cat. HB-6366
ONLY 6.95 SAVE 3
BUG CAGE COVER
ONLY $4.85 SAVE $2.10
Jaycar Introduces the Easy way to
Buy Greencaps
TOTAL 50 pieces Cat. RG-5000
See our catalogue for full detai
Cat. HB-6370
$109.50
$49.00
$139.50
$89.00
$169.50
$ 129.00
If you own a
$4.25 ' - l _ _ _ ~
SAVE $1.25
" -
$a
HR-5210
HR-5215
HR-5220
HR-5225
HR-5230
HR-5235
SAVE $10 NOW $95
SPEAKER PROTECTOR
KIT
Cat. KA- 1117
SAVE $2 NOW $21.50
very well made product. A 7.5V AC
adaptor is provided.
Cat. YT-6510
WAS $249
NOW $219
·1
RS232 TO
CENTRONICS
ADAPTOR
• Interface a printer to RS232 serial port
of your computer
• Includes PCB, DB25 A/angle plug &
components.
Cat. KE-4666
SAVE$2.50
NOW ONLY $30.00
NEGATIVE ION GENERATOR
A METER FOR ALL SEASONS
240 volt - SAVE $50
For full specs on all of these products see our 1988 catalogue.
Cat. YX-2905
ECONOMY POCKET
:t.J~
• 20,000 ohms/Volt
• Size 80 x 50 x 30mm
Cat. OM-1001
1-l- "'(,j~
5"1.JC
$17.50
LOW COST MODEL
• 10,000 ohms/Volt
• 12 ranges
Cat. QM-1015
Indoor TV ~
Antenna i;
UHF/VHF/FM
~
The ultimate indoor antenna - built-in
mixer for UHFNHFIFM - wide
frequency band from 40MHz - 890MHz.
Directional fine tuning possible with
variable direction inner reflector - easy
to mount - 75 ohm impedance with
coaxial cable anc! plug.
Cat. L T-3130
\
SAVE $3
ONLY
$31.95
Solar
Powered
Exhaust
Ventilation
Remove gas, fumes, humidity, etc by
using the suns free power - solar. It will
remove about 35 cubic metres of air
every 1/2 hour in bright sunlight.
Ideal for:
• Boats •Caravans• Port-a-loos
• Greenhouses • Sheds• Holiday
homes• Backyard dunnies
• Kitchens • Weekenders, etc.
Cat. YX-2500
SAVE$5
OCTOBER ONLY
$44.95
MicroChart
SELLOUT
Bye-bye MicroCharts. Over the years we
have sold hundreds of MicroCharts, but
now the time has come and their time is
numbered .
M icroCharts are professional, comprehensive, plastic summary cards packed
with key time-saving information on:
microprocessors, electronics,
programming, and tools for busines s.
• Solid plastic • lasts a lifetime • 2
comprehensive sides • Crystal clear
printing • Instant access to data you need
See our 1988 catalogue for full details.
• "C" Language
Cat. BM-8512
• Basic Intro
Cat. BM-851 0
• 8080 & 8085
Cat. BM-8501
• 6502 (65XX)
Cat. BM-8502
• Z80 CPU
Cat. BM-8500
• 8086 & 8088
Cat. BM-8508
• Alogrithms
Cat. BM-8504
• How to sample
Cat. BM-8514
• Wordstar
Cat. BM-8506
Thinking about
investing in a
VIFA speaker kit?
Let Jaycar tempt you in to making that
decision in October. SAVE UP TO $100
PER PAIR.
All our stores have the new upgraded Vffa
kits on demonstration, so drop in and
have a listen.
Remerrber, you willpay about twice as
much for similar pre-built imported speakers. In fact they will probably have Vita
speakers in then anyway. See our 1988
, catalogue for full details.
,. (Demonstration speakers are not at
Concord).
SA 130 3 way kit complete with
tabinets and crossovers. 130W RMS
power handling.
Cat. CS-2465/CB-2467
SAVE
$100
ONLY
$1099 pr
J
$26.50
POPULAR MODEL
• 20,000 ohms/volt
• 10A DC range
Cat. QM-1022
-t~ .
"-'"''-~~
~\:\)I
$39.95
ULTIMATE ANALOGUE
• Transistor tester
• Centre zero adjust
• Peak to peak & RMS
Cat. QM -1050
$79.95
10A DIGITAL
• Tran sistor tester
• Vinyl case
Cat. QM-1530
$89.95
CAPACITANCE TESTER
• 10A digital
• Transistor tester
Cat. QM-1540
$129
4.5 DIGIT 10A
• Transistor tester
• Diode tester
• Data hold
Cat. QM-1560
$179
TOP DIGITAL
• With frequency counter
• Capacitance tester
• Transistor tester
• 20A current
• High impact case
Cat. QM-1555
SA-100 2 way kit complete with
cabinets and crossovers. 100W RMS
power handling.
Cat. CS-2460/CB-2462
SAVE
$70
ONLY
$729 pr
$159
DIGITAL AUTO TUNE-UP TESTER
• RPM & dwell on 8,6,5, and 4 cylinder
and more
Cat. QM-1573
$139.50
DIGITAL L-C TESTER
• Cap range 2 to 200uF
• LC range 2mH to 20H
Cat.OM-1575
$219
DIGITAL AC CLAMPMETER
•400 amp
• LCD display
Cat. QM-1570
$139.95
SA-70
2 way kit complete with
cabinets and crossovers. 70W RMS
power handling.
Cat. CS-2471/CS-2472
SAVE
$50
ONLY
$449 pr
J'
ALL ONE PRICE
WERE$12.50
~
NOW $9.95
, :~·
0
•
SAVE $2.5~ },(~~
··· -:.\ , SA-50 2waybookshettkltwith
,/i''t,~_-i.,
_, · ··... 'cabinets and crossovers. 30W RMS
W 0 n't
),'¾j-'•·4" · ' ,:. ,. power handling.
' ;..;f<t . /. ~- '°''.· Cat. CS-2450/CS-2452
last
·c·-\:' -<- ··'
,6~"~-·-~-, • t.\_
. ,.
SAVE
l_ong
:t,~~
~-~$ 20
!liB'lf~~t~~tONLY $379
SPEAKERPHONE
Ref: Silicon Chip Sept 1988
High quallty hands free telephone adaptor
that works extremely well.
Full kit including box, panel, isolating transforme r and all parts.
Cat. KC-5040
ONLY $89
Thin Insulation Tape
10mm diameter x 20 metres long. Japanese made
and black In colour. Flame retardant and cold and
weather resistant. LIMITED QUANTITY
Cat. NM-2805
ONLY 60t roll
SAVE $7 on ADCOLA 240V
Soldering Irons
S30
12 wan
Cat. TS -1492
ONLY $29.95 SAVE $7
S50
16 wan
Cat. TS-1494
ONLY $32.95 SAVE $7
SOLAR ENERGY SENSATION
*
.,.
DUE EARLY
OCTOBER
..
0.45 VOLT SOLAR
CELL MODULES
·*;i
•,
-
..
to utilise
, Size 75 x 45 x 6mm
Cat. ZM-9005
;)
$6.50
10+ $6.20 ea
~
,.,
. .•
*
*
$29.95
SOLAR PANELS··*· "
2 Models
) ,
6 volts <at> 240mA
· '
12 volts <at> 120mA
These are quality made solar panels with
aluminium picture framing around the
edges for durability and ease of
mounting. The solar cells themselves are
covered by a clear resin for long life.
Each panel measures 327(L) x 165(W) x
18mmthick.
SOLAR EDUCATION KIT
12 volt panel
Cat. ZM-9008
Cat. ZM-9009
<at>
120m
A
$79
The solar panel in the lid will charge up to 4
x AA NiCads in a fairly short time. It is ideal
for yachts, campers or anywhere where
240V is not available. It is NO DEARER
than an ORDINARY NiCad charger but
takes about the same time to charge in
reasonable sunlight.
Cat. MB-3502
Size: 65(W) x 30(H) x 95(D)mm
WAS $17.95
NOW $14.95
*.
complete with:
• Solar cell module
• Solar energy booklet explaining
the whys and hows of solar energy
• Small DC motor
• Screws and nuts
• Wire with motor clips
• Coloured spinner discs
• Paper earoplane and bird models
• Plastic turntables with 4 sizes, 5/8",
1", 1 1/2" and 2"
• Plastic fan-spinner
Discover for yourself how to harness
the nergy of light and employ It in
countless practical applications.
Solar energy uses are limited only by
your imagination.
Cat. KJ-6690
ONLY $9.95
Loudspeaker P.A. Bin Enclosure
Designs Book
J' ·,
Fane Acoustics UK, makers of speakers for the
likes of Pink Floyd, David Bowie, Genesis ,
Iron Maiden etc. have produced an absolutely
fantastic book on P.A. bin designs. The book
begins with construction info in general, i.e.
what materials to use, how to join timber,
how to brace the cabinets, sealing, lining,
wiring, crossovers, impedance matching, etc.
The second section includes 22 separate
detailed designs for: reflex cabinets,
horns, wedge monitors, folded horns, w bins etc.
Designs accommodate 10",
12", 15" and 18" speaker components.
This book is cram packed with information.
Save a fortune and build high power
P.A. bins for yourself and friends.
SOLAR PLANT
TURNTABLE
No more lopsided plants.
Promote healthier well
developed plants.
Will handle up to
15 kg of weight.
Also ideal for store
window displays.
Cat. YX-2503
$17.95
Cat. BF-4150
~'~~'
■
1
VISA
$14.95
HEAD OFFICE
MAIL ORDERS
POST & PACKING
115 Parramatta Road Concord 2137
P.O. Box 185 Concord 2137
~o
~~49~9 ~ ~.~~
Telephone (02) 747 2022
HOTLINE (02) 7471888
$25
$49.99 s 4.50
Telex 72293
FOR ORDERS ONLY
$50
$99.99 $ 6.50
0
100
_FA_C_S_I_M_IL_E~(0_2~)_74_4_0_7_6_7_ _ _ _T_O_L_L_FR_E_E_(D_D_8)_0_22_8_8_8_ _v_ER_s__ __s_10_.oo_ _ - - ,
•
1
*
Now you can experiment with solar energy ... the energy source of the future. Our
solar education kit is designed to let you build your own solar models. This kit comes
6 volt panel<at> 240mA
$79
Solar Battery
Charger
.
How often have you been away on holiday leaving your car at home, and when returning finding your battery as flat as a tack I You need to push the car out of the
garage, down the driveway and out onto the street so you can connect jumper
leads, or wait an hour or more for the NRMAIRACQ/RACV to arrive.
Well, with this handy gadget all that is gone. When you park your car for extended
periods (i.e. 4 or more days) simply plug this into your cigarette lighter socket and sit
the unit on the dash board, or near the window of the garage. When you return
home - no more dead batteries. The unit consists of solar cells in a housing with 1
metre of cable and cigarette lighter plug.
Cat. MB-3503
Size 96 x 65 x 6mm
Cat. ZM-9006
10+ $3.75 ea
*"·
' -,,
·.,,:...
SOLAR CAR-BATTERY BOOSTER
0.45V
1000mA
$3.95
'.~9. FREE power '.ro~ the sun.
*l·
1
!. .
Ideal for experimenters. Connect in
series or parallel if you wish. Terminal
strap enables easy connection to other
cells.
Two handy sizes
0.45V
400mA
*'
.
Jaycar proudly intr?_duces a range of direc.t imported solar pro.ducts
;~I~ ,
MAIL ORDER VIA YOUR
fr
ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50
L--------------------------------------'
SYDNEY • CITY
117 York St. (02) 2671614 ·
Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 • 12
GORE HILL
188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 •
Mon-Fri 9 - 5.30 Sat 9 - 4pm
CARLINGFORD
Cnr. Carlingford & Pennant Hills Rd (02) 872 4444 Mon-Fri 9 • 5.30 Thurs 8.30 pm - Sat 9 • 2pm
BURANDAQLD
144 Logan Rd (07) 393 0777 Mon-Fri 9 • 5.30 Thurs 8.30 - Sat 9 -12
CONCORD
115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sat 8.30 - 12
MELBOURNE-CITY
Shop 2, 45 A'Beckett St City (03) 663 2030
Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12
HURSTVILLE
121 Forest Rd (02) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 -12
SPRINGVALE VIC
887-889 Springvale Road Mulgrave (03) 547 1022
Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 - 12
Build this 5-element
FM antenna
How's your FM reception? Not up to
scratch? You can greatly improve
matters by building this 5-element Yagi
antenna which is designed specially for
the FM band.
By LEO SIMPSON & BOB FLYNN
It's amazing isn't it. So many people spend thousands of dollars on
their hifi equipment and then just
string up the simple dipole antenna
that came with their receiver or
tuner.
It really is a waste. After all,
most people know that to obtain
28
SILICON CHIP
good TV reception, they need a
good antenna installation. Well, the
same applies for FM. If you want
the best sound quality, you need a
good antenna.
Sure, if you live in a strong signal
area, you might get away with just
a tap off your existing TV antenna
but a separate FM antenna will
always give a better result. The
problem is: what antenna to buy?
There are very few available and of
those that are, few are suitable for
fringe areas.
To be specific, the most common
FM antenna available is a 3element Yagi which gives, at best,
about 6dB gain with respect to a
simple dipole. These are OK in
strong signal areas but we wanted
more gain. We also wanted more
directivity to cope with poor recepFig.1: this diagram shows all the
details of the 5-element antenna. At
top is a plan view while the other
diagrams show hardware and
element mounting details.
►
.
.
E
E
B
~
a:
,f;l
E
ita:
E
E
E
\::!
.
.s
.s
;!
~
a:
,-
w
~
iS
IlliS
9
:;;
w
~
a:
a:
0
0
E
.s
::.
...
0
,f;l
,f;l
a:
iS
!!i
N
..,~
=
z
N
-L
BOOM 2222mm
A
A
C
A
A
19
19
...
N
~
...
N
...
N
50
63D
627
363
~
0
562
J
~694
69/
FOLDED DIPOLE INSULATOR
3mm ACRYLIC
-==------------Jil
-------- -----'140D
-":.:....- - ------- - - -- -~...-----------~~-
~
DIPOLE TOP PIECE - 1 REQO.
642
680
DIPOLE BOTTOM PIECE - 2 REQO.
I
0
19
19
50
3/16" x 70mm
WHITWORTH SCREW
I
0
FOLDED DIPOLE SPACER - 1 REQD.
19mm SQ. ALUMINIUM TUBING
MATERIAL:- FOLDED DIPOLE, IHRECTORS ANO
REFLECTOR : 10mm DIA.; 1mm WALL
THICKNESS, ALUMINIUM TUBING
BOOM : 19mm SQ., 1.8mm WALL
THICKNESS , ALUMINIUM TUBIIG
0-
FASTENERS : STAINLESS STEEL
FOLDED IHPOLE BOTTOM PIECE
0
REFLECTOR ANO DIRECTORS TO
BOOM CONNECTION
3/16" x 60mm
WHITWORTH SCREW
FOLDED DIPOLE TOP PIECE
FOLDED IHPOLE ENO
0
;
42
IHPOLE ENO PIECE
2 REQO.
=,,
ELEMENT
BG x 13mm STAINLESS STEEL
SELF-TAPPING SCREW
BOOM
SPLIT WASHER
I
0
FM ANTENNA
FOLDED DIPOLE TO BOOM CONNECTION
OCT0BER1988
29
Fig.2: the dipole insulator plate has wing nut terminals to connect 300!1 ribbon
or a 300!1 to 75!1 balun. The plate is made from Perspex, Lexan or other
acrylic material. The square boom makes mounting easy.
more directional. To put it another
way, it has a narrower acceptance
angle. This means that reflected
signals coming in from the side of
the antenna will be suppressed.
This is worthwhile because the
more suppression you can obtain
for reflected signals, the less
distorted the resulting stereo sound
will be.
In other words, if you have problems with distorted sound from
some FM stations (due to reflected
signals or "multipath" ), you should
be able to obtain a worthwhile improvement using this antenna.
Another reason to build this
antenna is to improve on the signal
available from a normal 3-element
array. While a gain figure of about
+ 2dB with respect to a 3-element
array may seem modest, it can
make a substantial difference to the
apparent signal-to-noise ratio when
receiving weak stations.
Tools you will need
Fig.3: this topside view of the antenna shows how the folded dipole is attached
to the square boom. Note the short section of aluminium tubing which acts as
a spacer between the underside of the boom and the dipole insulator plate.
Whitworth or other machine screws hold it all together.
tion conditions where multipath is a
real problem.
After looking at what's available,
we decided to design and build our
own. Actually, we ended up
building a number of variations
before settling on the design
presented here.
The new antenna is a 5-element
Yagi array. It has a folded dipole, a
30
SILICON CHIP
single reflector and three directors.
It has an estimated gain of between
8 and 9dB gain with respect to a
dipole and an improved front-toback ratio compared to a 3-element
array.
Narrow acceptance angle
As well as an improved front-toback ratio, this antenna also is
Most enthusiasts will have all the
tools needed for this project. You
will need a hacksaw, electric drill
and a vice. It would also help if you
have a drill press but you can do
without. Apart from an antenna
clamp (U-bolt and V-block bracket),
no special hardware or fittings are
required.
Making and assembling this
antenna is very straightforward. If
you have all the materials available
you can probably do it in a single
afternoon.
The diagrams of Fig.1 show all
the details of the 5-element antenna. These diagrams show the
dimensions of all the elements and
the various hardware bits you will
have to make to assemble the antenna. At top is a plan view showing
the length of all five elements and
their spacing along the boom.
Fasteners
After a few years' exposure to
the elements, many antennas are in
a poor state. Aluminium may not
"rust" but it does corrode, particularly in seaside areas or in
metropolitan areas where there is a
lot of industrial fallout. This corrosion can be a lot worse if you don't
use the right screw fasteners.
We recommend the use of
What is a Yagi antenna?
The Yagi is not a new antenna
design by any means. It was
developed by H. Yagi and S. Uda
at Tohoku Imperial Univers ity in
Japan in 1926.
In the VHF (very high frequency)
bands, of which the FM band
(88-108MHz) forms a small part,
most antennas depend on electrically resonant elements; ie,
elements which are a halfwavelength at the frequency of
interest.
In its simplest form, the Yagi
consists of a dipole element and
an additional slightly longer
parasitic element behind it, called
the reflector. More complex
designs have shorter parasitic
elements in front of the dipole and
these are called directors.
The reflector and directors are
referred to as parasitic elements
because they also resonate over a
frequency range similar to that of
stainless steel screws throughout,
whether for machine screws or
self-tappers. They do cost a little
more but they last indefinitely.
Don't, on any account, use brass
screws. When used to attach
aluminium elements these will corrode away almost before your eyes.
Nor do we recommend galvanised,
bright zinc or cadmium plated steel
screws. In seaside areas these can
be visibly corroded with just a few
days' exposure.
In rural areas, well away from
the sea or city pollution, you can
probably get away with galvanised
screws but the antenna will last
longer if you paint it.
Starting work
Before you start, make sure you
have obtained all the aluminium
and hardware listed in the Bill of
Materials. After all, you will be
frustrated if you get half-way
through and find you can't progress
farther because you lack screws or
some other item. Get 'em all before
you start.
Cut the boom to length first. It is
2222mm long. It is made of 19mm
square aluminium tubing which
the dipole. Part of the electromagnetic ene rgy they capture is
re-radiated and picked up by the
dipole. Hence the director and
reflectors add considerably to the
signal which is picked up by the
dipole on its own.
By suitably dimensioning the
reflector and directors, it is possible to determine the overall frequency coverage of a Yagi antenna, its gain and its directional
characteristics. In general, the
more elements in a Yagi array, the
higher will be its gain and the
smaller the forward acceptance
angle .
There is a law of diminishing
returns though. Above a certain
number of parasitic elements, no
useful increase in gain is obtainable . There is a definite tradeoff between the practical size of a
Yagi and the amount of gain it
provides .
makes drilling and assembly easier.
(Yes, if you are experienced in
metalwork and have access to a set
of V-blocks and a drill press, you
could substitute 25mm diameter
tubing for the boom).
While you're at it, cut the folded
dipole spacer which also uses the
19mm square tubing. It is 50mm
long. You should have a piece of
tubing about 120mm left over as
scrap. Don't throw it away. It will
come in handy later.
Now cut the 10mm diameter tubing for the director, three reflectors
and parts for the dipole. Remember
the old adage about "measure
twice and cut once". It's hard to
lengthen elements that are too
short. Note that the three directors
are all the same length, 1270mm.
Next, centre-punch the boom for
all holes prior to drilling. Note that
the boom is 2222mm long and the
total of the element spacings along
the boom is 2182mm - see the plan
diagram on Fig, 1. Mark the hole
centre position for the reflector element first, 20mm from one end of
the boom, and then work your way
along.
If you have a drill press which
Bill of Materials
Alumini um
2.3 metres of 19mm square
aluminium tubing with 1 .8mm
wall thickness
8 .5 metres of 10mm diameter
aluminium tubing with 1 mm
wall thickness
Hardware
1 piece of thick Perspex, 1 20
x 40 x 3mm
1 U-bolt and clamp to suit mast
4 8G x 13mm screws
2 8G x 32mm screws
2 3/16-inch Whitworth
roundhead screws 70mm
long
1 3/16-inch Whitworth
roundhead screw 60mm long
2 3/ 16-inch Whitworth
roundhead screws 32mm
long
2 3/16-inch Whitworth
roundhead screws 1 9mm
long
7 3/16-inch ID split or
lockwashers
7 3/16-inch Whitworth nuts
2 3/16-inch Whitworth wing
nuts
2 3/16-inch ID flat washers
Note: all screws, washers and
nuts to be stainless steel
Miscellaneous
Mast and wa ll mounts or
bargeboard mount (hockey stick
style) , 3000 to 750 in-line balun
(for outdoor use). semi-air spaced coax cable (Hills SSC32 or
equivalent). plastic cable ties,
silicone sealant.
lets you drill all the element holes
square through the boom you are
fortunate. If not, mark the hole centre positions on both sides of the
boom and drill from both sides. If
you don't get the element holes lined up properly, you will have the
elements skew-whiff.
A few words of advice on drilling
is appropriate here. Drilling in thin
wall aluminium can be a problem
and many people will tend to end up
with holes that are more triangular
than round. The way around this
problem is to drill all the large holes
(ie, all 10mm holes) undersize and
then ream them out to the correct
size using a tapered reamer.
OCT0BER1988
31
though because the dipole should
be assembled and mounted on the
boom first.
Making the dipole
Fig.4: the ends of the folded dipole are fabicated using 42mm lengths of
aluminium tubing shaped to mate with the upper and lower pieces. They are
held together with a 70mm long machine screw, nut and split washer.
Fig.5: the mast clamp and V-block assembly can be purchased from electronic
parts or automobile accessory retailers. Use galvanised types if possible.
Avoid cadmium plated or zinc plated clamps which tend to rust out.
Be careful when reaming holes
out though because it is quite easy
to get carried away and then end
up with holes that are oversize. Use
a scrap piece of 10mm tubing to test
when the holes specified at 10mm
are the correct size.
32
SILICON CHIP
Each director element and the
reflector is held in the boom with a
self-tapping screw, as shown in
diagram A of Fig.1. Drill a 3mm hole
at the centre point of each element
but only through one side. Don't
mount the elements on the boom yet
The folded dipole is made from
five pieces of 10mm aluminium tubing, three long and two short. The
detail of its assembly can be seen
from the diagram at the bottom of
Fig.1. Two short tubes, shown as
diagram E on Fig.1, are cut and
shaped so that they key in with the
top and bottom elements of the
dipole. Further detail is shown in
the photo of Fig.4.
The top and bottom pieces of the
dipole are held at each end with a
70mm long 3/16-inch Whitworth
screw, together with a nut and lock
washer. At the centre, the lower
halves of the dipole are terminated
on a insulating plate (shown in
diagram D of Fig.1). This plate is
made of 3mm acrylic (Perspex or
Lexan). The dipole halves are each
secured to the insulating plate with
a 19mm long 3/16-inch Whitworth
screw, nut and lockwasher.
Terminals for the dipole are provided with two 32mm long 3/16-inch
Whitworth screws, each fitted with
a nut and lockwasher plus a wing
nut and flat washer.
The insulating plate is secured to
and spaced off the main boom via a
section of square tubing, shown as
a "folded dipole spacer" in
diagram F of Fig.1. The insulating
plate is secured to the spacer with
two 8-gauge 32mm long self tapping screws which go through
the spacer and into the boom. The
top piece of the dipole is then
secured to the boom with a 60mm
long 3/16-inch Whitworth screw,
nut and lockwasher.
The details of the dipole insulating plate and fixing to the
boom can be seen in the photos of
Fig.2 and Fig.3. Note that while we
used a white Perspex, you could use
a piece of clear material if that is
what you have on hand.
By this time the antenna looks
just about complete. You need to
add the antenna clamp, to enable it
to be attached to the mast, and you
will need a 3000 to 750 balun to
match it to 750 coax cable. You can
use 3000 ribbon if you wish and
omit the balun, but to obtain the
Fig.6: do you have trouble drilling round holes? You'll do
better by drilling the holes undersize and then reaming
them out to exact size with a tapered reamer.
most interference-free signal, we
recommend coax cable for your
installation.
Unfortunately, many antenna
clamps are sold with a cadmium
plated and passivated finish. These
have a "gold" finish. This may be
adequate for inland areas but they
soon rust in sea air. We may seem
to be paranoid about corrosion but
since the SILICON CHIP editorial offices are only a few hundred metres
from the seaside we are very aware
of just how quickly antennas can
rot away.
If you can, buy antenna clamps
that are heavily galvanised. These
last a lot longer than the cad-plated
jobs. U-bolts and clamps intended
for auto exhaust systems are
generally quite good in this respect.
But be aware that zinc " plated" fittings are not as rust resistant as
galvanised types. Zinc plated fittings have a smooth bright appearance while heavy galvanising
is unmistakable - it has quite a
rough appearance.
If you really want to gild the lily,
go to a ship's chandlers and buy
stainless steel U-bolts and clamps.
They'll last forever; well just about.
We suggest that the ends of
all the elements and the boom be
Fig.7: the reflector and director elements are attached to
the boom using self-tapping screws. All screws, nuts and
washers should be of stainless steel to avoid corrosion.
stopped up with epoxy adhesive (eg,
Araldite), putty or silicone sealant.
This will stop them from whistling
in the wind. Better still, you can buy
Delrin plugs to suit the square
aluminium tubing. These look
neater.
You might also consider painting
your antenna, if you live in an area
where corrosion is a problem. We
suggest you leave the antenna for a
month or so to weather it and then
paint it with an etch primer. Finish
it with an aluminium loaded paint
such as British Paints "Silvar" .
Installation
When you have finished your
antenna you need to carefully consider its installation. There is no
. point in going to a lot of trouble
making it if you don't install it
properly.
Try to install your new antenna
well away from existing TV antennas as these can have quite a
serious effect on the performance.
Similarly, nearby metal guttering,
electric cabling, metal roofing or
sarking (ie, reflective insulation
such as Sisalation) can have a bad
effect on antenna performance.
Don't forget the effect of a hot
water tank which may be lurking
just beneath the roof tiles.
If you live on a busy street, try to
install your antenna as far away as
possible from the traffic side of
your house. That way you will
minimise ignition noise from passing traffic.
Finally, install the antenna as
high as possible above the roof and
guttering. If that is a problem, try to
install the antenna so that it is at
least a half wavelength away from
the nearest metallic object such as
guttering or roofing. This means a
distance of about 1.5 metres away
from guttering.
Take care when installing the
antenna. Safe working with ladders
is particularly important. Take
your time and don't take risks. You
don't want to end up in hospital.
Line up the antenna so that it is
aimed at the main FM stations of interest. If you are really keen, you
could also consider installing a
rotator, to obtain the very best
reception from all stations.
If you are using 3000 ribbon, use
spacers to hold it away from the
mast, otherwise you'll lose signal. If
using coax cable, tie it to the mast
with insulation tape or cable ties, to
stop it flapping in the wind.
~
OCT0BER1988
33
D
DIECAST BOXES
Diecast boxes are excellent for
RF shielding, and strength.
Screws are provided with each box .
H11451 100 x 50 x 25mm . $ 5.95
H1 1452110x60x30mm
$ 6.50
H t 14531 20 x 65 x 40mm . $ 6.95
H 11 46 1120x94x53mm . $11.50
H11462188x 120x78mm ... $13.50
Ht 1464 188x 188x64mm ... S29.50
H 10382 3 x 4 x 2 inches
H10383 3 X 4 X 3 inches
H10384 3 x 4 x 4 inches
H1 03853x4x5inches
H10386 3 x 4 x 6 inches
H10387 3 x 4 x 7 inches
H10388 3 x 4 x 8 inches
H103893w:4x9inches
H103903x4xl0inches
.
.
.
$ 5.50
$ 6.50
$ 7.50
7.95
$ 8.50
. $ 9.50
$
.
$10.50
$10.95
. $11.95
UTILITY BOXES
HORWOOD METAL
INSTRUMENT CASES
(ROUND HANDLES)
8416N
H10461153x 102x203mm $18.95
84/BN
H10462 203x 102x203mm S19.50
84110N
H10463 254 K 102 x203mm S19.95
8411 2N
H10464 305x 102x203mm $22.95
Plastic boxes with aluminium tops.
· and available in four sizes. Very
popular lor projects and very
ecconomical!
H10101 150x90x50mm $ 3.25
H10102 195x113x60mm $ 4.50
H 10103 130x68x41mm $ 2.75
H10105 83x54x28mm
$ 1.95
H 10110 120x65x38mm $ 2.95
H10112 120x65x38mm
(Metal top)
$ 2.95
CROSSOVER
NETWORKS
CPF
CONTINUOUS POWER
FILTEA SPIKE ARRESTOR
The Fortran C PF Filtered Electronic
Spike Protector provides a protective
electronic barrier for microcomputers.
printers, telephone systems and
modems electronic typewriters,
audio and stereo systems and other
sensitive electronic equipment .
The CPF provides protection from
dangerous electrical spikes that can
c~u~ anyth~ng lrom_obvious damage
(like 1mmed1ate equipment failure) to
less obvious harm that can drastically
shorten a system·s life.
CPF's superior circuitry design and
semi conductor technology reSIX)nds
instantly to any potentially damaging
over-voltage. ensuring safe trouble
free operation .
Additionally, CPFs filtering capability
helps eliminate troublesome and
9316N
H1 0467 153 K 76 x 228mm $16.95
H10465 203
Ht0466 254
H10468 305
H 10470 430
93/BN
x 76 x 228mm
93110N
x 76 x 228mm
93112N
x 76 x 228mm
93/17N
x 76 x 228mm
Cat.X10088
$29.95
FREE POSTAGE
FOR SILICON CHIP
READERS
THIS
MONTH
MINIMUM ORDER OF $50 APPLIES
JUST QUOTE THIS ADVERTISE MENT
$29.95
MINIATURE HOBBY VICE
• Lever operated suction grip base
for instant mounting and portability
• Mounts on smooth non-porous
surfaces.
Cat.T 12458 ... only $6.45
K&WMETAL
INSTRUMENT CASES
Used in many projects, these cases
have hammertone finish and are
both versatile and ecconomical
H10478 125 x 40 x 65mm . S 5.95
H1 0479 150 x 55 x 95mm . S 6.95
H 10480 100x92x130mm ... $ 8.95
H 10481150x55x100mm ... $ 7.95
H10482200x80x130mm .. . $ 9.95
H1 0485255x92x 155mm ... $14.95
H10487255x 165x 155mm . $16.95
H10489305x 105x2QOmm . $16.95
SPECIFICATIONS :
4
~~:::u~~:ra~e~ 1
DC
Prima,y Cunent: 4·2A (24V input
~-~e
MASTER
RACK MOUNTING
CABINETS
These superb rack mount cabinets
will give your projects a real
professional appearance!
Just look at these features ...
• All dimensions conform to the
International Standard
• All alumir,ium construction
• Choice of black or natural finish
• Deluxe brush finish anodised front
panel
• Removeable top and bottom lid
• Ventilated lid
Horizontal Depth : 254mm
A = External Front Panel Height mm
B = Mounting Hole Centres mm
C = Internal Chassis Height mm
A B C Finish Cat.No. Price
44 34 38Natura1Ht 0401 $59.50
88 57 82Natura1H10402 $69.50
132 89 126 Natural H 10403 $79.50
44 34 38B!ack H10411 $65.00
88 57 82Black H10412 $75.00
132 89126Black H1041 '.3 $85.00
• Charges from 1 lo 100. C. AA. AAA.
N. and up to 3 x 9V batteries at the
same time.
• Dual colour LEO in first three
compartments to designate 1 •SV
or9V.
• 240V ACl50Hz.
• Approval No. N10637
Cat.M23525 .
........ $59.95
STEP DOWN
CONVERTER DC-DC
~fnfi;:~~
POCKET SIZE
BATTE RV TESTER
• Tests all 9V to 1·SV batteries
including button cells.
STEREO WIRELESS
TRANSMITTER
This unit was developed to allow
portat?le compact disc players to be
used 1n cars by transmitting the
~e;g~~t~;e~utp~tc~~~:~gi_r~fir in
also transmit any mono/stereo signal
~~"::c7ivh ~adphone output to any
8
SPECIFICATIONS :
• Input 3·5mm stereo phone plug .
Impedance 32 ohm .
• Mono/stere<:> switch has plug
mounting chp.
• FM Transmission approx .
90·35MHz (Tuneabfe 89-91 MHz)
• Range 15 metres. {below 1SmV/m
at 100 metres)
• Power 1 ·5V AAA size batteries
(100 hours continuous use)
• Size72 x 38 x21mm
• 12dB attenuation
•Crossover point 800 and 5,000 Hz
• Impedance ohms
0825 PLUG WALL PLATE
• Fitted with OB25P plug. (AS232)
• Anodised aluminium plate.
• Includes mounting hardware.
P10944
$11.95
a
$24.95
Cat. A 16005
3 WAY 150 WATT
CROSSOVER NETWORK
• 16d8 attenuation
• Crossover point 350 and 3.000 Hz
• Impedance 8 ohms
Cat. A16007
$34.95
t-.r.
_,
TEXTOOL SOCKETS
P1701616pin ............... $14.95
P17024 24 pin .
... $18.50
P17028 28 p;n .... .... ... ... . $24.95
P17040 40 p;n .
.. $29.50
A16100
Use these quality, all metal, Piezo
tweeters for great top end sound in
your band speakers, disco sound
system, etc. Rated at 30 watts RMS. ·
in a system they will handle over
100 watts RMS.
Two sizes to choose from :
Size: 4 " x 101,-2•·
Impedance : 8 ohms
Rating : 30 watts RMS
Response: 1.5kHz-14kHz
Dimensions: 102x267x 177mm
Cat. C92082
Normally $49.95.
This month only $39.95
Size: 3"x T
Impedance : 8 ohms
Rating : 30 watts RMS
Response : 2kHz • 15 kHz
Dimensions: 76 x 177 x , 45mm
Cat. C92084
Normally S29.95
This month only $24.95
Dealers, OEM's, etc., phone
(03) 543 2166 for wholesa~ prices
PIEZOSIREN
• 4 piezo units in a high impact
plastic cabinet
• Input 12V DC - 200mA
• Output 115d8 at 1m, dual tone
• Compact size 105 x 85 x 45mm
• Smart design suits interior use
Cal . S15071 ............. ... . $24.95
()
-,
OMNI-DIRECTIONAL
WIRELESS MICROPHONE
Tuneable : 92 - 104MHz
Freq. Response: 50 • 1SkHz
Range: Over 300 feet in open field .
Modulation: FM
Power Source: 9V Battery
Type : Electret Condenser.
Dimensions : 185 x 27 x 38mm
Weight: 160 grams
Cat. A 10450 .. ... .... ... .. .... . $19.95
$69.95
• Requires no crossover and
handles up to 1OOW!
• Sensitivity : 100dBI0 .5m
RS232 GENDER
CHANGERS
~tJ~ifo'f~~ns~~ Jfnfi~:cT~ matt
$119.95
. $11.95
SUPER HORN TWEETER
Built around a heavy duty heatsink
this unit features the latest transistor
A16160
$9.95
$11 .95
10A STEP DOWN
CONVERTER DC-DC
SPECIFICATIONS:
Input Voltage : 24V DC
Output Voltage: 13·8V DC
Primary Cunent : 11A (24V input,
10A output)
Output Current: 8 Amp continuous
rated (12Amax .)
Size: 125(W) x 50(H) x 175(0)mm
Weight: 900 grams
P10947
$7.95
• Requires no power source.
M23521
$99.95
black .
2WAY60WATT
CROSSOVER NETWORK
• Fitted with DB25S socket. (RS232)
• Anodised aluminium plate.
• Includes mounting hardware.
• 12dB attenuation
• Cross over point 2,300 Hz
• Impedance 8 ohms
==r~J~=.sbatterysizes
Ou~itu:fi:!ent : 4 Amp continuous
rated (5·5A max .J
Size : 125(W) x SO(H) x 90(D)mm
Weight: 450 grams
A16155
DB25SOCKET
WALL PLATE
$4.95
MIDRANGE HORNS
SUPER DELUXE
BATTERY CHARGER
~ ✓1P~~
BUIit around a heavy duty heatsmk
this umt features the latest transistor
1
~r!t8tfo ftenS~8~
matt
black with a unique mounting bracket
makes it the best in its class.
Cat.A16001
3WAY60WATT
CROSSOVER NETWORK
S21.50
• Ideal for holding components. and
other small/light objects .
2WAY60WATT
CROSSOVER NETWORK
Cat.A16003
A10031 (10 discs) $12.95
A10032 (20 discs) $19.95
$18.95
$9.95
3WAY60WATT
CROSSOVER NETWORK
• Holds 10120 compact discs in Iheir
cases
• lnterlockillQ modular design
allows vertical and horizontal
interlocking
• Discs slide into place horizontally
making lilies easy to read.
• Wall mount or free standing .
$17.95
P10940
• 6d8 attenuation
•Crossover point SOO and 5,000 Hz
• Impedance 8 ohms
COMPACT DISC
STORAGE UNITS
$3.20
• Fitted with 5 pin DIN socket.
• Anodised aluminium plate.
• Includes mounting hard•Yare .
• 6dB attenuation
• Crossover point 5,000 Hz
• Impedance 8 ohms
Cat.A16002
$69.95
Designed for car burglar alarm backup battery. Allows the back-up battery
to be charged from the car battery
and isolates the back-up battery by
not allowing the back-up battery to
drain back to the car battery
A 12095
A 10011
~~ena~,~;";!~Tir:~£~~:r~:c!sn~
lamps, and the like that threaten the
~ormance and shorten equipment
hie of unprotected electronic
components.
SPECIFICATIONS :
Electrical rating : 220·260 volts
(AC) SOHz 10 Amp
Splke/AFI Protection: 4 ,500 amps
for 20m/second pulses .
Maximum clamping voltage: 275V
differential mode.
CAR BATTERY ISOLATOR
HORWOOD MET AL
INSTRUMENT CASES
(SQUARE HANDLES)
Enables a portable CD player or
portable TV to be played through any
car speaker system by using the cars
cassette player. Reduces the risk of
thett. Just plug in when required , and
remove when you are finished. Hard
wiring not needed .
Crossovers are essential for
multiway speaker systems, otherwise
your bass will be ~egraded by inter•
modulation distortion and cone
break up, and your treble will be
distorted by bass components.
These c:-ossovers are designed to
channel only the frequencies that
each driver can properly handle.
Read the specifications to choose
the correcl one for your need .
FREE STANDING, FOLD
UP MAGNIFIER
An ecconomically priced " hands free "'
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: i~~d~i:;s~M$ 3kHz-30kHz
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,.JE
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Low dual cone, wide range .
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........ Cat.C12000
1·9
10+
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RS232 WIRING
ADAPTOR BOX
•
•
•
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Male to female
25 (?etachable plug on leads
2 mini jumpers
Ideal for experimenting or
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DUAL TRACKING 18·5V
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Cat.K41630 .....................
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.............. ,,, .. ,,, .. ,, $22.95
l~e~ta:;g~(~r~~~,,~ters audio
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THE SCREECHER
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Here is a low cost car alarm
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(86a19, EA August ·a6)
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HANDS-FREE
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Here's a hands-free telephone that
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MUSICOLOR IV
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• ~~~a~f;~~rs with LED status
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MUSICOLOR IV
Add excitement to parties, card
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AUDIO TEST UNIT KIT
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(81A010) (EAOct '81 )
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The RIE ktt lncludea a 1uperb
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$134
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This simple project is suitable for
1
:o~:t;~/~~~J:~¥~~g~f;r~! •
(ETI 581 , June '76)
Cal . K45810 .. .... .. .. .... .... .
$34.95
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LOW-COST BIPOLAR
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Add excitement to parties, card
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Musicolor IV llght show. This is the
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Cat.K81080 .................
$29.95
Have you ever desotdered a suspect
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Handy Tester. (EA Sept .'83) 83TT8
Cal. K83080 ....... Normally $18.95
tf~s t~~~bYi~~~~f~!~~=~~orde(s
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MUSICOLOUR IV
~fe
When your camera's ltashijun fires,
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Cat. K86081 ... ................
TRANSISTOR TESTER
$99.95
~~sAe~!b.!i~u~gic2
Cat. K84020 .
$9.95
Updated from the EA March 'BO
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1W AUDIO AMPLIFIER KIT
A low-cost ~eneral-purpose.1 watt
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Cat. K84111 ....... ....... .....
$39.95
Here is a simple model train control
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Cat. K80120
$39.95
ELECTROSTATIC
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It's called electrostatic hazard and if
!~~~~~~r;!~?C ~~~:~~~il~:;;~t~~~
the poor device is never likely to be
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Cat. K41730 ... ...... .........
$54.95
READY-SET-GO LIGHTS
A simple project for starting slot car
~;ci~~~::&;:~::~rse~r::ional
random delay between the amber
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$24.95
EA AM STEREO
DECODER
AM stereo is now broadcast in
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This add-on decoder wori<s with the
Motorola C-QUAM system.
(EAOct.'84) 84M510
Cat. K84100 ...... Normally $26.95
SPECIAL, $16.95
CRYSTAL CONTROLLED
TV PATTERN GENERATOR
ZENER TESTER
LEb~u~du~~~~!~· ~~~~:lso check
(ETI May'83) ETI 164
Cat. K41640 ............. .... ..
$11.95
~i!~eo'K.rt~
:t,
~~ELAIDE
NOTE : (tr1ces may vary 1111ersta1e due to
lreigh1COSIS)
MAIL ORDER,
Local Orders: (03) 543 7877
Interstate Orders: (008) 33 5757
All Inquiries: (03) 543 7877
CORRESPONDENCE,
P.O. Box 620, CLAYTON 3168
Telex: AA 151938
Fax, (03) 543 2648
-
MAIL ORDER HOTLINE
008 335757
fTOLLFREEJ
/STRICTLY ORDERS ONLY)
Cat.
A simple low cost add-on for your
multimeter. This checks zeners and
reads out the zener voltage directly
Rod Irving Electronics
MELBOURNE: 48 A'Beckett St.
Phone (03) 663 6151
NORTHCOTE, 425 High St.
Phone (03) 489 8866
CLAYTON: 56 Renver Rd.
Phone (03) 543 7877
SOUTH AUSTRALIA,
Electronic Discounters P/L,
Anyone wishing to obtain the
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Errors and omissions excepted.
Prices and specifications subject to
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;~=~!:~~';{;d tradmarks ol thew
■EEZ
THE WAY I SEE IT
By NEVILLE WILLIAMS
Fly by wire: is it safe from
electromagnetic interference?
Future aircraft, ships, trains and road vehicles are
likely to be guided and controlled by electronic
rather than mechanical means. But while electronic
systems may be reliable in themselves, it has yet to
be shown that they can be fully protected from
electromagnetic interference.
We know what can happen if the
brakes fail or the steering linkage
comes adrift in a present-day
tourist bus. It can easily end up in
the creek at the bottom of the hill! A
similar fate could befall its future
electronically controlled counterpart if the data circuits from the
driver's cab to the road wheels
were to be corrupted by a chance
signal from a high-power mobile
transmitter in the adjacent traffic
lane.
There is certainly no lack of
precedent for accidental transmitter or other electromagnetic
breakthrough into all sorts of electronic equipment, from radio
receivers to radio telescopes. Ask
any design engineer or service
technician who's been around for a
while; it's something that they have
always had to live with!
The question is not so much why
interference should be a potential
problem with electronic control
systems but why it should not be,
based on a mass of past experience!
The vital difference is that
whereas to date, electromagnetic
breakthrough has merely been embarrassing, frustrating or mildly
expensive, it is much more serious
36
SILICON CHIP
when the lives of passengers are
directly involved.
Fly-by-wire concept
In aircraft, electronic control or
the so-called "fly by wire" concept
has been around for some time but I
first encountered it in 1984, when
researching an article on Australia's then-new FA-18 Hornet attack fighter. Up until then, I must
confess, the term fly-by-wire seemed to relate more to the woven steel
cables strung from the cockpits to
the control surfaces of ancient
biplanes the cables that
helmeted pilots religiously checked
before take-off.
In the present context, and certainly as applied to the FA-18, the
word "wire" has to do with control
circuits. These take over from the
usual mechanical or hydraulic
links, conveying encoded instructions from the cockpit to the flight
computers and thence to actuators
coupled to the various control
mechanisms throughout the plane.
The computers process and execute instructions from the pilot
while optimising - or configuring
- the plane for take-off, landing, or
J:!Ormal flight, taking into account
the constantly changing fuel/
weapons load. Being connected also
to strain gauges and other status indicators, they can intervene to protect the airframe from excessive
forces, unless deliberately overridden by the pilot to cope with
emergencies.
Like a super "George" (auto
pilot) the flight control computers
can be programmed to relieve the
pilot (or crew) of routine tasks, freeing them for activities which call
for intuitive human reaction - a
major requirement in a combat aircraft as complex as the FA-18.
Indeed, in more radical military
designs, where aerodynamic
stability has been deliberately
sacrificed for sheer get-up-and-go
performance, the planes are
reputed to be virtually unflyable
without constant computer monitoring and intervention.
The bottom line is that the
desired end result can be achieved
much more efficiently with a
dedicated all-electronic control
system, than by attaching separate
electronic modules to otherwise
conventional mechanical and
hydraulic linkages. The allelectronic fly-by-wire approach is
lighter, more accessible for
automated system checking, and
capable of higher redundancy to
cope with possible airframe
damage, especially in combat
aircraft.
Passenger, cargo planes
Modern airliners like the new
A-320 Airbus are also being designed around fly-by-wire technology
but with emphasis on operational
The Switch to UHF TV On the NSW South Coast
My perception of the Australian
radio/TV broadcast scene was
recently altered by a couple of
weeks spent holidaying on the
NSW mid-north coast. The winter
days were pleasantly mild but
whatever else the area may have
going for it, a surfeit of broadcast
entertainment is certainly not one
of them.
Back in Sydney, most residents
have access to five local TV stations, eight AM-stereo radio stations and about as twice as many
FM stations, if one includes the
community broadcasters. At most
times, if one wants to look or
listen, there's a reasonable chance
of finding something to fit the
mood.
But in the unit where I was staying, despite a newly installed
antenna/booster system, only two
worthwhile TV signals were
available - from the ABC and a
regional commercial station.
As for radio, the score was the
noise-free ABC regional transmitter on the FM band and on AM,
Radio National from the ABC, plus
the local commercial broadcaster
and an assortment of other signals
that were only just listenable.
In that short list, the role of the
economy, reduced crew requirements and detailed monitoring
of the flight envelope, both to assist
pilots and to counteract possible errors of human judgment.
According to news reports, one
of the demonstration routines for
the new A-320 Airbus has been a
low-level fly-over at reduced speed
and in such an attitude as to be inadvisable, if not hazardous, under
ordinary manual control.
It therefore came as quite a
shock when a brand new A-320
recently crashed in full view of
spectators. It was apparently performing just such a manoeuvre an event that gave rise to speculation that the flight computer system
may have "crashed" a few critical
seconds before the plane it was
controlling!
The item concerned the plight of
a small group of viewers in the
southern highlands of NSW, who
would be affected by the pending
re-deployment of TV stations in the
adjoining lllawarra area of NSW
from their present VHF channels to
UHF - to make room for new FM
radio services.
Preliminary tests had indicated
that the UHF signals might not
reach this and other small communities that were currently able
to receive the VHF transmissions.
Naturally, the residents were
upset.
Admittedly, the DOTC is planning to explore some of these problems before the VHF transmitters
are actually switched off but how
isolated small communities will fare
in the all-UHF era is the subject of
assurances rather than guarantees.
What I found disturbing in the admittedly off-the-cuff TV interview
was the facile dismissal of the
viewers'objections:
(1 ). They were fringe viewers
who'd been lucky enough to
receive useable signals from the
VHF transmitters. They might not
be so lucky with the UHF service.
(2). The government has made
other provisions for fringe viewers.
All they need to do is to install a
dish and pick up services direct
from the satellite.
Not surprisingly, the viewers
concerned were unimpressed by
the idea of having to spend
$2500-odd to receive fewer TV
services than at present - the
ABC and SBS only.
While the DOTC has a job to do,
it is to be hoped that they will be no
less keen to advise and assist the
disadvantaged as they may be to
"pull the plug" on the VHF services by the due date. I support in
principle more intelligent long-term .
use of the VHF/UHF bands. But
the need for a full complement of
FM radio broadcasters is not so
urgent that TV fringe viewers need
to be summarily disadvantaged.
The matter may possibly have
been clarified before you get to
read this but in the meantime, I was
intrigued by further speculation
that radar blips or other powerful
radio signals may have corrupted
the plane's control logic at a
critical moment.
Such an eventuality was named
as the most likely reason for the
puzzling crash of a West German
fly-by-wire Tornado fighter in 1984,
killing both crew members. They
certainly appeared to have ignored
warnings to keep well clear of
ultra-powerful radio transmitters
near Munich carrying transmissions for the "Voice of America"
and "Radio Free Europe".
It is true that both military and
commercial aircraft carry communications and radar transmit-
ters, some delivering quite high RF
output. It can also be assumed that
precautions would have been taken
at the design stage against possible
breakthrough into the flight control
system from these sources.
It does not follow, however, that
filtering, shielding and isolation
from identified potential inter£erence will guarantee ,immunity
at all times, from other external
sources of a different frequency,
spectral content and power level whether unintentional or deliberately hostile.
Just consider the following:
• Interconnecting leads can act
as receiving antennas, especially at
frequencies to which they happen
to be electronically resonant.
• The growing use of plastics
rather than metal in aircraft con-
ABC is crucial and as if to emphasise the point, chairman David
Hill chose that same period to announce plans to provide additional
program services in the area.
His positive note was in sharp
contrast to the attitude of a staff
member of DOTC (Department of
Transport & Communications) who
had been quoted in a TV news item
a few days previously.
OCT0BER 1988
37
THE WAY I SEEIT-CTD
struction may cause on-board wiring to be less effectively shielded.
• While much more compact and
efficient, solid-state equipment is
relatively vulnerable to high level
electromagnetic radiation - suggested as a reason why some Russian combat aircraft are reputed to
use valves for critical functions.
Problem that won't go away
After many years in the business,
I have no illusions about the persistent and intrusive nature of unwanted interference affecting electrical signals. As already suggested, it has always been with us
in one form or another. I find it difficult to believe that it will suddenly
and obligingly disappear from the
present scene.
In the 1920s and 1930s, when
half the fun of radio was in logging
weak and distant stations, we had
to battle daily with atmospheric
and man-made "snap, crackle and
pop"! Oh yes and with
heterodyne whistles from other
listeners' regenerative detectors.
In the 1940s and 1950s, with a
rising emphasis on car radios and
mobile 2-way equipment, we had to
deal with vibrator hash, silence the
ignition of the host vehicle, and put
up with the invisible cocoon of interference that surrounded many
other vehicles on the road. For good
measure, rural vibrator-powered
receivers involved a parallel set of
problems.
The preoccupation with television in the 1960s and 1970s exposed the pattern of harmonics being
radiated by most old-style amateur
transmitters, while the CB radio
boom, which followed, emphasised
the vulnerability of contemporary
consumer equipment generally to
nearby radio frequency emissions.
In Britain, for example, official
complaints about interference from
CB radio transceivers averaged
several thousand per month during
1981/82!
More recently, computer and
other digital equipment has added a
further dimension to the conflict
between wanted signals, "dirty"
power lines, and the complex clutter of extraneous electromagnetic
radiations which is poised to corrupt the flow of encoded information.
This leads to further observations:
• Digital equipment can itself be a
frequent source of interference.
• Some CD players radiate
enough RF to noticeably desensitise the associated FM tuner in
a hifi system.
• Sydney airport radar caused
major hassles for engineers when
setting up the UHF TV relay channels in Kings Cross.
• A Sydney sound studio recently
encountered serious hash problems
from newly installed switchmode
power supplies.
• People fitted with heart
pacemakers are warned against
certain environments which might
affect the electronics.
• Lightning strikes or near misses
are still a fact of life, as pointed out
in "Serviceman's Log" (August
1988, page 31).
It's all a matter of EMC
In European technical parlance,
if not elsewhere, discussion of such
problems is commonly lumped
under the heading "EMC". This is
short for electromagnetic compatibility, or the compatibility of
particular technologies and/or
items of equipment with the overall
electromagnetic environment. It involves both sides of the equation:
(1). The ability of electrical or
electronic equipment to operate
efficiently without needlessly
polluting the already cluttered electromagnetic environment. (Strictly
speaking, even a clinically clean
transmitter complicates the environment by emitting yet another
signal).
(2). The ability of electronic
equipment to function normally,
unaffected by extraneous electromagnetic energy, natural or
man-made - a critical consideration in the present context.
Despite countless discussions
and conferences over the years, at
national and international levels, it
is doubtful whether governments
and industry have handled electromagnetic compatibility any more
deftly than other major environmental issues.
Historically, we've tended to put
up with RF interference problems
- output and input - until they've
become utterly intolerable and even
then, settled for corrective
measures that didn't involve dipping too deeply into the too hard
basket!
Rather than tackle spurious emissions head-on, it's been easier to
maintain the S/N ratio by progressively upping the power of
transmitters around the world,
thereby complicating the electromagnetic environment in another way.
As mentioned in the August
issue, it took decades for the
Australian Government (and
others) to give their inspectors effective control over RF sources
other than regulation transmitters.
In Europe, the EEC group is at odds
over standards, with full legal implementation still two or three
years away.
Wise after/before the event?
If there's one lesson to be learned
from contemporary environmental
debate, it's that we tend to barge
ahead on the basis of present need
(or fad) only to later concede that
more consideration should have
Any new technology certainly hos to be
a lot better than what was aboard the Tornado
fighter that crashed in Germany in 1984.
38
SILICON CHIP
'Problems?
... and you
don't have our
I20page
catalogue . ..
Modern fighter aircraft use fly-by-wire technology but is it sufficiently
developed for civilian passenger aircraft?
been given to the consequences of
so doing.
It's easy enough to be perceptive
after the event, but ever so much
harder to correct the situation
when the damage has been done.
Now - not later - is the time to
debate this whole fly-drive-ride by
wire push. Does it represent real
progress or the use of high
technology for the s.ake of commercial exploitation?
It may seem utterly presumptuous for a mere technical columnist in a magazine to query the judgment or the motives of the world
aircraft industry or, in longer term,
the manufacturers of ships, trains
and road vehicles. But in effect, the
question boils down to this:
• Have electronic engineers
associated with those industries
really overcome, once and for all,
the perennial problem of electromagnetic interference?
• Can they guarantee that their
electronic control circuits are totally proof against penetration and
corruption by all conceivable extraneous sources of electro-magnetic radiation?
• Assuming that reality falls
somewhat short of perfection, can
they be confident that a functional
all-electronic control system can be
at least as reliable as the most proven conventional methods?
Any new technology certainly
has to be a lot better than what was
aboard the ill-fated Tornado fighter
in 1984. The mere fact that the
crew had been warned to keep
away from the Munich transmitters
indicates that the control equipment was known to be vulnerable to
high-level electromagnetic radiation.
In terms of EMC - electromagnetic compatibility - how
much better is the equipment
aboi:trd the FA-18, the A-320 and
other comparable aircraft in 1988?
Drive-by-wire cars?
If it is appropriate to speculate
about aircraft which are technologically up front in terms of
design, production standards and
maintenance, what is the likely
position in relation to road vehicles
and, in particular, to the ordinary
family car? How compatible will
it/they be in an increasingly cluttered electronic environment,
especially after encounters with
some of our local "she'll-be-rightmate" mechanics?
In considering this subject, it certainly isn't reassuring to read
reports in overseas journals of
obscure malfunctions in vehicle
cruise and engine management
systems, which appeared to be due
to electromagnetic interference.
Those would be annoying,
frustrating, perhaps expensive but
a similar malfunction directly affecting control of the vehicle could
be disastrous. Best we ask the questions now, rather than wait until
we're behind the wheel!
A promising way of "hardening"
communications and control equipment (reducing its vulnerability
both to the electromagnetic environment and to deliberate zapping) would be to replace the
"wires" with optical fibres. Maybe
we should shift the emphasis to
flying-riding-driving by glass!
~
At last . ..
a TRADE
catalogue for
the consumer
ARISTA ... your one-stop problem
solver. Video plugs and sockets ...
Video extension speakers . . . Video
flyleads ... Video RF interference
filters .. . Video splitters ... Indoor
antennas ... Video switching units
. . . Down convertors . . . Video
speaker controllers . . . Video
camera lights . .. Video tape
rewinders ... Video cine adaptors
. . . Video head cleaners . . . Video
splicing kits . . . Video storage
cases ... Video dust covers . ..
Video leads .. . Searl plug leads
... Video dubbing kits .. . Video
headphones . . . Video shotgun and
wireless microphone systems . . .
Pre-amplifiers with video inputs .. .
Video camera stands . . .
Just about anything
you want.
... Try us ... NOW!
Get your catalogue FREE
from your local ARISTA
dealer or send $2.50 P&H
and your return address to:
ARISTI\.
ELECTRONICS PTY LTD
PO BOX 191, LIDCOMBE, NSW 2141
OCTOBER 1988
39
,--------------------------------,
I
I
Why Waste Your time With Other Suppliers
Altronics Can Deliver Any Of The Quality Products
To
You Tomorrow - Just Phone Your Order Toll Free
1
I J kO' D
On 008 999 007
I a~/ Direit~~e II
Country Clients Please Allow Additional 48-72 Hours
I
I
1
I
I
~---------------------------------
Microprocessor Controlled Detector
Clips On To Sunvlsor
Invisible from outside your vehlcle - this lantHtlc high apec Radar
Detector Detects X and K Band Radar up to an Amazing 13KM
This super compact "Sunvisor clip on" Microeye Detector is virtually
invisible from the outside of most vehicles at normal eye heiaht hence its
very unlikely yours would attract the attention of a thief (or the
Gendarmes for that matter) However, please remember that use of Radar
Detectors is not permitted in some states.
MICRO EYE VECTOR
The First Detector With GaAs Diodes
DC Brushless Fan
120MMx120MMx38MM
Brush less,
Electronically
Commuted DC Motor
Voltage
24V DC
Current
330mA
Speed
3100 RPM
Air Flow
23 C.F.M.
Noln Level
32 dbA
Until now, GaAs diodes have only been used in I sophisticated military
radar equipment. The Microeye Vector is the first consumer electronics
product equipped with this new technology.
Why GaAa Diodes Make The Difference
• Lower threshold allows for a better signal to noise ratio • Lower signal
conversion loss • Higher barrier reduces noise. Quite simply GaAs
diodes increase the sensitivity of the Microeye Vector.•Using the latest
digital processing technology the unit will filter out and ignore emissions
from 80% of poorly designed Radar Detectors that emit microwaves. •
Simply plugs into your cigarette lighter socket. • Clips onto sunvisor •
Detects Mobile Radar Equipment. • Highway/ City Modes switch allows
monitoring of City or Highway conditions.
Normally $29.98
This Month
S24 .DO
F 1040
6 or More $20 ••
Ultra High Power Capacity
Polypropylene Ba•• Drivers
Save 25% This Month
12" (300mm ) Model
100 Watts continuous input
150 Watts intermittent input
Impedance 8 Ohm
Sensitivity 93db
Weight 3620gm
9
9
$
s4 9 9
C 3070
Normally S139
Acceaaorles
Included:- Visor
bracket • Velcro
• Cigarette lighter
plug.
21 Day Money
Back Guarantee.
1 5 " (375 mm) Mode l
!~=~~~i~:~J~~nt input
412
Normally
High Performance ALC Wireless
Microphone
Our incredible ALC Mic is
• Cardiod -Uni Directional Pick-up
pattern• Freq.Res.: 30Hz-15KHz
• carrier Frequency .Adjust Range:
8 1
one of the most exciting
products for '88. Wireless
Mics suffer from overmodulation distortion with too
higher input sound level making them unsuitable for high
grade vocal entertainment
use of ALC (Automatic Level
compressor) fixes all this.
w
~:~;,;;·$1~;:~,,s:;~;i;; ~:1: S99 .00
Super Bargain Save $50
Fantastic Negative Ion Generator
There have been volumes written about the benefits of negative ions
combating air pollution, cigarette smoke etc. can be very beneficial to
Asthma sufferers. Our great little Rover generates billions of ions per
second! Includes tester.
W
120 Watts continuous input
~g;075
$17; elght
$
j
111\\1
149
/ii
~filfi f~l~~~:~~<at>r~~E.I~lI
quick stocks are limited.
These are the Genuine Grain Oriented Toroid Transformers
as un d In Electronic Australia Protects
Toroidal Power
Transformers
Why • Torold?
• Smaller size and weight to meet modern
"Slimline" requirements.
• Low electrically induced noise den,anded
by compact equipment.
• High efficiency enabling conservative
rating whilst maintaining size
advantages.
• Lower operating temperature.
• Simple , quick single boll mounting
Dimensions and Weight
180 VA Model• 110 Diam . 45mm
H. 1.8Kgs Lead s 200mm
300 VA Model• 125 Diam . 45mm
H. 25Kgs Leads 200mm
160 Watt Models 300 Watt Models!
S65
A 0990
s29
=,.'. ~
10 up
cat.No.
S62 ea
SEC.V
M 3050
M 3055
M 3060
12 + 12
18 + 18
25 + 25
~;g
!tS
$79
Cat.No.
M 3085
M 3086
M 3088
~~~
10 up
$75 ea
SEC.V
12 + 12
18 + 18
25 + 25
!g:~
,;}{
~~~:~==
:: ; · :· tl■lr}_· ; 1111: I:;··•· :·::: ···. -··•· ··.·Jtr ·\·> ·•·•···•·•·· ·· ;: ·=·:·r <X .·: r·.•.··.,- · • · ❖
~
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A Great New Product From Altronics For '88
The Fantastic Pin Point Ultrasonic Cleaner
' ~<at>
c\ofs,
conne
""?u\ef ~e\a'/s,;...ucn
co••: nes,
"o ,..
c,ean 5'l-l1\c ses a
ce•s, G,as
? 'l-le\\e{'/ \e\
Je n t1'o
t1'1JC
Design Award Winner
Awarded the Good Product Design Award for CETDC in 1987. This
fantastic Ultrasonic cleaner can earn its cost a hundred times over in
cleaning Computer Connectors, PCB's, Switches, Relays, Jewellery,
Glasses, Watches etc.
How Does It Work?
The Pin Point Ultrasonic Cleaner uses a transducer generator to
produce millions of activated microscopic cleansing bubbles, which·
blow dirt, grease & grime off surfaces, and deep into cracks and holes.
This personal ultrasonic cleaner won't scratch precious jewellery or
glass. Comparison studies made by hospitals, commercial businesses
and industry show ultrasonic cleaning proves better and safer than a,ny
conventional method.
But don't take our word for it. Test the Pin Point Ultrasonic cleaner
yourself . Pop your dirty watches , glasses, connectors etc. into the
cleaners stainless steel basin, add a cup of tap water, and three minutes
later see the difference. The results are instantly revealing .
SPECIFICATIO NS
Power Supply : 240V 50Hz Power Consumption : 300mA Frequency :
40 +/-2KHz Dimensions : 224 x 114 x 124mm Capeclty: 570ml
Weight : 1kg Body Materlal: ABS Plastic Tank Materlal : Stainless
Steel (SUS 304) On/Off: 3 Minute Auto Timer.
••••••
I
Amazing Price Breakthrough
*
RF Signal Generator
Great Saving On
#·i:C•l*l#hil◄ •! 1 1013 ·
Quality
Solderless
Breadboards
Frequency Counter Sensation
150MHz Frequency
Counter
A frequency counter is invaluable for
the accurate alignment and testing of
many modern electronic circuits.
is a winner.
SPECIFICATIONS:
Frequency Range: 100k - 150MHz in
6 ranges RF output level 1OOmV RMS
Accuracy +/-3% Modulatlon: Internal
(30% depth) - 1KHz• External - 50Hz
- 20KHz • Crystal Locked Oscillator '
NOW
SPECIFICATIONS:
Freq.Range: 10Kz - 150MHz
Gate Time 1 sec. 6sec. Accuracy +/-1
count Max.Input 20V P- P Sensitivity:
• 10Hz - 30MHz - 25mv-100mV
• 10MHz - 150MHz - 100mV - 300
• Power requirement-9V DC at 100mA
S199
a 1520
S18O.00
Stop Data Crashes And Corrupted Software
"Squeeky Clean" Mains FIiters
An investment in one of our fantastic 'Squeaky Clean ' Mains Filters
could save you a small fortune with your computer system.Protects
Hardware end Software from mains voltage spikes caused by
lighting, transmitters, electric motors, welding, machinery etc.
Anyone who has to re-build 3 weeks of software programming will
cherish the aquisition of one of these fine mains filters .
Energy Authority Approved .
P 8160 4 Outlets
Each individually filtered. A
must for 'serious' computer
installations e.g. for Schools,
Business etc. • Loading
Rating: Continuous 10 amps,
with circuit breaker at 240V
P 8150 Slngle FIitered
AC . • Outlets: 4 GPO's
Double Outlet Model
individually filtered.
Just the shot for home
computer or for individually
located peripherals e.g . remote
printer, computer terminal etc.
Loading Rating: 10 Amps Max.
load at 240V AC • Outlets: 2
GPO 's single filtered .
$269
640 Holes
P 1005
$12.50
640 + 100 Holes
P 1007
$14.50
640 + 200 Holes
P 1009
$16.95
400 + 1280 Holes
Accepts up to 16 x 16 pin OIL
IC's Terminals for PS
Connections.
P 1012
$43.50
SOO +1920 Holes
Accepts up to 24 x 16 pin OIL
IC's Metal Back ing Plate for
Shielding of sensitive
circuitry.
P 1015
$65.00
High Definition
Computer Monitor
Superb "Goldstar Pro" Non glare
naturally, & screen character
resolution well worthy of mating
up with top end personal or professional computers.
• Compatable with IBM, Apple,
Commodore Computers
• Excellent for small business
applications • Exceptionally
clear & stable display • 80
characters 25 lines display.
CDT Non glare phosphor P31 green
Input composite video 1V P-P Input
Conn . RCA Jack Input Imped. 75
Ohms or high imped. (switchable)
Video Bandwidth 18MHz Horlz.
Reaolutlon 900 lines at centre
external control• brightness contrast
129
Now s
.DO
D 1115 Amber Screen
-~·:·;,~ . : t ~ ~ ; , - :.
Great Kit Projects To Build
Many Just Released For 1988
Ja~k/~~~~t~ell
Brllllant Performance Stereo Pre Amp
111111111 :::
Universal High Power
Amplifier Module
(See SC Dec'87)
?}W. }
J ! Ft
:::•1:::
] ii
Studio 200 Stereo Control Unit
(Slllcon Chip June/July'88)
Out-Performs Commercial Units Costing $600 Plus
:::•••1
::::::a::::
11
The Studi·o 200 Stereo Control Unit is companion to the studio 200
stereo power amplifier (or other power amps). It features slim single
unit rackmount profile, treble, bass, balance, input selector, tape
monitor switch, stereo/ mono switch and volume control. Inputs
include phono, tuner, CD, VCR and tape loop.
I! I
K5015
:1: 11:• 1
s229
High power rugged reliable design featuring
low distortion and inbuilt speaker protection
All components, including output transistors mount on a single PCB. Suitable for
high quality guitar amp, public address or in a
high fidelity stereo amplifier. Kit includes
angled heatsink bracket, main heatsink and
unlike other kit suppliers, the in-built Poly-,
switch for loudspeaker protection.
General Purpose Pre-Amp
This unit contains· all necessary
components to complete:- • A Phone
Pre-Amp with RIAA freq. response•
A tape Pre-amp with NAB response •
A microphone Pre-amp with either 40
55 or 80db of gain.• Or a Pre-amp for
just about anything!
Power 10-40V DC High 100db Ripple
I:I
i•l lil i
Jro;.I
Rejectio~
::::::::::::or,
s18.so
5510
1,,..
j/1,
db/
}/ 0.{
:::::::=::,Q =::
Active Direct
lniectlon Box
itii
JI
Ellmlnates Annoying Hum Pick up}
(!tee EA Oct'87)
,:,:,:,:::::w i
t fai:
J\i\i; i
:••··••:•1
\ 0.
\It
Calling A!I Audio Purists
K 5010
This : ; : ~ ~ ; ; ; ; ; : ;,;~ic;~~h; ~s. ; ;r You
5399
Per Channel Power Ampllfler
.,.,_.,_::=
_'_,_,_•••
:,_:,•.
""'
: ar
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•_9.:1
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-
Featurea: • In-Built speaker protection• Toroidal Transformer
(low hum)• Black Satin Finish • Low leakage power supply capacitors
• Housed in Rugged Custom Chassis.
Specifications: • Output Power 100W into 8 Ohms Freq. Res.(at 1W)
20Hz-50KHz + or - ldb Input Sensitivity 870mV Harmonic Distortion
(20Hz-20KHz) 0.1% Slgnal To Noise Ratio 100db or Better Protection
5A fuses plus RDE245A Polyswitch Damping Factor (without
K
5550
$
45 .00
H' h E
I ltl
S t
lg (S~:~ff1l on %~Ip ~.ny'88)ys em
_P_o_1_ys_w_i_tc_h_e_s_)_1o_o_<w_i_th_P_o1_y_sw-itc_h_e_s_J_10_0_._s_ta_b_1_111_y_u_n_c_o_n_d_it-io_n_a_1._--,,f
II•II
,Jj( \
1:•: :1 ::::
I
Extend~ the life of plugs
Dlscollte
(See SIiicon. Chip July/Aug'88)
Add Some Colour To Your Next Party
[~I~t~~~~~;:: 1i
electric guitar pickups,
-:
synthesizer etc. to low level
balanced outputs to be fed
over long lines.
Features: Professionally
screen printed • Earth isolate
·:
switch • 15db pad • Phantom ;:::;:: :,:•·
powering plus internal 9V bat. )C::
& points, increases
power & improves fuel
economy. Suits 4,6 & 8
cylinder engines. Install
one into your car & start
saving $$$ from the very
first day.
K 4015
s43.so
: :• m111•11e::1g11F::11&1:: : n1:1m1:1m~:::::::: ~:;:;~•1~::'.:~ ~::;::
The Screecher
Car Alarm
(See EA Aug'86)
Ear Splitting
110clb Modulated Tone
K 4360
s39 .95
Now our top selling car Alarm. Two
Sensor inputs-Normally open and
normally closed enable,simple
connection to door, bonnet, Boot
light, switches etc.
The Protector Car Alarm
(Slllcon Chip Feb'88)
Save Over $100 On An
Equivalent Commercial
System
Feature•: Internal & External Sirens
• Dash lamp flasher • Battery back
- - - - - - - - - - - - - - - - - - - - - - - - - - - • • up• Delayed .& Non delayed inputs•
Ignition killer• Easy to build & install.
sa-we $SS \
\he co•
o"cornrnerc\al
ol
1ua\eo\l
(See EA Mag.Jan '85l
eQU •
Super Low Price on Famous
EA 8 Sector Alarm Svstem Kit
FHIUrN:
• Alarm has 8 separate input circuits - 8 sectors
can be monitored independently.
• Each input circuit is provided with an
indicator LED and a sector On/Off switch.
• Individual sector isolation allows the user to
have some areas of the premises habited
while others remain protected e.g. Inside
Off/Outside On .
• Inputs accept both normally closed and
normally open sensors.
• Two inputs provided with an entry delay
between 10-75 seconds) .
Internal t,ip warning buuer-alerts owner/
occupant of pending alarm operation- .
great for the " forgetful " amoungst us. This
buzzer is pre-settable between 5 and 55
seconds prior to Alarm.
• Unique circuit detects automatically when
any N/ O or N/ C loops are either open circuit
or dead short. • ·II· eomeone trying to bridge
Bench Top
Power Supply
3-30V to 1 amp Max.with
variable current llmlt
FEATURES:
• Output 3 to 30V at 1A • Short circuit
protected • Load switching• Current limiting . Dual scale meter• Housed in our
Delu xe " ABS " instrument case .
SPECIFICATIONS:
• Output Voltage - 3 to 30V • Output
Current - 0 to 1 amp (fully variable)• Load
Regulat ion - Better than 0.2% from Oto full
load • Output Ripple-Less than 2mV RMS.
KIT
K 3210
rHd awltch .. etc.
• Switched output can be used to sand a silent
alarm through an auto-dialler circuit or
similar.
K 1900
S 5065
149.50
(without Back Up Battery)
KIT $
(12V 1.2AH Backup Battery) Now Only
24V To 12V DC
$15.00
Converter
(Slllcon Chip Dec'87)
Laboratory
Power Supply
Enables 12V appliances like
stereos, 2 way radios, CB's etc . to
operate from a 24V battery.
• Operates from 18V-30V. Output is
13.6V at 5 amps.
KIT
K 3255
-f
59 .OD
K3300
3-5 Volt• at up to 5 Amp•
$
195
Designed by Electronics Australi~. this supply has been one of our most popular
kits. Our version incorporates refinements and 1s now housed 1n an attractive,
tough " ABS" instrument case. This all new compact version has been made
possible by the use of a highefficiency Toroid Power Transformer. So you win I.our
ways - less heat, less weight - Greatly enhanced appearance and easier to build Remember the Altronlca Kit 11 fully drHled and punched.
Manufacturers, Contractors and Bulk Users
Please Contact Our Wholesale Sales Dept.
Sydney (NSW Only) Colin Fobister 436 0422
Perth
09 328 2199
174 Roe St. Perth W.A. 6000
PHONE TOLL FREE 008 999 007
Perth Metro & After Hours (09) 328 1599
ALL MAIL ORDERS
P.O. Box 8350 Perth Mail Exchange W.A.6000
AL TRONICS RESELLERS
Chances are there is an Altronics Reseller right near you - check this list or phone us for
details of the nearest dealer. PIHH Note: Resellers have to pay the cost of freight and
insurance and therefore the prices charged by Individual Dealers may vary slightly
from this Catalogue - in many cases, however, Dealer prices will still represent a
significant cost saving from prices charged by Altronics Competitors .
Don't forget our Expre11 Mell and Phone Order Service - tor the coat of a locel cell,
Bankcard, YIN or MMtercerd holder, cen phorie order tor Nm• day d..petch.
STANDARD DELIVERY a PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA
WIDE - We process your order the day received and despatch via. Australia Post.
Allow approx 7 days from day you post order to when you receive goods
$7.00 OVERNIGHT JETSERVICE - We process your order the day received and
despatch via. Overnight JelHrwlc• Courier for delivery next day Country areas please
allow additional 48-72 hours Weight limit 3Kgs (3Kgs covers 95% of Orders).
$10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express
Road - Please allow 7 days for delivery.
INSURANCE - As with virtually every other Australian supplier, we send goods at
consignees risk. Should you require comprehensive insurance cover against loss or
damage please add 1% to order value (minimum charge $1) . When phone ordering
please request " Insurance" .
TOLL FREE PHONE ORDER - Bankcard.Visa, Mastercard Holders can phone order
toll free up to 6pm Eastern Standard Time. Remember with our Overnight JetHrwlce we
deliver next day.
?') }{'\'
WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K .B .Electronlcs &
Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock
Retravision 351246 WYALKATCHEM D & J Pease 811132
NT ALICE SPRINGS Ascom Electronics 521713 F~rmer Electronics 522967
ACT
CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334
VICTORIA CITY All Electronic Components 6623506 SOUTH
MELBOURNE Winscott Trading 6995740 SUBURBAN
CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics
■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electron ics 346133
QUEENSLAND CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall
Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321
MACKAY Philtronlcs ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron
World 278988 TOOWOOMBA Hunts Electronics
■ 329677 TOWNSVILLE Solex ■ 722015
CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force
Electronics ■ 3770512 CHRISTIE& BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics
:::;::j::: :')::::::::
:
:.:.,:\.:.\.:,:.:,.: ',.:.:,:.:,:.:,.::.:.:.:.:.:.:.':.
Reid
SA
:;:;~88 T~~::~~ F~~;A~~ct~~:~~: ~a~e6yo:~42;3~U~J!~ST:;·~~:r:~E~8 rvse~u■
Electronics
COUNTRY
!~
3~:~El~~~hoo~!c:a~~~~: 31~~~ALL~ S~ re
;l~~tr~:~~~
■ 2671385 CARINGHAH
COFFS HARBOUR
Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218
Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NELSON BAY Nelson Bay
~;=~;;
A woolly picture at Wollongong
For those of us who service TV sets in a big city
served by several transmitters, all carefully sited
and delivering signals of about the same strength
at any one location, life is (relatively) simple. But
not so for our collegues who work in fringe areas,
where customers seek the best of both worlds.
This train of thought was started
by a story from a colleague who
works in and around the
Wollongong area on the NSW south
coast. The story itself, while interesting in its own right, was made
even more interesting because of
the way it highlighted the many problems encountered in this area. But
before getting stuck into the
technical problems, we first need to
set the scene.
For the benefit of those not
familiar with this part of the world,
the City of Wollongong is some
70km - as the crow flies - south
of Sydney. (I've never been able to
work out why the poor old crow has
been given the job of making these
measurements or, for that matter,
how he goes about it. Perhaps he
does it on the basis of so many wingbeats to the kilometre?)
Anyway, the accompanying sim-
ple map should help put the reader
in the picture. Given reasonable
terrain, 70km is not a great
distance for a TV signal but, in this
case, the terrain is anything but
favourable. Wollongong city is at
sea level, and sits immediately
below an escarpment, some 300
metres high, which runs parallel to
the coast and only a few kilometres
inland.
As a result, the advent of TV in
Sydney (using channels 2, 7, 9 and
later 10) saw a forest of tall masts,
fitted with high gain antennas and
amplifiers, which sprang up in
Wollongong and the coastal
suburbs to the north and south. As
might be expected, the results were
patchy and unpredicable. While
Smith might receive excellent pictures, poor old Jones next door
could often get little more than
snow.
\
44
SILICON CHIP
This situation prevailed for some
years, during which time both the
residents and the local TV sales
and service industry learned to live
with it. And, in many cases, they
achieved results which, in theory,
should not have been possible. In
short, the population had become
Sydney TV orientated.
Eventually, the powers that be
presented the area with its own TV
channels: channel 4 (94-101MHz)
as the commercial channel and
channel 5A (137-144MHz) as the
ABC channel. Both these bands,
regardless of their geographical
allocations, have been controversial; channel 4 because it occupied
part of the "international" FM
band, and channel 5A because it
transgresses certain international
satellite channels, and is adjacent
to the amateur 2-metre band
(144-148MHz).
But controversies aside, the
channels have in general served the
area well. The two transmitters are
located on Knight's Hill, some 700
metres above sea level and about
30km sou' sou' west of Wollongong.
They also serve areas to the south,
such as Nowra, Jervis Bay,
Ulladulla and even further down
the coast, as well as inland.
In theory, of course, the locals
should have been content with
these two channels since, officially,
the Sydney channels were never intended to serve that area. But
human nature being what it is, and
considering the history of Sydney
reception, most wanted the best of
both worlds. And very nice too, if
you can get it; four commercial
channels plus the ABC puts you one
up on Sydney viewers.
(By the same token, many Sydney
clubs and hotels have channel 4
and 5A antennas pointed at
Knight's Hill to take advantage of
Sydney sporting events not broadcast locally).
Knight's,
Hill
er~·
eKiama
Nowra
/~~
.
ateman's
Bay
Fig.1: this map shows the area,
south of Sydney, involved in the
accompanying story. The Sydney TV
transmitters are at Gore Hill while
the Wollongong transmitters are at
Knight's Hill.
But satisfying this desire wasn't
always plain sailing. In some cases
it worked out very well, often by
default, but in others it presented a
host of problems.
Signal strength problems
and around Wollongong itself, since
the antenna is pointed towards
Sydney and the local signals are approaching from the rear and the
side. In addition, the antenna is not
cut to favour the local signals, so
there is enough natural attenuation
to prevent problems.
But not always. As we move
south from Wollongong the distant
signals get weaker but, because the
local transmitters are moving
around to the front of the antenna,
their signals get stronger. And as
we said earlier, there is conflict
between channel 4 and channel 9.
The main reason appears to be the
nearly two-to-one frequency relationship between the two channels.
While the second harmonic of channel 4's vision carrier falls short of
channel 9's vision carrier, some of
channel 4's video content would
reach it.
Anyway, the practical result is
that, with too much channel 4
signal, channel 9 becomes unwatcha ble.
As these problems became apparent the TV antenna industry
responded with a range of "traps"
designed to control channels 4 and
5A, and having different orders of
attenuation. The first one offered
provided 30dB attenuation and,
when this proved to be too severe
for many localities, was followed by
20dB and lOdB models.
These helped a lot but were not
adequate in all localities. Which only serves to highlight the difficulties
encountered in this and similar
areas; each case has to be treated
on its merits and installations
tailored to suit.
Which brings us to the specific
situation that started this story, and
which the reader will be better able
to appreciate against the background we have just set out. In fact,
from here on, the story is best handed over to my colleague. This is how
he tells it.
Colleague's story
The story really started about 15
years ago, and concerns a customer
who lives at Ulladulla, about 85km
south of Knight's Hill and about
180km from the Sydney stations at
Gore Hill. I helped him install a new
TV set when he moved into the area
at that time. His home is on an excellent site and I felt sure that
Sydney's signals would be readily
available. But he wasn't interested
and, in fact, for a few years was
content to watch the two local
channels, using nothing more
pretentious than a pair of rabbit
ears.
I don't like rabbit ears. Signal
strength notwithstanding, they
simply cannot provide a clean
Broadly, the problem is one of
having to cope with vastly differing
signal strengths and the risk of
cross modulation caused by powerful local signals mixing with weak
distant ones. In particular, there is
conflict between channel 4 in
Wollongong and channel 9 in
Sydney.
A popular set-up for Sydney
reception is a phased-array antenna, such as the Hills model CA16,
feeding a suitable amplifier, usually
masthead, on the tallest practical
mast. These antennas are cut to
resonate around channel 9, but are
broad enough to cover 7, 8, 9, 10
and even 11 in some circumstances.
This arrangement is often good
enough to cope with both groups of
signals. This is particularly so in
OCT0BER1988
45
SERVICEMAN'S LOG
signal in all circumstances. Movement of venetian blinds and other
metal objects, or even people, can
create all kinds of ghosting problems. As a result, I continued to
urge him, over the years, to fit a decent antenna.
He succumbed in the end and I
fitted a simple 4/5A antenna on a
"hockey stick" mast mounted on
the bargeboard of the house. And
even he had to admit that the improvement was worthwhile.
He was happy enough with this
for the next couple of years, then
suddenly, about 10 years ago, expressed a desire to receive the
Sydney channels. I suspect that the
advent of some sporting events,
available only on these channels,
prompted this decision. Anyway, I
was confident I could provide a
suitable installation.
I chose a Hills CA16 phasedarray antenna, mounted on a
5-metre length of masting, and
feeding a Standard Components
MH20 masthead amplifier. This
produced excellent signals from the
Sydney channels, apart from channel 9, which suffered severe cross
modulation from channel 4.
This came as no surprise, having
come to grips with the problem
previously in this area. The solution called for yet another trap
filter which had been developed by
the antenna manufacturers, following representations from myself
and other servicemen.
Initially, we had tackled the problem using the lOdB or 20dB 4/5A
filters already mentioned. This was
tricky enough in itself because the
strength of the channel 4 signal as
fed to the amplifier can be quite
critical. Too little attenuation can
wreck channel 9, while too much
46
SILICON CHIP
can put channel 4 into the noise.
And the gap between these limits
can be quite narrow.
But there was an even bigger problem, involving channel 5A. For a
couple of reasons, channel 5A's
signals are significantly weaker out
of the antenna, to the point where
they can be well into the noise by
the time channel 4 is under control.
One reason is that 5A's signals
are naturally weaker in this area,
an official DOTC survey listing
them as lOdB down on channel 4.
By my observations this figure may
be a little high, but there is at least
a 6dB difference.
The second reason is that this
phased-array antenna favours
channel 4 rather than 5A; probably
because, being cut for channel 9, it
favours channel 4 on a harmonic
basis. Anyway, whatever the
reason, channel 5A can be down
anything from 6dB to lOdB. So, on a
worst case basis, channel 5A could
be 20dB down on channel 4, and
even in the most favourable circumstances is going to be 12dB
down.
By itself, this difference can
usually be tolerated. But add 10 to
20dB attenuation caused by a filter
needed to control channel 4, and 5A
is well and truly into the noise.
The new filter, designated
FL300-4, was designed to attenuate
channel 4 only, by 18dB. I have no
details of its response curve, but it
is reasonable to assume that it
would be level within a few dB over
the bandpass. It was a simple
device, on a printed board measuring about 25 x 60mm and consisting
of four resistors, three fixed
capacitors, a trimmer and three
printed inductors. It was enclosed
in shrink plastic for external moun-
ting, but I chose to mount it in the
amplifier housing.
And it worked. Channel 4 was
eliminated from channel 9, and
channel 5A was left in the clear to
provide a clean picture. So
everyone was happy.
Lost colour
End of story? No, the beginning
really. As I mentioned, all that happened about 10 years ago and was
virtually forgotten until recently.
Then the customer was on the
phone with the complaint that he
was losing colour on channel 4.
My first reaction was to enquire
whether it was only channel 4 that
was faulty. (Some customers will insist that a fault is on one channel
only, for the simple reason that they
only ever watch that channel!)
On being assured that channel
5A and all the Sydney channels
were OK, my next reaction was to
suspect faulty fine tuning for channel 4. On this basis, I told the
customer to check the fine tuning
and see if this made any difference.
If that didn't work, then I would
have to make a call.
Well, it didn't work and he was
on the phone the next day to report
this. So I headed for the hills. I'd
taken care to pack the field
strength meter because, even at
that early stage, I had a feeling that
the fault was likely to be associated
with the antenna.
I found the situation essentially
as the customer had described it,
and quickly convinced myself that
there was nothing wrong with the
set.
So I disconnected the coax from
the set and made some field
strength measurements on the
channel 4 signals. The vision carrier (95.25MHz) was running at
54dBu (0dBu = 1µ V) which was
possibly a trifle low, but not
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FREQUENCY (MHz)
Fig.2: response curve of the channel 4 filter. As can
be seen, it gives a pronounced dip at 100MHz.
seriously so. But the sound carrier
(101.75MHz) was down to 35.5dB
and, while it is normally down
significantly on the vision carrier, I
felt that this was more than it
should be. And if something was
lopping off the top of the response
curve it would show up as a weak
sound carrier, but could also mean
a weak chominance sub-carrier.
So it was up the ladder and onto
the roof to lower the antenna for a
thorough inspection. This revealed
nothing significant. Nor were there
any other visible faults , such as bad
coax connections, or the like. So it
looked like something funny in the
ampiifier or the filter.
The filter was the easiest to
check, by the simple process of
removing it. This brought the vision
carrier to 73.5dBu (a jump of just on
20dB) and the sound carrier to
59.5dBu (a jump of 24dB). Of
course, channel 4 was now back to
full colour. But poor old channel 9
was the loser with cross modulation
from channel 4 very much in
evidence.
The vision carrier increase was
not unreasonable for an 18dB filter,
but I was suspicious about the
sound carrier which had recovered
an extra 4.5dB gain compared to
the vision carrier gain. This seemed
to confirm that there could be
something amiss at the high frequency end of the filter bandpass,
as I had already half-suspected.
As far as the immediate situation
was concerned, the easiest thing to
do was leave things as they were,
while I took the filter back to the
workshop for a more detailed check
and consideration of what best to
do.
Back at the bench I fed signals
from the generator through the
filter and into a suitable level
meter. Selecting an arbitary zero
reference at B0Mflz I took a series
of readings across the bandpass.
The results are shown in the accompanying graph and the point that
stands out is a marked dip at
100MHz which is virtually the
chrominance sub-carrier frequency
(99.7MHz) and which is no less than
16dB down from reference.
Just why the filter had developed
this dip was a mystery. A visual examination revealed nothing and a
detailed component-by-component
check would have taken more time
than I could spare at that stage. So I
simply pushed it to one side.
Antenna trap
The important thing was to
decide on the best solution. Simply
fitting a new filter was one option,
but I decided to try another approach which I had developed more
recently. In many cases, it has proved to be perfectly adequate.
This involves making a simple
trap from a length of coax; a
quarter wavelength long at the appropriate frequency [allowing for
the coax velocity factor) and which
is connected across the amplifier
input terminals. The other end is
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Phone: (02) 724 6982
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OCT0BER1988
47
SERVICEMAN'S LOG
left open and, by reason of the
quarter wavelength dimension,
makes the device look like a short
circuit at the chosen frequency.
The "Q" of such a trap is quite
high - too high for this application
- so the trick is to cut it for a lower
frequency, about 88MHz in this
case . This normally provides
enough attenuation to prevent cross
modulation but has little effect on
frequencies above the channel.
This offers another advantage.
There are several Sydney FM stations in this segment, and these are
well received in good local positions. The ability to use the TV
antenna for these signals is a bonus
which customers appreciate.
Happily, this approach worked in
this case and I had the customer's
system back to normal in a couple
of days. It is not, of course, a
panacea, but when it works it has
the advantage of low cost, simplicity, and reliability. A convenient
form of coax is the very thin Teflon
dielectric type, the higher cost being of little consequence in this
application.
End of story
Well, that's my colleague's story
and I think the lesson to be learned
is that there is no one answer to the
problems encountered in such
areas. The successful serviceman
or technician is the one who has a
whole range of options available,
most born of long experience in the
area, and a good understanding of
the basic principles involved.
From my own bench
For a change of scene, here is a
short report from my own bench
about a puzzling case of sound
distortion in a TV receiver. The
first one occurred several years
ago and I have had about eight
since then. Naturally, after the first
one, they presented no problem.
I had intended to write about this
on many occasions but, for one
reason or another, never managed
it. It was only when another such
case landed on the bench a few
days ago that I was reminded of my
good intentions and resolved to procrastinate no longer.
That first case involved a Sanyo
6603 colour TV set but I hasten to
add that the fault is not confined
to any one brand. The lady who
owned it was basically an ABC
viewer but occasionally chose a
commercial program if it
appealed to her. And this
was the first vital clue
because her complaint was that,
FOR A Ct\~~GE OF see.NE
HE'RE. IS ~ SHOR, 'R£POR.T'
FROM W\'1 OWN 'gE.NCH•o•
48
SILICON CHIP
while the sound was perfect on the
ABC, it was distorted on one of the
commercial channels. (I can't be
certain which one; most likely channel 9, but I would stand corrected
on that. In any case, it doesn't alter
the sense of the story}.
It was convenient to make a
house call on that occasion, and I
f?und that the customer's description of the fault was quite accurate,
except that the distortion was far
worse than she had led me to
believe. But why distortion on that
channel only? The picture was first
class but I checked the fine tuning
anyway, just in case of something
silly in that department. All I learned was that, by detuning the channel to the point where the picture
had virtually vanished, the sound
was significantly improved, although it was still a long way from
perfect.
Then the penny dropped. That
particular channel had just enjoyed
a blaze of publicity as a result of its
being the first to introduce a stereo
sound system. So that was it; I'd
have been prepared to wager a new
picture tube to a dud diode that for
some reason, yet to be determined,
this set didn't like the stereo sound
signal.
Well, that was a start, but there
was still a -way to go. What would
cause a set to respond to a stereo
signal in this way? With the stereo
system only recently introduced, it
was a real brain teaser to try to
visualise how this might happen.
The stereo signal
I had followed the technical
discussions which had preceded
the selection of the system, so I was
familiar with its basic theory. And
to refr_e sh the reader's memory, our
TV stereo system uses a second
sound carrier alongside the main
one, approximately 242kHz higher
in frequency; more exactly,
242 .1875kHz ± 1Hz, if my memory
serves me correctly. (All right, all
right, I looked it up}.
To maintain compatibility, the
main channel carries a left plus
right (L + R} signal (mono receivers
thu_s receive a normal mono signal}
while the second channel carries a
right only (2R} signal. In a stereo
receiver, these two signals are
SIF AMP .
& DEMOD .
IC151 AN340
or LA1320
SYNC. DRl\11
0202 2SC5:
18'-
.,
"""
fl90 1'
3300
FRO'"4 SW90 18
l
TO A UOIO
OUTPUT
Uh'
fll:('11.'
Fig.3: portion of the sound IF channel of the Sanyo 6603 showing the
IF amplifier and demodulator chip (IC151), the sound IF transformer
(T151), and the quadrature coil (T152).
matrixed together to recover the
separate left and right channels.
Which is all very well as basic
theory, but was not much practical
help right then. For one thing, I
couldn't be sure whether I had a
one-off situation - ie, a fault in this
particular set - or whether there
was something in the design of this
model which made it incompatible
with the new system; something
which nobody had foreseen when
the set was designed.
I finally decided that the faulty
design theory was the lesser
possibility, particularly as I had
heard nothing of any such probl~m
elswhere. But, if it was this particular set, where did I start
looking?
I fished out the manual and turned to the sound IF section of the circuit, the relevant portion of which
is reproduced here. The main portion is the sound IF amplifier and
demodulator chip, IC151 (AN340/
LA1320}, and I had to consider the
possibility that the fault could be in
the chip itself, or in any one of a
dozen or so associated minor
components.
But my strongest hunch was that
it was simply an adjustment problem, if only because such maladjustments, while rare, are not
unknown in the mono scene, where
they cause varying degrees of
distortion. And, while in theory at
least, such adjustments should be
made using a sweep generator and
CRO, experience has taught me that
it is usually possible to make a
perfectly acceptable adjustment, in
the field, with nothing more than a
keen ear and a little care.
The two adjustments I had in
mind involved the sound IF
transformer, T151 , which feeds the
sound IF to pins 1 and 2 of IC151 ,
and the sound detector transformer
(quadrature coil) between pins 9
and 10. Based on experience I
tackled the latter first.
TETIA TV TIPS
National TC1401 A
Symptom: Bottom foldup . Linearity
can only be corrected if height is
reduced almost to minimum.
Voltage on TR454 collector low at
80V instead of 91 V.
Cure: C-463 , a 22µF 250V electro , open circuit. This capacitor is
the bypass on the main rail to the
vertical output and its loss drops
the rail voltage , as well as introducing excessive negative feedback.
A vital precaution in making such
adjustments is to first note and
mark the position of the core or
slug, then move no more than one
turn initially to judge the effect.
Further adjustments can then be
made if necessary but one should
always be in a position to return to
the original setting.
In this case, one turn was enough
to produce a dramatic improvement, so I kept going until I passed
the obvious peak, then returned to
that point. And for the moment, that
seemed to be the answer. But had I
found the right peak? Was this the
main sound channel or the second
channel?
Confident that I could return to
this setting when I needed to, I turned the adjustment back to where it
had been, then beyond this until I
found another sound channel. Subjectively, it was hard to pick the difference between the two, but I
reasoned that the first was more
likely to be the right one, so I reset
the core to this position. Then I moved to T151 and gave it a slight
tweak, which was all it seemed to
need.
Finally, I switched the set to the
ABC, which I knew was not even experimenting with stereo at that
time, and was happy to note that
the sound was perfect here also.
Undoubtedly, had I picked the second channel instead of the main
channel, this test would have
revealed it.
So that solved that problem and,
as I said earlier, I have had about
eight such cases since._ All have
responded completely to this simple
adjustment routine.
As to why the fault occurred in
the first place, I can only guess.
One possibility is that the adjustments simply drifted, and it is
true that most of the sets had been
in use for several years. On the
other hand I am more inclined to
the idea that the adjustment was
out from day one; not far enough
out to upset a mono signal, and
therefore capable of passing final
test, but far enough out to allow a
distorted version of the second
channel to be heard.
That's all we have room for this
time around; see you next month.~
OCT0BER1988
49
T
H
E
MUSICAL
T E C H
'For us the realistic reproduction of music is the essential promise'
Saul B. Marantz
THE CL
MATCH
ASSIC
BOX CRYSTAL SET
By STEVE PAYOR
Have you ever built a crystal set in your
life? If you've never a built a crystal set
before, this is the one to have a go at.
You '11 be surprised at just how well it
performs.
This interesting little project is
easy on the budget but big on
satisfaction. And it won't cost you a
cent to run after it's finished, even
if you let it play continuously until
the year 2088.
Make no mistake about it, this
crystal set is a real, working AM
radio receiver, not just a nostalgic
novelty.
Until the invention of electronic
amplification, the humble crystal
set was the only form of wireless
reception in use. Circuit development reached a peak around the
1920s and the "Super Crystal Set"
described in the March 1988 issue
of SILICON CHIP is a typical example
of the type of receiver used for shipto-shore communications over
thousands of miles.
Simpler crystal sets, using only a
single tuned circuit, were used for
listening to domestic broadcasts
and the crystal set described in this
article is in the same category. It's
cheap, easy to use, and capable of
receiving all local broadcast stations at worthwhile volume.
There is a price to pay for free
entertainment however. First, you
have to string up an antenna and
provide a fairly good earth. Second,
you will have to find a pair of sensitive, high-impedance headphones.
More about the headphones later.
Indoor antenna
Our new crystal set has been
designed to work with 15 metres of
hookup wire as an indoor antenna.
In most cases just draping it around
A1
MATCHBOX CRYSTAL SET
Fig.1: the complete circuit for our matchbox crystal set. Unlike
most other crystal sets, it uses variable inductance tuning to give
constant bandwidth and volume over the entire tuning range. The
headphones should be high-impedance types (see text).
a skirting board will do the trick.
But if you live in a poor signal area
it may be necessary to run the wire
out the window and up and away
from the house.
In any case, stick to a length of 15
metres to start with, because the
antenna capacitance and resistance form an integral part of the
tuned circuit.
As you can see from the circuit
diagram and photographs, the tuned circuit consists of an inductor,
wound on the outside of a matchbox, in parallel with a fixed
capacitor and the antenna
capacitance. The inductance is
varied over a wide range by sliding
two pieces of ferrite rod in and out
of the matchbox.
The ratio of minimum to maximum inductance that can be
achieved in this way is about 4:1,
which is not quite enough to cover
the entire broadcast band in one go.
This band extends from 531kHz to
1602kHz; ie, a 3:1 frequency ratio
which requires a 9:1 change in
inductance.
We solved this problem by providing an antenna tapping, A2, at
the centre of the coil. This tapping
is used when tuning the top half of
the band, and the antenna
capacitance is transformed to an
equivalent capacitance of only
32pF or thereabouts.
When the antenna is connected
to Al, the full antenna capacitance
(approximately 135pF) is in parallel
with the tuned circuit. This effectively doubles the tuning capacitance and shifts the tuning range
down to cover the bottom half of the
band.
The two antenna tappings also
perform another vital function they enable us to optimize the
antenna coupling for each tuning
range.
The subject of antenna imOcT0BER 1988
53
1~NJ~~:Els
El--0
400
EQUIVALENT
TO
EART!!J:""°
...
· V
135PF
300uH FIXED
SIGNAL
INDUCTOR
Fig.2: equivalent circuit for a
15-metre long antenna. It can be
represented by a 135pF capacitor
in series with a 400 resistor and
an AC voltage source.
pedance, and its loading effect on
the tuned circuit, is perhaps the
most important consideration in the
design and operation of a crystal
set. So let's start by considering the
antenna as an electrical circuit.
Equivalent circuit
Fig.2 shows the equivalent circuit of our 15 metres of hookup wire
at broadcast band frequencies. The
wire is too short for its inductance
to be significant at these frequencies. Thus, the antenna can be effectively represented by a capacitance of 135pF in series with a
small voltage source [the received
signal) and a certain amount of
resistance.
This resistance can be broken
down into two parts. The major
component is just the highfrequency resistance of the antenna wire itself. The other component
is the "radiation resistance",
which represents the coupling of
the antenna to the surroun~ing
space.
The total series resistance of our
15-metre indoor antenna [including
the earth connection) is about 400
at 1MHz, of which only a few ohms
is the actual radiation resistance.
Thus the antenna's efficiency is
quite low.
One way to increase the antenna
efficiency is to make it longer and
higher. The wire resistanc:::e increases in proportion to the length,
whereas the radiation resistance
goes up with the square of the effective height above ground. This
should answer the old question
"why is a longer antenna better
than a short one?" .
54
SILICON CHIP
Fig.3: the traditional "textbook" crystal set.
The need for tap-changing as the set is
tuned makes operation awkward.
If we could run a very thick
antenna wire straight up to a height
of a quarter of a wavelength (75
metres at 1MHz), we would find
that the series inductance would
exactly cancel out the capacitive
reactance. Thus, the only impedance left would be the radiation
resistance, about 370. To achieve
this ideal performance, this antenna would also require a perfectly
conductive ground plane - a copper disc 150 metres in diameter
would be near enough!
Believe it or not, at a distance of
20km from a typical broadcast station, such an ideal antenna would
receive more than 20mW of power.
This is enough to provide quite
respectable sound level from a
loudspeaker!
Obviously such an antenna
system is not practicable, but one
should bear in mind that a crystal
set needs the best possible antenna
PARTS LIST
1 wooden matchbox
9 metres 0.355mm (27 B&S)
enamelled copper wire
5 solder lugs
1 polystyrene or silvered mica
(low loss) capacitor;
approximately 1 OOpF
1 germanium diode, OA47,
OA91 , OA90 or equivalent
4 miniature alligator clips
Miscellaneous
1 5 metres of insulated hookup
wire for antenna, additional wire
for earth lead as required, highimpedance headphones (see
panel) .
and earth system to function
effectively.
A microwatt of received power
will provide good volume with a
sensitive pair of headphones, a
nanowatt is perfectly listenable,
and a signal of around 50 picowatts
is just readable.
A good earth
For the record, this crystal set
will receive stations at listenable
volume with less than a metre of
antenna. However, it won't work at
all without an earth connection, for
the simple reason that the antenna
current has nowhere to flow.
One can get away with a large
metal object buried in damp soil,
but since dirt is not as conductive
as metal the best ground connection
would be a large metal grid, laid on
or under the ground, and stretching
as far as possible in all directions.
Domestic water pipes fit this
description admirably.
Selectivity and coil tappings
Sharpness of tuning is always a
problem with simple crystal sets the resistive component of the
antenna impedance and loading by
the diode circuit both tend · to
reduce the selectivity of the tuned
circuit.
One solution to the problem is to
provide several taps on the inductor, as in the typical "textbook"
crystal set of Fig.3. If we tap the
antenna and diode into the coil a
few turns from the "earthy" end,
the tuning will be very sharp
because the loading will be negligible. But the signal coupling will be
correspondingly small.
Selectivity and "Q" Factor
The "Q" or Quality Factor of a
tuned circuit is the ratio of its centre frequency to its -3dB band.,
width (see Fig.4). For example, a
tuned circuit with a centre frequency of 1 MHz, and a -3d8 bandwidth of 1 0kHz, has a Q of 100.
Normally, a Q of this magnitude
is only just achievable with a welldesigned low-loss inductor. The
unloaded Q of the Matchbox
Crystal Set at 1 MHz was
measured at around 95 to 98.
Conveniently, Q is also equal to
the ratio of the impedance of either
the inductor or capacitor (they are
equal at resonance) to the
resistance causing the energy loss
in the tuned circuit.
For example, consider again a
circuit with a Q of 100 at 1MHz. If
the tuning capacitance is 1 00pF, it
has a reactance of -j16000 at
1 MHz and the inductor has a reactance of +j1600O (253µH). For a
Q of 1 00, the equivalent series
resistance of the tuned circuit is
1600/100 = 160. The equivalent
parallel resistive load would be
1600 x 100 = 160k0. (Fig.5.)
Thus a high-Q tuned circuit must
have very little series resistance (in
the coil for example), and a very
high parallel load resistance.
The unloaded Q of the Matchbox
Crystal Set is almost entirely determined by the coil resistance
which, as we have just calculated,
is about 160 at 1 MHz. Compare
this with the DC resistance which
is only about 1.30!
When the crystal set is in use,
the Q is considerably lower,
because of the combined loading
The optimum tapping points can
be found by experiment but (and
here's the catch) they vary with
each frequency setting. For example, at the low frequency end of the
band, one might obtain best results
with the antenna tapping at 100%
(ie, at the top of the coil) and the
diode at about 60% of the turns. At
the high frequency end of the band,
the optimum antenna tapping may
be only 10%, and the diode tapping
about 25%.
BW
AMPLITUD
OdBl+-----t-~
Q=
folBW
lo
FREQUENCY
RESONANT
FREQUENCY
Fig.4: the "Q" of a tuned circuit is
the ratio of its centre frequency to
its - 3dB bandwidth.
25311Ht:D
OR~
lo
= 1MHz Q = 100
Fig.5: equivalent high•Q tuned
circuits (Q = 100 at 1MHz).
of the aerial resistance and the
diode circuit.
With a 5k0 headphone load and
a 1 5-metre antenna connected to
"A2", the Q of the Matchbox
Crystal Set was measured at
around 50 at 1MHz, giving a
-3dB bandwidth of 20kHz. Since
the typical minimum separation
between local broadcast stations
is about 50kHz, this would put the
interference from an adjacent carrier at -14dB. Unless the wanted
signal is very weak, the major component of the interference will be
ultrasonic, and therefore inaudible,
so you will find that the Matchbox
Crystal Set has adequate selectivity for most applications.
There are three reasons why the
tappings change so much. First, the
RF resistance of the antenna wire
increases with the square root of
the frequency (due to the "skin effect"). But worse than this, the
radiation resistance goes up with
the square of the frequency. Thus,
the damping effect of the antenna
resistance is considerably greater
at the top end of the band than it is
at the bottom end.
Second, to obtain the same selec-
tivity at the top end, the tuned circuit needs to have a "Q" three
times higher than at the bottom end.
Finally, to make matters worse, the
impedance of the L and C elements
is three times higher at the top end
of the band. The result is that we
need to reduce the effective antenna and diode loading by more than
a factor of nine as we tune up the
band.
For this reason the fixed inductor/variable capacitor approach is
just about the worst arrangement
possible. The only reason why this
circuit is so popular is that variable
capacitors are ·(or were) readily
available. Variable inductors, on
the other hand, were something you
had to make yourself.
Variable inductance is best
If we want a tuned circuit that
maintains constant selectivity with
the antenna and diode connected to
a fixed tapping point, the first thing
we must do is use a variable inductor instead of a variable capacitor.
Oddly enough, all of the earliest
crystal set designs used variable inductors. These were invariably
quite cumbersome affairs, using
either a sliding contact arrangement or a pair of coils which slid
or rotated inside one another.
Nowadays, making a variable inductor is almost too easy, thanks to
the availability of low-loss RF
ferrites.
With a fixed tuning capacitor
and a variable inductor, the impedance of the L and C elements is
three times lower at the top end of
the band. This means that, for a
given loading, the tuned circuit Q
will automatically be three times
higher. In practice, the effect is not
quite this good, since we have ignored the resistive losses in the coil
itself.
Another problem is that the
loading is not constant. Remember
that the antenna resistance increases with frequency, so the optimum tapping point still needs to
be moved, although over a much
smaller range.
This design solves the problem by
electrically "moving" the A2 tapping as the tuning is adjusted.
Although this tapping is nominally
half-way up the coil, the effective
OCTOBER 1988
55
Headphones for the Matchbox Crystal Set
Owning a good pair of highimpedance headphones is a must
for any crystal set enthusiast. You
may get lucky poking around the
disposal stores, but most of the
headphones you are likely to find
will have a fairly low impedance
Don't let this worry you too
much . If you find a sensitive pair in
good condition, then a small audio
transformer with the appropriate
turns ratio is all you will need to
turn them into a first class pair of
crystal set headphones.
The most sensitive type to look
for are those with a "balanced armature" mechanism and a light
aluminium diaphragm . Old telephone earpieces of this type are
excellent and, even allowing for
the losses in the impedance matching transformer, they are just
about the most sensitive transducers ever made.
Next, in order of decreasing sensitivity, come the even older style
of headphones with sheet iron
diaphragms. These are still being
manufactured in 20000 impedance, but the sensitivity is not
as good as it was in the old days.
Next come the older style of
"modern" headphones, the ones
coupling varies depending on how
far the ferrite rods are inserted into
the top of the coil. When the rods
are only partially inserted, the inductance of the top half of the coil
is greater than the inductance of
the bottom half.
Also, not all of the magnetic flux
from the bottom half of the coil
passes through both halves - some
of it leaks out the sides of the matchbox. Thus, the effective tapping
is less than half-way up.
When the ferrite rods are fully
inserted, all of the flux flows
through both halves of the coil and
the effective tapping point is exactly half-way.
So our "fixed" antenna tapping
actually "moves" whilst we are
tuning from station to station.
There is an obvious advantage of
this tuning system - it's dead easy
to use. As a bonus, the Matchbox
56
SILICON CHIP
with small 80 loudspeakers in
them, and very large earpads.
A good scheme is to connect
both 80 drivers in series (get the
phasing right) and use a 1 k0:80
transistor radio type audio
transformer (eg , the M-0216 from
Dick Smith Electronics). You may
lose a little bass response, but you
will have a pair of 20000
headphones.
Note that the DC resistance
looking into the matching
transformer will be a lot less than
20000, so the transformer looks
like a short circuit to the DC
voltage from the rec'titied carrier.
Actually, it is not quite this bad
because the diode still has a few
thousand ohms of forward
resistance. Nevertheless, it is
worth taking some steps to avoid
excessive damping of the tuned
circuit.
Fig.6 shows how a series
resistor can be added to bring the
DC resistance up to 2k0. A bypass
capacitor prevents any attenuation
of the audio signal.
This technique can also be used
to make a pair of medium impedance phones from a couple of
old telephone earpieces. These
Crystal Set automatically maintains
a constant bandwidth and volume
over its entire tuning range.
There is a second and not-soobvious bonus: we can accurately
mark a tuning scale on the sliding
part of the matchbox. This is normally not possible with an "ordinary" crystal set, since a slightly
different tuning scale is required
for each antenna tapping - hardly
worth the bother!
Actually, the Matchbox Crystal
Set has two tuning scales, one for
the top end of the band (with the
antenna connected to AZ), and one
for the bottom end (with the antenna connected to Al).
As you can see from the photographs, both scales are almost
linear, and all of the Sydney stations are spread out quite nicely
across each range. The same will
apply for other locations.
" 20000" 1k·BO AUDIO
HEADPHONES TRANSFORMER
HEADPHONE
DRIVERS
80
Fig.6: this diagram shows how to
convert a pair of low impedance
headphones into 20000 highimpedance headphones. All you
need is a small audio tran~former,
a resistor and a capacitor.
0.22·0.47
BALANCED
ARMATURE
TELEPHONE
EARPIECES
200 (0C)
Fig.7: this circuit will give good
results with 200 telephone
earpieces.
have an AC impedance of a few
hundred ohms each, but a DC
resistance of only 200. Connected as shown in Fig. 7, they
perform surprisingly well, although
with 'a proper matching transformer
Once your crystal set has been
calibrated, the tuning scales will
always be spot on, so long as you
maintain a fixed antenna length.
Diode circuit
For the sake of simplicity, the AZ
tapping is used for the diode as well
as the antenna.
Loads of between Zk0 and 10k0
are about right for this tapping. If
you intend to use a very high impedance load, such as a pair of
piezoelectric "crystal" earpieces,
then connect the diode to the top of
the tuned circuit (ie, to Al). The
load resistance with crystal earpieces will be somewhere between
100k0 and lM0.
Headphone impedance
At this point we should explain
why the headphone impedance required for crystal sets is always
DIODE
IN~&T
PIEZOELECTRIC
TRANSDUCERS
4.7k-10k
Fig.8: a 4.7kll-10kll resistor should be added in parallel with piezoelectric
transducers to prevent distortion due to insufficient shunt resistance.
the results are phenomenal.
If you don't want to go to all this
trouble, try a pair of piezoelectric
transducers. Murata make some
very sensitive piezo inserts which
are easy to fit into any old-style
headset. These are available
(along with lots of other goodies)
from Orpheus Radio, RSD 898,
Ballarat 3352. Telephone (053)
34 2513.
Piezoelectric transducers have
the opposite problem to electromagnetic transducers - they
have an infinite DC resistance, and
a fairly low AC impedance. Electrically, a typical pair of piezoelectric transducers in parallel
looks like a 0. 1µF capacitor. If you
connect them to the diode without
a load resistor, all you will hear is a
faint, distorted crackling.
very high, compared with the impedance of modern high-fidelity
headphones (usually 80 to 320).
Why can't we just move the diode
tapping way down towards the bottom of the coil and use low impedance headphones? The answer
is we could, if we could find a diode
with a resistance of about 100 at a
forward voltage drop of say lOmV.
The best all-round diode for
crystal set use is the gold-bonded
germanium type OA47. At lOmV
applied voltage, a typical device exhibited a forward static resistance
of 26k0 and a reverse resistance of
3 lk0. So, for signal voltages of
± l0mV, no effective rectification
takes place.
When the voltage was increased
to lO0mV, the forward resistance
dropped to 7k0 and the reverse
resistance increased to 73k0. Rectification now takes place but, for
Fig.8 shows the demodulated
signal envelope as delivered by
the diode into a load which has too
much capacitance and not enough
shunt resistance. Severe audio
distortion results because the
capacitor can't discharge rapidly
enough to follow the audio frequency variations. Adding a 4. 7k0
to 1 0kO resistor in parallel with the
transducers will fix this problem.
Last, but not least, you might like
to try a pair of "crystal" earpieces.
These use tiny crystals of a
naturally-occurring piezoelectric
salt and their impedance is very
high. A pair connected in parallel
will only need a shunt resistance of
between 1 0OkO and 1 MO for best
audio quality. Often, the reverse
leakage of the germanium diode
alone will be sufficient.
reasonable efficiency, a load in excess of 10kO is necessary to prevent
undue loading.
There are two possibilities for
improved rectification with low impedance loads. One is the so-called
"backward diode", which is really
a zener diode with a reverse
breakdown voltage of 0V. These are
normally used only in microwave
detectors and are hard to come by.
Another approach is to use a battery and potentiometer to bias a
silicon diode into forward conduction. By adjusting the bias, you can
select the best compromise between forward and reverse resistance for a given load.
This approach was often used in
the past, especially when using a
"carborundum detector". This was
a diode made from a crystal of
silicon carbide with a sharpened
steel point sticking into it. It needed
This old telephone earpiece was
converted to high impedance
operation using the circuit shown in
Fig.6. The parts all fit in the plastic
housing.
a forward bias of about 1V for best
results.
However, high impedance headphones and an ordinary germanium
diode are still the most convenient
arrangement. If you want to, you
can make a suitable pair of phones
using currently available parts (see
panel).
What, no .00tuF capacitor?
Conspicuous by its absence from
the circuit diagram is the usual
.00lµF capacitor across the headphones. This is included in all the
"textbook" circuits to provide RF
filtering of the audio output, but its
presence is usually undesirable.
The impedance looking into a rectifier with a capacitive filter is
close to half that of the load
resistance, so with our headphones
already lower than the optimum
load resistance, this capacitor only
makes things worse.
By contrast, an inductive filter
can increase the effective load
resistance to slightly more than the
headphone resistance. A lmH or
2.5mH RF choke in series with the
diode may well improve the performance with low impedance headphones (eg, lkO or even 6000) - at
least in theory. In practice, the
choke can be left out as there will
be sufficient inductance in the
headphone windings or in the matching transformer.
Construction
Let's begin construction by
locating a suitable matchbox. This
OCT0BER1988
57
glue is incredibly tough, and it is the
only one which can take soldering
temperatures without embarrassment.
Start with the three lugs on the
"antenna" side of the matchbox.
Spread an ultra-thin smear of
Urethane Bond on the matchbox,
and a little more on the solder lugs.
Position one lug at each end, and
one exactly in the middle. Leave the
box standing on its side for several
hours until the glue hardens.
Next, turn the box over and glue
the two headphone lugs exactly opposite the "A2" and "E" lugs,
checking the location with a ruler.
Stand the box between two heavy
objects to keep it level until the glue
sets.
The tuning scale was carefully hand-drawn on the inner part of the matchbox.
Note the diode running across the centre of the matchbox and the
polystryrene capacitor between the "Al" and "E" terminals.
L1,L2
= 37 TURNS,
0.355mm DIA. ENAMELLED
COPPER WIRE, CLOSE WOUND.
100pF
TUNING
CAPACITOR
FERRITE RODS GLUED
TO INSIDE OF
MATCHBOX TRAY
f
\
V
'
SOLDER LUGS GLUED TO MATCHBOX
COVER WITH URETHANE ADHESIVE.
Fig.9: here's how to build your matchbox crystal.set. Each
of the coils consists of 37 turns of 0.355mm guage wire, but
other wire gauges can also be used (see text).
is not so easy as it sounds because
wooden matchboxes are scarce
these days, and the cardboard ones
are a little too flimsy to wind a coil
on. In any case, you will need to
make up a wooden "dolly" to prevent the box from being crushed
during the winding. Carefully plane
a block of wood so that it just fits
tightly inside, then glue a short
piece of broom handle to it and put
it aside.
Next, give the insides and outsides of both halves of the matchbox a coat of Satin Estapol or
similar clear polyurethane finish.
This strengthens the assembly considerably. Allow it to dry overnight,
then lightly sand all over with 600
58
SILICON CHIP
grade paper to smooth any furry
bits. The top coat of Estapol will be
added later, when the coil windings, etc are in place.
Meanwhile, prepare the five
solder lugs by firstly tinning them
- this will minimise the amount of
soldering heat needed later on.
Once tinned, thoroughly scrub
away all traces of the flux resin
with a tissue and methylated
spirits, then bend the lugs through
90° as shown in the photographs.
Glueing the lugs
The best glue for this job is Dow
Corning "Urethane Bond" (formerly sold under the Selleys label). This
Winding the coil
The recommended wire gauge is
0.355mm (27 B&S) but don't worry
if you don't have the exact size good performance can be obtained
with any gauge from 0.315mm to
0.5mm (28 B&S to 25 B&S). Of
course, the number of turns that
will fit in the available space will
vary, but the appropriate choice of
tuning capacitor will compensate
for any variation in inductance.
For example, on one prototype,
wound with 0.355mm wire, two
coils of 37 turns each just fitted between the lugs. This crystal set required a tuning capacitor of l00pF.
A second prototype was wound
with 0.5mm wire. The two coils ended up having only 23 turns each,
and a 270pF tuning capacitor was
required.
Performance wise, there was little difference between the two windings, although the second set had
a slightly restricted tuning range,
and it preferred a lower headphone
impedance.
When it comes to winding the
coil, you can use one of two
methods. Either wind each half of
the coil separately, terminating the
wire on the solder lugs as you go, or
wind the whole lot in one go, with a
few extra turns across the central
gap which can be snipped out later.
Keep a heavy tension on the wire
all the time, and don't let go or you
will find yourself having to start all
over again. In fact, it's a good idea
to have on hand several short
pieces of masking tape, for holding
flanges, and soldered the end of the
antenna wire to it. A band of flat
elastic keeps the wire in place
when it is wound up.
For the earth lead, we suggest
that you use a few of metres of wire
with a miniature alligator clip at
one end, and a large jumper lead
clamp at the other end, which can
fit around the kitchen tap, or a
water pipe.
Initial testing
We made up an antenna reel using a tin can with a couple of large "Milo"
lids as flanges. The headphones were put together from a pair of discarded
telephone headsets and a small audio transformer.
the wire in place should you need to
stop for any reason.
It isn't necessary to count the
turns, just fill up the available
space between the lugs with a neat,
close-wound layer of wire.
When the time comes to solder
the wire to the lugs~ you can temporarily anchor the turns in place
with more masking tape, or secure
the windings with "Super Glue" or
a tiny smear of "Araldite".
Thoroughly scrape and tin the ends
of the wire, and solder them to the
lugs with a minimum of heat.
Mounting the components
The diode runs from the middle
"A2" lug, across the front of the
matchbox, to the headphone lug on
the other side. Bend the leads neatly to follow the shape of the box.
The tuning capacitor runs down
the side of the matchbox, between
the "Al" and "E" lugs, but its exact value needs to be determined
experimentally, so do not solder it
in place at this stage.
The only other components are
the two pieces of ferrite rod, but
first they need to be cut to length.
Ferrite is quite hard and brittle.
About the only way to cut it is to file
a groove right around the rod and
then break it by hand. Trim the rod
if necessary by rubbing it on a sheet
of silicon carbide paper (wet or
dry), using kerosene as a lubricant.
Check that both pieces fit snugly
lengthwise down each side of the
"drawer" part of the matchbox. If
everything is correct, give them a
wipe over with methylated spirits,
then glue them in place with
5-minute AL'aldite.
By the way, any type of round or
flat ferrite rod will do, providing it
is "antenna" grade ferrite.
Accessories
The crystal set is now ready for
testing but first we need some accessories to complete the setup.
Number one on the list is a suitable
pair of headphones, and we have
prepared a panel describing a
number of practical alternatives.
Fit a pair of miniature insulated
alligator clips to the headphone
leads.
Next; measure out 15 metres of
medium or heavy duty hookup wire
for the antenna, and fit a miniature
alligator clip to one end. You may
wish to secure the other end to
some sort of spool, so that you can
wind the antenna up without getting it thoroughly tangled.
We made a spool from a tin can
with two large "Milo" lids as
Now for the exciting part. Connect up the antenna, earth and
headphones, and temporarily attach a 100pF capacitor to the "Al"
and "E" terminals with a pair of
short clip leads. Check the coverage
of the top end of the band with the
antenna connected to the "A2" tapping, then the bottom end with the
antenna connected to "A 1 ".
If you are missing some stations
off the top end of the band, you will
need to reduce the tuning
capacitor, and vice-versa. A small
assortment of capacitors will provide quite a variety of values if you
Handy Hints
Hint #1: nail polish is a handy
item in your workshop. It will
secure a pointer to a dial cord,
prevent a knot in a dial cord
from coming undone, or can be
used to lock screws in place.
Nail polish can also be used to
anchor the terminations on
small coils and to permanently
set trimmer capacitors and
potentiometers.
Hint #2: to hold small components while you solder them
together, use a large spring clip
(normally used for holding
papers together). The spring
clip can either be screwed to
your work bench or to a solid
block of wood to stop it. from
moving around.
Hint #3: having trouble getting
a replacement tip for your Tandy, Dick Smith or Scope
temperature-controlled iron?
Many of the tips for these
brands are interchangeable.
Take your old tip with you to
compare it with the new one to
make sure it matches.
OCT0BER1988
59
This view shows how the two ferrite rods are glued to the inside of the
matchbox tray. Any type of round or flat ferrite rod can be used, providing it
is "antenna" grade ferrite .
connect them in series and parallel
combinations.
Once the required capacitance
has been determined, it can be
made permanent, but make sure
you use a low-loss capacitor. A loss
factor of less than .001 % at 1MHz
is desirable. The best capacitors
are polystyrene, silvered mica, or
NPO ceramic types specifically
designed for RF work.
Finishing touches
The ruggedness of your Matchbox Crystal Set can be improved
by giving the lower parts of the
solder lugs, and the area around
them, a thin coating of epoxy. Use
slow-setting Araldite, and spread it
thinly and evenly with a pointy instrument. It will flow out smoothly
and set crystal clear if you warm it
up a little while it is setting. A
warm window sill in the afternoon
sun is ideal.
Put a little of the epoxy oh the
diode and capacitor as well but
don't bother to coat the coil windings - these are best held in place
with a final coat of Satin Estapol.
Before you get out the Estapol,
stick some small pieces of sticky
label material on the matchbox and
label the terminals "A 1" , "A2",
"E", " Phones" and "Phones" with
your neatest writing. Don't use a
spirit-based felt tip pen - use
drawing ink or similar water-based
60
SILICON CHIP
The matchbox crystal set is tuned by
sliding the tray up or down to change
the inductance of the coils. A good
earth connection is vital for correct
operation.
medium. Also, now would be a good
time to draw a tuning scale on the
sliding part of the matchbox, so that
it will be protected under the final
coat of Estapol.
Calibration
As you can see from the
photographs, we managed quite a
comprehensive tuning scale. This
was hand-drawn over the first coat
of Satin Estapol with Rotring drawing ink and a fine pen. This surface
takes ink beautifully if it is pretreated to render it slightly
hydrophilic (ie, to make it attract
water). Just moisten a tissue with
saliva (yes, that's right), rub it all
over the Estapol, and then wipe it
dry.
If the cardboard is darkly coloured, you can stick some white
label material over it, or use one of
the decorative white or silver inks
available at most artists' supply
shops.
Next, consult a list of AM broadcast stations (in any recent DSE
catalog for example) and make a
short list of all the stations in your
area and their frequencies. Log as
many of the stations as you can,
drawing a light pencil line against
the edge of the matchbox for each
one. Draw a base line on the scale
and measure the positions of all the
station lines relative to it.
Next, plot a graph of these
measured distances against the
listed carrier frequency of each
station. Carefully join the points
with a smooth curve. You can now
read off the position of any intermediate frequencies (eg. every
50kHz or lO0kHz), as well as the exact position of any stations which
happen to be too weak to be received from your location.
Transfer all this information with
ruler and pencil onto the sliding
part of the matchbox, and ink it in.
If you make a mistake, it can be
cleaned off with a moistened cotton
bud. Be careful of smudges - the
ink takes a long time to dry on this
surface.
Finally, give both halves of your
crystal set a final coat of Estapol all
over, keeping clear of the exposed
parts of the solder lugs of course.
Operational hints
Although the circuit should be
tuned by moving the ferrite rods in
and out of the top of the matchbox,
you can also tune in the same stations by moving them in and out at
the bottom. The difference here is
that the lower half of the coil will
have a greater inductance, effectively moving up the "A2" tapping.
This will give you more volume,
but less selectivity - the stronger
stations will be noticeably louder
but some of the weaker ones will be
lost altogether. Use whichever setting suits you best.
~
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Constructional Projects
for the Enthusiast
Amateur Radio by
Garry Cratt
The Serviceman's Log
The Way I See It
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ring us on (02) 982 3935 and
quote your Bankcard or Visa
Card number and the expiry
date.
Detach and mail to:
FREEPOST 25
SILICON CHIP PUBLICATIONS
PO BOX 139
COLLAROY BEACH
NSW 2097
I
Signature _ _ _ _ _ _ _ _ Card expiry date_/_/__
• No postage stamp
required in Australia.
0;}/
d'tJ
I
~-------------------------------------~
OCT0BER1988
61
$10 Off Infra-Red
Controller!
Here's great value: you'll save $10
on the superb AEM 240V Infra-Red
Controller. Gives dual action (on/off)
control on any mains device (TV,
lamps, etc etc) from up to 12m away.
Both sections (transmitter and
receiver) supplied (and spare
transmitters are available). Exclusive
DSE kit includes special case &
panel. Cat K-3428
----
WAS $59.95
s49es
Spare
Transmitter To Suit:
sges
Just in case you lose yours - or want
to give control to more
than one person.
Cat K-3429
TV Cro Adaptor
Handy
Zener
Tester
When zeners are new, you can
sometimes read the type number.
Sometimes. When they're a little
older ... And how do you know if
they're zenis goodus or zenis
cactus?
With a Zener diode tester, of course.
And now at this month's bargain
price you can easily afford to have
this valuable bit of test gear on your
shelf. Exclusive to Dick Smith
Electronics (as described in ETI),
includes case and pre-punched front
panel. Cat K-3051
wAs s2s.95
THIS MONTH:
s 1995
What did you do with that old b&w
TV? Still gathering dust in the
corner? Turn it into something useful
- an audio CRO - with this nifty kit.
The display is great for
demonstration and teaching purposes
('cause it's BIG!) or even use as a
legitimate test instrument. Cat K-3060
THIS MONTH ONLY: SAVE $5.00
s29es
Don't Cook
Yourself With
Microwaves!
Microwave ovens: those marvels of
the eighties, can also be downright
dangerous. If yours leaks, it could
cook you instead of the food! Check
out the microwave with this smart
leakage detector. No batteries to 90
flat, so it's virtually fail safe. Positive
safe/unsafe test. Cat K-3095
fVCRo
®'"<at>'·-,.
NORMALLY
$12.95
OCTOBER
sges
Exceptional value: even more kits to save on!
Clllck tlltae Git for VIINI Many llava already
been redaced to low, low prices. Hyot'rt not
s~opping at DSE JGl'rt wuting yHr Ii• Ind
IIIOnty.
1GHz Digital Frequency Meter
3 ranges cover 20Hz fo 100O'MHz!
Everything's included. Cat K-3437
ONLY
IR Remote Control Stereo
Preamp
Cat K-4003
Now Only $199
VHF/UHF TUner Module
To suit Teletext Decoder Cat K-6050
was $19.95
Now $14.95
$199
Low cost 12OW MOSFET
ampllfler module
Just $59.95
Cat K-3443
TUner Module
VK Powem1aster
CAT FAX/Rm Decoder
Cat K-6335 Outstanding Yaluel
Huge 25A peak with suitable transformer!
Short form kit. Cat K-3448
Suits UHFNHF Down Converter
Cat K-6051 Sava $51
$14.95
Link .Your HF Receiver To Your
Computer/
The most versatile counter circuit around!
Up to 2MHz counting speed, clock enable, Save $80!
6m 100 Watt Booster AMP
5-15V operating voltage. Cat K-3451
Yalue $19.95 Cat K-6349 was $279
$99
Fantastic! $199
Appliance Meter
Measures consumption of mains
appliances quickly and easily. Cat K-3453
lncredlble! $19.95
R-L-C Bridge
Measures Unknown Components!
Cat K-3468 Great buyl
$49.95
$39
Graphic Equaliser
10 individually controllable steps in each
stereo channel. Cat K-3500
Bargain!
Low Distortion Audio Oscillator
$99
Cat K-3469
$44.95 With Full Re_pflater Operation!
Explorer UHF Upgrade Kit
TV Pattern Generator
Cat K-3472
Gives your explorer that professional
Sensational Value! $29.95 finish! With S meter and circuitry. About
'13 the original price. Cat K-6302
ONLY$9.95
Optical Motion Detector
$27.95
Cat K-2721
Walkman Amplifier
Short form kit. Cat K-2722
Sensational!
70cm CaAsFET Preamp
$4.95
Muslcolor IV
With masthead mount! Cat K-6309 Was
Combines both colour organ and chaser in
Now $99
$109.95
Now $99 one unit! Cat K-3143
For UHF or VHF Transceivers ..
LEDTacho
13.BV 2A Power Supply
2m GaAsFET Preamp
Cat K-6311 Sava $10
Cat K-3240
$19.95
$39.95 Car Brake-lamp Flasher
Cat K-3245
Just $3.95
JustS89 Motor Cycle Alant1
UHF Wattmeter
Easy to build and fit! Cat K-3249
VHF Power Meter
Cat K-6316 $10 OFF!
VZ-200 Serial Interface
Economy Car Alaffll Mkll
$29.95 Cat K-3253
AM Stereo Decoder
Teletext - without a VCR
Teletext Tuner
Cat K-6319
$19.95
$39.95
Cat K-6312
Lets you connect a modem to your VZ
computer. Cat K-6317
$19.95
Biometal Wire Starting Kit
Get into the world of robotics!
Cat K-7000
Cat K-6306
Reduced to 100$9.95
UHF All Mode Power AMP
50 watts out of just 2 watts drive!
Cat K-6307 $80 Off old Catalogue
Price!
$199
Cat K-6310
$19.95
NowS119.95
Radio Direction Finder
3 Digit Counter Module
Cat K-6345
Great Security!
Bipolar UHF Preamp
Can be built inside your tuner!
Cat K-3415
$19.95
Teletext IR Remote Controller
Suils K-3515 Teletext Decoder.
Yalue PIUS $59.95 Cat K-3425
RF Attenuator Box
Up to 63dB attenuation from 50 to
500MHz! Cat K-6323 was $89.95
Now$59.95
$70 OFF!
HFAmateurRecewerKlt
Cat K-6330 was $369
$29.95
$29.95
lnfrared Remote Control
Repeater
Remote control for your VCR, TV, hi-fi, etc
from any room in the house! Cat K-3426
Slashed to $9.951
Music Generator
Nice Picture: Shame
About The Sound!
·What? You're
Missing Out On
UHF?
Just because you don't want to buy a
new UHF TV? Why should you - this
kit will get you UHF TV on your
current VHF TV - for a tiny fraction
of the price of replacement. Watch
There've been some pretty
SBS and watch their rating soar!
extravagant claims made about
Cat K-3236
negative ions. Even if only a small
percentage are true, we believe a neg
HURRY!
ton generator can be really
$10 OFF
beneficial. This one is completely
safe because it doesn't use a mains
multiplier (operates from a safe plugpack adaptor); is easy to build and,
well, you be the judge. You'll
certainly judge the $5 saving to be
tops! Cat K-3333
Ahh! So Soothing!
ATs5995
WAS $24.95
Own A DFM? Get
More Range!
Digital frequency meter prescaler kit
gives up to 500MHz range from your
current (100MHz or so) meter. Simple
construction, really worth its salt! $1
off our already low low price.
Cat K- 3432
AND IT'S ONLY
s5es
s1ges
8 Channel Infra
Red
Most video recorders do a pretty
good job at handling the video signal
but, oh, the sound! And when you
record off a recording (who'd do
that?) it's usually magnified. Fix up
crook VCR sound with this processor:
gives simulated stereo, 5 band
equaliser allows tailoring the sound
the way YOU want it, and noise filter
virtually eliminates that zzzshj!
Cat K-3422
$10 OFF AT ONLY
s29es
Receiver: Cat K-3
ANOTHER $10 OFF:
NOW ONLY
s29es
WOW! 1/3 OFF NORMAL PRICE SAVE$50
WAS $149 NOW
If It's Real Power
You Want ...
Try this one for size: AEM's 60 watt
mosfet amplifier module. You can use
it for virtually any purpose: PA,
guitar & instrument, even
hi fi (yes, it's that good!)
Delightfully
easy to build
(one PCB construction).
Cat K- 3441
Now$
I
~
What Do You Want Transmlttar: cat K-3434 Normally $169, Now $ 1 4 9
Your Panel Meter Low Cost
Amplify The
To Read?
Amplifier Kit Is
This LCD panel meter module will do
Savings!
Now Real Low
it: make it read virtually anything.
Here's a twenty dollar saving off a
Operates from very wide supply rail
Cost!
hundred watt amplifier for one forty
(uses only a milliamp or so) so you
can operate it from the device itself.
Ideally suited to do-it-yourself
projects where you want really
snazzy metering.
Cat K-3450
Burglary is again
on the increase.
Beat them before
they beat you with
this home alarm kit:
you·11 have a fully
professional system which can
be installed virtually anywhere
(using commonly available detection
sensors) and will scare the pants off
the felon! Cat K-3424
sgg
Normally $59.95
If you need more control than our
simple one channel I/R controller, try
this one: up to eight channels of
control for your stereo, VCR, model
train set, nuclear reactor ... This
value plus kit comes in two parts:
the transmitter and receiver. Build
each bit as you want. And there are
savings on both parts!
Ifs
Alarming -
four megs! Now the translation: our
It was $99.95 in the 1988 catalogue.
100W 2m linear amplifier kit was
Now it's down to an incredible $59!
The low cost amplifier makes a 9.reat $279, this month all you'll pay is
$259! Now get your hand-held up
"first" project - the short form kit is
into the big
all one one PCB, includes all
league!
components, controls, etc but not a
case or transformer (we figured most
Cat K-6313
hobbyists would already have those!) ~~~IU
Cat K-4001~~- .__ ._
==-,.-.,,,,_,
s259
$10 OFF
AT ONLY
s39es
Last Chance For
Glass RTTY!
Stocks of the VZ300 have almost
gone - and so have the RTTY
decoder kits. This month (or until
they're all gone!) save a big one third
off the already drastically reduced
price. We're clearinQ them out to
make way for new ktts - so you reap
the benefit! Cat K-6318
LOW PRICE: $29.95 NOW
LOW LOW PRICE:
s1ges
• NSW • Albury 21 8399 • Bankatown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444
• - • l e (W1rrln91h M1H) 905 0441 • C1mpbelltown (046)27 2199 • Chlllwood Chlae 411 1955
• Chullor1 642 8922 • Gore HIii 439 5311 • Gooford 25 0235 • Hornaby 477 6633 • Liverpool 600 9888
• Maitland 33 7866 • Miranda 525 2722 • Neweaatle 611896 • North Rrde 883855 • Parram1tta 689 2188
• Penrittt(047)32 3400• Railway Squ1re2113777• Sydney City 267 9111 • Tamworth661711 • Wollongong
28 3800 • ACT • Fyshwick 80 4944 • VIC • Ball ■r■t 31 5433 • Bendigo 43 0388 • Box HIii 890 0699
;~l=&:--~:1:; ::J !':I:::::;
;2~::1:~~~:~•
Briab■ne
g~6
4~~='·6:f/05~F~~~=
• lprtngvale 547 0522 •OLD•
City 229 9377 • Buranda 391 6233 • Calms 311 ~5 • Chermalde
359 6255 • Redbank 288 5599 • Rockh■ mpton 27 9644 • SouthPort 32 9863 • Toowoomb■ 38 4300
• Townaville 72 5722 • Underwood341 0844 •SA• Adelaide City 232 1200 • Beverley 3471900 • Sl Marys
277 8977 • Elizabeth 255 6099 • Enfield 260 6088 • WA • Cannington 451 8666 • Frem ■nae 335 9733
• North Perth 328 6944 • Perth City 4813261 • TAS • Hobart 31 0800 •NT• S1\11rt Park 81 1977
ORDER BY PHONE TOLL FREE (008) 22 6610 FOR DSXpress 24 HOUR DESPATCH
6641
Make sure your house is easy to find
LED-LIGHT: THE HOUSE
How would you like a house number
that glows in the dark? Visitors would
no longer have to peer through the murk
with torches to find your abode. Your
house number would welcome them with
a cheery glow.
By JOHN CLARKE & LEO SIMPSON
Most homes are hard enough to
find during the day when you can
see the house numbers but at night
it's a different matter. How many
times have you peered through the
dark trying to find a particular
street number? It's even worse on
wet nights when rain and darkness
combine to make street . numbers
virtually impossible to see, even if
you have torch.
Now, at least as far as your own
home is concerned, you can do
something about it. You can build
the LED-Light, a street number that
glows in the dark. It turns itself on
automatically at dusk and then
turns itself off again about 4.5
hours later.
We've even incorporated an
automatic brightness feature so
that the LEDs (light emitting diodes)
are brightest at dusk and then dim
down significantly so that they are
not too bright on the visitor's eyes.
That might seem like gilding the lily
but when you have upwards of 50
or more LEDs glowing in the dark
they can seem painfully bright. But
more of that later.
The LED-Light is powered from
the mains via a 12V AC plugpack
rated at 300mA or more. Using low
voltage AC means that you could
mount the LED-Light on your letter
box and bury the wires carrying the
12V supply directly beneath the
soil. In some areas, mounting the
LED-Light high up on your home's
front wall might be a better idea, in
case some light-fingered technofreak takes a fancy to it. Either
way, running the wires to it will not
be a problem.
We built our prototype LED-Light
into a standard plastic jiffy box
measuring 198 x 113 x 63mm and
the LEDs are all fitted onto the lid,
as can_ be seen from the illustrations. A light dependent resistor
(LDR) senses whether it is daylight
or not and operates the circuit accordingly. Our prototype was made
for one of our staff members who
lives out in the sticks; hence Lot 14.
The circuit
A light dependent resistor senses the approach of darkness and turns the
LEDs on for a preset time. Make the figures big enough so that they can be
easily seen from the street.
64
SILICON CHIP
You might think we've gone right
over the top with the circuit for the
LED-Light considering that it uses
five ICs, four transistors and five
diodes. Well, they're real cheap ICs
so that is not a problem. The circuit
can drive up to 64 LEDs which is
enough to cater for 4 or 5-digit
street numbers (or Lot or RSD
numbers, if you're out in the bush).
The circuit has three functions:
light sensing, a long interval timer
and a brightness modulator. Light
sensing is provided by the light
dependent resistor LDRl and ICl ;
the long interval timer consists of
IC2 and IC3, while the brightness
modulator is IC5, Q3 and Q4.
IC4 lets the three circuit functions work together, to determine
whether the LEDs are on or off,
bright or dim.
The light dependent resistor
NUMBER THAT GLOWS
01-04
4x1N4002
12VAC FROM
PLUG-PACK
+
+
470
10
16VWr 16VW.:r
~t}' J
.,.
100k
+12V
4xRED LEDS PER ROW
(64 LEDS TOTAL)
16
4011
10 CK
4
8
.,.
.,.
10
+
2
16VW:r
3
+12V
+12V
LDR1
ORP12
.,.
8
56k
IC1
555
2
+
.,.
.,.
15k
B
E~C
VIEWED FROM
BELOW
~-
.,.
470k
10k
.,.
.o~I
.,.
LED-LIGHT HOUSE NUMBER
Fig.I: the circuit can drive up to 64 LEDs which is enough to cater for 4 or 5-digit street numbers. LDRl and ICl
provide the light level sensing, IC2 and IC3 form a long interval timer, and IC5, Q3 and Q4 vary the LED brightness.
LDR1 and a series 33k0 resistor
form a voltage divider which is
monitored by pin 2 (and pin 4) of
IC1, a 555 timer. When LDR1 is exposed to light, its resistance is low
and therefore pins 2 and 4 of IC1
are held high. As the level of illumination decreases (like, when it
gets dark) the resistance of LDR1
increases and so the voltage on pins
2 and 4 begins to fall.
When the voltage on pin 2 drops
to about 4V, IC1 's output at pin 3
goes high. It remains high for as
long as pin 2 is at 4V or below. In
pitch dark, the resistance of LDRt
is likely to be several megohms
which means that pins 2 and 4 of
IC1 will be below 1V.
Pin 3 of IC1 is connected to pins
12 and 13 of NAND gate IC4c and
pin 6 of IC4b, another NAND gate.
NAND gate IC4c functions simply as
an inverter, so that when pin 3 of
IC1 goes high, pin 11 of IC4c goes
low, pulling the reset pin (11) of IC3
low too. This lets the timing interval
start. It also turns on the LEDs via
IC4b, Qt and Q2. We'll come back
to IC4b later.
Long interval timer
IC2 is another 555 timer IC which
is connected to oscillate at about
0.5Hz. This means that it produces
a train of positive pulses at its pin 3;
one pulse every two seconds. These
pulses are fed to the clock input (pin
10) of IC3, a 14-stage divider. This
OCT0BER1988
65
5-second delay set by the 470k0
resistor and 10µF capacitor connected to pins 6 and 7 of IC1.
Brightness modulator
The LEDs are inserted into tight-fitting boles in the lid of the case and wired
in series groups of four. Our prototype used 55 LEDs but you will probably
need a lot less than that for your house number.
As noted above, the brightness of
the LEDs is varied depending on
whether it is dusk or pitch dark. At
dusk, the LEDs are at maximum
brightness and as it gets darker,
they are dimmed down significantly. This function is performed by
IC5a, a dual operational amplifier.
IC5a monitors the voltage across
LDR1 and its output at pin 1 is used
to vary the voltage at pin 5 of IC5b
which operates as a Schmitt trigger
oscillator. It runs at up to about
2kHz (depending on the degree of
darkness) and its pulse output
drives transistor Q3 which drives
Q4 and the LEDs. Thus IC5 controls
the duty cycle of the LEDs.
At dusk, when the LEDs are
brightest, they are on 100% of the
time. When it is pitch dark, they are
on about 50% of the time. This is
when they are being pulsed on and
off at about 2kHz. Transistor Q4
switches on and off the positive
supply to the LEDs and is driven by
Q3 via oscillator IC5b.
Power supply
Power for the LED Light is derived from a 12VAC plugpack. This
feeds a bridge rectifier consisting
of diodes Dl to D4. The rectifier
output is filtered with a 1000µF
capacitor to supply the LEDs.
For the remaining circuit, the
filtered rectifier output is regulated
with a 12V 1W zener diode, with
further filtering provided by a
4,70µF capacitor. The 10µF capacitor is for extra supply bypassing adjacent to the ICs.
The light dependent resistor (LDR) is mounted at full lead length on the PCB.
When the PCB is later clipped into the place, the leads of the LDR are bent so
that its face protrudes through a hole in the side of the box.
divides the incoming frequency by
214 or 16,384. The result is that
after about 4 hours 30 minutes the
output at pin 3 (Q14) of IC3 goes
high.
The signal from pin 3 ofIC3 is fed
to NAND gate IC4a, connected as an
inverter. So when pin 3 of IC3 goes
high, the output of IC4a, pin 3, goes
low. This drives pin 5 of NAND gate
IC4b and thereby turns off Qt, Q2
66
SILICON CHIP
and the LED display.
IC4a also drives pin 4 of IC2
which then inhibits any further
oscillation.
The output of IC3 stays high until
next morning when light hits LDR1
and IC1 delivers a reset pulse to pin
11 (ofIC3).
IC1 will not respond immediately
if car headlights strike LDR1 for &
few seconds. This is because of the
Construction
We built our LED-Light into a
plastic utility case measuring 198 x
113 x 63mm. All the circuit components, with the exception of the
LEDs, are mounted on a printed circuit board coded SC03-1-0988-1
and measuring 104 x 103mm.
Assembly of the PCB is a simple
matter of inserting the parts into
the board and then soldering."Begin
by installing the wire links,
resistors and diodes. Then do the
capacitors and transistors.
PARTS LIST
1 plastic utility case, 198 x
113 x 63mm
1 PCB coded SC03-1 -0988-1 ,
104 x 103mm
1 12VAC 1 A plug pack
64 5mm red LEDs (see text)
1 ORP12 cadmium sulphide
cell (LDR1)
Semiconductors
1 4020 14-stage ripple carry
binary counter
1 4011 quad 2 input NAND
gate
2 555 timers
1 LM358 dual op amp
1 BC558 PNP transistor
1 BC548 NPN transistor
1 BC338 NPN transistor
1 BC328 PNP transistor
4 1 N4002 1 A diodes
1 1 2V 1W zener diode
Fig.2: here's how to mount the parts on the PCB. Because the LEDs
are wired in groups of four, you might not need all of the 4 700
resistors shown. Note that the corresponding 4700 resistor must be
increased to 8200 for a one or two-LED set, as outlined in the text.
Note that the diodes, transistors,
electrolytic capacitors and ICs
must be oriented as shown on the
overlay diagram. Don't bend the
leads of the 1W zener diode, D5,
close to its body to fit it into the
holes on the board. This component
can get warm depending on
whether the LEDs are off (which
means that the supply is lightly
loaded) and whether the mains
voltage is high.
To enable D5 to cope with expansion when it does get warm, install
it with an expansion loop at cine
end.
The light dependent resistor
LDR1 is soldered into circuit with
its leads sufficiently long so that it
can be mounted with its face protruding from the the side of the box.
Checking the circuit
Before wiring all the LEDs into
the circuit and installing the unit in
the box, it is a good idea to check
that the circuit board functions properly. If you check it out now it will
be much easier than trying to
troubleshoot it later. So leave off
the rainbow cable connecting the
LEDs until the following checkout
procedure has been done.
First check that all solder joints
on the board are up to scratch and
that there are no solder bridges between tracks or breaks in the tracks
themselves. Then connect a 12V AC
or DC plugpack capable of delivering 300 milliamps or more. You can
use a 12V bench power supply if
you like, as it will work just as well.
If you are using a bench supply, adjust it to deliver about 14 volts
which will cater for the voltage
drop in the diode bridge (about 1.2
volts).
Now use your multimeter to
check voltages around the circuit.
D5 should have close to 12 volts DC
across it. With your multimeter's
negative lead on the negative end of
D5, check that + 12V appears at
pin 8 of ICs 1, 2 and 5, at pin 14 of
IC4, at pin 16 of IC3 and at the emitter lead of Qt.
Now cover LDR1 to prevent it being exposed to light. If you have an
analog multimeter (or a digital
multimeter with an analog scale)
you should be able to check that IC1
is oscillating at about 0.5Hz. Leave
the meter set to the same DC
voltage scale and place the positive
Capacitors
1 1OOOµF 25VW PC
electrolytic
1 4 70µF 16VW PC electrolytic
3 1 OµF 16VW PC electrolytic
1 .01 µF metallised polyester
Resistors (0.25W, 5%)
2 X 470k0, 4 X 100k0, 1 X
56k0, 1 x 33k0, 1 x 15k0, 1 x
1 OkO, 2 x 5.6k0, 3 x 1 kO, 18 x
4700, 1 x 330 0 .5W
Miscellaneous
Solder, tinned copper wire,
300mm of 1 8-way rainbow
cable.
lead on pin 3 of IC1. The pointer
should flick up the scale to 12V
about once every two seconds.
You check the frequency divider
operation of IC3 in a similar manner. Place the negative lead on each
output in turn. Pin 9 (the Qt output)
should rise to 12V every four
seconds or so; pin 7, every 32
seconds; and pin 5, every 64
seconds.
You ·could check every available
divider stage (not all stages have
pin outputs) in this way if you
wanted to but it would be very timeconsuming and a fairly pointless exercise. Once you've demonstrated
that the early divider stages of IC3
are working you can be sure it is
OK.
OCTOBER 1988
67
Note that IC2 will oscillate
whether or not LDR1 is exposed to
light but IC3 will not work unless
LDR1 is covered. This is because
IC3's reset input, pin 11, is high (ie,
at + 12V). You can check the action
of LDR1, IC1 and IC4 by covering
and uncovering LDRt. With LDR1
covered, pin 3 of IC3 and pins 12
and 13 of IC4 should be high. Pin 11
of IC4 and IC3 should be low. Five
seconds after LDR1 is uncovered,
all these points should change
state;, ie, pin 3 of IC3 and pins 12
and 13 of IC4 should go low and so
on.
Having got this far, we've practically checked the whole circuit.
Now wire one LED and a 10k0
resistor in series between one of
the 4700 resistors and the common
line from the collector of Q5 (this
line is along one edge of the board,
adjacent to the row of 4700
resistors). Note that the LED comes
on when LDR1 is covered and goes
out five seconds after it is uncovered. Good. Its brightness
should also visibly dim as LDR1 is
completely covered.
I
OOOIMIODD-GOOOOD-GO
.,,
I
Fig.3: this is the full size pattern for the printed circuit board.
Wiring the LEDs
The LEDs are mounted on the lid
of the case and can be arranged in
any manner required. Up to 64
LEDs can be accommodated. We
arranged the LEDs on our prototype
close together but they can be spaced further apart for better
readability at a distance.
The LEDs are inserted into tightfitting holes in the lid. Wire the
LEDs in series in sets of four with
the anode of one connected to the
cathode of another. If the last set of
LEDs is not four, then the series
resistor supplying that set will need
to be altered.
For three LEDs, the resistor can
remain at 4700, for two and one
LED sets, use an 8200 resistor.
You can run the wires from the
LEDs to the PCB using multi-way
rainbow cable.
A hole is required in the base of
the case for leads from the 12VAC
plugpack and another close-fitting
hole is needed for LDR1.
The unit is now ready for final
testing. Connect up the power and
test that the voltage across the
zener diode is about 12V. Now test
68
SILICON CHIP
Stout pieces of tinned copper wire can be used to connect the commoned anodes
of the LEDs together. Keep the wiring tidy to avoid confusion.
that the LEDs light when LDR1 is
covered. They should remain lit for
five seconds after LDR1 is again
exposed.
Finally, the case can be weatherproofed using silicone sealant over
the cord entry and around the
edges of the lid.
Delete options
Just like some new cars have
"delete" options then so has this
circuit. If you are not buying the kit
you can save a few dollars by leaving out the automatic brightness
feature. To do this, delete IC5, transistors Q3 and Q4 and the 10
resistors and .OlµF capacitor
associated with these active components. A link should be wired in
place of the collector and emitter
leads to Q4.
~
Nicad ~
Battery
-.!.!~~-=- •••
Charger
a
(NJ{f.rrl}
rans
Mein, powered.
ch•rges 6 x AA or AAA
High Qunlity
from C.I.C. Co.
s19 80
betterie, i n 14-16 hr,,
vith LED indica1or>.
ca1 02-2012
a..~
for rndlo control
Tamiya curs etc.
Plug-1n replacement i,
Cat
1300mAH end et thl, price,
02-1090 \JOU could efford 2 e, ,pere,.
Recommended charging I 30mA 1Shrs.
s20
10-49$16 eo
50-99 $14 eo
100• $ 12 eo
7.2V mead
- ~ Battery Pack
$49
Toi won Ltd.
•
3'" ( 00mm)
3" ( 80mm)
5" ( 120mm)
5" ( 120mm)
EA
Buy No;,,,
Cet 06 - 1o 19
Cel 06-1020
Cet 06· 1029
Cet 06 - 1030
11 sv AC
240¥ AC
11 5V AC
240¥ AC
3.5mm mono~
5(0)(C[)([E7]"5 ~
The~e normally , e l l ~
for 40 cents! But
now you con buy
them for;-
1-19 ...... 10C eo Cet 19-8000
20-99. . eceo 100• ...
see,
ALARm
7.2V mead Chargers
festchargein 15mins ~
or trickle cherge from t' .i. :'<at>:•
cer battery.
..,... ~ _
St11ndord Quick
Churger.. .... $39 ~
-~ '
Deluxe Quick
·
:
Ch11rger. ..... $ 95
Duel meter,, electronic timer control,
S0UilD
sqq
01:i'J22
Supplies 3/6/9V de from lii:ihter skt
for CD player or Wei kmen caooet1e &
inbuilt FM converter transmits sound
A
24V AC or DC
$
Engl ish Chloride Gent
15 0mAcu rr ent
Ca l 03-2019
1
~
7 50
■
I 0• $6.75 ee
,
□;~•
WOOFERS
•
4• ZSW 80Hz-7KHz 19-6080 ... $ 22
6" 50W 60Hz·7KHz 19-6002 ... $51
B" 75W 50Hz-7KHz 19-6084 ... $ 49
Buy 10 less 10:11
~
24V AC ..... . 19-4091
4.90
24V DC .. ..... 19·4092 ..
7.50
110V AC .. .. . 19-4093
2.50
240V AC. 19-4094 .... .. . 6.50
I" Dome Tweet
55W 1,2KHz-20KHz
Suit honeycomb speoke
Weter resist11nt
hi-fi ,peakers,
75W RMS pwer,
SOHz-5KHz sn
$36ea
NE'w'
33
$
Redio control,
e~dn~~~:r:;:,
pr og remmeble code,
~
01 -0910
s89
r enge 12- 15 me tre,.
RELAY
contects
.,,,
5A
Each
Cat 19-4076
$3.30
Single pole, I K
ohms, new, best
quoli ty.
Electrothermol
brand.
$;
0
~5
s2ea
1 O+ $1.80
Cot . 19- 4094
TV TRANSw:1
AUDIO/VIDEO
Send audio end video
signal• to TV oet(o)
""ithin 30m renge on
":'"'.::. ·; ..·--; · ,.
UHf Ch36, No di reel
""!ring_ needed so use
'w'lth video camera,
too! 9V be1t or 240VAC.
$8 g
•
Cot 04-1155
s44
Motor-drive n reflecting
mirror fleshes up to
150/mi nute, orange or
blue lens. 'w'eterproof,
for to'w' trucks, 'w'erning
light etc. 12V DC 1A
c~to1-s31s
Iii
No - Name Floppy Disks
but '100%
guaranteed I
fomous maker no lebel
diskettes 1n ple1n Yh1te
envelope, 'w'ith 'wlrite-on stickv leb,h .
5J{DS:DD ..... s16.9s
Cet50·1013
ULTRASONIC
+ RADIO KEY
~
-~~
-11
Redic control ON/OH. , ~
penic elerm button,
•1.
current door ,en,i ng,
interior motion detector,
inbuilt ,iren, del•~. re,et, $220
leteot burgler- proof deoign 19-5252
CAR ALARffi
12v /
- FLASHING
~
/
Cat
,
/
\
01-5179
RED LIGHT
Connect, to ignition
,,,,,itch - ectivaled only
Yheniq nit ioni,offllt',
A go a great deterrent even if
you don t ll8ve en elerm.
$1 -,.
JRCKPOT: ~:~~:\~::,
Box
Ca1 16- 3407
Each
$6-85
12V ROTRTinG
FLASH LRffiP
STROBE
FLHSHER
SWITCH
12Vdc DPST
Tekemisswe
VB Ser-ies
25W 325Hz-lSKHZ
15 PIN Femule
New DIGITHL
REffiOTE
~\. CHR HLHRffi
SOLENOIDS
5" Honeycomb
Cone Mid-ran
Sealed beck, metches el
honeycomb cone Cit
'w'oofers.
19-6D
~
~
f° II;)
ca1 16-3406
9P pluy to 25P skt .. Cat 16 - 3445
9P skt lo 25P plug .. Cat 16-3447
0~DT Ei~c ~"
HIGH QUALITY
}:·
~~~~tmtg
beoe
CetOl-5312
NON-RESETTABLE
2 ◄ V DC .. $5.50 ee
24 V DC Chassis 19-5011 ...$6.SOea
11 O VAC Chaooi, 19-5012 ... $ 5.00ea
220 V AC Chaosi o 19-5013 ... $ 5 . 95 ea
Bug 1 0+ Less 1 0\11
HEAVY DUTY
-
--~
pin size connector.
15 PIN Mule
Cat 01-09'17
11
4/6/8" Honeycomb Cone
~
~ri:R5~
euto reoet, 12Vdc oper.
c-1
TYPE CONNECTORS
12V RED. HLUE.
ORANGE.
IDEAL FOR ALARMS etc .
•Build your o'w'n system at 1o'w' cost I Hu
25 ea
siren. entry/exit delay, S
)!~~~m~
into car redio for high quality. ou1pu1.
Reduce cone breakup,
excellent be,, sound,
RMS power ret1 ng, .
All 8 ohms i mpedence .
LOOK AT OUR ADVERT
HERE EVERY MONTH!
22K end - of-line reoiotoro, N.0/N.C .
i notentenddeley, Inbuilt
Extro loud
08 9
AsusedonnewlBM
type computer, etc .
Htwe 15 pin, in 9
in SILICON CHIP
~ CONTROL
~ MODULE
t
FEEDER~
for CD plnyers
·
Finger Guord s now ovoiloble!
3 ' (80mm) $1 SO ee Cot 06-1022
5" ( 120mm) $1 .50 ee Cot 06· 1032
NEW
We're GLAD
to be here
no 6
, Semiconductor,
•
•
•
•
•
SY1tches
(lectrol ytic,
Potentiometer,
Connector,
Se mple,
cat 24- 0020 s15 • ~i;~t~~t:1~~~-,
:tro
$l5 .95perl00di,ko
9 Pin DB to 25 Pin DB
Momentory type
Cat 01-0455
Push ON-Push OFF$l
Cat 01-0457
each
VIDEO
LIGHT
12V 100 Watt
For ell video camera
lighting 'w'ith po'w'er
peck end charger.
$229.oo
Day/Night
PR.INTER.
BUFFER. ·; .
SWITCH
•.
SEnSOR
SWITCH
Photocell ;,,ilh 240V AC
Z56K)$2951ncl
switcheble to dueil out-
tex
puts vith poverful copy $360 + 1ex
fecility . Eech buffer cen use the full
Z56K RAM vhile the other i, not in
use . You can copy on one buffer 'W'hile
the other ls receiving inout or orin1i ng, or copy both et the ,eme time to
2 different pri ntero . Higheot Quelity
end fully guerenteed . 200xl45x40mm
Buffer :
De1e:
Pover :
256K or 2x12BK o1orege
4K bytes/second maximum
Z40Yec or 9Vdc •1 500mA
Macintosh®
CABLES
Re91st,r•d trad, rn~rk of Appl, Compu tpr-
~
:~~ :~ ;:i~t;r m:~ c=)
( lmege""riter I, ll or some other,)
o·•
$10.95
Pl u, to printer
$10. 95 ·; · •
(lmege'w'riter I, II or ,ome others)
Plu,tomode m
•
HALOGEN
CENTRONICS P A R - L L E L
ca104-1592
z buffers (total
2 95
Custom m11de to order here ; n Oz
relay s'w'itching for home,,
security, neon siqns etc
Cat 04-0110 Weterproof for outdoor,.
$16.50
CASSETTE SALVAGE and
REPAIR KIT
CASSETTE
Complete ,et of cassette
perb'W'ithsplicing bar
end tape end bh1des .
Cet 01-0430
REPAIR KIT
r:;..i
rfiiil
~
"ij
~
$2.95Eech ~
TELEPHONE
EXTENSION
BELL
10 Metre leed for
remote locat ions
'w'ith \JS type plug.
Aust pl ug -8depter
on l y $5.52 eo
$22.so
Cot 24-3001
Interesting circuit ideas which we have checked but not built and tested. Contributions from
readers are welcome and will be paid for at standard rates.
Off peak indicator
for hot water systems
How many times have you run
out of hot water from your off-peak
hot water system? It most commonly happens when the rellies
(relatives) are staying and use all
the hot water before you even get
up, leaving no hot water for the
most important shower of the day
- yours.
This circuit provides a visual indication when the hot water system
is switched on so you have some
idea when it will be safe to venture
under the shower head. It monitors
for the presence of control tones
on the 240V mains and switches on
a LED.
The circuit is powered by a
9V AC or 12VAC plugpack which
picks up the control tones. Diode Dl
half wave rectifies the 12.6VAC
from the transformer and the
resulting DC is filtered using a
470µF capacitor. A 7808 regulator
sets the voltage at 8V.
Control tones picked up by the
+8V
9-12V AC
PLUGPACK
+
IC2
70
SILICON CHIP
DUT.,_8_~
NE567
22k
1k
0.33'+
transformer are coupled via a
.0039µF capacitor and a 47k0
resistor to the input of ICl. This is a
non-inverting amplifier with its gain
set by the 22k0 and lkO feedback
resistors at pin 2. The amplifier is
biased to the half supply point by
the two lOkO resistors connected to
pin 3.
Both the .0039µF input capacitor
and the 0.33µF feedback capacitor
filter out the 50Hz signal from the
mains supply but allow the lkHz
control tones to pass.
Output from the amplifier connects to the input of IC2, an NE567
phase locked loop. This provides a
low output from pin 8 whenever the
IC detects or locks onto a set frequency. In this circuit, the lock frequency is lkHz as set by the .039µF
capacitor and 27k0 resistor at pin
6.
When control tones are present,
the signal is amplified by ICl and
detected by IC2. The resultant low
output from pin 8 of IC2 drives the
off peak indicator LED.
r-----------------+---..--+---+15V
Audio overload
detector
Here is a circuit which indicates
whenever an audio signal exceeds
a specified threshold value. It is
useful to indicate clipping levels on
a power amplifier, mixer or
microphone amplifier. It indicates
the overload by flashing a LED for
about 200ms for each overload
peak.
The circuit comprises three ICs.
ICl is used as a precision full wave
rectifier, IC2 as a comparator and
IC3 as a timer.
The precision rectifier uses a
CA3140 connected as an inverting
amplifier. A diode is connected in
series with the output and within
the feedback loop. The CA3140 is
specified here because its inputs
3 IN
1.5k
220k
IC3
555
INPUT
.,.
i.,.
OVERLOAD
LED
1M
can be pulled below its negative
supply line (pin 4).
Opei'ation is as follows: when the
input goes low, ICl functions as an
inverting amplifier with a gain of
- 0.5. Diode Dl is forward biased.
When the input signal goes positive,
the output of ICl goes to ground and
Dl is reverse biased. The signal is
then passed to the output via the
3k0 and 1.5k0 resistors.
.,.
In this case, the op amp is effectively out of circuit and the output
signal is half the input signal. So the
CA3140 in conjunction with diode
Dl provides full wave rectification
and a gain of 0.5.
Op amp IC2 compares the output
voltage from the precision rectifier
with the reference voltage set by
trimpot VRl. When the rectifier
voltage exceeds this reference
1k
10k
MAXIMUM
ADJUST
IC1
555
VR2
1M
10
RESET
.,.
4.7
+
K
4
013
680k
01
8C548
014
2 0.120min
3
0-240min _
S
2
.,.
.
16VW.r-
Long interval timer
Many applications call for
time intervals which are too long
for a standard 555 timer circuit.
In practical terms, it is limited by
the leakage of normal electrolytic capacitors to time intervals of no more than about 15
minutes.
For longer intervals, you need
to resort to a long interval timer
such as the XR2240 or the circuit
presented here. It uses a 555
timer to drive a 4020 14-stage
ripple counter.
ICl is connected as an astable
timer (ie, it oscillates continuous-
voltage the output of IC2 goes low
and triggers a 555 timer, IC3. The
555 timer is connected as a
monostable so that the output remains high for about zooms each
time it is triggered. The zooms
period is set by the 220kn resistor
and lµF capacitor at pins 6 and 7.
The output of the 555 at pin 3
drives the LED via a lkO resistor.
The input voltage to the circuit
should be limited to an absolute
maximum of 15 volts peak-to-peak.
Note that the input impedance of
the circuit is rather low at 3k0. To
function properly, the circuit
should be driven by a low impedance source.
Subscribers
Are you about to change your address? Please advise us by the
middle of the month to ensure
that your next issue arrives at
your new address.
ly). Its output is divided by IC2,
the 4020, with division ratios set
by switch S2. The division ratios
are 2048 at pin 15, 4096 at pin 1,
8192 at pin 2 and 16,384 at pin 3.
To obtain a 30 minute period, as
set by S2, ICl is set to oscillate at
1.13Hz by adjusting trimpot VR3.
With this setting, S2 can also
give time periods of 60 minutes,
120 minutes and 240 minutes.
The high output from S2 is used
to turn on Q2 and the associated
relay. The output is also fed back
to Ql which switches on and
pulls pin 4 of ICl low, stopping it
from oscillating. So once the
selected time period has been
reached, the output at S2 stays
high and ICl does not oscillate.
S1 provides a reset function.
When S1 is closed, pin 11 of IC2
is pulled high. This resets all its
outputs low. This turns off Ql
and allows ICl to oscillate.
The O. lµF capacitor connected to pin 11 also provides a
"power on" reset function.
When power is first applied, the
O. lµF capacitor is effectively a
short circuit so that pin 11 is
pulled high for a short period, to
allow reset to occur.
Trimpots VRl and VR2 are
provided for fine adjustment of
the time period.
SAFETY WATCH
Safety Watch will be an occasional feature in SILICON
CHIP drawing attention to issues of electrical safety
in the workshop and home.
Electric shavers
should be checked
Electric shavers are so reliable that it is easy to become
blase. The power cord should be
very carefully examined from
time to time to check for any
cracks in the insulation. After
all, remember that these appliances are used in wet environments and so the possibility
of a shock from a cracked power
cord is high. If the cord shorts,
there is also the danger of burns.
In one case, the power cord
was found to have a serious
break in the insulation of the
removeable 2-pin female plug.
The cord was normally wrapped
around the shaver after each use
and so the crack was hidden in a
permanent bend in the reinforced section of the plug.
There is no satisfactory repair
for this situation. Do not attempt
to tape it over as further flexing
will lead to breaks in the insulation of both conductors and
ultimately they will short. The
cord must be replaced and the
faulty cord disposed of.
The same comments apply to
other appliances which use
removeable cords; eg, cassette
players and radios.
OCT0BER1988
71
Brand new ~
240V50Hz Synchronous
Motors
CLEAR STYRENE
UTILITY BOX
This water clear box consists of two
matching halves . Overall dimensions
(both halves) are 63(L) x 40(W) x
25(D)mm. The boxes are Ideal for
storing small components or housing
ve,y small projects. As they are clear
they would, for example, make a good
housing for a photo llash trigger.
Low cost and limited quantities.
We have made a SCOOP PURCHASE
of Double Pole Squirrel Cage motors
with rubber shock moue.:lng plate
(which can be removed if necessary.)
The motor is supplied with an on-off
switch (also removable) and features a
4mm diametm hard steel drive shaft,
21 mm long (with mounting plate
removed).
These motors are Ideal for fans or when
reduced, in applications requiring a
Cat.HB-6065 4
~~•,":,r f;:,lii. i.
•
' / • 4
">
:,1., r, :
~ ..
for $1.00
iflRlU/fJ©
~~!M~/fJ ifO©!M
:B~c;.-~N"
•
BICENTENNIAL
LIGHTS
WHAT A FLOP!
We really believed everybody would jump
at the chance to illuminate their gardens.
But nol So, they have got to go. 12 volt
operated, 6 metres long, 20 lamps. See
our ads July for full details.
WAS$49.95
Out they go at
$29.95
1/2ANRCA
LEAD?
Well, not quite. These are a stereo lead,
(figure 8 shielded) with two RCA plugs
on one end and tinned stripped leads on
the other. Leads with 2 RCA plugs on
both ends sell for $4.95.
Cat. WA-1040
ONLY$1.95
10+ $1.75 each
RUGt SAVINGS
41®® mm.W
G JENJEIB.&i.IL
JFUJIBJF(O)§JE
A UJII» II(0) A.IMCJF
IffiihlB?.<GAIIN
Completely built, this module measures
63 x 35mm, has a high input irrpedance
and high gain. Runs on 9V and requires
a 15 ohm load. Supplied with full specs
and data. Made In England!
Cat. M-0292
ONLY$3.95
10+ $3.50 each
We have a small quantity of 15 ohm 5" x
4" speakers to suit. Otherwise just use
two 8 ohm speakers in series.
Cat. AS-3013
$3.95
ZENER DIODE
BARGAINS
BARGAIN No.1
1 watt Pkt 25
12 volt
Cat. ZR-1370
$2.95 SAVE $5.80
BARGAIN No.2 6 volt
500mW Pkt 50
Cat. ZR-1372
$2.50 SAVE $10
NORMALL V $29.95
NOW
Tonearm cable. Yes, we've finally
n able to locate a small quantity of
core tonearm cable. This cable is
· led together and total diameter is
$14.95
CLOCK MOVEMENT
WITH BUILT-IN
PENDULUM DRIVER
This module measures 87mm long x 55 wide x 35mm
deep and uses 1 x AA battery. Clock movement Is
supplied with 3 sets of hands, and pendulum Is a
suspended arm within the module which swings
back and forth. A suitable pendulum can be
attached to the bottom of the arm.
Flt your own custom dock face.
Great for novel applications.
WAS $22.95
Cat. XC-0103
NOW $16
· · . SAVE $6.
TRANSFORMER
BARGAIN
ULTRA THIN
SHIELDED CABLE
This 100VA unit measuring 1D0(H) x 90(
x 75(D)mm features a rrounting bracket
that enables you to mount rt vertical or on
its side. Primary winding is tapped from
200-240 volts. Secondaries are 1 x 16V.
1 x 12V. Both would be minimum 2 amps.
Cat. MM-1812
Qualtty English made shielded cable
with a total diameter of 1mm. Ideal for
screened wiring in small spaces I
Packet 5 metres
WAS $14 SAVE $5
NOW
$9
Jaycar 12V/ .,,-1>
300VA SINE ~~
WAVE Inverter
NOW AVAILABLE
wave• and this unit gives a genuine
300VA, not less.
The Jaycar Sine Wave Inverter has
tremendous surge capab ilny. It will, for
example, stan a small refrigerator.
We are very proud ol this Aust ralian
made and designed product. The price,
however, may have to rise soon, so
· hurry!
Cat. Ml-5020
$399
SALE
01
I/;
~
;;;;;; ,._ (~
"' 'I!)
Chassis mount socket on bakelite with
. ____________
Features Mylar drivers, sponge earpads,
metal 3.5mm stereo plug. Cat. AA-202 1
WAS $29.50
Cat. WB -2310
NOW $17.95 SAVE39%
SA880
Mylar drivers, freq . repon se
GREEN RECTANGULAR
20Hz-25kHz. Quality muff pads .
LED BARGAIN
Cat. AA-2022
NORMALLY 40C each
WAS $39.50
OCTOBER PRICE
1-10
20eea
11-99
16eea
100-999 14e ea
1000+
12eea
including taxi
Cat. ZD-1765
NOW $24.50
~~
, .
OCTOBER SPECIAL #
Cat. TH-189 1
~
fl//1)~
1
fi (
~
1
125mm flush cutters
Cat. TH-1892
/
$7.95
-~
SAVE$2
POINTED TWEEZERS
/
/
SAVE $1
/
1
11'
QN_L ~ 1.95
tSi\l""""ll;i(~f)
/1
t__lfv®~~
'
1
-'
~
economy plug .
NOW $39.50
SAVE 34°/4
For full details see our catalogue.
SAVE 38%
~
..-~ "
JUST ARRIVED
QUALITY NIPPERS
$7.95
SAVE$2
WAS$59.50
-«\._~~
---------■.,,,,"fiW!i.,1/ 211%11~7!:.■.. Cat. TH-1765
RCA
SOCKET
Top of the range, excellent sound.
Qualtty phones. Cat. AA-2023
ONLY $2.50
130mm wire nippers
Now you can enjoy SIN E WAVE power
at AROUND 85% EFFICIENCY for
much the same cost as inferior square
HEADPHONES
SA888
Similar to those used on
those expensive gold audio
leads. Clearly marked in red
or black.
RED
Cat. PP-0236
BLACK
Cat. PP-0237
Now ~ou can have _all the benefits of
t~~; g~e~r ~~:sJ;;~~~~e~\mport is
durable, stylish and compact, measur-
$3.50 ea
1O+ $3.20 each
WIRE WRAP KYNAR
WIRE ON SPOOLS
We have been after this for years, and
have finally lound it. It's high quality
SILVER PLATED (other companies sell
wire wh ich isn ot silver pl<)ted) on 50 foot
spools. Available in 4 colours.
RED
Cat. WW-4340
BLACK
Cat. WW-4341
BLUE
Cat. WW-4342
ing only 110mm in total length. It simply
plugs directly into the cigarette lighter
socKet in your car. lt can generate large
amounts of negative ions 1or purifying
air , and scme ozone for eliminating
odour.
Jaycar's direct importing cuts out the
middle man and saves you money.
SPECIAL INTRODUCTORY
OFFER ONLY $34.95
Cat. YX-2910
/
ONL'?$s."so/ ~
NORMALLY 36i ea 1/2 PRICE ;- · _· _' _
10 FOR $1 SAVE 73%
PLASTIC · W { ·-';' ·
per reel
1/2 PRICE
FEET
-~ ~ ..Th•a•t·s•o•nly•1•3•ep•e•rf•oo•tl---CIGARETTE PLUG amps,
Ideal for turntables, speakers, large
etc. Easy mounting wtth one 4 mm
USUALLY $1 .20
OCTOBER SPECIAL
60i ea
diameter bolt or self tapper. Diameter
35mm at base.
USUALLY SSC ea
ocTOBER ONLY
1O+ 35C ea
BA CK AGAIN!
White Cone
Midrange
Our rrost popular midrange. Large sealed
back wtth extra clear crsip midrange.
110mm, 80 watts RMS power handling,
95dB sensitivtty, 10oz magnet, freq ."resp.
31 Hz - 7kHz, resonant freq. 310Hz.
'
Cat. CM-2080
1986 PR ICE eat your heart out Dickll
ONLY $22.50
Polypropylene
Cone Midrange
We've been able to lower our price on our
high power midrange. Black Poly cone.
Huge 10oz magnet. 5" diameter.
Specifications:
Power handling
100 watts RMS
system
Resonant Freq.
570Hz
Sensitivity 96dB
Freq. Rasp.
570Hz - 7kHz
Cat. CM-2085
$24.95 r . ; . . ; ~ ~
40i each
Cat. HP-0830
Build ·;our own, or use for spares.
Oualtty Japanese made DPDT push on/
push off switch rated at 125V 3 amp.
Complete with black round knob. These
are commonly used as on!off power
switches fo r mains products, and normally
cost about $4 • $5.
Javcar has a quantity availam:e for only
$t.95.
Cat. SP-0730
$1.95 ea
WAS
$6.95
NOW
$4.95
SAVE
$2
Cat. KJ-7100
10+ $1.75 ea
12V CAR ANALOGUE
CLOCK MOVEMENT
"P<at> <at>[}{][Ml ~ □ L'Zl
®Wl~©~[Q) ©<at>~~
FOR THE PRICE OF
ECONOMY COAX
Yes. for a short time only,
you can purchase HIGH
QUALITY air spaced 75
ohm coax for the same
price as our economy
75 ohm cable.
Normally tts $1.20 per
metre, but you can buy it
for only 80e per metre.
Or, ~ you buy 50 metres
or more, it's only 60e metre.
That's half price!
ao;~;tre
50m or more
60t metre
~
u
MASSIVE SCOOP
PURCHASE!
Grab a quartz crystal car clock wtth a
set of automotive style hands at a
price that will astonish you I Once
a'gain our suppliers huge loss is your
gain! Convert that broken/unreliable or
inaccurate mechanical clock in your
car to space age precision I
ade in West Germany by VDO, the
odule measures roughly 45 x 38 x 40
ep. The compact size virtual ly
sures that nwill fit in any space!
ntit strict! limited!
A JAYCAR/SILICON CHIP EXCLUSIVE KIT
.P LASMA DISCHARGE DISPLAY
Ref: Silicon Chip August 1988
Jaycar and Silicon Chip have combined
to produce a low cost but spectacular
plasma discharge display. At the heart of
the kit is an exclusive rare-earth gas
chamber specially made for this kit.
This gas chamber is specifically designed
to produce a spectacular red, violet and
orange continuously moving light show.
It's like nothing on earth I You will absolutely
amaze your friends and family.
The Jaycar kit of this project includes the
rar&-earth chamber, mounting plinth, EHT
transformer and inverter electronics.
A 2-3 arrp 12V DC power supply is required.
(A battery charger is ideal).
You can have this 9Xclusive kit, complete for
the amaz ing low price of only $2991
Call in to one of our stores for a demol
Cat. KC-5035
SA VE $26.50 on
500MHz Frequency
Counter Kit
Ref: EA Dec 81/Feb 82
For October only you can purchase the
50MHz frequency counter kit at $169.50
and for an extra $20 we will supply the
500M Hz prescaler (worth $46.50). This
represents excellent value.
Counter Kit KA-1390 $169.50
Prescaler KA 1392 $46.50
NORMALLY $216.0
BUY BOTH FOR
ONLY $189.50
SAVE $26.50 ~r'
l)l(flAtFREJJJJfNCY/PfRIODMiTtf<
NEW LOW PRICE $229 "'"'"'
SAVE $70 Saving
s made because of mass
production of this sensational product!
'(•
NOW $79
July/Aug
MODEM KJT
Normal Price $379.00
Power Supply $49.95
$428.95
$199
• SAVE AN AMAZING $22
BUY BOTH FOR ONLY
Cat. KE-4715/4716
.
',._
I
. "'' i~.
cj)
CLOCK MOVEMENTS WITH BUILT-IN
MELODY MODULE
~~
~
~
WAs $99
PASSIVE INFRA RED
DETECTOR - PRICE
BREAKTHROUGH
It had to happen II
Jaycar was the first to offer pulse count
P IR's and lately we were the first to offer
pulse count for less than $100. We are
proud to announce another first in PIR's.
A QU ALITY PIA FOR ONLY $69.95
FULL PRICE
Sure, you are probably thinking "but what
about the quality and reliability" . There's
nothing worse than an alarm system that
false triggers, you know the old story
about the boy who cried wolf.
We have extensively tested the units and
have no doubt about their quallty and
operation ability.
Features & Specifications
• Dual element pyroelectric sensor
• 24 dual element detection zones in
three :ayers
• Wide angle 90" multi layer coverage
• 12 metre range
• Operation voltage 7.5 · 16V DC
• Tamper protected
• LED Indication
• Size 65(H) x 84(W) x 46(D)mm
• Colour beige
• Relay output
~
• 3 month guarantee ~
Cat. LA-5017
ONLY $69.95
$30 LESS THAN ANY PIR
WE KNOW OF
.t,-
~~~
"
•
irrpedance input unit
measuring to well over
50MHz. All parts mount
on the one PCB. The
Jaycar kit includes case,
front panel and all
specffied parts.
Cat. KA-1 702
~=
f"
WAS$299
LOW COST 50MHz
4 DIGIT DIGIT AL
FREQUENCY
METER 'f::
6
~~~:::i~u;~~ hly
~
sensitive, high
Y:>.
ET/
~eg:JiC:C~5JNTELLIGENT
s~.,.c
~
',l"-w'"
~-,1,"''I•'
· CATALOGUE
'·~~-~--·
132 pages of electronic goodies. Hyou
don, have our catalogue or if you've lost It
call in to any of our showrooms for a free
copy. (And a lollie if you have to wait). OR
send a large SAE to PO Box 185 Concord
2137 and we'll post you one.
6.3 VOLT MES
GLOBES
Don1 miss this bargain. OEM's
Bruce Routley (02) 747 2022.
NORMALLV 50~
THIS MONTH
4 for $1.00
10 for $2.00
. CARUNGFORD .
OPEN 'TIL 2pm SAT • 0.1 MONOLITHIC
:J■i
----------TOP SHOPPING AT JAYCAR
CAP SALE
We have available a pack of 0.1
monolithic capacitors with short leads at
a very special price. The leads vary from
1.5mm long to 5mm long. The 1.5mm are
fust long enough to go through a circuit
board.
ONLY $7.95 for 100
NORMALLY $16.50 per 100
Cat. RC-5496
I'!
Jaycar will purchase your surplus stocks
of components and equipment. We are
continually on the lookout for sources of
prime quallty merchandise.
CALL GARY JOHNSTON OR
BRUCE ROUTLEY NOW ON
(02) 747 2022
These are widely used In Personal
computers. Sorry about the price, but thes
are genuine European plugs. They are so
new the Asians haven, copied them yet.
Cat. PP-4007
$14.95
Outdoor Irifra
Red .Motion
Detector
Ideal for both residential and commercial
appllca.tlona, Completely seff contained an
easy to Install. Designed to mount directly
to a standard round junction box.
The unit wtll autorTIP•lcally turn on two
floodlights when someone walks within th
detector range. Ideal security system to
protect loved ones and property. Delectlo
range Is 40 feet long by 60 feet wtde. Ugh
wtll stay on for a mlnlmum of 1o seconds
up to 15 minutes (adjustable). Works only
at night. Globes not supplied.
cat. LA-5132
ONLY$139
FM TRANSMITTER (l\flNI l\flTTER)
Refer: Silicon Chip October 1988
Listen to your compact discs playing at home on your
Walkmanl This project transmitts the input signal on
FM which can be picked up by the FM radio in a Walkman.
Uses one IC and delivers about 200 microwatts. Full kit.
Cat. KC-5041
ONLY $29.95
POWERMATE2
Refer: EA October 1988
Revamped version of original Powermate
power supply. Delivers clean, crisp
regulated 13.8V DC at up to 5 amps.
Full kit.
Cat. KA-1707
$119
1GHz DIGITAL
FREQUENCY KIT
Complete kit.
$299
Cat. KC-5013
I
I
100WATT AMP
MODULE UTILISING
POLYSWITCH
IC: :J '2 If
f_,t:,;:!
u ~,
• SPEAKER
PROTECTION
Silicon Ch ip December 1987
.':' r.j"'•t-, . •Refer:
Kit includes PCB, all components
r v,.,•-·
,
ONLY $39.50
480/100
Capacitor discharge
gn ltion system for
- - - - y o u r car
4 9
cat. KE- s o
Playmaster/Jaycar 60/60 Blueprint Amp
$79.50
~E
~A
~ D~E~L~U~X~E..C~A1111R
~
ALARM
$369
Hundreds sold. See our 1988
catalogue for full details.
$89.50
• 300/300 full duplex plus 12oon5 half
duplex
Cat. KM-3046
.ACTIVE 'DIRECT
INJECTION " DI BOX
Full of features. See our 1988 catalogue for
full details.
Cat. KA-1690
$34.50
DIGITAL
CAPACITANCE
METER
$85
POWER SUPPLY TO
SUIT Cat. KE-4048 $29.50
TRANSFORMER
,
Ref: EA August 1985
• Checks values from 1pF to 99.99uF
over 3 ranges
Cat. KA-1695
$33.
Cat. MF-1095
'
UNIVERSAL SPEED
CONTROL
·«
,_ '
__
... •.\Oi
_:;.~•- ·
q
Control • eleclric drills, fans. electric
blankets, lamp dimmers , soldering irons.
PC board pre-built. Full kit only.
~~~' ~t
•
~•
~ - - -~_!__I_ V/SA
: F·
!MasterCard.
---
'.,
100 watt module
Cat. KE-4052
1
..
•<•
. I.
$21.50
Cat. KA-1652
.SUPER SIMPLE
MODEM
$27 .50
r:
Tests transistors,
SCR's and diodes.
Cat. KA -1119
Cat. KA-1550
STILL AVAILABLE
480/50 50 wait module
!
PULSE SHAPED
CDI
$8.95
Cat. KE-4050
~
See our 1988 catalogue for full details
$38.95
FABULOUS
ETl480 AMP
MODULES
IN CIRCUIT
~·.,_ ••
TRANSISTOR .., i 1..,
f •
TESTER
i ; ••
-< '
Cat. KS-6502
(less polyswitch) and heatsink bracket.
Cat. KC -5019
Polyswitch to suit
Cat. RN-3418
ONE OCTAVE
EQUALISER MODULE
10 band graphic equaliser module with
10 slider pots S
$
Cat. KM-3064
AVE 5
NOW $54.95
•. Handy Teslf"f
··sYNTOM"
DRUM
SYNTHESIS
·
~
~ -~
HEAD OFFICE
115 Parramatta Road Concord 2137
Telephone (02) 747 2022
Telex 72293
FACSIMILE (02) 744 0767
MAIL ORDER VIA YOUR
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! CONCORD
HURSTVILLE
THE EVOLUTION OF
ELECTRIC RAILWAYS
Of all Australian railways, the
Queensland system has in recent years
been the most innovative. Its significant
achievements include the introduction of
a powerful new electric locomotive, a
triple bogie unit rated at 2.9MW.
Electric locomotive design began
in Europe 85 years ago using a
single motor and rod-drive copied
from steam locomotives. These proved to be immensely strong but incapable of high speeds because of
the long fixed chassis mounting the
driving wheels.
Accordingly the two-bogie type
was introduced where each axle is
76
SILICON CHIP
driven by its own motor. To obtain
sufficient pulling power for freight
service, three driven axles (six driving wheels) per bogie were used.
Locomotives using two six-wheel
bogies have been constructed using
six traction motors, with a total
power up to 10,000HP (7.46MW).
This wheel arrangement is
known in Australia, USA and
Europe as the Co-Co type. "C" indicates three driven axles per bogie
and "o" means that no non-driven
wheels exist. In Switzerland the
Re6/6 nomenclature would be used
instead, where "R" indicates high
speed capability, "e" stands for
electric and 6/6 shows that there
are six driven axles out of a total of
six.
The Co-Co design has reigned
supreme worldwide for all heavy
service but it does present problems, particularly on the winding
narrow guage (3 feet 6 inches,
1067mm) tracks which make up the
Queensland rail system. There are
two particular problems:
(1). On tight curves the 3-axle
bogies incur considerable friction
between wheel flanges and the rail
inside edge. Wear on both the rails
FACING PAGE: CUT-AWAY drawing
of a 3000-class triple-bogie locomotive.
A lot of equipment is included in the
body, including a large transformer
◄ which steps down the 25kV AC
overhead supply. (Drawing courtesy
Clyde/ASEA- Walkers).
and the wheel flanges can be high.
(2). The long bogies also cause considerable track deflection which
means that maintenance to the permanent way is a constant problem.
These two problems could be
solved if 2-axle (Bo-Bo) locomotives
were used but the greater axle
loading could not be tolerated on
Queensland's light tracks. The BoBo design also presents a problem
in that for a given loco weight, less
tractive effort is available before
wheel slip is encountered, than for
a Co-Co design.
Built by Clyde/ASEA-Walkers, this powerful new 2.9MW electric locomotive
was the first of a new generation for Queensland Railways. The triple 2-axle
bogies allow the loco to negotiate tight curves and give less track deflection
than a conventional Co-Co design.
Tri-ho locomotives
The solution was a really innovative design involving a Bo-BoBo design - that's right, three
2-axle bogies, sometimes called a
Tri-Bo configuration. This has one
2-axle bogie at each end of the loco
and one in the middle. To allow the
loco to negotiate curves, the end
bogies swivel as you'd expect while
the middle bogie slides from side to
side under the loco chassis.
This permits the wheels of the
centre bogie to self-align with the
track for minimum sideways friction. The centre bogie carries one
'third of the total weight, with flexible cables joining the traction
motors to the control circuits in the
body above. Maximum sideways
deflection on the centre bogie, on
the tightest curves, is ± 200mm
from the centre-line of the loco
chassis.
With twelve wheels, all driven,
six traction motors and short bogie
wheelbase, many locomotive
designers see this type as ideal. For
a given loco weight, it has the same
axle loading and tractive effort as a
Co-Co design but it has the advantage that each bogie carries only
one third of the locomotive weight
(rather than half in a Bo-Bo or CoCo design). This point is important
in the design of short bridges and
culverts.
Before electrification, the Queens-
RE DTE
CONTROL
EQUIPMENT
ELii'ffllit'rcs
CUBICLE
Fig.1: this diagram shows how the major equipment is arranged inside
the new Queensland Railways 3000 class locomotives. The two end bogies
pivot in the normal way while the centre bogies can move sideways by
20cm in either direction to enable the loco to traverse curves.
land Railways were transporting
over one million tonnes of coal each
week from huge open-cut mines in
the Blair Athol, German Creek, Curragh and Blackwater districts.
From there, the coal was hauled to
the ports of Gladestone, Dalrymple
Bay and Hay Point, for shipment to
the world.
Record tonnages were being
hauled by the coal trains, pulled by
up to six diesel electric locomotives.
Each loco was rated at 1.65MW
giving a total of 9.9MW (13,270HP)
per train. Their huge consumption
of diesel fuel was a prime factor in
the decision by the Queensland
Government to electrify all the
state's coal lines. Queensland
Railways engineers then faced a
number of important questions:
(1). What axle loading (weight per
axle) and weight per bogie can be
withstood by the track, bridges and
track bed?
(2). What tractive effort and power
would be needed in each loco and
how many locomotives to use per
train?
(3). What electrical system to use,
what voltage, frequency, AC or DC,
and what type of control?
(4). Can the one locomotive design
perform all the required tasks: express passenger, heavy coal and
freight trains?
High voltage AC
Because of the long distances over 1490km of track was to be
OCTOBER 1988
77
ELECTRIC RAILWAYS - CTD
electrified - a single phase 25kV
AC 50Hz system was adopted. With
25kV AC used on the overhead contact wire, the necessary track
substations can be spaced at large
intervals. To further reduce the
current (and voltage drop) the QR
system uses an arrangement of
50kV feeder cables to supply
centre-tapped trackside transformers. These produce the 25kV
supply for the train overhead contact wire.
The 50kV AC feeder supply is
derived from the State Electricity
Commission's 132kV 3-phase supply fed to substations spaced at
about 50km intervals.
Locomotive manufacture
The State government split the
contract for manufacture of the
electric locomotives between two
Australian companies. The Clyde/
ASEA-Walkers group is building 70
locos, to be known as the 3500
class, at their Maryborough works.
Comeng (Commonwealth Engineering) is building the remaining 76
locomotives, to be called the 3100
class, at their Salisbury engineering works.
As all locos have the same major
specifications, the two classes
together are conjointly called the
" 3000 class". Both classes make
use of microprocessors and high
power gate-turn-off thyristors
(GTOs) to control the traction
motors. Each loco carries a
4.5MV A transformer which steps
down the 25kV overhead wire supply to several fixed voltages between
400 and 800 volts with lower
voltages for controls and auxiliaries.
Each locomotive is equipped with
six 495kW (664hp) direct current
motors. These are four pole compound wound with compensator
windings and interpoles. The whole
locomotive is therefore rated at
2.9MW continuous power at the
rail. These are geared for a maximum speed of 80km/hour and can
produce a continuous 260kN of
tractive effort at 40km/hour or a
maximum short time rated starting
tractive effort of 375kN (84,000lb).
The Clyde/ASEA-Walkers group
are using ASEA motors while the
Comeng company use Hitachi. The
motors have series field windings to
maximise starting torque and
separately excited low voltage
shunt field windings to achieve
precision control.
Bogies
Each of the three bogie frames is
fabricated from structural steel
with critical control and inspection
of all welds to ensure long life free
of fatigue problems. Primary
suspension is by chevrons of rubber
which are backed up by helical spring secondary suspension. These afford good isolation of motors and
body from track irregularities and
vibrations.
Traction rods transmit acceleration and braking forces from the
bogies to the body. The complete
bogie design is vital to the achievement of minimum axle-to-axle
weight transfer during acceleration. This allows both motors in
each bogie to be driven equally
hard without one wheel pair slipping. Thus maximum tractive effort
for a given loco weight can be
achieved.
GTO thyristors
As already mentioned, the
Queensland 3000 class are controlled by GTO thyristors. Fig.2 shows
the essential circuit for the motor
controls. Each motor armature is
fed by two series phase controlled
thyristor bridges connected in
series. Each thyistor bridge is fed
from a secondary winding on the
main transformer.
Another secondary winding supplies another thyristor bridge for
The Comeng 3100 class is similar to the Clyde/ASEA-Walkers 3500 class but uses Hitachi motors instead of ASEA
motors. Comeng is building 76 of these Tri-Bo locomotives at its Salisbury works.
78
SILICON CHIP
25kVAC SDHz
DYNAMIC
BRAKING
RESISTOR
REPEAT TRACTION
MOTORS 4,5,6
REPEAT MOTORS
2 AND 3
11 OVDC SUPPLY TD
MICROPROCESSORS,
CONTROL, BRAKES,
CRITICAL FUNCTIONS
-----1
+
'T'
DYNAMIC BRAKING
BATTERY
CHARGER
110v:
SERIES FIELD
MOTOR No.1
..J..
-:;
SHUNT AELDS
MOTORS 4,5,6
AUXILIARY SUPPLY
3-PHASE 415VAC SOHz
----------''W------TD S
NT
MoTt:s 2 FlEJ-~s3
,
---------------------------,-\-----SEPARATELY EXCITED
SHUNT FIELD MOTOR No.1
WHEEL
RAIL
Fig.2 partial schematic of the electrical system within the 3000 class locos. SCR chopper circuits are used to
control the power to the six traction motors. The locos have dynamic braking but do not employ regeneration
to put power back in the grid.
the shunt field windings of all traction motors. The phase control
signals are derived from microprocessors which take into account
the acceleration or braking
demands from the driver.
The main thyristors are cooled by
forced oil flow in , the Clyde/ASEAW alkers locomotives while forced
air cooling is used in the ComengHitachi versions.
Electrical power for the microprocessors, controlling electronics,
running lights and other vital functions comes from the onboard
l lODC battery supply.
Brakes
In formulating the concept of a
locomotive for heavy-haul freight,
general freight and also passenger
service, the designers had little
scope for innovation in brake
design.
Dynamic braking can certainly
be provided . on the locomotive,
saving wear on brake blocks
throughout the train, but for final
stopping and emergency use full air
brakes are needed.
As the new locos will haul both
new and old rolling stock, standard
air brake systems must be provided. To allow for multiple operation
of locomotives by one driver, the
braking controls are mounted in a
separate rack in the loco and
remotely controlled by pneumatic
lines from either driver's cab.
For dynamic braking, as Fig.2
shows, the armatures of the traction motors are disconnected from
the thyristor bridges and connected
to heavy duty low resistance braking resistors. The traction motors
now act as DC generators, with the
degree of braking controlled by the
power applied to the shunt field
windings.
Multiple operation
Up to six locos may be used on
heavy coal trains with three locos
at the front and three near the middle. These coal trains can be up to
2km long!
Control for two or three head-end
locomotives from any driver's cabin
is via a 44-wire cable connecting
the adjacent locomotives. Control
for the three locos a kilometre away
in the middle of the train is by
LOCOTROL II, an ingenious radio
control system which we will investigate in a later episode of this
series.
While every locomotive is fitted
with a driver's cab at each end, only 39 locos are equipped as command units with LOCOTROL sending
equipment.
Creep control
The maximum tractive effort a
locomotive can exert depends on:
(1). The total motor power.
(2). The gear ratio from armature
shaft to axle.
(3). The percentage adhesion of the
wheel-rail contact; which depends
on the wheel and rail surfaces and
the weight on each wheel.
The QR 3000 class electric
locomotives have about the maximum motor power and gear ratio
for the weight per axle allowed by
the track. Apart from applying sand
to the rails, one way to maximise
adhesion is to improve the wheelrail surfaces. The polished wheel
OCT0BER1988
79
Other auxiliaries include cabin airconditioning, blower fan motors (for
traction motor cooling), cooling oil
pumps for · the main transformer,
thyristor cooling and air compressors for train air brakes. These
pumps and blowers are driven by
3-phase 415 volt AC induction
motors.
The 3-phase 415V AC supply is
derived from a single phase to
3-phase converter driven by an extra secondary winding on the main
single phase transformer.
Comeng have used a rotary
machine consisting of a phase
motor driving a 3-phase alternator
which is hung beneath the loco cab.
The Clyde/ASEA-Walkers' locos
use a solid-state 3-phase converter
instead.
Results
Clyde/ASEA-Walkers is building 70 of the new 3500 class electric locomotives
at its Maryborough works. This photo shows two partially completed bodies.
surface resulting from the use of
composition brake blocks tends to
cause wheel slip.
Over the last few years great advances have been made in minimising wheel slip in locomotives and
thereby maximising tractive effort.
This is called " creep control". It
also has the benefit of keeping both
driving wheel and rail steel surfaces in the best condition for maximum adhesion.
In essence creep control is an
automatic control system which
makes the loco driving wheels
travel up to 5 % faster than the forward speed of the train. This is
referred to as "5% creep". Creep
also has the effect of continually
grinding the loco wheels on the rails
so that the wheel contact surfaces
remain clean but not polished. Such
a surface ensures maximum wheelrail adhesion.
Experience has shown that 5%
creep is an optimum figure. If more
creep is allowed the driving wheels
will tend to slip, and produce less
tractive effort. Naturally, when less
than maximum tractive effort is required, the creep value will be less,
as set by the control system.
80
SILICON CHIP
To maintain creep at the critical
value of 5 % , ASEA has provided
radar equipment below the
locomotive, to measure true ground
speed. Also a tachogenerator
measures axle rpm. This then gives
a true comparison of wheel
periphery speed and rail speed.
If the wheel periphery speed is
more than 5 % faster than rail
speed, the traction motor armature
current feedback signal is increased by the creep controller. This
feedback retards the phase of the
trigger signal for the GTO
thyristors supplying armature current, hence reducing motor current
and torque to bring the creep back
to a figure of 5% .
Should the creep be less than 5 %
the reverse action increases motor
current and speed to regain the optimum creep. Microprocessors do
the control functions.
Auxiliaries
Essential auxiliaries such as the
phase control circuits of the GTO
thyristor bridges, running lights
and emergency lighting are
powered by a 110V DC lead-acid
battery slung under the loco body.
The first loco built, No.3501, rolled out of the Maryborough
workshops on Thursday 29 May
1986 and was operating between
Rockhampton and Gladstone by 6
September 1986. The first electrically hauled coal train ran in
May 1987.
The whole electrification program including the main line from
Caboolture to Rockhampton and the
coal lines in four stages will cost
one billion dollars . This money will
eventually be repaid by the
achievement of faster running
times with resultant greater use of
wagons, increased revenue and
huge savings in diesel oil.
These electric locomotives a re
eminently successful, with 10,000
tonne trains being hauled by six
locomotives at considerably higher
speeds than could be achieved by
the previous diesel electric locos.
Footnote
While the 3000 series are the
first large order of Tri-Bo locos to
be ordered by an Australian
railway system and one of the few
Tri-Bo classes in the world, the first
Australian Tri-Bo loco was the
8650 delivered to the NSW system
in October 1985. This was a test
bed for the triple-bogie arrangement used in the 3000 class, as built
by Comeng. The rest of the
50-strong 8600 class NSW DC electric locos have conventional Co-Co
bogies.
~
Silicon Chip Back Issues
Issue Highlights
November 1987: Car Stereo in Your
Horne; 1GHz Frequency Meter;
Capacitance Adapter tor DMMs.
1987: 1 00W Power
Amplifier Module; Passive lntrared
Sensor tor Burglar Alarms; Universal
Speed Control and Lamp Dimmer;
24V to 12V DC Converter.
December
January 1988:~ 'Ci:ll11'100Wtie UHF
Antenn ·
ly; CustolS
Adapter t
l!JlcGI
wer Suppmger; Subcarrier
M Tuners.
February 1988: 200 Watt Stereo
Power Amplifier; Deluxe Car Burglar
Alarm; End of · File Indicator tor
Modems; Simple Door Minder; Low
Ohms Adapter tor Multimeters.
March 1988: Remote Switch tor Car
Alarms; Telephone Line Grabber;
Low Cost Function Generator;
Endless Loop Tape Player.
April 1988: Walkaround Throttle tor
Model Railroads; pH Meter tor Swim·
ming Pools; Slave Flash Trigger;
Headphone Amplifier tor CD Players.
May 1988: Optical Tachometer tor
Aeromodellers; High Energy Ignition
for Cars; Ultrasonic Car Burglar
Alarm; Restoring Vintage Radio
Receivers.
June 1988: Stereo Control Preamplifier; Breakerless Ignition For
Cars; Automatic Light Controller;
Mega-Fast Nicad Battery Charger.
July 1988: Fitting a Fuel Cut-Off
Solenoid; Booster for TV & FM
Signals; The Discolight Light Show;
Tone Burst Source tor Amplifier
Testing.
1988: Build a Plasma
Display; Remote Chime/Doorbell;
High Performance AC Millivoltmeter;
Getting the Most Out of Nicad
Batteries.
August
September 1988: Hands-Free
Speakerphone; Electronic Fish Bite
Detector; Switchmode Charger tor
12V Gel Batteries; Vader Voice.
BACK ISSUES ORDER FORM
Please send me a back issue tor:
D November 1987
D December 1987
D February 1988
D March 1988
D August 1 988
D May 1 988
D June 1 988
D July 1 988
D April 1988
D Sept.1988
Enclosed is my cheque/money order for $ ______ or please debit my D Bankcard
Card No
I~~~~~~~~~~~~~~~~~
Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_/_/_ _
Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
(PLEASE PRINT)
Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Suburb/town _ _ __ _ _ _ _ _ _ _ _ _ Postcode____
D Visa Card
Price: $A5.00 each (includes
postage): Overseas orders add
$A 1.00 per issue tor postage.
NZ & PNG orders are sent by
air mail.
Detach and mail to:
SILICON CHIP PUBLICATIONS
PO BOX 139
COLLAROY BEACH
NSW 2097
L - - - - - - - - - - - - - - - - - - - - - - - - -·- - - - - - - - - - - - - . . . . J
OCT0BER1988
81
Our range of DATAK products has
proved enormously successful:
small wonder, this quality product,
made in the USA, makes virtually
every aspect of PCB making a
breeze. Below are just some of the
DATAK products - many reduced
to tempt you to try them!
·Etch Resist Pen Dry Transfers DATAK PCB designing and
Remember the pen we used to
sell? We stopped selling it_
when we found out the resist
was a deadly poison (others
still sell it!). The DATAK etch
resist pen is a non-nasty,
highly effective way to make
one-off PCB's. Cat N-5180
DATAK make some great
transfers. To whet your
appetite (no, Lucretia, you
don't eat them) here are two.
.
SAMPLER
ASSORTMENT,
containing 17 different sheets. A
5766
~~~rter pack. Cat N95
S
~- NOW 16
Datak
Burnishing
Tool: Save $3
TARGETS & REGISTERS,
containing 40 different pcb &
crosshair registration marks for
precision alignment. Cat N-5820
~
You'll need one of these if
you're at all serious about
making PCB's. Cat N-5715
NOW s4es
UNIVERSAL OIL
PATTERNS, allowing you to
make any OIL pattern up to 40
leads. 48 in pack. Cat N-5768
s1495
Datak Contact
Frame:
Datak Circuit
Fix It Kit: Save
$13
Eventually, you'll get a PCB
that's RS. Fix it with Cricuit Fix
Kit. Pure Copper traces &
donuts with adhesive backing,
readY. to repair a PCB or
modify a new one. Great for
developers too. Cat N-5900
Save $6
~~~~ii~~~~~t exclusive to Dick
You've asked for them: an economic
range of tapes, pads, lettering and
so on for designing PCB patterns,
marking panels and so on. Here
they are!
TITLES, LABELS,
NUMBERS ETC•
A great range of w~rdmg re;dy for
your front panel or other marking
applications Dry transfer lettering
simply rub over them with a
suitable burnisher (such as a ball
point pen).
Audio, TV & HI Fi
Five sheets containing titles for the
above applications plus one letter/
number sheet. Available in Black
(Cat N-5753) or White (Cat N-5754)
Amateur Radio & TV
Similar to above, five sheets to
pack, with letter/number sheet.
Black (Cat N-5755) White (Cat N-5756)
Test & Industrial
Equipment
Completing the set: 5 sheets for
CRO's, meters, analysers, etc etc.
Yep, you'll need one of these
Also includes letter/number sheet.
too. If you're serious, that is.
Black (Cat N-5757) White (Cat N-5758)
Beats the old sheet'o glass and
95
two books routine anytime. Cat ALL ABOVE SETS:
N-5710
s8
Was$35.95
DIAL MARKINGS,
SCALES, PATTERNS,
PANEL & METER
Marks & Switch
Patterns
Three sheets of assorted arrows,
lines, switch graduations, numbers,
etc in both Black and White.
Cat N-5750
95 set
s11
NEED EXTRA POWER?
As we get more and more electrical products, we have less and less spare outlets. Dick Smith
Electronics solves your power point problems - without going to the expense of having extra outlets
installed!
Click Spacesaver Double Adaptors
Not like four old ones: these fit flush on the power point to _creat~. a d~~ble power point from a
single. I you already have a double power point, you can fit the twin Spacesavers to make a
4-way outlet!
Single Spacesaver
Double Adaptor
Resist These Bargains?
Unlikely!
DATAK quality resist products to make your PCB making a
breeze. They're also refills for the DATAK PCB kit
Developer
Resist
Filter
N-5905
N-5907
N-5711
Was $11.95
Was $18.95
Was $10.95
Now $9.95 Now $15.95 Now $6.95
{SID
....,.,,,
IIESHIY
LIQUID
~ .:~·•;""!.,~
-==·
film Processing
Chemical Pack
Photo-sensitive polyester film
suitable for laying out PCB
patterns in pos or neg format.
6 sheets 125 x 150mm.
Cat N-5705
Film developer and fixer pos/
neg him, or for replacement
pack for PCB kit Cat N-5909
Was $11.00
Now s995
s14
PCB Making Materials
Datak precision tapes, pads and
donuts perfect for commercial as
well as hobbyist pcb pattern
preparation.
Available in various sizes as listed:
TAPES - precision slit highly
flexible crepe.
.031in (N-5780) .080in (N-5786)
.040in (N-5782) .093in (N-5788)
.062in (N-5784) .125in (N-5790)
~~~~NE
s395
ea
,DONUTS - precision cut donuts
· to accurately match tape. 380
donuts in each pack, all .031in OD
on 0.2in x 0.3in centres
:~~~:~ =
All one price
.125in 00- N-5774 s-425
15
5775
· 0in OD - NPATTERNS - Various styles
suit most applications.
T0-18 Pattern (3 pin), 144 in set.
Cat N-5760
84
Jg·~-m~rn (3 pin). in set.
32 set
~1
pack, in
16 Pin OIL pack, narrow pads. 32 in
set Cat N-5765 •A 25
k
All one Price: ...
gg
~:m~
pack
~-if~
paC
""o"'w•a"'v"'a"'ila'■.'b■.'te"'a"lt"ll!'"'51!0""',es111■:--------■-•------•-----
Fit to both the left and right outlets of a double
power point to turn It into a 4-way outlet on the
wall Ideal for stereo systems, computers, etc etc
Cat P-5-'-44""4_ _ __
Fits to a single outlet or
to the nght hand outlet
of a double, extends to
the nght hand side
cat P-5442
s395
s7es
---...~~~~~:=,=!~:!;,
"
~
,:_l}
~~ea,J,,,;;;;;;,,j.JI
How about a bit of protection?
If you're running sensitive equipment, (computers, video & TV, etc) you should know that spikes
or surges on the mains can damage or even destroy it, or destroy hours or days of work on disk!
The Surgebuster series of mains suppression filters virtually eliminate these surges: in fact,
they're so sure of themselves they offer $5000 FREE INSURANCE COVER against voltage spikes
or power surges I
Click Single Power Point Protector
The Surgebuster Junior plugs into any outlet and protects
any device or devices plugged into it.
Don't forget the $5000 free insurance cover is included!
Cat P-5617
s4ges
Click Surgebuster &-Way Board
The best of both worlds: a six way power board - with all oullets on that board protected
against surges or spikes. It's also overload protected. And yes, it too comes with the $5000
insurance cover Cat P-6515
'5995
TIME FOR A NEW TV ANTENNA?
How were the Olympics? Twenty runners in each heat? Two high-jumpers on the bar at once? You
need a new antenna! Dick Smith Electronics has a huge range of antennas - there's one right for
your area (ask for free, helpful advice at your nearest store). Here's just a small sample:
Band IV and V
Suburban VHF
It's a great all-round performer for the
typical suburban home
(regardless of city). Easy ~o
erect, good fib ratio and very
good value for money.
.----"Cat L-4022
S6S95
-
What a performer! Covers all UHF
channels, so if you've got both bands we've
got you covered! Butterfly elements,
· gold anodised
/
finish for long ,,.
•
long life.
,,.
Cat L-4084
sgg
~ ~~~~e!r!r~~
Meter Dial Markings
Four sheets with dial plate arcs &
graduations to let you customise
any meter movement. Suits meter
radii from 25 to 125mm. Black only.
Cat_N-5752
50 set
taEV/! Twin Pack Spacesavers
~y~u~e~n ~!p~I~!
chances are you only want
channel 28 UHF. This band IV ,
antenna Is pertect - and It wont
break the bank! Cat L-4082
'65
band V stations
(which include most l~cal
area translators). High
gain easy to erect
Cat L-4080
'5995
-
Accessories, Too:
Barge Board Mount: Easy way of getting the antenna up from a vertical surface.
Catl-4150
Short Mount: Designed to hold vertical masts. 28cm long, with saddle clamp. Cat L-4152
Longer Mount: As above, but 69cm long to clear eves, etc. With saddle clamp. carL-4153
Mast Section: 2.4m galvanised pipe for mounting antenna. 27.5mm diam. Cat L-4156
Telescopic Mast: 4.8m galvanised telescoping mast for that extra height. Cat L-4157
Saddle Clamp: 90 degree V-block and U-bolt assembly for holding mast to mount, antenna to
mast, etc. Cat L-4165
2-way Splitter: Inside splitter for running two TV's from one antenna. Suits 300 Ohm cable.
s495
Cat L-4218
4-way Splitter: As above, but for running up to 4 TV's from one antenna. For high signal
levels. Cat L-4220
~~hm: Use with coax cable installations for running 2 TV's. Inside use only.
2
~Jhm: As above, allowing 4 sets from one antenna. Suitable for strong signal levels.
4
Baluns: Used for converting 300 ohm system to 75 ohm and vice versa (eg coaxial lead to an
old TV with 300 ohm antenna inputs).
•2"5
Universal: Inside use only. Cat L-4456
Outside: Protected from the elements. Cat L-4465
Masthead Diplexer: Combines the signals from UHF and VHF antennas, allowing one cable
~;ft!/
t_f~J
;:dn~~:i~~:~: Used where TV set has only one antenna input but VHF and UHF antennas
need to be connected. cat L-4476
TVI Filter: High-Pass filter for VHF & UHF TV, eliminates or reduces interference from CB, HF
amateur, etc. Cat L-4475
• N SW• Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 6 71 7722 • Bondi Junction 38 71444 • Brookvale
(Warringah Mall) 905 0441 • CampbeHtown (046)27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill
439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • MaiUand 33 7866 • Miranda 525 2722
• NewcasUe 611896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777
• Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800 •ACT• Fyshwick 80 4944 •VIC• Ballarat 31 5433
• Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366
• Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088
• Richmond 4281614 • Ringwood8795338 • Springvale5470522 • QLD • Brisbane City 229 9377• Buranda 3916233
• Cairns 311 515 • Chennside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863
• Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide Ctly 2321200 • Bevet1ey 3471900
• St. Marya 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • FremanUe 335 9733
• North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 811977
NOW AVAILABLE AT ALL STORES - OR CALL
TOLL FREE: (008) 22 6610
FOR HOME DELIVERY!
IT'S STILL OUT THERE ...
Yes! You could still find a $1000 bonus ii you're the lucky
customer who purchases the One Millionth Fun Way Kill At time
of going to press it was still out there, somewhere on a shell in a
Dick Smith Electronics store (or possibly even in DSXpress, the
Mail Order Centre).
No questions, no qualifications: ii you buy the lucky one
millionth kit, you'll win the prize: $1000 worth of any products
from your Dick Smith Electronics store.
NEW!
GENUINE CANNON
CONNECTORS
Butane "Pencil" Blowtorch
Soldering, silver soldering, glass bending, heatshrinking, even
small brazing - they're all easy with this superb little tool.
Butane powered (standard cig lighter refills) with controllable
flame down to near pin-prick. All in a tiny (200mm long x 13mm
diam) hand-held torch. Cat T-1380
Why take the risk with cheap imitations? Genuine Cannon
Connectors for Audio & mains use wi ll see you right - and
won't let you down when the going gets tough!
s1495
Mains Rated (fully approved
½ Price
Superstand
for mains use)
AXR-LNE-12
AXR-LNE-32
AXR-LNE-31
AXR-LNE-31
LINE PLUG P-1627 $9.95
PANEL PLUG P-1629 $7 ,50
PANEL SOCKET P-1630 $7 .95
LINE SOCKET P-1631 $9.50
THE ONE MILLIONTH FUNWAY
KIT WITH $1000 BONUS!
s12s5
Hobbyists - repair shops - labs assembly benches - if there's one
item your bench really needs, this is
IT! Heavy cast base with stands for
Soldering Iron (complete with spiral),
solder rol AND an adjustable vice
with 360 degree, rotation for holding
and turning pcb s One of our most
~ o p u l a r stands - our bulk buying
OJ
saves you money Cat T-5700
12V Tester
High Power Audio Ran!e (ideal
f Or Speaker COnnectOrS, efc
AXR-PDN-12W LINE PLUG P-1632 $10.50
AXR-PDN-11suNE socKETP-1634$9.95
AXR-PDN-31W PANEL SOCKET P-1636 $7.50
SAVE ON
SWITCHES!
Mercury
Switch
~
WAS s69 96 NOW ON•'Y s3495
•
L
<at>
125V AC 3A. Ideal for
projects or automotive
Now 5 175
'119
Standard DPDT
Ji
yr
No, not literally - only the price. When you want the best in
performance/noise/weight/size ratio, you cannot go past a
toroidal transfomer. And now both of these are reduced $10!
Hurry - limited stocks at this price!
use. Standard toggle with
on/off indicator plate. Ill
CatS-1215
~ 45+45V<at> 3.3A plus 15+ 15V (ideal high power amplifiers)
Was $1 95
~ Cat M-1600
Tilt mount switch SPOT.
Essentially a movement
detecting switch. Low
Same as above but 1!_ 1
current applications. Ideal double pole/double
for bike and car alarms,
throw. Cat S-1216·;
~
etc. Cat S-1935
~
•
•
Was $3. 95
NOW 5295
-
TOROIDAL TRANSFORMERS
Standard SPST SLASHED
AXR-PDN-14B PANELPLUG P-1638 $8.50
SOS:
~
Was $2.25
NOW s1 75
What a Bargain
Manufacturer's Error: You reap the benefit! Quality Bit Blitzer
"121" Internal Modems, fully guaranteed and in perfect
working order, around $100+ less than you'd expect to pay.
Cat X-3304
..
.
ONLY s199
NOW IN STOCK.
We've raved about these in our catalogue.
We've told you how fantastic they are - now
they're in stock so you cand find out for
yourself! AC Voltage detectors which don't
rely on contact - so they're S-A-F-E! About
the size of a small marker pen, perfect for
electricians, maintenance people. hobbyists,
everyone! First shipment is almost sold out!
Cat Q-1530
Was $79.95 NOW ONLY S69
95
35+35V<at> 2.2A plus 15+15V (ideal medium power amplifiers)
Cat M-1602
Was $69.95 NOW ONLY s59
95
CHEAP CASE!
Another beauty: this one's for auto cable testing.
Actually pierces the insulation without removing
cables, gives no go/maybe/good indication with
3 leds. Also tests HT pulses from distributoL
Look at the price! Cat a-2000
795
Was $9.95 NOW S
NEW!
No Frills Multimeter
Most hobbyists need two multimeters:
their good bench meter (often a digital)
and a cheapie - one that can take the
rough and tumble, and doesn't cost a
fortune. This one's the latter category:
but for the low low pr1ce you get a great
10k/v meter with 18 ranges including 2
battery check seales.
Includes probes.
Cat Q-1015
s2495
Huge range of
moving coil and
digital multimeters
from only $17.95 .·
Hobbyist CRO
We made thousands of these cases to suit our low cost amplifier.
To many! Our loss is your gain: we've slashed the price to_ move Most hobbyists need a CRO excess stock. They make great cases for virtually any pro1ect:
most don't have one. Once
simply put the front panel on to suit yourself and WOW! Cat H-2900 you've used a CRO you'll
how you got on without
W $ 34 95 ~~ 11 wonder
it! This one won't break the
bank, but gives a usable
o
response to beyond 6.5MHz •
ideal for most users. Try it:
you'll like it! Cat 0-1280
as
,
$2795
NOW
~
---··
___,,,.
GET INTO SCANNING!
s399
175XL Mobile 1OOXL
Handheld
60 Meg Probes Coloured
Here's a value-packed set of
Test Clips
probes for CRO use. Multiple
What a great hobby: no licences or qualifications required, and
you can start straight away with these superb Bearcat Scanners!
Hurry! Stock won't last long at this
crazy price!
101 Key Keyboard
The cheapest around - but there's no loss of quality! Superb
"Alps" keyswitches for reliability, ideal for most IBM compatible
computers. Cat X-3821
Covers all popular bands, with
16 channel memory to store
your favourite frequencies. 12
volt operated, comes with AC
Adaptor to use at home.
Cat D-2812
S369
s149
Our most popular 16 channel memory,
covers 9 bands
between 66 and
512MHz. Complete
with rechargeable
NiCad batteries
and charger!
Cat D-2813
s399
MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS:
• NSW • Arlll411t: Sound Components 72 4981 • Ballina: Ballina Electronics 86 7022 • Bownl: F.R.H. Electrical 611861 • Broken
Hill: Hobbies & Electronics 88 4098 • Cllarltslown: Newtronics 43 9600 • Cliffs H1r1lot1r: Coifs Harbour Electronics 52 5684 • Ou~bo:
Chris's Hi-Fi 82 8711 • Fonler: Forster Village Electronics 54 5006 • Glen lnaes: John Sommerlad Electronics 32 3661 • Griflilh:
Miatronics 62 4534 • lnvenll: Lyn Willing Electronics 221821 • Li111on: Decro Electronics Services 21 4137 • Moree: Moree
Electronics 52 3458 ofll1N1111: Head ware 72 3895 • Nown: Nowra Electronics 21 4979 • Wqga: Phillips Electronics 21 6558 • VIC
• Morwlll: Morwell Electronics 34 6133 • Slllpparton: Phillips Electronics Pty. Ltd. 21 9497 • W1rrn1"1bool: Marrtronics 62 9870
•OLD• BIN1111ni: Bob Elkin Electronics 72 1785 • Kinprey: Holmes Today Electronics 62 1658 • Klwana: Splitec 94 7349 •
Mlcuy: Stevens tlectronics 511723 • Mlryboroqh: Keller Electronics 21 4559 •SA• M16I1111iitr: Hutchessons Communications
Centre 25 0400 •WA• Allllny: Micro Electronics 41 2077 • Genldlon: Batavia Lighting & Electrical 231842
• Klrn1'1: Dave's Oscitronics 85 4836 • TAS • Dtvonport: A.I. Electronics & Hobbies 24 8322
piece set, with x1x10 switch,
60MHz bandwidth all in a handy
plastic pouch. ~
Cat Q-1247
.;0
If you're birdsnesting or even
doing a lot of circuit testing,
these multi-coloured test clips
are great. Mini size, come in a
variety of colours. And they're
near hall price this month!
Cat W-4588
Normally 95c ea
NOW ONLY
5Oceach
AMATEUR RADIO
By GARRY CRATT, VK2YBX
How to convert a CB radio
to the 28MHz amateur band
It's easy to convert a CB radio to the 28MHz
amateur band. Just build and fit this simple
oscillator circuit for 40 channel operation on
AM or SSB.
One of the main problems confronting the amateur operator
when it comes to multi-band operation is the cost of multiple
transceivers to cover every band.
In particular, transceivers for the
10-metre (28MHz) band are expensive. But there is another way convert a low-cost 2 7MHz CB
transceiver to do the job.
While this task may appear to be
quite daunting, it's really fairly
straightforward. All you have to do
is fit the simple oscillator circuit
described here and perform a few
circuit tweaks. The converted
transceiver can be used for novice
operation on 10-metres or for driving a transverter (ie, a frequency
converter) for operation on the VHF
or UHF bands.
A 40-channel CB transceiver
capable of SSB operation is an ideal
candidate for conversion to 28MHz
operation. These transceivers were
imported in vast quantities so their
prices are much lower than
equivalent amateur-band models.
CLARIFIER AND
AMISSB OFFSETS
5.12MHz
10.24MHz
-101--1.-~
VCO = 16.27MHz (CH 1) TO
16.71MHz (CH 40)
CHANNEL SELECT
PLUS SSB OFFSETS
+N = 91 (CH 1) TO 135 (CH 40)
DOWNMIX INPUTS
=
0.91MHz (CH 1) TO
1.35MHz (CH 40)
10.695MHz AM
10.6975MHz LSB
10.6925MHz USB
Tc,
AM/SSB
OFFSETS
Fig.1: the Uniden AX 144 uses phase locked loop (PLL) frequency
synthesis to set the output frequency. To change the band of
operation, the tripler is disabled and a signal from an external
oscillator injected into the PLL mixer.
84
SILICON CHIP
As well, they were made to meet
stringent DOTC regulations, thus
guaranteeing reasonable quality.
For this project, we chose to convert a Uniden AX 144 SSB
transceiver which retails for
around $329. However, many other
late-model SSB transceivers employ
similar circuitry and could be
modified just as easily.
PLL tuning
Fig.1 shows the block diagram of
the transceiver. As can be seen, the
unit uses phase locked loop (PLL)
frequency synthesis to select a
precise 40-channel segment in the
27MHz band (26 .965MHz to
27.405MHz). What we have to do is
change this to a 40-channel segment of the 28MHz band.
The first thing to note is that the
frequency bandwidth of t he
transceiver is fixed at 440kHz (ie,
27 .405MHz to 26.965MHz). This
means that it's not possible to cover
the full 28MHz band. A good compromise, for either 10-metre or
transverter operation, is to convert
the unit to operate from 28.285MHz
to 28.725MHz.
OK, so we've now selected the
frequency segment in which we
wish to operate. We now have to
decide how to convert the
transceiver to this higher frequency segment. What we have to do is
increase the VCO frequency, as set
by the PLL, by a fixed amount on
each channel.
Because of the way in which the
PLL and the VCO operate, the
easiest way to do this is to change
the frequency that's normally fed
RB
100{)
r---......---....--'¥1~-0+BV REG.
3xBA244
OR SIM.
D1
R1
3.3k
CS
10pF
-----111--oOUTPUT
.,.
B
L1,L2,L3 : 12T 25 B&S ENAMELLED COPPER
WIRE CLOSE WOUND ON FERRITE SLUG
EOC
VIEWED FROM
BELOW
Fig.2: the external oscillator circuit is a Colpitts type with diode
switching to vary the output frequency. Either AM, LSB or USB
operation can be selected by switching the corresponding
input to + 8V.
from the P11 to the P11 mixer via
the tripler. As Fig.1 shows, the P11
generates a 5.12MHz signal by
dividing the 10.240MHz reference
oscillator frequency by two. This
5.12MHz signal is then externally
tripled to 15.36MHz and mixed
with the VCO frequency to give a
control frequency for the P11.
This control frequency is simply
the difference between the tripler
and VCO output frequencies. In
normal CB mode, the VCO frequency ranges from 16.27MHz (Ch.1) to
16.71MHz (Ch.40) and so the control frequency ranges from
0.91MHz to 1.35MHz. Note that the
VCO output is also fed to both the
transmit and receive mixers.
To change the band of operation
we simply disable the 5.12MHz
tripler and inject a suitable (higher)
mixing frequency into the P11 mixer from an external oscillator. This
oscillator must incorporate some
method of frequency compensation
to allow for USB and 1SB operation,
as well as AM operation.
Oscillator circuit
Fig.2 shows the circuit of our
oscillator. It is a Colpitts type
employing diode switching to vary
the amount of inductance in series
with the crystal (Xl). The nominal
frequency is set by crystal Xl but is
modified according to whether 11 ,
12 or 13 are switched in.
The mode switching function is
achieved by conveniently utilising
the 8-volt output from the mode
switch on the front panel of the
transceiver. Thus, for 1SB operation, the mode switch connects the
1SB input of the oscillator to + 8V.
This forward biases D1 and connects 11C1 to the crystal.
The AM and USB modes are
selected in exactly the same
fashion.
Crystal frequency
So much for the basic oscillator
circuit. We now have to calculate
the crystal frequency (Xr) required
to give us the desired frequency
band. To do that, we use the following equation:
Xr = 15.36MHz + (N x 0.44)MHz
where N equals the number of
440kHz band segments above the
original CB band. In this case, we
have to move the frequency band
up by 1.32MHz (ie, N = 3). Thus:
Xr = 15.36 + 1.32 = 16.68MHz.
It is necessary to add 2.5kHz to
this figure to allow for USB operation. This is because the series inductors in the circuit only allow the
oscillator frequency to be reduced.
Thus, the final crystal frequency
becomes 16.6825MHz.
Construction
The circuit is built on a small
printed circuit board coded
06210881 and measuring 53 x
35mm. Fig.3 shows how to install
the parts.
You can install the parts in any
order you like although the three
coils are best left until last. Keep all
component leads as short as possible and push the transistor all the
way down onto the board before
soldering its leads.
The three coils are all wound using 12 turns of 25 B&S enamelled
copper wire on an F14 ferrite slug.
This gives an inductance of 5-l0µH,
depending on the position of the ferrite slug. Clean and tin the enammelled copper wire leads before
soldering the coils to the PCB.
It is a good idea to check the
oscillator for correct operation
before fitting it to the transceiver.
use-~,.,....,,_ .._,
AM----:rrs:;-·,._"'_,,"-"'l
" ..,,
"-..,.r~=
LSB
+BV REG.
Fig.3: keep the leads as short as
possible when installing the parts
on the PCB.
Fig.4: you can use this full-size artwork to
make your own printed circuit board.
OCT0BER1988
85
PARTS LIST
1 PCB, code 06210881, 53 x
35mm
1 16.6825MHz crystal, 30pF
parallel cut, Hy-Q code
GE05E, OC49 holder
1 BC548 NPN transistor
3 BA244 or similar switching
diodes
3 F14 ferrite slugs
Capacitors
1
1
1
1
1
1
1
.01 µF ceramic
330pF ceramic
1 OOpF ceramic
82pF ceramic
39pF ceramic
18pF ceramic
1 OpF ceramic
Resistors (0.25W, 5%)
2 X 22k0, 3 X 3.3k0, 1
1 x 1 kO, 1 x 1000
This view shows bow the oscillator board was mounted in the Uniden AX 144
transceiver. The AM, LSB and USB inputs are connected to the mode switch
pins on the PCB at the front of the chassis (top right).
L12
470uH
R93
22k
C96
...
.047r
This is easily done by checking the
output with an oscilloscope, frequency counter or HF receiver. Of
course, you will have to strap the
AM select input temporarily to the
positive supply so that the circuit
will oscillate continuously.
If everything checks out OK, adjust L2 for an output frequency of
16.680MHz. The LSB and USB
modes should then be selected and
86
SILICON CHIP
Fig.5: to disable the tripler, you
simply lift one end of C73
(marked with a cross). The output
from the external oscillator is
then fed into C73 and L14
adjusted to give PLL lock on the
new band.
Ll and L3 adjusted for output frequencies of 16.6775MHz and
16.6825MHz respectively. These
adjustments will interact slightly
but don't worry too much at this
stage - we'll adjust the oscillator
more accurately later on.
Fitting the oscillator
The location of the oscillator
board is not critical, although care
X
2.2k0,
Miscellaneous
Hookup wire, 25 B&S enamelled
copper wire for coils.
should be taken to ensure that it is
clear of the speaker when the
transceiver is reassembled. It can
be secured by soldering a piece of
heavy guage tinned copper wire
from the earth foil to an adjacent
metal can on the main transceiver
PCB. The + 8V regulated DC rail is
available on pin 11 of the PLL chip.
The next step is to locate the
5.12MHz output from the PLL and
disconnect it from the tripler circuit. Fig.5 shows the location on the
AX-144 transceiver. In this case,
the 5.12MHz output appears on pin
10 of the PLL (IC2) and is fed to the
tripler circuit (113) via C72 and
thence to the PLL mixer (TR19) via
C73.
To disconnect the tripled PLL
signal, you simply lift one end of
C73 (marked with a cross on Fig.3).
The output from the external
oscillator is then coupled to the PLL
mixer (TR19) via C73.
Installation can now be completed by wiring the "mode select"
inputs on the oscillator to the back
of the mode switch. This will
automatically select the correct
2.5kHz oscillator offsets when USB
and LSB are selected. Fortunately,
the mode switch connections are
easily accessible on the PCB runn-
Table 1: Channel Frequencies
Channel
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Old Frequency
26 .965
26.975
26.985
27.005
27.015
27 .025
27.035
27.055
27 .065
27.075
27 .085
27.105
27 .115
27 .125
27 .135
27 .155
27 .165
27.175
27.185
27 .205
27 .215
27.225
27 .255
27 .235
27.245
27 .265
27 .275
27 .285
27.295
27.305
27.315
27 .325
27.335
27.345
27.355
27.365
27.375
27 .385
27.395
27.405
ing along the front of the
transceiver. They can be identified
by checking for the presence of
+ 8V on each of the terminals,
when the appropriate mode is
selected.
Adjustments
A few adjustments are necessary
to ensure correct operation. The
first step is to adjust the VCO to
give PLL lock on the new band of
frequencies. This is done by
monitoring the DC voltage at test
point 2 (see Fig.5) and adjusting L14
for 4.5 volts when channel 40 is
selected.
New Frequency
28.285
28.295
28.305
28.325
28.335
28.345
28.355
28.37528.385
28.395
28.405
28.425
28.435
28.445
28.455
28 .475
28 .485
28.495
28.505
28.525
28.535
28.545
28.575
28.555
28.565.
28.585
28.595
28.605
28.615
28 .625
28 .635
28 .645
28.655
28 .665
28.675
28.685
28 .695
28 .705
28.715
28.725
Once PLL lock has been achieved, L2 on the oscillator board
should be adjusted to set the CHl
output frequency to 28.285MHz. To
set the USB and LSB offsets, the
transmitter should be modulated
with a lkHz tone and L3 and Ll on
the oscillator board adjusted to give
28.286MHz on USB and 28.284MHz
on LSB. These adjustments may interact so it is wise to run through
the alignment procedure several
times.
Finally, the receiver sections
prior to the IF stages should be
realigned for optimum performance, as should the driver and
output stages of the transmitter.
This is best done by referring to the
service manual for the transmitter.
Where to get the parts
The 16.6825MHz crystal is
available from Hy-Q International,
1 Rosella St, Frankston, 3199.
Telephone (03) 783 9611. The cost
is $25.23 post paid. Be sure to
specify full details as set out in the
parts list.
BA244 switching diodes or
similar can be obtained from Dick
Smith Electronics Kit Department
(PO Box 321, North Ryde, 2113), or
from VSI Electronics, 16 Dickson
Avenue, Artarmon 2064; phone (02)
439 8622.
F14 ferrite slugs are available
from Neosid Pty Ltd, 23 Percival St,
Lilyfield, 2040; phone (02) 660
4566.
Service manuals for the AX144
CB transceiver can be obtained
from the importer, Santronic Corporation Pty Ltd, 27 Garema Crescent, Kingsgrove, 2208; Phone (02)
599 3355.
16
PRODUCT SAFETY RECALL
DICK SMITH ELECTRONICS PTY. LTD.
NOTICE TO
ALL CUSTOMERS
TEMPERATURE
CONTROLLED
SOLDERING
STATION
Cat T-2000
Sold in all states, may constitute
a safety risk as the power switch in
some units has been found to be
incorrectly wired . The units which
may be affected are fitted with a
meter having a white, translucent
background and bear the legend
"AUST DES REG NO 86081" on the
front nameplate below the
temperature control.
Customers are asked to return
this product as a matter of urgency
to the nearest Dick Sm ith Electronics
Store for immediate attention to the
problem.
We apologise for any
inconvenience caused. Further
enquiries may be made by
contacting Rex Callaghan, Technical
Services Division on (02) 888 3200.
OCT0BER1988
87
BOOKSHELF
Dynamo Design
& Construction
The Homebuilt Dynamo, by Alfred
T. Forbes. Published 1987 by ToddForbes Publishing, Oratia, Auckland, New Zealand. Hard covers,
307 x 220mm, 182 pages, with over
300 illustrations. ISBN O 95977 49 0
4. Price $85.00.
Many people in remote areas are
looking for alternatives to mains
power from the local supply
authority. Often the connection is
just too expensive or they want to
be completely self-sufficient.
Whatever the reason, there is
always a need for books on how to
generate your own power, hence
this book.
It is a practical step-by-step
guide to building a large low speed
alternator. You may wonder why
anybody would bother to build an
alternator when automotive and
truck alternators are available so ·
cheaply. The author explains that
automotive alternators require a
relatively high shaft speed before
they will generate any useful
power. His low speed alternator is
intended for use with windmills or
THE
HOMEBUILT
DYNAMO
DYNAMO DESIGN and CONSTRUCTION
WITH CERAMIC MAGNETS
AN OAIG!N.6:L MOOULAR DESIGN
BASED ON PRACTICAL EXPffi!ENCE
byAJfred1:Fottm
A P!Ctu«I Diary Of Step.by-Step C00$tructk>n
ofaLD#SpeedGeneratorMdtlO'N
lthasbeenpullOuse
water turbines which run at low
speed.
He then goes to describe in great
detail, with the aid of hundreds of
photographs and diagrams, how ,he
made an alternator with an output
of about 1000 watts. However, it is
not a conventional alternator. It
uses high power ceramic magnets
instead of rotor coils and these act
against individual wound stator
coils, all connected via bridge rectifiers to a common output.
The resulting 28kg alternator no
doubt works and the author makes
claims of high attained efficiency.
The only problem is that it is not a
explanatory text is minimal.
At the low cover price they are
worth looking at. They are
available from all Tandy stores.
Mini Notebooks
From Tandy
Engineer's Mini-Notebook: Op Amp
IC Circuits, 48pp, $2.69; Digital
Logic Circuits, 48pp, $2.69; Communications Projects, 48pp, $2.69;
Optoelectronics Circuits, 48pp,
$2.69; 555 Timer IC Circuits, 32pp,
$1. 79; Basic Semiconductor Circuits, 48pp, $2.69. All written by
Forrest M. Mims III. Published by
Radio Shack. Soft covers, 135 x
210mm.
This is a handy series of six
notebooks which present a small
aspect of electronics in a stylised
form; ie, in hand-printed form with
circuits sketched rather than
drafted. In this form it may seem
88
SILICON CHIP
practical alternator for charging
any sort of battery-powered
lighting system. Because it uses
ceramic magnets in the rotor, the
usual method of output voltage
regulation, by varying the field current, is not possible. Hence, as is
normal for any uncontrolled
generator or alternator, the voltage
output roughly doubles for a doubling in shaft speed.
Nevertheless, you must admire
the grit and determination of
anyone who undertakes such a project. It must have taken hundreds of
hours, as just about every step was
done with the aid of simple hand
tools. He even describes the process of cutting ceramic magnets
with a hand-powered diamond saw,
as well as making a magnetiser
powered by a bank of 4700µF 75V
capacitors charged by handpowered dynamo. He also shows
how to precisely cut thousands of
stator laminations with a jig using a
pair of tin-snips !
Our copy of the book came direct
from the author in New Zealand. It
is available via airmail for $A85.00.
See the classified ad section in the
back of this issue.
Towers' IC
Substitution Books
less daunting to the beginner.
Certainly, with all but one of
these booklets being only 48 pages,
they don't take long to read
through. They can be regarded as a
useful source of circuit ideas
although the amount of supporting
Tower's International Digital IC
Selector; Towers' International Op
Amp Linear IC Selector. Both priced at $29.95 from Jaycar stores.
These two books were reviewed
in our June 1988 issue. They were
wrongly stated as being available
from Dick Smith Electronics stores.
They are available from Jaycar
stores. We apologise to the corn- ·
parries concerned and to readers
for any inconvenience.
wpoD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR C
NEW COMTESTERS NOW
AVAILABLE
1.
2.
3.
4.
5.
6.
Tip
Heater holder
Filter p ipe
Filtetcam idge
F ilt91" removing 1..,er
Suction / Hot air
change lr.,er
7. Thermo sensor control
8 . Electric outlet cord
9. Cleaning pin
~
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NEW DESOLDERING GUN
The SC-5000 gun incorporates a motorised diaphragm pump. There are no tubes
or separate compressors. A built-in
thermo sensor circuit controls the 60W
ceramic heater to ensure rapid warm-up.
Exact temperature control prevents damage to sensitive circuitry. The gun can
also be used as a hot blow tool. $399.00
ex tax ($479.50 inc tax)
Optional Stand $18.00
Contact Geoff for all your semiconductor and IC requirements. Our range Is
constantly expanding. Always remember to call "Wood for Chips!"
HIGH QUALITY SILICONE
RUBBER LEADS
~
No more pungent smells when your iron
touches on a test lead. These are the best
in the business from HCK. Super flexible
and we now have the new 2mm sizes
available. Who else offers such a comprehensive range of test leads?
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COMTEST CT 212 and CT225 are the
basic tools for testing and troubleshooting
RS-232 interfaces. They ease installation
and verify the proper operation of the most
widely accepted interface between computers modems etc. Small sized and self
contained both can be easily used with
data comms devices and computers.
Both offer many features not found on
other testers such as clear and logical
layout of the face-plate , a unique Ground
Potential Difference Test function and
optional Three level bidirectional Current
Loop Test, Pulse detect and battery
check.
FUNCTIONS
• Breakout Box
• Interface Signal Monitor
• Signal Simulation
• Ground Potential Difference Test
e Cable Testing (Model CT225 only)
• Parallel Interface Testing (Model
CT225 only)
• Pulse Trap - Optional (P.T./C.L.)
• Current Loop Test - Optional(P.T/
C.L.)
Price
Ex Tax
Inc Tax
Corniest GT 212 $250.00 $285.00
Corniest CT225
$365.00
$415.00
Corniest P.T./C.L. $ 70.00
$ 80.00
Tax exe~ price& are only available where official tax ex&l'Tl>""
tion certificate giving Name. Address and Tax Nun-ber is
provided at time of ordering.
SILICONE LEADS TO SUIT 2mm FITTINGS
HCK-MS101
2mm RED 1m
7.70
HCK-MS102
2mm BLK 2m
7.70
2mm FITTINGS
HCK-8234-1
2mm RED HOOK CLIP 3.00
HCK-8234-2
2mm BLK HOOK CLIP 3.00
HCK-9217-1
2mm RED STKBL PLUG1 .85
HCK-9217-2
2mm BLK STKBL PLUG 1.85
HCK-9225-1
2mm RED TEST PROD 2. 70
HCK-9225-2
2mm BLK TEST PROD 2.70
HCK-9229-1
2mm RED TWEEZERS10.60
HCK-9229-2
2mm BLK TWEEZERS 10.60
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SILICONE LEADS TO SUIT 4mm FITTINGS
HCK-9014-1
HCK-9014-2
HCK-9016-1
HCK-9016-2
HCK-9024-1
HCK-9024-2
HCK-9026-1
HCK-9026-2
HCK-9112-1
4mm RED STGHT 1m
4mm BLK STGHT 1m
4mmREDRIA1m
4mmBLKRIA 1m
4mm RED STGHT 1m
4mm BLK STGHT 1m
4mm RED RIA 1m
4mmBLKRIA 1m
4mm RED SFTY 1m
11.40
11 .40
12.10
12.10
12.25
12.25
12.80
12.80
4.75
FEATURES
Breakout Switches
Probe Points
Probes
DB25 Connectors
Model
Indicators
Fixed
Floating
Weight
Case
4mm BLK SFTY 1m 4.75
4mm RED SFTY RIA 1m4.75
4mm BLK SFTY RIA 1m 4.75
4mm BLK 16A 0.5m
6.85
4mm RED 16A 0.5m
6.85
4mm BLU 16A 0.5m
6.85
4mm YEL 16A 0.5m
6.85
6.85
4mm YEL 16A 0.5m
4mm VIO 16A 0.5m
6.85
4mm BLK 16A 1m
8.70
8.70
4mm RED 16A 1m
8.70
4mm BLU 16A 1m
8.70
4mm YEL 16A 1m
8.70
4mm GAN 16A 1m
8.70
4mm VIO 16A 1m
4mm BLK 16A 1.5m 10.45
4mm RED 16A 1.5m 10.45
4mm BLU 16A 1.5m 10.45
4mm YEL 16A 1.5m 10.45
4mm GRN 16A 1.5m 10.45
4mm VIO 16A 1.5m 10.45
1
1
26
52
1 9V battery
145 X 40 X 90
(Wx H x D)
240g
Clamshell
LED's total
Power
Dimensions
HCK-9120-1
HCK-9120-2
HCK-9123-1
HCK-9123-2
HCK-9209-1
HCK-9209-2
HCK-921 0-1
HCK-9210-2
HCK-9206-1
HCK-9206-2
HCK-9116-1
HCK-91 16-2
HCK-91 19-1
HCK-91 19-2
HCK-91 24-1
HCK-9124-2
HCK-921 4-1
HCK-921 4-2
HCK-9132-1
HCK-9132-2
HCK-9205-1
HCK-9205-2
HCK-9203-1
4mm FITTINGS
HCK-9203-2
4mm/2mm RED ADPTR 1.80 HCK-9230-1
HCK-9227-1
4mm/2mm BLK ADPTR 1.80 HCK-9230-2
HCK-9227-2
HCK-9112-2
HCK-9113-1
HCK-9113-2
HCK-S051
HCK-S052
HCK-S053
HCK-S054
HCK-S055
HCK-S056
HCK-S101
HCK-S102
HCK-S103
HCK-S104
HCK-S105
HCK-S106
HCK-S151
HCK-S152
HCK-S153
HCK-S154
HCK-S155
HCK-S156
25
50
12 terminated,
length 15mm
2 one fixed ,
one free
CT212 CT225
12
25
RD CLMP GRIP 50mm 10.60
BLK CLMP GRIP 50mm10.60
RED COUPLING XHK 1.50
BLK COUPLING XHK 1.50
RED CROCODILE 2A 2.70
BLK CROCODILE 2A 2.70
RED CROCODILE 15A 4.40
BLK CROCODILE 15A 4.40
RED HEX PROBE
3.00
4mm BLK HEX PROBE 3.00
4mm RED HOOK GRIP 9.50
4mm BLK HOOK GRIP 9.50
4mm RED JAW GRIP 14.50
4mm BLK JAW GRIP 14.50
4mm RED ADPTR XSA 3.00
4mm BLK ADPTR XSA 3.00
4mm RED PNL MT SKT 2.95
4mm BLK PNL MT SKT 2.95
4mm RED PNL TW SKT 3.50
4mm BLK PNL TW SKT 3.50
4mm RED SQ PROBE 2.70
4mm BLK SQ PROBE 2.70
4mm RED STKBL PLG 2.70
4mm BLK STKBL PLG 2. 70
4mm RED TWEEZERS10.60
4mm BLK TWEEZERS 10.60
GEOFF WOOD ELECTRONICS PTY LTD
229 Burns Bay Road , (Corner Beatrice St. ) iNc INNsw
Lane Cove West, N.S.W. P.O . Box 671, Lane Cove N .S.W. 2066
Telephone: (02) 4271676, Fax: (02) 428 5198.
8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday.
Mail Orders add $_5.00 to cover postal cha rges.
Next day delivery in Sydney add $5.00.
All prices INCLUDE sales tax.
Tax exemption certificates accepted if line value exceeds $10.00.
BANKCARD, MASTERCARD, VISA , CHEQUES OR CASH CHEERFULL Y ACCEPTED
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I PRODUCT SHOWCASE I
Escort EDM-55
digital multimeter
Do you find ordinary digital
multimeters. hard to use in some
situations? It can be tricky to place
probes on measurement points
while looking at the reading. Here is
a possible solution.
The Escort EDM-55 is a small
probe digital multimeter with a
3-1/2 digit liquid crystal display and
a 6-position rotary function selector. It is auto-ranging (ie, no need to
switch voltage, current or ohms
ranges) and the readings can be
held on the display by using the DH
(data hold) button.
The meter measures DC volts, AC
volts, ohms, diode and continuity.
DC volts can be measured in 5
ranges from 200mV to 500V. The
200mV range has 100µ V resolution
with an accuracy of ± 2 % of
reading plus 4 digits. The input impedance for this low range is an
unbelievable lOOOMO. However,
we were able to confirm that it is indeed lOOOMO.
The 2V range has an accuracy of
± 0.7% of reading plus 4 digits and
an input impedance of 1 lMO. The
20V, 200V and 500V ranges have
accuracies of ± 1.3% of reading
plus 4 digits, and lOMO input
impedance.
The AC function has 4 ranges
from 2V to 500V. The accuracy is
± 2.3% of reading plus 8 digits with
a frequency response of 40Hz to
500Hz. Input impedance is about
lOMO for all ranges except for the
2V range which is 1 lMO.
Resistance is measured in 6
ranges from 2000 to 20MO with accuracy of ± 2 % plus 4 digits for all
ranges except for the 20MO range
which is ± 10% plus 4 digits.
Double layer
capacitors
for memory backup
Where it is necessary, to
power random accessory
memory (RAM) while a computer
is powered down, the designer
essentially has two choices: a
lithium or other expensive long
life battery which will eventually
need replacement or a high value
double layer capacitor. For the
latter approach, Murata have
the AC 200 series of 5.5V
ceramic double-layer capacitors
(compatible with rµost microprocessor and TTL logic), with
values ranging from 18,000µF to
100,000µF (or 0.018 to 0.1
Farad).
To give an idea of their size,
90
SILICON CHIP
The meter also checks diodes by
displaying their forward voltage.
Continuity measurement has a
range of up to 2k0 and the buzzer
sounds when the resistance is
lower than 3000.
The meter is protected against
overvoltage to 700V for the DC and
AC ranges and 250V for diode,
resistance and continuity functions.
Battery life from the two 76A
camera cells is quoted at 80 hours.
(A bit short; don't forget to turn it
off). The batteries are included
with the meter as well as an insulated long probe tip.
The Escort EDM-55 is available
from David Reid Electronics for
$79. Phone (02) 267 1385.
Single pole
circuit breakers
the AC 200 series O. lF measures
only 12.5mm in diameter and
7mm in height. Other values are
smaller, at 11 x 6.5mm, with
5mm pin spacings.
For further information, contact the Australian distributor
for Murata products, IRH Components, 32 Parramatta Road,
Lidcombe, NSW 2141. Phone (02)
648 5455.
With some equipment you just
cannot help blowing fuses and it
becomes expensive after a while.
This can happen with power supplies or with new designs which are
under development.
The solution is to fit one or more
of these thermal circuit breakers
from Potter & Brumfield. They're
Touch screens for
personal computers
Some people like them, others
don't but they are becoming
much more popular. What are
we talking about? Touch screens
for personal computers. In the
past these have used an infrared
grid or membrane immediately in
front of the monitor screen. The
new MicroTouch screen uses
capacitive sensing.
Each screen is made from a
single sheet of glass with a
resistive pattern bonded to its
surface. This provides 1024 x
1024 touch points. The screen
cannot be scratched by pens or
sharp objects and is superior to
plastic membrane screens in optical clarity and durability.
The superior resolution of the
MicroTouch screen allows the
development of comprehensive
menus via the supplied software.
Among the programming tools
are software-controlled or
switch-set data formats, modes
and parameter settings, and a
full function intelligent auxiliary
serial port.
Software is available for IBM
PC AT, XT and compatibles and
for the Apple Macintosh. On the
hardware side, there are two interface cards, an RS232C serial
controller and an IBM PC bus
controller.
The Microtouch screen is
available as a complete video
monitor in kit form to be fitted to
most monitors, from 23 to 68cm
diagonal. Flat panel screens
from 23cm to 168cm are also
available.
For further information on
MicroTouch screens contact
Paul Tenukest at Rand Walker
Pty Ltd, 33/47 Neridah Street,
Chatswood, NSW 2067. Phone
(02) 419 2088.
about the same size as a 3AG
fuseholder . and clip-mount into a
16mm diameter hole.
Priced at $7.80, they're available
from Geoff Wood Electronics.
Phone (02) 427 1676.
Handy logic probe
from Jaycar
The HYT-07 Logic Tester is a
pencil probe which is suitable for
checking all logic families such as
TTL, LS, CMOS etc.
The unit includes a pulse/normal
switch to indicate pulse or continuous signals. Three LEDs plus a
small audio transducer provide the
logic level indication.
In the normal mode, a green LED
indicates a logic LOW, a red LED indicates a logic HIGH and with both
LEDs out, the probe voltage is between HIGH and LOW logic levels.
The audio beeper gives a low note
for a
LOW and a high note for a
(logical!).
Pulses are indicated by a yellow
LED which gives a 200ms flash for
each pulse detected. The audio
beeper also sounds briefly for each
pulse. High or low-going pulses are
indicated when the red or green
HIGH
LED flashes in sync with the yellow
LED.
The probe can detect pulse widths as narrow as 25ns and for frequencies to 20MHz.
The HYT-07 Logic Tester is
available from Jaycar Electronics,
catalog number QT2210.
OCT0BER1988
91
THE EQUIPMENT YOU NEED,
AT BARGAIN PRICES!
ECONOMY SOLDER
SUCKER
•
•
•
•
Light weight
Sturdy construciion
Easy to remove tip
Excellent value for money !
Cat. T11271
$11.95
ECONOMY ANTISTATIC
SOLDER SUCKER
•
•
•
•
L=--"""""'-:j
HUNG CHANG (RITRONJ
20 MHz DUAL TRACE
OSCILLOSCOPE
•Wide bandwidth and high sensitivity
•Internal graticule rectangular bright CRT
•Built in component tester
•Front panel trace rotate,
•TV video sync filter
•Z axis (Intensity modulation)
•High sensitivity X-Y mode
•Very low power consumption
•Regulated power supply circuit
PORTASOL
• Four~~Ps~~~~Po~~h.
Hot Blow . Hot Knife
• No Cords or batteries
• Heavy duty. tip temperature
adjustable up to 400°c .
• Equivalent to 10-60 watts
• Hard working . Average continuous
use 90 mInuters
• Refills in seconds
• Powered by standard butane gas
lighter fuel
• Ran~e of easily replaceable screw
tips mcluded •
• Includes metal stand for the
sotdenng iron when workmg
• Cap features built-in flint for
igniting Portasol tip
• Includes snap case for storage
Cat T12639
$89.95
Light weight
Sturdy construction
Easy to remove tip
Excellent value for money!
Cat. T11 281
$13.95
FREE POSTAGE
FOR SILICON CHIP
READERS
THIS
MONTH
MINIMUM ORDER OF $50 APPLIES
JUST QUOTE THIS ADVERTISEMENT
f!l~~re
~2Y ~ 1~c~ l1~R!r ...
• Sanding
• Engraving
• Grinding
• Polishing
• Cutting
• Dnlling
• Milling
• Erasing . etc.
Features :
Operates on sale , low 12 volts from
mains electricity via AC adaptor
(s_upplied) . Light and easy to handle
with touch switch and lock for
~~~~-ufgi~n~'.~~M~~:~~,r~r;mm
holes In steel . 2 year guarantee
Contents :
• 12V Super Tool
• Plugpack AC adaptor
• 1 spherical milling cutter
• 1 wire brush
• 1 grinding wheel
• 4 drill bits. 0.6, 0.8. 1.0. 1.2mm
• Set of 5 chuck coHets
• 6 eraser sticks
• Instruction sheets
Cat. Tt2300
$64.95
r.9.~~~~w
~~ufib~ PPRJ LL
COMPONENT TESTER is the special circuit with which a
single component or components in circui t can be easily
tested. The display shows faults of components, size of a
component value, and characteri stics of components. Thi s
feature is ideal to troubl eshoot solid state circuits and
components with no circuit power. Testing signal
(AC Max 2 mA) is supplied from th e COMPONENT TEST IN
termina l and the result of the test is fed back to the scope
through the same test lead wire at the same time.
motor, this lightweight (113gm) drill
is ideal for many jobs. Perfect tor
PCB work! Has a 0.8 to 1.2mm
chuck and 1mm drill t}it
Requires 12V 1 AMP.(usewith
~;?~~~302
.....
~ b~ o~u9et ~or q~!ri~~unlike our
opposition·s!
60/40 Resin cored
Cat. No .
Description
Price
T3t000 71mm250gm ..... $8.95
T31002 71 mm500gm .. $15.95
T3t010 .9tmm250gm ... $7.95
T310t2 91mm 500gm
$14.95
T3 t 020 1.6mm 250gm .... $7 .50
T31022 1 6mm 500gm .. . $13.95
T31030 71mm 1 metre .. $1 .50
T31032 91mm 1 metre ... . $1.25
T310341 .6mmlmetre .... $1.00
RS232 BREAK OUT BOX
A simple way o f monitoring RS232
mterface lead activity. Interface
powered , pocket size for circuit
testing, monitoring and paIchmg .
10 signal powered LED "s and
2 spares. 24 switches enables you
to break out c1rcuIts or reconfigure
and patch any or all the 24 acttve
positions
SPECIFICATIONS ,
Connectors : 0825 plug on 60mm
ribbon cable and 0825 socket.
Indicators : Tncolour LED"s tor TD .
RD . RTS, CTS. DSR. CD . TC .
AC . OTA. (E \TC .
Jumper Wires : 20 tinned end pieces
Power : Interface power.
Enclosure: Black. high impact
plastic.
Dimensions : 85 x 95 x 30mm
X15700
$94.95
$19.95
CRT
CRT : s·· (150mm) Flat-faced high brightness CRT with Internal Graticule
Effective d i splay area : 8 x 10 d1v (1 div
10 mm )
Acceleration potential : 2KV
VERTICAL
Operating Modes : CH -A. CH-8 . DUAL. ADO (CH-8 can be inverted.)
Dual modes . Alter . 0.2uls- O.Sms/d1v Chop : 1ms • O.Ss1d1v
CHOP frequency 200KHz approximately.
Deflection factor : SmV1cllv 20V1div + 3 0:o. 12 ranges tn 1-2-5 step w11h fine
con trol
Bandwidth : DC : DC - 20MHz ( 3d8) AC . l OHz - 20MHz 3dBJ .
Rise Time: Less than 17ns
Overshoot : Less than 3 % .
Input Impedance : 1M ohm t
50:o. 20pF + 3pF
Ma ximum Input Voltage : 600Vp-p or 300V (DC ,1- AC Peak)
Channel Isolation : Better than 60 dB at 1KHz .
3800
HORIZONTAL
This instrument is a compact.
~~i &!'!~~~~2u~ii~!~1:n.d A~J;.,~20 ranges m 1-2-5 step wItn rme control
Sweep Magnifier : 5 times (SX MAG ).
Linearity : 3%
TRIGGERING
~~~s~g~~~tETXETRE~iL~( :d1i~~~:~~l~~f:/,~~~(:;2_0~~z~;(~~;;:~~~:~~ore
more Ihan 30MHz) .
Source : INT. CH-A. CH-8 . LINE and EXT.
~~t~~;:ruannd Negative . continuosly variable with level control PULL
1
Coupling :AC . HF-REJ and TV TV SYNC Vertical and Horizontal Sync
!~f~:
~:ii~~~rz~~~~~ye:~~~~ea;ro~~:~?~'
i~~.f~i:n:Y;~~ef>v~~,1~::el)a~:
switched automatically by SWEEP TIME/OIV switch .
TV -V·O.Ss/d1v to 0 .lmsldiv. TV-H :50uts/div to 0 .2uts/div .
X-Y OPERATIONS
X-Y Operations : CH-A : Y a>Cis. CH-B: X axis Highest Sensitivity : 5mVldiv .
COMPONENT TESTER
Component Tester : Max AC 9V a1 the terminal with no load . Max current 2mA
when the terminal is shorted . (Internal resistance is 4.7K ohm)
OTHER SPECIFICATIONS
Intensity Modulation : TTL LEVEL (3Vp-p) : Positive ...... brighter.
BANDWIDTH : DC - 1MHz MAXIMUM INPUT VOLTAG E: SOV (DC + AC Peak)
Calibration Voltage: 0.5Vp-p +/- 5%, 1KHz 1 / 5% Square wave
Trace Rotation :Elec1rically ad1ustable on the fron t panel
Power Requirements : AC : 100, 120. 220. 240V 20W
Weight: 7kg approximately.
Size: 162(H) x 294(W) x 352(D)mm .
only $895
(tax exempt only $775)
Bulk orders, schools, please phone (03) 543 2166 for
special low pricing
METEX
MULTIMETER
METEX
3530
MULTIMETER
This instrument is a compact.
• Dtode testing with I mA fixed
current.
• Audible Continuity Test.
• Transistor hFE Test.
SPECIFICATIONS
Maximum Display: 1999 counts
3 ½ digit type with automatic
polarity indication.
Indication Method : LCD display.
Measuring Method : Dual-slope in
A-0 converter system.
Over-range Indication: ·· 1·· Figure
only in the display.
Temperature Ranges : Operating
OoCtC' + 40-C
Power Supply : one 9 volt battery
(006P or FC- 1 type al equivalent)
Cat .Qg 1530 ........ Normally $109
;ujje~g~a:~rJ~~t9:raf~rdnl~!~~~~d
DC and AC voltage, DC and AC
current. Resistance and Diode ,
Capacitance. Transistor hFE and
Continuity Test. The Oual•slope A-0
Converter uses C-MOS technology
for auto-zeroing, polarity selection
and over-range indication . Full
overload is provided. It is an ideal
instrument for use in the field ,
laboratory. workshop, hobby and
home applications.
Features ...
• Push-button ON/OFF power switch.
• Single 30 position easy to use
rotary switch for FUNCTION and
RANGE selection
• 112" high contrast LCD.
• Automatic over-range indication
wilh !he ·· 1 .. displayed .
• Automatic polarity indication on
DC ranges .
• All ranges fully protected plus
Automatic "'ZERO Mof all ranges
without short circuit except 200ohm
Range which shows "000 or 001 ·· .
• High Surge Voltage protection
1.5 KV-3 KV.
• Capacitance measurements to 1pF
• Diode lesting with 1 mA fixed
current.
• Audible Continuity T esl.
• Transistor hFE Test .
SPECIFICATIONS
Maximum Display: 1999 counts
3 ½ digit type with automatic
polarity indication .
Indication Method : LCD display.
Measuring Method : Dual-slope in
A-D converter system.
Over-range Indication : ·· 1 ·• Figure
only in the display.
Temperature Ranges : Operating
OoC to + 40•C
Power Supply : one 9 volt battery
(006P or FC-1 type of equivalent)
Cat. 091540 ...... .. Normally $139
SPECIAL$79
SPECIAL $109
;ujJe~Q~~1tl~~~~~rdrT)~~~~~,;~d
DC and AC voltage , DC and AC
current. Resistance and Diode . for
testing Audible con11nuity and
transistor hFE . The Dual-slope A-0
Converter uses C-MOS technology
for auto-zeroing, polarity selectron
and over-range indication . Full
overload is provided. Jt is an ideal
instrument for use in the field,
laboratory, workshop. hobby and
home applications .
Features ...
• Push-button ON/OFF IX)Wer switch.
• Single 30 position easy to use
rotary switch for FUNCTION and
RANG E selection .
• 1;2 '" high contrast LCD .
• Automatic over-range indication
wilh the '"1" displayed .
• Automatic polarity indication on
DC ranges.
•f~,~~~j;
.!~~ FfJ·'~~~?r~~~es
without short circuil except 200 ohm
Range which shows " 000 or 001 "' .
• ~~~~~fv~oltage protection
METEX
4500H
MULTIMETER
METEX
M-3650
MULTIMETER
~~e~:;~n:i~it\~~~~:7ii{
capacitance meter and
transistor tester.
J~~;~~c6~~a~a~uJi~;t"1e11ow
~irr~~~~~g~ ~~i~~~(t~e2gJ~~~ts
diode and transistor test. continuity
(with buzzer), capacitance meter, up
to 20 amp current measurement and
comprehensive AC/DC voltage ,
current and resistance ranges.
CHECK THESE FEATURES ....
• Push-button ON/OFF switch.
• Audible continuity test
10A, 41;, digit multimeter
with digital hold,
transistor tester and
audible continuity tester.
The Metex 4500H is perfect for the
0
~~~~~c~~rre;~i:~r~h: ,eand~~~~tof
a 41,2 digit multimeter. This meter is
exceptionally accurate, Uust look at
the specifications) , and yet. still
retains an exceptionally low price!
The Metex 4500H features digital
hold which is normally only found on
very expensive multimeters. This
enables you take a reading and hold
that reading on display even after
you have removed the probes,
simply by pressing the hold button .
CHECK THESE FEATURES ...
• Readout hold
• Transistor Tester
• 4 ½ digit x 1J.2'"(H) LCD
• Audible continuity tester
• Push-button ON/OFF switch .
• Quality set of probes
• ~~t~tt~~~~tcio,~i~ince~~~o
and RANG E selection .
• Transistor test
• Diode test
• Quality probes
• 1;2•· High contrast LCD .
• Full overload protection
•20Amp
• Built in lilting bail
• Capacitance meter
• lnstruciion manual
• r~nug;:
~st\'.f~C~l~N
and RANGE selection.
• Built in tilting bail
• Instruction manual
• Full overload protection
• hFE test
• Battery and Spare fuse
• Diode Tester
• Vinyl case
091550 .
Normally$ 165
Special, only $129
091560 .... Normaliy$ 175
Special, only $159
:~t~~~~
1-9
10+
Cat. S12500 ..... ... Normally $7.95
1-9
10+
25 +
$4.95ea $4.25ea $3.95ea
•
-======a
QUALITY 3mm LEDS
RELAYS
We have a great range of panel
meters at great prices !
Cat.No.
Description
Price
010500 MU45 0-1mA
12.50
010502 MU45 50-0/SOuA 12.50
0 10504 MU45 0-1 OOuA
12.50
0105 10 MU45 O·SA
12.50
0 10518 MU450- 1A
12.50
0 10520 MU45 0-1A
12.50
010525 MU45 0·20V
12 50
010530 MU52E 0· 1A
14.50
0 10533 MU 52E 0-SA
14.50
0 10535 MU45 VU PMelre 14.95
0 10538 MU65 0-SOuA
16.95
010540 MU65 0-1mA
16.95
010550 MU65 0· 100uA
16.95
010560 MUGS 0·20V
16.95
1-9
10+
100+
S. P.D.T. 3Aconnectors ..... S1 4060
$1.50
$1.30
$1.10
O.P.D.T. 3A connectors ..... S14061
$1.95
$1 .75
$1.30
S.P.O.T. 12V Coil 10A240V S141 14
$4.95
ECONOMY
TRANSFORMERS
1-9
10+
2155 240V 6-15V 1A
Cat. M12 155
$9.95
$8.95
2156 240V 6-1SV 2A
Cat M 12156
$14.95 $ 13.95
2840 240V 9V CT
Cat. M12840
S5.95
$4.95
2851 240V 12-6V CT 1SOmA
Cal. M1 2851
$5.95
$5.50
2860 240V 15V CT 250mA
Cat. M12860
$5.95
$4.95
6672 240V 15·30V 1A lapped
Cat. M16672
$14.95 S13.95
$3.95
$3. 75
Cat. No. Col. 1-9
210 140 Red $0.15
2 1014 1 Grn $0.20
210 143 Ylw $0.20
2 10 145 Ora $0.20
10+
tOO+
$0.12
$0.15
$0.15
$0.15
$0.10
$0.12
$0.12
$0.12
:p
/~
U.V. TUBES
'
Fits into standard 15W flou ro holder.
Suitable for Scotchcal, Eprom
erasing etc. As used in ETI Eprom
Erasing Kit.
WARNI NG : Do not look directly into
UV Tubes .
Cat H28600 ............ .. .. . $29.95•
"If ordering by mai l please include
an extra $2 for '"special '" packin~ .
'
,
QUALITY 5mm LEDS
Cat. No. Col. 1-9
2 10150 Red $0.08
2 1015 1 Grn $0.15
2 10152 Ylw $0.15
10+
100+
$0.07 $0.06
$0.12 $0.10
$0.12 $0.10
10TU
U D
POTENTIOMETER
Spectrol Model 534
¼ " shaft.
Save a fortune on expensive
throw away batteries with these
quallty Nlcads and Rechargers!
Size Desc.
1·9
10+ 100 +
AA 450 mA.H $2.95 $2. 75 $2.50
C 1.2 A. H.
$9.95 $9.50 $8.95
D 1.2 A.H .
$9.95 $9.50 $8.95
RCA GOLD PLATED
PLUGS AND SOCKETS
For those who need the ulti mate in
connection. Essential for laser disc
players to get that fantastic sound
quality.
Plug Cat. P10151
$2.95
$2.25
Socket Cat. P10150
=
1
Equiv (Bourns 3540S , Beckman
7256)
Dials to suit 16-1- 11 . 18-1-1 1.
21-1- 11.
R14050 SO R
A14100 SK
A14055 100A R141 10 10K
R14060 200R A14120 20K
R14070 SOOR A14130 SOK
A14080 1K
A14140 100K
A14090 2K
1·9
10 +
$9.95
$9.50
NEW TRANSISTORS
Rod Irving Electronics have two new
transistors which will replace a
multitude of common hard to get
devices.
The PN100 is a NPN genera.) pufP?se
medium power amp and switch with
continuous collector current up to
500mA.
The PN200 is a PNP general purpose
amp at collector currents to 1 Amp.
Both are T0 -82 plastic package
PN100 REPLACES :
PN222t , PN2222 , PN2222A,
PN3585. PN3568, PN3569, PN3643.
PN5133 , 2N22 19A , 2N2222A .
2N3414. 2N341 5, 2N3416. 2N341 7.
2N3700 , 2N3704. 2N3904, 2N4123 .
2N41 24, 2N4401. 2N5088, 2N5210.
PN200 REPLACES:
PN2907, PN2907A. PN3638,
PN3638A. PN3640, PN3644 ,
PN4 121 . PN4 143. PN4248. PN4249.
PN4250 , PN4355. PN4916, PN4917,
PN591 O. 2N2905A. 2N3467.
2N3702. 2N3906. 2N4125. 2N4 126 .
2N4291, 2N4402, 2N4403 , 2N5086,
2N5087, 2N5447 .
PN100 Cat. T9000 1
PN200 Cat. T90002
1·9
10 +
$0.20
$0.18
GOLD INSERT
LOW PROFILE
IC SOCKETS
•
•
•
•
Gold machined pins
Extremely high quality
Anti-wicking.
Ideal for professional use or where
field service of components is
required .
Cat.No. Description 1-9 10+
P10620
8 pin $1.20 $1.10
P10624 14 pin $1 .60 S1.50
P10626 16 pin $1.90 $1.80
P10628 18 pi n $2.00 $1.80
P10630 20 pin $2.20 $2.00
P10632 22 pin $2.40 $2.20
P10634 24 pin $2 .60 S2.40
P 10640 28 pin $2.90 $2.60
P10644 40 pin $3.00 $2.70
Leakproof. long service life batteries
ideal for security systems
emergency lighti ng or as a computer
backup power supply. etc ..
Cat. S1 5029 .
Normally $19.95
1-9
$13.95
,.firirf1
,
WIRE WRAP
IC SOCKETS
These quality 3 level wire wrap
sockets are tin-plated phosphor
bronze .
Cat.No.
Description 1-9 10-t
P10579
8 pin $1 .50 $1.40
P10580 14 pin $1.85 $1.70
P10585 16 pin S1.95 $1.80
P10587 18 pin $1.95 S1 .80
P10590 20 pi n $2.95 $2.70
P10592 22 pin $2.95 $2.70
P10594 24 pin $3.95 $3.50
P10596 28 pin $3.95 $3.50
P10598 40 pin $4.95 S4.50
-
3 ?.
1,9
P10960 3 PIN LINE MALE.
10 ➔
$3.90 .. ...... .............. $3.50
P10962 3 PIN CHASIS MALE
$3.00 ............ .......... $2.50
P10964 3 PIN LINE FEMALE
$4.50 ...................... $3.90
P10966 3 PIN CHASIS FE MALE
$4.95 .................. .... $3.95
,.-•-.~
I 1' t \
I
SPECTROL 64Y
MULTI TURN TRIMPOTS
Cat.No.
R14700
A14710
R14720
R14730
R14740
A14750
R14760
R14770
R14780
R14790
A14800
R1481 0
R14820
R14830
R14840
R14850
Description 1-9
10R ......... $3.50
20R ... .. ... $3.50
SOR ... ...... $3.50
100R ....... $3.50
200R ..... .. $3.50
SOOR .... ... $3.50
1K ....... ... . $3.50
2K .... ....... $3.50
SK ... ....... . $3.50
10K ..... .... $3.50
20K . ...... $3.50
SOK ......... $3.50
100K . ..... $3.50
10 +
$3.20
$3.20
$3.20
$3.20
$3.20
200K ..... .. $3.50
$3.20
$3.20
$3.20
$3.20
$3.20
$3.20
$3.20
$3.20
$3 .20
SOOK ....... $3.50
1M .. ........ $3.50
$3.20
$3.20
1
,!
! '
LOW PROFILE
IC SOCKETS
Save a small fortune on these '·Direct
Import"" low profile IC sockets! PC B
mounting solder tail. Dual wipe. All tin
plated phosphor bronze or berryllium
and dual wipe for reliability.
Cat.No. Description 1-9 10+
P10550 8 pin ... .. ... $0.20 $0.15
P10560 14 pin .......... $0.25 $0.20
P10565 16 pin ..... ..... $0.35 $0.20
P10567 18 pin ........ .. $0.40 $0.30
P10568 20 pin ........ .. $0.40 $0.30
P10569 22 pin .. ........ $0.40 $0.30
P10570 24 pin .......... $0.40 $0.30
P10572 28 pin .. ... ..... $0.50 $0.40
P10575 40 pin .......... SO.SO S0.40
MAIL ORDER HOTLINE
008 335757
•
•
fTOLL FREEJ
LO. _L; -77
-
CHROME LED BEZELS
9mm hole. available 3 colours
Cat. No.
Description
Price
S1 4030 Red ............ .... .... $1.20
S14032G reen
.... ... .... ... $1.45
S14034 Yellow ... ........ . $1 .45
TYPE 1-9
10+
100 +
gp
$0.60
$0.60
$0.50
$0.65
$0.65
$0.60
$0.60
$0.65
$0. 60
$0.50
$0.50
$0.40
$0.60
$0.60
$0.50
$0.50
$0.60
$0.50
9S
9C
15P
15S
15C
25P
25S
25C
$0.70
$0.70
$0.60
$0.70
$0.70
$0. 70
$0.70
$0.75
$0.70
DB 25 CRIMP SPECIALS!
Type 1-9
Femate $2.95
Male .... S2.95
HIGH INTENSITY
RED LED BAR GRAPH
Dimensions :
Overall : 63mm across, 5mm high.
LEDs: 10 x 5mmx: 1mm
10 +
Cat .No.
1-9
$2.75
2 10180
$2.95
TAG TANTALUM
CAPACITORS SPECIALS!
Price
0.48
R16125 16V 10uF.
0.52
R16126 16V 15uF.
0.75
R16128 16V 22uF ..... 0.85
R16216 25V 2.2uF . 0.40
R16220 25V 4.7uF .. 0.70
R16222 25V 6.8uF . 0.70
R16224 25V 10uF .
0.60
R16228 25V 22uF .... 2.40
R16300 35V 0.1uF .. 0.30
R16302 35V 0.15uF .. 0.30
R16304 35V 0.22uF .. 0.30
R16306 35V 0.33uF .. 0.30
R16308 35V 0.47uF ..
R16310 35V 0.68uF ..
R16311 35V 0.82uF .. 0.35
R1631 2 35V 1.0uF.
R16314 35V 1.5uF .
R1631 6 35V 2.2uF .. 0.50
R1 6318 35V 3.3uF .
R16320 35V 4.7uF ..
R16322 35V 6.8uF . 0.80
R16324 35V10uF.
R16326 35V 15uF ...
~~8
R16328 35V 22uF .
3.50
2r~~f4 fgJC
Ji~~in...
DB25 CONNECTOR
SPECIALS!
'
000
00~
cw
.......
,, ~,,CANN
CONNECTORS
10+
$2.50
100+
$1.95
$2.50
$1.95
sn
8(£]<at>]
SPECTROL MULTIDIALS
MODEL 15-1-11
Numberof t urns : 10
Minor Scale Division : 1/500 turn
Shaft Bore: 6.35mm ( 1/4 '")
Finish: Satin Chrome
Body Size: 25.4 x 44.45mm
(1 X 13/ 4 ")
Depth: 25.4mm (1")
Weight: 45.4g (1 .6oz.}
Cat .R14405 .. ..... .. $45.95
SPECIAL, $35.95
MODEL 16-1 -11
Number o f turns: 15
Minor Scale Division : 1/50 turn
Shaft Bore: 6.35mm ( l /4 ")
Finish: Clear Anodize
Body Size: 22.2mm diameter (.875" )
Depth: 22.2mm (.875" )
Weight: 19.8g (0 .7oz.)
Cat.R14400 ........ . $26.95
UnencOded keypad . 10 digit keys
plus two utility keys. Light grey in
colour.
OUTPUT ARRANGEMENT:
Output Pin N°· Symbol
1 ... .. .... ..........N.A.
2 ....... .... ... .... Shield plate
3 ....... ... ....... Colum n2
4 .. .. ........... ..... Aow4
5 ................. ... .Column 3
6 .......... .... ....... Row1
7 .................... Column 1
8 .................... Row 2
9 .. ... ............... Row3
10 .......... .. ........ N.A.
Cat.C 19030
1-9
10 +
100+
$2.95
$2.50
$1.95
SPECIAL, $21 .50
Cat.R1441 0 ....... .. $46.95
SPECIAL, $37.50
FREE POSTAGE
FOR SILICON CHIP
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THIS
MONTH
MINIMUM ORDER OF $50 APPLIES
JUST QUOTE THIS A0VERTISEMENT
.
~
42mm PIEZO BUZZER
S15073 .. .
$7.95
MELBOURNE: 48 A ·Beckett St.
Phone (03) 663 6151
NORTHCOTE: 425 High St.
Phone (03) 489 8866
CLAYTON : 56 Renver Rd .
Phone (03) 543 7877
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MODEL 21 -1-11
Number of turns: 15
Minor Scale Division : 1/100 turn
Shaft Bore: 6.35mm ( 1/4 ")
Finish: Satin Chrome
Body Size: 46.04mm diameter
(1.812")
Depth: 25.4mm (1" )
Weight: 85.g (3oz .)
gJg ~
8:g8
Rod Irving Electronics
0~~
ULTRASONIC
TRANSDUCERS
Designed to transmit at 40k Hz
(L 19990) and receive at 40kHz
(L 19991) with up to 2~V 1/P on the
transmitter. These units can't be
heard and so are ideal for.TV remote
controls. water level de1ectors,
burgalar alarms , motion detectors
and information carriers as they can
be either pulsed or used in the
continuous wave mode.
Full specifications below for design
purposes.
Maximum Input Voltage : 20V rms
0
~~~: ~~=~~~;r!~~N=
o4S ~M~~
POSTAGE RATES :
S1
S9.99
S2.00
S10 S24.99
S3.00
S25 $49.99
S4.00
$50 S99.99
S5.00
$100 S199
$7 .50
$200 $499
S10.00
$500 plus
S12.50
The above postage rates are ~or
basic postage only . Road Frei ght .
bulky and fragile items w ill be
charged at different rates .
All sales ta x exempt orders and
wholesale inquiries to :
RITRONICS WHOLESALE .
56 Renver Rd, Clayton .
Ph . (03) 543 2166 (3 lines)
Errors and omissions excepted
Prices and spec1f1cat1ons sub1ect to
change
110d8 min .
Sensitivity (dB/v/ubar) min. :
- 65 min .
Bandwidth (kHz):
Transmit: 4.0 (at 100c:IB)
Receiver: 5.0 (at - 73dB)
:~~:a~
~s~J;n~;~ari~~~Tii~~~~~
M achmes · Apple 1s a ,eg1s tere-d trademark
lm~=~~rsoo
respect,ve ownets
Receiver: 5000
Cat. L 19990 (Transmitter)
Cal . L19991 (Receiver) . .
·0eno1es 1eg,s1e1ed tradm arks o11he,1
$6.95
$6.95
■[ffil ::E
Phone privacy
junction box
NEW PRODUCTS - CTD
Regulated power
supply from
Oatley Electronics
Bargains in power supplies are
few and far between but this offering from Oatley Electronics rates a
mention. They are an open chassis
unit originally used in Telecom
equipment. They have two outputs,
24 volts DC rated at 1.3 amps and
32 volts AC also at 1.3 amps. While
these ratings are fairly modest, the
Hand-held 2-metre
transceiver
Captain Communications is
now stocking the very small learn
u2A/ A, a palm sized transceiver
for the 2-metre amateur band. It
measures just 11. 7cm high,
5.8cm wide and 2.8cm deep.
Features include 10 programmable memories, offset capability, LCD readout, 2.6 watt output
and 32 built-in sub-audible
codes.
For further information, contact Captain Communications on
(02) 633 4333.
94
STLICON CHIP
transformer is a bulky fully encapsulated unit rated at 140VA.
This means that it could deliver
over 4 amps at 32 volts AC. Essentially then, you get the makings of a
much bigger supply which could be
either fixed or variable.
Full circuit details are provided
plus suggested modifications for
making a fully-variable supply.
Price is $26.95 plus $10 for freight.
For further information contact
Oatley Electronics on (02) 579 4985
(see advert on page 100).
If you thought the Line Grabber
for telephones featured in the
March 1988 issue of SILICON CHIP
was a useful idea but didn't fancy
building it, here is an alternative.
The PTl 15 Privacy Junction Box
from Arista is the prototype of the
Line Grabber. The difference is
that the PTl 15 is fitted with US
modular phone plug sockets rather
than Telecom sockets.
It performs exactly the same
function as the Line Grabber; if you
pick up the phone all other phone
extensions on the line are unable to
listen in. It is priced at $32.95 from
all Arista outlets.
Cassette salvage
and repair kit
I
Hands up all those readers who
have at least one partly destroyed
cassette in their collection but
which they're still loath to throw
out. Maybe the case is buckled, the
tape broken or tangled, or perhaps
it is jamming.
Now there is a solution in this
handy repair kit. It comes with a
spare cassette housing (handy if
you have to destroy one of those
housings which are glued instead of
screwed together), splicing bar,
razor blade and splicing tape.
There is even a little rewinding
knob which is much more effective
than rewinding a loose tape with a
pencil.
The kit is good value at just $2.95
and is available from David Reid
Electronics, 12 7 York Street,
Sydney 2000. Phone (02) 267 1385.
Hydraulic hole
puncher makes
metal work easy
Any tradesman who has laboured over the process of cutting clean
circular holes in metal panels will
love this appliance. It is designed to
punch holes in any sheetmetal including copper, brass, aluminium
and the toughest of them all,
stainless steel.
Essentially it is an updated version of the screw punch and die set
except that now the die is pulled
through the sheet metal by a
hydraulic ram. It works on the same
principle as a hydraulic jack - you
pump the handle to apply pressure
to a larger cylinder which does the
work.
If you've sweated when using the
old screw punch and dies you'll
wonder why this wasn't invented
years ago.
It is available in a number of versions. Pictured is a portable unit,
type HP-1, with an ability to punch
round holes from 10mm to 80mm in
diameter or 20 to 50mm square
holes. Maximum material thickness
ranges from 1.6mm in stainless
"Sensational Price Offer"
a:
w
0
a:
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..I
ci
:I
I
ffi0
IC
0
..I
ci
:I
l
~
CONTACT
CONTACT
ELECTRONIC PARTS
COMPUTER SPECIALS
DB8
DB15
DB25
0837
PLUG
PLUG
PLUG
PLUG
80c
70c
85c
1.85
DB8
DB15
DB25
DB37
SOCKET
SOCKET
SOCKET
SOCKET
80c
70c
85c
2.00
DB8
DB15
DB25
DB37
BACK SHELL
BACK SHELL
BACKSEHLL
BACKSEHLL
80c
80c
80c
1.50
CARD EDGE CONNEClORS
20 WAY IDC PLUG
34 WAY IDC PLUG
1.75
2.25
MACHINED IC SOCKETS
8
14
18
18
20
22
24
28
40
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
55c
70c
85c
80c
1.00
1.25
1.30
1.30
2.25
CONTACT
COMPUTER SPECIALS
MATH CO-PROCESSOR
SWITCH BOXES
40
350
585
$750
$1250
$1900
8087 • 3
8087 • 2
80287 • 8
80287 • 10
80387 • 18MHz
80387 • 20MHZ
12
COMPUTER POWER SUPPLIERS
150W
200W
200W COMPACT
r05
165
155
MOTHER BOARDS
XT TURBO 8MHZ ZERO RAM
AT 4 LAYER 12MHZ ZERO RAM
386 18-20MHZ ZERO RAM
1210
650
$3000
RS232
RS232
RS232
RS232
•
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•
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3WAY
4WAY
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CENTRONICS
CENTRONICS
CENTRONICS
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48.00
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58.00
85.00
58.00
81.00
65.00
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ADD ON CARDS
CGAfHORYi
MGA PRINT R PORT)
MUL I 1/0+FDC
E PROM WRITER CARD
78.00
115.00
120.00
199.00
"RED HOT FAVOURITES"
LED 5MM ROUND
RED-GREEN-YELLOW
10c
VOLT REGULATORS 1.2AMP
HARD DRIVES
SEAGATE ST225 20MEG
$480
7805 TO 7824
7905 TO 7924
50c
50c
TRANSISTORS
HAND SCANNER
HS2000
$480
2N3055
TIP 31 C
Suite 2 - 283 Burbridge Road
Brooklyn Park
SOUTH AUSTRALIA 5032
PH. 08 • 234 - 0240
Fax 08 • 352 .• 1449
Mall Order
Postage
Less than $50 ............................... $3.50
$50 • $99 ...................................... $4.50
$100 • $250 .................................. $7.00
NxNe $250 ................................ $10.00
Heavy Items adds extra
0
BANKCARD O MASTERCARD O VISA
Gard No .............................................. ..
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50c
ALL PRICES INCLUDE SALES TAX
WHOLESALE ENQUIRES WELCOME
PRICES VALID WHILST STOCKS LAST
CONTACT INTERNATIONAL
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EXPIRY DATE
Signature: .... .... .......... .......................... ... .... ...... .. ............. .
(Note: unalgned credit card mall ordera cannot be accepted)
Name: ................................................. .......................... .
Address: ......................................... ............................... .
.. .. .. .. .. .. . .. .. .. .. .. ... .. .. . .. .. .. .. .. .. .. .. .. .. . Postcode: .................. .
(Please allow 14 DAYS for normal mall and bank clearance delays)
I
Mailbag -
continued from page 3
pointer to relevant documents put out
by these organisations.
I enjoy your projects, my most recent effort being the 1GHz Frequency
Counter (which is a ripper!) but I
think that learning to understand
both the theory and the application is
as important, if not more so, than the
feeling of achievement. In this regard
the explanations provided in the articles are usually pretty complete but
in this case I feel I have missed out.
A final emphasis is that while
many people consider the 'rules' set
by government controlling bodies to
be irksome, I know that you will agree
that we need the orderliness they
seek to achieve. It follows that we
need to be continually aware of these
requirements and that in publishing
construction projects you have some
obligation to quote the specific provision of standards or government
regulations applying to the project.
P.
J.
Lees
Jolimont, WA
The Department of Transport and
Communications has allocated a frequency of 304MHz in its Interim Document RB243. This covers personal
safety and security radio systems.
Transmitters operating on this frequency are restricted in their
equivalent radiated power to less than
100 microwatts. The occupied bandwidth of emissions from the transmitter must not exceed 1D0kHz.
Please see other correspondence on
this project in the "Ask Silicon Chip"
pages of this issue.
Caution on the Discolight
While noting the serious and
responsible approach to electrical
safety standards and practices taken
by the magazine, I feel I must point
out an oversight in the wiring of the
"Discolight" appearing on pages 44
will
and 45 of the August issue of SILICON
CHIP.
According to the parts list only the
rear panel is of aluminium and
therefore the front is plastic. On the
front you show a mains switch (S6)
with a metal toggle and frame; also a
number of small toggle switches and
two pots with aluminium knobs. All
these are probably connected
together and appear not to be mainsearthed. In the event of damage or
failure of the mains switch the front
panel may acquire mains potential.
Similarly, but less likely, a failure
in the internal circuitry could place
mains potential on the tracks of pots
and contacts of the switches, posing a
risk of leakage or breakdown to their
respective frames.
If an aluminium front panel had
been specified then it could be
securely mains earthed and the unit
rendered safe. I believe this is required under SAA regulations. As an
alternative, the mains switch at least
should be earthed or replaced with a
plastic enclosed type.
Hoping you can bring this matter to
the attention of your readers and kit
suppliers.
Frankly, the likelihood of the
specified heavy-duty switch breaking
down is extremely remote. We have
never heard of a single instance of a
mains-rated switch breaking down to
frame. And the likelihood of the the
optocouplers breaking down and making all the circuitry live, at mains
potential, is even more remote.
It is also standard practice with most
kitset suppliers to use screen printed
plastic front panels. Still, it would be
good wiring practice to earth the metal
bush of the mains switch and those of
the two potentiometers.
~
~~
U~
~
UV,,,,
-
C g~
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--'~
..~au
·co
•~~
RCS Radio Pty Ltd is the only company which
manufactures and sells every PCB & front panel
published in SILICON CHIP, ETI and EA.
651 Forest Road, Bexley, NSW 2207
Phone (02) 587 3491 for instant prices
96
SILICON CHIP
Wire stripper
and crimper
P. Allison
Summer Hill, NSW
ft~
0
steel to 3mm in aluminium.
A larger version, the NP-2,
punch round holes from 15mm to
150mm in diameter or 20mm to
100mm square holes. Other portable models have die heads which
are separate to the hand-powered
section, to enable hole punching in
awkward spots.
For production use, there is the
model EG-3 which is designed for
bench mounting.
For further information on this
range of hydraulic hole punchers
contact Stainelec Industries, 26
Boola Avenue, Yennora, NSW
2161. Phone (02) 632 6797.
Some combination wire strippers
and crimpers are not very effective.
Perhaps they don't strip wire
without nicking the conductors.
Some are hopeless at the task of
crimping connectors. So if you are
buying one of these tools be aware
that if it is very cheap, it might not
be the bargain you expect.
This combination wire stripper
and crimper from Geoff Wood Electronics works very well indeed. It
automatically adjusts its jaws to
strip the insulation from almost any
size of wire without nicking the conductors. It has an effective wire
cutter as well as being able to cope
with three sizes of crimp connectors.
It is priced at $34.95 from Geoff
Wood Electronics - phone (02) 427
1676.
~
ASK SIUCON CHIP
Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line
and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097.
Video distribution
system has ghosts
on one channel
Could you please give me some
advice on a video distribution
system? I've shown a diagram of
what I would like to achieve - ie,
the VCR or off-air signals available
at any of four TV sets. I would install a masthead amplifier as
decribed in the July 1988 issue of
SILICON CHIP because I live about
10km from the transmitter.
We don't have line of sight to the
transmitter because I live in a gully
and have to use an anti-ghost TV
antenna. The picture on the ABC is
OK but on TVT-6 it is very bad with
vertical bars on the screen about
10mm wide. Do you think the
amplifier would improve the situation or not? Also, would the
amplifier be suitable for UHF CB?
(G. O'S., Rosetta, Tas).
• Your method for making the TV
and VCR signal available to four
TV sets should be satisfactory but
Enclosure design for
a widerange speaker
I am interested in a reflex
cabinet for a British made 8-inch
Richard Allen loudspeaker with a
frequency range of 45Hz to 17kHz.
It has a 4-inch (10cm) magnet.
Would it be possible for you to give
some idea of internal measurements in inches or centimetres? It
could perhaps be 30 inches high
and 18 inches wide with a specified
depth and a vent or port to suit.
Have you any suggestions? (S. N.,
Devonport, Tas ).
• Dear, oh dear. We don't have an
inch rule. What are we going to do?
Seriously, without having the
Thiele-Small parameters for your
loudspeaker, it is probably a waste
of time designing a vented
enclosure for it. We don't even
VCR
,--------tOUTPUT INPUT------.
BEDROOMS
1
2
MAST HEAD
AMPLIRER
(SC JULY 88)
1----t
TWO-WAY
COMBINER
TWO-WAY
SPLITTER
FOUR-WAY
SPLITTER
KITCHEN LOUNGE
Fig.1: proposed arrangement for distributing VCR and off-air signals
to four TV sets.
unless you have fairly weak TV
signals to begin with or the expected losses via the combiners and
splitters are high, the masthead
amplifier may not be necessary. It
certainly will not improve the
reception on TVT 6 if you have vertical bars down the screen. These
are vertical sync pulse ghosts and
are symptomatic of very bad reception conditions.
Unless you can obtain a more
directional antenna for channel 6
and/or orient the antenna so that
the ghosts are placed in the null
points of the antenna (for a Yagi,
deep nulls are present in the sides),
no improvement is possible. We
assume that your antenna is on a
high mast.
Yes, the masthead amplifier will
work on UHF CB signals but you
should be aware that UHF signals
are even more directional than the
VHF TV signals that are presently
giving you problems. If you are in a
"shadow" as far as UHF signals
are concerned, it is unlikely that
any masthead amplifier will help
you.
know the free-air cone resonance
although it is probably around
50Hz or so, we'd guess.
It's a stab in the dark, but we'd
suggest you install the loudspeaker
in a sealed (ie, with no vent or port)
enclosure with a capacity of around
40 litres or so. As for suitable
dimensions, we suggest a cabinet
with internal dimensions 580mm
high, 340mm wide and 220mm
deep. Use 12mm or 20mm thick particleboard or plywood and fill the
enclosure with Innerbond (bonded
acetate fibre) wadding.
and July 1988) without the cost of
an expensive rack mounting box.
Would you please advise readers
where they may obtain the following: (1) LM833 op amps; (2) pots
with indents; (3) balance control
(MN) as specified; (4) PC-mounting
DPDT push-on push-off switches. To
my knowledge they have never been
catalogued by any of the four major
suppliers. In fact, I have been informed that as far as the pots are
concerned, they are not available.
Your assistance in this matter
would be greatly appreciated.
(D. G., Julatten, Qld).
• Pots with indents are a big supply problem at the moment but you
can obtain suitable pots without the
indents, including the balance control, from Jaycar. They can also
supply the LM833s and the
switches.
Parts for the
Studio 200 preamp
As a reader of your magazine
from the first issue I am currently
trying to put together your Studio
200 control unit (described in June
OCTOBER1988
97
2.2pf
INPUT- I - - - - - - - - - - RF
OSCILLATOR
A.UOIO
OUTPUT
LOW PASS
ALTER
3.3pf
QUENCH
OSCILLATOR
Fig.2: block diagram of the front-end of
the Remote Alert/Doorbell. Its operation
is explained in the text.
Self-oscillating detectors
are intriguing
I am intrigued by the detector
used in the "Remote Alert/
Doorbell" described in your
August 1988 issue. Can you supply any further information other
than the fact that "whenever a
signal is received, this stage
oscillates at 304MHz" please. (J.
E., Bull Creek, WA).
• To paraphrase a cer tain old
TV show, "you asked for it". As
you have guessed, the circuit
operation is a lot more complicated than our short description indicates. When you've read
the description, you'll see why
we gave the brief explanation.
We based the circuit on one
featured in an article in the IEEE
Transactions on Consumer Electronics, Volume CE-33, No 3,
Electronic ignition
for model aircraft ·
As a novice electronics hobbyist,
I find your down-to-earth explanations of electronic circuits and component functions most helpful. I am
a radio control model aircraft enthusiast and am in the process of
building your optical tachometer.
The reason for this letter is to ask
if you can come up with an electronic spark ignition for model aircraft engines, particularly 4-stroke
models. Keep in mind that such a
design would have to be as light as
possible and must not interfere
with the receiver. (D. De V.,
Toowoomba, Qld).
• Your suggestion is a good one
98
SILICON CHIP
.,.
Fig.3: Q2 is a super-regenerative receiver
which consists of both an RF oscillator and a
quench oscillator.
August 1987. The relevant part
of the circuit is reproduced here
as Fig.3.
The circuitry associated with
Q 2 is a ctually a super regenerative receiver which consists of both an RF oscillator and
a quench oscillator. The RF
oscillator comprises Q2, 1 2 and
the 22pF, 3.3pF and 2.2pF
capacitors. It runs at close to the
transmitted centre frequency (in
this case, 304MHz).
The quench oscillator comprises the series inductor 13, a
lkO r esistor and a .OOlµF
capacitor at the emitter of Q2.
The RF oscillator rapidly alter-
although we don't have a lot of
background info on this topic. If you
or other readers have info on model
aircraft ignition it would be a help
in the development of a suitable
circuit.
New life for
cassette players
I read with interest the article
"New Life for Old Cassette
Players" in the March issue of
SILICON CHIP. I feel that it was an
excellent article for all young
beginners just entering electronics.
It will encourage many to retrieve
an old tape player from a dusty
shelf and get it going again.
I would like to see a future series
nates between an oscillatory and
non-oscillatory condition at the
quench frequency rate. The
function of the quench oscillator
is ·to ensure that continuous
oscillation does not occur in the
absence of an input signal. In effect, the RF oscillator "squeggs"
(ie, gives very short bursts of
oscillation) at a rate set by the
quench oscillator.
When a modulated signal is
received, the fluctuating RF level
of oscillation causes the DC level
at the base of Q2 to vary accordingly. This signal is then fed via
inductor L4 to the following
amplifier stage.
of service notes and techniques for
servicing cassette decks, radios .
and CD players similar to the fine
articles which we regularly read in
the Serviceman's Log column.
With the above idea in mind, I
would like to ask you, or one of your
readers, if there is a simple solution
to remedy the newly arrived problem of auto-reverse cassette
players continually changing direction when a tape has been inserted.
I don't mean changing the direction
when a tape has come to the end of
one side, but as soon as the tape has
been inserted and the mechanism
activated. The machine then continually clicks back and forth and
will not stop.
It seems after watching the
machine that the mechanism is
under some tension and cannot
decide which direction to stabilise
on.
I have seen several machines
which exhibit the same characteristic and hope that you can provide
an answer. (R. P. , Latrobe ,
Tasmania).
• We have not experienced this
problem. Can any reader provide
the answer?
Power supply
for . video light
In the November 1987 issue of
SILICON CHIP you featured a 12V
power supply for a car radio which
was rated for a continuous 1 amp.
Can I use it to supply a 12V quartz
halogen video light that runs from a
12V dry battery? The light is rated
at 100 watts. (E. D., Cheltenham,
Vic).
• The 100 watt rating on the light
is the essential clue. Dividing that
figure by 12V gives a current requirement of no less than 8.3 amps.
That's a very high current for any
dry battery to sustain and even the
average car battery would only last
for a few hours at that rate.
The alternative of a mainspowered 12V 8.3 amp continuously
rated supply would not be a cheap
item by any means; ideally it should
be well regulated to ensure long life
and correct colour temperature of
the lamp. We have not described a
suitable supply but if there is sufficient demand we would do so.
As an easier alternative, why not
enquire at a lighting supply store
which stocks quartz halogen spot
lamps? You may be able to
substitute a 240V-rated lamp which
would do the job without any need
for a power supply.
Wants information
on semiconductors
Is there a data book available
which explains the full functions of
most semiconductors? For example,
with a unijunction transistor (UJT}:
when the anode voltage is 0.5V
above the gate, the UJT will conduct. What I am looking for is some
publication which goes into some
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Name ......... .... ....... .. ... ...... .. ..... ... ..... ... ..
Address .
Suburb/Town .. ....... .. .
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detail on how these semiconductors
will activate or de-activate. (A. M .,
Browns Plains, Qld).
• We can understand your problem. General Electric published a
number of handbooks which were
very good on explaining how
devices such as unijunctions worked (eg, GE Transistor Manual, GE
SCR Manual). As far as we can
determine though, these books are
no longer available and we are
unable to nominate a suitable
alternative.
Actually, the device you are
referring to is not a unijunction
transistor (which has two bases
and one emitter) but a PUT
(programmable unijunction transistor). This was a device developed
by General Electric as a more
predictable "unijunction". A PUT is
actually an "anode gate silicon controlled rectifier" (SCR} which is a
variant on the more common
cathode-gate SCR.
The ultimate answer to this need
for a data book which explains how
these special semiconductors work
will be provided when we get our
series on Discrete Devices under
way. Unfortunately, we can't make
any promises on the starting date.
Notes & Errata
Studio 200 Stereo Control Unit,
June1988: experience with the control unit when teamed with a
number of power amplifiers has
shown that the combination can
oscillate supersonically when the
Treble control is at maximum and
the Volume control is at high settings. While these are abnormal
control settings, if oscillation is
allowed to persist it may damage
the power amplifier or the
speakers.
To prevent the condition occurring, we suggest that an additional
270pF capacitor be connected
across the 4. 7k0 feedback resistor
for IC2 in each channel. In addition,
a 560pF capacitor should be connected across the volume control
potentiometer; ie, one 560pF
capacitor across VR1a and one
across VR1 b.
Remote/Alert Doorbell, August
1988: when setting the transmitter
frequency for Ql, do not connect
pin 15 of IC1 to the + 12V supply.
This can damage IC1. Instead,
disconnect the 47k0 resistor from
pin 15 and connect it instead to the
+ 12V supply to make the transmitter run continuously.
OCT0BER1988
99
T CEN·1·
Cash in your surplus gear. Advertise it here in Silicon Chip.
PROJECT REPAIRS
PROJECT REPAIRS - Having trouble
getting your EA/ETI/SC kit to work?
Phone (03) 7 49 3480 for estimate or
send kit to K. Hunter, 5 Yatama Crescent, Werribee 3030.
FOR SALE
NEW 64K-256K PRINTER BUFFER
design release. VER 4.0 and REV G
boards now available. Double-sided
PCB, EPROM and instructions:
$39 .00. Optional additions include 2
by 7 -segment LED front panel display
of percentage full, 1 to 99 copies
select, 3 polled computer inputs,
printer switches, computer switches,
and serial converter boards. For a free
catalog sent a 37c stamp to: Don
McKenzie, 29 Ellesmere Crescent,
Tullamarine 3043.
RADIO/TV RESTORERS - We have a
large stock of new valves . Send SAE
for list or phone Shellharbour TV Service , 268 Mary St, Shellharbour,
2529. (042) 95 1175.
EPROMS 2764 $4, 27256 $6,
27512 $10, 74HC374 $1, uP6800
$3, 6802 $4. All minimum quantity
100. Transistors - PNP 2N2907 A 5c,
mimimum quantity 1000. Ask for Winnie on (02) 344 0173 after 6.30pm.
Oatley Electronics - for exclusive and
selected kits. These prices will not be
repeated.
Passive lnfrared Movement Detector
Kit (SILICON CHIP, Dec. 1987): a PIR
detector employs body heat detection
and represents the most reliable type of
detector currently available. This unit
employs a dual pyroelectric detector
and its performance is equalled by only
the more expensive commercial
equivalents. With the wide-angle lens
fitted this unit has a view of 90 ° and a
useful range of more than 1 0 metres.
The narrow angle lens gives a useful
ran ge of more than 25 metres! The kit
include both the lenses and a scaled
pattern of the lens housing. The lens
housing consists of thin tin plate which
100
SILICON CHIP
is easy to cut out and solder. On
special until the end of this month for
an incredible low price of only $44.95
including p&p (normally $57 .95).
Metal box not included.
Satellite Siren/Backup Siren Kit (EA,
Sept. 1987): comes into action when
the main alarm power is interrupted or
the vehicle battery is disconnected.
This unit is simple to install; it requires
only two connections to your existing
alarm system. What's in the kit? - 1
PCB plus kit components, 1 battery
holder, 1 barrel key switch with two
keys, and a suitable plastic case. All
this for only $39.95 incl. p&p (normally $55.00). PCB and components kit
only $16.90.
UHF Remote Controlled Key Kit (EA,
Jan. 1986): this multi-purpose unit is
on special for only $41.95 plus $2.50
p&p. For full details see our advert in
SILICON CHIP, July 1988.
Stereo VU Meter Kit (EA, June 1987):
the kit includes the stereo meter movement and is priced to clear at an incredible low price of only $9.95 (normally
$17.95) plus $1.50 p&p. Only while
they last.
FM Transmitter Kit: professional quality - low noise - has pre-emphasis suits microphones, guitars, instruments
etc. See EA, Sept. 1986. You can buy
the complete kit which even includes
the preamp for only $14.95 plus $1.50
p&p to clear stock.
Want more information on a listed
kit? Just send us $1 .00 and a stamp
and we will send you a complete copy
of the instructions. If at a later stage you
decide to buy the kit, simply tell us not
to include the instructions and subtract
$1.00 from the kit price.
Mail address: Oatley Electronics, PO
Box 89, Oatley, NSW 2223.
Shop address: 5 Lansdowne Parade,
Oatley West, Sydney, NSW 2223.
Phone (02) 579 4985.
Shop hours: Mon; Wed; Thur; and Fri.
between 10am and 5pm. Also Saturday between 10am and 1 pm.
Telephone orders: Bankcard, Mastercard and Visa Card accepted with
phone orders. Minimum order on a
credit card Is $15.00
Mail orders: Bankcard, Visa Card,
Mastercard, cheques and postal
money orders accepted.
Advertisers Index
Allied Capacitors .................. 11
Altronics ....................... . 40-43
Arista Electronics .... .. ...... .. ... 39
Avtek ........ ..... ...... ......... .... IBC
Bell lRH .. ...... ........ ...... ........ 19
Contact International .......... .. 95
Dauner Electronics .............. 4 7
David Reid Electronics .... ...... 13
Dick Smith Electronics .. .. . 62,63
82,83,87
Elmeasco .. ........ .. ........ ...... IFC
Geoff Wood Electronics .... .. .. 89
Jaycar Electronics ...... .... 24-27
72-75
J.V. Tuners .. .. .... .... .. ...... .... . 47
Kenwood Australia ... ... .. .... OBC
Marantz Australia ............ 50,51
Pre Pak Electronics .. .. .... .. .. .. 69
RCS Radio .... .... .. .. .............. 96
Rod Irving Electronics ..... 34,35
92,93
Scan Audio ........ .. .......... ..... 11
PC Boards
Printed circuit boards for SILICON
CHIP projects are made by:
• RCS Radio Pty Ltd , 651
Forest Rd, Bexley, NSW 2207 .
Phone (02) 587 3491 .
• Jemal Products, 5 Forge St,
Welshpool , WA 6106. Phone
(09) 350 5555 .
• Marday Services, 2139 Great
North Rd , Avondale, Auckland ,
NZ . Phone 88 5730.
BOOKS & PLANS
LOW SPEED GENERATORS for windmills, water turbines, steam engines.
The definitive book: "The Homebuilt
Dynamo" (1987) , 182 pages, 8.5" x
12", hardback. Generator design and
construction with ceramic magnets.
Complete plans, 268 photographs,
step-by-step construction details.
$A85.00 postpaid airmail (brochure
$A5.00 refundable). Todd-Forbes
Publishing, 627 West Coast Road,
Oratia, Auckland .
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r-:- - - - - - - 1 nease send me further information and detailed broGhures to:
I Name _ _ _ _ _ __
II __________
_ _ _ _ _ __
Address _ _ _ _ _ _ _ _ _ _ _ _ __
II
Postcode
Post to Avtek Data Communications, P.O. Box 651,
LANE COVE 2066.
_
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