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Leo Simpson and Greg Swain present ...
Hifi review:
Marantz' s super
new CD-94 CD player
Aeg1s1ered o, Ausiraha Pos; Publica11on No NBP 9047
Fluke. First Family of DMMs.
When accuracy, performance and value
are important, professionals the world over
look to Fluke - the first family of DMMs.
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There's the low-cost 70 Series - the
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tough 20 Series - totally sealed and built
to survive the dirtiest, grimiest, roughest
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to withstand the rigors of the field service
environment. The precise 8060A Series the most powerful and complete test and
measurement system available in~ handheld package. And, of course, the versatile
Bench/Portables that carry on the Fluke
tradition for precision and durability in
lab-quality bench instruments.
Fluke comes in first again with the
world's largest selection of quality accessories to help extend the capabilities of
your DMM even further.
There's no need to look anywhere else.
Uncompromising Fluke design and leading edge technology are the reasons why
attempts at imitation will never fool the
millions of professionals that accept nothing less than a Fluke.
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• TASMAWA George Harvey (003) 31 6533 (002) 34 2233
• VICTORIA Radio Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 4301 • A.W.M. Electrical Wholesalers
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JANUARY 1 988
FEATURES
4 The Evolution of Electric Railways
12
32
68
86
by Bryan Maher
Pt.3 - The problem of braking
The 1987 CESA Hifi Awards by Leo Simpson
Best amplifier, tuner, CD player & loudspeaker
Marantz's Elegant New CD Player by Leo Simpson
For the audio connoisseur
OTC'S Automatic Seaphone Service by Leo Simpson
Ship-to-shore dialling for all boat owners
Digital Fundamentals, Pt.3 by Louis Frenzel
Teach yourself digitial electronics
WHAT WERE the best hifi
products for 1987? We name
the winners of the 1987 CESA
Grand Prix hifi awards on
page 12.
PROJECTS TO BUILD
14 High-Performance UHF Antenna by Leo Simpson
Uses readily available materials
24 Update the Sound of Your Telephone by John Clarke
Simple circuit fits in your telephone
:t 18.5V power supply by John Clarke
The ideal supply for your workbench
48 1 GHz Digital Frequency Meter Pt.3 by Steve Payor
Construction, calibration a nd troubleshooting
64 Subcarrier Adaptor For FM Tuners by John Clarke
Listen to hidden FM transmissions
71 The Flexo Shortwave Antenna by Ed Noll
Improve your shortwave reception
38 Dual Tracking
IF YOU CAN do basic
metalwork you can build this
high-performance UHF
antenna. It's a four-bay bowtie design to cut down on
interference and ghosting.
Details page 14.
SPECIAL COLUMNS
56 Serviceman's Log by the original TV serviceman
When the chips are down
76 Amateur Radio by Garry Cratt
Amateur television: getting started
82 The Way I See It by Neville Williams
Information has its place, but what about knowledge
DEPARTMENTS
2 Publisher's Letter
3 Mailbag
10 News & Views
22 Circuit Notebook
43 Bookshelf
79 Product Showcase
94 Ask Silicon Chip
96 Market Centre
HERE 'S THE ideal power
suppl y for your workbench.
This is a dual tracking design
giving up to ± 18.5V, and
features voltage metering and
short circuit protection. Turn
to page 57.
JA NUARY 1988
1
SILICON CHIP
PUBLISHER'S LE'I-IER
Publisher & Editor-In-Chief
Leo Simpson, B.Bus.
Editor
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Regular Contributors
Neville Williams, FIREE, VK2XV
Bryan Maher, M.E. B.Sc.
Jim Yalden, VK2YGY
Garry Cratt, VK2YBX
Jim Lawler, MTETIA
Photography
Bob Donaldson
Editorial Advisory Panel
Philip Watson, MIREE, 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 ttie publisher. Kitset
suppliers may not photostat articles without written permission
of the publisher.
Typesetting/makeup: Magazine
Printers Pty Ltd, Waterloo , NSW
2017 .
Printing: Macquarie Publications
Pty Ltd, Dubbo, NSW 2830.
Distribution: Network Distribution
Company.
Subscription rates are currently
$42 per year ( 1 2 issues). Outside Australia the cost is $62 per
year surface mail or $120 per
year air mail.
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 B.,each , NSW
2097 . Phone (02) 982 3935 .
ISSN 1030-2662
* Recommended and maximum
Australian price only .
2
SILICON CHIP
There's a UHF antenna
in your future
Some time ago we planned to publish a four-bay bow-tie UHF antenna. We thought it would be quite a popular project since more and
more viewers, even in the country, are now being serviced with UHF
television broadcasts. The bow-tie array we are publishing this month
has a number of desirable advantages over the more familiar long
Yagis used for UHF. First, it covers both UHF bands and it has better
discrimination against "aircraft flutter". With those thoughts in mind,
we were quite pleased to be going to press with this antenna as
featured in our article.
And that would probably have been the end of the story as far as
our January issue was concerned. However, just as we were going to
press, the Department of Transport and Communications issued stage
one of a timetable for television channel changes from the VHF to the
UHF bands. This is the long awaited announcement of the Department's plan to move television stations from the FM band, so that more
FM stations can go on the air. Most of the displaced TV stations will
have to move to the UHF (ultra high frequency) bands.
The timetable will mean far reaching changes for millions of people
around Australia. Whereas most people up till now have not felt a
pressing need to install a UHF antenna, even though some UHF services have been available, they will now have to do so. It will be mandatory, if they wish to continue watching the same programs.
Three television channels are in the FM band, 88 to 108MHz: channels 3, 4 and 5. As well, channel 5A will also be moved upwards. And a
number of translator services occupying channels elsewhere in the
VHF (very high frequency) bands will also move into the UHF bands to
make way for some of the stations moved from the FM bands.
In stage one of the timetable just released, 15 TV stations and three
translators will be moved from channels 3, 4, 5 and 5A. These moves
will be accomplished by late 1990. Stage 2, for channel changes after
1990, will be announced in the next few months. We'll publish full
details of the changes as they become available.
The changes have been decided upon after a long period of consultation with all parties in the TV broadcast industry. In the short term,
they will cause some disruption while viewers slowly make the
necessary adaptations. In the long run, we'll have a lot more FM stations which will be all to the good.
But sooner or later, many more people will be watching UHF TV
broadcasts. Which makes our UHF bow-tie array rather timely,
doesn't it?
Leo Simpson
MAILBAG
A winner
I have just read the first issue of
SILICON CHIP and you have an absolute winner. I cannot remember the
last time I picked up an electronics
magazine that had so much meaty
editorial and project content. It is
also pleasing to see that you have
assembled a great team of contributors. It has been a long time
since I actually looked forward to the
next issue of an electronics magazine.
Gary Johnston
Managing Director
Jaycar Pty Ltd
Congratulations
Our hearty congratulations on the
birth of your great new magazine.
The high standard of both features
and construction projects looks a winner. A few years ago the ranks electronics enthusiasts were decimated
by defections to the personal computer phenomenon. I'll bet 90 % of
them have now found personal computers pretty droll. SILICON CHIP
should be just the ticket to entice the
hackers back to the world's most interesting hobby - electronics.
Jack O'Donnell
Managing Director
Altronic Distributors Pty Ltd
Delighted with format
Congratulations on your exciting
new venture. As a long time enthusiast and previous subscriber to
another electronics magazine, I was
delighted with the format and content
of the first issue of SILICON CHIP and
wish you the best of luck for its
success.
It was a pleasure to see some simple, cheap yet extremely useful projects which other magazines have
been lacking in recent times (namely
the Capacitance Adaptor for DMMs
and the Off-hook Telephone Indicator, both of which I'll be
building). Hope you'll keep up the excellent standard.
George Mangos
Maroubra, NSW
Likes steam
As a regular peruser of newsagents' shelves for magazines of
various kinds, and a regular reader
of various Australian electronics
magazines, I was impressed with
your first issue. It contained a good
variety of articles, without the sanctimonious suggestion that everything
therein (steam engines, for instance}
was intrinsically tied up with "stateof-the-art" electronics. Congratulations.
T. Graetz
Walla Walla, NSW
SIUCON CHIP,
PO Box 139,
Collaroy Beach 2097.
Does not like steam
I have just purchased and read
your first copy of SILICON CHIP. On
the whole it appears to be a good attempt to breathe some life back into
the electronics magazine scene in
Australia.
My definition of an electronics
magazine is one which introduces the
reader, both beginner and experienced, to the technical aspects of electronics. These are to include explanations of new technologies, processes,
design techniques and construction
projects where possible to help reinforce the concept.
I am particularly interested in getting involved in amateur radio and I
hope that your section will provide a
good deal of information along with
projects.
Too often these days, it appears to
me, many magazines are overburdened with vaguely related topics.
Just because its got a processor does
not necessarily make it interesting.
Therefore, I cannot condone your
feature on electric railways or any
similar articles you may have planned. An article on the devolopment and
operation of electric motors would
have been more relevant.
How your particular publication
develops will be up to yourselves and
your contributors but I wish you all
the best of luck on your venture.
Hands up who has done that in the
last two years!
I have since debated this issue with
electricians who genuinely understand the problem (there are very few
who do} and they argue that two earths must provide better protection
than one. While this may be true, it is
also true that the consumer will be
unaware when one of the earth connections becomes faulty. This condition could exist for several years.
The real problem occurs when the
other connection becomes faulty or is
disconnected by a tradesman (electrican or plumber). That's when every
three-conductor appliance in the
premises will become live at 240V AC
above earth! Worse still, if the
neutral is faulty and a plumber
disconnects your incoming water
pipe, all your taps will be live in addition to your appliances.
How often is that likely to occur
you ask?
I firmly believe there have been at
least five deaths in Queensland alone
in the past several years that were
directly attributable to the above condition. Newspaper reports say the
deaths were due to an electrical
fault.
Your article suggested that consumers could buy "clamp-on meters"
and check their own installation. I do
not believe people will go to this trouble, technical or not. There is a safer
solution:
(1} Convert all premises back to the
"Direct Earth" system; and
(2) Earth all neutral wires at suitable
intervals at street power poles.
This will give the advantages of the
MEN system without the safety
hazards to consumers.
L. Iemi
Bentley, WA
M. McDonald
Wynnum, Qld
Safer solution to M.E.N. hazard
I was very interested in your article "Your House Wiring Could Kill
You" (November 1987). The MEN
system has concerned me for many
years, since introduction, due to the
reasons outlined in your article.
I wrote to a number of authorities
several years ago, stressing the inherent dangers of the system, to no
avail. The bottom line was: "It is the
consumer's responsibility to ensure
his electrical installation is maintained in a safe ·condition."
Jumper lead solution
I like your new magazine. It looks
good and the content is excellent.
Good also to see the Veroboard alternatives for projects. I don't usually
buy kits and have no enthusiasm for
making boards, hence usually have to
do the conversion myself.
I have two comments on your article entitled "Your House Wiring
Could Kill You". You say the wiring
can develop a dangerous fault. Actually the danger only arises when
continued on page 70
JANUARY 1988
3
PART 3 -
TIIE PROBLEM OF BR
'I'H E EVOLUTION OF
ELECTRIC RAILWAYS
While early railway development in
England and America is well
documented, much pioneering work was
also done in Europe, particularly in
Fronce, Germany and Sweden.
By BRYAN MAHER
Sweden did some impressive
development for they were in the
railway business quite early, having used horse-drawn mine
railways as early as 1798. The first
steam locomotive built in Sweden
was named the "Forstlingen" and
began service on a private line from
4
SILICON CHIP
Ore bro to Nora in March 1856. The
Government responded with the
opening of a line from Goteborg to
Jonsered and another from Malmo
to Lund, the first segments of their
future National Network, in
December of the same year.
Within six years the railway
crossed their country from ,/',
Stockholm to Goteborg and by 1892
they had in operation the world's
first International Train Ferry, connecting Helsingborg in Sweden with
Helsingor in Denmark.
In 1885 to 1902 they built the
fi~st railway within the ~retie
Circle, the Lapland Railway,
· ·
to transport iron ore from
Kiruna to Norway's ice-free
seaport Narvik. This railway was
electrified in 1915.
Extended to the Swedish port
Lulea on the Gulf of Bothnia in
1903, the whole 490-kilometre
length was fully electrified by 1922.
This world-first initiative in the
development of low frequency
alternating current traction
H· •·-·
At left, a view of Sweden's Lapland
Railway in mid-summer. This line
runs within the Arctic Circle but
◄ carries 38 trains per day in each
direction. (Bryan Maher photo).
systems initially used a 15kV 15Hz
supply generated specifically for
traction in low speed water-driven
alternators at the Porjus Power Station and transmitted via 80kV
single phase power lines. The
motors used are series commutator
motors.
The reason for the low frequency
supply is that on higher frequencies
like 50Hz the interpoles do not effectively cancel the armature
magnetic field reaction on the main
magnetic field, leading to severe arcing between commutators and
brushes.
The permanent summer snowline
in such northern climes is a mere
1000 metres above sea level. Since
about half the line's length is above
500 metres elevation, the track is
only free of snow during midsummer. Therefore, the electrical
designers decided to house all
trackside 80kV/15kV transformers
within large brick buildings for protection. But this plan came slightly
unstuck when the electrical
workers had the transformers temporally installed and working out in
the open while the bricklayers were
still at it.
As winter approached, all work
necessarily ceased but the
transformers and electrical gear
performed beautifully all winter,
even in blizzard conditions. The
cold air gave better cooling and
allowed the transformers some
overload rating so the engineers
decided to leave them where they
were.
Keeping in mind the low frequency used, transformer cores and
hence complete transformers are
considerably larger than similar
50Hz types so the now unwanted
brick buildings had been built to
generous proportions. But what use
could be made of them now? Even-
tually, these strong brick structures
were put to good use as the
roomiest passenger waiting rooms
on the system.
As well as being a lesson in international cooperation, as
locomotives of both countries
(Sweden and Denmark) share the
work, this line is unusual for
Europe as ore trains of 5500 tonnes
are commonly hauled by Dm class
4.8 megawatt (6400 horsepower) or
Dm3 class 7.2 megawatt (9400
horsepower) locomotives. Perhaps
you may find it difficult, gentle
reader, to picture such an Arctic installation as a busy thoroughfare
but in fact the average traffic is 38
trains per day in each direction six passenger and 32 ore trains.
More than 30 million tonnes of iron
ore are shifted to Narvik annually.
When other Swedish lines were
electrified, frequency converters
were used to derive 16.666Hz
single phase traction supply at
15kV from the three phase national
grid 50Hz system. This method
eventually replaced the 15Hz supply on the Lapland line also. By
1942 the world's longest electric
train journey was in Sweden, a
distance of 2022 kilometres.
Braking
In the 1830's it became quite apparent to the railway world that a
moving train is very hard to stop
and the early increases in
locomotive power and train weight
only increased the problem.
Originally in England, hand
operated brakes were fitted to each
wagon and a guard was appointed
to run along beside the train and set
each truck's brakes as the train
slowly rolled over the top of a hill.
You may find it hard to believe,
but this method of braking was still
use on a few privately owned
coal lines in the Newcastle
areas as late as the 1960s.
Increases in train speed
in the 1840s soon put this
method in the "too hard" category.
American railroads responded by
This two-axle electric locomotive was
made by Messrs Fowler & Co, of
Leeds, England at the turn of the
century. It was intended for use on
short lines. Electrical pickup was via
trolley wheel. (Norm Marks photo).
JANUARY 1988
5
turned a valve to allow some air into the "train line" and all truck
brake cylinders let go partially or
fully so the brakes were pulled on
by the brake-springs. The nice part
was that should a train coupling
break and the train become parted,
the hose couplings automatically
uncoupled, allowing air into the
lines of both parts of the train and
all were brought to a safe stop.
This method was used for years
in Britain but trouble came when
trains became heavier and faster
still. Other countries experienced
the same problems as they were
building lines up and down mountains. There is a limit to the pull
that can be exerted by a vacuum
cylinder as it can only have one atmosphere pressure or about 15 psi
acting on the piston. That limits the
useable strength of the brakespring and hence limits the braking
force that can be applied. Some
way of using higher pressures was
clearly needed.
Westinghouse air brakes
Built in 1901 by Messrs Siemens & Halske, of Berlin, Germany, this
experimental loco used 50Hz three-phase AC at 10,000 volts. On board
transformers stepped the voltage down to 750VAC. Just imagine the
complications of the overhead wiring at points. (Norm Marks photo).
fitting a walkway along the top of
the roof of every wagon. At the end
of each wagon's walkway was a
handwheel to apply the brakes.
Brakemen had to run the length
of the speeding train to apply the
brakes by turning each wagon's
handwheel. When some handwheels were found hard to turn,
each man was supplied with a
heavy wooden club to assist. Tales
of the Roaring West showed that
these brakemen's clubs were useful
in a brawl too!
With longer trains up to four
brakemen per train were employed,
two riding in the brakevan and two
riding on the engine. If two large
locomotives were used doubleheaded, a train crew could be considerable, with a driver and two
firemen to each loco , four
brakemen and a conductor, eleven
men in all.
Such a headcount can only
reflect the low wages and long
working hours of those days. Can
you appreciate their tough working
6
SILICON CHIP
conditions descending the mountains in a winter snowstorm?
To further assist in stopping
trains the caboose (guard's van)
was made large and heavy and
equipped with a powerful handbrake operated by the conductor
from within. Coal trains in the
Newcastle area up to the 1960s still
used the same idea.
Vacuum brakes
England, with more finesse, invented a vacuum operated brake
system with vacuum pipe, hoses
and hose couplings running the
length of the train. Brakes on each
wagon were pulled on by a spring
and simultaneously held off by
vacuum in a piston and cylinder.
The train driver set the steamdriven vacuum pump in operation
which evacuated the "train line"
(ie, the pipe, hoses and all brake
cylinders), pulling all truck and loco
brakes off. This was the running
condition.
To stop his train, a driver simply
That's where the Americans
came into the picture. Inventive
readers across the country can be
heard mumbling something like "So
what's the problem ? Why not just
apply compressed air to the piston,
any pressure you like to make it, instead of vacuum? Use 100 psi or
200 psi or whatever is necessary to
pull off a more powerful brakespring?"
Such an idea would give protection in case of a train coupling
breaking. Furthermore, a wagon
parked on a siding would perforce
have its brakes on, and a handwheel and gearing could be used to
pull the brakes off a parked truck
when we want to move it for
loading. The idea has in fact been
used for short trains; you could call
it a " straight air" system.
But the catch comes with a long
train, say a kilometre long with 100
wagons, each with its brake
cylinder full of air. That's a large
quantity of air to be moved a long
distance to the engine before the
brakes are applied, and-the brakes
would be firmly "on" in the front
wagons long before the air had
travelled from the back of the train
where the brakes are still "off"
This would result in a nasty
Pictured is a battery-operated loco used on the Lancashire and Yorkshire
Railway. The loco weighed 22 tonnes and was capable of pulling loads up to
120 tonnes. (Norm Marks photo).
"concertina" effect every time the
driver uses his brake control.
The Westinghouse organization
of the USA patented a system
wherein each wagon carries its
own high pressure air reservoir
and a 3-way air valve called the
"triple valve". Brakes are applied
by air pressure, not by spring,
when the triple valve opens a path
from the wagon's air reservoir to
the brake cylinder. Brakes are
released when the triple valve
opens a path from the brake
cylinder to atmosphere, letting the
air escape, and simultaneously
closing off the wagon ' s air
reservoir.
The lost air from the wagon's
reservoir must be replaced for the
next brake application. While
brakes are not being used the triple
valve opens a path from the train
air pipe to the wagon's air reser-
voir, allowing the air compressor on
the locomotive to refill all wagon
air reservoirs. This pumping-up
process usually takes some time but
that is acceptable if the system is
used intelligently.
"And just how?" you ask "does
that clever triple valve know when
it is supposed to change its function
as aforesaid?" Yes it is a clever little valve indeed. Its function is dictated by the difference in the
pressure between the wagon's
reservoir and the "train line". So
the loco driver controls the triple
valves and thereby the brakes by
letting air out of the train line or
allowing his compressor to pump
the line back up again.
The above story is a simplified
explanation but it does show that
full brakes can be applied by emptying to atmosphere only the air
contained in the train line pipe.
This is not a great quantity of air so
it can be done fairly quickly. And if
coupling breaks the train, full
brakes are automatically applied to
all train sections.
Furthermore the guard or conductor can apply emergency brakes
to the whole train, including the
locomotive, by opening a simple onoff valve mounted in his guard's
van or caboose emptying the air out
continued on page 74
Now being phased out, this is typical
of the heavy caboose or guards' van
used on American railroads.
(Conrail-J. Hill photo).
JA NUARY 1988
7
BUILD-IT-YOURS
SAVE$$$$!
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steel case
200W Power
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At last! The perfect opportunity to get yourself the perfect computer ...
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But you pay much, much less because you put it together yourselfl
disk controllers, ports, etc
No, there's no soldering or other difficult work required. All that's
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And it's guaranteed to be that simple: everything you buy is designed
to fit together ... holes line up, slots are in the right place, etc etc. No
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WHY BUILD YOUR OWN COMPUTER?
Apart from the reasons above (ie, you get what you want and you pay
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Nothing teaches you more about how something functions than constructing it yourself. It's the best way for anyone to gain an understanding of the fundamentals of computer operation - even if you've never
looked inside one before! Suddenly all those 'buzz words' you've often
wondered about will start taking on meaning ...
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Yes, just imagine. It must be one of the ultimate projects!
School & Tech students - think of how this will shape up as your
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Business People: now the computer you've always wanted at work can
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You don't have to outlay a large amount in one hit: this computer has
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4 clock speeds from
6 to 12MHz inbuilt
Keyboard lock
for security
BRIEF
Mother Board:
80286 CPU
6, 8, 10 & 12MHz speed (selectable)
Provision for 256K, 512K, 640K or
1024K RAM on board
CHIPSet technology & IC's
7 Channel OMA
16 Level Interrupt
Award BIOS (fully licensed)
Real time clock on board (battery b/u)
8 Input/Output Slots
(6 with 62 and 36 pin connector,
2 with 62 only)
CMOS Memory to Maintain System
Configuration
IBM PC/AT compatible
All LSI & RAM IC's fully socketed
80287 Co-processor socket provided
ELF'AT'
Buy what you want, as you want it ...
Baby AT' Motherboard:
Complete with 8 expansion slots, back-up battery, speaker,
manual and all lC's except RAM. Catx-1000
$799
Hinged Steel Case
Footprint just 430mm square, case covered In quality bone
crinkle finish. Pre-drilled, slotted, etc as required, complete
with front panel. Catx-1005
*175
200W Power Supply With enough capacity for full
expansion, complete with whisper quiet fan, on/off switch
and input/ output connectors. cat x-1010
*275
DISK CONTROLLERS:
Floppy Controller:- Up to 4 36OK or 1.2Mb drives.
CatX-2014
Hard/Floppy Controller: Handles 2 of each hard/flopoy.
CatX-2008
*129
*399
DISK DRIVES:
*269
*795
1.2Mb Floppy Disk Drive Complete with cables Cat x-2200
20Mb Hard Disk Complete with cables Cat x-2203
PLUG-IN CARDS:
*129
*149
*399
*139
CGA & Parallel Printer: Cat x-2010
MGA & Parallel Printer: catX-8141
EGA card with Hercules Compatabillty: cat x-2013
Serial/Parallel/Game Port Card: Cat x-2012
KEYBOARDS
1.2Mb Floppy and/or
20Mb Hard Disk
SPECIFICATIONS
Hard/Floppy Disk Controller:
Controls 1 or 2 hard disks
Ind. standard ST-506/ST-412 Interface
Up to 2048 cylinders
Up to 16 read/write heads
Data Transfer rate SMb/s
Controls 1 or 2 floppy disk drives
Interface similar to FD-SSF minifloppy
Double density 320/360Kb or 1601180kb
High density 1.2Mb
Rated to work up to 12MHz
Graphics Cards:
MGA, CGA & EGA available
Ports:
Keyboard port on motherboard
Parallel, serial & game ports on interface
Monitor port on appropriate graphics
card
84 Key 'IBM' Format Cat X-3820
101 Key Expanded Style: (direction keys and extra function
keys) Cat X-3821
MEMORY
Fast (120ns) top quality 41258 RAM chips. 9 required per
256K bank. CatZ-9313
(each):
Special price tor 18 or more:
(each):
*129
*149
*1095
•9•
5
EXCLUSIVE TO
l>CK0SMITH
EL
iCS
PTY LTD
DSEB465/RT1087
NEWS & VIEWS
Radio BDR in Darwin has begun
transmitting in AM stereo and is
the most recent of the ABC's
metropolitan stations to have this
facility.
We were interested to read the
following in a press release on the
event. "Because AM stereo is a recent innovation, only late model
Pictured above is the previewed Philips CD Video player, the CD475. It can
play 12cm, 20cm and 30cm video discs. Note the massive disc drawer.
Just when you thought things
were fairly quiet on the
technological front, Philips have
stirred the pot again. Late last year
Philips previewed CD Video - compact discs with video. They weren't
just video stills either, they were
the full bit - moving colour pictures, every bit as good as from the
current VHS HQ VCRs. And they
have the same high quality compact
disc sound.
"Alright," you are saying,"that's
pretty radical but I can accept it. So
what?" Well, CD video discs will
not just be on the familiar 12cm
discs we have become used to; they
will also be in 20 and 30cm versions
too. The 12cm version will contain
six minutes of video and music plus
another 20 minutes of music only.
And it can be played on any CD
player, video or not. It will be
known as the video "single".
The 20cm version of the disc will
contain about 40 minutes of music
and video while the 30cm version
will contain about two hours of
music and video. In a throwback to
the vinyl record days, they will be
known as "extended play" and
"long play" discs.
With the disc drawer closed, the CD475 looks very much like a normal CD
player. No release date has yet been set, nor is there any indication of price.
10
SILICON CHIP
Have you taken all that in? The
next bit is even more interesting.
Philips have developed a player
which plays all the CD video discs
described above, plus normal compact discs, plus all optical video
discs ever made. They demonstrated the machine, the Philips
CD675, with a video disc released
nine years ago!
This means the player can be used with interactive video discs.
Naturally, the machine has perfect
video stills and slow motion
replays. Boggle, boggle.
At the time of writing, no info
was available on the likely release
date to the market of the discs or
the players; nor was their any real
indication of prices. We expect that
release will probably be towards
the end of this year.
•
Philips and Sony, the codevelopers of the compact disc,
have agreed on specifications for a
CD Write-Once system intended for
professional use. The proposed
write-once recorder will permit
recording of data or audio information onto a blank write-once disc.
The information can then be played
back repeatedly, as for a normal
compact disc or CD-ROM.
Data storage capacity will be
essentially the same as for the existing CD-ROM; ie, a mind-blowing
600 megabytes.
Philips gives James
Bond the best
radio receivers are capable of
receiving and reproducing AM
stereo, however all AM radio sets
can still receive AM stereo broadcasts. Those sets without stereo
capability will simply reproduce
them in mono.
ABC listeners wanting stereo
sound reproduction should first
check that their radio sets have
built-in AM stereo capability."
We wonder if ABC listeners will
bother.
rA:nstra ·a
man11fact er
baml to-g:eth-ei
A group of Australian hifi
manufacturers have formed an
association to promote their products on local and overseas
markets. It sounds like a good idea
to us.
We hope they do a lot more than
the majority of foreign-owned companies at present in the market.
While some sectors of the hifi
market are doing quite well, others
are dying on their feet because of
the lack of any promotion.
There is just one drawback to
this promotional scheme; it will go
under the dreadful logo, Ozfi. Will
anyone take a product with an "Ozfi" label seriously?
Come one, come all. All amateur
radio operators, their families and
anyone interested in amteur radio
are invited to attend the 1988 Central Coast Radio Club Field Day to
be held on Sunday, 21st February
at the Gosford Showground.
If you're interested, put the date
down in your diary. If you are a
potential trade exhibitor, contact
the Central Coast Amateur Radio
Club, PO Box 238, Gosford, NSW
2250.
Advertising has leapt to i:iew
heights with the release of the
latest James Bond film, "The Living Daylights". This is loaded
with the usual improbable plot,
improbable dialogue and improbable escapes and is a lot of
fun.
The most unusual feature for
us was the exposure of Philips
products. This wasn't glaringly
obvious you understand, and you
could easily miss it if you weren't
aware but we noted at least 12
instances where the Philips
brand name or Philips products
were featured. Some of the tasks
to which Philips products were
put to were a little unusual to say
the least.
As far as we know though,
James Bond's special keyring
which is loaded with a number of
techno-gimmicks, is not a standard Philips product. We doubt
whether it would be approved
for general sale.
Radio service for
Japanese tourists
In case you didn't believe it,
Australian companies are working harder to cater to tourists,
particularly those from Japan.
Commencing next month, there
will be a special radio service
aimed at Japanese tourists.
Known as Travrad (Travellers'
Radio), the service will be broadcast in Adelaide, Alice Springs,
Brisbane, Cairns, Canberra, Darwin, Gold Coast, Melbourne,
Perth and Sydney.
Broadcasts will be narrowband FM on about 151MHz from
6am to 10pm every day. The
broadcasts will be picked up on
fixed receivers in motels and
hotels and on portables which
will be available for hire at
hotels and other tourist
destinations.
The service will be operated
by a new company, Fidelity Communications Corporation Ltd.
It will be a Japanese language
service carrying news and info
about tourist activities,
Australian history, customs and
lifestyle, music and human interest material.
Better throw another shrimp
on the barbie, eh?
Cordless phone
import ban
The Department of Transport
and Communications has moved
to prevent overseas travellers
from bringing back cordless
telephones into Australia.
In a recent announcement, the
Minister for Land Transport and
Infrastructure, Mr Peter Duncan, said that all cordless phones
brought into Australia are being
impounded and must be tested
before release, by the Department of Transport and Communications, by Telecom and by
one of the Electricity Authorities.
He noted that fees for this type of
testing may exceed $1000 and
there is no guarantee that any
equipment will be approved for
use.
Better knock that item off your
overseas shopping list. Approved
cordless phones will continue to
be on sale in Australia.
Four-wheeled boats!
Now that OTC's automatic
Seaphone service with direct
dialling ship-to-shore has been
introduced (see story this issue),
how many cars are likely to be
fitted with marine radios? That's
a question the pundits are asking
themselves as they compare the
pros and cons of Telecom's
cellular radio with Seaphone.
With the much lower initial cost
of Seaphone, it is probable that
quite a -few will be fitted to cars.
It seems that OTC's base
radios do not ask the position of
boats when they call in so they
have no way of knowing whether
the radio is fitted to a boat or
car. There has been at least one
instance of a Seaphone call for
road service.
JANUARY 1988
11
FOR A NUMBER of years now Sony has had a reputation
for very fine tuners and this year they won out with their
model ST-S444ESX. Its outstanding specification includes
an ultimate signal-to-noise ratio of 96dB in mono and
91db in stereo. RRP is $893.
WINNER IN THE Technological
Development category, the Bose
Acoustimass system uses the very
small stereo satellite speakers
pictured above, which are only 19cm
high and have magnetically shielded
drivers, allowing them to placed near
video monitors. The Acoustimass
woofer module, pictured below, can
be positioned anywhere in the room.
'IHE 1987
IIlFI AWARDS
- TIIE WINNERS From a limited field of runners, this year's
CESA Grand Prix hifi awards produced some
interesting winners. Consistent performers like
Marantz and Sony were there again, as was
Yamaha, while Bose chalked up its first award.
BEST AMPLIFIBR
this year was the
Marantz PM-64Il
which has
comprehensive input
control facilities,
including video
inputs and CD-direct,
which bypasses the
tone controls and
other preamp
circuitry. Power
output is 100 watts
RMS per channel
and up to 300 watts
(IlIF music power)
into 2-ohm loads.
RRP is $1099.00.
12
SILICON CHIP
YAMAHA HAS been one of the few Japanese
loudspeaker manufacturers to really gain a
reputation for its loudspeakers. This is not the
first time it has won the CESA award for best
loudspeaker. This very fine 3-way system, the
NS-10000, uses carbon fibre technology in the
woofer and beryllium for the tweeter and
midrange domes. RRP is $13,000.00.
By LEO SIMPSON
The CESA Grand Prix hifi
awards have been having a
rough trot since their inception
three years ago and each year
has been marked by less entries
as more hifi distributors retire
from the field to lick their
wounds and comtemplate an
ever toughening market.
A surpise, but no surprise
really, was that there were no
entries at all in the turntable
category. The Japanese have virtually abandoned the field
altogether to chase after the
burgeoning compact disc market.
This, while millions of people
around the world still have
billions of records they wish to
play.
Winner in the amplifier
category was the Marantz
PM-641( making it two consecutive wins for this company.
The PM-64II is a keenly priced
model with plenty of power and
facilities. Runner up was the
powerful Perreaux PM2350 with
200 watts per channel.
No award was made in the
receiver category, since it was
only a two-horse race. Similarly,
the judges decided not to make
an award in the cassette deck
category - it was a field of plodders but the racers of the day
hadn't been entered.
In spite of the large number of
CD players on the market, there
were only five entries in this
category, from Marantz, JVC,
Yamaha, Sharp and Sony. Sony
was the winner, with their highly
rated model CDP-555ESD.
Sony also won the tuner
category, with their ST-S444ESX
model which has very high performance in its FM section.
The other two awards, for best
loudspeaker and for technological development, were interesting because the respective
winners were originally not
entered in their ultimate award
category. The Bose Acoustimass,
a sa telli te-cum-superwoof er
system was entered in the
loudspeaker category but won
the award for technological
development.
And the Yamaha NSl0000,
which was entered in the
category for technological
development, won the prize for
best loudspeaker.
Let's hope there are a lot more
horses running next time.
SONY'S top-of-the-line
CDP-555ESD CD player
has every feature you
could think of, including
remote volume control. It
can also be teamed with
an optional linear D-A
converter, the
DAS-702ES, for even
higher performance. RRP
of the player on its own
is $2299.00.
JANUARY 1988
13
14
SILICON CHIP
By LEO SIMPSON
& BOB FLYNN
If you can do basic metalwork
you can build this antenna. Your
bill of materials will be around $25
and the finished antenna should
give better performance than commercial UHF Yagi antennas costing
up to a hundred dollars and more.
In Australia, on the UHF (ultra
high frequency) TV bands, the Yagi
antenna is king. UHF Yagis are now
very familiar on Australian rooftops. They have a long boom, up to
1.8 metres or more, with many
short elements arranged along it.
The Yagi design for UHF has
many advantages. It is easy to mass
produce, uses a modest amount of
material, has relatively low windage (ie, force due to wind acting on
it), good directional characteristics
and good gain, depending on the
number of elements.
The Yagi does have a number of
drawbacks though. It must be made
with considerable precision if it is
to perform well, so it is not so easy
for the enthusiast with basic
metalworking facilities to build. It
is also a no-compromise design in
that it is not practical to design a
Yagi which will cover both UHF
bands, particularly if you want a
modicum of gain. You can have
band IV or band V but not both.
In Australia, by the way, UHF
band IV covers channels 28 to 35,
526 to 582 Megahertz. UHF band V
covers channels 39 to 69, 603 to
820MHz. Each channel occupies a
7MHz slot.
In Europe and other parts of the
world, there are common alternatives to the Yagi design. One is a
Yagi with a corner reflector,
another is a bow-tie with corner
reflector, while a third is the most
common, the bow-tie array. This is
essentially a dipole (shaped like a
bow tie) with a plane reflector close
behind it. Higher gain is obtained
..
..
..
:(l
1
REFLECTOR ELEMENTS
6mm x 1mm WALL THICKNESS ALUMINIUM TUBING 600mm LONG 17 REQUIRED
Fig.1: front and side elevation of the new UHF antenna. This diagram labels
all the special hardware items that you have to make except for the reflector
elements. Below is a close-up view of two of the dipole bays.
Thinking about building an antenna to pick up UHF TV
in your area? This four-bay bow-tie array has high gain and
covers UHF bands IV and V without modifications.
JANUARY 1988
15
THIS ROW OF HOLES
ALL 6mm DIA.
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+
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BILL OF MATERIALS
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....
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FRONT
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I
SIDE
FRONT VERTICAL BOOM
19mm SQUARE x 1.6mm WALL THICKNESS
ALUMINIUM TUBING
BACK
SIDE
REAR VERTICAL BOOM
19mm SQUARE x 1.6mm WALL THICKNESS
ALUMINIUM TUBING
Fig.2: cut and drill the front and rear booms exactly as shown here.
16
SILICON CHIP
by stacking bow ties, in either twobay or four-bay arrays. The latter is
the design we are presenting.
The four-bay bow-tie array
antenna has a number of advantages over typical Yagis. First, it
can cover both bands IV and V
without modification. Second, it has
better gain than all except the
highest gain Yagis which may
measure up to three metres long.
Third, it has good front-to-back
ratio and a much narrower acceptance angle, in both the vertical and
horizontal planes .
(Note: the 18-element TC-18 from
Hills is a combination of a long Yagi
with a small corner reflector. The
corner reflector gives it slightly
higher gain and a narrower acceptance angle. For those who do not
wish to build their own antenna, it
Antenna
1 .6 metres of 1 9mm square
aluminium tubing with 1.6mm
wall thickness
13.8 metres of 6mm aluminium
tubing, 1 mm wall thickness
1 .4 metres of 3mm dia. solid
aluminium rod
270mm x 130mm x 1.6mm
aluminium sheet
4 1 0mm x 50mm x 3mm thick
Perspex
50 pop rivets (3mm x 6mm ,
aluminium mandrel); or
50 stainless steel self-tapping
screws (see text)
2 U-bolts and clamps to suit
mast
16 stainless steel screws,
3mm dia. x 16mm long, nuts
and shakeproof washers
Balun Box
1 80mm x 52mm x 30mm
plastic box
1 printed circuit board,
SC2-1-0188
3 6BA x 12mm screws with
nuts
2 6mm spacers
3 stainless steel self-tapping
screws, 1 5mm long
Miscellaneous
7 50 semi-air spaced coax cable
(Hills SSC32 or equivalent),
plastic cable ties, silicon sealant,
Delrin plugs (for square tubing)
is a good choice in fringe areas. It is
available in Band IV and Band V
versions).
The narrow acceptance angle of
a four-bay bow-tie array is important, particularly if your location
does not have a good line-of-sight to
the transmitter and if you are often
over-flown by aeroplanes. This
combination of circumstances can
lead to a phenomenon known as
"aircraft flutter".
When this occurs, the signal
reflected from the aircraft to your
antenna can be stronger than the
more direct signal received from
the transmitter. This causes very
strong ghosting on the screen and a
slowly fluctuating vertical bar on
the screen which is the ghost of the
horizontal sync pulse.
The picture flutters because the
plane is moving at high velocity
relative to your antenna and so the
path of the strong reflected signal is
changing rapidly.
In severe cases. aircraft flutter
can cause the picture to lose
horizontal synchronisation.
Where the bow-tie array has a
considerable advantage over the
Yagi is that it has a much narrower
vertical (and horizontal) acceptance. This is about half that for a
Yagi of equivalent gain; ie. about
27° versus about 40°. This means
that the bow-tie array will pick up
much less reflected signal from
high flying aeroplanes and
therefore interference is much less.
Well, what about the disadvantages of the bow-tie array versus
the Yagi. Yes, it does have some.
First, because it is a vertical rather
than horizontal array, it has considerably more windage. Ser:;ond,
there is probably more work in
fabricating a do-it-yourself design
such as this.
While we did not have equipment
for measuring the absolute performance of the bow-tie array
featured here, we were able to
make a lot of direct comparisons
with commercial UHF band IV and
band V Yagi designs. These were
essential to optimise the performance for both band IV and band
V.
After a lot of trial and error, we
are pleased to present a design
which is very competitive with pre-
The front and rear booms are fastened together using four tie plates (see
Fig.6). Bend the cross-coupled harness connectors slightly so that they do not
touch each other.
sent commercially available Yagis
and as noted above, it is notably
less susceptible to "aircraft
flutter".
Design features
Our bow-tie array is similar in
appearance to a number of corn-
mercial designs which are
available overseas. It is constructed mainly of 6mm aluminium
tubing with the two vertical structural members (booms) being 19mm
square tubing. The four dipoles are
effectively vestigial bow-ties, being
Vees made of tubing rather than
JANUARY 1988
17
tapping screws. These are strong,
readily available and corrosion
resistant.
We do not recommend galvanised, bright zinc or cadmium plated
steel screws as these do not stand
the test of time. Often they will
start to rust within a few days' exposure in seaside areas. They may
be OK for roofing work but in combination with aluminium they rust.
If you live away from the sea and
decide to use these types of screw
anyway, we recommend that you
paint the antenna. We'll talk about
that later.
Don't, on any account, use brass
or mild steel screws. If you use
these, you will spoil the job.
207
Fig.3: the 16 dipole elements are all made from 6mm aluminium
tubing. Cut the dipoles to a length of 207mm.
Q
"'
18
26
26
18
100
Fig.4: either 3mm thick Perspex or
clear Lexan can be used for the
dipole carriers (four required).
Making your antenna
DIPOLE MOUNTING CLll'S
1.6mm ALUMINIUM 8 REQUIRED
+
+
Fig.5: the eight dipole clips
are cut out using tin snips
and then bent up in a vice.
◄
87
triangular pieces. This cuts down
on the windage while keeping the
bandwidth essentially the same.
The reflector is essentially a
large grille about 60cm wide and
80cm high. The four dipoles are
mounted on a common vertical
boom which is spaced away from
the vertical boom of the grille by
about 50mm.
The antenna is shown in front
and side elevation in Fig.1. This
diagram labels each special hardware item you will have to make.
These are: (A) the dipole carriers, four required; (B) the dipole
mounting clips, eight required; [C)
the main mounting plate; (D) balun
box assembly; (E) dipole elements,
16 required; (F) the boom tie plates,
four required; (G) front boom; [H)
rear boom; (J) o'!lter harness connectors, four required and [K) inner
harness connectors, four required.
Also shown on Fig.1 but not
18
SILICON CmP
Fig.6: cut and drill the four
aluminium tie plates as
shown here. These tie the
front and rear booms
together.
labelled as such, are the reflector
elements, of which 17 are required.
Fasteners
After a few years' exposure to
the elements, many antennas are in
a poor state. Because aluminium is
such an active metal, the right
fasteners must be used otherwise
corrosion will be very rapid,
especially in seaside areas.
We recommend three types of
fastener for this project: (1)
Aluminium pop rivets with
aluminium mandrels. Those with
steel mandrels are not recommended. Eventually, their mandrels will
rust and while this may not harm
the antenna it will cause unsightly
discolouration. (2) Though often
hard to get, aluminium screws are
recommended although they are not
available in self-tapping types and
so all screw holes would have to be
tapped. (3) Stainless steel self-
Most enthusiasts will have the
tools needed for this project. You
will need a hacksaw, electric drill,
vice, pop-rivet gun, blow-torch or
LPG cylinder and torch. Apart from
a pair of antenna clamps [U-bolts ),
no special hardware or fittings are
needed as we will detail how every
part is made.
Making and assembling this
antenna is a fairly straightforward
process although some steps are a
little tedious. You must first obtain
all the aluminium and hardware
listed in the Bill of Materials, and
make sure you have access to all
the tools we have listed above.
Having assembled together all
the raw materials, you can start
work by cutting all the aluminium
elements with a hacksaw.
Cut the two booms first, which
are made of 19mm square
aluminium tubing. The details are
shown in Fig.2. The rear boom is
812mm, while the front boom is
720mm long. Then centre-punch
and drill all the holes in both booms.
Make sure that all the holes for
the reflector elements in the rear
boom are precisely in line and that
their centres are 4.6mm from the
front surface as specified on the
diagram of Fig.2.
Do not forget the holes for the tie
plates or the holes in the back of the
rear boom, for the main mounting
plate. Trying to drill these after the
antenna has been partially popriveted together would be a tricky
task.
The mounting plate is rivetted to the
back of the rear boom and carries
two U-bolts to mount the antenna to
the mast.
Next, cut all 17 reflector
elements and the 16 dipole
elements. These are made from
6mm aluminium tubing with a 1mm
wall thickness. The dipole element
dimensions are shown in Fig.3
while the reflector lengths, all
600mm, are shown in Fig.1.
Assemble each reflector element
into the rear boom, one at a time.
The method we used was to thread
one element through the boom, centre it precisely and centre-punch on
the front of the boom, at the intersection of the centre-lines of the
boom and the reflector element.
Drill a 3mm (or 1/8-inch) hole
through the front of the boom and
element and then pop rivet the two
together. Do this for all 17 reflector
elements.
Dipole plate & clips
Next, make the four dipole
plates, as shown in Fig.4. We used
3mm thick white Perspex but you
can use clear Lexan or Perspex as
they stand the weather equally
well. When drilling, do not use too
high a speed otherwise the Perspex
will tend to melt and congeal on the
drill.
Now, make the eight dipole clips.
We cut and bent these from a strip
of 1.6mm thick aluminium, 38mm
wide. Fig.5 shows the details. Each
clip can be cut with tin snips, flattened with a hammer and then each
side bent up in a vice.
That done, you can make up the
four dipole assemblies, each requiring a Perspex dipole plate, two
dipole clips, four dipole elements
plus four stainless steel 3mm
screws, nuts and lockwashers.
Next, make the four tie plates
which tie the front and rear booms
together. You can also make the
main mounting plate at this stage,
since it uses the same material,
1.6mm thick aluminium sheet. The
details are shown in Fig.6 and
Fig.7.
Now assemble the front and rear
booms together. using the four tie
plates. You can use pop rivets or
stainless steel self-tapping screws
for this job.
Fix the main mounting plate to
the rear boom, using pop rivets or
stainless steel self-tappers.
Mount the four dipole assemblies
onto the front boom. Use pop rivets
or stainless steel self-tappers.
Your antenna now looks the part
and only lacks the harness and
balun box assembly.
JANUARY 1988
19
Make the inner and outer
harness connectors, as shown in
Fig.8. These are made from 3mm
diameter aluminium rod. This is the
trickiest stage in the whole process.
After cutting to length, the ends
of each connector must be hammered flat. To do this satisfactorily,
you will have to anneal each end
with a blow torch (or LPG torch).
Unfortunately, there is no easy way
of judging how much heat to apply
but if you overheat the end it will
suddenly melt and fall on the floor.
The way to do it is to place each
end in the flame for a few seconds
and then hammer it flat. If
necessary, reheat the end to finish
the job. In fact, aim to do the flattening in two steps of hammering
and annealing otherwise you will
inevitably melt it.
That done, centre-punch each
end and drill 3mm holes. The eight
connectors are then ready to be attached to the four dipoles but
before you can do that you need to
prepare the balun box assembly.
Incidentally, note that when the
ends of the harness connectors are
hammered flat, they spread and
stretch quite a bit. This accounts
for the fact that the outer connectors are cut to 200mm long but
when the ends are hammered flat,
the hole centres for the connector
screws can be drilled 199mm apart.
Balun box assembly
The balun box provides a correct
termination for the antenna
harness and terminals for 75-ohm
coax cable, all sealed away from
the elements for protection. It takes
the form of a black plastic box with
a small printed circuit board inside.
This mounts the air-cored balun
and the terminations.
The printed circuit measures 30
x 70mm (code SCZ-1-0188) and has
a very simple pattern. The balun is
made of two small coils of enamelled copper wire, as shown in Fig.9
and Fig.10. Use wire with selffluxing enamel for this job. Selffluxing enamel melts easily in a
solder pot or with a soldering iron
and is much easier to work with
than high temperature wire
enamels which must be thoroughly
scraped off before the wire can be
tinned with solder .
.20
SILICON CHIP
~
~
•
4
-I--.
•
.,
I
♦
•
~
-$
15
35
0
•
15
35
116
Fig.7: drill the mounting plate to suit the Ubolts and clamps used.
CE==========================~
199
OUTER CONNECTORS
3mm DIA SOLIO ALUMINIUM 4 REQUIRED CUT PIECES 200mm LONG,
ANNEAL ENDS ANO HAMMER FLAT
I
75
I
{ ~
130
INNER CONNECTORS
3mm DIA SOLID ALUMINIUM 4 REQUIRED CUT PIECES 132mm LONG,
ANNEAL ENDS AND HAMMER FLAT
BEND AS SHOWN BEFORE MARKING HOLE POSITIONS
Fig.8: dimensions for the inner and outer harness connectors. Use a
blow torch to anneal the ends before hammering them flat.
Incidentally, do not think that the
connection of the outer coil of the
balun is a mistake, as shown in
Fig.10. It is correct, with both ends
soldered to earth.
The balun printed circuit board
and its accompanying box is tricky
to mount. We suggest the following
method. First, attach the four
harness inner connectors to the
printed board using stainless steel
screws and nuts. The aluminium
conductors must not make physical
contact with the copper side of the
board.
You can use brass or copper
plated steel for the coax cable
clamp. We suggest you solder brass
nuts to the copper side of the board
to secure the cable clamp and the
screw to terminate the inner conductor of the coax cable.
Fig.11 shows the details of the
balun box and how it is mounted.
Use one self-tapping screw to
secure the box to the front vertical
boom. Use two spacers and two self
tapping screws to secure the
printed board to the case bottom.
The latter two screws should
penetrate the boom.
Now attach all eight harness connectors to the dipole assemblies
and the antenna is virtually finished. Do not over-tighten the dipole
assembly screws otherwise the
Perspex will distort and possibly
crack.
You will need a pair of antenna
clamps or U-bolts to mount the
antenna to the mast or J-pole (for
barge-board mounting). We prefer
the use of galvanised U-bolts and Vclamps for this job rather than the
cadmium-plated and passivated
types used for most antenna hardware. The latter have a gold finish
and often start to rust prematurely.
U-bolts and clamps for
automotive exhaust systems are
0
300{)
ANTENNA
__
7~{l
T
_,.
~
BALUN TRANSFORMER
PRIMARY 12T, 0.67mm ENAMELLED COPPER WIRE
CLOSE-WOUND ON A 3.2mm DIA. MANDREL
SECONDARY SLIPPED OVER END OF PRIMARY
AND BOTH ENDS SOLDERED TD EARTH
BALUN COILS MOUNTED ON COPPER SIDE OF BOARD
SECONDARY 6T, 0.67mm ENAMELLED COPPER WIRE
CLOSE-WOUND ON A 4. 76mm DIA. MANDREL
Fig.9: winding and termination
details for the air-cored balun.
Fig.10: the balun coils are mounted on the
copper side of the PCB. Note that both ends of
the secondary are soldered to earth.
tThe completed balun board. Brass nut-s are soldered to
the copper pattern to secure the screws for the cable
clamp, coax cable inner conductor, and harness
connectors.
generally quite suitable and have
good corrosion resistance. Or, if
you want to be really fancy, go to a
ship's chandlers and buy stainless
steel U-bolts and clamps. They're
costly but good.
We suggest that the ends of all
the reflector and dipole elements be
stopped up with silicone sealant.
This will stop them from whistling
in the wind. You can do the same
with the booms although, for a
neater result, you can buy square
Delrin plugs.
Installing the antenna
Take a lot of care when installing
your antenna. There's no point doing a fine job of assembly and saving all that money if you end up in
hospital because you fell off the ladder. Climbing ladders with anten-
0
PLASTIC BOX
BOX CENTRE
LINE
00
00
,-
II
-l-
1
N
0
0
(J
en
This is the actual size pattern for the balun board.
nas is dangerous work.
The first step in installation is to
decide where to mount your antenna. For best results mount it as high
as possible and well clear of other
antennas.
It is not really practical to mount
this bow-tie array on the same mast
as a VHF antenna unless it is vertically separated by at least one
metre.
Having mounted your mast, take
the antenna up and secure it with
the U-bolts. Then terminate the
coax cable. For minimum signal attenuation and good cable life, we
recommend Hills semi-airspaced
cable, type SSC32 or equivalent.
At your TV set end of the cable,
you will probably need a diplexer to
continued on page 95
View inside the balun box assembly.
It should be sealed against the weather.
WIRING HARNESS
(BENO HARNESS TO CLEAR
'--..._ ~ - - - - - + - - - - - - / " - - , , C A B L E CLAMP)
'
FRONT BOOM
0
1
,-
I
COAX
6.6mm DIA. HOLE FOR COAX
IN ONE ENO DNL Y
Fig.11: details of the balun
box assembly. It is
secured to the front boom
at one end using a selftapping screw and at the
other end by two selftapping screws which pass
through the PCB and 6mm
spacers.
JANUARY 1988
21
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.
Sequential lamp
flasher for your car
S1
0--0"""",
FLASHER
TIMER 2
TIMER 1
+ 12 V
LAMP 1
10k
For those people who are tired of
having a single pair of lamps at the
rear of their car to indiciate righthand or left-hand turns, this circuit
will make your vehicle different indeed. It allows three lamps to be
flashed in sequence. Lamp 1 lights
first, then lamp 2 and then lamp 3.
Then all the lamps extinguish and
the sequence begins again, at the
rate set by the car's existing
flasher module.
You could add the extra lamps to
the rear parcel shelf or mount them
externally. Either way would give
you much more visible turn signals.
The circuit begins to operate
with switch S1 closing. This lights
lamp 1 immediately and capacitor
Cl begins to charge towards the
positive rail. When the anode
voltage of Ql exceeds the gate
voltage by 0.5V, Ql switches on and
,.
A
A(:f}
SCR1
C106Y
G
~~.
C1
0.47
16VW
KAG
SCR2
C106Y
G
+
_
0.47
16VW
.,.
.,.
triggers SCR1. This lights lamp 2
and powers the second timing circuit. This operates in a similar manner to the first timing circuit and
lights lamp 3.
When the flasher module opens,
all lamps are extinguished and the
sequence recommences when the
flasher module closes the circuit
again.
Since each SCR drives only one
lamp, usually 21 watts or
+
thereabouts, no heatsinking will be
required. The time period can be
adjusted by changing the value of
the 0.47 µF capacitors.
Note: this circuit will not work
with those flasher modules which
place residual voltage across the
lamp filaments during the "off"
periods. This residual voltage will
result in the SCRs failing to turn off
and the lamps would cycle once and
then flash simultaneously.
High impedance op amp with input protection
The circuit presented here was
designed to provide a high impedance input, namely 1MO in
parallel with ZOpF, input protection to at least ± 100V and bandwidth limiting to about 2MHz. The
first approach is shown in (a). This
shows an LF351 op amp in
voltage-follower mode (output connected to inverting input) and with
input clamping diodes connected
to ± 10V rails.
The problem with the diodes
specified is that they are too
leaky. This would not normally be
a problem but the gain of the
following stage (not shown) is 80.
The effect of connecting a low impedance source to the input
amplifier was a shift in its output
by 250mV. When multiplied by the
following stage's gain, this would
be enough to overload it.
22
SILICON CHIP
+10V
OUTPUT
(a)
-10V
One solution is to use low
leakage diodes such as BAV45s
but these cost more than the
LF351. Another alternative is to
use the gate-source junction of a JFET. Many of these devices exhibit the right characteristics (not
switching types) but have a maximum current of only 10mA. The
base-collector junction of many ordinary bipolar transistors, such as
2N3638A, is fine, with leakage
currents in the picoamp region.
I . used PN3653s because they
also exhibit quite low junction
capacitance. That then raised the
concern that the variation of the
input voltage might vary the
capacitance of the base-collector
junction and hence vary the bandwidth with input voltage.
An elegant solution is presented
Crowbar over-voltage
protection for power
supplies
2A
v+-<r-...o-----SCRl
C122D
Most logic circuitry can be
damaged if the supply voltage goes
too high, even for brief periods. For
this reason most power supplies for
computer and logic applications
have fairly complex circuits to
assure good regulation. When this
circuitry fails though, the usually
well-regulated output goes much
higher and following circuitry is
usually damaged.
To avoid this, crowbar circPitry
is often added, to provide drastic
protection in the last resort. In the
event of the supply rail going high, a
dead ·short circuit is placed across
+
10
(a)
it. This blows a fuse and renders it
safe.
Three crowbar protection circuits are presented. (a) is a simple
circuit involving just a zener diode
to sense the voltage and an SCR
(silicon controlled rectifier) to provide the short circuit and blow the
fuse. When the supply voltage rises
slightly above the zener voltage,
current is fed via the zener into the
gate of the SCR to trigger it. The
fuse blows within one microsecond
which is fast enough to protect
semiconductor circuitry.
The problem with this circuit is
that it is too dependent on the particular zener characteristic and on
the trigger current of the SCR.
(b) is a better circuit. Ql acts as a
comparator, comparing a preset
voltage at its base with the zener
voltage at its emitter. Because of
the gain of Ql, the circuit has a
much more precise trigger point
and it has the advantage of being
adjustable with VRl.
(c) is better still. The diode in
series with the zener provides
V+--o-2-AD-_.,__ _ _ _ _ _ _ _ _ _ __
SCRl
C1220
2.2k
10
(c)
(b)
temperature compensation of the
reference voltage. The circuit has
higher gain and the differential
amplifier acts as a more precise
comparator.
+lOV
D1
1N914
Substituting electros
2x1N914
D3
D4
OUTPUT
3.9k
INPUT
10pf+
1M
.,.
(b)
D2
1N914
-10V
in (b). This shows the 1N914s
strung across the input of the op
amp and with further clamp
diodes connected to the output.
The ± 10V rails must then be able
to handle the full current of the op
amp when it is over-driven.
This configuration eliminates
the leakage problems of the
1N914s because they have virtually no voltage across them until the
input is overloaded. At other times
the input diodes are effectively
bootstrapped out of circuit by the
op amp's output.
$20 to: Phil Denniss,
University of Sydney.
Where an electrolytic capacitor
is specified in a circuit, you can
always substitute a capacitor with
a higher voltage rating, provided
that the size of the capacitor is not
a problem. You can often also
substitute a capacitor with a lower
voltage rating, provided the voltage
across the capacitor is not likely to
be exceeded.
Circuit designers often standardise on capacitors with only two
voltage ratings, say 16V or 25V. In
many cases though, a capacitor
rated for 25V may have much lower
voltage impressed across it which
gives the opportunity for
substitution.
JANUARY
1988
23
Update the sound
Our phone ringer has been
designed to go on a small printed
circuit board which can be installed in just about any phone although
we expect that most will be installed in older phones with electromechanical bells.
Only six components are used in
the circuit, five of them mounted on
the printed circuit board (PCB). The
exception is the piezoelectric
transducer which actually produces the chime sound.
How it works
Are you tired of the sound of your
telephone bells? You can change to a
modern sounding chime by building this
simple module.
Apart from wishing for a change
in the sound of your old telephone
bells, there is another good reason
for building this personal phone
ringer. If you work in a large office
with many telephone extensions, it
can be very difficult to tell whether
it is your phone that is ringing or
not.
With this little circuit wired in
place of the existing bell or solid
state chime, you can set the tone of
your phone so that it is distinctly
different from all the other phones.
That way, if you are away from
your desk, you won't be wondering
if it is a call for you every time a
phone starts to ring.
Another reason for using this
ringer circuit instead of your
phone's existing bells may be if you
or someone in your household is
partially deaf. You may not want to
go to the trouble and expense of
having an extension bell installed if
this ringer can do the job.
+
C2I
OV0UT
BRIDGE
RECTIFIER AND
28V CLAMP
THRESHOLD
CIRCUIT WITH
HY S!~R~~IS t---"""
8
12.6V
OUTPUT
FREQUENCY
CONTROL
RT
PSB6520 TONE RINGER IC
.,.
Fig.1: block diagram of the PSB6520. Rt sets the oscillator frequency while Cs
sets the rate at which the oscillator is modulated.
24
SILICON CHIP
.,.
The heart of the phone ringer is a
Siemens PSB6520 tone ringer integrated circuit (IC) which is
specifically designed for use as an
electronic bell in a telephone set.
The functions of the PSB6520 IC
are shown in Fig.1. When a ring
signal tone is sent down the
telephone line, the voltage is coupled via capacitor Cl while the current is limited with series resistor
Rl. An internal bridge rectifier converts the AC ring tone to a DC
voltage which is clamped to a maximum of 28V. C2 at pin 7 is a filter
capacitor to provide a smoothed DC
voltage.
When the DC voltage derived
from the ring signal reaches about
18V the oscillator circuit begins to
operate with switch Sl closing to
the upper position. If the DC voltage
falls below 8.4V, Sl will reclose to
the lower position and the oscillator
will cease operation.
Resistor Rt at pin 4 sets the frequency of the oscillator while
capacitor Cs sets the rate at which
the ocillator is modulated to produce its pleasant burble tone.
Naturally, the tone is audible only
while the ring voltage is present, so
instead of going ring ring your
phone will now go chirple chirple.
Fig.2 shows the final circuit. As
can be seen, we have not included
capacitor Cl in the circuit, since all
telephones will already have a
of your phone
Design by
JOHN CLARKE
PARTS LIST
PCB, code SC121 -1287 , 28
x 36mm
PSB6520 tone ringer IC
(Siemens)
piezo transducer (Jaycar Cat.
AB-3440 or equivalent)
1OµF 63VW PC electrolytic
capacitor
1 0. 1µF metallised polyester
capacitor
1 22k0 miniature vertical
trimpot
2.2k0 0.25W resistor
Miscellaneous
Solder , hook-up wire .
We installed the prototype in this phone by glueing it to one of the flat metal
pillars which support the dial mechanism (bottom left).
capacitor for the existing bell or
ringer circuit. The value for Cs is
O.lµF while a 22k0 trimpot is used
for Rt. The 10µF capacitor at pin 7
of ICl filters the DC supply.
Assembly
Assembling the printed board is
not an onerous task since there are
not many · components. The only
point to watch is the need to install
the IC and the 10µF capacitor the
right way around.
When you have installed and
soldered all components into circuit
you can check the unit on a DC
power supply. Feed in about 20
volts DC to the input terminals and
note that you get a continuous
"chirple" sound from the piezo
transducer. You can adjust the frequency of the oscillator with the
trimpot to suit your taste.
For optimum results though, we
suggest you slowly vary the trimpot
until the sound from the transducer
is loudest. There will be distinct setting for the trimpot which gives a
much louder sound output than any
other. This corresponds to the
Fig.3: parts layout for the
printed circuit board.
.J
0
,
continued on page 85
;;1·:~~ J.
L.
-~-...
~~
i°/
l<'ig.4: the printed circuit
board measures 28 x 36mm.
~l~!l~ili!i~g~~H
o fS (U;!'"'
INTERNAL TO
TELEPHONE
I
ACROSS
PHONE BELL
IC1
PSB6520
:· . _,,i ;; ;
10
63VW
+ CS
_0 1
VR1
22k
PERSONAL PHONE RINGER
121-1287
Fig.2: the complete circuit diagram for our phone
ringer.
/
I
b(6)U--""'I
FROM
PHONE BELL
!"!lo
TO
PIEZO
TRANSDUCER
,.....,.ra--,_.
, .. ,., ,, .,,. /f/ ~ ij~~
Fig.5: the circuit is so simple, it can easily be
assembled on a small piece of Veroboard. Use an
oversize drill bit to make the cuts in the tracks.
JANUARY 198B
25
ltronics Will Deliver Any Of These Quality Products To Your
Door faster Than An Other Australian Supplier
(Within 24 Hours To Every Capital City and Suburbs - Allow Additonal 24 - 48 Hours For Country Areas)
111111111 ll11111111111111111 IIIII IIIIIII II lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllIIll Ill IIII IIIIIll IIIIIII IIII IIIII IIIIII IIIIIIIIIIIIIIIIIIIIllll 11111111111111111111
The Power House Arrives
Operatea from 12 or 24 Voll 1yItemI via
Internal wiring connection,
Big brother to our 300W Model this brilliant design can be internally connected for
either 12 or 24Voperation . Full 600watt output- and that will power a fantastic array of
appliances e.g. Lighting, Electric Motors, Electric drills, Hi Fi , TV Sets, Computer.
An abaoluta muat for H°':'.11 P~w•r or for. ~h.•. Tn,c:_~,.. Jr.!l!'JOr etc.
677
f'..77
Complete Kit
Fully Built & Tested
New Model /RD Has
Fantastic Range
With Two Mode Lens
Why Pay $150 or More
Our Price $99ea
10 or More $90ea
Operates From 12V Car Battery
Just think how handy it would be to have 240 Volt AC Mains Power when camping
or for your boat or Caravan.
Auto Start draws power from your battery only when appliance is plugged in and
"turned on" . i.e. battery can be left permanently connected if desired.
Thermal Over Load. Current Regulated. Current Overload
.. t
Complete Kit
Fully Built & Tested
99.
Features:
• Lens simply 'snaps' to either wide angle
(range 40 feet) for normal use or Normal
angle (range 80 feet plus) for corridor
applications .
• Snazzy integral mounting bracket allows
corner 90 deg . mounting as well as
normal surface mo unt.(This is a fantastic
feature as these work best in corners and
are visually unobtrusive}
• 12V DC Powered
• Built-in test lamp
• Alarm output SPOT 30V 1a
S 5301
professional detectors use st ate of the art circ uitry to achieve ultra
operation. They are currently specified by several "Name" commercic>.I
mpanies.
We believe the Vector to be one of the finest and most sensitive Radar Detectors
available in the World today. Approximately 4db greater sensitivity than the A 1520
Until now, GaAs diodes have onl y been used in sophisticated military radar equipment.
The Microeye Vector is the first consumer electronics product equipped with this new
technology.
Why GaAs Diode ■ 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.
Features: • Separate audio alerts for X and K Band. • Three operational switches:
Power: On and Off: RSD (Radar Signal Discriminator) to minimize extraneous signals
with a LO (local ) positon and a LR (Long Range) position ; FIiter Mode designed for
instant computerized analysis of incoming signals with O and LA positions.
Invisible from outside your car. The Vector
simply clips onto your sun visor. Thus the
Gendames and would be villains ar
non the wiser.
Counter Kit
(See Silicon Chip Mag.
Nov 1987 for Details)
s
A 1530
UV Eprom Eraser
Erase your EPROMS quickly and safely. This unit is a
cost effect1_ve sol~t1on_to your problems. It will erase up
The Tec hnical excellence of this counter to 9 x 24 pin devices in complete safety in about 40
places it w ith Hew!"ett Pac kard and other minutes for 9 ch ips (less for less chips).
world famous test equ ipment makers.
•Erase up to 9 chip• at a time• Chip drawer
has conductive foam pad • Mains Powered
K 2515 Due Mid Dec'
• High UV intensity at ch ip surface ensures
thorough erase• Engineered to prevent UV
exposure• Long Life UV tube• Dimensions 217 x80x68mm • Weigh t 670g .
Super Bargain 1/2 Price
en volumes written about the benefits of negative ions combating air
rette smoke etc. can be very beneficial to Asthma suffer--3rs. Our gnat
erates · ·
·
second! Inc ludes tester.
Heart disease strikes down many people in
their early 40's (or even 30's). The tragedy
remains that had such victims been alerted ,
remedial n,edical , physical and dietary
action could have been prescribed to avoid
illness and in many cases restore full bodily
health . X 3055
Blood Pressure and Heart
Rate Monitor
Feature•:
• Non- Microphone Measurement System
• LCD Readout
gs
h Po
uallty
Virtually a~h~!XP.~~e~ol!!~!ake~~w~s~B!en~o~P~!o~!ne Cones
with their drivers. The advantages are considerable• less cone flexing or "break up", improved
bottom end response and reduced enclosure sizes.
One of the probl~ms of course, has been the high cost of P-P drivers. Fortunately, with Altronlca
direct Import prices, you can now be the owner of any ol the18 fine 1peaker1 tor I lr1cUon of what
you'd expect.
Note: the conservative power ratings, the massive magnets employed and
high order sensitivity specifications with these fine Drivers.
Brief Specifications (All 8 ohm Voice Coil Impedance)
oofer
100W Mu
C 3055
C 3060
Frequency Re1pon19 fo-3000Hz Resonant
Frequency 36Hz Sensitivity (1 M/ 1Watt) 87 db (+
or -2db Voice Coll 25mm Nell Weight 900gm
Electromagnetic Q .48 Magnet 280 gm.
P 3000
P 3010
P 3020
P 3030
P 3040
P 3050
P 3090
Male 9 Pin
Female 9 Pin
Male PCB Rt/l
Fmale PCB RVL
Male PCB mnt.
Fmale PCB mnt.
Backshell cover
2.95
3.25
3.75
4.50
2.95
3.95
P 3100
r 3110
P 3120
P 3130
P 3140
P 3150
P 3190
Male 15 Pin
Fmale 15 Pin
Male PCB Rt/L
Fmale PCB RVL
Male PCB mnt.
Fmale PCB
Backshell cover
3.25
3.85
4.35
5.50
3.85
4.85
2.20
P 3200
P 3210
P 3220
P 3230
P 3240
P 3250
P 3290
Male 25 Pin
Fmale 25 Pin
Male PCB Rt/l
Fmale PCB Rt/l
Male PCB mnt.
Fmale PCB mnt.
Backshel I cover
Frequency Re1pon19 Fo-3000Hz Re1onant .
Frequency 33Hz Senaltlvlty(M/ 1 Walt) 90db (+
or-2db) Voice Coll 38mm Nett Welght2200 gm.
Electromagnetic Q 4 Magnet 836 gm.
•
C 3070
C 3065
15
25
1.95
150W Mu
100W Mu .
15
Frequency Reaponl8 fo-3000Hz Resonant
Frequency 30Hz Sen1ltlvlty (1 M/1 Wall) 92db (+
or -2db) Voice Coll 38mm Nell Weight 2650 gm
Electromagnetlc Q .23 Magnet 836 gm.
29
•
Frequency Reaponl8 fo-2000Hz Resonant
Frequency 23Hz Sen1ltlvtty (1 M/ 1Watt) 93db ( +
or -2db) Voice Coll 38mm Nell Weight 3620 gm
Electromagnet Q .22 Magnet 1410 gm.
II IIIIII III IIIIIIIII I111111111111111111111111111111111111111111111III IIIIIIUIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIII
115
S•
~~-~
•
•
The use of Super Heavy Duty Heatsinks as Rack Case sides now
allows a myriad of Amplifiers, Power Supplies, Battery Chargers
etc. to be built in an "Off the Shelf" rack case.
10•
Fantaallc tor Stereo Ampllflers-Each Heatalnk wtll
accommodate an audio output 1tage of approxlmately 120W wtth
normal efficiency and dlsllpallon.
A Great Cha11l1 lor Heavy Duty Power Supplies and Battery
Chargers. We 1uggest the mounting of Rectifier Bridge or diodes
on one Heatslnk and the Regulator devices on the other.
4.95
5.50
4.95
6.90
4.95
6.25
2.20
Order With Either Black Or Natural Anodised Front Panela
Natural Anodised Front Panel
Specifications:
Heatalnks Altronics H 0590 Front Panel 3 unit Rack size 480mm x 132mm x 3mm Base 1.0mm steel, ventilation slots provided Top
Cover 1.0mm steel, ventilation slots provided Internal Dlmen1lon1125 x 370 x 250mm External Dimensions 130 x 440 x 252U'm plus
standard front panel Finish Black anodised aluminium plus powder coat black top/ base.
hassls
Now your preamps, Amps, Control Modules Monitor
Panels etc. can look every bit as good as Technlcs
Nakamlchl and other top manufacturers.
Please Note: This
product is a genuine
Pan Brake Bender
allowing you to make
quite complex chassis
boxes, lids, trays etc. It is made from solid steel and is not
to be confused with inferior Non Pan
Brake simple benders currently sold
by our competitors.
Make Your own
Chassis and Cases
and Save a Fortune
Value Plus
T 2400 ......... $99.95
e Su erb Micron Varlabl
FEATURES: These beautifully craftea racK cabinet boxes will give your
equipment.a real 1st class appearance with removable top and bottom
cover panels • All dimensioning conforms to the International Standard
• Netural or Black finish • Ventilated lid • Deluxe finish front panel
• Individually cartoned• Supplied in Flat Pack Form - Easily assembled in
minutes - Side Elevallon1:- D=254mm C (Internal Chassis Height)•
B (mounting Bolt Centres).
SIX NATURAL AND BLACK FINISH MODELS - The Black or Natural
finish cabinets are each available in 44mm, 88mm or 132mm high models.
Mountirig hole centres conform exactly to International Racking
Specifications both vertically and horizontally.
Cat. No. Flnlah
Natural
H 0401
H 0402
Natural
H 0403
Natural
H 0411
Black
H 0412
Black
H 0413
Black
A
44
88
132
B
34
57
89
44
34
88
~32
57
89
C
38
82
126
38
82
126
Were
$59.95
$69.95
$85.00
$59.95
$79.95
$89.95
No more changing tips to obtain the
correct working temperature - simply
select any one of 5 temperature settings
between 320 and 440 deg. C
Temperature Readout via. LED
bargraph.
Temperature Stablllty to
within 4% of selected mean
temperature.
Heat Capacity full 48 watts
available for H/D work .
Low Voltage Element
Slllcon rubber bum
re1l1tant lead Chrome
plated Iron clad llpa.
*
*
*
T 2440
Be Qulckl Next Month $139
a er
Own An lnphone
And Your Neighbours Will
Be Green With Envy
Here's Why
Its Completely Mobile The Go Anywhere Cordless lnphone
No
Installation
Costs
Simply Plugs
Into Your
Phone Socket
•
lnphone Is
Great Around The
Factory or Building
Site
is not tied to the wall with wires - you simply take it where
you want. Never again need you spend half the night
crouched around the kitchen bench or draughty
hallway with those long winded calls.
•
Use It By
The fireside fn Your
Favourite Chair
•
Super Handy
When Sunbaking
By The Pool
INPHONE is quite simply the finest cordless phone
available . No other cordless phone has the quality ,
security and the features at any where near an
affordable price of INPHONE.
AT HOME you can keep in touch around the
swimming pool. (Please note the equipment
is not waterproof). In the garden . Under the
car. While watching T.V. In the bathroom .
In Bed . Or next door when you' re playing
cards or having a Barbecue with your
Microphone
neighbours.
IN BUSINESS a busy executive can take the
INPHONE around the factory, warehouse ,
showroom , sales yard or construction site
or into the car park, and not miss a
deal! Also INPHONE is ideal for
use in restaurants.
IN SPORT on the field or track ,
the gym , around the swimming
pool , Lifesavers on the
beach etc .
Comprehensive 6 months
Warranty
Brilliant
Performer
SIMPLY GREAT
AROUND THE POOL
Normally Great Value At S269
Exclusive Offer To Readers Of Silicon Chip Magazine
This Month
·
S 199 -
But You Must Mention T ·
When Ordering
We Regret This Special Offer May Not Be
Available From Altronics Dealers
dvert
Just lmag ne a
an Hour -
ys em you can na a n abou
Uses No Wiring or Cables and Costs Less than $1 for the
Mounting Hardware
e
/
Fantastic UHF 305MHz Microprocessor Control
Wireless Security Alarm System
Commercial grade, quality alarm systems are expensive - Just phone one of the "Name" security firms and get a quote for your home-our estimate
is that it will be anything up to $1,000 just for the equipment-then there 11 the ln1tallatlon-countless holes punched through walls, miles of wiring and a
day or two of installers labour and that'• around $25 per hour theM day,. Hardly worth the effort 11 It? After all what h■ve you gotto looM?-Only the
'Video Player, CD Player, Camera, HI FI, TV, Jewellery and 10 onll
Well all that 11 now changed-with our brllllantly englnHred Home Guard WlrlH1 Security Sy1tem Read OnApart from the flawless operation of the Home Guard System-One of the great features is its application with rented or leased premises-Lets face it,
money spent on installing a wired system in your Home or Office. Factory etc. is irrevocably lost when you move on. With the Home Guard you simply
take it with you .
·
This alarm system is a brand new design that features completely wireless
connection to all accessories. even the reed switches. Think of how easy it
Ideal for the lounge room, family room or
is to install a "Wireless" alarm system. The benefits are endless,
hallways e.g. anywhere where an intruder is
e.g. arming your Flat or Townhouse with an alarm you don't need to run likely to pass through. Mounts up on the wall or
wires through the roof or drill great holes through your walls. When
moving house the alarm is simple to dismantle and re-install elsewhe,e. on top of bookshelves etc. Detects movement
within an area of 9M by 9M by sensing intruder
The system divides protected 3reas into either perimeter zone or internal body heat movement through the protected area
zone, programmable by dip switches in each transmitter/ detector. Pocket Should not false trigger with the family cat or
remote control can simply arm or disarm your house perimeter from your curtain movement etc. - as is the case with the
bedside when retiring etc. this allows essential protection while cancelling cheaper Ultrasonic alarms.
internal zone as desired. Each transmitter/ detector unit can be
programmed into interior or perimeter zone. Zones can be programmed S 5280
1 9
for instant or delayed trip . The system has a built-in ear piercing siren for
•• · • ' ••· •· •••' ••
intrusion and panic alarm signals. It also has another dry relay output with
normally closed, normally open contacts for connecting to other alarm
reporting devices such as telephone dialer, additic;,nal outdoor siren etc.
System Is Comprised Of :
This unit is an optional line carrier receiver.
Receives signal through 'AC' line i.e. it would
ideally be located in, say, the roof space and
plugged into mains power .
S 5290
peclal Package Price
Comprl1lng:
One S 5265 Main Controller
One S 5270 Reed Switch
One S 5280 Passive I/R Detector
One S 5285. Wall control unit.
Including Batteries
Sy1tem Cat.No. S 5260 .... . .
Accessories
• Wireless reception of external or internal sensors or detectors .
• Selectable home or away modes for selecting internal and external
arming or just external to allow movement inside the building
• Built in Piezoelectric siren gives different signals to indicate different
functions.
• Sends signal down power line to activate one or more remote sirens.
• Programmable Arm/ Disarm switch buttons.
The main control receiver runs on 240V AC with a 12V 1.2AH battery for
emergency backup. All other units with the exception of the line carrier,
run on a 9V battery each . The average life expectancy is approximately
one year. System works around the 305MHz frequency where there is less
chance of false alarm. The range of the unit is normally 80 metres in open
space.
Alarm and Indication
Sound ■
Intrusion Alarm - Panic Alarm - Arm Tone - Disarm Tone - Exit Click
Tone - Monitor Tone - Tampering Alarm .
qeed Switch)
Suitable for Window, and Doore
This consists of an enclosed reed switch and
compact UHF transmitter and a removable
enclosed magnet. The unit is at rest when
magnet and reed are side by side (within 25mm
or 1 inch). When the magnet is moved away
more than approximately 1 inch the alarm
signals to the Main Control Receiver and the
alarm is sounded. In practise the
Reed/ Transmitter is mounted on the door or
window frame with the magnet on the moving
door or window .
Note: For larger installations your system may well require several Reed
switches, movement detectors and 2 or more sirens . Also the remote door ,
controller and or pocket remote controls could be very worth while
accessories. The fantastic thing about the Altronic system is you simply
add more detectors as you discover the need - no wiring, no e:<pensive
technicians. no modifications to equipment.
A real joy to use - keep it at the bedside table allows you to, say, alarm the house perimeters
when retiring or you can take it with you when
you go out, arming your system after you lock
the door. Unit is a function control transmitterto send 4 different signals.
011 - To disarm the system before entering .
Home - To instantly arm the system with
'Perimeter' detection only. Away - To arm
complete system after a given exit delay time of
about 40 seconds. Panic - To start an
emergency signal whenever needed, in any
mode.
S 5275
nt Door Keypad
This handy accessory virtually duplicates the
function of the Master Controller unit but at a
more convenient location i.e. just inside your
entry door etc. System can thus be armed or
disarmed without the need to go to Master unit.
Especially handy for larger homes or offices.
S 5285 ................................ .
rs for Long Range,
ro uction
Altronics proudly release the Eleco
System - Used Worldwide by Entertainers
i.e. Rolling Stones, Dire Straites,
Tina Turner and 1000's more!
Superb
Microphone
Reproduction
Compares with
Shure,Beyer
and AKG
Unique
Microphone
design completely
Eliminates
"Dangling"
Antenna
Breathtaking performance without signal drop-out or noise interference. The Eleco Wireless Microphone System
Is virtually the ultimate in an Entertainers Microphone system (or for any roving microphone application for that
matter!)
All the annoying wireless microphone characteristics such as "drop out", static and noise are completely
eliminated by use of auto 1wltchlng dual diversity recelvere. The output of each receiver is continually monitored,
with the strongest and clearest signal always selected. Dynamic Range exceeding 100 db is obtained by
employment-of a Patented special Parabola level compressor and Dynamic expander.
The operating range 11 a minimum of 50 metres (often this can be extended to 200 metres and more in normal
circumstances).
Several Frequencle1 are available to aleviate cross interference when two or more systems are used in proximity.
Brief Specifications Frequency 202.1, 202.9, 203.7 MHz (Please specify if you have a preference)
Mlc Carrier Power i;omW (Max) Mlc Antenna built-in Dynamic Range over 100db S/N Ratio better than 90db Frequency Re1pon1e 20Hz to 16KHz + or - 3db
Mlc Battery 4 x AA cells Battery Life over 24 hours continuous operation. RecelverSen ■ltlvlty 12db/microvoltfor60db S/N ratio Preemphaol ■/De emphaol■ sous.
Receiver output unbalanced 6.3mm phone jack and balanced 3 pin cannon type. Output Level (adjustable) Unbalanced 0-2.SV Balanced Oto+ or - .3V into
600 ohms. Receiver Power Supply 200 - 260VAC.
Prices
(A) Dual Diversity Receiver $729.00
(B) Entertainment Microphone (hand held type)
(C) Lavalier Type Microphone $349.00
•
Fr• ue
C 0111
C 0113
C 0115
C 0121
C 0123
C 0125
C 0131
C 0133
C 0135
$349.00
ecelver and
J •• 999
Please Note 3 different operating frequencies are available (you will need to
specifically nominate desired frequency only if the equipment is being used in
proximity with other Eleco Systems on the 200MHz band.
•
Dual Diversity Receiver
Dual Diversity Receiver
Dual Diversity Receiver
Entertainment Microphone
Entertainment Microphone
Entertainment Microphone
Lavalier Microphone
Lavalier Microphone
Lavalier Microphone
202.1MHz
202.9MHz
203.7MHz
202.1MHz
202.9MHz
203.7MHz
202.1MHz
202.9MHz
203.7MHz
$729
$729
$729
$349
$349
$349
$349
$349
$349
IIIIIIIIIIIIIIIIIIIIIIIII IIIIIIII IIIIIll IIll II IIIIIIIIIIIIIIIIIIIII IIIIIIIIIII1111111111111111111111111
Wide Range
Weatherproof Extension
Speakers For Your Stereo
System
G a F r The Back
Patio, wlmmlng
Pool, Games Room ,
Den Pool Ro m E
g
I y
Weather Proof Speakers
ed ord
• Rugged extruded aluminium construction • Superb
powdercoat industrial paint finish • Engineered in
Australia • Excellent reproduction • Superior to imports
- Yet just a fraction of the price!
Altronics proudly announce the release of
the superb Redford Weatherproof Speaker
and Sound Column Range. Imagine a wide
range speaker system which is highly
directional and with efficiency approaching that of reflex horns!
Redford is the solution for high quality
sound reproduction outdoors. The Five
Models to choose from '.'FIii the Bill" from
applications on boats to high grade paging
and music entertainment installations.
D
11 OhM M
Using a dual doped cone driver these fantastic weatherproof speakers are of quite
surprising performance.
The 4 Ohm models are intended for use as main speakers i.e. for car sound systems/
graphic equalisers on your boat or Four Wheel drive etc.
The 16 Ohm versions are intended for use with higher power systems. 16 ohms is
employed to give a generally correct volume balance when used as extension speakers
to the main speaker system - An added bonus is your amplifier load is kept to
respectable limits! Great for back patio, den etc.
C 0932
White 4 Ohm
C 0938
White 16 Ohm
C 0,934
Black 4 Ohm
C 0940 Black 16 Ohm
All $99 each
or
$190 per Pair
u
These vibration free enclosures are
constructed from die extruded heavy
gauge aluminium and finished with
incredibly durable industrial powdercoat
enamel. The speaker ends are sealed via
gaskets and tough moulded "LU RAN S" U /
resistant end caps. The end result iS "Good
Looks" together with assured rugged
durabilitv for the Australian environment.
The drivers have been chosen for wide
range.low distortion, mid range "pr_esence"
(essential for high grade vocal work) and
high efficiency in general. Power Capacity
for short term use, the drivers will safely
handle 150% of rated power. Acoustic
wadding is used to dampen Bass
resonance. Weather Proof Con ■trucllon
and uae of "Doped Cone1" Foam plastic
and cloth is sandwiched between Baffle
and Front Grill to prevent water ingress. A
first for Redford is the use of a patented
cone moisture repellant process for all
models.
Dimensions 260mm wide
x 170mm high x 150mm D.
(Mounting brackets are
included)
20
I Oltm (Ml 30 Watt)
■t
Use 2 special dual doped cone drivers for those wanting a bit more umph!
C 0943
C 0944
f
Black
White
100 Volt L
$139ea
$139ea
o
A
$260 per pair
$260 per pair
II F
UN Ith Prof
Mualc Sy tem
PA
Using a "Doped" wide range drivers and fitted with grain oriented steel line transformer
Output cable allows connection to 10W/SW/2.SW with 10 watt models, 20W/10W/5W
with 20 watt models and 40W/20W/10W with the 40 watt versions.
C
C
C
C
C
C
_
0941 10W/100V line Black $119ea $220 per pair
0942 10W/100V line White $119ea $220 per pair
0945 20W/100V line Black $169ea $299 per pair
0946 20W/100V line White $169ea $299 per pair
0950 40W/100V line Black $225ea $399 per pair
0955 40W/100V line White $225ea $399 per pair
:4
••
(.
L.
~- .. .
-1
••
I
"
•
$17.50
(
" NO NEED
TO
Low-Cost Unit
UNSOLDER
Checks Values from 1pF -1 00uF
SUSPECT
TRANSISTORS "
FEATURES:
* Output 3 to 30V at 1A * Short circuit
The readout consists of a bright 4-digit LED display and the full scale
readings for each range are 9999.9nF and 99.99uF. No adjustments are
necessary when taking a reading . You simply connect the capacitor to the
• Tests both NPN and PNP trans istors 1n
test terminals and select the appropriate range. The circuit can accurately
circuit at the touch of a switch • Tests
measure capacitance down to one picofarad (1 pF). This is made possible
Diodes and SCRS as well • No need to
by the internal nulling circuit which cancels any stray capacitance
switch between NPN and PNP- its
automatic. Two LED indicators are used to between the test terminals or test leads . So when you measure a 5pF
show condition of device being tested .
capacitor, the unit will display 5pF.
Altronlc1 Kit Feature - " ABS" jiffy box and
test leads supplied. Cat. K 2530
K 2522 .. . ............................. .
protec ted* Load switchi n g* Current lim iting . Dual sc ale meter • Housed in o ur
Deluxe " ABS " instrument case .
FEATURES:
SPECIFICATIONS:
* Output Voltage - 3 to 30V * Output
Curren t - O to l amp (full y variable ) • Load
Regulation - Better than 0 .2% from Oto ful l
load* Output Ripple-Less tha n 2mV RM S.
Cat . K 3210
This Ultrasonic Movement Detector provides added protection against illegal entry via.
an open window etc . Connects d irectly to an alarm with a normally open input. Detects
Dead easy to build and (even better ) there
ara only 3 electrical connections required
to the car wiring system .
This alarm drives off would be thieves with
an ear splitting modulated tone. Once
activated it is near impossible to stay within
the confines of the car.
Featuret: Entry Delay• Exit Delay• Alarm
Timer • Lamp Flasher • Three second soft
alarm reminder. Piezo siren produces
any movement up to 3 metres within an angle of 30 degrees. Will operate directly oft 12V
i.e. Car Battery etc .
4400
29.50
modulated tone of 110dbat 1 metre. Simple
to build and install. Two Sensor Inputs
Sharpens up your picture when Copying
Video to Video
Here's a ■ lmple but effective video enhancer that is
super eHy to bulld at a fraction of the cost of
commercial mod~ls. Unit sharpens picture detail ,
and can .actually improve the quality of a copy by
amplyfy,ng the top end of the video signal K 5825
174 Roe St. Perth W.A. 6000
Perth Metro & After Hours (09) 328 1599
P.O. Box 8350 Perth Mail Exchange W.A.6000
.
- We process
your order the day received and despatch via. Australia Post. Allow approx 7 days from
day you post ord er to when you receive goods. Weight limited 1 Kgs.
.
- We process your order the day received and
despatch v1.a. Overnight Jetservlce Courier for delivery next day Country areas please
allow addItIonal 24-48 hours . Weight limit 3Kgs.
days for delivery
- For deliveries exceeding 3Kgs and less than 10Kgs - allow 7
-
All orders of 10Kgs or more must travel Express
Road - Please allow 7 days for delivery.
.
. - As with virtually _every oth~r Au~tra~ ian 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" .
- Bank~ard Holde rs can phone order toll free up to 6pm
Eastern Standard Time. Remember with our Overnlg_ht Jet■ervlce we deliver next day.
ALTRONICS RESELLERS
Cha~ces are there is an Altronics Reseller right near you - check this list or phone us for
details of the nearest dealer. Please Note: Resellers have to pay the cost of freight and
insuran?e and therefor~ the prices charged by individual Dealers may vary slightly
f~om_ ~his Catalogu~ - in many cases, however, Dealer prices will still represent a
srgn,f1cant cost saving from pnces charged by Altronics Competitors.
Don't forget our Expreu Mall and Phone Order Service • tor the cost of a local call
Bankcard, Visa or Ma■tercard holders can phone order for ■ame day de■patch.
'
If you have a Retail Shop, you could increase
significantly by becoming an Altronics Dealer,
Fobister (09) 328 2199 for Details.
COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K.B.Electronics &
Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronics 854836 MANDURAH Lance Rock
Retravision 351246 NEWMAN Watronics 751734 WYALKATCHEM D & J Pease 811132
ALICE SPRINGS Ascom Electronics 521713 Farmer
Electronics 522967
CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334
CITY Active Wholesale ■ 6023499
All Electronic Components 6623506 SUBURBAN
ASPENDALE Giltronics 5809839 CHELTENHAM Talking Electronics 5502386 CROYDEN Truscott
Electronics ■ 7233860 PRESTON Preston Electronics 4840191
COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell
Electronics 346133 SWAN Hill Cornish Radio Services 321427
CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE
VALLEY Economic Electronics 523762 Fred Hoe & Sons Electronics 2774311 PADDINGTON SLACKS CREEK David Hall
Electronics 2088808 TOOWONG Techniparts 6710879 COUNTRY
CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins
Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 NAMBOUR Nambour Electronics 411604 PALM BEACH The
Electronic Centre 341248 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron
World 278988 Purely Electronics (Shopping Fair) 280100 Xanthos
Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015
CITY Electronic Comp & Equip . 2125999 Force
Electronic ■ 2122672 SUBURBAN
BRIGHTON Brighton Electronics ■ 2963531 CHRISTIES BEACH Force Electronics ■ 3823368 ENFIELD Force
Electronics ■ 3496340 PROSPECT Jensen Electronics ■ 2694744 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics
■ 454764
HOBART George Harvey ■ 342233 LAUNCESTON Advanced Electronics 315688 George Harvey ■ 316533 Nichols Radio
. TV 316171
CITY David Reid Electronics ■ 2671385 SUBURBAN BLACKTOWN Wavetront Electronics 8311908 CARINGHAH Hicom
Unitronics 5247878 LEWISHAM PrePak
Electronics 5699770 SMITHFIELD Chantronics 6097218 COUNTRY ALBURY Webb's
Electronics
■ 254066 COFFS HARBOUR Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NEWCASTLE Novocastrian Elect.Supplies
■ 621358
NOWRA Ewing Electronics ■ 218412 ORANGE RAYMOND TERRACE Alback Electronics 873419 TENTERFIELD Nllthan Ross
Electronics 362204 WINDSOR M & E Electronics ■ Communications 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400
Blue Ribbon Dealers are highlighted with
a ■.
These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item tor you.
HIFIREVIEW
arantz's elegant
compact disc la er
Marantz is moving up market. That's the very
strong conclusion we came to after looking at their
latest CD player, the CD-94. This machine leaves
previous models for dead in terms of operating
refinement, sound quality and, most of all, finish.
Reviewed by LEO SIMPSON
In the last few years Marantz has
gone through its vicissitudes but
now it has a new direction and commitment to the highest audio fidelity. This new direction has been
mostly due to its chief audio
designer Ken Ishiwata, a Japaneseborn engineer operating at
Marantz headquarters in Eindhoven, Holland.
His hand was clearly demonstrated in Marantz's award winning PM94 stereo amplifier and one
can see that a great effort has been
made to achieve the same standards with the CD-94.
Let's face it. There are many
cheap compact disc players on the
market and as far as most people
are concerned these do a perfectly
satisfactory job; they play the
music and they do it to a far higher
standard than their delighted
owners were probably used to with
32
SILICON CHIP
their disc-based equipment.
But there is more to the compact
disc than just the basic CD players.
There are a substantial number of
people who want quite a lot more
than the basic machines offer. And
up till now, there have not been
many machines catering to their
needs. There probably never will be
but this new machine from Marantz
is certainly a contender for the very
top of the market.
Unfortunately, mere photos do
not do the Marantz CD-94 justice.
They can't show the very fine
finish. They can't show the glasslike texture of the timber end
panels, the subtle colouring of control panel illumination and major
control lights. Nor do they show the
solidity of the machine, or the action of its controls.
We'll attempt to tell you
something of the physical attributes
of the machine but you really need
to have it demonstrated "in the
flesh" to fully appreciate it.
At first it does not look all that
different from other CD players. It
is largish but not overly so and
since so many CD players are black
these days it does not really stand
out as being really different; quite
the opposite in fact. It is unobtrusive. It has very few controls
visible on its front panel.
Turn it on though and it starts to
look more the part. Its display panel
lights in a very subtle blue (it's a
vacuum fluorescent display) with a
large pair of digits for track
number and then smaller digits to
show index numbering and elapsed
time in minutes and seconds. There
is also a line of very small digits
which show the number of tracks
on a disc (up to 24) and those that
have been played. What we like
about this display is that it is bright
enough without being at all gaudy.
Press a very discreet open/close
button and the disc drawer slides
out quickly and smoothly. So many
CD players give a poor impression
at this stage. The drawer either
makes graunching noises, or is too
slow or is jerky. None of that with
the CD-94.
Once the disc is dropped onto the
Inside the rigid diecast aluminium chassis of the CD94: note the generous transformer and all the capacitors which
are specially made for Marantz. The player is particularly immune to shock and vibration, a legacy of the
comprehensive error correction circuitry and the rigid construction.
platform, you can either nudge the
drawer to make it withdraw or you
can push the open/close button to
achieve the same result. Good. This
is a most desirable feature since
not a few players can be jammed or
damaged if the CD drawer is
physically pushed home.
The only other controls visible on
the front panel are the two large
buttons to the right of the display
panel for play/replay and
pause/stop, and three small buttons
below the display for FTS (favourite
track selection) and track selection
(forward/reverse). That may not
seem like enough until you lightly
press the lower part of the front
panel. It then drops open smoothly
(damped by a dashpot) to reveal a
whole array of controls to enable
you to make the machine do just
about anything.
Paradoxically though, most users
will probably never use these controls because, as far as we were
able to determine, it can all be done
with the infrared remote control.
Playing features
The CD-94 has all the playing
features of most compact disc
machines and a lot more besides.
One of these is shuffle play. Instead
of playing the disc through from
start to finish, you can press "shuffle" and have the tracks played in
random order. This can be a pleasant change when playing anything
except classical music.
Another unusual facility on the
CD-94 is "FTS" which stands for
favourite track selection. This
enables you to program the
machine to play selected tracks on
a compact disc and omit the others.
Once you have programmed the
machine for a particular disc it will
always remember it. Thereafter, as
soon as you feed the disc into the
machine, it shows FTS on the
display and you can then play the
programmed selections by pushing
the FTS button on the front panel or
on the remote control.
Depending on how you use it, the
Marantz can store a hundred or
more compact disc 'favourite track
selections'. For example, 155 discs
can be programmed to play an
average of five tracks each. In some
ways, we would prefer to think of
this facility as the "disliked track
non-selection" - you can program
the machine to omit those tracks
you hate. Good idea?
The CD-94 also has "Index" play
whereby you can program or select
musical passages to be played by
JANUARY 1988
33
The lower part of the front panel drops down to reveal an impressive array of control buttons for programming. There
is also a headphone socket with its own level control. A nice touch is the gold plating on the ten track selection buttons.
their index number. These are
generally not used on pop music
discs but are frequently used to
identify movements within classical
pieces.
Another facility is "AMS" or
automatic music selection. This
goes through and plays the first ten
seconds of every track.
Repeat play is also featured, a
common facility on CD players, but
the Marantz also gives a similar
facility with the Play/Replay. More
often than not, pushing the Play button while play is in progress makes
the machine move to the next track.
On the CD-94 though, pushing the
Play button makes it restart the
same track and it does it almost
instantaneously.
Response times on the CD-94 are
particularly fast. It can usually access and start playing any track on
a disc within two or three seconds,
and often much less. The worst
case, going from the first track to
the last of a 25-track disc, takes
four seconds flat!
Another feature which sets this
machine apart from others is the
provision of digital and optical fibre
outputs on the rear panel. This is
principally to allow it to be used
with Marantz's special CDA-94
Digital-to-Analog Converter. This
latter is a high precision multipurpose unit which automatically
adjusts its sampling frequency to
suit the selected input: 44. lkHz for
compact disc, 48kHz for the new
DAT (digital audio tape) machines,
and 32kHz for the anticipated
satellite broadcast audio.
Removing the highly polished
timber end pieces and the heavy
aluminium lid of the case reveals
another big difference with the
CD-94 machine. At a time when
other machines are going to all
plastic construction and weighing
only about 5 or 6kg, the Marantz
has a very rigid diecast aluminium
chassis and a diecast chassis for
the player mechanism too. All up
weight is 10.3kg.
The internal circuitry is
beautifully laid out and uses analog
componentry unique to Marantz.
This includes the large Elna electrolytic capacitors with ceramic
filling and the damped copper
styrol (polystyrene) capacitors in
the Bessel output filter stages. The
capacitor leads are also tinned
oxygen-free copper instead of the
usual tinned mild steel leads, a
feature which Ken Ishiwata claims
is important to sound quality.
A relatively large mains
transformer is used, considering
the low nominal power consumption of 30 watts. The machine is
double-insulated and we are glad
to report that the mains wiring is of
a much higher standard than a lot
of equipment which sports the
"double insulation" symbol. A
sheathed two-core mains flex is used, which is as it should be.
16-bit dual D-A converters
Marantz uses the new Philips
dual 16-bit D-A (digital-to-analog)
converters with four times oversampling. The beauty of this
system, apart from much improved
linearity, signal-to-noise ratio,
separation and all that, is that it
allows a digital filter to remove the
176.4kHz digital residual left over
The CD-94 has digital and optical outputs as well as the normal analog outputs. There are two additional sockets for
use with the Marantz bus system.
34
SILICON CHIP
after conversion. A third order
(18dB/octave) Bessel filter takes
care of the remainder of the audio
filtering.
This is better than typical
machines which use a very sharp
"brick wall" filter to remove the
residual digital artefacts which inevitably results in ripples (ie, small
deviations) in the audio passband.
Three better
from the Best.
Testing
Our first objective tests of the
CD-94 involved its tracking performance and error correction. We used the Philips No 4A defect disc and
naturally it passed all tests without
so much as a murmur. Then we fed
it a badly scratched disc which
many players refuse to load let
alone play.
Here the Marantz did very well
and probably better than any other
player we have come across. It
played all but two tracks and even
with these two, which are probably
unplayable by any machine, it made
a fair attempt before the laser pickup was thrown completely out and
the machine came to a stop.
The machine was commendably
immune to shocks and vibration.
Short of pounding on it with your
fist, it is very difficult to make it
mistrack.
Without doubt though, the most
impressive test results involved
measurement of the frequency
response. Marantz claim a frequency response from 2Hz to 20kHz
within ± 0.0ldB. When I first read
this spec I did not believe it. It
would be an unprecedented degree
of precision for any piece of electronic equipment, audio or
otherwise.
Subsequent checking proved that
the spec is genuine although I still
find it hard to believe. Up till this
time, the tightest tolerance we have
seen for any piece of electronic
equipment has been ± 0.ldB.
We knew darn well that there
was no piece of measuring gear
currently available (maybe in Standard labs there are) which would
verify the spec. But we went ahead
and measured the frequency
response anyhow.
It was uncanny, watching the
millivoltmeter pointer come up to
exactly the same reference point
for every frequency between 20Hz
The remote control duplicates all the
facilities on the player. Very fast
response times are a feature of the
machine.
and 20kHz. Clearly, the CD94 was
far better than the millivoltmeter.
Marantz quote similarly ambitious figures for signal-to-noise
ratio, separation between channels
and total harmonic distortion. S/N
ratio is quoted as better than
104dB, channel separation at better than lO0dB and harmonic
distortion as better than .0015% at
lkHz and 0dB. These are truly excellent figures.
Unfortunately, we were not able
to verify them as we presently lack
a suitable filter to remove residual
44. lkHz signal. In the CD-94,
residual 44. lkHz is at a level of
about - 70dB and this masks
signals which are much lower in
level. This is a consequence of not
using a "brickwall" filter, as we
mentioned above. Based on the performance te.sts we were able to
carry out, we have no reason at all
to doubt the machine easily complies with its specifications.
I would go further than that. Of
all the machines I have tested or used so far, I would have to rate the
Marantz CD-94 as the best overall.
It is a delightful machine to use and
to listen to. I'd love to own it.
For such a top-rating machine, it
is something of a bargain. Recommended retail price is $1699.00.
For further information, contact
Marantz (Australia) Pty Ltd on (02)
742 8322.
~
For decades, Ortofon has been recognised
as being without peer in the development
and manufacture of sound reproduction
cartridges. Today, the legend moves the
leading edge a significant step further.
You are invited to hear the introduction
of the three latest Ortofon Moving Coil
Cartridges each with 3 unique features:
1. Unsurpassed quality of the moving coil
principle.
2. High output (2mVl directly into a .
standard phono input, totally elimin~ting
the need for a step-up transformer.
3. Trade-in and trade-up options at point of
purchase.
Ortofon MC X-1 Elliptical diamond.
Ortofon MC X-3 Fineline diamond.
Ortofon MC X-5 Van den Hui diamond.
These 3 cartridges have been so well received by the hi-fi press
that we will let them complete this advertisement:
"It was one of the smoothest, silkiest, and leasHoloured
cartridges we can recall using. The Ortofon XJMC is a delightful
cartridge, the kind that can be enjoyed tor hours without creating
an urge to listen to something else. And the price is right!"
Stereo Review, March 1987.
" ... overall we consider the X3-MC a very clean, uncoloured
cartridge and among the most handsome sonically of the movingcoil models we·ve tested."
High Fidelity, January 1987.
"Whatthecartridgessharesonicallyaresweet,nonagressive
behaviour, freedom from vinyl whoosh, and an openess ideal tor
portrayal of atmosphere and ambience ... the X3 will do justice
tosystemscostingwaybeyonditspricecategory."
Stereophile, Vol. 10 No. 1.
"Colouration was very, verylow,vinyl'whoosh' and tracing
noisevirtuallynon-e,istent,andambiencewaswell-conveyedby
both IMC-Xl and MC-X3) ... it has to be regarded as an ideal
introduction to the joys of the MC ownership."
Hi-Fi News & Record Review, January 1987.
For full details and free brochures, contact the
Sole Australian Distributor, SCAN AUDIO or
your nearest ORTOFDN specialist.
SCAN AUDIO Pty. Ltd.,
52 Crown Street, Richmond, Victoria 3121.
Telephone: (03) 429 2199.
ortofon
accuracy in sound
S& T SA 5042
JANUARY 1988
35
Heathkit® SELLOUT!
The chance of a lifetimel We're clearing out our remaining stocks of famous
Heathkit products ... many WAY BELOW COSTI
Hurry - Limited stocks only!
Hero Jr. Robot.. BELOW COST!
The robot of the future is here today. It's Hero Jr - from Heathkit, of course. More
than just a robot, Hero Jr will become a real member of your family. He (she?) is
pre-programmed: Hero Jr will wake you up (even listen to make sure you're
awake!), remember dates and anniversaries, walk, talk ... protect you and your home
(it can even activate the optional Health Security Centre) and much more. You can
program Hero Jr to perform a myriad of tasks for you - with either its own keypad
or with your own home computer (using the optional RS232C link, BASIC cartridge,
terminal emulation software and cartridge adapton. Of course, Hero Jr is battery
operated (rechargeable) and comes with a recharger (240 to 115V stepdown
transformer required). How much for all this wizardry? Cat G-1005
s595
9£;
Buitt up version: was $1995 Now sg95 fii ~
In ktt fonn: Was $1395 Now
cartridge adaptor:
(for plug-in command cartridged) Cat G-1050
BELOW COST!
s79
~
t.t.\.~
Was $179 Now
Computerized Weather Station
.
\
A,!,1.
~~
'-~
--.,-
From the most respected kit builders in the world, comes the most
advanced computer weather station! Features digital clock/4 year calendar,
4 digit accuracy, barometer, thermometer, wind vector, memory and more!
WAS
NOW
'999
*395
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NOW
199
*149
CatG-2000
~!b!=.!~~ian you won't find better quality! Modulated and
unmodulated signals from 310kHz to 110MHz with calibrated harmonics to
220MHz. Cat G-4005
1
Audio Signal Generator
An economical piece of test gear that you'll find essential for audio and
WAS
digital circuits. 10Hz to 100kHz frequency range with both sine and square 1
159'8
wave output. Battery operated (2 x 9V batteries, not inc.) Cat G-4010
Signal Tracer Kit
Save a heap of time on repairs! The signal tracer kit will check RF, IF, even
WAS
audio circuitry quickly and easily. Ideal for any workbench! Cat G-4015
1
189'8
Hobbyisfs R-L-C Bridge can Sava your money!
Your junkbox is probably choka with unmarked components. Don't throw
them out - or buy new ones: Check them with this R-L-C Bridge. Put it
together in about 4 hours - and start saving! Resistance: 10 ohms to 10M.
Capacitance: 10pF to 10uF. Inductance: 10uH to 10H. Cat G-4025
NOW
*149
NOW
*129
WAS
NOW
' 199
*169
DICKe SMITH
c~'itaTIi~LJCf~ ELECTRON
° ICS
ONLY AVAILABLE THROUGH
DSXpress
Sydney (02) area cal 888 2105
PTY LTD
Build this low cost
Dual tracking
±18.5V po"7er supply
Take a squiz at this: a dual tracking
power supply of modest cost giving up to
+ 18.5 volts DC. It has voltage metering,
a LED dropout indicator and short
circuit protection.
By JOHN CLARKE & LEO SIMPSON
Sooner or later, every electronics
enthusiast needs a DC power supply. They used to get by with a
variable supply giving up to 15 volts
or so at around 500 milliamps but
today's circuits using op amps,
memory and logic devices need a lot
more than that. For op amps you
need balanced positive and
negative supplies of ± 15V while
some memory chips such as
EPROMs need ± 5V.
The problem with designing a
power supply for the enthusiast or
technican is that it is easy to get
carried away with fancy features
that are seldom used. The end
result is an expensive supply that
no one can afford. So we at SILICON
CHIP have put our heads together on
this project to produce a supply
which has good performance and
features while keeping the cost
within bounds.
What are the big cost items in a
power supply? That was the question we asked ourselves as we set
out to design this supply. The big
cost items are the transformer,
meter, case, filter capacitors and
printed circuit board. We could not
eliminate any of these components
in a self-contained power supply so
we selected them very carefully to
optimise the performance versus
price ratio.
For example, we selected a
transformer with a centre-tapped
30V winding rated at one amp. This
was much cheaper than a centretapped 44V 1.5-amp transformer
that we would have selected as first
choice if price was not so important. But we had to admit that the
times when enthusiasts want high
currents are fairly rare.
By picking the smaller transformer, we greatly cut down the
power dissipation in the circuit and
thereby reduced the heatsinking requirements, the size of the case and
the cost of the filter capacitors and
regulatprs, all for very little reduction in overall utility of the supply.
We also saved money by using a
smaller meter, smaller rectifier
diodes and so on.
The end result is a compact
power supply which will serve the
needs of the vast majority of electronic enthusiasts and technicians.
It will become another in a growing
list of SILICON CHIP test equipment.
JANUARY 1988
37
D7
1N4002
POWER
LOAD
S2a
0--0+
E •
2.7k
2200
+
25VW
_
100
+
25VW
D10
1N4002
-14V
47k
1200
LOAD
OUT
S2b
o-o-
2.7k
08
2.2M
LED2
DROPDUT
D11
DUAL TRACKING POWER SUPPLY
D41-188
...
..,.
4x1N4148
Fig.2: the circuit uses a 30V 1A transformer to drive a bridge rectifier and two adjustable 3-terminal regulators. ICl
inverts the control voltage provided by VR1 to drive the LM337. IC2 monitors the output ripple to provide drop-out
indication.
The SILICON CHIP power supply
has tracking positive and negative
DC outputs adjustable from ± 1.2V
to ± 18.5V. Both supply rails are
protected against short circuits and
2.Dr x~ - - - . - - - - . - - - - . --
--,
~
::E
5.
...
~ 1.011--f'----+---
=
:::,
c.,
-+-----+----t
c:,
;
D._._ _...,__ __.__ __.__ _
D 1.2
Fip, 1
10
~
15
SUPPLY VOLTAGE (VOLTS)
Fig.1: this graph plots the maximum
output current for voltage settings
between ± 1.2V and ± 18V.
38
SILICON CHIP
20
voltages generated by external
loads.
Maximum load current is 1. 7A
between ± 3V and ± 10V. When
the supply stops regulating, a LED
indicator lights.
You can use the power supply in
the conventional way to provide
balanced positive and negative
rails, or you can take the output
from between the positive and
negative output teminals and
thereby get more than 36 volts DC
output. The circuit is fully floating
(ie, not tied to mains earth) and so
the output can be referenced to
earth via the positive, negative or
0V rail.
What will it do?
Fig.1 shows the maximum output
current available for voltage settings between ± 1. 2 volts and ± 18
volts DC with the positive and
negative rails loaded. Up to 1. 7
amps is available for settings between ± 3 and ± 10V. Above 10V
the available current reduces, to
200 milliamps at ± 18 volts.
Remember that this performance
applies with both the positive and
negative rails loaded, so that by
taking the output between the
positive and negative rails, you get
get up to 1. 7 amps at 20 volts and
up to 200 milliamps at 36 volts.
Line regulation is within ± 5mV
of a given output voltage setting for
mains input variation between
220V AC and 260VAC. Load regulation at 1.7 amps is within 100mV at
a setting of 9 volts; ie, close to 1 % .
Ripple output (ie, 100Hz hum and
noise superimposed on the DC rails)
is less than lmV peak-to-peak for
load currents up to one amp. These
are excellent figures. Dinkum.
Note that the actual maximum
The supply is very easy to wire but you should take extra care with the mains
wiring. Use a cord-grip grommet to secure the mains cord.
available current from the power
supply will depend on the
temperature of the heatsink and the
amount of power being dissipated
in the regulator(s) for a given output
setting.
Circuit details
Fig.2 shows the complete circuit.
As already noted, it is based on a
30V centre-tapped 1A power
transformer, Arlec 6672A or
equivalent. Diodes Dl to D4 are
connected as a bridge rectifier
which, combined with the two
22001,lF filter capacitors, give plus
and minus DC rails of about 21
volts.
These unregulated DC rails are
fed to LM317 and LM337
3-terminal regulators to provide the
adjustable plus and minus supply
outputs respectively. We'll briefly
explain how these regulators work
before going on with the rest of the
circuit description.
· The regulators are designed to
give 1.25V between their output
and adjust terminals. With this in
mind, and the fact that the current
flowing out of their ADJ (stands for
ADJust) terminal is negligible, it is
easy to design a variable regulated
Fig.3: operating principle of the
LM317 3-terminal regulator. Rt
and R2 set the output voltage (see
text).
·
supply. The circuit of Fig.3
demonstrates their operating
principle.
Two resistors are used to set the
output voltage in the circuit of
Fig.3. Rl is fixed while R2 is
variable. Since the voltage be~ween
the OUT and ADJ terminals is fixed
at 1.25V, the current through Rl
and R2 is also fixed. This gives a
simple formula for the output
voltage as follows:
Vout = 1.25(1 + R2/R1)
In our circuit Rl is 1200 while R2
is made up of of a 2.7k0 resistor in
parallel with VRl, a 5k0 potentiometer. The maximum effective
value of R2 is thus 1.75k0 and the
theoretical output voltage range is
therefore between 1.25 volts and
19.5 volts. However, the
unregulated DC voltage fed into the
regulators is normally not quite
high enough to enable 19.5 volts
output to be delivered.
That explains the circuit as far
as the positive regulator (LM317) is
concerned but what about the
negative regulator'? It has an operational amplifier connected to its
ADJ terminal instead of a variable
resistor. What giveth'?
The idea of the op amp is to provide a mirror of the voltage at the
ADJ terminal of the positive
regulator. So if the ADJ voltage at
the positive regulator is + 10 volts,
the op amp will produce an output
of - 10 volts by virtue of the fact
that it is connected as a unity gain
inverting amplifier. So ICl ensures
that the negative regulator always
tracks with the positive regulator.
The 1200 resistor between the
ADJ terminal and output of the
LM337 is there for two reasons:
first, to give the required minimum
load for the regulator, and second
to set a load current flow into ICl.
This load current of 10.4 milliamps
impresses a voltage drop of 10.4V
across the lkO resistor at the output of ICl. This allows the op amp
to drive the ADJ terminal of the
LM3 3 7 regulator to - 17. 3 volts in
spite of the fact that the negative
supply rail to ICl is only - 14 volts.
The supply rails for ICl are provided by zener diodes D5 for the
positive line and D6 in series with
LED 1 for the negative line.
Diodes D7, DB, D9 and DlO protect the regulators from reverse
voltages which may be generated
by capacitive or inductive loads
connected across the outputs.
Drop-out indicator
When the regulators are working
as designed, the ripple voltage
superimposed on the DC rails will
be very low. However, if the current drain is higher than the
regulator can supply while still
maintaining about 2 volts between
its input and output terminals, the
ripple voltage will suddenly become
quite high. The output voltage will
fall rapidly if even more current is
called for and the ripple will go
even higher.
When this condition is beginning
to occur you may have no idea that
it is happening. You need a visible
JANUARY 1988
39
PARTS LIST
1 plastic instrument case, 205
x 159 x 68mm
1 PCB, code SC041-188, 112
x 92mm
1 . Scotchcal front panel, 1 90 x
60mm
1 meter scale display, 52 x
• 43mm
1 6672 30V, 1 A transformer
1 single-pole pushbutton mains
switch
1 DPDT mini toggle . switch
4 banana panel terminals (blue,
white, red and green)
1 5k0 potentiometer
1 knob
1 mains cord and plug
1 cord clamp grommet
2 solder lugs
1 aluminium panel, 196 x
64mm x 1.5mm
2 T0-220 insulating kits (mica
washer and bush)
1 MU45 panel meter, 0-1mA
movement
Semiconductors
1 LM31 7T positive adjustable
3-terminal regulator
1 LM337T negative adjustable
3-terminal regulator
1 TL071, LF351 FETinputop
amp
1 741 op amp
9 1N4002 or equivalent 1A
diodes
6 1N914, 1N4148 small signal
diodes
1 12V 1W zener
1 15V 1W zener
2 5mm red LEDs
Capacitors
2 2200µF 25VW PC
electrolytic
2 1 OOµF 25VW PC electrolytic
4 1µF 25VW PC electrolytic
1 0.1 µF metallised polyester
Resistors (5%, 0.25W)
1 x 2.2MO, 2 x 47k0, 1 x.39k0,
1
X
X 22k0, 3 X 2.7k0, 3 X 1k0, 1
2200, 1 X 1800, 2 X 1200
Miscellaneous
Solder, hookup wire, insulating
sleeving, screws, nuts, selftapping screws etc.
Putting it together
Close-up view showing how the 3-terminal regulators are mounted (see also
Fig.5). Use your multimeter to check that the metal tabs are isolated from
chassis.
indicator. Hence, we have designed
a drop-out indicator using IC2.
ICZ is connected as an inverting
amplifier with a gain of about 800.
It monitors both the positive and
negative regulators via 2.7k0
resistors and a O.lµF capacitor.
Diodes Dl 1 and Dl 2 limit any noise
or ripple signal level to a maximum
of ± 0.7V.
The amplified ripple at the output
of IC2 is fed to a full wave rectifier
40
SILICON CHIP
consisting of D13 to D16 via a lkO
limiting resistor, to feed a light
emitting diode, LED 2. The LED
begins to glow when the ripple at
one of the regulator outputs
becomes greater than about 4mV
peak-to-peak. At about 19mV p-p
ripple the LED is fully alight.
A lmA meter monitors the output
voltage via the lkn and 39k0
resistors. This gives it a full-scale
reading of 20 volts.
The supply is housed in a standard plastic instrument case
measuring 205 x 159 x 68mm
(Altronics Cat. No. H-0480 or
equivalent). All the circuit with the
exception of LEDs, switches and the
pot, is accommodated on a printed
circuit board measuring 112 x
92mm (coded SC041-188). Both
3-terminal regulators are bolted to
the rear metal panel of the case for
hea tsinking.
You can start assembly by checking the copper pattern of the board
for any breaks or shorts in the
tracks. Compare it with the pattern
published in this article.
With that done, you can install
all the small parts on the printed
board. These include the resistors,
diodes, links, small capacitors and
the two op amps. Make sure that
the ICs and diodes are correctly
oriented before soldering them into
place. Note that the two ICs face in
the same direction. Use the wiring
diagram of Fig. 4 to check each
stage of assembly.
Next, install the two 2500µF
capacitors and the two 3-terminal
regulators. The regulators should
be mounted so that their bodies are
about 10mm clear of the board, to
allow them to be easily bolted to the
back panel of the case.
We recommend the use of PC
pins for all external wiring from the
POWER TRANSFORMER
CLAMP
GROMMET
\
MAINS CORD
Fig.4: follow this wiring diagram carefully and your supply should work first time. Use medium-duty 24 x 0.2mm
cable for connections between the PCB and transformer, and to the output terminals and Load switch (see text).
board. They simplify connecting it
up and give easy test points when
checking voltages.
The completed printed board is
supported on four of the integral
plastic standoffs on the base of the
case and secured with self-tapping
screws. The transformer must be
mounted directly onto the base of
the case. To do this, two of the standoffs will have to be removed or
drilled out and holes drilled for
3mm roundhead or countersunk
screws. Use lockwashers under the
two nuts.
Note that the mains earth wire is
terminated to a solder lug on the
rear metal panel of the case and
thence to a solder lug secured by
one of the transformer mounting
screws. The earth wire also goes to
the green GND terminal on the front
panel.
When the printed board has been
installed, slide the metal rear panel
into the case and mark the mounINSULATING
BUSH
\
~
Ml .I
WASHER
iI
SCREW
Deburr de burrs
HEATSINK
(REAR OF CASE)
NUT
ting hole positions for the two
regulators. The mounting holes
should be drilled for 2.5mm screws.
Fig.5 shows the mounting details
for the two regulators. Note that a
mica washer and insulating bush
must be used to isolate each device
from the metal panel.
/
T0220
DEVICE
Fig.5: mounting details for the
two 3-terminal regulators.
Before securing the regulators,
make sure that the mounting holes
are free of burrs. Lightly smear
heatsink compound on the regulator
heatsink surfaces and the mating
areas on the metal panel. Then
screw the two regulators to the
panel as shown in Fig.5.
You should then switch your
multimeter to a low Ohms range
and use it to check that the metal
JANUARY 1988
41
tabs of regulators are both isolated
from the metal panel.
You can then work on the front
panel. Kitset buyers can expect
that they will be supplied with a
screen-printed precut panel but if
you're working from scratch you
will probably have to make or purchase a Scotchcal panel. The artwork can be used as a drilling
template for the front panel. The
meter is supplied with its own
template for the four mounting
screws and 46mm diameter cutout.
This latter hole can be made by
drilling a series of small holes just
inside the circumference of the
marked circle and then filing the
resulting cutout to a smooth circle.
Having drilled all the holes, you
can affix the artwork to the front
panel. The material covering the
holes is then removed using a
Stanley utility knife.
Now the front panel hardware
can be mounted. In complete kits, a
new scale should be supplied for
the meter. This is easily fitted. Just
unclip the meter bezel, undo two
screws, remove the old panel and
replace it with the new and then
reassemble. Alternatively, you can
remove the existing scale, erase the
numbering and re-do it with
Letraset.
Complete the wiring by following
What's a dual
supply?
"Wotsa dual tracking power
supply anyhow and why would I
want one?" we hear you ask, in
your ardent quest for knowledge.
The word dual refers to the fact
that this power supply has two
supply rails , one positive and the
other negative. The word tracking refers to the fact that when
you adjust the positive supply,
the negative supply automatically
follows so that it has the same absolute value. So if you set the
positive output to plus 1 0 volts
DC, the negative rail will be very
close to minus 10 volts.
That's what you'd expect, isn't
it?
Fig.4. Connecting wires to the
potentiometer, the two LEDs and
the meter can be light-duty hook-up
wire but the remaining wiring
should use heavier wire, such as 24
x 0.2mm insulated cable.
The 3-core mains cable should
have its outer insulation layer
removed for a length of about 10cm
so that the active lead can reach
the mains switch on the front panel.
The mains cord can then be
secured to the rear panel using a
cord-grip grommet.
The neutral lead is terminated
directly at the transformer, as is
the other lead from the mains
switch. Both the mains termination
on the transformer and the mains
switch itself should be sleeved with
plastic tubing to avoid the possibility of accidental shock.
When all the wiring is complete
you should check your work
carefully against Fig.4 and Fig.2
(the circuit diagram}. With that
done, you can apply power and
check the voltages. The
unregulated voltages to the input of
the two regulators should be about
± 21 volts, while supplies to the two
op amps should be + 15V at pin 7
and - 14V at pin 4.
Now check that the positive and
negative supply rails can be varied
over the range from below 1.5V to
above 18V and that the two supplies track each other within
± lOOmV.
The dropout indicator can be
checked for correct operation by
connecting a 220 resistor across
either the positive or negative supply. Now, when the output voltage is
wound up above 15 volts, the LED
should light.
All that remains is to secure the
lid of the case and your power supply is ready for work.
lb
~
_, _
.i.
CLASS-2.5
•
MU -45
•
Fig.7: this full-size artwork should
be used to replace the existing
meter scale. The old artwork is
removed by unclipping the meter
bezel and undoing two small
screws.
Fig.6 (left): this full-size
reproduction of the PC pattern can
be copied and used to etch your
own PC board.
42
SILICON CHIP
BOOKSHELF
Comprehensive text
on power supplies
Switching and Linear Power Supply, Power Converter Design, by
Abraham I. Pressman. Published
1977 by Hayden Book Co, Inc,
Hasbrouck Heights, NJ. Hard
covers, 160 x 235mm, 372 pages
ISBN O 8104 5847 0.
These days switching power supplies are becoming ever more
widespread throughout electronics
as efficiency, compactness and low
heat dissipation become more
desirable. For this reason alone the
book is of considerable interest but
it would be a mistake to regard it as
just on switching power supplies.
As the title suggests, there are also
major portions devoted to the
design of linear power supplies and
power cqnverters.
A brief explanation of these
terms is in order before going on to
review this text. Switching power
supplies vary and maintain their
output by rapidly switching on and
off their main control element
which these days is a high power
transistor or transistors.
A linear power supply is one in
which the output voltage is varied
or maintained by continuously adjusting the main control element
which again is a power transistor
or group of transistors. Lastly,
power converters are circuits
which step up or down from a DC
input voltage to provide one or more
DC outputs. They usually consist of
a high frequency transformer
driven by switching transistors.
And now to our review: as far as
the subject matter is concerned,
this book is old. Published in 1977
and possibly written a year or two
before that, it naturally misses out
on all the developments in power
supplies and electronics generally,
that have taken place in the last
twelve years or so.
That means that such things as
3-terminal regulators, gate turn-off
thyristors, power Mosfets, CMOS
logic circuits and Fet-input op amps
don't get a mention. Nor is there
any discussion at all on power control using silicon controlled rectifiers (SCRs) or Triacs and hardly a
mention of 3-phase circuits.
Be that as it may, it is still a very
worthwhile book, now in its seventh
printing. I would regard it as one of
the best overall texts on the subject
of power supply design that I have
come across.
There are nine chapters in all,
starting with a chapter on basic
voltage regulators and power converters. This has a good section on
the design of zener diode and emitter follower regulators. An
understanding of this topic is essential to anyone involved in power
supply design.
Chapter two is basic square
wave power converters and
regulators while chapter three is on
compound regulators.
Chapter four is an excellent
dissertation on the subject of thermal design which is applicable to
power amplifier design as well as
power supplies. It discusses forced
air cooling too.
Chapter five is another on fundamentals, this time on rectifier
design using capacitive filters. This
also contains a useful section on
voltage multipliers, using diodes
and filter capacitors.
Chapter six goes into the nitty-
gritty on series pass regulators and
includes sections on foldback current protection and crowbar overvoltage protection.
Chapter seven is on integrated
circuit voltage regulators, mainly
on the Fairchild µA723 although the
National Semiconductor LM105
and Motorola MC1560/1561 are
also covered.
Finally, chapter eight covers
DC/DC converters while chapter
nine covers switching regulators,
both in considerable detail.
In summary, it's an oldie but a
goodie. Our copy came from Jaycar
Electronics.
Active filter design
Active Filter Design, by Carson
Chen. Published 1982 by the
Hayden Book Co, Inc, Hasbrouck
Heights, NJ. Soft covers, 152 x
228mm, 133 pages. ISBN O 8104
0959 3.
This small text is aimed at the
engineer who wants a quick
reference on the subject of active
filters. It makes con$iderable use of
mathematics to support the text,
particularly S-parameters.
There are essentially six
chapters, as follows: (1) Transfer
Functions, Decibels and the Quality
Factor; (2) Magnitude, Phase, Poles
and Zeros; (3) Some Basic Transfer
Functions; (4) Basic Filter
Topologies; (5) Mathematical Approximations: Butterworth,
Chebychev, Elliptic and Bessel; (6)
Cascading, Normalisation, Frequency Transformation and Impedance Scaling.
It is by no means an easy text to
read. For example, the sections on
poles, zeros, normalisation and impedance scaling are unlikely to be
understood by anyone who has not
previously come up against these
concepts.
In summary then, it is OK for the
engineer or engineering student but
anybody else can probably forget it.
Out copy came from the publisher.
JANUARY 1988
43
••
-
·
•. •
- ·.
-· • • •
- ·
• •
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Ref: Silicon Chip Jan '88
Ref: Silicon Chip Jan '88
WCAR
New generation door opener
WCAR
Usten tD hidden transmissions on FM broadcasts.
alarm.
WCAR
PC board and components.
Cat. KC-5020
WCAR
Cat. KC•5014
WCAR
SUB CARRIER ADAPTORS
FOR FM TUNERS
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ANNUNCIATO
$37.50
$22.95
9V power supply
Cat. MP-3010 $18.50
1.25 tD 18.5V DC, voltage metering.
LED dropout !ndlcatDr, short
circuit protected. Full kit.
Cat. KC-5022
DUAL TRACKING
POWER SUPPLY
ULTIMATE CAR
BURGLAR ALARM
Ref: Sllcon Chip Jan '88
Includes flashing light
switch, back-up battety
factllty and lgnltlon killer.
Cat. KC-5021
$79.50
••
$99.95
• • • • ,.
'
~ ,· ·~· ·., ·•. .>: ,._· •..:. ✓,,...
4.,
-
50 & 100 WATT
AMPLIFIER
MODULES
Extras · Siren Hom
Cat. LA.·5700 $26.50
Screamer Plezo
Cat. LA-5255 $17.95
Back-up batlety
Cat. SB-2480 $22.50
Ref: Silicon Chip
lf you are tired of
phone, tty this kl
phone · Includes
Cat. KC-5015
$19.9
:~g:~ : :i,: :,l " - - - - - - - - - - - - - - - - - - - - - - - - - - - -41111
Ref: Silicon Chip Dec '87
Kits Include PCB all parts
and heat stnk bracket.
O'hermtstors not supplied).
SOWA'IT
Cat. KC-5018
$32.95
ThermtstDr RDE115
Cat. RN-3415
$8.95
lOOWATI
Cat. KC-5019
$38.95
ThermtstDr RDE245A
Cat. RN-3418
$10.95
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12" GUITAR SPEAKER
8" WHITE CONE
WOOFER
NEW MODEL
Finally available, our updated guitar speaker with
extended frequency response. Especially suited for
not only Bass guitar buy Rythm & Lead as well.
Specifications
Resonant Frequency
60Hz (was 80Hz)
Impedance
8 ohms
Freq. Response
60 • 5000Hz (was 80 · 4000)
Power Handling
100 watts RMS
Magnet Weight
40 oz
Net Weight
3610 grams (was 3520g)
Sensitivity
102dB
But the best news 1s the prtce • NO INCREASE
Cal CG-2380
STILL ONLY $89.50 LESS 15% $76.07
Best looking and
sounding 8" woofer
we've seen for the
prtce. White cone,
large magnet 10oz,
roll surround.
Spees
Power Handling .
Resonant Freq.
FIreq.dResponse
mpe ance
Sensitivity
MOTOROLA Model KSN 1038
Over 100 watts rms, frequency 4·30kHz.
No crossover required. Especially suited to H1 Fi.
Cat. CT-1914
ONLY $26.95 · ·
·-.· .:·· ·
MOTOROLA Model KSN
1016
50x 125mm
This exponential horn has a full 90"
hortzontal dispersion angle. With harmonic
distortion of less than 1%, this unit is Ideal
for HI Fi use. Frequency response 3 • 30kHz
±3dB, maximum input 25V rms,
no crossover required.
Cal CT-2026
•
MOTOROLA
Model KSN 1135
NEW MODEL
Same to look at as Model 1005A (CT-1910)
but handles 75 watts. SPL 96dB.
Cal CT-1908
ONLY $14.95
LESS 15% $12.70
60 x 150mm Rectangular
Widest frequency range of the plezo horns,
otherwise similar to the CT-2026.
No crossover required.
Cat. CT-1912
WAS $34.50
NOW $29.95 LESS 15% $25.46
SAVE $9.04
HE ORIGINAL ADEL NIBBLING TOOL
BACK AGAIN
.E/G68
MOTOROLA
~
Model KSN 1089A
NEW MODEL
MOTOROLA Model KSN 1025A
ONLY $29.95
LESS 15% $25.46
·..
• ·•
WAS $26.50
NOW $22.95
LESS 15% $19.50
WAS $26.50
NOW $19.95 LESS 15%. $16.96
SAVE $9.54
BORN IN THE USA
How things change. You can now
purchase from Jaycar the ortgtnal
Amertcan Adel nibbling tool. Due to
prtce rtses from Asian countrtes we've
been bale to direct Import the ot1g1nal
tool (which we sold 10 years ago) and
sell It at the same prtcc as the Asian copy.
• Cuts holes · any shape over 7 / 16''
• Notches clearance for plugs and w1I1ng
• Trtms underslze holes to flt parts
• Suitable for steel up to 18 gauge,
Aluminium 16 gauge, plastic and copper
Cat. TH-1765
1
5 up $24.50 LESS 15% $20.82
Why buy a Taiwanese P!ezo Tweeter
when Jaycar can offer you the best for no more.
MOTOROLA Model 1005A
· • · ..•
,
·•
LESS 15% $22.90
GENUINE MOTOROLA PIEZO
TWEETERS AT TAIWANESE PRICE
90mm SUPER HORN
Perfect for use where Jong throw Is needed.
PA's and musical instrument use. Frequency
response 3.8-28kHz ±3dB, maximum Input
25V rms ( IO0W amp power), no crossover required.
Cat. CT-1910
8
96dB
.,
1
;:;;{{
5 or more $79.50 LESS 15% $67.58
WAS $24.00
NOW $18.95 LESS 15% $16.10
SAVE $7.90
_.
ohms
3." Direct Radiating Tweeter
Looks like a normal 3" cone tweeter. Great
for car sound and H1 Fi.
Cal CT-1906
ONLY $9.95
LESS 15% $8.46
••••••••••••••••••••••••••••••••
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These are basically a 5mm LED mounted tn
.232••
+
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a plastic housing spectftcally designed for
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mounting.
Available
In
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4
standard
colours.
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Green
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12.54mm)
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Jaycar has Introduced this great LED array
JAYCAR
for our 1988 new product line-up. It has 7
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green
and 3 red rectangular 5mm x 2.5mm
10
up
$1.30
ea
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LEDs mounted In a black housing. Ideal for
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Cat. ZD-1702
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DIRECT IMPORT SAVES YOU MONEY
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(ALLRED)
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WAS
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The STD Bar for your telephone will be available
200mCd
Cat. ZD-1790
99t
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sometime In Janua,y. It appeared In our
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catalogue but we were afraid to
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10
up
70<:
Less
15%
release
It due to to the safety
10up90t
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aspect of 000 emergency
N EW"'f-sS
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Cat. ZD-1792
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$3.75
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number. We have solved
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LESS 15% $2.12
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this problem, and the new
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I
DIRECT IMPORT
SAVES YOU MONEY
ALL THE SAME PRICE
48~ ea LESS 15% 41~
U
~ 1t1
-iL,,u
WAS $1.95 ea
NOW $1.50 ea
LESS 15% $1.28
LOWER PRICES ON
ULTRA BRIGHT LEDS
$4.25 LESS 15% $3.61
STD BAR - FINALLY RELEASED
rl1fl
$34.95 LESS
15% $29.70
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BISHOP GRAPHICS - LESS 15% OFF ALL PRICES
As demand for greater PCB density Increases so does the need for a more professional approach to PCB design. To help In this regard, Jaycar stocks a comprehensive range
of PCB artwork materials from BISHOP GRAPHICS of the USA. This material Is both dimensionally stable and accurate which, enables you to produce complex layouts with
greater accuracy. (Vexy necessaty for LSI, for example). Once your artwork has been produced you can make your own board.
111111
PRE-SPACED
HG-9906 0.100" d!aPADS
1.58mm 240 pads $5.60
HG-99070.100" dla 1.91mm 140pads $5.60
HG-9908 0.156" dia 2.54mm 150 pad $5.60
PRESSURE SENSITIVE COPPER TAPE
OOOOO0
DIL PATTERNS
HG-990914 PIN 32 symbols
HG-9910 16 PIN 32 symbols
HG-9911 18 PIN 28 symbols
HG-9912 24 PIN 12 symbols
HG-9913 28 PIN 12 symbols
HG-991440 PIN 8 symbols
$5.60
$5.60
$5.60 .
$5.60
$5.60
$5.60
DIL PATTERNS · NARROW CUT
HG-9918 14 PIN 32 symbols
HG-9919 16 PIN 32 symbols
HG-9920 40 PIN 8 symbols
$5.60
$5.60
$5.60
BLACK AR1WORK TAPE
HG-9930 0.026" wide
HG-99310.031" wide
HG-9932 0.040" wide
HG-9933 0.050" wide
HG -9934 0.062" wide
HG-9935 0.080" wide
HG-9936 0.093" wide
HG-9937 0. 100" wide
HG-9938 0 . 125" wide
HG-9939 0.200" wide
HG-9940 0.250" wide
x 20 yards
x 20yards
x 20 yards
x 20 yards
x 20 yards
x 20 yards
x 20 yards
x 20 yards
x 20 yards
x 20 yards
x 20 yards
$3.95
$4.25
$4 .25
$4.25
$4.30
$4.30
$4.30
$4.30
$4.30
$4.30
$5.75
0.031" ID
0.031" ID
0.031" ID
0.031" ID
0.031" ID
0.031" ID
$4.30
$4.30
$4.30
$4.30
$4.30
$4.30
DONUT PADS
HG-99410.080"
HG-9942 0.100'
HG-9944 0.125"
HG-99450.156''
HG-9947 0.200'
HG-9948 0.250"
OD x
OD x
OD x
OD x
OD x
OD x
AR1WORK ACCESSORIES
HG-9955X-Acto knife
HG-9956 5 trim pack blades
HG-9957 5 art pack blades
$4.65
$3.95
$3.95
•
•
•
•
1111111
1111111
IIIIIII
IIIIIII
-i,8
•
Ideal for repairing damaged or broken
semiconductor traces on a PCB.
Use to modify circuitry on existing PCB's.
HG-9901 0.031" wide x 6ft
HG-9902 0.050'' wide x 6ft
HG-9903 0.100' wide x 6ft
<;:,>.'())
~
$4.30
$4.30
$5.35
AR1WORK FILMS POLYESTER
Always use a background grtd during printed
circuit artwork and layout preparation to
ensure maximum accuracy on the final PCB.
10 x 10 grtd, matt on one side - 0.003" thick.
This Is the material you lay your pattern on.
HG-9959 8.5 x 11" pack of2
HG-9960 I I x 17' pack of 2
$4.25
$7.50
ULTRAVIOLET EPROM ERASER
If you need to regularly erase the contents ofEPROM's then this Is
your most cost-effective solution. It will erase up to 9 x 24 pin devices
In complete safety to your eyes and your chips, In around 40 minutes
for 9 chips Oess for less chips).
• Erase up to 9 chips at a time
• Chip drawer has conductive
foam pad
• Mains powered
• High UV Intensity at chip surface
ensures thorough erase
• Engineered to prevent UV exposure
• Long UV tube life
Specifications
240V50Hz
Operating Voltage
8 watts
Power Consumption
Cat. XE-4950
9 to 24 pins
Capacity
UV Source Wavelength
253.7nm
6.4mW/cm'
UV Intensity
3000hours
Tube Life
21.7 X 8 X 6.8cm
Dimensions
Weight
670grams
$99.50
LESS 15%
$84.58
--~;filiiil:l!ll!iliiii!!!!!!!!!!'!!!!!!!l!!!I!!!!!!!!!!!!!!!!!~~----------_::======================::..,,
~fflt::;r
JAYCAR ·JAYCAR
JAYCARJAYCARJAYCARJAYCARJ AYCAR JAYCARJAYCAR JAYCARJ AYCARJAYCARJAYCAR JAYCAR JAYCARJ AYCAR JAYCAR JAYCAR JAYCA RJ AYCAR JAYCARJAYC AR JAYCARJA Yl
JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JA '✓'
JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JA-.
24 TO 12V CONVERTER
Ref: Silicon Chip Dec '87
Well suited to nm 12 volt
appliances from 24 volt.
Can deliver up to 5 amps.
Complete kit
Cat. KC-5017
$59.00 LESS 15% $50.15
We have managed to purchase a second batch.
They are slightly more expensive but st111 represent an absolute_bargain.
You guessed It, another Jaycar buy far, far below manufacturers cost where
you buy at a normally sllly prlce because other people have lost heavily.
This time Its a VERY HIGH QUALITY cassette deck mechanism that cost over
$35 US tn 1000 lots! This JAPANESE MADE mechanism Is deck only - I.e. a
door Is not fitted nor are there buttons. The deck Is not operated by
mechanical buttons and all control ls by electric signals, therefore the deck
could easily be software con trolled.
The deck also features an air damper cylinder for soft eject, massive capstan
flywheel, HI FI head and excellent specs. (see below) .
This deck Is Ideal as either a fast high capacity PC memory storage or as a
retrofit lo an existing cassette deck to Improve performance.
Worth at least $80, grab one for ONLY
SOLAR GENERATOR
Ref: ETI Dec '87
This Is a cheap, no fuss way to
trickle charge a 12V car battery.
PC board and parts.
Cat, KE-4730
$12.95 LESS 15% $11.00
HIGH IMPEDANCE AC/DC
MILLIVOLTMETER
$29.95 LESS 15% ONLY $25.45
Ref: EA Dec '87
This kit will measure AC and DC signals
down to a couple ofmllllvolts, with negligible
circuit loading. Complete kit with case and meter.
Cat. KA-1695
Cat. AC-1590
SPECS:
• 4 track, 2 channel Phillps compact cassette deck
• Tape speed 4. 75cm/sec
• Wow and flutter <0.12% RMS
• Wtndlng time 110 sec FF & REW C-60
• Working volts 9 - 15V
• Supplied with 12 page comprehensive manual lnclucllng circuit diagram,
truth table, etc.
$46.50 LESS 15% $39.53
UNIVERSAL SPEED CONTROL
& LAMP DIMMER
Ref: Silicon Chip Dec '87
Use for control of dnlls, fans, electric blankets,
soldering Irons or a dimmer. Complete kit with
box, matns leads, etc.
Cat. KC-5016
$18.95 LESS 15% $16.11
JAVCAR
No1 FOR
KITS
OCTAVE EQUALISER MODULE
Ref: AEM Dec '87
This one octave EQ module Is suited for PA and professional use. Klt supplied with
all components, pots, PCB. No box or hardware.
Cat. KM- 3064 .
$49.95 LESS 150/o $42.46
TURN YOUR SURPLUS
STOCK INTO CASHII
Jaycar will purchase your surplus
stocks of components and
equipment. We are conttnually on
the lookout for sources of prlme
quality merchandise.
CALL GARY JOHNSTON OR
BRUCE ROUTLEY NOW ON
(02) 747 2022
Build this superb
1GHz Digital
Frequency Meter
This month, we complete construction
of the 1GHz DFM and describe the
calibration procedure. There's also a
useful troubleshooting guide - just in
case you strike trouble.
By STEVE PAYOR
Last month, we left off after
describing the assembly of the two
main printed circuit boards. The
next step is to solder the two boards
together at right angles.
To so this, carefully align the two
boards, using the arrows at each
end of the display PCB as a guide,
and solder tack them in several
places. Now inspect the assembly
carefully and make any adjustments that may be necessary.
When everything ls correct, solder
all the matching pads together to
create a permanent assembly.
Finally, check that there are no
solder bridges between adjacent
pads. The meter is now ready for its
first test.
Temporarily install an insulated
This close up view shows the mounting details for the two BNC sockets. Note
that two earth links are soldered to the 500 input socket.
48
SILICON CHIP
link across the switch connections
to the mains terminal block (the
mains switch is installed later),
then slot the counter module into
the front of the case. Connect the
power supply leads to the board
with a multimeter set to measure
DC current in the + 5V lead. Plug
in, switch on and verify that the
current is between 300 and 500mA
(depending on how many digits are
lit).
If all is well, try pressing the
front panel buttons. On power up,
the display should read .000kHz
and the second Function LED
should be lit (frequency to 10MHz).
When the Range buttons are pressed, the leading zero on the display
should be directly above the
selected button, and the decimal
point should be immediately to the
left or right of the leading zero,
depending on the setting of the
Function pushbuttons.
The function indicator LEDs and
the µsec and kHz light bars should
change with the Function
pushbuttons.
If you strike problems here,
switch off immediately and check
for wiring errors.
Assuming the power consumption of the counter module is within
the specified limits, you can now go
ahead and make the + 5V supply
permanent. Twist the supply leads
together and trim them so that they
are just long enough to reach the
counter PCB.
The µsec and kHz transparencies
can now be glued to the light bars.
Use only water-based PVA glue (eg,
Selleys "Aquadhere"). Only a tiny
bead around the outside edge is re-
, Se
12,8
1·.
Above: the new 1GHz DFM is shown
here displaying the frequency
generated by the SAB6456 prescaler
IC (see text).
quired. If you make a mess, clean
up with a damp cotton bud and try
again.
Testing the counter module
The counter module should rest
comfortably in the second PCB slot
from the front, leaving a 10mm
clearance between the display PCB
and the front panel. At this stage,
you will find that the lkO multiturn
trimpot will be resting on one of the
PCB guide rails, so carefully cut
away the plastic at that point.
Do not drill a hole right through
the plastic case, as this trimpot is
not meant to be adjusted from the
outside.
With the counter module and
rear panel module in place, slip on
the top half of the case, then turn
the whole unit upside down. The
bottom half of the case can now be
removed to expose the underside of
the counter and display PCBs.
Next, solder a shorting link
across the lMO input pads on the
display PCB and plug a 1. 7V red
LED into the Molex pins at the test
point. The anode of the LED should
be connected to the + 5V track,
which is the thicker of the two.
Switch on - with no signal input,
the LED will either be on or off,
depending on the state of the
Schmitt trigger (IC2a).
If the LED is off, turn VRl
1,28
,128
QUENCV METER
Hints on Drilling the Perspex Panel
The greatest hazard when drilling thin perspex sheet is the
possibility that the drill will take one
bite and shatter the panel.
To avoid this problem, the drill
should be as sharp as possible, for
a clean finish, but the cutting edge
should have no rake . Specifically ,
the leading edge should be at 90 °
to the cutting direction as shown
below. It only takes a minute to
convert a normal drill bit, using a
grinder or pocket stone.
The other problem often encountered is a poor finish, caused
by the drill overheating and melting
the surrounding plastic. Again,
keep the drill sharp.
There are two other styles of drill
grinding which are useful when
building a project like this. The Wshaped bit is for cutting clean,
perfectly round holes in sheet
metal. This drill actually punches
out a thin disc at the end of the cut,
leaving no burr on the far side. It is
perfect for drilling ventilation holes
in aluminium or thin sheet steel and
will even cut a clean 1 2mm hole in
clockwise until it just comes on, or
vice versa. Tapping VRl with a
metal screwdriver will inject
enough noise to trip the Schmitt
trigger, so keep the blade in steady
contact (or use a plastic
screwdriver).
NORMAL
DRILL
FOR
SHEET
PERSPEX
METAL
SPOTFACING
tinplate. Using a normal drill for this
job would leave you with a mess.
The spotfacing drill is similar, but
the "wings" are straight instead of
W-shaped, and less rake is used
on the leading edge. This type of
drill will soon get rid of any unwanted plastic pillars, cutting them
flush with the inside of the case.
Having found one of the trip
points, slowly turn VRl in the opposite direction, half a turn at a
time, counting as you go. When the
Schmitt trigger changes state
again, you have found the other
trigger point. On the prototype, the
JANUARY 1988
49
The 100MHz preamplifier circuitry is adjusted with a 1. 7V red LED plugged into two Molex pins on the back of the
display PCB.
range was five full turns. This is a
convenient way of checking the DC
gain of the amplifier circuitry each turn is approximately lmV.
Check the trip points once more,
then set VRl exactly half-way between them for maximum
sensitivity.
Once VRl has been set, remove
the input short and the LED. Slip on
the bottom of the case and turn the
instrument right way up again. The
instrument is now ready for its first
frequency measurement.
Select a lMQ resistor and clip
one lead short. Switch on and touch
this lead to the 0.047 µ,F input
capacitor while holding the other
lead in your fingers. The DFM
should show a steady reading of
.050kHz. Note: the lMQ resistor, in
conjunction with the input
capacitance, acts as a low-pass
filter for the 50Hz signal picked up
by your body capacitance from the
mains wiring.
The 7 10 prescaler can now be
checked by pressing the F3 button.
The display should change to
0.05kHz (ls gating time].
Now switch to period mode. You
should get a fluctuating reading of
around 20,000µ,s (20ms). The
reading will be constantly changing
because the short-term stability of
the mains is nowhere near as good
as that of the crystal. Removing the
signal source in Period mode will
freeze the reading since the 7216A
counter chip will be waiting for the
required number of input cycles to
50
SILICON CHIP
be completed before it updates the
display.
Checking the 1GHz range is easy.
Press the F4 button and select the
minimum gating time (R4). You
should now have a rapidly updating
reading of around 1.2GHz. This is
because the SAB6456 prescaler
oscillates at this frequency when no
signal is present. Now press the R2
button and wait 12 .8 seconds until
the display updates. The leading
"1" will now be in the overflow
position, with the rest of the digits
much the same as before.
The above procedure checks out
virtually all of the functions of the
DFM. If your unit passes all the
above tests, you can be sure it's fully operational.
The front panel
The front panel artwork shows
the drilling pattern for the panel.
Red perspex is the material of
choice and the colour to ask for is
"Red 502". This is a deep ruby red
colour which looks quite dark but
transmits the wavelength of the red
LEDs extremely well.
The thickness of the panel should
be 2mm, with 1.6mm as the second
choice. Unfortunately, these
thicknesses are not universally
available, although 3mm sheet is
quite common and can be pressed
into service if you have no other
choice.
The 3mm sheet will fit in the wide
gap between the front panel slot
and the first PCB slot. The PCB
should be moved to the third rearmost slot (don't forget to cut the
relief for VRl ). Provided none of the
components are higher than the
height of the 7-segment displays,
everything will still fit.
If you go for this option, note that
you will have to trim an extra 1mm
from the top and bottom of the
panel. The width remains the same.
Once the panel has been cut to
size, the holes can be drilled to accept the switches and input sockets.
This can be done by first taping the
front panel artwork (or a copy) to
the panel, then marking out the
holes with a sharp scriber. Pilot
drill all holes with a small PCB drill
to start with, then progressively
enlarge the holes, checking the centring as you go .
The final hole sizes are 9.5mm
for the BNC sockets and 10-1 lmm
for the pushbutton switches. You
1.0~--~~--~~--~
0.9
0.8
I·e o.,
i
0.6
TIME (mi nutes from switch-on)
Fig.12: this graph plots the warm-up
drift of one of the prototypes. The
total drift is better than 1ppm.
POWER
•
cycles counted 1000
gating time, sec 10
10
128
100
1
1
12.8
10
.1
.1
1.28
1
.01
.01
.128
I
10MHz 100MHz 1GHz
PER~ENCl
1Mn/10pF
\llfl
\llfl 50n
DIGITAL FREQUENCY METER
0
C041-1187
Here are actual size artworks for the front panel, printed circuit boards, and
kHz and µ,sec indicators.
may wish to ream the last mm or so
of the pushbutton holes, particularly if the drill is not cutting evenly.
Drilling thin Perspex is not an easy
task, so we have included a panel
on hints for drill sharpening for
those readers who are not used to
working with this material.
Because the inside edges of the
pushbutton holes are visible, you
may wish to polish them. Alter-
natively, blacken them with a marking pen.
Front panel assembly
Affix the Scotchcal label to the
front panel, then cut out the three
holes for the power switch and input sockets using a sharp utility
knife. A light touch with a reamer
will improve the appearance of the
hole for the mains switch.
I!&
JANUARY 1988
51
Troubleshooting the 1GHz DFM
Don't rush out and replace all the
semiconductors if the counter
module fails to work first go. The
problem is almost certain to lie
elsewhere unless you've done
something silly, such as installing
an IC or transistor back to front.
The first thing to check is that all
the parts are in their correct
positions and are correctly
oriented. For example, the
switches will not work if they are
rotated 90 °.
Next, check the copper side of
the PCBs for soldering faults, such
as bridges between the closelyspaced tracks around the IC pads.
Another thing to look for is open
circuit tracks, and these are most
likely to occur where too large a
hole has been drilled through an IC
pad.
One area where soldering faults
are both common and easily
detected is in the multiplexed
display. A short between
segments is easily recognised
from its effect on the display, as is
an open circuit along one of the
segment tracks.
Some constructors of previous
Mount the two BNC sockets and
orient them so that the solder tags
will fit between the parts on the
display PCB. The 500 input socket
should ,have its tag at 3 o'clock
(viewed from the back), while the
other tag should be between 7 and 8
o'clock. Bend the tags up by 90°
after the nuts are tightened.
Next, solder two short lengths of
tinned copper wire to the 500
socket and one to the lMO socket
(the two connections to the 500
socket minimise the series inductance). This done, solder two short
lengths of tinned copper wire into
the central hollow pins of the
connectors.
Remove the counter module from
the case and test the fit of the front
panel over the switches. Bend the
earth links from the BNC sockets to
engage the PCB holes, then slide the
module and panel together into the
case. The leads from the input
sockets can now be soldered to the
52
SILICON CHIP
DFM projects have experienced
trouble in getting the 7216A's
oscillator to start up. The
symptoms are no display at all, or
only one digit lit and very briefly at
that. The problem usually occurs
with very cheap crystals which
have a large equivalent series
resistance.
Calculations based on the
minimum guaranteed gain of the
CMOS inverter show that the
oscillator will only work with a
crystal having a series resistance
of less than 800 and 20pF shunt
capacitance, or 350 and 30pF
nominal shunt capacitance.
If you are unlucky enough to
have a crystal with excessive
series resistance, the cure is fairly
simple: use less capacitance to
the +5V rail at pins 25 and 26 and
maintain the correct shunt
capacitance by installing a
capacitor across the crystal.
For example, removing the 39pF
capacitor and 40pF trimmer leaves
the crystal with a shunt
capacitance of about 3pF, so
adding a 27pF capacitor between
pins 25 and 26 will bring a 30pF
crystal back to the correct
frequency. The circuit will now
tolerate a series resistance as high
as 1200 although the stability will
no longer be quite as good.
display PCB.
Finally, the wiring between the
mains switch and the terminal
block can be installed. Be sure to
use mains-rated cable for this job,
and cover the switch terminals with
spaghetti insulation or heatshrink
tubing to prevent accidental electric shock. For good measure, we
also covered the entire switch body
and part of the leads with additional heatshrink tubing.
Don't forget to remove the link installed across the terminal block in
place of the mains switch earlier
on.
sharpening). This will quickly cut
the pillar right down flush with the
surrounding plastic.
We drilled four rows of holes in
the front left-hand area of the case
bottom, and another two rows on
the other side of the ribbed section.
The ribbed section was left undrilled (see photos pages 39 and 43,
November 1987). This allows cool
air to flow up under the main
counter chip and around the
10MHz crystal.
A small hole must also be drilled
in the lid of the case, directly above
the 40pF trimmer capacitor. This
hole allows external adjustment of
the trimmer during calibration. It is
located 26mm back from the rearmost PCB guide rail, and 47mm in
from the inside edge of the case
(note: if the display PCB occupies
the third PCB slot, read 29mm instead of 26mm). Drill a small hole
first, then ream it out to accept one
of those little plastic plugs that
Ventilation
It is important to ventilate the
case correctly if you want the best
possible frequency stability.
Before drilling the bottom of the
case, you will have to remove some
of the plastic pillars that are in the
way. This is best done with a spotfacing drill (see panel on drill
Signal tracing
A pair of headphones and a
multimeter are the best de-bugging
aids you can have for this project.
Assuming the 1 0MHz oscillator
is running , the 7216A should be
putting out 500Hz signals on the
digit and segment driver lines. You
can verify this with the headphones. Use a 1k0-1 OkO resistor
as a probe (to avoid loading the circuit and to protect the headphones), and listen to one of the
digit driver outputs. A "spiky"
500Hz tone should be instantly
recognisable, and all the digit
drivers should sound the same.
The segment drivers will have
the same pitch but a different timbre as the numbers on the display
change.
Check that a similar 500Hz
signal is also reaching the clock inputs of the 4024 and the 401 7s.
As a matter of interest, follow the
signal through the 4024 binary
divider's seven stages . The
7 .8125Hz signal (at the output of
the sixth stage) will sound like a
series of fast clicks.
To check the passage of the
500Hz signals through any of the
4016 analog switches , connect
the headphones across the
switch, using two resistors as probes. It is easy to tell when a particular analog switch is closed - it
should be almost silent when its
corresponding controlling Range
or Function button is pressed.
Faults in the signal path selection logic can be quickly tracked
down using DC voltage
measurements. The logic levels at
the ECL gates are described in the
panel on ECL logic but note that
some of the DC control inputs
have a logic O level less than
+3.4V which is OK since any
voltage between +3 .4V and
ground will do for a "O" input.
You can use headphones to
trace a 50Hz test signal through
the ECL preamplifier, Schmitt trigger, and the +5 and +2 counters
(but see note below) .
cover the screws on 240V wall
outlets.
Finally, fit four rubber feet to the
bottom of the case. Construction in
now complete.
Calibration
Before attempting calibration,
you should allow a warm-up time of
at least 15 minutes with the lid on.
This will give the instrument time to
stabilise and will ensure the best
possible accuracy.
To properly calibrate the instrument you will need a signal source
of known frequency, with a stability
better than one part per million. For
most of us, this boils down to one of
two choices: either local colour TV
transmissions or the 10MHz standard transmissions from WWV Colorado or WWH Hawaii.
The latter is preferred by the
author because it has the same frequency as the crystal oscillator. All
you need is a domestic shortwave
The logic levels throughout the
ECL signal path will be +4.3V
(high) and +3.4V (low) , and the
first two differential amplifiers will
be biased in between at +3.8V. A
special note of caution here: any
external connection to the signal
path will make the 100MHz
preamplifier oscillate. This is why
we chose to use a LED to monitor
the Schmitt trigger output during
the setting up procedure.
You can minimise your chances
of disturbing the circuitry by using
a resistor as a probe for your
multimeter. A value of
1 Ok0-1 OOkO is suitable for 1 OMO
digital or FET analog multimeters,
however you must cut the "probing" end quite short. Even a centimetre of lead will upset the sensitive wideband circuitry.
If you are using a low-resistance
multimeter, switch to a low voltage
range and choose a resistor which
wil l provide a convenient
"multiplier" for the reading. The
resistor acts as a low-pass filter,
preventing feedback between the
multimeter leads and the ECL circuitry at high frequencies .
receiver and seven metres of
hookup wire as an antenna. Wait
until evening, when the ionosphere
over the Pacific Ocean will reflect a
fairly good signal, and position the
DFM near the antenna so that its
radiated 10MHz clock signal is
about the same strength as the incoming signal. Adjust the 40pF
trimmer with a plastic screwdriver
until you have a zero beat.
If the shortwave receiver has a
tuning meter, you can watch the
-beats when the frequency is too low
to be audible. Adjustment to within
1Hz is often possible.
Most colour TV transmissions
are synchronised to atomic clock
standards and the 4.43361875MHz
colour subcarrier oscillator in your
TV receiver is phase-locked to these
transmissions. The easiest place to
gain access to this signal is right at
the 4.43MHz crystal. Use a probe
made from a 10MO resistor shunted
by a small capacitor of between
lpF and 3.3pF, depending on the
capacitance of the shielded cable
you are using.
You can tell whether the subcarrier frequency has been disturbed
or not by keeping an eye on the colours in the picture.
The 15.625kHz line scanning frequency is also derived from the
same accurate standard and you
may be able to pick this up from the
stray radiation around the line output stage, without making an actual
connection to the TV. Unfortunately, there are less digits to play with
in this case so, to obtain the highest
accuracy, switch to Period mode
and adjust the trimmer for a
reading of 64.0000µsec.
If you decide not to calibrate the
instrument, just set the 40pF
capacitor to about 10% less than
full mesh. This places a nominal
20pF across the crystal and the frequency will be within 10 or 20ppm,
depending on the crystal tolerance.
Note: some 10MHz crystals will
require a nominal shunt
capacitance of 30pF. You can easily tell if this is the case because you
will not get a zero beat, even with
the 40pF trimmer fully meshed. The
cure is to add some additional
capacitance across the trimmer
and the existing 39pF capacitor. A
pair of 15pF or 18pF capacitors
should be sufficient. These are best
soldered to the underside of the
PCB with very short leads.
If this still doesn't trim the
crystal to the correct frequency,
then you may have been supplied
with a series-resonant crystal by
mistake.
All capacitors used around the
crystal oscillator should be high
quality types; eg, polystyrene or
Philips NPO miniature ceramic
plate.
Fig.12 shows the warm-up drift
of one of the prototypes which used
a cheap 10MHz crystal and an imported power transformer which
ran quite hot. Surprisingly, the drift
was less than lppm. Better quality
components will give even better
stability.
Your new 1GHz Digital Frequency Meter is now ready for work. We
hope that you find it a useful addition to your range of test
equipment.
~
JANUARY 1988
53
KITS
Musicolor IV
Flasher
The Musicolor Mk IV is four chase patterns plus
auto chase and reverse chase AND four channel
colour organ with built-in microphone means you're
ready to start a lightshow! Cat K-3143
Make it as the latest in electronic
jewellery, or a burglar warning
light, etc. The choice is yours
and it's easy! cat K-2621
Beat Triggered Strobe
Really makes your music come alive by flashing in
time with the music. You can also use It in
conventional strobe mode. With a variable flash rate
up to about 30 flashes per second. Cat K-3153
71
$
3as
Two project packs to allow you to build
any of the kits. Project Pack One
allows you to build any of the first ten
kits in FunWay One. Project Pack Two
gives you the additional components
required to build any of the 20 kits
(needs Pack One too!) Note - FunWay One book is
NOT included with these kits. FunWay One: Project
Pack One Cat K-2600
sees
How do you
test a Zener?
s59es
Look Mum. No bike!
89
The ultimate in protection ! One of the best alarms
around. Includes its
own siren output. Cat K-3252
$
•
Add an lgnH1on Killer for
Protection
<9
<at>
Nothing's worse than a =~;;~~':.-;·
car th~t ini~behaves.
~
·
.■ iA
Especially If you're
tryilllj to knock it off.
5
C)©
~~~~~ns~7:it:r~t and
stops. Bill Sykes thinks the car's crook and goes off
searching for another! You return to rour car, reset
the ignition killer - and drive away. Cat K-3255
s22
1Oow Amp Module
Use two for stereo, or even use in
bridge for double output! (Get up to a
massive 200W output!) Cat K-3442
Let's see. Out with the
power supply. Work out
the series resistor. Get the
voltmeter and put it across
the zener. Turn on the
supply. Woops! Wrong
resistor. One cooker
Zener... Or you can build
the Zener Diode Tester.
Very simply and
accurately checks Zeners
without danger. Especially handy in the service lab
when the markings are worn off! Cat K-3051
$2995
IR Remote Control Preamp
Full command over your
hi-fi system without
~
moving from your chair!
§
The IR Remote Preamp
O
comprises a complete
preamp in which all
functions can be selected
by infra red remote control. And it's loaded with
features! Cat K-4003
s29ss
s259
Build an amplifaer:
economically!
Teletext - without a VCR
\jjfy&£f7P.
,tt1.1.~~~~
"'--~~ ~,, -;,. :-·;ey,f~ .:_,
_..,,,
Mini Project
Board
80 x 60 x 8mm board with 58
groups of 5 connected terminal
points. Grid is laid out in aloha- t:::E=====:.:=:,
numeric format for simple "track"
identification, and the board is supplied with a pad of
overlays so you can mark out circuitry for later use or
for transferring to pcb/matrix board. Cat P-4614
s11ss
Giant Project Board
Similar to above, but this one has a whopping 128
groups of terminal points. Overall board size 178 x 67 x
8mm, also has 8 bus lines of 25 connected terminals.
Dependable corrosion-free terminals for long life and
circuit reliability. Cat P-4615
$
WAS $18.95
NOW
1795
l'roject Boards
PLUS!
A complete mini work bench! This
one has 256 groups of 5 connected
terminal points plus 16 bus lines of
25 connected terminals. But that"s
not all: the 130 x 170mm board is housed in a plastic
"work bench" complete with three terminals (for power
connection, inpuUoutput, etc). Overall size is 150 x 225
x 20mm. Bona: Work pad included
for circuit working. Cat P-4616
s2 695
Teletext Tuner
Here's a great first "big" project. When you've
finished mucking around, build an amplifier! It's not
too difficult - our new Economy Amplifier Kit
makes it a cinch! Kit is "short form" - does not
include case (H-2900) or transformer (M-6672).
Over SW per channel at <0.05% distortion, CD,
.
d
· t c t K 4001
tu ner, d,scan
aux mpu s. a -
-:::r:;:;::
0
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"
FunWay One Project Packs
s135
~ il:\;.\U,' ' (J
!
s.12995
. -....- 1OOW HF Linear Amplifier
li
The Teletext uner can
Designed for our HF Transceiver (Kbe built into your
6330) but also ferfect for use with
Teletext Decoder (Cat
a huge range o QRP commercial ■
K-6315) so you don't
gear, in the range of 3 to 15 watts
.
need to own laetvecw~,t-hKit
output. Gives around 10 to 14dB
.
comes comp
gain
so
up
100W
output
could
be
everythin you'll need including comprehensive,
obtained from a very modest input.
easy to fo~low instructions. Cat K-6319
Cat K-6331
sg9es
s379
New!
Colour PVC Tape
Computer Tool Kit!
A 12 piece computer tool kit for
those repairs, alterations, etc.
With IC inserter/remover pin
straightener, screwdrivers,
reversible torque screwdriver,
pliers and more. All in handy
zippered case! Cat T-~39
PVC electrical (insulation)
tape in multi colours for
easy identification even has colours for
mains wiring! 18m rolls.
s49ss
ETC
All one price:
95c/perroll
BARGAIN
Gnel/Yellew
Ora11119
111d
Quality Screwdrivers
With this great range of screwdrivers you
can screw it up without ruining it!
Clt No. Tr,e
1 T-6020Stubby- flat head
2 T-6025 Stubby - Philips head
3 T-6030Standard - flat head
4 T-6035Standard - Philips head
5 T-6040 Popular - flat head
6 T-6045 Popular - Philips head
7 T-6050 Long - flat head
8 T-6055 Long - Philips head
9 T-6060 Heavy - flat head
10 T-6065 Heavy - Philips head
(N-1359) Slack Brewn
(N-1360) Bnlwn
(N-1361) BI■
(N-1362)
(N-1363)
(N-1364)
Silastic
Pay Only
$1.95
$1.95
l.95
1.95
$1.95
$1.95
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$3.95
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l
Now we have both types: neutral and acid
curing. Choose the type you require for the
particular application at hand. Both in handy
squeeze tubes - perfect for those hard-toget-at locations.
Aci~ Clri.. :
(732RTV) 75g tube
NNtral Clrill:
(738RTV) 85g tube
s4as s12as
Cat N-1225
Cat N-1226
STORE LOCATIONS
NIW
Swin & Young SIS.
T55 Terrace Level
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613 Princess Hwy
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1150 Mt Alexander Ad
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OLD
157-159 Elizabelh St
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Kings Rd & Woolcock St
Cnr PacHic Hwy & Kingston Rd
SA
77 Grenfell St
668 Pori Road
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Shop T25, Elizabeth Ci1y Centre
Main Norlh Rd & Dariington St
WA
Wharf St & Albany Hwy
66Adelaide St
William St & Robinson Ave
Raine Square, 125 William St
TAS
Shop 40A, Lower Level·
Cat' & Fiddle Arcade
NT
20StuanHwy
Southport
Toowoomba
Townsville
Underwood
(075)32 9863
(076)36 4300
(077)72 5722
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Adelaide
Beverley
Darlington
Elizabeth
Enfield
(08)232 1200
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(09)451 8666
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(09)328 6944
(09)481 3261
Hobart
(002)31 0800
Stuart Park
(089)81 1977
(07)288 5599
(079)27 9644
Dear Customers,
Quite often, the products we advertise are so popular they rur. out wrthin a few days, or unforseen circumstances might hold up shipments so that advertised lines are not in the stores by lhe time the advert
appears. And very occasionally, an error might slip through our checks and appear in lhe advert (after all, we're human too!) Please don't blame the store manager or staff: they cannot solve a dock strike on the
other side of the world, nor fix an error that's appea,ed in print. ,t you're aboutto drive across town to pick up an advertised line, why not play it safe and give them a call first... just in case! Thanks. Diet< Smith
Electronics.
MAJOR DICK SMITH ELECTRONICS AUTHORISED RESELLERS
• NSW•Armldate: Sound Components, 244 Beardy St, 724981 •Balttna:Sellina Electronics, 102a A1"'8rSt, 86 7022• Bowral: F.R.H. Electrical, 28 Station St,611861 •BrokenHUt: Hobbies& Electronics, 31 OxideSt,884098• Ch«leltown:
Newtronlcs, 131 Pacific Hwy, 43 9600•CoffsHarbour: Coffs HarbotJr Electronics, Shop 3 O>fts-HaOOur Mall, Park Ave, 52 5684• Denillquin: Deni Electronics, 220Cressy St. 813672•0ubbo: Chris's Hi-R, 1/100 TalbragarStreet. 828711 • Forster.
Forster Photo Sound, Shop 36, Forster Shopping Village, Breese Pde, 54 5006 •Glen Innes: John SOmmerlad Bectronics. Shops 5& 6 Mackenzie Mall. 323661 •Grtfflth: Mlatronlcs, 166-1708annaAve. 624534•1nverel: Lyn Willing Electronics,
32LawronceSt, 221821 •Kernpaey. Drummond Home Entertainment, 38 ForlhS!Teet, 626265•Leeton: Leeton Record Centre, 121 Pine A,., 53 2081 •LlghtnlngR!dge:Lighlning Ridge Newsagency,40eMorilklSt 290579•1.Jomore, Decro,
12 Cerrlngton St, 21 4137 • Uthgow: Douroy Photographies, 183 Main Street, 51 3173 •Moree: Moree Electron!cs, 26 Balo St, 52 3458 • Parkes: Strad Music Centre, 279-281 Clarinda Street, 623366• Port Mac:quarle: Hall of Electronics, The Horton
Centre, 124 Hort:in St, 83 7440 • Orange: Fyfe Electronics, 296 Summer St, 62 6491 • Sprlngwood: 'Nellington's Electrical Discounts, 132 Macquarie Rd, 51 4888 • Taree: Brad's Ek!ctronlcs, Shop 6, Civic Cinema Centre, Pulteney St, 52 6603
• Tumut Tumut Electronics, 62 Russell St. 47 1631 • Uiladulla: Pau~ Electronic& Hobby Toys, Shop 1, 10 Wescn St, 55 2454 • Wagga: Phillips Electronics, 60 For,yth St, 21 6558 • WOlllngton: Wellington Electrical Service, 110 Lee St, 45 Zl25
•Young: Keith Donges Electronics, 186 Boorowa St, 82 1279 • VIC•Colac: Colao Electronics, 215 Murrary St, 31 2847 •0unotry: Finders Pfy. Ltd., 90 Broadway St, 68 1333• Moe: The Moe Store, 56 Geo~ St, 27 2155• Morweh: Morwell
m~ic:~d~~E1~~~~rt~t i~y~~ ;1~5.l'.3,=~~1J:~b~i~:~a~·
~:p= ~~~BE,~~~~t: ~oi~~~ :t~~~S~p°s~
6e=~~tt~~2~~h~t1'fs~r!K~::~n~w1~c,;~irc:.1st~~:~°r:sal~~~~~.\~~~t.,~~=I~~ ~::2se:.i~:=:~~:.s:3~1
1
~~~~d=:":t,~?kl;~=n~!~=~~h~~~2~
1:1~!~
rn~=~~~
58
Certwright Cente, Nicklin 'Way, 94 7349 •Mackay.Stevens Electronlcs, 42 Victoria St, 51 1723 • Ma,yborough: Keller-Electronics, 218 Adelaide St, 21 45.59 • Mt Isa; Outback El~onlcs, Shop 71, Bandy Hwy, 43 3475 • Nambour: Nambour
Electronics, Shop 4, Lowen House, Ann St, 41 1604 • Noosa Heads: Sunshine Phone Systems, Shop 6, Sunsnine Bazaar, Sunshine Beach Rd, 47 4444 •SA• Mt Gambter. Hutchessons communications centre, 5 Elizabeth St, 25 0400
:J~~n~:c::::::·~::- ·ii=i~r~
m
i
ELECTRONICS
~MUd:Z :a1,129e,1
POST •
PACKING
CHARGES
Order Value
Charge
Order Value
Charge
$5.oo - $9.99
$10.00 - $24.99
$25.00 - $49.99
$2.00
$3.50
$4.50
$50.00 - $75.oo
$75.00 or more
■
$Ns_.Aso.
~:=c~~es-:::=
AGC: 10 Pulteney Sl Adelaide
through
0~
===----=-------P•TY--LT-D=----------------=-
VIS4
P.O..Box 321, North Ryde N.S.W. 2113
Tel: 888 3200
When the chips are down
I didn't have much trouble deciding which story to
relate this month. It was a case of Murphy at his
best. Start at one end of the circuit and it will be
at the other end; start in the middle and you'll
move towards the wrong end. Either way, you can't
win.
The story concerns an AW AMitsubishi 63cm colour set, model
6346, one of several models based
on the ML series chassis. This is a
very recent model and, in fact, the
particular set was still under warranty, the owner having purchased
it three months earlier. He was a
new customer, having recently moved into the district, and apparently
had been directed to me as the
nearest serviceman authorised to
provide warranty service for AW A
sets.
The first contact was by phone,
initially to confirm that I could provide the service and then to find out
what was involved. I confirmed that
I could provide the service, but explained that it would be his responsibility to bring the set to me. Warranty agreements do not cover
•house calls, or the cost of transport
to or from the service department.
The · customer accepted this situation philosophically enough: "No
problem - I'll borrer me mate's
ute."
Those points clarified I made
some attempt to determine the
nature of the fault; loss of picture,
loss of colour, loss of sound or
what?
"Aw no - the picture's gone all
funny; kind of collapsed, if y'know
what I mean."
I wasn't sure whether I did or
not. The best guess was frame collapse, although the implication was
that there was still some kind of a
picture to be seen. Perhaps it was
only a partial collapse. There was
56
SILICON CHIP
obviously no point in probing further; I would just have to wait and
see.
And so it was that the "mate's
ute" eventually turned up with the
set on board, and we carried it into
the workshop. I took the opportunity to connect an antenna and
switch it on, just in case there were
any points to clarify while the
owner was still there. I suppose I
can hardly blame the owner for his
"all funny" description. The first
75mm at the top of the screen was
blank, the next 100mm showed a
reasonably linear picture, from
there to within 50mm or so of the
bottom was grossly expanded, and
the rest of the picture compressed
into that last 50mm.
It was, literally, not a pretty
picture.
Other commitments prevented
me from delving any deeper at that
stage and I put the set aside for a
day or so. When I did get around to
it I fished out the circuit and concentrated on the vertical section
(Fig.1 ).
Special Notice
These notes are being contributed by the author who, from
1950 until July this year, wrote
'The Serviceman" in another
magazine . . We feel sure that
regular readers of that series will
welcome the opportunity to continue following his adventures in
SILICON CHIP.
LP..Si KNOWN f>\CT1JR.€:
OF \V\UR.?l-1'-i, ASou,- .
TO BE: HI, B\.f A FALLING
Sf\rE. Wl·\ll-'ST D'ROWN\t-JG
l N A FL.ASH FL.00t> O~
AC It> RAIN ON '11'\
NV\..\...A.!!.01< t>L.A.INu •..
e:.
Jungle IC
In fact, there wasn't a great deal
to be seen. Most of the functions
were performed inside a 48-pin
jungle type chip (IC201,
MC1310AP), including the vertical
sync separator, vertical oscillator,
ramp generator, and an amplifier
which delivered a signal at pin 16,
which was applied directly to a vertical output pair, Q451 and 452.
And that seemed to be all there was
to it.
I concentrated on the output
stage for a start. I checked the
various minor components, including two diodes, D451 and 452,
but found nothing suspicious.
Similarly, a voltage check around
the two transistors produced
figures very close to those shown on
the circuit.
The next logical step seemed to
be to get the CRO going and check
appropriata waveforms. The circuit
shows two vertical waveforms, one
at the vertical oscillator pin of the
IC (pin 20, waveform 8), and one at
the vertical output pin (pin 16,
waveform 7). I checked waveform 8
first, and this came up virtually
identical with the photograph on
the circuit.
But waveform 7 was another
matter. Even the photograph on the
circuit suggests that there is some
"mush" on the pattern and this appeared to be even more so on my
CRO. But this aside, the shape was
nothing like that on the circuit,
although the amplitude was approximately the same.
So what was happening? Was
the chip at fault and delivering a
faulty waveform to the output
stage, or was the output stage at
fault and somehow loading the chip
and distorting the waveform? Since
I had already checked the output
stage fairly thoroughly I hesitated
to blame it. On the other hand, as I
have remarked before, I am less inclined these days to suspect an IC
until all other possibilities have
seemingly been exhausted. And
there could still be something funny
about one or other of those output
transistors, which didn't show up
on my voltage check.
The transistors are each
mounted on a U-shaped aluminium
heatsink, the "U" being inverted so
that the heatsink sils above the
main board. The ends of the vertical sections are cut to provide
narrow tongues which fit into slots
in the board, then bent slightly to
hold them in place. It was
necessary to remove the heatsinks
from the board in order to gain access to the transistors, but this was
not particularly difficult.
Unfortunately, the effort seemed
to be wasted. Both transistors
tested OK, as did the two diodes,
which I tested a second time while
the transistors were out of circuit. I
also double checked the minor components (resistors and capacitors),
and the height and linearity controls, until I finally convinced
myself that there was nothing in
that part of the circuit which I
hadn't cleared.
Which seemed to put suspicion
squarely back on the chip. But still I
hesitated, trying to think of
anything I might have overlooked. I
drew a blank and was rapidly
reaching the conclusion that the
chip would have to be replaced, if
only to prove the point one way or
the other. After all, I could easily
spend several hours searching
vainly for some external fault,
which may not actually exist, and
finally be forced to change the chip
anyway.
On the other hand, if I changed
the chip now, that point would be
settled once and for all. Granted,
I'd be down the cost of a chip if I
was wrong (but one chip up in my
stock) and down by the time needed
to change the chip. Now I don't pretend to like changing chips, particularly 48-pin monsters - I don't
suppose anybody does - but I've
developed a pretty good routine and
a fair amount of skill over the
years, and can usually do the job in
about 15 minutes. That's no record,
and I know some blokes who can do
it quicker, but it's time well spent to
prove a point.
Sydney or the bush
A more practical snag was that I
didn't have such a chip in stock, so
one had to be ordered, which at
least gave me time to think while I
was awaiting delivery. In fact, this
didn't help much; I had not thought
of any other possibility by the time
the IC arrived so, muttering
something about "Sydney or the
bush", I set to with solderwick,
solder sucker and a good hot iron,
and pulled out the suspect chip.
The whole operation went
smoothly enough and I subsequently fitted the new IC, tidied
everything up, and switched on
hopefully. I don't suppose I need
spell it out; it wouldn't have been
worth writing about if it had been
as easy as all that. Suffice it to say
that the set behaved exactly as
before. I was back to square one.
So what now? Up to this pointJ
had convinced myself that I had
thought of everything before I
changed the chip. Quite obviously I
hadn't, but I was at a loss to think of
some new line of attack. I went over
the circuit again. I had proved, the
hard way, that the chip was not at
fault. I was also convinced that
there were no faulty components in
the output stage. So what did that
leave?
It was more of a growing suspicion than a sudden inspiration but I
found myself thinking more and
more about the scan coils and any
minor associated components.
Faults in scan coils are extremely
rare, but I have seen the effect of a
shorted turn, and it does some
weird things to the picture. In any
case, there was not much else left
to suspect.
Tracing out the circuit from the
vertical output stage to the scan
coils revealed the existence of
several auxiliary components,
apart from the scan coils, and I
..,..,.., ....
JA NUA RY
1988
57
,RHJb
,
Ill
15K
, IW
!Ha)
nsv
Deflection
Yoke
'
C9 11
33µ
160 V
12 V
1
4
02
3
<
1
V
"~
Y3 2
H
Fig.1 portion of the AWA 6346 circuit showing the scan coils and associated
circuitry. The pincushion correction circuit is on PCB-PCC.
made a mental note that these
would have to be checked. But first
the coils themselves. I fished out a
shorted turns tester that I had not
had occasion to use for a long time,
unplugged the scan coils, and
checked for shorted turns. Result: a
clean bill of health; there was
nothing wrong there.
That left only a few auxiliary
components, the main ones being on
a small printed circuit board bolted
to the side of the cabinet and connected to the scan coil circuit via
flying leads and plugs and sockets.
The relevant portion of the circuit
is reproduced here to assist
readers to follow the story. The
board is designated PCB-PCC, the
"PCC" standing for Pin Cushion
Correction. It consists of a
transformer, T571, resistors R575
and 576, and capacitor C575.
Connection to the scan coils is via
two plug and socket sets; PV (Plug
Vertical) and PH (Plug Horizontal).
The vertical scan coils are connected to the vertical output stage
via pin 4 on the deflection yoke
diagram and eventually find their
way back to chassis from pin 3, via
the pincushion network, and a pair
of 8.20 resistors in parallel between "PV1" and chassis. These
resistors appear to be part of a
feedback network, and are not
shown here by reason of their
remote location.
58
SILICON CHIP
I had left the set running while I
visually checked out this section
and related it to the circuit, which
meant that the set had been running for about 15 minutes, much
longer than I had run it so far, since
I had previously turned it on only
long enough to check a few voltages
or whether the replacement chip
had achieved anything. In any case,
I had not been observing the circuitry associated with the scan
coils.
But now my attention was drawn
to R569, a 2200, 1W wirewound
resistor, mounted on the main
board, but effectively connected
between pin 3 (vertical scan coil)
and the 12V rail. I don't know what
function it serves, but I noticed it
for the simple reason that it was
running stinking hot - literally. So
hot, in fact, that it had melted the
solder connecting its pigtails to the
board.
Well, it seemed that at last I was
onto something, even if exactly
what was not clear. Looking at the
circuit again I suspected that, for
some reason, the circuit from pin 3
to chassis was incomplete, forcing
the scan current to seek a path
through R569 and the 12V rail. And
the most likely cause of this would
be failure of the two 8.20 0.25W
resistors (R462 and 464) already
mentioned.
So these were located and check-
ed - only to draw a blank; they
were spot on value and completely
free from any signs of stress. So
much for that theory. But I still had
the idea that there was a fault
somewhere in this chassis return
path and a check with the ohmmeter from pin 3 of the scan coil to
chassis confirmed that there was a
resistance of several hundred
ohms; much higher than seemed
logical.
So began a rather laborious process of checking individual connections involving the printed board
PCC and the associated plugs,
sockets and leads. In detail, PV is a
female plug, on a flying lead, which
mates with male pins, 1 and 2, on
the board. The flying leads are
crimped into the plug contacts and I
suspected that there could be trouble here. Checking this wasn't easy
because of the difficulty of ensuring
that one was making an effective
connection with the contact inside
the plug. But, after several attempts, I finally gave them a tentative all clear.
But what about the board itself,
and particularly the pins. The pins
are hollow and are mounted by inserting them in a hole in the board,
then expanding them with a flaring
tool to make a moderately strong
mechanical joint. Then, when the
board goes through the solder bath,
the flared end of the pin is soldered
to the surrounding copper pattern.
I pulled the board out and examined it closely, using a magnifying glass. As far as I could see, all
four pins were soldered perfectly to
the copper pattern. But the ohmmeter told a different story.
Measuring from pin 1 of PCC to the
surrounding copper pattern showed virtually zero resistance, but not
so pin 2. Here there was a varying
resistance of around several hundred ohms.
Significantly, even though I knew
there was a fault there, I could not
pick it visually. But a few moments
work with a hot iron, and a
somewhat lavish application of
solder and flux, removed any doubt.
In fact, I treated all four pins,
because I could no longer trust a
visual check.
TETIA CORNER
Blaupunkt (Bridge Rectifier
Chassis)
Symptom: Fuse S1242 blows
repeatedly. If the fuse is replaced
often enough, the set will eventually fail completely with a clattering
noise coming from the chassis.
Cure: D1245 (TAG 3-400) SCA
shorted or breaking down under
load. An emergency repair can be
effected by removing diodes
D1242 and D1 244 from the
bridge board. This reverts the set
to its original half-wave rectifier
design, in which state it seems to
run quite happily.
This information supplied by The
Electronics Technicians' Institute
of Australia (Tasmanian branch).
Relief and frustration
Then I switched the set on and up
came a perfect picture. I viewed the
end result with mixed feelings;
relief that I had finally cured the
fault, but also a certain amount of
anger at the frustration I had experienced, and the time I had
wasted, all because of one
miserable dry joint. Only someone
else who has been through it all will
know how I felt.
Still, that's what the game is all
about; one has to take the rough
with the smooth and, in the
ultimate, measure success by the
end result. On that basis this job
had been a complete success, even
if it had been less than satisfactory
financially. And I am still puzzled
as to how that joint could look so
good yet be so poor.
~tb.2.
ANl:>
46~
FR.ON\ AN'-f 5\G,~S
Of course, I had destroyed any
evidence in proving the point, and
there wasn't much help for that. As
I saw the joint, the solder had flowed into the hollow pin and right out
to, and over, the edge of the flared
end. It had also flowed quite freely
over the copper pattern which ran
under the flared section, and it
looked as though these two runs of
solder had mated into one.
Quite obviously they hadn't but,
short of using an electron
microscope that looks around corners, I am at a loss to suggest how it
might have been better checked.
The only real answer, I suppose, is
if in doubt, resolder it. Which I did
of course, but the "doubt" was a
long time a-coming.
And now, for a change of pace,
c..oMr>LE:'1""<=-L.'-f
r~ee-
Or s~~ss.. _.
here is a story from one of my
regular contributors, Mr J.L. of
Tasmania. It is an intriguing story
involving both technical problems
and the ingenuity in solving them,
and the frustration caused by the
replacement parts problem. This is
his story, for which he has
nominated the following appropriate title:
Sharp shooting
One thing about television servicing that appeals to me is the uncertainty principle. When a dead set
comes into the workshop I never
know what killed it, and finding out
involves a series of tests and
guesses that will, hopefully, point to
the faulty part.
This was never more clearly
shown than with a Sharp CX2020
that came in recently. Tracking
down the fault took both practical
and theoretical knowledge, plus experience, suitable test equipment
and a pile of patience.
The customer remarked that the
set failed to start up when switched
on at 7pm, although it had been
working perfectly at 5pm. There
had been no sparks or smoke, just a
total refusal to show any sign of
life. He tried the set on a known
good power point, just in case, but it
was totally dead.
As is the way with so many
customers, he felt sure that the picture tube was done for. He wasn't
really convinced when I tried to explain that if it was the tube, he
should still have sound.
When I switched it on in the
workshop, I heard the degaussing
coils go "boing" which indicated
that part of the set was working.
That characteristic degaussing
sound meant that the power lead,
mains switch and mains fuses were
all intact. I could tell this much
without even taking the back off.
But that's as far as I could go
with the back on. Next it was inside
to check the DC power supply.
Specifically, there should be about
300V on the collector of the chopper transistor (Q701) and, in this
set, 115V on its emitter. The 300V
was there, but not the 115V. Quite
obviously the chopper was not
running.
This set uses a self-oscillating
JANUARY 1988
59
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R60I
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C608
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(16V)
(ML):;
C609
SW60I
R6l0
5.6K(3W)
[F-"°__cJ_N.I)
Fig.2: horizontal oscillator (IC501) and line output stage of the Sharp CX2020. Note the protective diode
incorporated in Q602.
chopper which should self-start,
then come into sync with the line
frequency as the line output stage
gets going. The pulse from the line
stage (Fig.2) is not essential to run
the chopper but, as well as its synchronising function, it is used by the
protection network to indicate the
presence of faults on the line output. No line pulse may mean a fault
and so the chopper is shut down.
So where should I start to look for
a fault in a roundabout network of
this kind.
My first line of attack is to determine if the chopper is trying to selfstart. I do this by looking at the
emitter of the chopper transistor
with the 'scope. If I'm lucky I will
see a brief flick of the trace which
indicates that the transistor is being turned on, if only for one or two
cycles. The output voltage appearing on the emitter is immediately
reflected to the protection circuit,
and if all is not right, the base drive
to the chopper is very promptly
terminated.
In this case, the flicker of the
scope trace, when it did appear,
was so brief as to be almost unnoticeable. Still, it was enough to
say that the chopper was trying,
and at this point I had to make an
60
SILICON CHIP
educated guess as to where the
troubl-e lay. It could be either a fault
in the supply itself, or a fault in the
set proper. It's a "heads or tails"
situation, but experience helps a little. Line output stage faults are
more common than power supply
faults.
In fact, faulty line output transistors are so often the cause of
stoppages that most servicemen
check that component first of all.
It's usually simple to reach the collector and measure its resistance to
chassis. If the meter shows zero
ohms, then the transistor is like the
Christmas turkey. In this case there
was no such indication and the
transistor (Q602) checked out
perfectly.
Well, sort of perfectly, because
the base-emitter junction is difficult
to check in circuit, normally showing as a short through the line drive
transformer. Still, if collectoremitter shows no sign of leakage
then it's a safe bet that the base
emitter junction is OK. Or so one
might think.
My next move was to connect the
CRO to the base of the line output
transistor to see if there was any
drive reaching this point. Again,
this was inconclusive because the
trace merely flickered, without any
evidence of a drive waveform. I
transferred the probe to the collector of the transistor, hoping to see a
similar flicker there. I already
knew that the 115V rail appeared
briefly, so if the line output transistor was being driven at all, there
should be some signs on the collector side. But there wasn't a
sausage.
Unusual failure
Up to this point I hadn't switched
on the soldering iron, but the time
had come and in a couple of
minutes I had the 2SD869 line output transistor lying naked on the
bench. And now I could really
detect the cause of the trouble. The
base emitter junction was as short
a short as any short I have ever
seen. It is an unusual failure for a
power transistor because the basecollector junction seemed undamaged, and there was no trace of
leakage between collector and
emitter.
So now I had the problem of
replacing a 2SD869. This transistor
is one of those odd animals with a
built in protection diode, used in a
number of recent vintage Japanese
sets. Replacing these can be quite a
VOOD FOR Cl-I/PS ... WOOD FOR Cl-I/PS ... WOOD FOR Cl-I/PS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR CHIPS:.. WOOD FOR C
SCOOP PURCHASE
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LM7912CT
LM7915CT
LM79L05ACZ
LM79L12Acz
s1.oo
$1.40
SO.BO
so.90
course!)
This month we're
listing a few of our
~~:9;~~c:EFE~;~Es
LM1 13H
s19_10
LM313H
s11.oo
Doni Forget - it's still
WOOD
Geoff has managed to get hold of a limited
CHIPS
quantity of genuine PA PST fans. They're
the 75mm type for 220V operation.
While they last you can have one for
just$25.95
IC SPECIALS
27C64
200nS 8kx 8 CMOS EPROM 12.5.VPP. These are
stock items in the
~~~~~~
linear range.
!;~~
LM3290Z
s1.1s
prime quality, not factory seconds or floor sweepings!
Whatever your
requirement give
Geoff a call
And they're only $5.99 each
CD4503/80C97 Hex
tor
CMOS
VOLTAGE REGULATORS
AVAILABLE AT LAST
PORTASOL PROFESSIONAL
(it's the complete kit!)
It's
a
gas
knife .. . it's a
soldering
iron ... it's
hot blow. And
a
blow
torch ... it's
a
hot
it comes in a neat carry kit
complete with a bit wiper. No cords or batteries yet it gives
the equivalent of a 1 O to 60W iron. You can get up to 90
minutes average continuous use from a single fill. And you
refill it in seconds using a standard butane gas lighter refill.
· Tip temperatures as high as 400°C
can be set. The kit
includes one soldering tip, a hot kntte, blow torch and hot
blow. The cap contains a flint lighter. The complete kit comes
in a handy case (with stand for the iron) which just about fits
Porta-Sol Professional is $81.00.
PORTASOL STANDARD SOLDERING IRON
in your pocket.
Geoff
has
sold
hundreds
of
'em
to
servicemen
and
technicians. Complete and ready to use like the Professional
but you only get the iron and bit
$39.95.
P.ORTASOL TIPS
Expand the capability of your Portasol Iron with spare tips available for standard iron in
1 mm,
2.4mm, 3.2mm, 4.8mm
and hot knife tip. Professional tips come in same sizes plus
hot
blow
and
blow
torch.
Tips
are
JlQl interchangeable
between irons, so specify Standard or Professional when
ordering. Tips are all
$12.95
each.
IBM and Compatible PC Users!
Save a power point - Get a rewireable IEC plug from Geoff.
It's so easy -on the back of your PC you'll fi_n d an IEC outlet
which is controlled by the power switch on the computer. So
cbop the mains plug off your monitor and connect the L2298
and hey presto you 'll never forget to switch your monitor off
again! Qu_ality Belling Lee (Geoff has a full range of IEC
connectors) Ask for
!e
t
Q:
0
II..
Cl
0
i
LM304H
$6.05
LM305AH
$5.85
LM3051-1
$1.75
LM309H
$5.45
LM309K-STEEL $5.90
LM317H
$7.30
LM317HVH
$10.85
LM317HVK-STEEL
$10.85
LM317K-STEEL $6.60
LM3 17KC
$5.20
LM317MP
$1.85
LM317T
$1.05
LM320H-5.0
$9.65
LM320K-12
$7.70
LM320K-15
$7.70
LM320K-5.0
$7.70
LM320MP-12
$3.25
LM320MP-15
$3.25
LM320MP-5.0
$3.25
LM320T-12
$3.70
LM323K-STEEL $5.50
LM325N
$10.75
LM326H
$11.75
LM326N
$10.75
LM330T-5.0
$1.75
LM333K-STEEL $14.35
LM333T
$6. 70
LM337H
$7.95
LM337HVH
$13.90
LM337HVK-STEEL
$17.45
LM337K -STEEL $9.15
LM337LZ
$1.40
LM337T
$2.55
LM338K-STEEL $13.25
LM340K -15
$5.90
LM340KC-12
$2.30
LM340KC-15
$2.50
LM340KC-5.0
$2.25
LM340T-12
SO.BO
LM340T-15
S0.75
LM340T-5.0
SO.BO
LM341P-12
$1.35
LM341P-15
$1.35
$1 .35
LM341P-5.0
LM342P-12
$1.20
LM342P -15
$1.20
LM342P-5.0
$1.20
LM350K-STEEL $9.65
LM376N
S0.90
LM396K-STEEL $31.90
LM723CN
SO.BO
LM2925T
$4.60
$1.75
LM29:l>T-8.0
LM2931CT
$3.05
LM2935T
$4.80
LM2940CT-5.0 $2.80
LM3524N
$3.65
LM76601N
$3.10
LM78L12ACH
$2.05
LM7BL12ACZ
S0.60
LM78L15ACZ
so.so
LM7905CK
$4.15
LM7912CK
$2.55
~~~~~- 2 5
LM336Z-5.o
LM368H-5.o
LM385Z-1.2
LM385Z-2.5
LM399H
LM3999Z
LM349N
:~:
s1 .90
s 11 .90
$2.40
$2.40
$6.15
$4.75
$16.85
$1.85
$1.20
$2.65
$2.80
S0.60
$7.95
$7.95
$4.80
$1 .25
$1.05
$1.55
$2.40
$1 .20
AUDIO AMPLIFIERS
LM380N
LM380N-B
LM381AN
LM38 1N
LM382N
LM383A T
LM384N
LM386N-1
LM387N
LM388N-1
LM389N
LM390N
LM1875T
$1.90
$1.90
$6.40
$3.95
$3.05
$4.'30
$3.50
$1.65
$2.80
$2.40
$2.40
$1.95
$8.00
INSTRUMElfTA nON
AMPLIFIERS
LM3630
LM363H-10
LM363H-500
LM725CH
$38.00
$24.00
$24.00
$9.20
OPERAnONAL
AMPLIFIERS
LM10CLH
LM10CLN
LM10CN
LM1 1CH
LM11CLH
LM11CLN
LM11CN
LM301AH
LM301AN
LM307H
LM308AH
LM308AN
LM308H
LM308N
LM310H
LM310N
LM312H
LM316H
LM318N
LM321AH
LM321H
LM324AN
LM324N
LM344H
LM346N
LM348N
$8.30
$5.95
$9.30
$9.75
$6.70
$3.30
$3.50
$1.30
S0.70
$1.95
$6.95
$5.10
$2.45
$1.00
$4.20
$4.25
$6.00
$11.20
$2.20
$28.05
$10.15
$4.70
SO.BO
$11.20
$4.75
$1.90
$2.20
SO.SO
$3.10
$1.25
$2.45
$1.05
$0.80
$0.50
$0.30
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$1.10
$1.90
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$2.30
$2.25
$2.25
$2.25
TRANSISTOR ARRAYS
VOLTAGE COMPARATORS
LM306H
LM311H
LM311N
LM319N
LM339AN
LM339N
LM360N
LM360N- 14
LM361 N
LM392N
LM393N
LM710CH
LM1414N
LM3302N
LM358N
LM359N
LM709CN
LM733CH
LM733CN
LM74 1CH
LM 741CN
LM741CN-SGS
LM747CH
LM747CN
LM833N
LM1458H
LM1458N
LM:l>BON
LM3900N
LM4250CN
LM13080N
LM13600N
LM13700N
LM394CH
LM394CN
LM394H
LM395T
LM3046N
LM:ll86N
LM3146N
$5.40
$5.40
$7.40
$3.85
$1 .50
$1.15
$2.15
TEMPERATURE SENSORS
LM3351-1
LM335Z
LM35CAH
LM35CH
LM 35DZ
LM3911H-46
LM3911N
$3.15
$2.40
$12.95
$13.95
$2.60
$5.05
$2.65
SPEOAL FUNCn0N
BLOCKS
LM331AN
LM331H
LM331N
LMC669CCN
LM1812N
LM18:l>N
LM1889M
LM1893N
LM2907N
LM2907N-8
LM291 7N
LM2917N -8
LM 3909N
LM3915N
LM3916N
$9.85
$13.20
$7.60
$11 .05
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COMMI.INICA nONS
ORCUITS
LM565CH
LM567CN
LMC567CN
LM 1496H
LM1496N
LM 1886N
LM:ll89N
LM3189N
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$5.25
$1 .40
$2.35
$5.05
$2.05
$8.05
$3.95
$5.15
$3.20
nMERS
LM322N
LM555CN
LMCSSSCN
LM556CN
LM3905N
$3.05
S0.50
$1.00
$1 .10
$2.35
EXAR PRODUCTS
XR-2201 CP
XR-2202CP
XR-2200CP
XR-2204CP
XR-2206CP
XR-2209CP
XR -2211CP
XR-2240CP
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XR-5533AP
XR -5534ACP
XR-558CP
XR -8038ACP
$1 .65
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$9.40
$5.20
$7.50
$3.45
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$3.30
$7.30
L2298 at only $4.75
8.30 to 5 Monday to Friday, 8.30 to 12 Sat.
Mail Orders add $5.00 to cover postal charges.
GEOFF WOOD ELECTRONICS P/L
All prices INCLUDE sales tax.
(02) 427 16 76
Tax exemption certificates accepted if line value
exceeds $10.00.
p~~==~[ ;:::: e:::====; 229
BURNS BAY RD.
(CORNER BEATRICE ST.)
J~"
;
BANKCARD, MASTERCARD, VISA , CHEQUES
LANE COVE WEST N.SW.
IN C IN NSW
TWX71996
P.O. BOX 671
LANE COVE N.SW. 2066
8RI~
OR CASH CHEERFULLY ACCEPTED
specialising in electronic components for the professional and hobbyist.
pain as each manufacturer seems
to have his own design and none
seem to be compatible.
Here in Tasmania we have a real
spare parts problem as all
manufacturers have withdrawn
their spare parts services to centres in Melbourne or Sydney. So our
Tasmanian customers are now faced with 10 to 20 day delays while
we order the part, then wait for the
invoice, then send the cheque, then
finally get the part. (I know - some
firms do have faster services, but
most do not and our gripe is with
the latter ones).
The only alternative for independent servicemen like myself is to
cultivate our friendships with the
manufacturers' service agents. If
they have what I require, and my
face is welcome in their workshops,
then I might be able to get the parts
needed to put my customers' sets
back into working order in a
reasonable time.
So my immediate need for a
2SD869 led me to the local Sharp
agent. When I asked his receptionist about the availability of
2SD869's, a voice from deep within
the workshop declaimed "Yer don't
need wunna them! A 2SD350 is OK
in that set." The voice was soon
joined to the jovial face of their
technician who volunteered the information that the 2SD869 was only
a 1000V transistor, and the diode
was included to catch any spikes
over that level. On the other hand, a
2SD350 was a 1500V device and to
his knowledge, none had ever failed
in these sets.
He wouldn't tell me the price of
the 2SD869, but as the 2SD350 is
about as cheap as any power transistor can be, I decided then and
there to use one in this repair. So I
soon had a 2SD350 in the chassis,
in place of the original transistor.
Pressing the power switch produced not the expected burst of
sound, but quite the opposite - absolutely nothing. This was a real
disappointment because I was convinced that the transistor had been
the only faulty part in the set.
So I had to start troubleshooting
all over again. This time the CRO on
the chopper base showed a quarter
second burst of drive waveform.
The 115V rail also showed a change
62
SILICON CHIP
- the 'scope trace at the emitter
leapt up the screen, then quickly
dropped back to the zero line. This
was a much more positive response
than the earlier flicker, but it was
no closer to restoring full operation.
Continuing my investigations, I
found that the line output transistor
now showed more enthusiasm at
switch-on, but couldn't be resolved
into actual drive. It just flickered into some kind of action, them died.
So what now? It could be (a) a faulty line oscillator chip (IC501), (b) a
dud line driver transistor (Q601), (c)
a bad line driver transformer
(T601), etc, etc. With a chain of
doubts like this, it is perhaps best to
start at the beginning.
My 'scope was not able to resolve
any trace of line drive from the
oscillator chip at switch on, but
then a quarter of a second or less is
not very long to resolve anything.
What I had to do was power up the
chip and see if it produced the right
waveform. I used a 9V battery fitted with leads and alligator clips to
apply Vee to the chip. The set uses
a 12V rail at this point, but 9V is
enough to see if things will work at
all. In this case, 9V produced a
solid train of square waves and proved the chip to be 100 % .
While the battery was connected
I was able to trace the signal up to
the base of the line driver transistor. They went no further
because the collector is powered
from the 115V rail and this wasn't
working yet. So I had to devise a
way to get voltage onto this rail.
One of the most useful pieces of
equipment in my workshop is a
Variac, a continuously variable
autotransformer. I have also built
up a simple DC power supply using
an old TV transformer, a couple of
diodes and a 350V electrolytic
capacitor. When fed from the
Variac, this supply can deliver from
about 20V up to something over
200V. (It's rather crude, but I
haven't had either the time or the
money to build a better high voltage
power supply).
For this Sharp job, I connected
the DC supply to the 115V rail and
slowly cranked up the Variac. The
9V battery was still connected, and
the IC was delivering drive pulses
to the line driver transistor.
The voltmeter monitoring the
115V rail at first indicated a rising
voltage, but it stabilised at about 5V
and went no higher. Even 100V AC
into the DC supply could produce no
more than 5V out, and the Variac
was humming ominously.
The story is nearly finished!
I took no time at all to find that
the 115V rail was shorted almost
down to chassis. Examination of the
schematic showed two components
as the likely culprits. One was
C713, a l00µF 160V electrolytic
capacitor, and the other was
ZD702, a zener diode , type
EX0074CE, connected between the
rail and chassis.
Roast dinner
The more I thought about that
zener the more dubious it looked.
Then in the parts list I found that it
was a 130V type, twice as high a
voltage as any zener I've ever seen.
I'd bet a dud fuse to a roast dinner
that it was the villain. And so it
was. Not quite a dead short, about
10 ohms, but near enough to stop
the set dead in its tracks.
The zener is only in the set as a
protection device and the set works
quite happily without it. But it is
there for safety reasons and had to
be replaced. So now came the second spare parts trauma with this
set - where do you get a 130V
zener if not from the set's maker?
Fortunately, the zener value is
not critical and I was able to
replace the faulty item with two
62V zeners in series. The set is
now, if anything, a little safer than
it was.
Getting back to the philosophy
expressed at the beginning of this
story, I find television servicing an
occupation that is intellectually
stimulating and full of interest. It is
never boring and the smile on the
face 'of the customer when he
learns that it wasn't the picture
tube after all is all the job satisfaction that I could ask for.
Alternative transistors
Thank you J.L. for a most interesting story and an insight into
the problems faced by our colleagues in more remote areas.
I have no doubt that there may be
those who would question the
wisdom of substituting the unprotected 2SD350 in place of the
original 2SD869, in spite of the
higher rating of the former .
In fact, when I showed this story
to a colleague he immediately rattled of a list of protected output transistors, which he felt could at least
be considered. These included the
2SD870, 871, 899, 900, 951, 952,
953 and 954. However, neither he
nor I would be prepared to stick our
necks out and claim that all of these
would be compatible with the
Sharp circuit.
(Incidentally, most transistors of
this general type, with built in protection diodes, also have an in-built
resistor between base and emitter.
This is not always shown on the circuit symbol and could be mistaken
for leakage. Typical value is about
400.
More to the point, of course, is
the essentially practical problem
faced by J.L. and others who live in
places remote from the manufacturers ' distributors. And even then
the expression "on back order"
crops up all too frequently.
Obviously, all is not cider and
skittles in the Apple Isle, at least as
far as spare parts are concerned.
This being so, people like J.L. have
to do the best they can with what is
available. And at least the substitution was recommended by the
manufacturer's agent who, in turn,
appeared to be basing the recommendation on practical experience.
And I'm sure that no one would
have been happier than J.L. had he
been able to fit the correct replacement but, if it's not available and a
long wait is involved what should
one do? What would you do? More
to the point, perhaps, what would I
do?
See you next month?
it
l F ,-r 'S NOT A\JA\l.A~l.£, W~Prt' 8~0ULt>
ONE 'OO? W~AT WOUl.t> '<OU 'Do? VJHAT
\NOUl.t> ~EV t>O? '<~, W\o\Ai ~HOUt..t> WE t>o?
8.
~110:.~ >WAAT MlGHT' SHE. oo? ALll\OVGH, WMAT
WOUL.t) IT 'Do? Su, Tl-\EN W~AT WOUl...t> Tu.JO
OR MOR6 l)O~~E 10 ME POINT, W'°'~••.
~ ~-=? ))
JANUARY 1988
63
,
Listen to hidden FM transmissions
Subcarrier adaptor
for FM tuners
This simple adaptor circuit fits in your FM tuner
and lets you tap into hidden FM transmissions ..
By JOHN CLARKE
Just recently the Department of
Transport & Communications announced that it is ready to
authorise subcarrier transmissions
on FM broadcasts. Testing of these
transmissions is going on right now
and you can listen to them by
building this simple adaptor circuit.
In America, subcarrier transmissions on FM broadcasts have been
used for years. The Americans
refer to these services as Subsidiary Communications Authorisation or SCA. It is based on a 67kHz
subcarrier which is placed on the
main FM carrier.
In Australia the same system is
being used but it will be known as
&
LEO SIMPSON
Supplementary Monophonic
Transmission (SMT) which will be
generally recognised as an Ancillary Communications Service
(ACS). Not a very inspiring name, is
it?
Australian tests have been on
single sub-carrier transmissions at
67kHz but developments in the USA
provide for multiple sub-carriers,
some carrying digital data and
others carrying audio.
Now 67kHz sub-carrier transmissions are about to be authorised as
regular services in Australia. To
coincide with this, we have designed a suitable adaptor which can be
hooked into most FM tuners with a
This the ACS adaptor board, shown about 30% larger than actual size. All the
parts are readily available.
64
SILICON CHIP
mm1mum of fuss. Low in cost, it
uses just a few readily available integrated circuits.
Before we describe the circuit of
the adaptor, let's briefly talk about
FM subcarrier transmissions. They
will have no effect on standard FM
mono and stereo radios. Also, they
will be fully compatible with all existing FM radios, whether stereo or
mono. In fact, unbeknown to the
great mass of FM listeners, test
transmissions have been going on
for some time.
But while all FM radios are
presently unaffected they are able
to pick up the sub-carrier transmissions and, with the addition of an
adaptor such as the one we
describe here, able to detect the
audio signals which will generally
be music.
While we were developing this
adaptor circuit, the ABC in Sydney
was running ACS test transmissions on 2ABC-FM. The audio
modulation was the program
simultaneously being broadcast by
AM station 2BL. In the near future,
ACS broadcasts are likely to be
background music suitable for offices and factories .
SILICON CHIP'S ACS Adaptor is
built on a compact printed circuit
board (PCB) accommodating three
low cost op amps - a phase lock
loop IC, a 3-terminal regulator and
a handful of resistors and
capacitors.
,-----.. . -------~---~-----------.----A
TWIN -TEE Fil TER
220pF
10k
1.1k
11k
<>-11-.w.,,,.......>;,N,,~--w,;.,,---+--4-__.,.......- 4 _ - ,
DEMODULATED
FM INPUT
VR1
10k
10
>"......W,,,,......aj21N
5600
1.1k
3
~W,,-..::jlN
IC2
LM565
DEMO
OUT
VCO
+6V
MP
5
4.7
16VW
10k
't'--~-ll-"""""'~,-.'IN,f,r+-"M"'""'9--=j
P, RE
-+
1
.001
+-__.....____,.__.____.,__-+_ __;r--.......,__---
G N D 0 - - - - - - - . _ _ . , _ __ _ _ _ _ __ .__--4_ _
.,.
L------------------ll-------o
PLL DEMODULATOR
67kHz BAND-PASS FILTER
18d8/0CTAVE LOW PASS FILTER
GAIN= -1
IN
r + 1 5 V-30V
1
+
35VWI
..,
0. 22
AUDIO
> " - - ~ ~ OUTPUT
---------------vGNO
ACS ADAPTOR FOR FM TUNERS
61-1287
12dB/OCTAVE 6kHz LOW PASS FILTER
GAIN = -10
Fig.2: the circuit for the ACS adaptor is essentially just a phase lock loop with input and output filtering stages. Note
that TL081 op amps may be substituted for the TL071s.
67kHz INPUT
FROM FM
DEMODULATOR
67kHz
BAND PASS
FILTER
PLL
OEMOOULATOR
18d8/0CTAVE
6kHz LOW
PASS FILTER
GAIN = -1
12dB/OCTA VE
6kHz LOW
PASS Fil TER
GAIN = -10
AUDIO
OUTPUT
Fig. 1
Fig.1: this block diagram shows the four circuit functions of the ACS Adaptor.
The corresponding functions are also marked on the circuit diagram (Fig.2).
How it works
Fig.1 shows a block diagram of
our circuit. The 67kHz signal present at the output of the FM detector (in the radio to be modified) is
first fed to a 67kHz bandpass filter
and then to a phase-lock loop (PLL)
which recovers the audio modulation on the 67kHz sub-carrier.
The audio output of the PLL is
then passed through a low pass
filter which attenuates frequencies
above 6kHz at the rate of 18dB/octave. Another 12dB/octave lowpass filter stage completes the conditioning of the signal before it is
passed to an external audio
amplifier.
Fig.2 shows the complete circuit.
Op amp !Cl and associated components provide the 6 7kHz bandpass filter. A twin-T network comprising four 1. lkO resistors and
associated 0.0022µF capacitors is
connected in the feedback network
of the op amp. This gives some gain
at 67kHz and heavy attenuation for
frequencies above and below this
frequency.
An additional passive filter at the
input to the twin-T network (220pF
and 10k0) provides some additional
rolloff for frequencies below
67kHz.
In practice, the bandpass action
covers a frequency range of about
10kHz above and below the 6 7kHz
centre frequency. VRl sets the gain
of the bandpass filter stage.
IC2 is a Signetics NE565 phaselock loop which demodulates the
67kHz frequency modulated (FM)
signal from !Cl. The NE565 PLL
consists of a voltage controlled
oscillator (VCO) set to 67kHz and a
comparator which compares the incoming frequency modulated 67kHz
signal at pin 2 with the VCO signal
fed into pin 5.
The output of the comparator
represents the phase difference
between the incoming signal and
the VCO signal and is therefore the
audio modulation of the subcarrier.
Treble de-emphasis (150µs) is provided by a 0.033µF capacitor (pin
7).
The free-running VCO frequency
is determined by the 0.00lµF
capacitor at pin 9 and the
resistance between the positive rail
and pin 8 (lkO in series with VRZ).
VRZ adjusts the oscillator frequency (also known as the "centre frequency") so that the incoming
JANUARY 1988
65
signal is within the lock range of the
PLL.
To minimise noise in the
demodulated output, it is important
to reduce the lock range of the PLL
to a minimum. This is achieved by
shorting pins 6 and 7 together. To a
lesser extent, the lock range and
therefore the noise output becomes
smaller for lower input signals so
we keep the input signal reasonably
low without prejudicing the PLL's
operation.
Following IC2 is the 18dB/octave
filter employing IC3 which has a
gain of one for wanted signal frequencies. This filter is followed by
the final filter stage IC4 which has
a gain of ten.
The adaptor is ideally powered
from the tuner or receiver it is built
into so we had to make its input
voltage requirements non-critical.
The solution is to use a 12V
3-terminal regulator which enables
the circuit to be powered from any
unregulated DC rail from + 15 to
+ 30 volts.
The three op amp ICs and the PLL
ICIOI LA\231
16
FM IF' AMP, AF AMP
FM OET
I
TPI
FM OISCRI
NULL CHECK
Rll3 Rll2
18k
66
SILICON CHIP
C!I !
33p
Cll3
0.01
are all biased to half the supply
voltage by a voltage divider consisting of two 10k0 resistors which
is decoupled by a 4.7µ,F capacitor.
The centre-point of this voltage
divider is connected to pin 3 of each
op amp and the PLL.
PCB assembly
This photo shows the ACS adaptor
installed in an older AM/FM stereo
receiver, the Harman Kardon hk570i.
We used two brackets to suspend the
Adaptor above the tuner board of the
receiver.
56k
The PCB for this project
measures just 5 7 x 89mm and is
easily assembled.
No special points need to be watched when installing the parts on
the PCB except that component
polarities must be correct. Note
also that ICl has a different orientation to IC2, 3 and 4.
When assembly and soldering
are finished, check your work
carefully and then connect a DC
supply of between 15 and 30 volts.
Now check the voltage at the output
of the 3-terminal regulator, at pin 7
of the TL071 op amps, and at pin 10
of the PLL. In each case the reading
should be close to 12V. The voltage
at pin 3 of each IC should be close
PARTS LIST
IC201 LA3401
MPX
1 PCB, code SC061-1287, 57
x 89mm
3 TL071, LF351 FETinputop
amps
1 NE565 phase lock loop
1 7812 3-terminal 12V
regulator
Capacitors
R211
56k
R213
47k
+
C209
22
16V
R221
KJOk
1161
Fig.3: this is a portion of a typical FM/AM tuner (Sony ST-JX220A) showing
where the ACS adaptor is tapped in, across C111, between the FM detector
and the multiplex decoder.
1
1
1
1
2
1
1
1
1
4
3
1
1
4. 7 µF 1 6VW PC electrolytic
2.2µF 16VW PC electrolytic
1µF 35VW PC electrolytic
1 µF 1 6VW PC electrolytic
0.22µF metallised polyester
.033µF metallised polyester
.022µF metallised polyester
.0068µF metallised polyester
.0056µF metallised polyester
.0022µF metallised polyester
.001 µF metallised polyester
560pF polystyrene
220pF ceramic
Resistors (0.25W, 5%)
GND
1 X 20kf! 2%, 1 X 18kf!, 6 X
10kf!, 2 x 1.8kf!, 4 x 1.1kf! 2%,
1 x 1kf!, 2 X 56011, 1 .x 10kf!
miniature vertical trimpot, 1 x 5kf!
miniature vertical trimpot
+ 15V-30V
GND
INPUT
Miscellaneous
Hookup wire, audio leads, solder
etc.
Fig.4: take care when assembling the board. Note that IC1 is oriented
differently from IC3 and IC4.
to 6V and so should the voltage at
pin 6 of each TL071.
If everything is okey dokey, you
are ready to install the adaptor in
your FM tuner or stereo receiver.
Finding the signal
This is the tricky part. Ideally,
you need access to the circuit
diagram of your tuner or receiver.
You need to identify a positive DC
supply rail of between + 15 and
+ 30 volts. Then you need to find
the output of the FM demodulator.
In a stereo tuner this comes
before the multiplex decoder and
treble de-emphasis networks. In a
mono tuner, you must identify the
demodulator output before deemphasis. After de-emphasis, the
67kHz signal will be non-existent.
We have shown part of a typical
FM tuner circuit (Sony ST-JX220A)
as an example of where the 67kHz
signal must be picked off. As with
most medium priced tuners, it uses
two ICs to do most of its FM processing. These are the IF amp and
detector IC and the following
multiplex (MPX) decoder IC. The
most convenient point to pick off the
67kHz signal is at the input to the
MPX decoder.
Setting up
Having found the signal and
made the necessary connections
from the adaptor to your tuner, the
continued on page 95
Full size PC artwork for the ACS
Adaptor. Design by John Clarke.
Luvverly, innit?
JANUARY 1988
61
By LEO SIMPSON
Most people will be familiar with
Telecom's new cellular phone service which is becoming very
popular with business people who
spend much of their day in their
cars and trucks. Now OTC's
automatic Seaphone service is doing for boats what the cellullar
phone service has done for cars but
at much lower cost.
OTC's VHF Seaphone service has
been operating since 1976 and has
been gradually expanding over the
years to the point where even
relatively minor coastal population
centres now have it.
Early this year though, OTC
decided to substantially upgrade
the service so that people on the
waterways and as far away as
68
SILICON CHIP
100km out to sea could have direct
phone dialling, ship-to-shore. Local
electronics company Heyden-Spike
Ltd won the tender to develop the
system and has now produced a
computerised system which will
radically alter communications on
the water.
The problem of automation
OTC (standing for Australia's
Overseas Telecommunications
Commission] could foresee a large
obstacle in introducing an
automated Seaphone service: cost
to the boat-owners. OTC recognised
that if the new Seaphone service
was to be really popular the cost of
upgrading to it for each boat-owner
would have to be low.
That meant that all existing VHF
marine radios would have to be
usable and the cost of any fancy
dialling facility would also have to
be lower than the cost of a new
radio. This meant that the new
equipment on the boat would have
to be kept relatively simple while all
the "intelligence" would have to be
installed at OTC radio bases on
shore. And that is what has
happened.
Heyden-Spike Ltd has developed
a microphone which, in addition, to
the usual press-to-talk switch, has
12 pushbuttons for phone dialling.
The microphone can be fitted to any
existing VHF marine radio although
it cannot be simply plugged in. The
radio must first be modified to sup-
Thursday Island
OTC VHF
COVERAGE AREAS
VII
Chambers Bay
Point
Quobba
Ch
Ch
Ch
Ch
Long Point
Yanchep
Ch
Ch
Ch
Ch
16
67
23
26
Perth
■ VIP
Esperance *
~<-J
VIE
•
l
Ch 16
Ch 67
Ch 16
Ch 67
Ch 16
Ch
16
67
23
26
Ch 16
~~ ~~
Ch 26
Ch 02
)7
Existing Seaphone/Solas Stations
Ho b art *
Ch
)G ~
Ch2l
New Solas Stations
C~:e~ouga,nville
Sou
* Daytime hours only
p
Ch 16
Ch 67
This map shows the regions on Australia's coastline covered by OTC's Seaphone service. The relevant
VHF channels are 23, 26 and 27, corresponding to 157.1 5, 157.3 and 157.35MHz on transmit and 161.75,
161.9 and 161.95MHz on receive. Soon, virtually all of the eastern seaboard will be accessible by
Sea phone.
ply 12 volts to the microphone
circuitry.
Inside the microphone housing
are two printed circuit boards, one
for the keyboard and the other for
the 44-pin dedicated Motorola
microprocessor which has its own
inbuilt memory (RAM and EPROM).
The processor provides the DTMF
(dual tone multi frequency) tones
for dialling and the code which
identifies every Seaphone licence
holder.
Each Seaphone licence holder
will be allocated a subscriber
number but, for security, the code
stored in the microphone electronics will be known only to the
OTC computers.
Note that all the existing OTC
Seaphone services will be available
to marine radio users but the new
automatic service will only be
usable with those radios which
have been modified with the new
microphone.
Features of the service
The automatic Seaphone service
will be used as follows. The user
switches the VHF marine radio to a
free channel (eg Ch 02, 23, 26 or 27)
and listens to ensure that no calls
are in progress. The phone number
can then be dialled, preceded by
the STD number for Australian
calls or by the country code for international calls.
The user then presses the "*"
button to transmit the stored user 's
auto-Seaphone identifier to OTC's
computerised radio base station.
The user 's code number is then
validated by the computer which
checks to see that the code is valid
and that bills have been paid. A
brief voice announcement will then
state that "your call is being connected" . Normal ring tone will be
heard and when the called party
answers, call charges are recorded
by the computer.
While the call is in progress, the
user operates the press-to-talk button in the normal way. When the
call is finished, the customer
presses the " #" button to reset the
system.
If a call can't be connected, a
voice announcement tells the user
JANUARY 1988
69
automated voice announcement
will respond to the call and if there
are messages, the system will
automatically connect and bill the
Seaphone call to the shore
telephone subscriber who booked
the call earlier. That's a nifty arrangement which must have taken
a lot of thought to develop.
Dial 999 for emergency
Mr Kerry Stratton demonstrates the new push-button microphone which is the
upgrade for VHF marine radios using OTC's direct-dial Seaphone service.
Heyden-Spike Ltd (Brookvale, NSW) developed the new service and the
microphone.
that message and if the code is not
valid or recent accounts have not
been paid, the user is connected to
a (human) operator at the radio
base to sort out the problem.
Naturally, calls can be made
from shore to ship but they have to
be made via the OTC base radio.
This means that a telephone user
calls base radio and asks to contact
a person on the water. Whether or
not the call makes immediate contact depends on whether the
marine radio is turned on and tuned
to the calling channel, and is within
range.
Mailbag
continued from page 3
there are two faults, a broken earth
and a defective neutral. The problem
is that there is no indication of either
of these faults until both of them
occur.
I know a plumber who carries a set
of automotive jumper leads and he
uses them to bridge the gap when
breaking a run of pipe. With MEN,
any green-wire fault currents should
return to neutral if the water pipe is
broken, with no significant voltage
being developed above earth. It
wouldn't be a problem and hence
plumbers would not be aware of it
unless there was a faulty neutral, so
perhaps faulty neutrals are not un70
On the existing Seaphone service
this situation is taken care of by the
message system. Callers leave
messages with the base radio and
when the boat-owner calls in, the
base radio operator can place calls.
As can be imagined, this process
can be quite time consuming, both
for the radio operator and boat
owner.
In the new automatic Seaphone
service, the boat owner merely
presses the "*" button on the
microphone at any time to interrogate the OTC system for "any
Seaphone calls on hand". An
SJLICON CHIP
common in the system. Maybe
plumbers detect them more often
than the County Council people.
A. Lackey
Collaroy Plateau, NSW
Extra earth lead
Thanks very much for your article
on electrical safety [November 1987).
All my life I have been concerned
about electrical safety, not so much
for myself but for others, particularly
those nearest and dearest to me. You
should write some more on the
subject.
I too am super-cautious. Thirty
years ago I fitted an additional earth
In a distress situation, it is normal practice to use Channel 16 with
voice contact to the base radio or a
nearby vessel. With the automated
Seaphone service though there is a
quicker way to draw attention to an
emergency situation. By dialling
999 on any OTC Seaphone channel,
an immediate alarm will be activated and the computerised
system will automatically display
the vessel's name, call sign, type
and the owner's name and address
on the screen at radio base.
The emergency 999 function will
override any Seaphone call in progress on the selected channel.
Cost of the new service
The new service is not expensive,
particularly as far as the initial setup costs are concerned. The cost of
the new microphone plus fitting to a
marine radio is $249. Phone
charges are $1.30 per minute. At
the time of writing OTC was considering the introduction of a
6-second normal tariff charge.
On the face of it, this new
automatic Seaphone service from
OTC must be a winner. It is convenient, easy to use, and reasonably
priced.
~
from our washing machine to the cold
water pipe.
You have my support and best
wishes.
N. Walker
Como, NSW
An excellent magazine
Yours is an excellent magazine. I
had almost given up buying electronics magazines but I will take a
subscription to yours. I hope the standard of your first issue is reflected in
the future. Being a mechanic by trade
and a hobbyist only in electronics, I
find your articles well written and
understandable.
A. Glover
Cootamundra, NSW
Build this
shortwave
e a
Try this antenna switching arrangement
and improve your shortwave reception.
By ED NOLL
If you've ever had difficulty in capturing those
frequencies on the fringe of the shortwave spectrum,
you probably know what a blessing it would be to have
more than one antenna at your disposal. Now you can
- well not really, but the Flexo SWL Aerial can make
it seem as if you do.
The Flexo SWL Aerial is an antenna/antennaswitching system that improves reception by adding
flexibility to a single antenna installation, making it
seem as if you have more than one antenna. Flexo's
extended performance better accommodates the
extraordinary frequency span occupied by the many
shortwave broadcast bands. In effect, you have more
than one choice in dealing with the variables of
antenna length, line length, angle-of-signal arrival,
and propagation conditions.
With the Flexo, sensitivity is made more uniform
over the entire shortwave spectrum. It provides more
than one choice in finding an optimum signal-to-noise
(S/N) or signal-to-interference ratio when attempting
to pull in a specific station. If you listen only to strong
signals, the Flexo won't do much for your receiver's
performance because of the high-sensitivity, high
-- --8) PLUG 1 TO
- - - LY RECEIVER
(a)
Slb
Flg. 1
selectivity, and automatic-gain characteristics of the
latest receivers. However, if difficult receiving
conditions and weak-signal identification are your
bag, give it a try.
When a signal is weak, despite the high sensitivity
of the receiver, even a couple of dB of extra input
signal may help you obtain an ID. Even the strong
signals are subject to brief fades, so a more solid lock
is attractive to the music-loving enthusiast. Since the
needs of shortwave listeners tend to vary, we'll
describe both a simple two-wire Flexo and a really
different three-wire version.
The two-wire Flexo
A complete Flexo antenna and switching
arrangement is given in Fig, 1. Basically, as shown in
Fig. la, the antenna is cut as a dipole on the 60-metre
band. A coaxial transmission line
feeds the signal to the Flexo switch
and another short piece of coax (not
shown) then feeds the switch output
to the receiver. Note that one antenna wire is angled by 45 degrees in
the horizontal plane from the more
usual straight line position.
(b)
Fig.1 - the two-wire Flexo SWL Aerial gives you four
possible combinations. When S1 selects position 1, the
left-hand element is connected directly to the centre
conductor, which feeds the signal to the receiver.
Position 2 connects the element that's offset at a
45-degree angle. In position 3, both elements connect
to the centre conductor. Position 4 gives a dipole
configuration with one element connected to the
centre conductor and the other connected to the
braided shield.
JANUARY 1988
71
14.33m
PARTS LIST FOR THE FLEXO
SWL AERIAL
J 1 - Insulated phono jack
S1 - 2-pole, 4 or 6-position switch (see text)
Antenna elements - bare copper wire, AWG #16 or
#14
Antenna mast - PVC pipe (see text)
Down lead - coax cable or insulated wire (see text)
Metal box, guys, nuts, bolts, etc,
120 '
120'
..~'J,'!,I'>
As shown in Fig.1 b, the two antenna elements can
be angled also by as much as 30 degrees in the
horizontal plane from their usual positions. Thus, they
can be positioned to accommodate the mounting space
in your back yard.
In tests, it has been found that more reception
flexibility is obtained with one element angled rather
than straight. The antenna performs pretty much as a
dipole on the 41 to 60-metre bands. On the remaining
higher-frequency bands, other switch settings were
often preferable to the dipole connection. Remember
that the antenna wires become longer in terms of
wavelength at the higher frequencies and, therefore,
often perform more like a long wire.
The antenna mast was made of telescoped sections
of PVC piping (as shown in the photos). The coaxial
transmission line is fed to the top of the PVC mast by
cutting a hole in the mast at about chest-height. Fig.1
shows how the inner conductor and conducting braid
(outer conductor) of the coaxial line are conneoted at
the top of the mast. Two bolts serve as the antenna
terminals. It is to those terminals that the antenna
wires were attached using solder rings. The elements
were then stretched out in an inverted-V fashion and
brought down to two metal fence posts at ground level.
In effect, you are constructing a 60-metre inverted
THREE WIRES, -::::::
LOOSELY LOOPED -
PLUG 1
S1a - - - - - ~ E R
----CJ'
S1b
30
20
Fig. 2
Fig.2 - The three-element Flexo installation provides
greater flexibility over the two wire type by allowing six
combinations.
dipole, but one with the antenna wires not necessarily
in line.
There are four possible ways to use the two
conductors at the receiver end of the coaxial
transmission line. You can use the two separate
conductors individually (an either-or arrangement), or
connected in parallel. The fourth arrangement is to
The coax cable is fed through a hole, drilled about
chest-high in the PVC piping, to the top of the mast.
This view of the top of the PVC piping shows that the
coax cable terminates in large crimp-on lugs, which are
then secured to the mast using nuts and bolts. The
antenna wires are then connected to the bolts.
72
SILICON
CHIP
use them in dipole fashion.
The four possible choices are made available by a
four-position, two-pole switch. The two switch
sections are shown as Sla and Slb in Fig.la . In
switch position 1, the braid of the coaxial line from the
antenna is connected to the inner conductor of the
short section of coax line that runs to the receiver
input. In effect, the coaxial braid and one of the
14.3-metre antenna wires are being used as a single~
wire feed antenna. Notice that the braid does not
connect to the centre conductor of the coax line.
On position 2 of the switch, the centre conductor of
the coax line and its associated antenna element serve
as a single-wire antenna. In position 3, the braid and
the centre conductor of the coaxial feed line coming
from the antenna are connected to the inner
conductor of the short section coax line that channels
the input signal to the receiver. Thus, both antenna
wires are connected to the receiver in a single-wire
feed arrangement.
On position 4, the centre conductor and braid of the
antenna coax are respectively connected to the centre
conductor and braid of the receiver coax. Thus, when
position 4 is selected, the antenna operates as a true
dipole.
In putting the Flexo switching arrangement
together, you must make certain that the braid of the
transmission line from the antenna is not connected
directly to ground in the switching box. The only time
that the braid is connected to ground is when S1 is in
position 4. In the author·s switching arrangement, the
switch was built into a small metal box measuring 80 x
55 x 100mm. On the rear of the box, the author
mounted two isolated terminals (as shown in the
photos) to which the coaxial line from the antenna is
PVC MAST CONSTRUCTION
An antenna mast can be easily built from
telescoping setions of PVC tubing and a few nuts
and screws to hold the structure together. A
1 .5-metre metal fence ROSt, embedded in the
ground, is used as a foundation for the mast. Two
3-metre sections of PVC tubing can be used to
cqnstruct a mast about 5 .4 -metres high.
Begin with a 5cm diameter section of PVC tubing
and insert a second 3 .8cm diameter section of tubing, to a depth of 60cm, into one end . Drill holes
through the overlapping sections of tubing and bolt
them together. Insert and connect the signal carrying cables as needed. Connect the wires that will
Ii
JI
THROUGHBOLTS '---.....
GROUNO
LEVEL - - - ~ - -
11
11
11
II
jJ
In the three-element installation, the down leads are run
down the outside of the PVC piping through screw-eyes,
and are connected to the feed-in by bolts installed
through the mast.
act as the RF (radio frequency) pick-up elements . If
guys are to be used, cc;onnect them now . Use nylon
stranded rope - the smallest diameter you can
buy. Drop the mast 0ver the fence post and secure
with bolts. Finally, secure the guys. Taller masts
can be built by using ionger or additional lengths of
PVC tubing.
If a taller mast is desired , simply add to the length
by joining two 5em diameter sections of PVC tubing , using a 1-metre length of 3.8cm tubing as a
joint support. Insert the joint support about 60cm into the lower section of the mast. Drill holes and bolt
the two sections together. Secure the upper section in the same manner, with the two outer lengths
of tubing forming as tight a joint as possible . Finish
up by adding the RF pick-up elements , signalcarrying cables , etc. as needed.
JA NUA RY 1988
73
connected. To the left of these is a shielded phono jack
to which the coaxial line feeding the receiver is
connected. If you have trouble finding a two-pole, four
position rotary switch, a two-pole, six-position switch
may be substituted.
The three-wire Flexo
Another Flexo aerial uses three antenna wires and
a three-conductor transmission line as shown in Fig.2.
In that arrangement, the three antenna wires are
spaced 120 degrees in the horizontal plane. It, too, is
erected in the inverted-V fashion. The ends are
dropped down to three metal fence posts near ground
level. A view of that configuration is shown in one of
the photos. The three transmission line wires run
down the outside of the PVC mast through screw eyes
to three terminals that are mounted in the PVC piping
at chest level. From there, a three-wire transmission
line enters the radio room and connects to the Flexo
switcher.
When there are three wires that are part of the
transmission line, there are as many as twelve
individual combinations that can be switched in.
However, the six combinations provided by the
arrangement shown in Fig.2 give good results, and
little improvement can be obtained with additional
combinations. The switching arrangement shown can
select any individual wire for use as a long-wire
antenna. The remaining three positions use the
antenna wires in three separate dipole
configurations. As a result, the Flexo has some limited
directivity when operating as a switched dipole
configuration on the lower-frequency bands.
On the higher-frequency bands, the single-wire
combinations also display directivity. However, the
main advantage is that it gives you six combinations to
choose from in obtaining the best reception possible
for difficult propagation and interference conditions.
Don't expect it to be a cure-all; some additional
·•
The switch box is simply an inexpensive metal cabinet
that carries the selector switch, two screw terminals and
a phono jack.
options may be necessary under difficult conditions.
The switch is a two-pole, six-position type as
recommended previously. Note that Sla selects one of
the individual antenna wires when in positions 1, 2
and 3. Those same positions on Slb are left
unconnected. Thus, you are operating with a singlewire feed for the first three positions and true coaxial
feed for the latter three positions. The last three
positions (4, 5 and 6) of switch Slb connect the wires
in pairs to give a dipole configuration. In the 4, 5 and 6
positions, an appropriate antenna wire is connected to
the braid of the small section of coaxial line that
connects the output of the switcher to the receiver.
In checking out your results, it may be
advantageous to wire the switcher in terms of the
physical positioning of each antenna wire. In wiring
the Flexo switch, be certain to mount three insulated
terminals on the box for connecting the wires from the
antenna. You can use the same size box as for the
previous antenna.
~
Evolution of Electric Railways: ctd from p.7
of the train line pipe, commonly
known as "pulling the train's tail".
By 1950 the railway world was
changing fast. Diesel electric
locomotives had been increasing in
numbers since the war years and
superseding many steam locos. The
first advantages claimed for the
diesels were quicker starting and
longer times between overhauls.
As for running cost measured in
dollars per ton-mile of train hauled,
on some American railroads the
diesel electric could do no better
than existing steam locomotives. In
many countries , including
Australia, running costs of old
worn-out steam plant serviced in
ancient loco sheds did exceed the
expense of servicing and refuelling
74
SILICON CHIP
new diesel electric machines in
brand-spanking new service shops.
A few United States railroads did
show clearly that a large ·modern
steam locomotive could be serviced
and refuelled in a well-equipped
running shop at a cost less than or
equal to the equivalent expense for
diesel electric units of the same
power. The Norfolk & Western
Railway was one such line which
built its last steamer in 1953 and
continued to use steam locomotives
economically right up to April 4th,
1960.
Even then, economy was not the
reason for the death of steam. The
problem was that they were just
about the only railroad left using
steam and new parts and plant
became virtually unobtainable.
It is interesting that the major
manufacturers Alco, Baldwin and
Lima in America built their last
steam locomotive in 1947, 1949 and
1949 respectively, while in
Australia the last steam locomotive
to enter service, in January 1957,
was a 269 tonne giant, the articulated Garratt built by Beyer,
Peacock & Co Ltd, of Manchester
England.
So ended the amazing 160 year
steam era, with the diesel-electric
locomotive now ruling the world's
lines. But let us not forget the other
contender, the electric locomotive
which is widely used around the
world, expecially in Europe.
Next month when we will delve
into Australia ' s part in this
fascinating saga.
~
I
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1,
II
AMATEUR RADIO
By GARRY CHATT, VK2YBX
Amateur television: getting started
This month, we take a brief look at amateur
television and the equipment needed to get started.
As well, there's a handy list of amateur TV
repeaters and ATV groups.
One of the most technically
challenging aspects of amateur
radio is the transmission and reception of television signals, on the
amateur bands. Old timers and
newcomers alike find this medium
most satisfying, as most of the
equipment used is "home brewed" ,
and program material is mostly of a
technical nature.
There are many types of amateur
television, ranging from "slow
scan" TV (SSTV) which utilises a
channel width of only 3kHz, and sequential scanning at an audio rate,
to "fast scan" TV (FSTV) which
utilises a channel width of 7MHz
and transmits 25 pictures per second. As SSTV allows a greater
concentration of energy in a
smaller portion of the spectrum, the
distances over which communica-
tions can be achieved are much
greater than when using FSTV.
Nevertheless, distances exceeding
400km have been achieved using
fast scan TV.
Reception
It comes as no surprise to
discover that the majority of ATV
(amateur TV) activity occurs on the
UHF bands, primarily due to the
overlap between commercial UHF
television and the 570MHz ATV
band. This greatly simplifies the
equipment required for reception.
In fact many operators use a standard band 4 UHF TV antenna and a
UHF television receiver for ATV
reception.
Naturally a dedicated antenna
for UHF channel 35, low loss
feedline, and a GasFet preamp will
Fig.2: test patterns similar to this one
from VK2YBX are often used during
ATV test transmissions.
provide superior performance, but
it can be seen that very little outlay
is required to receive ATV.
Just as an enormous number of
repeaters serve the VHF and UHF
FM nets, so too do a number of ATV
repeaters. In fact most activity in
capital cities is via the local ATV
repeater (see Table 1).
As can be seen from the repeater
listing, the majority have their output on UHF channel 35
(575-582MHz), so that once a
suitable antenna has been obtained, it is simply a matter of determining the location of the nearest
repeater, tuning your UHF television to channel 35, and waiting for
a signal to appear.
Many ATV repeaters are sponsored and maintained by the relevant state branch of the Wireless
Institute of Australia (WIA). The
WIA transmits a weekly 30-minute
news broadcast, normally on Sunday mornings. These broadcasts
are ideal for tuning receivers and
adjusting antennae.
Transmission
Fig.1: some amateurs prefer to build rather than buy equipment. This photo
shows a typical home-made amateur TV station.
76
SILICON CHIP
As with commercial television
broadcasts, the vision transmission
Table 1: ATV Repeaters in Australia
Location
Callsign
Vision 1/P Sound 1/P Vision O/P SoundO/P
Canberra
Wagga Wagga
Sydney
Springwood
Newcastle
Central Coast
Bendigo
Melbourne
Brisbane
Brisbane
Central North
Central North
Adelaide
Adelaide ·
Hockham
Perth
Perth
Devon port
North West
VK1RTV
V.K2RTW
VK2RTV
VK2RTS
VK2RTN
VK2RTG
VK3RMZ
VK3RTV
VK4RAT
VK4RTV
VK5RCN
VK5RCN
VK5RTV
VK5RTV
VK5RWH
VK6ROD
VK6RUF
VK7RAE
VK7RTV
426.25
444.25
426.25
444.25
426.25
426 .25
426 .25
444 .25
444.25
426.25
426.25
579 .25
426.25
444.25
444 .25
426.25
426.25
444 .25
444.25
431.75
449.75
431.75
449 .75
431.75
431.75
431.75
449. 75
449. 75
431 .75
431.75
584. 75
431.75
449.75
449.75
431.75
431 .75
449.75
449.75
579.25
579 .25
579.25
579 .25
579.25
579 .25
579 .25
579.25
579 .25
579.25
579 .25
444.25
579.25
579.25
1246.25
579.25
579 .25
579.25
426.25
584.75
584.75
584.75
584.75
584.75
584 .75
584.75
584.75
584 .75
584.75
584.75
449 .75
584.75
584.75
1251 .75
584.75
584.75
584.75
431.75
sidebands and a sound carrier, the
channel spacing approaches
12MHz.
This sort of channel width would
severely limit the number of
available television channels, so a
system for reducing the required
channel width was developed for
commercial TV stations, which is
also used by ATV operators.
The Vestigial Sideband (VSB)
system, also sometimes known as
Asymmetric Sideband (ASB)
system, involves filtering out the
majority of the upper sideband of
the vision signal, reducing the channel width to around 5MHz. By
careful compensation in the
receiver, the video distortion that
would normally result from the
removal of most of one sideband
can be reduced to negligible
proportions.
Sound transmission is FM, and
although the techniques are similar
to those used for NBFM, the deviation is much greater (50kHz).
Because of the exclusive nature
of ATV and the resultant lower
level of activity, there are few commercial suppliers of suitable ATV
equipment. The South Australian
ATV Group, part of the SA branch
of the WIA, has a number of
Fig.4: superior results can be
obtained by using a resonant
antenna. This 580MHz Yagi gives
BdB of gain and is available from
Dick Smith Electronics.
Fig.3: a portable colour or b/w camera is suitable for amateur TV. The
composite video output from the camera is fed directly to the transmitter.
is amplitude modulated (AM),
whilst the sound is FM. Normally
the sound transmitter runs about
one tenth the output power of the vision transmitter, where two
separate transmitters are used.
However, some operators mix the
FM sound at the vision transmitter
output stage and consequently run
even less audio power to minimise
intermodulation products.
The standard spacing of 5.5MHz
between vision and sound carriers
is used to maintain compatibility
with domestic receivers. The channel bandwidth is 7MHz.
Wide channel spacing is required if good linearity and adequate video bandwidth is to be obtained. With a standard AM
transmission of 625 lines (25
frames per second) with two
Fig.5: this is the test pattern from
VK2RTS at Springwood in NSW.
JA NUA RY 1988
77
Fig.6: 1W amateur TV transceiver from
PC Electronics, USA.
Table 2: Active ATV Groups
• Gladesville Amateur Radio Club TV Group (PO Box 48, Gladesville,
2111 , NSW) . This club conducts test transmissions on UHF channel 35
on Wednesday evenings 7 .30pm-10.30pm, Friday evenings
7.00pm-1 0.00pm, and Saturday and Sunday evenings at various times.
The viewing audience extends from 1 00km south of Sydney to the northern suburbs. The VK2RTV transmitter runs 20W output into a 9dB omnidirectional antenna. Contact Keith VK2ZZO for further information.
• Sydney ATV Group (SATV Group, PO Box 84, Hazlewood, 2779,
NSW) . This group operates repeater VK2RTS (output UHF CH35) .
Operation by touch tone. Liason net operates on 14 7 .3M Hz simplex
every Tuesday evening. VK2RTS re-transmits material from the VK2RTV
test transmissions on Saturday at 7 .30pm.
• South East Queensland ATV Group (SEATV Group, PO Box 3 ,
Chermside, 4032, Qld) . VK4RTV repeater input is via valid television
signal. 70cm liason frequency is 438.025MHz. 2-metre liason frequency is 14 7 .3M Hz. Repeater receive antenna can be rotated by touch
tone operation.
• Wireless Institute of Australia. Most divisions have an active ATV
group. Many state divisions stock ATV publications. See your local
phone book under WIA.
• South Australian ATV Gro,up (GPO Box 1234, Adelaide, SA 5001 ).
The VK5RTV repeater has been licensed for 1 2 years. The present
repeater is a 20W microprocessor-controlled unit located at O'Halloran
Hill , south of Adelaide . Access is via a valid TV signal. The repeater has
over 250 touch tone control commands, and is one of the most versatile
in Australia. Regular transmissions are made on Wednesday evenings
8pm to 10.30pm, and Sunday mornings from 9am to 10.30am.
A "sister" repeater to VK5RTV, VK5RCN, is located at Clare, and is
powered solely by batteries, charged by a wind generator. This repeater
can be cross linked with VK5RTV to provide enhanced ATV coverage
form Adelaide to Whyalla and other outlying areas.
• Victorian Division WIA - ATV Group (3/ 105 Hawthorn Rd , Caulfield
North, Vic. 3161 ). VK3RTV operates from Mt. Dandenong and runs
1 OW into a directional antenna aimed at Geelong and Melbourne.
Repeater input is via a video modulated carrier. Touch tone operation is
required to activate a colour bar test pattern, and several pages of
repeater information. The repeater is solid state and microprocessor
controlled, and has a unique " received signal report" function.
78
SILICON CHIP
transmitter, preamplifier, and
receiver kits available, and it is
known that the Victorian division of
the WIA also had kits available
some time ago.
One supplier in the USA, PC Electronics (2522 Paxson Lane, Arcadia, California 91006) regularly
advertises a 70cm ATV
transceiver, Model TC70-1, which
has met with good success in
Australia. This company also has a
downconverter suitable for the
420-450MHz ATV simplex (and
repeater input) band which contains an inbuilt GasFet pr eamp,
Model TVC-4G.
One of the higher bands w hich is
presently being used for FM A TV
experimentation, both here and in
Europe , is the 2 3cm band
(1240-1300MHz). There are a
number of suitable " building
blocks'' which make ATV reception
r elatively simple in this band.
These include satellite TV
downconverters which convert the
950-1250MHz and 950-1750MHz
bands to 70MHz. Wyman Research
(PO Box 95 , Waldron, Indiana
46182) in the USA caters for this
type of A TV equipment.
Recommended reading:
(1). UHF/VHF Manual; G.R. Jessop
(available from most amateur radio
stockists).
(2). The 1987 ARRL Handbook;
published by the ARRL.
(3.) Radio and Television Broadcast
Stations 1986; Australian Government Publishing Service.
.~
Bench/portable
multimeter from
Fluke
Most technicians and enthusiasts
will already be familiar with the
popular Fluke 70-series digital
multimeters and their rugged-20
series for use in areas where dirt
and grime is problem. Complementing that range is the Fluke 37 bench/portable DMM which offers additional facilities to the former
meters.
As with the 70 and 20-series, the
Fluke 37 is auto-ranging, has 3200
count offering greater resolution
than standard multimeters, and it
has the bargraph feature which is
handy for nulling and peaking since
it responds faster than the digital
display.
Naturally, it can be used with all
standard Fluke probes and
accessories.
The 37 model offers minimax
recording whereby it will store the
highest and lowest digital readings,
over long intervals, as much as
several days. This can be very handy in servicing and design work. It
also offers Relative Mode, which
shows the change between a stored
reading and any following reading.
This can also be useful for nulling
test lead resistance.
All these features are incorported in an attractive bench style
Cute pedal
accessories from
Cutec
Arista has a range of eight audio
accessories for guitarists. All are
housed in a sturdy plastic box with
heavy pedal operated switch and
powered by a 9V battery (Eveready
216 or equivalent). No power
switch is fitted as this function is
performed when a jack is placed into the input socket.
We had a look at three of the
units in the range and can confirm
that they are ruggedly built, well
finished and quite suited to being
stomped on with a size 12 boot.
Typical of the range is the Stereo
Chorus which uses bucket brigade
devices to produce the time delay
necessary to simulate two voices.
The Over Drive is a distortion circuit giving a similar effect to an
over-driven amplifier fuzz box
case which has a tilting foot and a
built-in compartment for test lead
and accessory storage. The model
37 is priced at $490 plus 20% sales
tax where applicable.
Enquiries should be directed to
Obiat Pty Ltd, PO Box 37,
Beaconsfield, NSW. Phone (02} 698
4776.
(for echo and reverb effects),
Graphic Equaliser and Parametric
Equaliser. All units have simulated
stereo outputs by the way.
The Cutec range is marketed by
Arista and is widely available from
hifi dealers and electronic parts
suppliers.
Wet-dry head cleaner
for VCRs
while the Stereo Phaser is a
dynamic phase shifter which gives
effects from tremolo to a jet sound.
Other units in the Cutec range
are a Flanger, Stereo Analog Delay
While there is a certain amount
of controversy over head cleaning
tapes just about all VCR manufacturers distribute their own brands
of cleaning tapes. This one from
Arista can be used as a wet or dry
cleaner and is recommended for
use, by the manufacturer, for every
20 to 30 hours of operation.
The cleaning tape is not abrasive
but consists of a fabric ribbon. The
cleaning fluid is applied by squeezing the bottle to apply five or six
JA NUARY 1988
79
pliances, model train or model car
motors or whatever? We certainly
have. Now you can have clean compressed air for just these tasks
without having to spend several
hundred dollars on an air compressor or having to go to the
bother of hiring a cylinder of compressed air.
Smoke detector has
optical sensor
drops into the appropriate hole in
the cassette. Arista warn that if the
tape is used in this latter mode, it
may trigger the dew point sensor on
some VCRs. For these machines
they recommend that the tape be
used dry.
The cleaning tapes are available
from all Arista outlets.
Handy 400g
containers
of ammonium
persulphate
Electrolube Air Duster is the
answer. It's an aerosol-powered
550g container of irtert gas (we
guess it's probably nitrogen) which
comes with a small plastic hose to
enable the air to be directed where
you want it. It gives a good finely
focussed blast and is surprisingly
effective.
Pardon the pun, but it's a bottler.
Priced at $11.95 from Jaycar.
For those who like to etch their
own small printed circuit boards,
Jaycar has made available this handy 400g container of ammonium
persulphate. Etching instructions
are on the label. According to
Jaycar, the contents are sufficient
to etch typical boards up to 500 sq
cm in area. It is available from all
Jaycar stores.
Electrolube
Air Duster
How often have you wished you
had a small air compressor to blow
out carburettor jets, small ap80
SILICON CHIP
Some years ago smoke detectors
with a radioactive element sensor
were on the market but they were
withdrawn because of public fears
about radiation. This new smoke
detector from Arista Electronics
Pty Ltd has an optical sensor comprising an infrared light emitting
diode and photodiode. When the
light path between the two is interrupted by smoke, the alarm is
tripped.
It runs from an external supply
or its own 9V battery and has its
own piezoelectric alarm. It may
also be linked to other smoke
alarms in a security system or home
burglar alarm via two wires. Protruding through the grille of the unit
is a test pushbutton and a LED
which glows when the unit is
tripped.
We found it an effective unit. It is
available from all Arista retail
outlets.
.,.•~.r..1;~.,;~
RCS Radio Pty Ltd is the only company which
manufactures and sells every PCB & front panel
published in SILICON CHIP, ETl and EA.
651 Forest Road, Bexley, NSW 2207
Phone (02) 587 3491 for instant prices
4-HOUR TURNAROUND SERVICE
High per£ormance
headphone
amplifier for CDs
REPLACEMENT
TIPS
Professional Porta sol
gas powered soldering iron
Last month we briefly reviewed
the standard model Portasol iron
and recommended it as a very effective unit for all sorts of situations. Now there is a new version
called Professional Portasol. This
blue coloured unit comes in a neat
plastic case which incorporates a
small dish with a piece of foam in it
(for wiping the iron's tip), a small
wire stand and four accessory tips.
One was a standard soldering tip
while the other three comprised a
hot knife, a hot blower and a mini
blow torch.
While the latter accessories are
novel they are certainly effective
although the unit must be full of
butane for best results.
If you have the occasional need
for a small blowtorch as well as a
gas-powered soldering iron, this
Professional Portasol is a bargain.
It is available for $81 from Geoff
Wood Electronics. Phone (02) 427
1676.
Electromark have a high performance stereo headphone amplifier,
the ILP HY67, which would be ideal
for use with CD players which do
not already have a stereo headphone output. Fully encapsulated,
the unit has a signal-to-noise ratio
of lOOdB, separation between channels of 60dB and total harmonic
distortion of less than .01 %.
The HY67 can drive typical
stereo headphones with impedance
from 80 to 2kQ and can be powered
from supply rails up to ± 25V DC to
obtain a generous output level. As
well as being used with domestic
compact disc players, the headphone amplifier would be ideal for
use with a disco console for cueing.
For further information, contact
Electromark Pty Ltd, 40 Barry Ave,
Mortdale NSW. Phone (02) 533
4896.
two outlet LF-2 is $99 while the four
oulet model LF-4 is $269. They are
available from Jaycar stores.
Back copies of
Silicon Chip
Squeeky clean mains filters
Sooner or later anybody who has
a computer system will want a
mains suppressor. Transient
voltages superimposed on the mains
can cause system crashes and data
loss. This can be frustrating, time-
consuming and expensive.
These filters are made in
Australia by KCC and are fully approved by the Energy Authorities.
They can be recommended as a
source of clean mains power. The
Those readers who missed the
first two issues of SILICON CHIP can
purchase mint copies from our offices . The highlights of the first
issue included the first article on
our Digital Frequency Meter, a
Capacitance Adaptor for DMMs
and an Off-hook Indicator for
Telephones. Highlights of the second issue included a fully protected 100 watt power amp module,
a 24V to 12V converter for trucks
and a passive IR sensor for burglar
alarms. For details on how to order,
see page 92.
JANUA RY 1988
81
THE WAY I SEE IT
By NEVILLE WILLIAMS
Information has its place
what about knowledge?
It's possible to assemble any amount of routine
information about such things as the steam age,
the gramophone era or the birth of radio and hifi
in Australia but, sadly and in the normal course of
events, many of us carry to the grave a wealth of
first-hand knowledge of how things really were,
when it was all happening.
You may quibble about my choice
of the two key words in the above
heading and introduction but by
"information" I mean routine
references to dates, people, facts
and situations which can be found
in books, journals, newspapers and
documents, much prized by those
who delight in researching and
reconstructing history - accurately or otherwise.
By "knowledge", on the other
hand, I am referring to an innate
familiarity based on actual personal experience, or acquired or
communicated at that level.
It is important, as I see it, to differentiate between the two, not just
in the context of history but of the
present and future as well. Let's
think about it.
I'm becoming increasingly aware
of the distinction, as there seems to
be more than usual interest in the
past at the moment. You've probably noticed the recurring historic
themes on television, the emphasis
on restored buildings, the proliferation of antique dealers in country
towns, and so on.
Doubtless, some of this can be
put down to nostalgia, fond
82
SILICON CHIP
memories of times and situations
where people may have felt better
able to cope. But, beyond that, the
past has its own unique interest,
and its own unique value as a
reference with which to compare
the present and the future.
ABC's "Talking History"
For me, the matter was brought
into focus when I was contacted by
Stephen Rapley, presenter for the
ABC's Social History Unit. Their
program series "Talking History"
is currently being broadcast over
ABC Radio National and by satellite
to regional centres each Saturday
after the 1.30pm news (1.00pm in
South Australia).
The series covers a whole range
of subjects of social historical interest, but Stephen Rapley has most
recently been researching for a
future presentation on "Radio and
Telecommunications" in Australia.
At least that is the formal subject
title in the ABC's "Talking History"
brochure. In a news item published
in the September IREE "Monitor",
interest was expressed in topics
such as the contribution of
Australia's pioneer wireless
but
amateurs and engineers, the
emergence of broadcast stations in
the early '20s, local receiver
manufacture from the same period,
the Royal Flying Doctor Service, the
School of the Air, the vital role of
telecommunications in Australia's
development, the impact of television, the FM story and so on.
When he subsequently called to
see me, Stephen Rapley explained
the philosophy behind the series in
more detail. Dates and facts have
their rightful place, he said, but on
their own they're pretty dry fare,
especially for broadcasting.
The idea behind ''Talking
History" or oral history, if you like,
is to record for posterity the voices
and the impressions of people who
were actually involved in or lived
through the relevant periods. Their
stories and their first-hand account
of events and situations can
breathe life into regular but often
dry documented information.
Putting his theories into action
over morning tea, Stephen encouraged me to reminisce about my
life as a lad in a small country town,
dependent for amusement and information in those days on purely
local sources. We had no telephone,
no gramophone, no wireless and only irregular, shared newspapers.
Talking "historians"?
How did we occupy our time in
the evenings? As kids, I said, we did
our chores and played with other
kids until dark during the summer,
sat around shivering during the
winter and went off to bed with a
No runaround - when it was most needed!
The first two articles in this
series carried stories of people
who had received the runaround
instead of prompt electronic service. This story has a different
slant. It concerns a disabled pensioner lady who wanted a
"runaround" and couldn't get it.
The runaround in question is an
electric motorised wheelchair on
which she depends for mobility
outside the house. With its help,
she can do shopping or attend the
occasional social gathering. But
recently, in the middle of such an
outing, the drive system went
dead and she and her chair had to
be brought back home in a
neighbour's panel van.
Rather nervous about the cost of
getting it fixed , she rang the local
agent, who suggested that the
fault was probably iii the speed
control system . It was concentrated on an easily removeable
component board and it might be
possible to have it removed by
warm iron wrapped up in a towel at
our feet!
When did I first hear a wireless
set? On headphones or a
loudspeaker? What was it like
when we got a set of our own?
What were those early receivers
like? How did a country boy come to
get involved in radio as a career?
What was it like, working in a '30s
style radio factory? And so on.
None of this was actually recorded. As I talked, Stephen Rapley
scribbled industriously in his note
pad and fired back more prompts
and more questions. He was identifying possible subject themes to be
pursued and developed in the
weeks that followed.
Finally, what about other people
with whom I had shared the
wireless, radio, hifi and TV scene
during my working life? And here I
must confess to "dabbing in" a few
associates from past days cautiously, because I was not in all
cases aware of their present circumstances. But some, I knew, had
a story to tell. For example:
• Winston Muscio, ex STC & BSR,
someone on the spot and sent in
for checking. This she was about
to arrange.
When the board was duly removed, it was draped with the exploded remains of what had apparently
been an electrolytic capacitor but
there was no way of telling
whether this had been the cause
of the breakdown or the result of it.
Sufficient to say, the board was
despatched to the agent forthwith
for what he had tipped to be a couple of hours' work. However, when
she rang a few days later to inquire
about progress, she was told that
it had been sent interstate to their
central service centre.
When she had still heard nothing
a couple of weeks later, she wrote
direct to the service centre, who
phoned her back to say that the
unit had been extensively damaged by someone having reversed
the connections to the battery this, despite her insistence that the
chair had been operating normally
author of "Australian Radio - the
Technical Story"? "I already have
some source material from him on
tape", said Stephen R.
• Neville Thiele, of vented
enclosure fame, prominent EMI
engineer, more recently retired
from the ABC? "Initial contact had
already been made''.
• Ernest Benson, former AW A
engineer/editor, writer and lecturer
and pioneer electronic organ enthusiast? "How do I get in touch?"
• Reg Boyle, retired PMG senior
engineer, who saw broadcasting
and telecommunications from the
inside? "I've already made contact
with him through the IREE".
There were other long-time acquaintances who came to mind as
we chatted and doubtless, still
others who will respond positively
to the news item in the IREE
" Monitor". If you want to follow it
up, Stephen Rapley can be contacted at the Social History Unit,
ABC Radio, GPO Box 9994, Sydney,
NSW 2001 (Phone 02 339 0211, Ext
2683).
for months and that the breakdown
had occurred quite spontaneously.
As far as they ,could tell from
their paperwork, the board had
been repaired and despatched; it
must have gone astray somewhere. They'd have to check
around and let her know in due
course.
Where they looked and where
they found the board they never
admitted but the local agent did
ultimately ring to say that it had just
been despatched. In the meantime, she'd been sitting around for
five full weeks waiting for someone
to do a two-hour job!
It could just be that there's a
bright side to the story: she's had
the runaround now for two weeks
or more, without any sign of the
bill. "Maybe they've also mislaid
the paperwork", she said, "or they
may feel bad enough about it not to
charge me for replacing the little
gadget" .
Time will tell!
Typical recording session
In my case, Stephen Rapley's intention had been to record a more
structured but still informal chat in
my own home but intermittent traffic noise put paid to that. We ended
up in an ABC studio in William St,
Sydney, for the best part of three
hours while I responded to questions and prompts, some from the
interviewer's notes, others quite
spontaneous, arising from what had
just been said.
I found myself having to explain
the uncertainty about the time of
day in the pre-wireless era. How
domestic mantel clocks would vary
with the temperature and whether
or not they had been inadvertently
under-wound or over-wound. How
they could be 10-15 minutes out and
we wouldn't know, unless
somebody noticed the clock in the
stationmaster's office on the way
home and worked out that ours just
had to be wrong.
The chiming town clock? The
nearest one would have been
eleven miles (18km) of rutted road
away! Wireless solved that proJANUA RY 1988
83
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84
SILICON CHIP
blem, as well as providing up-todate (though not always accurate)
weather reports.
I recalled searching the scrub
with my father for a couple of tall
saplings to support the mandatory
30ft (10m) high aerial; contriving an
effective earth in parched ground
and adding a lightning arrester vital in an area prone to
thunderstorms and virtually devoid
of other overhead wires.
Oh yes, and the need to ration
family listening to one or two broadcasts a day. Why? To conserve batteries - because in those days a
set of new batteries, railed from the
city, could make an awful mess of a
week's wages!
Mention of a week's wages prompted further recollection of the
dismay when the primary winding
of one of the interstage
transformers in the family Colmovox burned out. What did my
father do but carefully dismantle
the whole thing, unwinding
thousands of turns of hair-fine wire
until he had located and repaired
the break. Then he successfully rewound it, entirely by hand - a feat
at which I still boggle.
Reliving these and many other
such situations, it became abundantly evident how far removed the
ABC's "talking history" was from
the documented information that
broadcasting stations commenced
operation at certain times and
places, allowing battery-powered
receivers of the period to bring
news, weather reports and entertainment to hitherto isolated
listeners.
How much of the recorded
material gets to air, or in what
form, is not for me to say. The present intention is to edit selected
segments into suitably instructive
and hopefully entertaining sessions, after which the master tapes
will be passed over to the national
archives. Contrast that with the
following.
Are computers addictive?
While involved in this and other
historically oriented projects, I've
had reason to chase through sundry
references in an effort to pinpoint
particular events and dates. You
know how it is: you're certain you
have the information somewhere;
you remember having seen it when
looking for something else; now you
can't find it!
Wouldn't it be great to have it on
computer? You could simply put it
up on screen, scan through it
yourself or, easier still, request the
computer to find this, that or the
other for you - which it can do in
seconds flat!
So, one wet and lazy day, I reached down my copy of the Macquarie
"Book of Events" and abridged the
contents of the chapter on "Radio &
Television" into a series of one line
entries into the computer.
It looked promising, even in that
very abridged form and, since then,
I've dropped in quite a few more
dates and events as I came across
them. Providing I don't decide to do
it some other way, the list seems all
set to grow like the proverbial Topsy. The main reason why it hasn't
already reached maturity is that
I've had to give priority to other,
more urgent tasks.
But I'm conscious that the embryo list has a certain on-going
fascination (did I say addiction?); a
compulsion to generate an original
personalised chronological listing,
almost as an end in itself. This,
despite the fact that a long list of
dates and abridged information on
a computer screen is deadly dull!
A comprehensive list would undoubtedly prove very useful but, in
the process of its compilation, I personally would become little the
wiser. By its use, I might even
become the poorer for not having
occasionally to search through the
literature and be reminded of other
things in the process.
The way I see it, instant access to
computerised information must be
seen as an efficient tool in the execution of certain tasks. In no sense
is it a substitute for assimilated
knowledge or innate knowledge of
the kind possessed by people who
have "been there and done that"!
My own embryo dates/events list
could be regarded as a miniature
version of a much wider scene. Any
number of computer databases
already exist out there, with the
largest collection of information
stored in a publicly accessible computer, in Australia, being that in
"CSX", maintained by the CSIRO.
The overall system is reputedly
so large and diverse that the people
who have access to it are said to
understand only the part which
they actually use. It is doubtful
whether anyone is aware of its total
contents.
I gather that much the same applies to other larger databases
around the world for the same
basic reason: like CSX, they have
simply grown over a period of time,
without sufficient attention having
been given to the problem of gaining
easy access to all the information
that has accumulated. For most
private computer users though,
databases are still something that
they read about.
But massive changes in the recording and dissemination of information are already visible on the
horizon. Huge quantities of
reference information can now be
stored on derivatives of the compact disc - typically more than
500 gigabytes per disc, equivalent
to 150,000 pages of printed A4 text
or a complete set of a large
encyclopaedia.
Grolier's American Academic
Encyclopaedia has already been
transferred to a single disc (words
only) while the UK-based Commonwealth Agricultural Bureau
has been making its database
abstracts available on CD-ROM on
a 2-year subscription basis although currently a rather expensive option.
It will only be a matter of time
though, before these databases become available at a price within
reach of most people with access to
a suitably specified CD player and
personal computer.
About then, we will have entered
the era of what Gareth Powell, computer feature writer for the Sydney
Morning Herald , has variously
described as hyperlearning ,
hyperteaching, h yperwriting,
hyper-reading, or hyperfiling. Oddly, and according to my dictionary,
the prefix " hyper" means "over" ,
implying excess or exaggeration.
That aside, I'll go along with the
terms hyperwriting and hyperfiling,
because they imply a staggering
concentration of information. That
it certainly would be, or is.
But these terms get back to my
earlier objection. Access to a huge
amount of information may be both
practical and useful to those who
need it for specific reasons, but it
has no 1:1 connection with acquisition, as implied by reading,
teaching or learning; in short, with
acquired knowledge.
In case you feel that I am expressing a purely personal view, let
me quote a systems manager with
whom I discussed the generalities
of computer databases: "It is important to realise that they are
simply capacious data files ...
sources of information ... nothing
more."
How many families already
display in their living rooms a nice1y bound multi-volume en-
Personal Phone Ringer natural resonance of the transducer.
You can also vary the frequency
of modulation of the oscillator by
using different values for Cs
although we assume that most constructors will stick with the value of
O.lµF which we have nominated.
Installation
Installing your new phone ringer
is easy. Just identify the connections to the bell ringer coil(s) and
substitute the two leads to the
phone ringer instead. Before you
make the connections though, you
should work out where and how to
mount both the printed circuit
ctd from p.25
board and the piezo transducer.
This will take some ingenuity in
some cases because even though
there is usually quite a lot of waste
space inside most phones, much of
it is unusable.
On the Telecom BOO-series
telephones which are installed in
most homes, the bell ringer coil is
connected between terminals Pl
and GS5. To disable the internal
bell, we suggest you connect both
ringer coil leads to Pl and then
wire the new ringer circuit between Pl and GS5. Doing it this way
makes it easy to restore the phone
to original condition if necessary.
We installed our prototype in an
cyclopaedia, containing a wealth of
information? It could be the source
of considerable knowledge but may
not, in fact, be consulted from one
year to the next.
Is there any reason then why
electronic encyclopaedias and
databases should be any different,
whether on disc or at the end of an
incoming fibre optic cable?
I'm not averse to encyclopaedias
and databases on chips or discs but
please, don't let's confuse mere access to information with knowledge,
however acquired.
Is there any real basis for such
apprehension? Is there any indication of data being substituted for
knowledge? I believe there is, right
here in our own industry.
Electronic "Living History", 1987
style, can still call on people who, in
their day, shared at first hand in
the application of basic technology;
who were involved in the design
and production of everything from
small components, through consumer equipment to the largest
transmitters; who enjoyed an easy
rapport with their peers from
overseas.
Next time around, another
Stephen Rapley may be less fortunate . The old timers may
remember the trends, components
and user manuals imported from
overseas but, apart from a few
isolated high-tech areas, innate
knowledge will be a rare
commodity.
That's the way I see it!
It:
BOO series phone by glueing the
board to one of the flat metal pillars
which support the dial mechanism,
The piezo ringer was then glued
edge-on to the base plate close by.
Five-minute epoxy was the adhesive
used. Tricky, huh?
Incidentally, glueing the
transducer edge-on renders it
louder than if it is secured on the
flat. The end result was quite a bit
louder than the original bells so we
detuned it a little by adjusting the
trimpot.
As a final note, this circuit can be
used as an alarm wherever a DC
voltage of 20 to 30 volts is available.
It is loud, arresting but not unpleasant and its current consumption is
low, at around lmA.
~
JAN UARY 1988
85
DIGITAL
F
In this chapter, we look at the circuits· that
make up the various logic elements and discuss
· their operation. We also look at the various
logic families; and ·we .test your knowledge.
LESSON 3: DIGITAL CIRCUITS
By Louis E. Frenzel, Jr.
In the previous lesson, we introduced the basic
digital logic elements, such as the inverter, AND gate,
OR gate, and NAND and NOR gates. These are the basic
logic elements that process binary signals in digital
equipment. We discussed their operation in terms of
the logic functions they perform and the operation of
each was expressed in Boolean algebra, truth tables,
and timing diagrams. Only logic symbols were used to
illustrate those devices. In this lesson though, we want
to take a look inside the logic symbols.
There are two basic methods of implementing
digital circuits: discrete and integrated. Discrete component circuits are those made up of individual transistors, resistors, diodes, capacitors and other components wired together on a printed circuit board. The
integrated circuit has all the components together on a
tiny chip of silicon.
Today, most digital circuits you will encounter will
be of the integrated circuit form. Occasionally,
however, you will run across a discrete component
circuit in an older piece of equipment or in one requiring some special or simple function. We will discuss
both ICs and discrete component circuits in this
lesson.
Inverters
Let's begin our discussion with the circuit used to
make a logic inverter. We will talk about simple
discrete-component circuits first and that knowledge
will easily translate to integrated circuits. For our
discussion here, zero volts or ground represents a
binary O and + 5V DC represents a binary 1.
The main element in an inverter circuit is a switch
as shown in Fig. la. The switch is connected in series
with a resistor to the supply voltage. A binary input
86
SILICON CHIP
+5V
,_:~
INJ!UT---l\ ~
/OUTPUT
✓
" --
R1
OUTPUT
(a)
Fig.1: a logic inverter operates like a shunt switch (a) in
parallel with the output. A transistor (b) operated at
cut-off and saturation functions in the same manner.
signal controls the operation of the switch and the
binary output appears across the switch. When the input is binary 0, the switch is open. The output,
therefore, is + 5V or binary 1.
If the input is binary 1, the switch is closed. Current
flows through the switch and resistor Rl. The output is
0 volts or binary 0, because the resistance of the
switch is near zero.
A common bipolar transistor can be used as the
switch to form a simple inverter as shown in Fig.1 b. A
transistor works well in this application because it
can be turned off so that no current flows through it,
or it can be turned on to let current flow through it.
Recall that there are three basic operational states
of a bipolar transistor: cut off or non-conducting, conducting in the linear region, and saturation. Those
states are achieved by biasing (see Review of Diode
and Transistor Biasing). When the transistor is cut off,
it is non-conducting and acts as an open circuit.
With the proper bias on the transistor, it conducts
d.
Fig.2: a MOSFET inverter
(Qt) using a MOSFET (Q2)
as a load in place of a
power-consuming resistor.
flJ•--.::.1•1,-:.m
INPIIT ..
in the linear region. This means that the collector current is directly proportional to variations in the base
current. That permits a small base current to control a
large collector current and thus cause amplification to
take place. The linear conducting mode is not generally used in digital electronics.
If sufficiently high bias current is applied to the
base of the transistor it will conduct hard and act as a
very low resistance. During that time both the emitterbase and base-collector junctions are forward biased.
The voltage drop between the collector and emitter at
that time is extremely low; therefore, the transistor
appears to be a virtual short circuit. When in saturation, the transistor acts as a closed switch.
Using those principles, the operation of the inverter
is easy to understand. If the input to the inverter in
Fig.1 b is 0V or ground, the base-emitter junction of the
transistor will not be forward biased. No current will
flow through Rl or the transistor. The transistor thus
appears to be an open circuit. Therefore the output is
+ 5V or binary 1 as seen through Rl.
When a binary 1 or + 5V signal is applied to the input, the base-emitter junction is forward biased. The
value of resistor R2 is made low enough so that the
base current is high enough for the transistor to
saturate. During this time, the transistor acts as a
very low resistance. A typical output voltage between
collector and emitter might be 100 millivolts (100mV).
This is sufficiently low so as to represent a binary o.
Metal oxide semiconductor field-effect transistors
(MOSFETs) can also be used to form an inverter as
shown in Fig.2. Here N-channel enhancement mode
MOSFETs are used. Ql is the inverter switch while Q2
acts as the load resistor. This technique is widely used
in N-channel MOS (metal oxide semiconductor) integrated circuits. Transistor loads are easy to make in
integrated circuit form and also take up much less
space than an integrated resistor.
An enhancement mode MOSFET may also act as a
switch. When its gate voltage is below some threshold
voltage (about + 1.5 volts in common N-channel
MOSFETs), the transistor is cut off. It acts as an open
switch. When a positive logic signal above the
threshold value is applied to the gate, the transistor
conducts; therefore it acts as a closed switch.
The operation of the inverter in Fig.2 is simple.
When the input voltage is binary 0 (near 0V), transistor Ql does not conduct. Q2, however, is conducting
because it is biased on. The output voltage is,
therefore, + 5V as seen through Q2.
When the input voltage is a binary 1 level or approximately + 5V, Ql conducts. It acts as a very low
resistance; therefore, little voltage is dropped across
it. The output voltage is near 0V or binary 0.
AND
and
OR
Gates
AND and OR gates can be constructed with diodes
and resistors. For example, a simple OR gate is illustrated in Fig.3. If both inputs to the OR gate are
binary 0 or ground, neither diode conducts and no current flows through resistor Rl. The output, therefore,
is at 0V or ground as seen through Rl.
If both inputs are binary 1, both diodes D1 and D2
conduct. Current flows through resistor Rl. The output, therefore, is a binary 1. Most of the voltage applied to the inputs will appear across Rl except approximately 0.7V which is dropped across each diode.
With a + 5V input, the output would be approximately
+4.3V.
If one input is binary 0 and the other binary 1, the
output will also be binary 1. For example, if input A is
+ 5V and input Bis 0V, diode D1 in Fig.3 will conduct.
The output will be approximately + 4.3V. That will
cause diode D2 to be reverse biased and it will be cut
off.
A simple discrete-component AND gate is shown in
Fig.4. If both inputs are binary 0 or ground, both
diodes D1 and D2 conduct. Current flows through Rl.
The output voltage at that point is the voltage drop
across the diodes. For a typical silicon diode, the
voltage drop will be approximately 0.7V. That is a lowlevel voltage and represents a binary 0.
If one input is binary O and the other is binary 1, the
output will also be binary 0. For example, if input A is
binary 0 and input Bis binary 1 or + 5V, diode D1 conducts. The output will be approximately + 0.7V. This
means that diode D2 will be reverse biased and,
therefore, cut off.
If both inputs are binary 1 or + 5V, both diodes conduct. The output will be + 5V less the voltage drop
D1
e--------c
INPUTS
02
A B
OUTPUT
R1
C
,, ,, ,,,
0
0
0
0
0
...
Fig.3: simple diode
OR
gate and its truth table.
+12V
R1
01
A 8
A
INPUTS
C
OUTPUT
02
r...
B
Fig.4: diode
AND
C
,, ,, ,
0
0
0
0
0
0
0
gate and its truth table.
JANUARY 1988
87
across the diodes. If the inputs are + 5V, then the output will be + 4.3V or binary 1.
If both circuits are as shown in Figs.3 and 4, additional diodes may be added to accommodate more inputs as needed. Furthermore, those simple circuits
can be combined with inverters to implement almost
any logic function. However, discrete component circuits take up a lot of space and are inconvenient to
construct. Their performance is also generally poor.
For that reason, they are used only where simple noncritical circuits are needed.
+5V
INPUTS
OUTPUT
C = A.ii
00
Digital Integrated Circuits
Virtually all pieces of digital equipment are built
these days using integrated circuits. An integrated circuit is one in which all the components - including
transistors, diodes, resistors and capacitors - are
fully formed and interconnected on a tiny silicon chip.
Many inverters, logic gates, flipflops, and other logic
and linear circuits can be contained within a small
area.
A typical silicon chip is roughly square, with sides
of approximately 2.5 to 6mm. The smaller chips contain several gates or inverters while the larger chips
might contain a complex circuit such as a
microprocessor. The chip is encapsulated in a special
package with leads that can be plugged into a socket
or soldered to a printed circuit board. The most
popular form of package is the dual-in-line package, or ·
DIP (see Fig.5), which may have 8 to 64 pins.
Digital integrated circuits are generally divided into
four basic categories: SSI, MSI, LSI and VLSI. Those
designations, described in Table 1, show how digital
Fig.5: dual in-line package
(DIP) for integrated circuits.
OUTPUT
:::::[3o---c
~
= TI
NANO
TRUTH TABLE
A
B
C
0
0
D
1
1
1
0
1
1
1
1
D
~
Fig.6: simplified TTL NAND gate circuit (a), and its
schematic symbol (b) and truth table.
!Cs are classified according to size, density and
function.
Digital !Cs are also classified by the type of transistors used in their circuitry. The two basic types are
bipolar and MOSFET. IC manufacturers have
developed a wide range of digital IC families using
both types of transistors. Typical bipolar families include resistor-transistor logic (RTL), diode-transistor
logic (DTL), transistor-transistor logic (TTL), emittercoupled logic (EGL), integrated-injection logic (I2L) and
several others.
RTL and DTL aren't used any more in new designs,
but you may occasionally find them in older equipment. TTL and EGL are widely used today while I2L
circuits are common in LSI and VLSI designs.
MOS logic families include P-channel and Nchannel MOS and complementary MOS (CMOS).
Because bipolar circuits are larger and consume more
power, they take up more space on a silicon chip and,
therefore, are used primarily for SSI and MSI circuits.
Most LSI and VLSI circuits are MOS or CMOS.
In this lesson we are going to talk about the most
popular forms of logic today, TTL and CMOS.
Transistor/Transistor Logic
TABLE 1
LEVEL OF ICs BASED ON CIRCUIT DENSITY
SSI
MSI
LSI
VLSI
88
Small-Scale Integration: Chips containing
12 or less gates, inverters, flipflops etc.
Medium-Scale Integration: Chips containing
12 to 100 gates, inverters, tliptlops etc,
usually connected as functional circuits that
do something such as counters, registers,
decoders, multiplexers, and many others.
Large-Scale Integration: Chips with 100+
gates, tliptlops etc, often forming complete
circuits such as microprocessors, pro.gram
and control circuits, and many others.
Very Large-Scale Integration: Chips with
1000+ gates, flipflops and other circuits
such as 32-bit microprocessors, data
acquisition systems, gate arrays and much
more.
SILICON CHIP
Probably the most popular form of SSI and MSI
digitial ICs is transistor/transistor logic (TTL). TTL is
used in everything from personal computers to the
most advanced avionics equipment.
TTL circuits use bipolar transistors and operate on
a power supply voltage of + 5V DC.
The basic TTL logic circuit is illustrated in Fig.6.
That particular circuit performs the positive logic
NAND function. However, other versions are available
to perform the AND, OR and NOR functions . A single input version of the circuit is used as an inverter.
The circuit has three parts: a multiple emitter-input
transistor fQl), a phase splitter transistor (Q2), and
the output stage (Q3 and Q4}. Refer to Fig.6a. Transistor Qt and Rt function as a simple diode AND gate
where the emitter-base junctions of Qt are diodes.
The main purpose of phase splitter Q2 is to furnish
complementary logic signals to the two output transistors Q3 and Q4.
Q4 is the output switching transistor and performs
the function of an inverter while Q3, along with Dl
and R4, forms an active pull-up stage. It is similar in
operation to the MOSFET load resistor described
earlier.
Some TTL circuits are available without the active
pull-up stage. Q3, Dl and R4 are eliminated and the
collector of Q4 is brought out to one of the DIP pins. An
external load must be connected. Open collector circuits are useful for driving components such as LED
indicators, relays and other external circuits.
In most cases the active pull-up circuit is preferred,
because it represents a very low impedance when the
output of the gate is binary 1. That permits the circuit
to quickly charge any external capacitance, thereby
greatly reducing the rise time and speeding up the
circuit.
The logic levels for the typical TTL circuit are 0V to
+ 0.8V for binary 0 and + 2.4V to + 5V for binary 1.
Now let's see how the TTL circuit functions.
Remember that it is a NAND circuit. You can refresh
your memory about how it works by referring to the
truth table in Fig.6b. Assume that either or both inputs
A and Bare at ground or binary 0. The corresponding
emitter-base junctions of Ql then conduct through Rl.
When Qi is conducting, it pulls the base of Q2 to
almost 0V and so Q2 is cut off.
As a result, base current is supplied through R2 to
Q3 which conducts. Transistor Q4 is cut off at that
time. The output voltage will be + 5V less the voltages
dropped across R4, Q3 and Dl. This output voltage is
typically in the + 2.4V to + 3.6V range.
If both inputs are binary 1, the base-emitter junctions of Ql do not conduct. However, the basecollector junction of Ql does conduct and provides
base current to Q2 and through Q4. Transistor Q4
saturates and effectively brings the output to near
ground level.
The most popular form of TTL is the 7400 series
which provides of all of the commonly used logic
functions.
The individual ICs are usually labelled with the
manufacturer's logo, the device type number, and a
REVIEW OF DIODE AND TRANSISTOR BIASING
Diodes and bipolar transistors are made by combining
N- and P-type semiconductor materials (silicon, germanium, gallium arsenide) to form junctions . A PN junction creates a diode.
CATHODE
®
If the base-emitter junction is forward biased and the
base-collector junction is reverse biased, the transistor
conducts. This is the normal condition for a transistor
operating in the linear region for amplification.
In logic and switching applications, the bias arrangements shown below are used . Here the transistor
is used as a switch to turn on an incandescent bulb.
ANODE
The diode symbol (above) is used in schematic
diagrams.
The current flowing in a diode depends on its bias, an
externally applied voltage. The circuits show the two
ways to bias a diode.
01
n
+
T
T
I
I
....L.
'I
.J..
'T'
I
I
Rl
....L.
REVERSE BIAS
(NO CURRENT FLOW)
FORWARD BIAS
(CURRENT FLOWS)
C )l
(a)
""T""
I
I
Rl
.L
+
(b)
(a)
If the cathode (N-type material) is made negative with
respect to the anode as shown at A, the diode is forward biased and it conducts. The amount of current
flowing is controlled by the resistive value of R1 .
If the cathode is made positive with respect to the
anode as shown in B above, the diode is reverse biased. No curr-ent flows in the circuit.
Transistor biasing follows similar rules . An NPN transistor is illustrated below.
EMITTER
C
BASE (8)
I
!
)
~---tt-·----111 ~---1 +
(b)
...
If the input is grounded as in A, the base-emitter junction is not forward biased. Therefore , the transistor
does not conduct and the bulb does not light. If the base
is made positive as shown in B, the base-emitter junction is forward biased . The base-collector junction is
reverse biased so the transistor conducts and the bulb
lights.
If the base current is made high as determined by Rb,
the transistor will conduct hard. Its collector-to-emitter
resistance will be very low and only a small voltage will
appear between the collector and emitter. The collector
may only be +0 .1 V with respect to the emitter at
ground . With the base-emitter junction forward biased
and conducting , the voltage across it will be the same as
a conducting diode or about +o. 7V.
If the base is +0. 7V with respect to the emitter or
ground and the emitter is +0.1 V, then the base is
positive with respect to the collector. This means that
the base-collector junction is forward biased also. This
condition is caused by high base drive. When both junctions are forward biased, the transistor is said to be
saturated. Saturated operation is typical in bipolar transistor logic circuits .
JANUARY1988
89
date code. Each of the TTL manufacturers such as TI,
Fairchild, Signetics, National Semiconductor, and
others, has its own special company symbol. The part
number designates the specific device. For example, a
7430 is a single 8-input NAND gate.
INPUTS
OUTPUT
A ~ A+B
B~
INPUTS
NOR
TRUTH TABLE
Propagation delay
A
B
C
Propagation delay is the time that it takes a logic
change at the input to propagate through the device
and appear as a logic-level change at the output (see
Fig. 7). For TTL circuits the propagation delays are
generally in the 2 to 30 nanosecond range and
operating frequencies up to 125MHz are possible.
0
0
1
1
0
1
0
1
1
0
0
0
INPUT----
Ip
Fig.7: propagation delay is defined as the time offset
between input and output logic level transitions.
Power dissipation is another important parameter.
The lower the power consumption, the better.
However, the faster the circuit, the more power it consumes. Most common TTL circuits have a power consumption in the 1-25 milliwatt (mW) range per gate.
Going faster
Some TTL circuits use Schottky diodes to speed up
circuits while reducing power consumption. Essentially, each transistor in the circuit has a Schottky diode
connected between the base and collector as shown in
Fig.B.
OR
Fig.8: schematic
diagram of a
Schottky
transistor.
When saturated transistors are used in an IC, it
takes a finite amount of time for the circuit to turn off.
That condition, known as charge-storage puts a limit on
the speed of operation. However, if a Schottky diode is
used, saturation does not occur and there is no charge
storage problem. As a result, switching speeds are
faster and propagation delays are lower. However,
standard Schottky TTL circuits have relatively high
power consumption.
The most popular TTL circuits today are the socalled low-power Schottky devices that have propagation delays as low as two nanoseconds. Those ICs are
designated by an LS in their part number (ie, 74LS20).
90
SILICON CHIP
W
00
Fig.9: schematic diagram of a CMOS NOR gate (a), and
its schematic symbol (b) and truth table.
Complementary MOS
Ip
DIOOE
PREVENTS
SATURATION
S = SOURCE
G = GATE
D = DRAIN
Another popular family of SSI and MSI logic circuits is complementary MOS or CMOS. CMOS circuits
use both P-channel and N-channel MOSFETs, thus the
prefix C for complementary.
The power supply voltage is typically + 5V,
although most CMOS circuits can operate reliably
with supply voltages in the + 3V to + 18V range.
Fig.9a shows the basic CMOS logic gate which performs the NOR function as indicated by the symbol and
truth table in Fig.9b. Note that Qt and Q2 are Pchannel MOSFETs while Q3 and Q4 are N-channel
MOSFETs. All four transistors are enhancement-mode
MOSFETs meaning that the transistor is normally off
until the threshold gate voltage is exceeded with a
logic input signal.
Now let's see how that CMOS NOR circuit operates.
Assume logic levels of 0V and + 5V for binary 0 and
binary 1, respectively.
Keep in mind that in order for an N-channel
MOSFET to conduct, its gate voltage must be positive
with respect to its source. Usually the threshold value
is approximately + 1.5V. Any input voltage greater
than that will cause the transistor to conduct. Otherwise, the transistor will be off. In P-channel
MOSFETs, the gate must be made negative with
respect to the source. Again, the threshold value must
be observed.
Referring to Fig.9a, assume that both inputs A and B
are at 0V or at ground potential. Since ground is
more negative than + 5V, the gates are negative with
respect to the sources so both Qt and Q2 conduct. Q3
and Q4 will be cut off at that time, because their gates
are at 0V and below the threshold level. As a result,
the output will be + 5V as seen through Qt and Q2.
If either input A or B is binary 0 while the other is
+ 5V or binary 1, then either one but not both transistors Qt and Q2 will conduct. For example, if input
A is 0V and input Bis + 5V, Ql will conduct but Q2
will be cut off. If input Bis binary 1, Q2 will be cut off
but Q4 will conduct. With Q4 conducting, the output
will be binary 0.
With both inputs binary 1, both Ql and Q2 are cut
off. However, both Q3 and Q4 will conduct, keeping
the output at binary 0. The truth table sums up all
possible conditions of inputs and outputs of the NOR
gate. Naturally, additional inputs and transistors may
+5V
+5V
+5V
1k
IN
(b)
(a)
Fig.11: using a 7401 open-collector 2-input NANO
integrated circuit as a NANO (a), and as an inverter LED
driver (b).
(b)
.,.
(al
Fig.to: schematic diagram of a TTL quad 2-input NANO
gate (a) and a logic circuit made from the quad sections
of a 7400 IC (b).
be added to create gates with 3, 4 or 8 inputs.
CMOS ICs are very popular because of their very
low power consumption. The only time current really
flows in the circuit is while the output switches from
one state to the another. The power dissipation of a
typical gate is in the 10-nanowatt range. This is very
low power consumption and makes power supplies
simpler and cheaper, and heat dissipation from the IC
practically non-existent.
Even though low power consumption is the primary
virtue of CMOS circuits, that does not mean that they
are necessarily slow. They are typically slower than
TTL circuits, but fast enough for many applications.
Typical propagation delays are in the 10 to 50 nanosecond range.
Another advantage of CMOS circuits is their high
noise immunity. That means they essentially ignore
any extraneous signal, pulse, glitch or undesirable input. As a result, CMOS is excellent for use in industrial and automotive applications where high noise
is common.
The two most popular lines of CMOS circuits are the
RCA 4000 series and the Motorola 14000 series. Both
have a wide variety of gates, flipflops, inverters and
functional logic circuits such as counters, registers,
multiplexers, decoders and others.
Using Logic Gates
Fig.10 shows how TTL gates are used. Fig.10a illustrates a common TTL IC, the popular 7400 quad
SHORT QUIZ ON DIGIT AL FUNDAMENTALS - LESSON 3
7. Logic circuits using both N-channel and P1 . In logic circuits, the transistor is used as a:
a. resistor
c. switch
b. diode
d. capacitor
2. When both junctions of a bipolar transistor are
forward biased, the transistor is said to be._ _ __
channel MOSFETs are called _ _ __ _ MOS.
8. An enhancement mode N-channel MOSFET has
a threshold of + 1 .5V. The gate voltage is +0. 7V
with respect to the source. The MOSFET is:
a. cut off
b. conducting
3 . To save space on an integrated-circuit chip, a
____________ is used as a pull-up
or load in a MOS inverter.
9. The most popular form of TTL has high values
of circuit resistors and uses diodes between the
base and collectors of the transistors to prevent
saturation . This kind of TTL is called _ _ _ .
4. The basic TTL gate performs which logic
function:
b. NANO
a. AND
10. The primary advantage of CMOS is:
a. low cost
b. low propagation
c . low noise margin
delay
d. low power
consumption
c. OR
d. NOR
5. The inputs to a 7 400 TTL gate are +0 .1 and
+3.8V. The output will be:
a. binary O
b. binary 1
c. no change
d. not enough
information
6. Which of the following is not a type of bipolar
logic?
b . ECL
a. NMOS
d . DTL
c . RTL
11 . TTL is slower than CMOS.
a. True
b. False
AJBU!q ·q ·g
as1ei ·q · ~ ~
UO!tdwnsuoo J8MOd MO( ·p ·0 ~
A}IHOlfOS J8MOd MO( .6
JJO lOO '8
AJBlU8W8fdWOO .L
SOv'JN ·e ·g
ON\fN ·q
·v
(JOlS!SUBJl
l08ij8 Pl8!! JOlOriP,UOO!W8S
ap1xo 1etaw) 1 3.:ISOv'J ·8
pateJntes · c
40l!MS ·O . ~
S~3MSN'1
JA N UA RY 1988
91
2-input NAND while Fig. lOb shows a typical logic circuit using it.
Note that unused inputs should be connected
together and to the supply voltage via a resistor to
avoid extraneous input signals.
Fig.11 shows another IC circuit application, using a
7401. This is similar to the 7400 in that it is a quad
2-input NANO. However, the outputs are all open collector, meaning that they require an external load or
pull-up resistor. The pull-up resistor is shown in
Fig.lla.
Fig.llb shows how the gate is used as an inverter
and LED driver. The output load is a LED with a
resistor to set the current value. When the input is low
(binary 0), the output is high and the LED is off. If the
input is high (binary 1), the output is low and the LED
turns on.
A CMOS circuit application using a 4001 quad
2-input gate is shown in Fig.12. With two of its inputs
wired together a gate becomes an inverter (Fig.12b).
Two gates wired as inverters can be connected to
form a simple astable multivibrator, usually called a
clock circuit (Fig.12c). The output is a continuous rectangular pulse train with frequency determined by the
values of resistance and capacitance in the circuit.
With the values shown, the output frequency is F =
Did you
•
llllSS
+5V
~=~
2
(b)
JUUUl
f
=
1/2.2RC
(C)
(a)
Fig.12: a CMOS 2-input quad NOR integrated circuit is
shown in (a). With the two inputs tied together (b) the
gate becomes a simple inverter that can be used for the
pulse generator shown in (c).The numbers indicate the
pin termination in (a).
1/2.2RC, where R = lOk0, and C = l000pF, and the
frequency is 45,454Hz or 45.454kHz.
~
Reproduced from Hands-On Electronics by arrangement.
Gernsback Publications, USA.
©
these issues?
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November 1987: Your House
Wiring Could Kill You; 1GHz
Digital Frequency Meter; Car
Stereo in Your Home;
Capacitance Adapter for DMMs
December 1 98 7: High-Power
Amplifier Module; Building an
AT-Compatible Kit Computer;
Passive lnfrared Sensor for
Burglar Alarms; Universal
Speed Control and Lamp Dimmer; 24V to 12V Converter.
Price: $5.00 each (incl. p&p). Fill
out the coupon at left and send
to:
s,ucoN
CHIP, PO Box 139,
Collaroy Beach, 2097.
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SILICON CHIP
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technology.
SILICON CHIP is starting off as an independent
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establish the highest possible standards for accuracy and attention to detail. We also wanted
complete editorial freedom. Every article you see
in this magazine has been carefully selected and
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Similarly, our circuit and wiring diagrams have
been very carefully laid out by our draughtsman
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Regular Features
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ASK SIUCON CHIP
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and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097.
Noisy transformer
in amplifier
I have recently completed an
amplifier kit whose design I am
sure you are familiar with. Unfortunately, the substituted dual Ccore transformer radiates a
magnetic field which I presume is
responsible for an audible hum
through the loudspeakers, slightly
louder on the left than on the right,
and constant regardless of advancing the volume, treble or bass
controls.
The hum is present with and
without inputs plugged in. Is there a
safe way of shielding the
transformer and would this be
responsible for the noise? [G.M.,
Maroubra 2035).
• We know of only one amplifier
currently being supplied with a Ccore transformer. Strictly speaking
though, it has only one core which
consists of two C-cores held
together by a Utilux hose clamp.
The transformer in question should
be very quiet and it is highly likely
that it is not at fault at all.
The most common problem in today's low noise amplifier designs is
earth loops. There should be only
one connection from the amplifier
circuit to the chassis. If there is an
additional earth connection which
may be caused by a short from the
outer connection of the RCA phono
socket to the chassis, there will be a
constant low level hum which is independent of control settings.
Apart from a careful visual inspection, the way to check for the
presence of an earth loop is to
disconnect the main earth from the
amplifier circuitry to its chassis.
Then switch your multimeter to a
low Ohms range and check for continuity between the amplifier circuit and chassis. There should be
none. From then on it is a matter of
visual detective work to see where
the short is occurring.
If the above checks still bring no
joy and the amplifier still hums, you
can still check whether the
transformer is the cause. All you
have to do is to remove the
transformer from the chassis while
still leaving it connected. You may
have to extend some of the leads to
enable the transformer to be positioned outside the chassis.
Now turn on the power and listen
carefully to the hum to see if it
varies with orientation of the
transformer. You may find that
there is a null in the hum output
with the transformer mounted at
Wants Leak circuit diagram
Some time ago, I was given
some quality valve audio equipment. It was being taken to the
local tip and a friend thought it
may be of interest. It turned out
to be a Leak amplifier. So now I
am the proud owner of a Leak
"Stereo 20" plus the "Varislope
Stereo" preamplifier to go with
it. As it turned out, replacing ~he
various coupling and filter
capacitors gave me a perfectly
functional unit.
This brings me to my problem.
I am trying to find a source of the
circuit information on this equip94
SILICON CHIP
ment, particularly of the
preamplifier. Could you suggest
anyone with this information? I
know the gear was imported into
Australia from England around
1960 by Simon Gray Pty Ltd.
However the company doesn't
exist any longer. [J.Sweet, 91
Anne Street, Aitkenvale, Qld
4814).
• Alas, we know of no source of
the circuit information you require. We have printed your
name and address in the hope
that one of our readers can help
you.
right angles to its present
orientation.
As far as your question about
shielding is concerned, it would be
difficult to shield the whole
transformer. However, it might be
practical to install a copper strap
over the winding assembly to
reduce any stray leakage flux.
Once again though, we don't
think the transformer would be the
problem. We suspect an earth loop.
Wants timer with
remote display
I hope you can help me with my
problem. I am attempting this project for a local sporting club. It
revolves around a three-decade
programmable timer. I am fairly
confident I can design the timer
myself but I also need a remote
display some 30 to 40 metres away
from the counter itself.
How do I keep the cable stranding to a minimum? What problems
will affect the digital signal over
such a long run? Should I have a
separate 5V supply at the remote
display? What is the cheapest and
simplest way?
I have tried to find books and articles on the subject of data
transmission but most of it applies
to computers and such with
transmission distances of no more
than 5 to 10 metres. I thought of trying multiplexers, D-A and A-D converters or maybe UARTs. I hope you
can help me. [R.O'G., Rockhampton,
Qld).
• Had you asked about a 3-digit
timer without the need for presetting we would have said that it
would be easier to have an additional remote timer so that only
three leads would be necessary in
the long cable; ie, + 5V, clock signal
and 0V.
Since you need presetta ble
counters [this letter was accompanied by a suggested schematic involving three 4029s, three 4511s
Ribbon or coax: which is best?
All of the information I have
read about UHF antennas in
Australia recommends the use of
75-ohm coax cable and most of
the installations I have seen in
this country have used coax. But
I have been overseas to the US
and Japan on a number of occasions and there they seem to use
ribbon cable frequently. Why is
tha~? Why is there such a
preference in Australia for
coax? I can't believe that our
reception conditions for UHF
would be any more difficult than
in cities in Japan and the US.
• We doubt whether UHF
reception conditions are any
more difficult in Australian
cities than overseas. Based on
typical attenuations figures at
UHF for ribbon cable and coax
cable, you might think that ribbon would be the more desirable.
After all, most coax cables have
losses of 10dB/30m or more at
UHF which is considerably more
than the nominal losses of
la.dder-type ribbon cable but we
would not recommend ribbon
cable on that basis.
It is possible that in some
situations, 300-ohm ribbon cable
might give comparable reception
and three 7-segment displays), you
will need to run 12 separate data
lines plus the supply lines. That
makes it messy.
We don't think UARTs (Universal
Asynchronous Receiver/Transmitter) would be practical or cheap
since you would need two 8-bit
UARTs to send and another two to
receive, plus all the timing circuitry
required.
Nor would A-D and D-A conversion be practical or cheap because
that also implies quite a lot of supporting circuitry.
The only practical way seems to
be to send all 12 data lines via
RS232 receivers and transmitters.
We suggest you use the Motorola
MC1488 quad line driver and
MC1489 quad line receivers, both
of which are quite cheap. You
would need three to transmit and
quality to 75-ohm coax but you
could only justify its use in areas
away from the sea which don't
have high rainfall. Once ribbon
cable becomes wet or coated
with a salt film, it starts to produce much higher losses.
It deteriorates quickly too and
is subject to signal pickup on the
cable itself, producing leading
ghosts and smeary pictures.
As far as we are aware, coax
cable is universally used
throughout Europe for UHF
reception and the same can now
be said for the USA and Japan. It
is also true that many if not most
installations in apartment
buildings overeases would not
feed UHF signals via distribution
system to each tenant. The signal
losses, particularly in older installations using inferior cables,
would make it impractical.
Rather, it is standard practice
to feed the UHF signals to a
down-converter so that the
signals are distributed at VHF.
The message is: forget ribbon
for UHF. If coax cable losses are
.likely to be a problem, you should
use a masthead amplifier to
boost the signal before it is
distributed.
three to receive. You will also need
± 12V supplies for the transmitters
in addition to 5V for the remote
display.
We admit that our suggested
solution does not look simple,
but it is probably the cheapest way.
Corrections
Digital Fundamentals, Dec. 1987:
Fig.6 on page 92 has been reproduced incorrectly. The type down the
left-hand edge of the diagram
should read INPUT A, INPUT B, INPUT
C and OUTPUT D. In addition, the second last paragraph on page 92
should read as follows: At times t 1
through ta the three inputs are
never high at the same time.
However, beginning at time ta and
ending at time t 9 the three inputs
are all high so that output D goes
high.
Subcarrier Adaptor
continued from page 67
setting up procedure is relatively
simple.
First, make sure that VR1 is set
so that its wiper is turned toward
the LM565. This will provide maximum signal level. Now adjust VR2
so that there is audio signal. Find
the extreme settings of VR2 where
the audio signal drops out, then set
VR2 halfway between the two
extremes.
VR1 is used to minimise noise
from the audio signal when the FM
signal level is poor. Adjust the trimmer until the sound becomes
distorted and then back off the adjustment until distortion is no
longer audible. If you have a strong
FM signal, adjustment of VR1 will
have no effect on the noise level and
so it should be left at its maximum
resistance setting.
UHF Antenna
continued from page 21
enable you to terminate cables from
your VHF and UHF antennas. A
single cable goes from the diplexer
to your TV set. Alternatively, the
diplexer output may be fed to a
splitter and then to various TV wall
plates around your home.
Tune your TV to the local UHF
station(s) and then orient the antenna for best reception.
Secure the cable to the mast with
plastic cable ties to prevent the
cable from flapping in the wind.
Seal the balun box with silicone
sealant to weatherproof it.
Painting
Depending on where you live,
painting the antenna cart be worthwhile, particularly in seaside
areas or near industrial areas
where there may be a lot of fallout.
In these cases, we suggest painting
the antenna with an etch primer
and then finishing with an
aluminium loaded paint such as
British Paints "Silvar".
As a final comment, if you are
building the antenna to receive stations right at the top of band V, say
between channels 59 and 69, a
small improvement can be gained
by shortening the dipole elements
by 5%.
JANUARY 1988
95
CENf
Cash in your surplus gear. Advertise it here in Silicon Chip.
plete kit featuring a dual mechanical VU
meter. Easy to assemble; the meter is
soldered directly to the printed circuit
board. Any audio signal can drive it
since its sensitivity is adjustable from
volts right down to 3mV! Can double as
a microphone preamplifier. Features
optional backlighting ; incandescent
lamps provided in kit. This unit is inexpensive at its normal price of $1 7. 90,
however during January you can buy it
for only $9-95 (p&p included)- Yes it is
a bargain; at this price you can afford
to build one into every piece of audio
equipment you own .
UHF Remote Controlled Key (Jan. 86
EA). A proven and reliable wireless
remote switch; 1 000s sold! Has more
than 13,000 possible code combinations. Multiple outputs and an on-board
off-on indicator enable this unit to
remotely switch car burglar alarms, car
central locking systems, home burglar
alarms, etc. The small transmitter also
has provision for a key ring . Our
special January package includes 1 x
transmitter PCB kit, 1 x transmitter
plastic case with battery clips and
pushbutton switch, 1 x miniature 12V
alkaline (lighter) battery, and the
complete receiver PCB kit for only
$39.95 including pack and post. Yes,
FOR SALE
0.25W RESISTORS: only 1 .5c each!
Values from 4 .7n to 2 .2MQ (E12
range) . $1.00 postage. Send for free
samples! Steven Fox, PO Box 4, South
Bexley, NSW 2207 .
NEARLY 1500 printer buffer kits now
sold. Prices start at $39 for a 256K
short form kit. All items advertised are in
stock. Dealer enquiries welcome. Bulk
discounts. Schools, Govt. Depts.
orders accepted . Oh yes !!, IBM compatible . Austral ian designed and
manufactured. Ideal project for user
groups or students. For a free catalog
send a 37c stamp to: Don McKenzie,
29 Ellesmere Cres., Tullamarine 3043.
ELECTRONIC components cheap . Example : 100 5mm LEDs - 34 Red, 33
green, 33 yellow - $12.00. Free post
and pack. LMF Products, PO Box 384,
Cootamundra, NSW 2590 .
OATLEY ELECTRONICS - for exclusive and selected kits. Here we
present our January specials:
Stereo VU Meter (June 87 EA) . Com-
Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents
for each additional word ; Display ads (casual rate) - $20 per column centimetre (max.
10cm).
Closing date: five weeks prior to month of sale. If you use a PO Box number, you must
include your permanent address and phone number for our files. We cannot accept ads
submitted without this information .
To ru n your own classified ad, put one word on each of the lines below and send th is form
with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach , NSW 2097.
PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS
2
3
4
5
6
7
8
9
10
11
12
13
14
15 ($7 .00)
16 ($7.40)
17 ($7.80)
19 ($8 .60)
20 ($9.00)
18 ($8.20)
Name ········ ·•··· ···· ··· ········· ······ ······ ··•·· ····· ·· ····· ·
Address
···· ··· ········· ··· ··
Suburb/Town
Enclosed is my cheque or money order for $ ........ ..... ..... ..... .
Bankcard D
Visa D
Card No.
Signature .. ... .
96
SILICON CHIP
Postcode
. . . . . or please debit my
that's everything you need and yes,
it's dirt cheap!
Satellite Siren (Sept. 87 EA). Add the
protection of this complete second
alarm system into your existing alarm
system. Automatically gain the benefit
of back-up battery operation and a complete and remotely placed second
alarm system! This unit is simple to install; it requires only two connections to
your existing alarm system. Unit is activated when the main alarm is vandalised, the main alarm power is interrupted,
or the vehicle battery is disconnected.
We now offer a short form kit for the
"Satellite Siren" . What's in this kit? - 1
x PCB and components kit, 1 x battery holder, 1 x barrel keyswitch with
two keys, and a plastic case. All this
for only $29.00 including pack and
post. So what else will you need later to
complete the unit? - 4 x AA nicad batteries at $3 .00 each and 1 x 12V piezo
siren at $16 each. Yes , all these prices
are unbeatable!
In the New Year our shop will re-open
on Monday 18/ 1 /88 (gone fishing) and
we will process our mail backlog on the
same day! Happy New Year!
Mail address: Oatley Electronics, PO
Box 89, Oatley, NSW 2223.
Shop address: 5 Lansdowne Pde,
Oatley West, Sydney, NSW 2223.
Phone (02) 579 4985.
To obtain a list of our kits and ready
made products send us a selfaddressed envelope (8cm x 21 cm) or
ask us to include it with your purchase.
Advertisers Index
Our advertisers are vital to the
success of SILICON CHIP. Please
give them your support.
. 26-31
Altronics . .
Arista Electronics .
. . 84
Australian Geographic ..... IBC
Dick Smith Electronics . ... 8,9 ,
36,54 ,55,75
IFC
Elmeasco
. 61
Geoff Wood Electronics .
.. 44-47
Jaycar Electronics ..
. . 96
Oatley Electronics .
.. 81
RCS Radio . .
. . 35
Scan Audio Pty Ltd .
~~~ ~;
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