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Floppy Disc Drives: Formats & Options S3.50 NOVEMBER 1989 NZ $4.95 ~~CTL David Reid Electronics DIDJA * ~ - -c_ o _M _ PUTER BUFFS CAN 5.25" D.S.D.D. DISKS QUICK MOUSE MICROSOFT COMPATIBLE was $99.95 I ~ BE QUICK!!! ::~: '------wlllilll_ _ _ 1~_ NO NAME BRAND PKT-10 ,, NOW 1':11 $26.50 ✓ ✓ HANDYMEN CAN NOW ONLY NEW! ARLEC "COMMANDO" CAR ALARM SYSTEM SOPHISTIC A TED ELECTRONIC CAR ALARM SYSTEM FOR YOUR VEHICLE ,,,1sy -to -follow comp,et.ecs,,c • ]1,vo H!lllO!l' • Ultr; 1so111c sensor pro tt'cls 1ns1de of vehicle • • • • • $399.00 Includes visor bracket. e ANYBODY CAN ARLEC DIGI-SCALE • DIGl·SCALE will measure from 1 gram or 0.1 ounce up to 2kg or 41b 4oz. • Convert from grams to ounces or ounces to grams using a sel ected key. • Various items can be individually weighed in the same container using the reset key. • 240 volt (plugpack not supplied) or battery operated. • 12 months warranty. $75.00 --,.--....-.. MOTORISTS CAN BEL MICRO EYE "VECTOR" RADAR DETECTOR SAVE $100 NOW ONLY No more cords • Fully portable! Gas Soldering Iron , Blow Torch, Hot Blow, Hot Knife. REPLACFMENT TIPS • Tip temperature adjustable up to 400 deg. C. • Average continuous use: 90 minutes • Display: 3.5 digit LCD. • Ranges: AC/DC V, 1 OA AC/DC, Ohms, Capacitance, Transitor Test, Audible Continuity. • Includes probes and soft case. • 12 months warranty. This high spec. radar detector detects X and K band radar up to 13km's. Detects mobile radar equipment, not only picks up signals in straight lines but from just about any angle as well as around corners and over hills. $65.00 PORT ASOL "PRO" SOLDERING IRON KIT SEW ST-3501 DIGITAL MULTIMETER David Reid Electronics ONLY -- ." ' • Playing distance up to 1 5 feet. • Auto-fire switch; • Two fire buttons. • New improved grip handle. 3.5" D.S.D.D. DISKS f..)t NOW $89.95 Infra Red Joystick to suit Commodore/Atari computers NNAME l l oBRAND ~K~: • Tracking speed: 600mm/sec. • Resolution: 200 DPI. • Includes driver, test program and mouse pad . Qi,><:kMru.>,w,,~ !iii n:d 1nd1ec1tor C1rcu1t Door:; _ ho1111ut. boot mid sunroof protec tion l:nq111l' 1111mobd1s('r Gl,1ss wh e11 tt1c nlarrn • Automatic reset LHll~Jl'I prolt'cl1011 e 1 l 5db SHCll * IT'S KAREN'S BIRTHDAY THIS MONTH HAPPY BIRTHDAY KAREN! GIVE KAREN A CALL AND WISH HER A HAPPY BIRTHDAY AND RECEIVE 10% OFF YOUR ORDER (MAIL ORDER CUSTOMERS ONLY) ULTRA-SONIC CLEANER PLASMA DISPLAY • Ideal for cleaning drafting pens, watches , photographic filters, or even dentures. AMAZE YOU and YOUR FRIENDS • 240 volt operation. * 200mm BALL with internal microphone. ONLY ONLY $150.00 $150.00 127 York Street SYDNEY 2000 Ph: (02) 267 1385 MAIL ORDERS P.O. BOX 0103 SYDNEY 2000 FAX: (02) 261 8905 POST & PACK $5-$25 .... $4 $26-$50 ... $5 $51+ .... . $8 BUSINESS HOURS Mon-Fri 8.30-5.30 Thur 8.30-7 .00 Sat 9.00-1.00 NOVEMBER 1 989 FEATURES GOT A COMPUTER & a shortwave receiver? Link them together with our new Radfax Decoder and plot out weather maps, radioteletype transmissions & Morse code. See page 18. 76 Electronics For Everyone by Leo Simpson Pt.5: what you need to know about switches 90 Simple Program For Resistor Calculations by S. Payor You type in the value & the tolerance 92 The Evolution of Electric Railways by Bryan Maher Pt.25: the Pilbara iron ore railways PROJECTS TO BUILD 4 Build A Low Cost Analog Multimeter by Leo Simpson Fun to build, easy to use 14 Super Sensitive FM Bug by Greg Swain So small it fits in a matchbox 18 The Radfax Decoder by John Clarke Teams with your computer, decodes weather maps, RTTY & Morse 32 2-Chip Portable AM Stereo Radio by Steve Payor Pt.3: the alignment details 64 FM Radio Intercom For Motorbikes by John Clarke Pt.2: alignment & troubleshooting THIS SNEAKY .FM BUG is smaJJ enough to hide in a matchbox yet is super sensitive. We show you how to build it starting page 14. SPECIAL COLUMNS 8 Vintage Radio by John Hill The humble 4-valve receiver 40 Remote Control by Bob Young Modern radio control systems 46 Amateur Radio by Garry Cratt Two-tone test oscillator for SSB transmitters 48 Serviceman's Log by the TV serviceman You've got to be 'Sharp' in this game 68 Computer Bits by Jennifer Bonnitcha Floppy disc drives: formats & options 86 The Way I See It by Neville Williams Electronic identification: a boom or a catastrophe? DEPARTMENTS 2 Publisher's Letter 3 Mailbag 7 Subscription Page 61 Circuit Notebook 89 Back Issues 99 Product Showcase 108 Bookshelf 110 Ask Silicon Chip 112 Market Centre SUPER SLEUTH (alias the Serviceman) matched wits with a tricky VCR this month but eventuaJJy won ('cos he's briJJiant). The super sleuthing starts on page 48. AM Stereo Radio THIS MONTH, WE conclude construction of the AM Stereo Radio with the alignment details. The procedure starts on page 32. NOVEMBER 1989 1 SILICON CHIP Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann (02) 982 9553 Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill Jennifer Bonnitcha, B.A. 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 the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. TypesettiQ_g/makeup: Magazine Printers Pty Ltd, Rozelle, NSW 2039. Printing: Macquarie Publications Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: currently $42 per year ( 12 issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP PUBLISHER'S u·1-1ER Electronics for Everyone - anyone can learn This month I want to talk about our on-going series "Electronics for Everyone". We started this series in our March issue and I did not have a chance in that issue to introduce it. The thinking behind the "Electronics for Everyone" series is that there are plenty of textbooks and magazine articles where you can read about the basic theory of electronics. By contrast, this series is intended to be entirely practical. Many people get quite a good grounding in electronics by taking a technical college course or a correspondence course but when it comes to doing something practical they feel a bit lost. Then again, there are many people who want to get stuck right into the practical side of electronics without bothering too much about the theory side. Having spent more than my share of time hunched over textbooks, I can well understand that. The practical side is more fun. So to cater for this need to explain the practical side, we have started the series "Electronics for Everyone". In each episode we'll explain how you can recognise the different types of components and the jargon associated with them. So far, we've had episodes on resistors [March 1989), plastic and ceramic capacitors (April), electrolytic capacitors [May), potentiometers and trimpots [September) and this month, switches. One of the difficult aspects of writing the series is that it is hard to focus on what is confusing to a beginner. When you have been writing about electronics for more than 20 years, it is very easy to forget what was puzzling when you started out. To overcome this problem we try to have people who are just becoming involved in electronics read each episode. Even so, after each episode is printed it sometimes becomes obvious that there are some aspects we have missed or possibly not explained as well as they should be. For example, when we had finished the article on capacitor coding in the April issue we thought that we had the subject pretty well covered. Then we came across some capacitors with the value given according to the IEC code, such as 680n for .68µF, but with the tolerance as given by the EIA code, with G for 2%. We think that this mixing up of codes by the manufacturers makes it very confusing. You can help us with the future presentation of episodes of "Electronics for Everyone" by writing and suggesting topics to be covered. Perhaps you are a beginner in electronics and want a number of aspects explained. Don't be afraid to ask. Everyone has to start where you are now. Perhaps you have considerable experience but can recall some aspects of electronics which were confusing to you. Either way, you can help make the series as comprehensive as possible. Leo Simpson MAILBAG Magazines wanted I am the General Secretary of the International Radio Listeners Club in Bangladesh. Most of our members are electronics hobbyists and we are now trying to obtain government permission to re-establish amateur radio in Bangladesh. Our telecommunications minister advises me that there is little chance that we will obtain amateur radio licences until we pass the necessary examinations. Unfortunately, there are no electronics publications in our country. In view of this, we would be grateful if your readers could donate old copies of magazines or books so that we could increase our knowledge of electronics. We lost our library and many valuable books during the flood in our country last year. Taimw: Rahan Konabari, PO Nilnagor - 1346 Dhaka, Bangladesh Service information for electronic gear I would like to add a comment about your May editorial on the supply of service information for consumer electronics. The editors of SILICON CHIP could help considerably if they would adopt the policy of not reviewing products that are distributed by companies who will not make service information available, at least to competent technicians. For example, anyone who bought an Amcron amplifier as a result of your glowing review in the August issue would do so in the hope that future service would be backed up by adequate service information. Your magazine is in an ideal position to check this availability and to advise · potential buyers. There is no conflict with your own projects because full details are published in the magazine. Any problems with the Studio series amplifiers or accessories can be solved by reference to the original articles. Mr I. Morrison (Mailbag, August) points out that many products are obsolete by the time the warranty runs out and consequently service information is no longer available. Similarly, many companies refuse to supply replacement parts for products still under warranty to any serviceman who is not an approved " service agent". This policy defies Trade Practices laws by forcing consumers into a monopoly situation. Consumers should have the right to engage any serviceman they choose, even if this means that they have to forego their free repair under warranty. (One major Australian company does recognise any qualified serviceman for warranty repairs and has no restriction on the supply of service manuals to the industry). If you really support the supply of service information to either the service industry or to consumers, you would do well to add a couple of lines to your product reviews, setting out details of available information. If a would-be buyer knows that there is no service information available, yet goes ahead and purchases the product, then his future troubles are of his own making. Jim Lawler Geilston Bay, Tas Valve portables were really OK I too have been reading John Hill's articles on vintage radios with interest. However, I feel John may have a prejudiced view on valve type portable radios as he seems to dismiss them as almost not being worth preserving, impossible to power (or at least very expensive), awkward, too heavy etc. At least I got that impression. He may not like them but there are many who do and think that they were quite state of the art compared to other valved radios. I was a serviceman in the 50s and 60s and serviced many battery valve portables - and transistor ones too. I would like to make a number of points where I am at variance with John. (1). Batteries were expensive but lasted in general about 300 hours where the combination of a No. 745 "A" battery and 2 No. 482 45 volt "B" batteries were used. The life of SILICON CHIP, PO Box 139, Collaroy Beach 2097. the "A" battery when it was a No.739 · type wasn't as long. (2). The battery drain by most 5-valve sets using the 174, 185, 1T4, 185, 3V4 combination was about 1113mA, not 8-l0mA as John states; (3). Economisers for the batteries did not use a resistance in series with the filaments in any sets that I ever saw. They did very occasionally use a higher value resistor in the bias network for the 3V4 output valve to reduce its current drain. (4). There were very few miniature portables using valves for at least two reasons: (a) the batteries. Two D cells and a No. 467 67½ volt battery had a very short life in the sets and the cost of running sets with this combination of " miniature" batteries was quite high. (b) there was very little room for an efficient loop aerial alongside all the metal work in the set, therefore the sets had relatively poor performance - certainly almost useless in country areas. They were, however, relatively small sets, being the size of the medium sized transistor portable of today. (5). If you do want to flaunt your battery portable it is quite possible to build a DC-DC power supply to replace the batteries. I suggest a 12V 1.2A.h sealed lead acid battery as the supply. You would then need 1.5 or 9 volts for the "A" supply and 90 volts for the "B" supply. Allowing for 80% efficiency for the conversion, you would get about 9 hours out of the battery between charges. If it were made into a pack the size of the 45 volt battery, this could be conveniently swapped between sets. No, I don't have a design for such a supply - maybe SILICON CHIP could produce one. (6). Yes the portables did have large speakers in some cases and don't you prefer the sound they put out compared to many transistor radios? (7). I found that people did in general use their portables quite a bit just on batteries, although to some it certainly was just a novelty. (8). Now the valve portables were continued on page 107 NOVEMBER 1989 3 This is how the kit appears as you take it out of the box. The meter movement and front panel are one assembly. Note the resistors wrapped around a strip of cardboard. By LEO SIMPSON Build this low--cost analog multimeter Are you in the market for a low cost analog multimeter? You are? Why not put together this kit multimeter? You'll save a little money and learn about multimeters in the process of assembling it. If you are on a tight budget, a low cost analog meter may be just the ticket until you can afford a digital meter with all the bells and whistles. And even if you don't have budgetry constraints [lucky you), a low cost meter such as this is often handy to have in your glovebox or car toolkit. Perhaps you already have a digital multimeter and don't consider that you need an analog meter. Well, there are times when an analog meter is more suitable than a digital type. For example, if you are aligning a radio [such as the AM Stereo Radio described this month) an analog meter is much more useful when trying to obtain a peak reading. As another example, the "Ohms" range of an analog meter is useful for judging whether a capacitor is good or not. You can do this by seeing how the meter's pointer flicks up the scale when the capacitor is connected. 4 SILICON CHIP So while analog meters have been largely superseded by their fancier digital cousins, they are still handy in certain applications and where sheer accuracy is not required. For most of the time, you just don't need high accuracy. Meter features The meter in question is a fairly basic unit with the more or less standard DC sensitivity of 20,000 ohms/volt on the DC ranges. What this means is that the meter will draw a maximum of 50 microamps from the circuit being measured for a full scale reading. When measuring voltages in high impedance circuits, you have to take this "loading" effect into account. The DC voltage ranges are 2.5, 10, 50, 250 and 1000 volts. The AC voltage ranges are 10, 50, 250 and 1000V while the Ohms ranges are 10k0, 100k0 and 1MO. DC accuracy is 4% of full scale deflection while The board is supplied partially assembled with a fuseholder, capacitor, trimpot, the current shunt and the insulated hookup wires. AC accuracy is 5% of full scale deflection. DC current ranges are 5mA, 50mA, 500mA and 10 amps. As well, there is a continuity range [with internal buzzer) and two battery check ranges for 1.5V cells and 9V batteries (eg, Eveready 216). These ranges pull a current of 20mA from the battery under test so they give a quite useful indication of battery condition. Overall size is 135 x 90 x 40mm thick so the unit is small without being in the tiddler class. Now to put it together. Construction When you open the kit, you will find a bunch of parts in a plastic bag. These will include the meter test leads, two penlite cells, a piezo buzzer and the trimpot for the zero ohms adjustment. The printed circuit is supplied with a number of pieces of coloured hookup wire already soldered to it, as is the heavy gauge brass [?) shunt wire for the 10 amp current range. The range switch is part of the printed board pattern, as you will see when you have a look at it. Also included in the parts collection is a strip of cardboard with all the resistors and diodes wrapped around it. These resistors are numbered and the value is listed. The same goes for the diodes. Assembly of the resistors and diodes is then simply a matter of installing them according to the "R" and "D" numbers on the PC board. This is what the board looks like when you have installed all the resistors. Don't bend the current shunt while installing resistors under it. We put the diodes in first, noting that D1 was a germanium 1N60 type while the others were silicon 1N4148s. The cathode ends [where the diode arrow symbol points to) of the diodes are indicated by a black stripe on one end of the diode bodies. Then we put the resistors in. Finding the position for Rl on the board is tricky - it's underneath one end of the current shunt wire. The spring contacts for the rotary switch are fitted as shown here. The piezo buzzer is secured with two small self-tapping screws. RESISTOR COLOUR CODES This is the back of the meter with the assembled board in place. The mounting arrangement for the Ohms adjustment pot is a little crude - it is connected to short pieces of tinned copper wire which are soldered to the board pattern. Resistors R4, R5 and R6 interfere with a yellow wire which is labelled as J5 on the board. Push it out of the way while you install these resistors. R7 is tricky too, because you have to manipulate it in under the current shunt wire to install it. Don't bend the current shunt wire out of the way though - if you do, you could disturb one of the solder connections. When you come to R12 there is another fork in the road. Right next to R12 is another resistor position but it is unmarked - leave it vacant. R13 is over near trimpot R21. To help you identify the resistors we have listed them with their colour codes. Note that there are some very odd values included, values that are specially made as precision multipliers for multimeters. Incidentally, why are the range resistors called multipliers? The answer is that they 'multiply' the basic voltage sensitivity of the meter movement itself. When all the resistors are in place, their leads can be soldered and then cut flush with the board surface. Now you can turn your attention to the meter itself. It comes assembled with the meter movement and the switch rotor. You have to add the springy metal contacts to the rotor. One of the photos shows how they fit. You can also fit the piezo buzzer with the two small self tapping screws provided. Next, fit the Ohms adjustment pot to the printed 6 SILICON CHIP Resistor Value 5-Band Code (2% tolerance) R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 violet violet silver red violet red black silver red violet red black gold red violet white red brown red yellow red black silver red yellow red black brown red yellow grey violet red red yellow grey yellow red red brown green black orange red grey black black orange red yellow black black yellow red brown green black green red grey green blue red red orange green yellow orange red brown violet blue yellow red blue blue black yellow red grey orange black silver red orange black yellow red red yellow brown black black red 0.770 7.20 720 7.92k0 420 4200 48.7k0 48.4k0 150k0 800k0 4MO 15MO 85.6k0 354k0 1.76MO 6.6MO 830 30.4k0 4100 board. It is attached by short pieces of tinned copper wire to both end connections and to two of the middle connections, as shown in the relevant photo. The method is fairly crude but is identical to that in the fully assembled examples of this multimeter. Fit the thumbwheel knob to the Ohms pot using the small machine screw provided and then temporarily fit the board to the meter housing. Check that the thumbwheel protrudes through the meter front panel by the right amount, so that it can be easily operated. continued on page 107 And here's what it looks like when finished - a handy little meter with a useful combination of ranges. The two battery check ranges are particularly useful. New column on computer hardware SUBSCRIBE SUBSCRIBE SUBSCRIBE ' [t a fj Have SILICON CHIP delivered direct to your door at no additional cost. Each month, we '11 bring you the best and brightest electronics magazine, put together by Australia's most experienced team. • • • • • • !il{ Police radar: it's not always right !I InteUigenrcharger for 12V gel batteries CONSTRUCTIONAL PROJECTS AMATEUR RADIO VINTAGE RADIO COMPUTER BITS THE WAY I SEE IT INFORMATIVE ELECTRONIC STORIES ~----------~------------------------FREEPOST* 24 Hour Fax Service (02) 982 9553 Send the coupon with your Credit Card details. 24 Hours, 7 Days a week. SUBSCRIPTION COUPON □ □ New subscription Renewal Start in, _ _ _ _ _ __ Name._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Subscription Hotline Telephone (02) 982 3935 9am-5pm Mon-Fri and quote your Bankcard, Visa Card or MasterCard No. and expiry date . (PLEASE PRINT) Street,_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town, _ _ _ _ _ _ _ _ _ _ _ _ Postcode. _ _ __ 1 year (12 issues) □ $A42 Australia Detach Coupon and Mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 *No postage stamp required in Australia. 2 years (24 issues) □ $A84 NZ & PNG (airmail) □ $A65 □ $A130 Overseas surface mail □ $A62 □ Overseas airmail □ $A 1 20 0 $A130 $A240 Enclosed is my cheque/money order for $ _ _ _ or please debit my □ Bankcard Card No. I □ Visa Card I I I I i □ MasterCard I I I I I I I I I Signature _ _ _ _ _ _ _ _ _ Card expiry date _ _ / __ / _ _ NOVEMBER 1989 ~ ~ 7 VINTAGE RADIO By JOHN HILL • The humble 4-valve receiver In the past, valve radios were built in many forms; from simple home assembled units to huge affairs having a dozen or more valves. Just how many valves were needed to make a good receiver was a question that had many answers. Let's take a closer look. In the 1920s, the "bigger is better" syndrome was becoming evident and this period saw domestic receivers develop from simple one and 2-valve units to sets with five or six valves. By the mid 1930s, some upmarket radios had grown to incredibly large units having up to 15 valves. These multi-valve monsters were, in the main, quite unnecessary and in some instances only the heaters of certain valves were connected into the circuit. These extra valves served no useful purpose and were there only for show, making the chassis look impressive if nothing else. The buyer was paying for a lot of additional hardware that wasn't even being used! A domestic radio generally requires five valves, including the rectifier, if it is to be classified as a reasonable receiver. In fact, the 5-valve radio became the industry standard because it was such a This little Astor Mickey is a typical 4-valve radio receiver. Although not up to the standard of 5-valve receivers, 4-valvers were quite adequate for use with strong local stations. 8 SILICON CHIP practical size. A 6-valve receiver will allow a stage of radio frequency amplification while a 7-valve receiver can offer the additional luxury of a push-pull output (ie, two valves driving the loudspeaker instead of the usual one). Not many radios were built with more than seven valves. The 4-valve receiver After the 5-valve receiver, the next most popular set was the "four valver" which was usually a smallish, budget priced mantle radio. This particular variety of valve radio is the subject of this month's column. The 4-valve receiver was popular for a number of reasons. First and foremost, it had one less valve and associated components and was therefore cheaper to buy. Second, if used in a capital city location (ie, close to a number of strong local stations), its performance was more than adequate. As far as the average big city listener was concerned, there was little or no difference in performance between a 4-valve receiver and a 5-valve receiver. The difference between a 4-valve set and a 5-valve set generally lies in the audio stages. In a 5-valve superhet there are two stages of audio amplification after the detector. Most superhets use diode detection and the diodes are usually incorporated in one of the valves. With the 4-valve setup, the audio signal comes straight from the detector to the output valve without the added boost of the five valver's first audio stage. This has a significant effect on the volume of distant stations and it is quite often the receiver has a couple of weak valves and is a bit out of alignment, then it's a pretty sick little radio. Therefore, if a 4-valver is to work well it must be kept up to the mark. This means that it must have good valves, correct alignment and a reason::i ble aerial and earth. This point was made obvious to me quite recently. I repaired a "Precedent" 4-valve tablegram for a friend and was quite amazed at how well the radio performed when the job was finished. It was outstanding to say the least and comparable to many 5-valvers. Tasma tweaks Four-valve receivers must be kept in tip top condition if they are to perform well. The performance of this 4-valve Tasma was considerably improved by replacing the output valve with the correct type and by giving it a full alignment using an RF generator and output meter. Stromberg Carlson made a number of popular 4-valve receivers. This photograph shows an early post war model. Unlike their 5-valve brethren, 4-valve receivers have little in reserve. case that the 4-valver is only satisfactory on local stations or distant stations of considerable power (eg, 50kW). However, some 4-valve radios are better than others. Occasionally, a good 4-valver will perform as well as a not so good 5-valver but only if it is in tip-top condition. It must be remembered that a 5-valve radio has some reserve. If its valves become weak and it gets a bit out of alignment, there are no real problems because the set will continue to work reasonably well even though its performance level has dropped a little. On the other hand, if a 4-valve Such an experience made me think about some of my own 4-valve receivers and I selected one (a Tasma) and gave it the once over in order to improve its performance. The Tasma had been restored back in the days when I didn't have a valve tester or a radio frequency generator; nor did I know then what I know now. There was every chance that a good tune up would improve this little receiver. The set was in fairly good condition but it didn't have the performance that the Precedent had. The first step after removing the chassis from the cabinet was to test the valves. The 6V6 tested at 35% - not a very strong output valve for a small four valve set. The other three valves all tested at around 75-80% and were considered good enough to go back into service. The "7,000" figure marked on the speaker transformer indicated that the output valve should not have been a 6V6 but an EL33 or similar valve requiring a 7,000 ohm anode load. The correct anode load for a 6V6 is 5,000 ohms. A suitable replacement valve was found. It tested at 85% and was fitted to the socket. The next job was to check out the intermediate frequency transformers and a radio frequency generator was connected to the top cap of the 6A8 convertor valve. This particular exercise proved to be very interesting. When aligning a radio, one often has to take a guess at the intermediate frequency and in some cases a sweep of the generator dial NOVEMBER 1989 9 This neat little 4-valve Radiola is an attractive mantle model. It is housed in a Bakelite cabinet and has been restored to "as-new" condition. is required to pick up the frequency of the IF transformers. Sometimes it is a common IF, sometimes it is not. The Tasma's intermediate frequency appeared to be 460kHz. IF transformers are frequently misaligned in old receivers simply because someone back in the dim past has had a fiddle with them. Tightening up all the "loose screws" doesn't do much for IF transformer alignment. It would also appear as though a good many tune ups were made in the past without an RF generator. When it comes to IF alignment on 4-valve recivers, the job must be done with the utmost care so that the set will work at its maximum potential. In some cases, maximum output can be a little above or below the set's recommended IF. By using an RF generator and an output meter, such slight differences can be observed and the IF transformers can be tuned for maximum deflection on the output meter. I'm not suggesting that the set should be tuned to some intermediate frequency it was never designed to work on. What I am suggesting is that due to tolerances in the manufacture of the IF transformers and the RF generator, the best performance may not be at 10 SILICON CHIP the specified frequency as indicated by the generator dial. This special alignment procedure may require several trial IF transformer adjustments to establish the optimum frequency. In some cases it may make no difference and even if it does, the gain will be only slight. Remember, however, that some 4-valve receivers haven't got much going for them and if one can gain a bit anywhere along the line then it's worth having. The little Tasma turned out very well and the improvements wrought by using the correct output valve and a full alignment with an RF generator were well worth the effort. Reworked Radiolette Sitting on the shelf next to the Tasma is a very small 4-valve Radiolette. Although it too was supposedly "restored", it was like the Tasma and had been repaired back in the days when I lacked both the knowledge and the equipment I now have. So the little Radiolette was the next 4-valver to be reworked. There were two things wrong with this set. First, there was an annoying buzz in the speaker when the volume was turned up. Second, its overall performance was well down, particularly when compared to the Tasma with its new lease of life. The valves tested OK with the exception of the rectifier which was decidedly weak. This was replaced and there was a considerable increase in high tension voltage, with a corresponding increase in volume. The Radiolette has an HT filtering arrangement that consists of a lOkO resistor [actually two 20k0 lW resistors in parallel) with a 24µ,F electrolytic capacitor to earth at either end. A resistance check indicated that the two resistors had· gone high for they measured 19.5k0 [togetherf Closer inspection revealed that one of the resistors had burnt out. Replacing the burnt out resistor lowered the resistance to 10k0 [which is what it should have been) and again the HT voltage increased. Accordingly, the volume of the set continued to increase and the performance level was noticably improved because of these two simple repairs. This particular problem of the burnt out resistor emphasises a point I mentioned some months ago when discussing various aspects of resistors and the role they play in valve radio circuits. It was suggested in that story that all resistors should be individually checked when restoring an old valve radio. Resistors that are open circuit or have changed value beyond their tolerance should be replaced. In the light of what happened with the Radiolette under discussion, checking resistors is a worthwhile precaution against trouble. The next step was an alignment check and the IF transformers were tweaked for maximum readings on the output meter. This was followed by careful alignment of the oscillator and aerial circuits, during which dial alignment discrepancies were corrected. Melbourne radio stations can be made to line up reasonably well on old dials, even though station frequencies have changed a little since the dials were made. Capital city stations in other states may or may not line up quite so conveniently. Problems? ... and you don't have our .120page catalogue . .. Another set to be reworked by the author was this Radi~lette: It was ~eu ·· down in performance and suffered an annoying buzz from the speaker until it was properly checked out and re-aligned. The buzz in the Radiolette's speaker was the result of poor mounting. The speaker frame is rivetted to a small cardboard baffle which had warped considerably, allowing the speaker cone to detach itself from the frame at points between the rivets. Using a few drops of glue and clothes pegs for clamps, the speaker cone was stuck back onto the speaker frame and the warped cardboard baffle was straightened up at the same time. This relatively simple repair resulted in the speaker working properly without irritating buzzing sounds at odd frequencies. My efforts were well rewarded and the little Radiolette turned out a good deal better than it started out. Before the rework job it was struggling to bring in anything other than local stations. Now it distorts on local stations and really needs a local station switch or a shorter aerial to reduce overloading. Leaky capacitors Only last night I was working on another 4-valve radio (a love job for a workmate) which was sadly lacking in performance. A check on the high tension voltage showed it was down to 150 volts despite the rec- tifier being in quite good condition. Replacing five paper capacitors resulted in the high tension rising to 245 volts, with a noticeable increase in volume. There was so much leakage through those old paper capacitors that they caused the field coil in the loudspeaker to overheat. It doesn't take much to rob a little 4-valve receiver of its performance or to create other problems. If used for prolonged periods, the field coil would have eventually burnt out. Summarising, 4-four valve radios require good valves, faultless capacitors, resistors of the correct value and tip top alignment if they are to function well. Unlike their 5-valve brethren, they have little or no reserve power and require more regular attention if they are to be maintained at their peak. ~ Footnote A variety of speaker grille material suitable for vintage radios is available from Mr John Post, Lot 232 Patanga Court, Karana Downs 4306. Phone (07) 21 0 0067 . He can supply samples if you promise to return them. At last . .. a TRADE catalogue for the consumer ARISTA ... your one-stop problem solver. Video plugs and sockets .. . Video extension speakers . . . Video flyleads . . . Video RF interference filters . . . Video splitters . .. Indoor antennas . .. Video switching units . . . Down convertors . . . Video speaker controllers . . . Video camera lights . . . Video tape rewinders ... Video cine adaptors . .. Video head cleaners .. . Video splicing kits ... Video storage cases .. . Video dust covers . . . Video leads . . . Scart plug leads ... Video dubbing kits . .. Video headphones ... Video shotgun and wireless microphone systems .. . Pre-amplifiers with video inputs .. . Video camera stands . . . Just about anything you want. ... Try us ... NOW! Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ARISTI\. ELECTRONICS PTY LTD PO BOX 191 , LIDCOMBE, NSW 2141 NOVEMBER 1989 11 SERVICE IS MOTHERBOARDS IBM PC/XT COMPATIBLE TURBO 10MHZ MOTHERBOARD -Expandable to 1MB RAM -4.77 or lOMHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Eight expansion bus slots -AMI BOIS ROMs included -8087-1 Math co-processor capability -Performs at an average speed of 100% faster than the original IBM PC/XT -Norton SI ratiFYJ of 2.0 -Size (12' x 8.5") -Weight (1.75Ibs) SAVE $30 .$M9 $110 IBM AT COMPATIBLE 12MHZ80286 MOTHERBOARD -Expardable to 1MB RAM using 256K DRAM chips -Expardable to 4MB RAM using 1MB DRAM chips -Expardable to 2.5MB RAM using a combination of 256K and 1MB DRAM chips -8 or 12MHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Six 16-bit and two 8-bit expansion bus slots -AMI BIOS ROMs included -Zero wait state -Selectable RAM chips speed (80 or 100 nanosecond) -80287-8 Math co-processor capability -Norton SI rati!YJ of 13.7 -Size (13' c 8.75") -Weight (2.25Ibs) $499 SAVE $50 $449 IBM AT Compatible 16MHz 80286 NEAT Motherboard • Expandable to 1MB RAM using 256k DRAM chips or 4MB using 1MB using 1MB DRAM chips • Uses 1OOns DRAMs - Five 16-bit and three 8-bit expansion bus slots - AMI BIOS ROMs included - Supports all NEAT functions including shadow RAM, EMS 4.0, RAM remapping, selectable wait states etc. 80287-10 Math Co-processor capability - Norton SI rati!YJ of 18.0 8/16MHz hardware or keyboard selectable • Front panel LED indicators supported - Size 13' x 8.5' Weight 2.25Ibs ,..$199 SAVE $150 $649 HIREZ BUS MOUSE FOR IBM PC/XT/AT/2 (MODEL 25,30) AND COMPATIBLE COMPUTERS The new LOGITECH High Resolution Mouse is the only mouse designed expressly for today's new generation of high resolution displays, such as EGA, super EGA and VGA. The mouse is ideal for desktop publishing as well as CAD applications. With 320 dots per inch (dpi) resolution (compared with 100 or 200 dpi mice), the LOGITECH HiREZ covers the same area on your screen. but uses 62% less desk space to do it. This saves you valuable desk space, and effort .. Mouse maneuvers that used to require a sweep of the hand are now reduced to a flick of the wrist. Includes Plus Package software with mouse drivers, text editor, menu building and point-click software (Lotus 1-2-3). -Size (3.8'1 x 2.7"w x 1.06"h -Colour light grey $149 SAVE$30 LEADS & ADAPTORS Power Cable Y for disk Adaptor D9F-D25M Adaptor 3.5' power cable adaptor Serial Printer/Modem CBl 8ft Parallel Printer Cable - straight 12ft Parallel Printer Cable - straight 6ft Parallel Printer Cable - rioht anole Modem/Printer Cable Serial Cable for AT Floppy Cable 5.25' C34 Internal Floppy Cable 3.5/5.25" Internal Floppy Cable D37 External HOD Cable 34 way HOD Cable 20 way Serial Shielded Cable M-F Serial Shielded Cable F-F Centronics Shielded F-F Centronics Shielded M-M $5.95 $9.95 $5.95 $19.95 $12.50 $15.00 $19.95 $19.95 $19.95 $12.50 $12.50 $19.95 $12.50 $9.95 $19.95 $19.95 $19.95 $19.95 PROTOTYPE DEVELOPMENT CARD- NEW Basic circuit already built-in. Has 3290 holes - this will save prototypers lots of time and energy. SAVE $50 $149 SLOT EXTENSION Kil - NEW Compatible with AT and XT. Excellent for test and repair of PC add-on cards $199 EXTERNAL DISK DRIVES 0-EXISTANT FLOPPY NTROLLER ou need additional ppies and already have on board or combined ppy/hard controller this rd will enable you to run any mix of two external · drives (36Ok/720k/1.2M B/ 1.44MB) ONLY $119 4 PORT MULTI FORMAT All drive mechanisms are FLOPPY CONTROLLER Japanese in a metal case and include all interface, hardware, Controls up to 4 internal or 2 internal/2 external cables and when necessary floppies in any mix of36Ok/ external power supply. 720k/1 .2M B/1 .44M B. FOR PC/XT/AT ONLY $129 3.5• 720k $299 1.44MB $329 REMOVABLE HARD DISK 5.25" 360k $299 MOUNTING FRAME 1.2MB $329 This fantastic new product mounts any 3.5" half height FOR TOSHIBA LAPTOPS hard drive in a portable 5.25" 360k $349 mechanism. This allOIIVS 1.2MB $399 the drive to be safely FOR ATARI ST520 & 1040 removed from the PC for 3.5• 720k $299 security reasons or for installation in another PC. The heavy duty aluminium EXTERNAL FLOPPY DRIVE alloy mechanism includes CASE security lock, warning alarm and LEDs to indicate Suitable for mounting additional drives externally to your system status. Mounting frames can be PC/XT/AT. Comes complete with both internal and external purchased for use in additional PC's. cabling. If you already have a Uses 1 x 5.25" mounting floppy controller and need 111u1 e:i d, ive:::, u:11:: vvith 111::vv i;u· existant floppy controller. CASE 3.5• $85 CASE 5.25" $85 2MB MEMORY EXPANSION CARD FOR IBM AT AND COMPATIBLE COMPUTERS -Utilizers (72) 41256-120ns chips for the full memory capacity of 2Mbytes -Offers conventional expanded ard extended memory capabilities -Features auto-parity check -EMS compatible dfiver -RAM disk and print spooler software included -Manual ircluded NO RAM MEMORY CARD PC/XT for 640K $245 $99 cn~ra V,.,UVW• FRAME & CRADLE FRAME ONLY $149 $99 GAMES CARD 2 x games (joystick) ports $29.50 FOR DETAILS ON OTHER PRODUCTS PLEASE RING. IBM PC/XT/AT COMPATIBLE KEYBOARD -1 Ol Key -Enhanced keyboard layout -Tactile touch keyswitches -12 Function keys -llurninated LED indicators for Num Lock, Caps Lock ard Scroll Lock -Separate cursor pad -Low profile design -Automatically switches between PC/XT or AT -Manual included -Colour beige -Size (19"w x 8'd x 1.33'hl -Weight (4.6Ibs) $99 84 KEY $89 1/0 CARDS CASES SPECIALS - WHILE STOCKS LAST All cards have optional 2nd serial ports - add $25.00 FOR PC!)CT Serial/parallel/games/ clock $125 Serial 2 port (opt) $55 ~ro'!~W:~~~j~8ka:st mono graphics $229 Serial/parallel/game/ clock/floppy 360/720/1.2/ 1.44 X 2 · $149 FOR AT XT 10MHz Turbo motherboard AT 12MHz motherboard NEAT 12MHz motherboa.rd NEAT 16MHz motherboard 386-20 20MHz 2Mb onboard 386-25 25MHz 2Mb onboard CGA Card EGA Card 20130Mb HARD DISK DRIVE 42Mb HARD DISK DRIVE Both American manufacture 8088 $110 SAVE 25% $449 SAVE $50 $549 SAVE $50 $649 SAVE $150 $2499 $3999 $99 SAVE25% $225 SAVE $7 4 $349 $499 $125 $99 $129 $129 MINI TOWER $299 MIDI TOWER $349 MAXI TOWER $499 all with power suooly IBM AT COMPATIBLE 200W PUWER SUPPLY -Input <at>47 -400Hz (110/240V switchable) -Output+!;.,<at> 20A. -':N<at> OSA, +12v<at> BA, -12v<at>0.5A -Plug compatible connectors -Built in fanSize (6.5'1 x 5.88'w x 6'h) $199 P/S 150W P/S 150W BABY Serial/parallel/games Serial 2 port $65 Serial/parallel/games/ floppy 360k/720k/1.2/1.44 $149 BABY 8088 BABY 80286 $125 $145 DISK DRIVES 720k 3.5" 1.44Mb 3.S- $199 $225 BOTH INCLUDE 5.25• MOUNTING 360k 5.25" 1.2Mb 5.25• $179 $225 CONTROLLER CARDS 360KBfl20KB/1.2MB/1.44MB FLOPPY DISK DRIVE CONTROLLER CARD FOR IBM PC/'JJ/AT AND COMPATIBLE COMPUTERS -Allows connection of one or two 360KB. 720KB. 1.2MB or 1.33MB floppy disk drives. Includes cable for two internal disk drives and manual. $99 FLOPPY DISK CONTROLLER CARD FOR IBM PC/'JJ AND COMPATIBLE 'S -Run up to four 360KB disk drives -Includes cable for two internal drives -DC37S connector allows for an additional two external drives (external cable not included) -complete with manual OVER 15 YEARS MAIL ORDER EXPERIENCE MONITORS 12' TTL Green $179 12' TTL Amber $179 CGA 14' TTL Colour Philips 2 year guarantee. Stereo sound suits PC and Amiga $525 EGA 14' TTL Colour $649 $55 MFM H/D DISK CONTROLLER CARDS FOR IBM PC/'IJ/AT & COMPATIBLE'S -8 bit MFM hard disk controller card for the 1MB PC/XT and compatible computers. Can be used with many types of hard disk $139 drives. Cables and documentation included. H/D DISK/FLOPPY CONTROLLER FOR IBM PC/'JJ AND COMPATIBLE'S - 8 bit floppy and MFM hard disk controller for the IBM PC/XT and compatible computers. It will allow connection of up to two hard disks and two floppy 360. 720KB. 1.2 & 1.44MB drives. Cables are included to allow connection of one hard disk and two floppy disk drives. To connect a second hard disk drive an additional cable will be required. $175 HARD DISK/FLOPPY CONTROLLER FOR IBM AT AND COMPATIBLE'S -16 bit floppy and MFM hard disk controller for the IBM AT and compatible computers. It will allow connection of up to two hard disk drives and any combination of two floppy disk drives. To comect a second hard disk drive an additional cable •will be required. $245 MFM HARD DISK CONTROLLER CARD FOR IBM AT AND COMPATIBLE'S - 16 bit MFM hard disk controller for the IBM AT and compatible computers. It can be used with many hard disk drives. Cables are included. $220 P/4/f ~U'(JI( ~ PERSONAL COMPUTER MARKETPLACE PtyUd PHONE (02) 418 6711 FAX (02) 418 6713 Mail Order Address: P.O. Box 1100 Lane Cove NSW 2066 FREIGHT CHARGES lncfude $10 with order for all normal items - heavy items, e.g. monitors add $15. 14 day money back guarantee Order by phone (use credit card), by fax or by mall. Unlasa insurance Is declined it will b• charged 1t 1% of total purchase. This Is for your proteclion. ALL PCM CARDS COME WITH A 12 MONTH WARRANTY All other products with manufacturers warranty DONT BUY ELSEWHERE CHECK WITH US FIRST NOTE: No RAM on any board unless specified. All prices inc tax and are subject to stock availability and to change without notice ---- -- SO SMALL IT FITS IN A MATCHBOX By GREG SWAIN This sneaky FM bug is small enough to hide in a matchbox. It's super-sensitive and can be picked up on an ordinary FM receiver up to 100 metres away. We're not suggesting for one minute that you use this little FM wireless transmitter to listen in on private conversations or to engage in industrial espionage. That would not be nice. Instead, this unit is mainly intended as a fun project for the budding electronics engineer. Provided that you can handle a soldering iron and follow a simple wiring diagram, this project can be assembled in about half an hour. All the parts, including an electret microphone and the batteries, are mounted on a small PC board which then slips inside a matchbox. The only indication that something devious is going on is an external wire lead for the antenna. A miniature slider switch on the board lets you turn the unit off when it is not in use to save batteries. When the unit is turned on, signals picked up by the micro14 SILICON CHIP phone are used to frequency modulate a transmitter stage and this then broadcasts the signal to an FM receiver. In practice, the transmitter is tuned for an output frequency of 100MHz which is right in the middle of the commercial FM band (88-108MHz). You do this simply by adjusting a slug in the coil that forms part of the transmitter tuned circuit. In addition to its obvious application as an FM bug, this unit also has more serious applications. For example, it could also be used as a baby monitor or to monitor a telephone when you would otherwise be out of earshot. By the way, this circuit is super sensitive - so much so that it has no difficulty picking up sounds in a room even when the microphone is fully enclosed in the matchbox. In This larger than life size photo shows just how simple the FM bug really is. Power is supplied by two 1.5V cells. fact, if you get too close to the microphone, the circuit will be overloaded. The circuit also boasts excellent frequency stability and has a power output of about 3mW from a 3V supply and 20mW from a 9V supply (roughly twice that of previous designs). How it works Fig.1 shows the circuit of the FM Wireless Microphone. It uses three NPN transistors, all of which are low-cost BC548 types. The transistors are not critical however, and BC547 and BC549 types will work just as well. A 3V battery supplies power to the circuit via on/off switch St. When the switch is closed, power is supplied to the electret microphone via resistor Rt. Any sound signals in the room are now picked up by the microphone and AC-coupled to the base of transistor Qt via a .01µF capacitor (Cl). Qt functions as a common emitter amplifier with bias set by the ON r.t C7 10pF R6 47k' C6 33pF T 3-9V: ...I... ELECTRET MICROPHONE L1 : ZA-2599 L2 : PCB PATTERN B EOc VIEWED FROM BELOW MATCHBOX FM TRANSMITTER Fig.1: signals picked up by the microphone are amplified by Qt and used to frequency modulate VHF oscillator stage Q2. Q2's output is then fed to Q3 which drives the antenna. lMO feedback resistor (R2) connected between its collector and base terminals. The amplified output appears at the collector and is coupled to the base of Q2 via C2 (O. lµF). Q2 functions as a VHF (very high frequency) oscillator stage. 11 and C4 (33pF) function as a tuned collector load for Q2 while C5 provides positive feedback to ensure that the stage oscillates. A low inductance is used for 11 and a high capacitance for C4 to improve stability and reduce the effect of stray capacitance. This VHF oscillator stage is fre- quency modulated by the audio signal on Q2's base. Thus, when ever a signal is picked up by the microphone, this stage produces a corresponding FM signal. An adjustable ferrite slug in 11 allows the oscillator to be tuned across the FM broadcast band as indicated earlier. The RF (radio frequency) output of the oscillator is taken from the emitter of Q2 and coupled to the base of Q3. This stage also functions as a common emitter amplifier. It drives the antenna via an output resonant circuit consisting of coil 12 and capacitor C7 (lOpF). 12 actually forms part of the copper pattern on the PC board, while C7 tunes the resonant circuit to 100MHz. If you intend operating the circuit at 90MHz, then C7 should be increased to 12-15pF for maximum efficiency. Note that in this circuit, the antenna is isolated from the oscillator tuned circuit. This ensures greater stability since the oscillator frequency is no longer affected by movements of the antenna. Power for the circuit is derived from two 1.5V N-size cells. These give a supply voltage of 3V but you CAPACITORS D D D D D D No. 2 1 1 2 1 1 Value 0 .1µF .01µF .001µF 33pF 10pF 5.6pF IEC 100n 10n 1n 33p 10p 5p6 EIA 104K 103K 102K 33K 10K 5 .6 Fig.2: keep all leads as short as possible when installing the parts on the PC board. See text r~ orientation of Lt. RESISTORS D D D D No. 1 2 2 1 Value 1MO 47k0 4.7k0 4700 4-Band Code (5%) brown black green gold yellow violet orange gold yellow violet red gold yellow violet brown gold 5-Band Code (1%) brown black black yellow violet black yellow violet black yellow violet black yellow brown red brown brown gold black brown NOVEMBER 1989 15 PARTS LIST 1 PC board, code ZA-1 431 , 50 x 31mm 1 DPDT miniature slider switch 1 pre-wound coil with ferrite slug, DSE Cat. ZA2599 1 electret microphone insert 2 1 .5V N-size batteries 1 7 50mm-length of insulated hook-up wire (for antenna) 3 BC54 7, BC548 or BC549 NPN transistors (01-03) Capacitors 2 0. 1 µ.F monolithics or ceramics (C2,C8) 1 .01 µ.F ceramic (C1) 1 .001 µ.F ceramic (C3) 2 33pF ceramics (C4,C6) 1 1OpF ceramic (C7) 1 5.6pF ceramic (C5) Resistors (0.25W, 5%) 1 1 MO (R2) 2 47k0 (R4,R6) 2 4 . 7k0 (R1 ,R3) 1 4700 (R5) can use a 6V or 9V supply if you want longer range and space is not a consideration. The current consumption is about 11.5mA. Construction Construction is straightforward. A complete kit for this project is available from Dick Smith Electronics for $16.95 (see panel), so obtaining the necessary parts is ncit difficult. All you have to supply is the matchbox. The batteries are secured by soldering their terminals to loops of tinned copper wire which in turn are soldered to the copper pads on the PCB (see Fig.2). Tin the ends of the batteries first by scraping away some of the plating and then applying a hot soldering iron. Fig.2 shows how to install the parts on the PC board. Install the two wire links first, then the resistors and the capacitors. These parts should all be pushed flat against the PCB before soldering their leads. The three transistors can now be installed. Push them down onto the board as far as they will comfortably go and be sure to match the transistor cases to the outlines on the wiring diagram. Solder their leads, then install the slider switch. The switch mounting lug adjacent to the edge of the board should be snapped off using a pair of pliers (see photo) otherwise it will foul the side of the case. Above: the square section at the top of coil L1 should be trimmed off, preferably before mounting it on the PCB. Orient the coil as shown. Left: the circuit fits neatly into a matchbox. 16 SILICON CHIP Similarly, the square section at the top of coil 11 must be cut off to provide clearance for the matchbox lid. Use a sharp razor blade for this job but be sure to remove the ferrite slug first. Install 11 so that the highest shoulder on the plastic former is adjacent to the switch. The electret microphone is mounted on the board using two short lengths of tinned copper wire (see photo). To do this, first solder the leads to the pads on the back of the microphone, then bend them so that they match the holes in the PCB. The microphone can then be installed on the board with its positive terminal adjacent to R5 (4700). You can set the transmitter output to virtually any spot on the FM band but we recommend a frequency of about 100MHz. Don't forget to turn the unit off when it is not in use (the switch is shown here in the 'on' position). It's quite easy to identify the microphone terminals. The negative terminal is the one connected to the metal case. Now for the batteries. These are mounted on one end of the PCB and are secured by soldering their terminals to loops of tinned copper wire. These wire loops in turn are soldered to the copper pads on the PCB. Be sure to install the batteries the right way around and note that they face in opposite directions to each other. Finally, connect a 750mm-long antenna (use insulated hookup wire) to 12 on the copper side of the board. Of course, you can use a shorter antenna if you wish but note that this will give a reduced range. Testing A commercial FM receiver is required for the test and adjustment procedure. Set the volume control to the usual level, then turn the receiver on and tune it to 100MHz. Now turn the FM transmitter on (just slide the toggle switch towards the centre of the board) and adjust 11 using the insulated alignment tool. When the transmitter is tuned to the correct frequency, you will hear a corresponding whistle in the receiver. If you now speak, you should be able to hear your voice via the receiver but note that it will probably sound quite distorted due to overloading and feedback effects. To fully test the unit, slip it into the matchbox with the antenna lead emerging through a hole in one end of the drawer. It can then be taken into a room where other people are speaking (or the TV is going). Any conversations should now come through loud and clear on the receiver. That's it! Don't forget to move the slide switch to the off position when the unit is not in use otherwise you'll quickly flatten the batteries. De-bugging Now, what if you suspect that your room has been bugged by one of these FM wireless microphones? How do you detect it? It's quite easy. All you do is turn on your FM radio and wind the volume control well up. You then tune slowly right across the FM band. If at any time you come across a whistle, you have been bugged. The whistle will be caused by acoustic feedback between the microphone in the bug and your radio's loudspeaker. It's then a matter of ferreting the little blighter out. You do this by moving your FM radio around the room. As you get closer to the bug the whistle (or howl) will become louder. [§;I Where to buy the kit A complete kit of parts for this project is available from Dick Smith Electronics stores or by mail order from PO Box 321 , North Ryde, NSW 2113 . Phone (02) 888 2105. The kit comes with all parts (including two 1.5V batteries) and sells for $16.95 plus $2 .00 p&p (standard mail only) . Quote Cat. K-5006 when ordering . Note: copyright of the PC artwork for this project is owned by Dick Smith Electronics . NOVEMBER 1989 17 Plots weather decodes Fig.1: a typical weather map as transmitted by the Bureau of Meteorology in Canberra on 5100kHz. It was decoded using the following switch settings on the Radfax Decoder: S1 1.7-2.0; S2 ± 600Hz; and S3 600 baud. Note that this particular map is leaning slightly to the left. This is corrected by altering a value in the software. 18 SILICON CHIP maps on your computer1 radioteletype and Morse code. a ax Got a computer and a shortwave receiver? Why not link the two together with this Radfax Decoder and plug into the world of FSK transmissions? You can get up to the minute weather charts, read overseas radioteletype messages as they are transmitted and eavesdrop on Morse transmissions, without even knowing Morse code. Circuit design by JOHN CLARKE If you have an IBM PC or PCcompatible computer and a shortwave radio you can plug into the intriguing world of non-voice transmissions on the shortwave bands. These include radioteletype (RTTY), Morse code and perhaps the most interesting of the lot, facsimile (fax). Of the fax transmissions, weather maps are the most interesting and useful, particularly if you are in a remote rural area or at sea. Weather faxes can take quite a lot of different forms . We have plotted out maps giving the conventional isobars with lows and highs, just as shown on TV every night. As well, we have received cloud maps (nephanalysis), also as seen on TV weather reports. We also have charts of wind wave and swell height which are not shown on TV and these could be very useful if you were at sea in a sm"l.ll boat! Regardless of whether maps are shown on TV or not, the attraction of being able to decode your own is that you get them as soon as they are transmitted. And of course, you can decode RTTY and Morse as well. FSK transmissions Both fax and RTTY transmissions use the FSK principle. FSK stands for "frequency shift keyed" and refers to a system whereby the modulation on a radio transmission is ·continually switched or "keyed" between two frequencies such as 2400Hz and 1200Hz. The rate of switching sets the "Baud" rate which is an old telegraphic term which means bits/second. Typical nominal rates for RTTY are around 75 baud (bits/sec) while typical transmission rates for fax transmissions are 1200, 600 or 300 baud. As for Morse - well Morse is pretty slow. Decoding FSK tranmissions does not take a lot of circuitry but it does require some software to allow the computer to turn the decoded digital data into something intelligible which can be displayed on the screen or printed out on a dot matrix printer. We have designed the circuit of the Radfax Decoder while the soft- ware, called " Radfax 2" , was written by Michael Delahunty. The software is only available directly from Michael Delahunty, as detailed in a panel in this article. The hardware OK, let's be specific about the hardware you need if you want to get into the world of fax and RTTY. First, as already stated, you need an IBM PC XT or compatible computer with a CGA or EGA monitor. The software requires the CGA or EGA monitor so if your machine presently only has a monochrome monitor and MDA card, you will need to do something about it. There is a version of the software available to suit a Hercules Graphics card or, alternatively, you could install a new Combo card from Electronic Solutions which lets a monochrome monitor work with software which needs a CGA card. You simply install it in place of the existing MDA card and change the DIP switch settings on the computer motherboard to suit. The program requires at least 2 56K of RAM in the computer and it will not work if you attempt to use it in conjunction with memory resident programs such as Sidekick. This is easily fixed by booting up the computer just with Radfax 2. If you want to print out weather maps and other info received via fax or RTTY transmissions, you will need an IBM or Epson compatible printer. The Radfax 2 software is rather clever in that it allows you to print out faxes sideways on your printer. This not only gives larger NOVEMBER 1989 19 This photo shows how a fax transmission appears on screen. Once the transmission has been completed, the picture can be saved to disc and printed out. This map is of wave swell height and is from the Bureau of Meteorology in Canberra. \i . ,, I printouts but gives much more detail than is available from the smaller printouts or from the screen. The shortwave receiver ___..... ·j } Fig.2: a printout has much better resolution than the corresponding on-screen picture. This printout was made in the conventional fashion but the software also allows you to print out faxes sideways for even better detail. The map shows wind wave height for 23rd September, 1989 (Bureau of Meteorology, Canberra on 5100kHz). 20 SILICON CHIP The FSK tones for fax and RTTY can only properly be received on a radio that has a facility for picking up SSB (single sideband) transmissions. This means you need a shortwave radio which either has a BFO (beat frequency oscillator), which is normally used for picking up Morse, or an SSB switch for selecting USB (upper sideband) or LSB (lower sideband). You will also need a decent outdoor antenna for your shortwave radio although we have successfully picked up some transmissions using just a whip antenna. For best results though, you need an outdoor antenna - the bigger, the better. The Radfax Decoder Next, there is the Radfax Decoder which connects to the audio out- put of your shortwave receiver. The output of the decoder then connects to the RS-232 (serial) or to the parallel printer port on your computer. If your computer has an RS-232 port, we suggest that you use it for the Radfax Decoder input, leaving the parallel port for the printer. That way, you can print out faxes at will, without having to disconnect the Radfax Decoder. The decoder is housed in a standard plastic utility box which has three rotary switches and one fine tuning control. The only other front panel feature is a LED to tell you that the decoder is working. Now let's have a look at the circuit. There is not a lot to it, just two integrated circuits and a 3-terminal regulator. +5v---..------------~ LOCK LE01 .01 0--I AUDIO INPUT 220k ¼ .016 Bandwidth and baud rate S2 sets the operating bandwidth of ICl, for which it will generate high and low error signals. In general, use a wide bandwidth 2 .>o-1"" ---OMORSE (CW) .022 OUTPUT 2 3;:r S1 : 1 2 3 4 2525/2D57Hz 2066/1663Hz 1663/1371 Hz 1377/1122Hz 430k 220k CENTRE FREQUENCY S1 IC1 XR2211 S2 : 1 : ±6DOHz 2 : ±400Hz 3 : ±3DOHz 4 : ±2QOHz 5 : ±100Hz 6: ±50Hz S2 6ANOWIOTH 470k 11 .0056I Phase lock loop The heart of the unit is ICl which is an XR2211 FSK demodulator/ tone decoder. As its name suggests, it is designed especially for decoding FSK signals. It is basically a phase lock loop which generates a high or a low error signal depending on whether the tone at its input is high, say 2400Hz or low, say 1200Hz. The error signal, at pin 7, is buffered by inverter IC2a and then fed to the computer input which may be the RS-232 port or the parallel printer port. Switch Sl and the associated four capacitors provide for four separate free-running frequencies for the phase lock loop. The 5k0 potentiometer (VRl} allows these frequencies to be adjusted within the limits shown for Sl on the front panel. For example, for setting 2 on S1, VR 1 allows the centre frequency of ICl to be set anywhere between 1683Hz and 2066Hz. This is the setting that we used most of the time, by the way, but depending on the nature of the transmission, you will need the facility provided by Sl. For example, when receiving Morse or RTTY, you may want to use setting 4. .,. .,. 100k ..-------+5V 36k 4.7k 12 IC2a 16,1 1-'---+--.:!!5 4 FSK/FAX OUTPUT 22k .,. FREQUENCY FINE ADJUST VR1 5k LIN 560k S3 : 1 : 1200 2 600 3 300 4 . 150 5 75 6 45 01-04 4x1N4002 12VAC 100 16VW GNO .,. RADFAX DECODER Fig.3: the circuit is based on an XR2211 FSK demodulator/tone decoder IC (IC1). This IC is basically a phase lock loop and generates a high or low error signal, depending on the incoming tone frequency. when receivmg fax (ie, ± 600Hz) and a narrow bandwidth for Morse and RTTY. Using a low bandwidth reduces data errors due to noise but if the bandwidth selected is greater than the difference between the two FSK tones, the circuit will not work. S3 gives the optimum filtering to suit the various data rates. In general, a smaller filter capacitor is used for the higher data rates. For example, at the 1200 baud setting, the filter capacitor is .0022µF . Morse output Since Morse is transmitted by switching on and off the carrier frequency, ICl will respond to a Morse transmission by switching its lock indicafion output, pin 6, on and off. To provide a visual indication of this, inverter IC2d drives LED 1. IC2b and IC2c provide buffering of the lock indication output before it is fed to the computer port. LED 1 will light continually when the Radfax Decoder is correctly NOVEMBER 1989 21 Fig.4: the PCB parts layout. Be sure to adjust each switch for the correct number of positions before installing it on the board (see text). The 3-terminal regulator is mounted flat on the board and secured using a screw and nut. picking up a fax or RTTY signal and will flicker on and off in time with a Morse signal. Power The Radfax Decoder is powered from an external DC or AC plugpack which can be 9-12 volts (nominal). D1 to D4 are connected in a bridge so that a DC or AC source can be used (and also without regard to polarity in a DC source). The diodes feed a 220µF 16VW capacitor and then the 3-terminal 5V regulator. Further filtering of the 5V output is provided by a lOOµF capacitor. The total current drain is quite modest and should be around 20 milliamps. Construction We housed our prototype Radfax Decoder in a standard plastic box measuring 159 x 95 x 52mm. All the components, including the switches and pot, are mounted on a printed circuit board measuring 125 x 88mm (code SC 03111891). Since the rotary switches are soldered directly to the printed board, it does not attach to the case but hangs off the front panel via the switch bushes. Assembling the decoder board is a fairly straightforward matter although it's best to install the PC pins, links, resistors and other small components before mounting the three rotary switches. The board pattern is designed specifically to suit rotary switches with PC pins. Before installing the switches, they should be adjusted to give the required number of switch positions. For example, S1 is adjusted to four positions and S2 and S3 to six positions. This is done by removing the nut from the switch bush and lifting out the lock washer to reveal the stop ring. You then reposition the stop ring tab in the hole marked '4' for a 4-position switch and in '6' for a 6-position switch. Check that each switch will give the required number of positions before installing it on the board. The 3-terminal regulator is laid flat onto the board and its tab anchored with a screw and nut. The red LED is installed with leads about 10mm long so that it protrudes through the front panel (when it is fitted). The potentiometer is installed by soldering its three connections to the three PC pins on the board. Note that the 220µF power supply filter capacitor is a pigtail type. A PC-mounting type will be too high to fit between the lid and PC board. RESISTORS □ □ □ □ □ □ □ □ □ □ □ 22 No Value 1 1 1 560k0 470k0 430k0 220k0 100k0 75k0 56k0 36k0 22k0 4.7k0 2200 2 2 1 1 1 1 2 1 SILICON CHIP 4-Band Code green blue yellow gold yellow purple yellow gold not applicable red red yellow gold brown black yellow gold not applicable green blue orange gold not applicable red red orange gold yellow purple red gold red red brown gold 5-Band Code green blue black orange brown yellow purple black orange brown yellow orange black orange brown red red black orange brown brown black black orange brown purple green black red brown green blue black red brown orange blue black red brown red red black red brown yellow purple black brown brown red red black black brown When all components are on the board, check all your assembly and soldering carefully. Now connect power and check that the + 5V rail is present at the output of the 3-terminal regulator, at pin 1 of IC1 and at pins 1 & 16 of IC2. If that's OK, put the board aside and start work on the case and lid. The case itself requires two 4mm The 5k0 frequency adjust potentiometer (VR1) is mounted on the board by soldering its terminals to three PC stakes. Note that the 220µF capacitor must be a pigtail type (if you install a PC-mounting type, it will foul the lid of the case). Take care when installing the two ICs as they face in opposite directions to each other (see Fig.4). diameter holes for the power supply and output leads and another hole to suit the RCA panel socket. Use the front panel artwork as a template to mark the lid for drilling, then drill a 5mm hole to suit the LED and the holes for the switches. Hint: drill these Qoles to 10mm diameter then open them up slightly with a tapered. reamer, · if necessary. You can now attach the front POLYESTER AND CERAMIC CAPACITORS □ □ □ □ □ □ □ □ □ □ □ □ No Value IEC EIA 1 2 1 1 1 1 2 1 2 1 1 1 0.15µF 0 .1µF .068µF .039µF .033µF .027µF .022µF .018µF .01µF .0056µF .0047µF .0022µF 150n 100n 68n 39n 33n 27n 22n 18n 10n 5n6 4n7 2n2 154K 104K 683K 393K 333K 273K 223K 183K 103K 562K 472K 222K When installing the LED, leave its leads about 10mm long so that it will protrude through the front panel. NOVEMBER 1989 23 panel label to the lid. This done, attach the various input, output and supply leads to the printed board, then fit the lid over the switch and pot shafts and install the locking nuts. Attach knobs to the switches and pot, screw the lid to the case and you are almost in business. The final wiring task involves connecting the Radfax Decoder output wires to a DB-25 male or female plug to suit the RS-232 or parallel printer port on your computer. As noted above, if you have an RS-232 port we suggest you use that for the Radfax Decoder output. That way you don't have to bother with connecting and disconnecting the printer each time you want to print out a fax or RTTY page. If you are using the RS-232 port, the connections are as follows: ,a, c:o ,,- ,M 0 (.) en RS-232 Connections Radfax Decoder RS-232 Port RTTY /Fax output pin 5 pin 6 pin 7 Morse output GND If you are using the parallel port, the connections are follows: Parallel Port Connections Radfax Decoder RTTY /Fax output Figs.5 & 6: here are actual size artworks for the PC board and the front panel. Inspect the PCB pattern carefully after etching and correct any defects before mounting any of the parts. Morse output GND • Parallel Port pin 13 pin 12 pins 18-25 • • ±50 • • • • ±100 • 2-2.5 • e 1.7-2.0 1-1 .3 1.3-1.7 ±200 • • kHz CENTRE FREQUENCY • • ±400 ±300 • ±600 45• 75. •1200 •soo • • 150 300 Hz b/S BANDWIDTH BAUD RATE • LOCKe • • 24 SILICON CHIP e • • • FINE ADJUST fi'McooER • PARTS LIST 1 PCB,codeSC03111891, 125 x 88mm 1 front panel label, 1 53 x 90mm 1 plastic case, 159 x 95 x 52mm 4 knobs 3 single pole 12-position PCmounting rotary switches (Jaycar Cat. SR-1 21 0, Altronics S-3021 ) 1 5k0 linear potentiometer 1 RCA panel socket 1 DB-25 plug to suit IBM serial or parallel port 10 PC stakes Semiconductors The audio input to the Radfax Decoder is fed in via an RCA panel socket mounted on one side of the case. The LED lights continuously when you are picking up a fax or RTTY signal and flickers on and off in time with a Morse signal. Now connect your shortwave receiver to the Radfax Decoder and the Decoder output cable to the computer. Boot up your Radfax 2 software disc; ie, type in "Radfax 2" and hit return. The main menu should come on and then you can enter a sample fax chart from the files directory. Having displayed a fax on the screen, you will know that the software is working OK. You now have to check that the software knows which port you are using for the Radfax Decoder input. To do this, you call up the Settings Menu by typing S (when the main menu is displayed). If you are using a serial port, the address is 02FE Hex (Com2) or 03FE Hex (Coml). If you are using a parallel port, the address is 279 Hex (LPT2) or 379 Hex [LPTl ). You call up the correct port address by using the juggle command until the right value is displayed (type J). What to look for It is now simply a matter of tuning in a good fax signal. On the east cost of Australia, the most reliable signal is 5100kHz which is the Bureau of Meteorology in Canberra. They also broadcast on 11,030kHz. If you are in the north of Australia, try the Bureau's Dar- win transmitters on 7535kHz, 10,555kHz and 13,920kHz. The New Zealand weather station on 13,550kHz is also worth a try. Other international fax stations worth trying are 13,510kHz, 14,826kHz, 14,685kHz, 16,320kHz, 17,068kHz and 18,130kHz. For RTTY stations, try 7542kHz and 10,730kHz [France), 9968kHz and 10,552kHz [Germany), 7695kHz and 13,563kHz (Taiwan), 13,780 kHz [Korea), 6845kHz, 9120kHz, 10,960kHz and 14,514kHz [Reuters), and 9985kHz, 16,232kHz and 19,520kHz [UPI). Many other fax and RTTY stations are listed in the book "Shortwave Radio Listening With the Experts", by Gerry L. Dexter. This was reviewed in our June 1989 issue and is available from Jaycar Electronics stores at $25.95. ~ 1 XR2211 FSK demodulator (IC1) 1 4049 or 4009 inverter (IC2) 1 7805 5V 3-terminal regulator 1 5mm LED (LED 1) . 4 1 N4002 1 A diodes (D1-D4) Capacitors 1 220µ.F 16VW pigtail electrolytic 1 100µ.F 16VW PC electrolytic 1 0 .15µ.F metallised polyester 2 0 . 1µF monolithic ceramic 1 .068µ.F metallised polyester 1 .039µ.F metallised polyester 1 .033µ.F metallised polyester 1 .027 µF metallised polyester 2 .022µ.F metallised polyester 1 .018µF metallised polyester 2 .01 µF metallised polyester 1 .0056µ.F metallised polyester 1 .004 7 µ.F metallised polyester 1 .0022µ.F metallised polyester Resistors (0.25W, 5%) 1 1 1 2 2 1 560k0 470k0 430k0 220k0 100k0 75k0 1 1 1 2 1 56k0 36k0 22k0 4. 7k0 2200 Where to buy the software The Radfax 2 software is only available directiy from the author, Michael Delahunty, who has kindly given us permission to use the name "Radfax Decoder" for this project. The software is priced at $35 plus $3 for postage and packing. It comes on a 5 ¼-inch 360K floppy disc and with a 1 3-page instruction manual. You need to specify whether you have a CGA, EGA or Hercules Graphics card. Write to Michael Delahunty, 42 Villiers Street, New Farm, Qld 4005 . Phone (07) 358 2785 . NOVEMBER 1989 25 I EXTRA VALUE SWITCHES! 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Ideal for alarm systems, intercoms etc. Cat M-9530 Only s29 95 Ideal For Trucks! 24/12V Convertor A sturdy regulated supply that's perfect for running CB's, stereo systems, etc in trucks with 24 volt systems (even some caravan parks supply 24V). Gives 13.8V <at> 2 amps DC. Suitable for in-dash or under-dash mounting . Comes with mounting hardware and instructions. Cat M-9810 ssgss Bargain Nicad Charger A great way to save money on batteries and make sure you've always got power when you need it! The DSE Charging Cabinet charges all the most common batteries, up to 8 at once, in any combination - AAA, AA, C, D & 9 volt. With indicator lights for each cell and reverse polarity protection. It's mains operated and comes with built-in test meter. Cat M-9505 Only s39ss DICit0sMITH Talking With... Play Music! Creative Music System The Creative Music Synthesizer card simply plugs into your IBM compatible and allows you create your own stereo sounds. With 12 channels (Voices), stereo output, 32 preset instruments and a stereo amplifier to drive speakers, headphones, etc. Define your own instruments, play 11111-!l!IIJJII background music, create albums of your favourite tunes and play them in any sequence or compose your own music ... it's fantastic! Cat X-2020 '299 r,o~ s! ~ ! ~ ~ ~r'! ' ~ ~o, conversation? "Speech Thing" is a complete hardware and software package which adds sound capability to your PC. Converts text (either from keyboard or ASCU files) to high quality speech. Simply plug Speech Thing into the parallel port and keyboard (comes with adaptors) - and it doesn't interfere with their operation. Can be used in conjunction with the 'Voice <at>-- - o Master' (X-2038) to sample and edit ~ digital sounds. Cat X-2036 =-.. ~: . s149 IBM AT Compatible 80286 Motherboard Tell It What to do! Building your own computer or upgrading the old one? Our new 12MHz motherboard is the way to go for the ultimate computing power. DRAM not included. How often have you wanted to tell your computer what to do? With Voice Master you can give it verbal commands. You want DOS? Just TELL the computer and it'll get it for you. Comes complete with headset and software which allows you to · ·· ·· ex~riment with voice recognition. With it you can set up to 256 different voice activated keyboard macros. Installation requires an 8-bit expansion slot. The perfect match for "Speech Thing"! Look .... • Expandable to 1Mb using 256K chips • Expandable to 4Mb using 1Mb DRAM chips• Keyboard or hardware selectable 8112MHz operation • Six 16-Bit and Two 8-Bit expansion slots. • Selectable for RAM speed - 80 or 100 nanosecond • Selectable from Owait states on read operations (with 80 nanosecond RAM) • Socketed for 80287 Coprocessor • Performance - 13. 7 using Norton S.I. • Battery backed real time clock on board • AMI Bios ROM's included • OK RAM supplied Cat X-2038 IBM/Apple Joystick Versatile, fantastic value and it can be used on either IBM or Apple II compatible computers. Lightweight and comfortable it's the best way to get into those fast action games. Bargain Super Mouse Casio fx-61 f Outstanding quality at a bargain price! Plugs into Calculator any serial port and comes with 9-25 pin adagtor. Complete with set-up disk, drivers, manual, r Halo paint program, mouse Pad and 'mouse house' so you can pack it away when not in use. Fully Microsoft compatible. Cat X-3805 f ~~s~o?.!es your Serial port. Cai X-3806 $129 Arcade Quality/ Commodore/Atari Joystick It's almost indestructible! Uses microswitches for the ultimate in speed and reliability. With twin fire buttons. It uses the same mechanism they use in arcade machines ... so you can be sure it's built to last...and last.and .... ! Cat X-3831 WITH 3 YEAR WARRANTY! s3995 .,,:;;;---a~ ~ Cat X-3570 Just With Electronics/ Electrical Formula/ With Dr Halal RS-232 Multilink Adaptor s4995 s199 s499 Cat X-1002 A complete in-line tester/ adaptor which makes complex and time consuming Serial connections a breeze! Comes fitted with 25 pin male connector and 25 pin female connector. With 1·umper pads and wires, 24 in- ine switches and 8 bicolour LED's wh ich monitor the lines and tell you at a glance when you've got it right. Cat X-2654 Voice Master It's one of the most useful tools anyone workinQ with electronics could have. With 27 of the most used electronics formulas built-in! Resonance frequency, impedance, voltage/current gam ... everything! Includes 74 scientific functions, 1Odigit display, pro~ramming functions .. .. it's unbelievable. Cat V-3828 $ Just 7995 Qualitv Disk Drives Easy to inst; lf in any IBM compatible! Great value half height floppy disk drives in all of the available configurations. Can be installed as an internal drive or externally (with optional case.) $249 1.44Mb Version. Needs DOS 3.3 or higher. S299 S199 3.5" Disk Drives 720K Version . Needs DOS 3.2 or higher. Cat X-2220 Cat X-2221 5.25" Floppy Disk Drives 360K Cat X-8012 El Ill El D la l:IEIIJIDD IIIEIEIDa a am II m Install Your Own Professional System The Complete Home Security Pack A complete, professional quality security system in a carry-away pack. You'd be surprised how easy it can be to install yourself. And it's outstanding value! There's everything you need for a comprehensive home security system .... and we mean everything! Look What You Get .... • High quality 4 Sector Control Panel - The heart of the system. • 2 Passive lnfrared Detectors - for large area surveillance. Eg. Hallway, entrance, room. • 2 Reed (Magnetic) Switches - For window and door protection. • Siren Horn and heavy Metal Cover with tamper protection. • Internal Screamer, Panic Button and Strobe Light • Back-up Battery, Power Supply and 100m of Cable • Plus Deterrent Stickers and Installation Manual. ALL Th.IS For Only ssgg Cat L-5150 Ideal for Home Unitsl Complete Wireless Security Our "wireless" home alarm is ideal anywhere wiring is difficult or impractical - the system offers complete security and can be installed in little more than an hour -and you don't need an extensive tool-kit to do it. What's more, when you move house, you can easily pack it up and take it with you. Comes With .... Central Control Unit - simply plugs into the mains and is left on a shelf or in a cupboard. Two Magnetic Sensors -easily fitted to doors or windows. Passive lnfrared Detector - for installation in entrance-way, hallway, room, etc. Remote Controller -allows you to operate the system from the palm of your hand; just like your VCR, etc. cat L-5125 Just s399 If you're lucky enough to live in a strong reception area, then this is afl you'll need for a good picture. These oldfaithful spiral antennas have been doing a great job for yonks. Cat L-4010 That's Value! s995 Perfect where an outdoor antenna is too much trouble. Just sits on the TV and can be adjusted in seconds. Takes arms for maximum adjustment. Cat L-4015 S129 Budget UHF/VHF Antenna Deluxe 3-Band Indoor An fantastic low price for a combined UHF/ VHF antenna that's ideal for metropolitan or good reception areas .... and you can easily install it yourself! Made from quality corrosion resistant materials for longer, trouble free life. Outdoor UHF Band Ideal For Fringe Areas! Top Performance 4 & 5 Medium The latest 23 element design multiband UHF UHF/VHF antenna for medium signal areas. It's an excellent anti-ghosting antenna and includes balun and coax connection. High quality corrosion resistant construction. Cat L-4086 o;;;s49 ~ 9~ Special 6udget Antennas available for many areas, check your local store. The inexpensive (and easy) way to get a clear picture in good reception areas. This quality indoor UHF/FMNHF antenna can be instalfed in minutes. It's ideal for colour, black & white and stereo. Cat L-4005 i»XPRESS ORDER BY PHONE - 008 22 6610 (LOCAL CALL FEE) OUTSIDE SYDNEY SYDNEY AND ENQUIRIES - (02) 888 2105 FAX: (02) 805 1986 OR WRITE TO DS XPRESS, PO BOX 321 N/RYDE NSW 2113 ALL MAJOR CREDIT CARDS ACCEPTED. 0/NITE COURIER AVAILABLE. 24 HOUR DESPATCH OF ALL ORDERS A top performing, high gain antenna with reflector. Saves the hassle of two antennas and it's made to the highest quality with all corrosion resistant materials. Cat L-4051 s149 rn [I)[§]ITJ rnmJ[§]ITJrnJ[[Q][g] mrrmrn[§] Unbslisvab/B FBBIUTBS and Va/us/ lncludss Battsry Chsckl 3.5 Digit With TR, Diode & Continuity 20MHz Dual Trace CRO A bright change for the toolbox! Includes all the usual ranges, current to 10A and resistance to 200megs... Plus a continuity checker with a fast 1OOms response time, a diode and transistor checker and battery checker (it tests under actual load conditions). Takes a single 9V battery (and tells you if it's low) and comes complete with a flip down handle that doubles as a stand. Ranges: DCV: 0.2, 2, 20, 200, 1000V ACV: 0.2, 2, 20, 200, 650V DC: 200uA, 2, 20, 200mA, 10A AC: 200uA, 2, 20, 200mA, 10A Resistance: 200, 2k, 20k, 200k, 2M, 20M, 200M Transistor Check: Hfe Diode Check: 1mA, 3.2V continuity: Buzzer Battery Checks: 1.5V(<at> 200mA), 9V(<at> 6mA) cat a-f445 AGood Onal s349s What's more, we'll be selling this model next year. Beware of cheap clearance models! Simple FM A A Much Improved Transmitter For \\t~ Light Chaser The 2Mtr Band ~ The first in a great new series of easy to build projects for the amateur radio enthusiast. It's designed to make setting up and construction easier so the novice can more readily follow . the operation and therefore gain more confidence in its use. The solid state NBFM transmitter module produces over 1 Watt at 144MHz. The operation Is simple where the signal from a microphone is amplified to form a modulation input of a variable-frequency crystal oscillator. The oscillator frequency, around 24MHz, is multiplied in two stages, first a tripler ... then a doubler to 144MHz. The resulting signal is amplified through several stages before being fed to an antenna. Short form kit contains components ~~ Cat K-6010 . a:~ ==~ DfCK lf ..a•.., _~Ml1W FM Wireless Microphone A \\t~ ~ This one is great! The FM Wireless Microphone is small enough to be inserted into a matchbox, can be tuned to operate at around 90MHz (On your FM receiver), incredibly stable, extremely sensitive circuitry and relatively easy to build. It's fantastic! You can use it as a bug (when you're playing around) or even as a link between, say, workshop and house, etc. Comes as a short form kit with components and PCB. Also includes batteries. Cat K-5006 t.,\~' ~ ~ ~~ , Communications On & BstwBBn Bikssl -~ r~~~~~h~~~~!ls! ~ ~as ~ ~~i! t d! ~ !f~~~r~ ~si! ! ~ A true FM intercom _which allows communication.between passenger_ and r!der a~ well as between.bikes. Not only _~ !.! ~ - ~ - - ~ - that, but It also doubles as an FM receiver for your favourite radio station. The transmitter and receiver are housed in a small case which fits in the jacket pocket. The speaker and microphone are fitted in the helmet. As well, the microphone is voice activated to save switching. Beware t)•L~~~ • ~..•, ~~~I though, it is not easy to build and is best tackled by someone with .a sound knowledge of kit construction. !aa _ !'."~ ~ !.! !!.__ ?:! ~ __ ~ - ~ comes complete - ready to assemble with all components, board, mic, speaker and case. Powered by three penlight batteries (not included). Cat K-6020 ~ _ It's miles ahead of previous models! Our new Light Chaser is low in cost, easy to build, incredibly flexible and it's designed with safety in mind. Providing 6 different chasing patterns, 8 speeds, an enhanced front-panel monitor display and the ability to run lamps to a total of 2400 watts. When the design was first conceived by our R& D Department safety was considered paramount, so it was decided the best way to achieve this was to build a 'dedicated' chaser. This also allows many more functions to be incorporated without getting into complex construction techniques. Comes com~lete ~~ gull form1, right down to the last bolt. ~~ at K- 316 lncr,dibly Small/ Lr - · I ~- (~ PHONES I~(.... SECURITY AUDIO COMPUTERS .rt • NSW• Allrf 218399 • BlllblC1W11S.11707 4888• Bllcklawn671 7722 • Ca■illlell awn(046)27 2199• Clllt&weodC11ue4111955 • Cllllll11642 8922 • Gori 1&1439 5311 • Gadanl 25 0235 • Hllmuy 477 6633 • Hmllll 580 8622 • L1vt11001 600 9888 • Mattlllll 33 7866 • Mlnlldl 525 2722 •Nlwl:ISIII 611896 • Nd llydl 878 3855 • Pamt111111 689 2188 • Pllrn (047)32 3400 •Hallway 211 3777 • SW11Y aty 267 9111 • T-~ 661711 • WaniQaliMll9050441•WIIIMlloll283800• ACT • Fymrick804944• VIC• Bil111111315433 • Bllllalit260 6088• llllldllo 43 0388 • Btx Hll 890 06W • C... (03) 383 4455 • DINlllf 794 9377 • Ent 9r1tld011 592 2366 • EasendOll 379 7444 • Fae!~ 689 2055 • Fmb!H783 9144 • llellowt232 7f 1•Malt. . aty3266088• RlcM!old4281614•RIIIIWIOd 8795338 •S,rinplle5470522 • QUJ• BrilUIII CllY 229 9377 • llll1lldl 391 6233 • Calms 311 515 • Cllnslde 359 6255 • lllllllllak 281l 5599 • Rocldtam,ton 27 9644 • S8lllhllert 32 9033 • flOWOll■N 384300 • TIIWIIIYile72 5722 • Ulllllrwood 341 0844 • SA• Ai1111k111 aty2321200• Bfflrfey3471900• St Mans277 8g77 • Biznllll 2556099• Ellllld2606088• WA• CNll11Sn4518666• i:r-tllle3359733 • Nortli1'1!1113286944• MClly4813261•Midlaad2501460• TAS • Houri 31 0800 •NT• S1art l'lrll 811917 ✓Dick Smith Electronics -Still FullorSurprises' 2-Chip Stereo Radio This month, we complete construction of the AM Stereo Radio by giving the alignment details. Provided you follow the instructions carefully, you will finish up with a receiver capable of true hifi performance. By STEVE PAYOR Precise alignment of this receiver is a challenging task, requiring care and patience. The circuit may appear to be working well even before alignment has been attempted, but this is more a testimony to the sensitivity of the MC13024 than anything else. When it is fully aligned, it will work much better. 32 SILICON CHIP To achieve the maximum stereo separation ()25dB) and minimum distortion (<1 % ), the RF and IF response curves must be perfectly symmetrical in both amplitude and phase, either side of the carrier frequency. Not only does the alignment have to be perfect but the tuning must also be spot on - within a kHz or so. Normally, such precision can only be obtained with a digitally synthesised front end. However, this is where the phase locked tuning of the MC13024 comes into its own. Provided the IF circuits are all centred on 450kHz and the reference oscillator is tuned to exactly 8 times this frequency, the PLL will automatically centre the signal carrier on 450kHz whenever it is within the ± 3kHz capture range. Block diagram Before we start randomly twiddling the coil slugs, it would be a good idea to review the way all the tuned circuits relate to one another, so we VOLTAGE CONTROLLED LOCAL OSCILLATOR ··rn ~ Jf, r----1 I I c4 osc I PHASE COMPARATOR TRIMMER 450kHz 981-2052kHz (:t 3kHz-VCO SHIFT) % llffi C3 ,fo 6MHz REFERENCE OSCILLATOR LS 3688 OSCILLATOR TUNED CIRCUIT AERIAL TUNED CIRCUIT f1 PHASE LOCKED LOOP ' CONTROL VOLTAGE L2 T1342 GANGED TUNING (CONSTANT 450kHz DIFFERENCE) 11 450kHz REF 531-1602kHz AERIAL TRIMMER ,fo 2ND IF TUNED CIRCUIT 1ST IF TUNED CIRCUIT MIXER II Ll FERRITE ROD AERIAL COIL 450kHz CERAMIC FILTER SFP-450D L3 T1341 IF AMPLIFIER ro 450kHz IF OUTPUT TO DETECTOR ANO STEREO DECODER L4 T1340 I --- - ----- ~----WIDE -12kHz t +12kHz -12kHz SIGNAL CARRIER FREQUENCY t +12kHz 450kHz -12kHz t +12kHz 450kHz Fig.12: this block diagram shows the tuned circuits that have to be adjusted during the alignment procedure. This involves setting the IF stages to 450kHz, adjusting the aerial and oscillator circuits, and setting the 3.6MHz reference oscillator. can formulate a suitable plan of attack. Fig.12 is a block diagram showing just those circuit elements of importance to the alignment procedure. The response curves of the RF & IF tuned circuits are shown approximately to scale, to help you visualise what is happening with each adjustment. The alignment process has four main aims: (1). Setting the centre frequency of both IF tuned circuits to the centre of the ceramic filter passband (4g0kHz ± 2kHz). (2). Setting the 3.6MHz reference oscillator to exactly 8 times the IF centre frequency. (3). Adjusting the oscillator coil and trimmer capacitor so that the dial calibrations are correct over the whole tuning range. (4). Adjusting the aerial coil and trimmer so that the aerial tuned circuit "tracks" the oscillator over the whole tuning range. Unfortunately, these four objectives cannot be achieved simultaneously by any instant "one shot" alignment process - at least not without a lot of test equipment. Instead, you need to repeat a series of adjustments, with each round bringing you closer to the desired result. Tuning meter The minimum requirement in the way of test equipment is an analog moving coil multimeter (remember those'?). If you don't have one, buy or borrow one now! Digital multimeters are almost useless here as they make finding the optimum adjustment unbearably tedious. If you have a 10M0 FET input type [ie, the equivalent of the good old VTVM), simply connect it between the AGC test point and ground. Alternatively, for a more expanded scale (useful if you are trying to make do with a bargraph display on a digital multimeter), try connecting it between the AGC test point and the + 1.0V reference. The ACG voltage dips slightly below + 1.0V on strong signals and will rise to around + 1.3V when the tuning is way off. On the other hand, connecting an ordinary moving coil multimeter directly between the AGC line and ground will kill the reception. This is because the low input impedance of the meter will pull the AGC voltage down and turn off the receiver gain completely. To overcome this problem, we have provided a "Buffered AGC" test point. So if you are using an ordinary multimeter as a tuning indicator, connect it between the Buffered AGC test point and ground. But regardless of what sort of tuning indicator you are using, remember this: optimum tuning means minimum AGC.voltage. Getting started The following settings are ''ball park" adjustments for all the coils and trimmers, based on our experience with two prototypes: • Slide the aerial coil (L1) along the ferrite rod until it is flush with the end of the rod. • Set the oscillator coil slug (L2) about one turn out of the top of the can. NOVEMBER 1989 33 Fig.13: the 'Sharp', 'Medium' or 'Wide' bandwidth option is selected by bridging solder pads on the PCB. We recommend that you select the 'Wide' option as shown at right. (Note: repeated from last month's issue - see footnote). • Set the aerial trimmer (associated with C3) and the oscillator trimmer (across C4) to half mesh. The aerial trimmer adjustment screw is adjacent to the C3 marking on the back of the tuning gang. The oscillator trimmer adjustment is below the C4 marking. • Set the slugs of both IF coils (13 & 14) level with the top of the can. Don't worry too much about the 3.6MHz reference oscillator at this stage. In fact, it is better left way off frequency to start with. This will disable the phase locked loop and make the initial alignment procedure the same as for any ordinary superhet receiver. (As long as the tuning indicator is NOT lit, you are in control of the tuning). IF alignment This is not a bad place to start but remember that you will have to come back and re-align this part later on, when the other tuned circuits are a bit closer to their final adjustment. Tune in a clear, un-crowded station near the top end of the band and peak the IF coils (13 & 14) for minimum AGC voltage. Temporarily peak the aerial trimmer as well and re-check the IF coils. Now swing the tuning knob a little to either side of the tuned station and, using your ears, locate each edge of the ± 12kHz passband of the ceramic filter. The distortion caused by the steep cutoff at each edge is unmistakable. Temporarily affix a slip of paper under the perspex cursor and carefully mark each edge of the passband, then put the cursor line exactly in the middle. Before starting alignment, the tuning shaft must be rotated fully anti-clockwise and the cursor aligned with the horizontal line on the dial. Don't forget to preload the Teflon washer and tuning gang bearings before tightening the grubscrew. 34 SILICON CHIP Don't worry at this stage that the station frequency doesn't match its location on the dial - this adjustment comes later. Also, if the tuning indicator LED comes on, get rid of it by de-tuning the reference oscillator. Having found the middle of the ceramic filter passband, go back and re-peak the IF coils (13 & 14) and the aerial trimmer again. The reason for peaking the aerial tuned circuit here is to prevent its response peak from masking the true centre frequency of the IF coils. As you can see from Fig.12, the aerial tuned circuit is quite sharp in its own right. This gives the receiver excellent image rejection and cross modulation performance but is a bit of a nuisance during the IF alignment. Getting the dial markings right Contrary to what you may first think, it is the oscillator frequency which determines the receiver tuning and not the aerial tuned circuit. Of course, the aerial circuit is tuned to the signal frequency but it has nothing to do with positioning the signal on the dial. It simply maximises the signal at a given position. To get the cursor to line up with the correct dial marking for a given station, you have to adjust the oscillator coil (12) and the oscillator trimmer capacitor (across C4). The trick is to always adjust the coil at the low frequency end of the band and the trimmer at the high frequency end. First, set the dial to the exact frequency of a station at the low end of the band and peak the oscillator coil for maximum signal. This done, move the cursor to a station frequency at the top end of the band, then move the station to this position using the oscillator trimmer. If you now go back to the low end of the band you will find that the first station has moved slightly (but not very much), so re-adjust the oscillator coil. Now you will find that the station at the top end of the band has moved a bit too, so readjust the oscillator trimmer. After about the third pass, both stations should be spot on. This photo will allow you to quickly locate the various coils and trimmers during alignment. The 3.6MHz reference oscillator (L5) should initially be left way off frequency to disable the phase locked loop (see text). · Getting the tracking right This step can be done simultaneously with the oscillator adjustments but we are describing it here separately for clarity. Basically the procedure is the same: you adjust the aerial coil at the bottom end of the band and the aerial trimmer at the too end. The trimmer adjustment (at the top end of the band) is straightforward but the aerial coil adjustment is a little tricky, since you will have to slide the coil along the rod with your fingers. Now putting your fingers on the coil will de-tune it quite drastically, so it's best to know which way to move it before you touch it! Try this simple test: tune to the exact centre of a station at the low frequency end of the band and note the effect of de-tuning very slightly to either side (by very slightly we mean staying within the flat region of the IF passband). If the indicated signal strength increases to the low side, then the resonant frequency of the aerial circuit is a little low. To correct this, you will need to slide the coil towards the end of the ferrite rod, and vice-versa. So now you know which way to move the coil, although how much is still a matter of trial and error. You must remove your fingers from the coil to check each position. Of course, all this peaking of tun- Where to buy the kit A complete kit of parts for this project has recently been made available by Dick Smith Electronics. You can buy it at your nearest DSE store or by mail order from PO Box 321, North Ryde, NSW 2113 . Phone (02) 888 2105 . The kit comes with all parts & even includes a low-cost pair of headphones to get you going . The front panel is of aluminium & is supplied pre-punched together with an attractive adhesive label. The price is $79.95 (does not include batteries) plus postage charges. Quote Cat. K-5200 when ordering . ed circuits assumes that the IF coils are correctly aligned to start with. Repeat the adjustments for these once more before making the final touchups to the oscillator and aerial tuned circuits. Remember: the oscillator adjustments set the stations to their correct positions on the dial, while the aerial adjustments peak the reception at these positions. Using stations at the extreme ends of the band is helpful for the initial tracking adjustments, since there is minimal interaction between the coil and trimmer adjustments. The final tracking adjustments should be done using stations about one quarter to one third of the way in from each end of the band. This will give a "best fit" linear approximation to the dial positions. With careful adjustment, it should be possible to get the station frequencies within a pointer's width of the station position over most of the tuning range. Setting the reference oscillator Tune to a nice clear station and, as before, mark the approximate passband edges on a piece of paper NOVEMBER 1989 35 Fig.14: these tuning scales are for Melbourne, Brisbane, Adelaide, Perth, Hobart and Launceston, and the Northern Territory. They fit in the blank central area of the tuning dial. One approach is to make a transparency or adhesive label from the artwork (try your local printer), which can then be affixed to the front panel label. Alternatively, you can use a combined artwork to produce a single 3M Dynamark (formerly Scotchcal) label. slid under the cursor. Now set the cursor as close as possible to the centre of the passband as your ears and eyes can detect and adjust the reference oscillator slug (15) with a plastic alignment tool until the tuning indicator LED comes on. Now carefully tune across the passband and note whether the "Locked" tuning range is centred within the audible tuning range. It will be fairly narrow - about 1/4 of the IF bandwidth. If it is a little to the high side of centre, screw the reference oscillator slug a teeny weeny bit out, and vice-versa. Persevere until you have the locking range exactly centred. Note: With the reference oscillator coil, maximum inductance occurs with the slug near the top of the can. The inductance decreases as you screw the slug in. If you find the slug needs to be screwed all the way out to make the frequency correct, try screwing it in instead. Stereo? Once the "Locked" indicator is lit, the receiver should switch to stereo mode if you leave the tuning knob alone for more than 300ms (ie, the LED should jump from half brilliance to full brilliance). If not, then something is amiss with the 25Hz pilot filter circuitry or the station is not transmitting in stereo. 36 SILICON CHIP The stereo mode is much more sensitive to phase errors than mono mode. For example, if you have chosen the Medium or Sharp bandwidth options for the 2nd IF tuned circuit, the alignment symmetry will be quite critical. With the Sharp setting, try detuning 14 ·slightly while listening to a stereo signal with headphones. The sound will appear to go in one ear and out the other, or even rotate around inside your head! Of course, the stereo separation will be thoroughly shot. For this reason, the Wide setting is recommended (at least initially) since it is the least critical with regard to alignment. Other test equipment? If you have a digital frequency meter and are thinking of hooking it up to the reference oscillator, then forget it. Even the SILICON CHIP 1GHz DFM (which has a lower input capacitance than most commercial units) can't get a proper reading, even with a 3pF divider probe. In any case, the MC13024 has a habit of shutting down the reference oscillator at the first sign of any disturbance. The best approach is to set the reference frequency indirectly. Hook the DFM up to an RF signal generator and adjust the signal fre- quency to exactly 450kHz (unmodulated). Run a length of insulated wire from the signal generator and lay it near the MC13024 chip to inject a little of this signal into the IF circuitry. As you tune through a station, you will hear a faint whistle which decreases in frequency until the LED comes on. After that, the whistle frequency will remain constant. This constant audible frequency is the error in the PLL setting so, while the LED is on, carefully adjust 15 until the whistle becomes a low growl, or even a rapid flutter if you are very lucky. Check the adjustment by tuning through the station again. When the whistle frequency becomes less than a few kHz, it should suddenly drop to a low frequency growl (as the LED comes on) and stay there until the LED goes off again. Now you can peak all the IF circuits (13 & 14), knowing that when the LED is on, the IF is exactly 450kHz. However, while this is an accurate way of setting up the reference oscillator frequency for a 450kHz IF, it doesn't help if the centre frequency of the ceramic filter is 2kHz off (worst case). Once again, you should perform an "eyes and ears" verification that the locking range is centred within the filter passband. Final touches With the reference oscillator working, you can now make some last minute touch-ups to the alignment. In particular, the local oscillator can now be precisely adjusted so that the locking range is symmetrical (about one cursor line thickness) either side of the chosen station markings. Also, the IF coils can now be repeaked any time the LED is on, as this guarantees that the IF signal is centred correctly. You will appreciate that this is a classic "chicken before the egg" situation but that's life, as they say. Operating hints If you are listening to " fringe area" stations with headphones, the 9kHz inter-carrier whistle can be annoying, especially at night. In these cases, try rotating the radio to minimise reception of the interfering carrier. The same applies to other sources of man-made interference. On local stations, however, inter. carrier interference will not be a +Trim to outside of board outline + SILICON CHIP AM STEREO Fig.15: the Rev.2 version of the PC board will be available only with the Dick Smith kit (see panel). The Rev.1 version (published last month) is available from the usual suppliers. problem, even if you use the Wide setting. In any case, we plan to describe an add-on whistle filter to improve the audio quality from distant stations. Look for it in a future issue. Finally, if you are driving speakers (rather than headphones) and the stereo mode drops out when you cO turn up the volume, it's time to change the batteries. Footnote: unfortunately, the colour overlay for Fig.5 in last month's issue was not precisely positioned. To eliminate any confusion about which pads to bridge, the diagram is reproduced in this article as Fig.13. ~ AUDIO TRANSFORMED FUJITSU MEMORY • DYNAMIC RAM 25 6K X 1 DUAL IN LINE PKG MB8 1256- 10P 100ns 5.00 1 Mb 1 Mb 2 56K 2 5 6K MB 81C1000- 10P MB S 1C 1000- 10PS Z MB 8 1C 4256 - 1OP MB 8 1C 4 256-10 PSZ 100ns 100ns 100ns 100ns 19.50 X X X X 1 1 4 4 CMOS CMOS CMOS CMO S DIP ZIG DIP ZIG PACKAGE ZAG PKG PAC K AGE ZAG PKG 4 Mb x 1 CMOS DIP / ZIP PK G 1 Mb x 4 CM OS DIP/ ZIP PKG MBB 1C4000-80P/ PSZ MBB 1C4400 - 80P/PSZ BOns BOns P .O.A . P.O.A. • STATIC RAM SK X 8 CM OS DIP LOW POWER BK X 8 C MOS SK INNY DIP LO W PW R 3 2K X 8 CMOS DIP LOW POW ER 32K X O FULL CM OS LOW LO W PW R 128K X 8 CMOS 1 Mb LOW POW ER MB8484 A- 10LP MB8464 A - 10LP- SK MB B4 256-1 0 LP MB8 4F256 - 20LP MB 84 1000-10P 1oons 6.00 100ns 100ns 200ns 100ns 15.50 P.O.A. P.O.A. • Add 20% Sales Tax / $5.00 P & P PACIFIC MICROELECTRONICS PTY. LTD. Suite 7, 1st Floor Westlelgh Centre, Eucalyptus Dve, WESTLEIGH N.S.W. 2120 PHONE : 02 481 0065 FAX : 02 484 4460 AUSTRALIAN REPRESENTATIVE FUJITSU MICROELECTRONICS PACIFIC ASIA LTD. FOR PROFESSIONAL, OEM OR AMATEUR Broadcast qua lity aud io transformers ex-stock More than 70 standard types ava ilable Fast prototyp ing service for non-sta ndard types Comprehensive data availab le o n request Local ly manufactured Compet iti vely price d HARBUCH ELECTRONICS PTY LTD 90 George St. HORNSBY >!SW 20 77 Phone (021476-5854 N OVEMBER 1989 37 Prices like you'd got a PC GAMES PORT JOYSTICK CAT.ACJOY These Joystick are ruggedly constructed to withstand the rigours of enthusiastic playing. • Easy fingertip control of the "fire" button. GET50%MORE HARD DISK CAPACITY WITH RLL CONTROLLER • Automatic spring return on both axes for autocentring • Terminates in the games port standard 15 pin male connector. only$30 TICK TOCK CARD CAT. DCAHR The clock card is a battery backed up real time clock/calendar. It is supplied complete with software to set the time and date. only$50 DISK DRIVE PARADISE NEW!! PC/XT HARD DISK controller Our new RLL (run length limited) hard disk/floppy disk controller boosts hard disk capacity and data transfer rate by 50%. It provides a high performance 2, 7 RLL-encoded hard disk control for IBM AT and 386 systems with interleave factors upto1:1. • Data transfer rate of 660KBytes/Sec • 50% more formatted capacity from the same drive • Works at up to 16MHz bus speeds • Cabling is supplied. Incorporates floppy disk controller system, which caters for 1 or 2 floppy drives, which may be of any type, either 5¼" or 3½", 360K. 1.2MB, 720K or 1.44MB capacity. Multi 1/0 Card CAT. 10-1005 This card suits all IBM PC/XTs. Features include: • An IBM standard parallel printer interface. It can be configured as LPT1:, LPT2: or LPT3: • An IBM compatible serial interface (with a second port as an option.) • Garnes port, compatible with standard joy-sticks • A Real-Time clock/ calendar with rechargeable Ni-Cad battery. • A fully industry standard Microsoft Bus Mouse interface. It uses a mini DIN jack, compatible with all bus mice. • An industry standard diskette drive controller. It can control two of either 5¼" or 3½" drives, in all standard formats, including 1.2MB, 360K, 720K and 1.44MB only$129 Big Tower Case When you have big things in mind, this case is the solution. Bays for up to 6 storage devices, 220W heavy duty power supply. Without power supply CAT CATOWER6 only$299 With power supply CAT. CA1POWER6P only$492 14 11 AMBER or GREEN MONITOR CAT.ACMG only$249 Miniscribe model CAT. DC-2200 Baby AT Tower Case Fully back compatible with the Western Digital WDXT-GEN2 controller used in the old machines, as well as those used in the latest turbo XT machines. • Controls up to 2 hard disks via ST-506 interface • Supports drives up to 1024 cylinders and 15 heads only$145 8425 20130MB Drive The perfect companion to the controller above. This precision US manufactured drive provides 20MB of storage (30MB with RLL controller), with speedy 65mS access time. only $349.00 The perfect answer for building your own AT. Available with or without 200W AT power supply. • Compact design • Bays for 2 x 5V4" and 2 x 3½" drives. Includes all fittings etc. Without power supply CAT.CATE only$149 With power supply CAT. CAT.PB only$299 TTL Monochrome monitor. The models ACMA (amber)/ ACMG (green) are high-resolution TTL monitors, designed to work with the hercules compatible graphics video adaptors. The monitors have 14 inch flat screen, antiglare tubes, making them an excellent choice for both text and graphics. only$199 relative in the business!! VGA MONITOR LA9F25M LA9M25F LAAPS2 LAAVGA LACFDD LACHDD20 LACHDD34 LACM25 LACM9 LACPP3 LACPP5 LACSP25 LACSP9 LAGC25F FAGC25M LAGC9F LAGC9M only$749 EGA/VGA MULTISYNC MONITOR CAT.ACMM EGAMONITOR CAT.ACMEGA A dot pitch of 0.31mm and non-glare tinted screen make this monitor ideal for enhanced graphics and applications requiring colour graphics generally. The Multisync monitor features a 14" colour display whi.ch automatically scans all between 15.5-35kHz (horizontal) x 50-70 (vertical) with TTL and analog inputs. It is suitable for CGA, EGA and VGA operation up to 600 x 800 dots.A text mode switch provides monochrome displays. only$599 only$899 ~~= . . . :~ ;~ LEADS AND ADAPTORS CAT.ACWNGA Full analog 14" VGA colour monitor with a resolution up to 640 x 480 dots. 30MHz bandwidth and .31mm dot pitch make it suitable for both text and graphics. LANULL LAOT 1~:~:~ g~ ~;,5 ~:al~ ~ 2 8 .,iVW+.:'.B"<at>· .·.·•••.i. •..·. .. Adaptor, PS2 -AT keyboard.. ....... $9.75 Adaptor, VGA to DB9F .. ....... $9.75 Floppy disk drive cable.. ....... $9. 75 · '"'· ' Hard disk cable, 20 way ................ $9.95 Hard disk cable, 34 way .............. .. $12.00 Modem cable, D25F to D25M ........ ... $15.75 Modem cable, D9F to D25M . .... $15.75 Parallel Printer Cable, 3 metre ..... ..... $15.00 Parallel Printer Cable, 5 metre .......... $18.00 Serial Printer Cable, D25F to D25M .. $15.75 Serial Printer Cable, D9F to D25M .... $15.75 ··'"":!<~~""' Gender Gender Changer, Changer, D25F D25MtotoD25F D25M........ .. .... $9.75 $9.75 . .. Gender Changer, D9F to D9F.. .. ..... $9.75 Gender Changer, D9M to D9M ......... $9.75 Adaptor, Null Modem.. . ...... $9.75 . Serial Quick Tester ..... $19.90 ,<at>1i©llliwi> .· Ethernet Network Cards We've slashed the cost of high performance networking. These cards are fully compatible with all industry standard networks including Novell NetWare ™, Gateway G/Ethemet, DECnet-DOS, PC-NFS, TCP/IP NetWare 3+, OS/2 LAN Manager, UNIX/XENIX, NetBIOS and APX. The Amazing 11 all-in-one 11 AT motherboard CAT. MB286AIO This is a 12MHz zero wait-state PC 'AT' Computer - complete on the motherboard (minus a video card). With the "All in One", you can build up a complete AT, with power supply, case, drive, keyboard and graphics card for as little as $1298. See article in August Silicon Chip for full details. NE-2 Ethernet Card NE-1 Ethernet Card CAT. NEE2 CAT. NEEl A full 16 bit Ethernet card, it supports NetWare and all Gateway communications products. • Compatible with 8 or 16 bit slot. • Novell NE2000, Gateway G/Ethemet compatible • Supports NetWare, APX and Gateway, G/X25 Gateway and G/Remote Bridge. • Includes T Adaptor A high performance 8-bit Ethernet card • Compatible with 8 or 16 bit slot. • Supports NetWare, NetBIOS, APXetc. • Includes T Adaptor only$449 only$399 Ethernet Accessories Diskless Boot ROM suit NEE1 CAf. WERBL. .............. ...... . $35.00 Diskless Boot ROM suit NEE2 CAT. WERB2$35.00 25' Thin Ethernet Cables ······························$35.00 Ethernet Terminator ......... ... $12.75 Call for further information . •••••••••••••••••••••••••••••••I : ~ ~~ Electronic Solutions I I Box 426 Gladesville 2111 : p I Phone (02) 906 6666 ■ Fax(02)9065222 I Freight on smaller items is now $9.00 + $2.50 P&P. : .,_..,__ .~-.,, : '-------il llllillllli•----I I I • We accept Bankcard, Mastercard & VISA mail orders our specialty. I : • Superior performance (with video and disk running at processor speed) • Around half the price you'd pay for the same thing "in pieces". • Up to 4MB can be fitted onto the motherboard - no need for memory expansion cards. Uses 256K or 1MB chips. • Two serial ports and one parallel port on-board • On-board floppy drive disk controller for both 5¼" and 3½" drives • All cables for ports and floppy drives included only$545 I • All prices include sales tax ■ ■ I I • Note: Products may vary in appearance from those pictured. In all ■ I I I : ■ cases they will perform to the same or a better standard. • All products carry a 14 day money back guarantee (software excepted) • All products carry a full 3 month warranty • All cards come with full documentation . Ring for quantity discounts and tax free pnces • I I : ■ I 1 ••••••••••••••••••••••••••••• J REMOTE CONTROL By BOB YOUNG Modern radio control systems This month, we will be taking a look at the main features offered by modern radio control systems for model aircraft. Among the most useful of these is the "buddy box" system of dual control used when an instructor is training a modeller to fly. Modern radio remote control systems for models are based on a transmitter (Tx} with built in control levers or steering wheel, a telescopic antenna and a battery pack (Fig.1}. The electronic circuitry includes an RF section of less than 1W (typically 500mW) and an encoder which converts the control stick · positions to a serial data stream. The modulation can be AM (amplitude modulation) or NBFSK (narrow band frequency shift keying) with a typical shift of ± 2.5kHz. The data stream may be encoded in PPM (pulse position modulation) or PCM (pulse code modulation) format. Typical figures for a PPM system are: frame rate 20ms; neutral 1.5ms; control 1-Zms; and identification interval Bms (Fig.2}. The receiver (Rx) has a separate battery pack and sockets to accommodate one or more servos (Fig.3}. The antenna is .usually a piece of flexible hook-up wire about 1 metre long. The Rx usually includes an RF section, a mixer/oscillator stage, a single conversion IF, an audio amplifier and a serial to parallel decoder. Adequate DC filtering and regulation is very important to eliminate servo noise. The servos are the muscles of the system and supply the power required to move the control surfaces or wheels etc. These items are marvels of modern technological achievement and can respond to the decoded signals with errors of less than ± 0.25° at the servo disc (or arm) with a high degree of reliability. Each servo consists of a small electric motor, an electronic amplifier, a gear train, a plastic housing and a feedback potentiometer, which is driven by the output shaft of the servo. This potentiometer provides the positional information to the servo amplifier. Each servo is fitted with a disc or arm (often called a "horn") which couples to the control pushrod. Batteries This modern transmitter boasts a range of features, including channel mixing, dual rate control, trim adjustment and servo end point adjustment. It employs frequency modulation and can control up to seven channels. 40 SILICON CHIP The batteries are the heart of the modern R/C (radio control) system but these items are also the number one killer of models. Modellers using cheap nicads in an airplane do so at their own peril (and that of everyone around them). In use, Rx nicads are called upon to deliver anything up to four amps for very brief periods in a 4-servo system. The situation is even worse in helicopters because all four servos are running continuously. .1/I "/ /4) AUX 2 (IF FITTED) OH TOP FACE 3 <at>AUXt(•RTTED) ~ / Transmitter Fig.1 illustrates a typical layout of a radio control Tx. However, there are as many transmitter layouts as there are manufacturers these days, so Fig.1 should be taken as a guide only. The technological explosion common to the electronics field in general has also hit the model business. Consequently, transmitters have suddenly sprouted a great profusion of knobs, dials, switches, FUNCTION 1 2 3 4 5 6 MOTOR AILERON/RUDDER/STEERING ELEVATOR RUDDER AUX 1 (RETRACTS ETC) AUX 2 (FLAPS ETC) Fig.1: this diagram shows a typical transmitter control layout, together with the stick allocations. The gimballed stick assemblies drive two potentiometers to provide control of aileron, throttle, rudder and elevator. 140 A 500 milliamp-hour (mA.h) battery will last for approximately 2½ hours in an aircraft and 45 minutes in a helicopter. For this reason, the minimum safe battery requirement for helicopters is 1.2 amp hours (A.h). When I see nicads designed for calculators in a receiver battery box, my heart sinks. The situation in a Tx is quite different, the typical current consumption being a constant 150mA. Calculator batteries may be OK but there are many considerations to take into account in this very important section and all will be dealt with fully in due course. CHANNEL digital displays and the like. Most of it, from my observations, appears never to be used by the consumer. Likewise, the internal electronics have undergone the same revolution, with AM (amplitude modulation) being displaced to some extent by FM (Frequency Modulation) and PPM (Pulse Position Modulation) being displaced by PCM (Pulse Code Modulation). To simplify the explanations in this series I will confine the discussion wherever possible to the still very common, reliable and inexpen~ sive AM PPM system which served us so well for 20 years. These systems use two gimbal stick assemblies as the primary mechanic- al controls (Fig 1). The principles applied in this system are still used in the others to a large extent, servos, for example, being interchangeable between all three systems. The minimum number of channels required for powered aircraft use is three: rudder, elevator and throttle. Model cars and boats can be operated quite successfully on two channels (steering and throttle) but even here the modern trend to sophistication is calling for gear shift and 4-wheel drive in cars, and mixture control and trim tabs on boats. The table in the corner of Fig.1 shows the typical channel number- CARRERf MODULATION FRAME C1 C2 C3 C4 1-2ms FRAME: 16111s 4CH 20ms &CH NTIFICATION: 8ms Fig.2: the modulation frame for a 4-channel PPM system. Control is affected by altering the positions of the pulses with respect to the start of the frame. NOVEMBER 1989 41 AERIAL 27 !,, PLUG IN CRYSTAL DDfRIF ND AILERON FITTED) ~p TWO MULTI CONNECTORS FOR 8 CHANNELS- (J l ,, BOTH THE SWITCH AND ...___ THE CHARGING CONNECTION CAN BE MOUNTED IN THE ( SIDE OF THE PLANE, CAR ETC, BUT NOT A BOAT,,_,....,_ _ ~ ~~~~~f.!!~ ' TO CHARGER CiNNECTIDN Fig.3: typical arrangement for a multi-channel airborne system showing the servo allocation for each channel number. The on/off switch and the charging connection are best mounted on the side of the fuselage. The battery pack should be rated at 500mA.h for aircraft and 1.2A.h for helicopters. ing and allocation of stick movements. The control gimbals are arranged to give a complete 360° of movement, thus enabling accurate mixing of two controls simultaneously. These gimballed stick assemblies are used to drive two potentiometers, one for each control channel. In operation, the output from each stick pot in the transmitter is slaved to the feedback pot in the servo via the encoder, decoder and servo amplifier electronics. This is termed "proportional control" and is the magic ingredient in modern radio control systems. It now means that if 7.5° of control deflection is called for, then that is precisely what we get (with an error of possibly ± 0.25°). In practice we do not fly like that but merely use the sticks to point 42 SILICON CHIP the model in the direction required. In other words, we fly by feel. But it all comes back to having that delightful, highly accurate coupling between the control stick and the servo. Of course, there are differences of opinion over which is the best way to combine the primary controls of the aircraft on the Tx gimbals. To understand this, consider that a model aircraft usually requires a minimum of four channels for successful operation (I am sidestepping the 3 channel argument for simplicity). These four channels control the ailerons (roll axis), elevators (pitch axis), rudder (yaw axis) and throttle (speed). There are two popular configurations for the control gimbals: (1) aileron/throttle on the right hand stick (Mode 1); and (2) aileron/ elevators on the right hand stick (Mode 2). The rudder is always on the left hand stick, combined with either throttle or elevator (depending on which mode is used). Now much ink has been spilled in bitter arguments by the experts on which mode is the best and I have no intention of opening this debate again. I prefer Mode 1, having started on Mode 2 and changed. The purists prefer Mode 2, arguing that full size aircraft have the aileron/elevator controls combined and therefore so should models. The big problem is that, in a full size aircraft, you use a fully articulated wrist, elbow and shoulder; in models you have only a thumb planted firmly on top of a small control stick. In the end, it is all a matter of personal preference but an important choice nonetheless. If you pick a mode that doesn't suit you, your ability to learn to fly may be seriously impaired - my years of instructing taught me that. Often, the deciding factor is the mode used by the instructor at your club. For this reason, there is often a predominance of one mode or the other in certain clubs. However, please remember this point: it is your ability to learn to fly that is at stake here and the final decision should be yours. While on the subject of learning to fly, I feel a bit of good advice is in order. Join a club and take advantage of the available instructional program. It will save you much heartache and unnecessary expense. Model aircraft are very difficult to fly and it takes almost as much time to learn to fly them as it does for a full size aircraft. Six hours of instruction from beginning to solo is a common figure. The big problem here is the complete lack of feel for the aircraft by the pilot (apart from the visual feedback). This interestingly enough is shortly to be overcome in some new sets about to hit the market. In these sets, a down-link transmission from the aircraft servos on a separate frequency will be used to provide feel for the control sticks. Incredible! Trim controls Two trim controls (one for each axis) are adjacent to each gimbal assembly to provide fine trim for the controls. These are usually called trim levers and provide about 15 % of the full range of movement. An aircraft can change trim for various reasons during a flight and some in-flight retrimming may be required. This eliminates the need to hold the stick off-centre during flight. If only three channels are used, the rudder servo is usually plugged into the aileron channel, so that the primary steering control is under the right thumb. There are many very interesting Tx layouts provided for cars, the most interesting being those with a steering wheel and throttle trigger in place of the control sticks. These are very popular and provide quite a natural feel. The photo on the following page shows Tx development taken to its logical conclusion. Here, the •••""h •• .:. • ..:>, The servos are the 'muscles' of a radio control system. These three units are from a model aircraft and plug directly into the 7-channel FM receiver at bottom left. A plug-in crystal sets the receiver frequency. transmitter circuit and the controls are built into a chair in which the pilot sits (the picture shows the author in his younger days). It's very strange at first but quite interesting once you are used to it. Transporting the chair is a problem, though. Auxiliary channels The auxiliary channels are usually very simple. Typically, they include a toggle switch for a retractable undercarriage (if fitted) and slide controls for the flaps and fuel mixture (needle valve on the motor) etc. Most transmitters will also have some sort of meter and this can serve one of two functions. The more common but less useful type functions as a battery voltage indicator while the more useful type functions as a Tx output meter. An output meter does have one drawback, though - it will change reading according to hand position and extension of the antenna, which leaves the user unsure of the true reading. However, when used correctly (ie, antenna fully extended and vertical, and both hands on the Tx case), they give a good indication of both Tx output and battery voltage. Buddy box One very useful feature in a model aircraft Tx is a "buddy box" or dual control system. This is not very common these days, which is a shame for it really does make learning to fly much less of a chore; In this system, two transmitters are joined with a plug-in cord. A pushbutton switch on the master Tx is then used to select modulation output from one transmitter or the other. In operation, the instructor holds down the momentary thumb switch, thereby passing control of the aircraft to the pupil. If there is an emergency, he simply releases the switch and transfers control to his own transmitter. This system saves the instructor from having to wrestle the Tx away from the pupil if there are problems. Indeed, some pupils will NOVEMBER 1989 43 In this novel arrangement, the transmitter circuit and the controls are built into a chair in which the pilot sits. It's very strange at first hut quite an interesting way to fly once you are used to it. withhold the Tx, insisting that they have everything under control right up until the moment the model starts digging a hole. It's very annoying for the instructor when this happens. I recall one incident when my son returned the Tx to me one microse- · cond before the model hit the ground and then complained for the next 15 years that "Dad crashed the model". Still, that's not quite as bad as my first multi-channel flight. I pulled the wings off the model during a steep turn and then, as the fuselage screamed down like an arrow, handed the Tx to MY instructor and said "Here, it's all yours". As stated previously, learning to fly is not easy and some instruction is a great help. Encoding features The old half-shot encoder which formed the basis of R/C sets for 15 years (circuit included in next mouth's column) was not very flexible electronically. It has now been replaced by modern multiplexed encoder ICs (eg, the NE5044), allowing a whole host of new features to be added. These include: • Servo reversing a slide switch is provided on the Tx to invert the pulses on each channel, 44 SILICON CHIP thus reversing the direction of travel of the servo. This feature calls for a deal of caution on the part of the user in case take-off is made with the servos reversed. For this reason, all control throws should be checked for correct direction of travel before the first flight of each day. This advice applies even if you are using a Tx without servo reversing. It only takes a pushrod to be accidentally replaced on the wrong side of a servo to wreak havoc. With servo reversing, it is even easier to come undone, especially if two models are used with the one transmitter. I have seen the odd pilot who is clever enough to fly with reversed controls but they are rare indeed. • Servo end point adjustment (EPA) - this is a very useful feature and quite safe to use. It is especially useful for throttle adjustment where it is undesirable for the servo to run up against the end stops. Running a servo against the end stops increases current drain and can burn out the servo motor and amplifier. This in turn can flatten the batteries and lead to Rx failure in the model. A small potentiometer (one for each channel) is used to adjust the servo travel to overcome this problem. If the Tx does not have EPA, the system must be set up carefully to avoid these problems. • Dual rate - this feature involves a switch and an associated pot on the front panel of the Tx for one or more channels. The pot is adjusted to set the overall percentage of servo travel available (0-100%) with full stick throw. On half rate, full stick throw will only deliver 50% of the available servo travel. Returning the dual rate switch to the off position restores the servo travel to 100%. This feature is useful for high speed flight where the controls become very sensitive around neutral. It does, however, require some care on the part of the pilot. In particular, the position of the dual rate switch should be checked before commencing any manoevre, especially outside loops. I have seen models crash because the pilots started a manoevre too low to the ground in the belief that they were in high rate when in fact they were in low rate. It is very awkward to get to the rate switch in time if this error is made. To my mind, the dual rate feature has been dated by the introduction of the exponential system. • Exponential control - often switched in by an external or internal switch, this feature gives electronic damping of the servo throw around neutral. As the name implies, the control throw follows an exponential curve, with less throw close to neutral and greater throw as the stick moves to the extremes. The advantage here is that the control response of the aircraft is always constant whereas with dual rate, two sets of reflexive 'responses must be developed. • Battery pack - all transmitters use a built in battery pack made up of either conventional or nickel cadmium cells. Because the Tx places few demands on the battery, with only about 150mA of current consumption, low-cost batteries may be used with comparative safety. Well that's it for this month. Next month, we'll look at the electronic considerations that go to make a good Tx. •§;] wpoD FOR CHIPS ... WOOD FOR CHIPS ... 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Features Weller closed-loop method of controlling maximum tip temperature to protect temperature sensitive components. • Grounded tip protects voltage and current sensitive components. • 48W stainless steel heater construction • Non-burning silicon rubber cord • 15 tip sizes - 0.8mm to 6.00mm diameter e 11secs to recover for 37°C drop • Choice of lip temperatures 315°C/ 600°F 3?0°C/70°F 430°C/800°F ~ :i:CJ ' . ' $137.00 a 5 5 5 3 3 1/4 1/4 1/4 1/2 1/2 Bulk Packs Filesafe OS Filesafe OS Filesafe OS Filesafe OS $6.50 $18.50 $34.95 $39.95 $69.95 OD HO OD HO All Prices per Pack of Ten Disks. iH111i -6041 terface d oa • • • • D ILL 'N DRIVE 1940 ne Points 8 bit PC Bus Connector Extra 25 way Female D Connector Ideal for lashing up those PC projects et 0 I.I. Q 0 9 Way Male to Female 15 Way Male to Female 25 Way male to Female ~ All 10.95 each - • Electronic Temperature control to within ±6°C over the range 177°C to 454°C • Three digit LED readout with ±1 °c resolution • Temperature control maintained for ±10% supply variation • Rapid response platinum temperature sensor with full proportional control • Thyristor power control with zerovoltage switching • Grounded tip • 42W/24Vac transformer operation • 10 second recovery • 14 tip styles - 0.8 to 5.0mm diameter $195.00 Pack of 4 high speed drill bits 0.6, 0.8, 1.0 and 1.2mm $6.50 Milling cutters Set of 3 $7.95 Wire brushes Set of 3 $14.40 Grinding bits Set of 3 $10.95 Cutting discs Set of 6 $10.95 E,aser sticks Set of 10 $3.50 Rechargeable two speed drill and screwdriver Features • Two Speeds Drill - 325 rpm, Screw-driver - 150 rpm • Forward and reverse operation • Pilot light for dark areas • Drills timber , metal, hardened plastic Supplied with Rechargeable Batteries AC Adaptor 3 Drill Bits 2.0, 3.0, 4.0mm 2 Slotted Screwdriver Bits 2 Philips Screwdriver Bits Incredible Value at only $65.00 tors e 101 Keys Fully Expanded Keyboard • Silent Tactile Switches • Curved Low Profile Keylops • Curled Lead With 5 Pin DIN • Extremely versatile. • All O.5metre long • Male and Female to Male and Female Yes folks you get both sexes on each end! D89 0B1 5 ONLY $129. 00 0B25 $22.95 $24.95 $26.95 1-'o Features • Dual 400/600 •c Temp Range e 1600 Watt output • Built-in safety handle • Hanging hook for storage • 12 month warranty A necessity at GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road, (Corner Beatrice St.) INC INNsw Lane Cove West, N.S.W. P.O. Box 671 , Lane Cove N.S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $5.00 to cover postal charges. Next day delivery in Sydney add $5.00. PENROSE All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED $59.95 AMATEUR RADIO By GARRY CHATT, VK2YBX A two-tone oscillator for testing SSB transmitters This simple two-tone test oscillator will allow you to correctly adjust the output of an SSB transmitter to prevent splatter. It uses just three low cost transistors and can be quickly lashed up on a piece of Veroboard. As most amateurs are probably aware, an incorrectly adjusted SSB transmitter can be the cause of adjacent channel interference or "splatter". This is a most undesirable situation. It not only in conveniences other amateur operators but can also cause interference to television and radio (a) reception which should be avoided at all costs. By monitoring the output waveform of an SSB transmitter, this problem can be detected and then eliminated by correct adjustment of the ALC (automatic level control) and modulation circuits. This can be done using a test signal from the (b) Fig.1: the output waveform (a) for a correctly adjusted transmitter and the resultant spectrum analyser display (b), The IMD products are suppressed by 30dB or so with respect to the output signal. 00 00 Fig.2: the effects of an overdriven output stage. The output waveform is flattened and the IMD products now cause splatter. 46 SILICON CHIP oscillator described here. It provides two test tones: one at 500Hz and the other at 2.4kHz. Spectrum analyser Perhaps the best way of monitoring the output of any transmitter is to use a spectrum analyser and sample the output at a convenient level. Fig.1 shows the output waveform of a correctly adjusted SSB transmitter. As can be seen, the two test tones are clearly visible and the intermodulation distortion (IMD) products are suppressed by 30dB or so with respect to the output signal. Hence there is virtually no adjacent channel interference. The corresponding modulation display is sinusoidal, showing no sign of an overdriven modulator. While this is not a foolproof relationship, (ie, there can be other causes of high IMD products in the transmitter output), Fig.2 clearly shows the effect of an overdriven output stage. The modulation waveform shows considerable flat topping and the result on the output can be seen on the corresponding spectrum analyser display. The frequency spread of the transmitter IMD products is sure to cause "splatter" on adjacent frequencies. Of course that is all very well for those amateurs fortunate enough to have access to a spectrum analyser. However, if you at least have or can gain access to an oscilloscope, monitoring the modulation output waveform is a valuable and simple method of predicting the purity of the transmitter output signal. .----------------------0+10-12v CS R6 PARTS LIST + 4.7J: R1 47k R9 470k 1 piece of Veroboard 1 plastic case 3 BC549 NPN transistors 2400Hz 100k C1 C4 .0082 .0018 ....__ _ _ _ _ _ _ _ _ _ _ _ _ _ _....._.....__ _ _ _ _ _ _--nGND Fig.3: the circuit for the two-tone test oscillator. Ql & Q2 form the 500Hz and 2400Hz oscillator stages. Their outputs are mixed in VR3 and fed to Q3 which functions as an emitter follower. VR4 allows the output to be adjusted to a suitable level for the transmitter. CRO checks A simple and practical method of checking the linearity of an SSB transmitter is to inject two harmonically unrelated frequencies into the microphone (or microphone socket direct) and observe the output on an oscilloscope fed with an RF probe and detector. The two tone oscillator has constant output which makes transmitter adjustment somewhat easier than repeatedly whistling or screeching into the microphone! If an oscilloscope of sufficient bandwidth (ie, higher than the transmitter frequency) is available, the RF output signal can be observed directly. If the modulator/ transmitter has good linearity, the modulation pattern will be as close to a pure sine wave as possible (Fig. t). As distortion increases, so do the spurious transmitter products (Fig.2). So it is prudent to operate an SSB transmitter under the cleanest modulation conditions possible. In practice, it is wise to operate the transmitter at voice levels slightly lower than the level achieved using a two tone input to ensure that the modulator is not overdriven. Circuit details The two tone "oscillator" described here actually contains two separate oscillators, one operating at the nominal lower audio frequency limit likely to be encountered in actual use, and the other operating at the highest nominal audio frequency. Even though most amateurs regard the "speech" limits of most audio circuits as 300Hz to 3000Hz, in practice 500Hz and 2400Hz are the more likely limits. Fig.3 shows the circuit diagram, which is very simple. There are two separate oscillators, involving Qt and Q2, which are almost identical Sallen-Key active filters, with a high level of feedback to induce oscillation. Some readers will recognise them as conventional transistor phase shift oscillators. Their outputs typically have quite a low level of distortion. Transistors Qt and Q2 oscillate at 2.4kHz and 500Hz respectively. Both audio outputs are fed to VR3 which is a tMO trimpot. This serves as a crude mixer while providing sufficient isolation to ensure that the two oscillators do not "pull" each other. Trimpots VRt and VR2 are used to trim the frequency of each oscillator. The output from VR3 is fed to Q3, an emitter follower, which provides an output with an impedance of around tkO via a tkO pot (VR4). The ---------o+10-12V SQ SPEAKER Fig.4: this optional power amplifier stage can be used to drive a loudspeaker. It's based on a single IC. Capacitors 1 1 OµF 16VW electrolytic 1 4. 7 µF 16VW electrolytic 3 .0082µF metallised polyester 3 .0018µF metallised polyester Resistors (0.25W, 5%) 1 470k0 6 1 OOkO 2 47k0 1 1 kO 1 1 MO trimpot 2 1 kO trimpots 1 1 kO pot. Optional power amplifier 1 LM386 audio amplifier IC 1 250µF 16VW electrolytic 1 1 OOµF 16VW electrolytic 1 1 OµF 16VW electrolytic 1 150 0.5W resistor output is capacitively coupled and could be fed directly into the transmitter microphone socket. The output level can be varied using VR4 to a level suitable for most transmitters. A further addition can be made to the circuit to enable the oscillator to drive a speaker, which can then be held close to the transmitter microphone if direct connection to the transmitter is not desired. Of course, the frequency response of the speaker must be taken into account. A speaker having sufficiently wide bandwidth is required so that both tones are presented to the microphone at much the same level. In practice, the use of a communications type external speak-er is acceptable, even though the efficiency of the actual speaker may be less at 500Hz than it is at 2400Hz. You will find that the speaker housing helps compensate the lower frequency level. The power amplifier used in our circuit is the LM386, which is connected using a minimum number of components to provide a gain of 20. The entire unit could be easily built into a "jiffy" box on Veroboard and could even be powered by an internally mounted 9 volt battery. ~ NOVEMBER 1989 47 You've got to be Sharp in this gaille This month's main story has many claims to fame - if 'fame' is the right word. It set something of a record in time taken to obtain a spare part and also a record for patience on the part of the customer. And on the bench it made another record bid; no less than four faults when only one was suspected. The story started when I was called to the local school to do a routine repair job on the PA system. It was the commencement of a term and I encountered a new principal who had just been transferred from a school in the far south of the state. The full significance of this last point was not appreciated until much later. After I fixed the PA system, we began chatting and he soon raised the matter of VCRs. Did I service these devices? When I said I did he explained that he had a VCR which was faulty and that it had had a checkered history of service. In fact, he had some very nasty things to say about the serviceman concerned which I would not dare repeat in print. But briefly, it appeared that it had been serviced on two or three occasions for various faults and after the last service, the present fault had appeared. So could I fix it? That was something of a leading question but sticking my neck out, I said yes assuming it was capable of being fixed economically. And feeling that the industry owed him something, I emphasised that if the repair appeared not to be economical, there would be no charge for the advice. He accepted my offer and added that he didn't care how long it took to fix the thing - just so long as it was genuinely fixed in the end. I doubt if either of us guessed how long it would really take but he was 48 SILICON CHIP as good as his word; not once did he pressure me. Naturally, I needed to know the nature of the complaint and as much of its history as possible. He was a bit vague about this. Basically, it was a failure to reproduce colour but more importantly, it was intermittent. I tried to determine whether this was a recording fault - was it only on tapes he recorded or also on pre-recorded tapes? but it seemed that he had not noted this distinction. Anyway, he duly delivered the machine to the shop. It turned out to be a Sharp VC-483X, a model of about four years old and one for which I had a manual. At the first opportunity I set it up, pushed in a tape and made a recording. There was no colour on playback and none when the tape was played in another machine. On the other hand, the machine would play a pre-recorded tape in full colour. OK, so we had a fault somewhere in the chroma circuitry. My next step was to open the machine and check for anything obvious. My first stop was the Y/C (luminance/chrominance) board which sits above the drum and transport mechanism. It is mounted component side down and is covered with a clear plastic sheet. Bodgie pot And did I find something "obvious"? One glance was enough; someone, presumably the previous N\"( FIRST s-rz::>p Wf=I\S 11-tE Y/C (LUM\NANc.£. CHROMINA~C£)SOAR'D WI-'\~ Sl"t'S A'SOV~ ~ 1'RUIV\ic-~, ~Ar-J\~N'\, MOUl\r\""ED COIY\f>~ S\De; t>OWN &GO~Wt~A a...€A~ 1)f.A~C 'SH"1'" serviceman, had attacked the copper side of the board and made an unholy mess of it. There was also a small trimpot which had been added and which obviously didn't belong there. Backtracking through the circuit and wiring patterns provided some clarification. The bodgie pot was a replacement for R508, a lkn pot used to set the choma record level. In its original form, it is a much smaller unit (about 5mm in diameter) and is normally mounted on the component side of the board. But it wasn't just the bodgie pot that shocked me. It was obvious that a number of other components in this part of the circuit had been removed and replaced with new components, and equally obvious that it had been done by someone who had never come to terms with proper soldering techniques in modern equipment. In short, it was a mess, with great blobs of solder around the various joints, plus a fair share of surplus blobs and slivers scattered around the board. The wonder was that the consequences had not been more spectacular. As to the reason behind this mess, one can only speculate. My guess is that it had started with the loss-of-colour fault, possibly intermittent, and that the serviceman had changed or tested all these components, including the pot, in an effort to track it down. That's fair enough as far as it goes. My real gripe concerns the shockingly poor manner in which it was done. Cleaning up The first thing to do was to get stuck into the board and clean it up. This I did and even if I do say it myself, I was able to get it back very close to its original condition. The only sour note was the bodgie pot for which I had no replacement and which had to be ordered. But at least I had eliminated any potential shorts and dry joints. Then I tried the machine again. And lo and behold, it worked; a perfect picture in full colour. Of course I didn't trust it; it was known to be intermittent and while I wanted to believe that I might have corrected something in the cleanup, that seemed like a long shot. So I simply kept on playing it at odd intervals while I waited for the replacement pot. I rang the owner and explained the situation. He wasn't at all con- cerned and in fact, I gained the impression that he was so cheesed off with the machine that he had mentally written it off. I felt I would have only had to suggest that he scrap it and he would have done so. Of course, I had no intention of making any such suggestion. The lack of the replacement pot meant the machine was now more or less pushed to one side. I tried it on odd occasions and it always worked but after a few weeks, pressure of other work prevailed and I abandoned even this ritual. I did keep needling the supplier about the pot though, but always without result. This went on for nearly six months - just as well the customer wasn't in hurry. Then one day a package of other spares arrived and there among them was the pot. "Aha!", I thought. "Now to get this one off the shelf". Normal Rate - I opened the machine again, fitted the new pot, tidied things up where the old one had been, and tried running a tape. No joy. The cassette carrier accepted the tape and put it on the deck but after that nothing happened. Fault number two. It wasn't a hard one to find. The idler wheel which drives the supply and takeup reels had packed it in. It was probably about due for replacement anyway and six months sitting unused on the shelf was the last straw. Anyway, it wouldn't drive the takeup reel and the protective circuit shut the system down. That didn't seem to be any pro- ly, if it runs at all. Then C813, a 1 O!,tF 35V electro, bypasses the same Vee rail and if it is open or low value, the result is weaving verticals. TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. $35 per hour. No charge for kits that can't be repaired. 3 month Warranty on repairs . Construction - fixed or hourly 1 2 Month Warranty on Manufactured Kits. Custom Designing, Manufacturing, Large or Small Quantitites. HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment. (02) 633 5897 Unit 4, 62 Great Western Highway, Parramatta, NSW 2150. Idle idler TETIA TV TIP National TC2202 (M8 chassis) Symptom: Set reluctant to turn on. Sometimes starts with a squeak, sometimes only squeaks. When it does get started it shows severe hum bars or horizontal wriggle . Cure: There are actually two different faults, closely associated with each other. R804, a 4. 7k0 SW resistor, feeds Vee to the horizontal oscillator. If this is dry jointed the oscillator runs erratical- FIX-A-KIT Kit Repairs - $15 per hour. Trading hours: 8am to 3pm Monday to Friday. D.DAUNER ELECTRONIC COMPONENTS WE STOCK A WIDE RANGE OF ELEC TRONIC PARTS • for Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WH ILE STOCKS LAST NEOSID HELIX FILTER for UHF now available COAXIAL RELAY 28VDC $32.00 TRANSMITTER VALVE 5786 $18.00 Come and see. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Caltex Service Station In Blrdwood Road) Phone 724 6982 TRADING HOURS: Monday to Friday 9.00 a.m. to 4.00 p.m. Saturday from 9.00 a.m. to 12.00 noon. N OVEMBER 1989 49 SERVICEMAN'S LOG -CTD blem. I had a spare idler on hand and it was a relatively simple job to fit it. Then I made another attempt to run a tape, only to realise that the machine was now completely dead - there wasn't even a clock function and when there is no clock it is something pretty fundamental. This was fault number three and it was a beauty. I went immediately to the mains fuse, F901, which is about as fundamental as you can get. But it was intact and that's when the fun started; a real chaseme-Charley effort. There is no way that I could describe the whole operation in the space available; nor could the reader follow it without a manual. Instead, I will content myself with a broad picture, with a few component ident codes tossed in for the benefit of my colleagues who do have a manual. IN ~HO'ln", The power supply (PWB-P) generates several voltages - including two 9V and two 13V supplies - which appear at plug PA. I checked all these voltages, hoping to find at least one that had failed. But no luck; they were all as prescribed which was a bit of a setback. One of these supplies - the 13V rail on pin PA4 - goes to board PWB-1 (IF Tuning Circuit) and appears at plug IEl. I followed this because the 13V supplies a package (RUNTKO157GE) on this board which is a power supply circuit in its own right. It delivers several voltages, some positive, . some negative and some AC. Again I drew a blank; all voltages were as marked. At this point pressure of more urgent jobs forced me to put the machine back of the shelf. But I did contact the owner rr w~~ F-\ N\E.sS, wrn-\ G~EA, '8LO~~ OF SOLDE.R":'; .. 50 SILICON CHIP and bring him up to date. He waved off my explanation: "No worries, mate - when you're ready". Patience indeed. It was several weeks before I was able to tackle the machine again. Still convinced that it was a voltage supply problem somewhere, I set about tracing and checking each supply rail in turn to its ultimate destination. Blind alleys I will spare the reader the agony of the blind alleys I followed; suffice it to say that there were several. But I eventually began tracing the 9V rail which commences at pin 9 of the power supply plug PA. This is shown as going to EB4. (Where the heck is EB4 ?) Well it turned out to be on board PWB-E, the mechanical control circuit, portrayed on a 3-section foldout sheet. The 9V rail comes into it on plug EB (pin 4) and rather interestingly, had now increased to 9.2V (good news for the perpetual motion inventors). According to the circuit, this rail goes straight from the plug to a device marked 'PR' but with no indication as to what this is. From there it runs all over the place, feeding a variety of components, and also exits from the board via at least five other plugs. So it is obviously a very vital rail. Having established this much on the circuit, I began checking this voltage on the board. Fortunately, I was able to pinpoint a couple of places where it should have been, only to find that it was missing. Well that was something. Now I was looking for the device 'PR' which, while shown hard against the plug on the circuit, was nowhere near it in real life. I finished up back-tracking along the copper pattern until I finally found it. It turned out to be a safety resistor, with voltage on one side and none on the other. So that was it - except that there was nothing on the device, the circuit, or in the parts list to indicate its value. Fortunately, most safety resistors fall into a fairly narrow category between 0.50 and 20 and with a nominal 0.5W rating. So, as a temporary measure, I fished out a similar device for another machine, fitted it, and we were back in business. Which was a considerable relief after all that effort. But why had the resistor failed? It had obviously been overloaded, rather than failed spontaneously, yet there was no sign of distress in the replacement. Naturally I was concerned that there was another intermittent somewhere but there wasn't much I could do about it, except give it a good workout. (In fact there was a good reason for the failure, which I will discuss later). So for the moment, I simply set it up in a corner of the bench, connected to a monitor, and ran it at every opportunity. The first day I ran a 3-hour pre-recorded tape through it. No problems. The second day I recorded a 3-hour tape, then played it back. No problems. The third day I played another pre-recorded tape. It ran without any problems for about two and a half hours. Then - a noise bar. Oh no! - fault number four. Sweaty brow As I wiped my brow in exasperation, I recognised the first clue; it was a stinking hot day and my workshop doesn't have air conditioning. I switched the machine off, let it stand for about half an hour, then ran it again. The fault had cleared, confirming my suspicion that it was a thermal problem. I rang the owner and asked him if he had ever experienced anything like this fault. He was quite emphatic that he hadn't and it Wil,S then that I realised the significance of his previous location; well south and somewhat elevated. The chances of him encountering the same thermal conditions as I had would be slim. In addition to the thermal clue, the nature of the display provided another clue. The noise bar was drifting slowly down the screen rather than remaining stationary as is more usually the case. This suggested that it was due to a loss of lock in either the drum motor or the capstan motor. The question was, which one? It was a 50-50 chance of course but I had a feeling in my bones that it was the drum motor. ,oo 11-1~ IVlACHIJ\le;:. W~'S N'OR6. OR t-6S1S ~SHE.'D A-S\t:>6-••• My first move was to connect the CRO to the appropriate test points - TP5 for the drum and TP3 for the capstan - and check the waveforms against those given in the manual for adjustment of the tab pots (R724 and R777) for correct operation. These waveforms came up virtually spot on - or at least as far as I could tell by comparing them with the idealised drawings in the manual, a point of some importance as it turned out. Of course, the machine had now cooled and so the test was not really conclusive. I had to leave things there for the day and the following day was a lot cooler, meaning that I had some trouble re-creating the fault. I considered applying artificial heat but rejected the idea. Instead, I wanted the fault to occur as a result of the machine's own internal heat distribution, at least for my initial investigations. Incidently, bulk heating can sometimes produce deceptive results due to innocent components being heated to a level far above that which they would experience under the worst real-life conditions. It's a point to watch. Anyway, the fault eventually appeared without any help and while waiting for this to happen, I had delved a little deeper into the circuit. The control signals for the drum motor come from IC708, on board PWB-A (Servo Still). The phase control signal comes out on pin 1, passes through transistor Q705, and is then applied to the drum motor. The frequency control signal comes out on pin 8, is processed by trani;;istors Q703 and Q702, and also goes to the drum motor. Since I had gleaned little from the CRO patterns at the te~t points, it occurred to me that it might be worthwhile checking these two circuits. I chose the collector of Q702, which goes directly to the drum motor. The only snag was that there are no waveforms in the manual covering these circuits so that I had no way of knowing whether what I was observing, under no-fault conditions, was within tolerance or not. The only obvious clue was that it changed when the fault occurred. Then it occurred to me that while I had the fault in my sights, it might be worthwhile trying to find the heat sensitive component with the NOVEMBER 1989 51 071 ◄ 0X01 ◄ 2a R71 t C701 '"'"' + i.z~ ..-Ei-c-+---N,-, R710 1,0v1 0702 '"" ·•ro 2SC~~ croo .o, 0703 2SA733 Fig.1: the drum control circuitry for the Sharp VC-483X VCR. Transistor Q702 appeared to be excessively heat sensitive. But was it? aid of some freezer spray. I started with Q705. No response. Q703 reacted similarly. But when I hit Q702 (2SC945) the reaction was immediate and dramatic; the fault vanished instantly. Further confirmation was provided by applying some heat to Q702 with the soldering iron, which quickly re-established the fault. I quickly fitted a replacement for Q702, then gave the machine another series of long runs. All seemed well at first but the second day was another hot one and after many hours operation, there was the fault again. And again, a smidgin of freezer was all that was needed to cure it. So what could I do? Run a plastic pipeline from inside the machine and give the owner a can of freezer, with instructions on how to use it? This and similar wild Heath Robinson ideas went through my mind, even while I was trying to figure out a genuine cure. I went back to the CRO check point [TP5) and had another look at the pattern. I still felt that it was as near as one could wish to the drawing in the manual but decided to try adjusting pot R724. With the machine still in fault condition, I turned the pot a few degrees one way with no result, then a few degrees the other way. And bingo, everything came good although it's 52 SILICON CHIP worth noting that the effect on the CRO pattern was virtually negligible. Well, that really did cure it. I ran the machine over many days, for hours at a time, and did everything I could to promote the fault. In all, it must have chalked up about 30 hours of use and it never flickered once. So what was the true nature of the fault? Was the first 2SC945 really faulty? Or was the original setting of R724 marginally off; perhaps just enough to cause trouble when the drift of some other component values became significant? Or had the previous serviceman had a fiddle with that as well as butchering the board? I'm inclined to suspect the latter, although there is little doubt in my mind that the first transistor was more heat sensitive than the second. Pertinent comments Finally, I feel that I should add a couple of pertinent comments. First, several checks with the owner have confirmed the cure; it hasn't missed a beat since and he is delighted. I have a permanent customer there. Second, why did the safety resistor fail? Shortly after I wrote the main part of this story I had another VC-483X in for service. It turned out to be a faulty idler wheel, similar to the one described above. That was simple enough and a replacement was quickly fitted. The only snag was that the machine was now completely dead; not even a clock readout. Of course the penny dropped and I went straight to the safety resistor. Sure enough, it had failed. Why? It was my own fault really. In both cases I had neglected to turn the machine off before working on it and, in removing the cassette carrier to get at the main deck, it is very easy to short one of the supply rails on the small board on the left hand side of the cassette carrier. And oops! - one safety resistor destroyed. That's one I learned the hard way. And what of the intermittent loss of colour which started all this? That was almost forgotten in the hassle of tracking down the other faults. And for a very good reason; it never appeared again and that includes my monitoring right up until writing this last part of these notes. From this I can only conclude that it was a faulty joint, either present from the start or created by the previous serviceman and which was corrected when I cleaned up the board. And that in itself is a rare enough event to be worth noting. ~ 1 PRICE PAGE if CRYSTAL EARPIECE Jft 3Crystal earpiece of high 1mpendance with 5mm plug . I Cat. AS-3305 1j Was $3.75 \,.. 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The Ferguson equivalent to this now sells for around $20. This is what you get for 1/4 of that 240V AC to 30-15-0 Ill) 150mA and 3V<at> 150mA MANUFACTURERS I We have a large quantity of these. Buy in bulk and save! $4.95 $4.50 $3.95 1-9 10-99 100+ This unit has a 75/300ohm input l!_nd two 75/300ohm outputs. Further splitters can then be used as this unit is designed to drive up to 8 • 10 TV points. It also has a channel 3. 4. SA and FM switchable trap (-25dB) in case of cross modulation of lBdB x 2. fC EXTRACTOR SAVE$1 WAS$2.95 NOW$1.95 Cal TH-1818 . Normally $109 NOW ONLY $69.95 TWEEZER BARGAIN WAS $1.95 NOW$1.50 SAVE 451'! Cal TH-1750 _ ~ ~ Dimensions (excluding pins): 41W x 340 x 32H Cal MA-2622 Non School/Non Government Accounts 0.4mm Single Core Manufacturers! Open an Hookup Wire SENSATION Another surplus buy. This is Telecom style hookup wire 0.4mm single core insulated. It comes on a 250m roll and there are also rolls with 2 cables on it of different colours total 500m. There are so many different colours available so if you order more than one roll we'll give you a different colour. Save an absolute fortune over normal prices. 250m roll Cat. WH-3027 $4.95 500m roll Cat. WH-3028 $8.95 ==== SPIRAL TV ANTENNA BARGAIN Jayi:ar will purchase your surplus stocks of components and equipment CALL GARY JOHNSTON OR BRUCE ROUTLEY (02) 747 2022 Two telescopic anten mounted in a sturdy cabinet which sits on your TV sel Telescopi rods are adjustable for maximum efficiency. 75 ohm plug and lead supplied. cat. LT-3110 Was $23.50 NOW ONLY $ 14 _95 ~~j~j~i.=~=i!-~~c1~~=.t~~~~\...SAVE $8. accountwithJayi:ar!Find outmorebycallingintoany Jayi:ar store or call (02) 747 2022 or send us a Fax (02) 744 0767 - or write! We will° send you an account application form by return. It's that simple! TV, popular spiral design. 300 ohm cable supoplied. WAS $9.95 NOW $6.95 SAVE $3 CalLT-3100 ..__----..:::::!!!E:::~~ RAD FAX Ref: Silicon Chip Cal KA-505 A MULTIMETER KIT TURN YOUR SURPLUS STOCK INTO CASH! RABBIT EARS $44 See Silicon Chip Nov '89 Ideal for students, who can now build something really useful. Multimeter specs: 20,000 ohms/volt. 23 ranges, continuity buzzer. Size 135 x 90 x 40 POWER CAR WINDOW WINDERS_ Convert your normal hand operated window winders to power windows. It's really simple to connect. remove the manual handle, choose the correct adaptor and connect to motor drive and mount the drive unit Supplied with cables and auxiliary switch. cat LR-8810 POWER WINDOWS FOR ONLY $219 POST a PACKING • ;1, ~, i ' - • I r . SYDNEY - CITY PARRAMATTA CONCORD HURSTVILLE 115 Parramatta Road Concord 2137 P. · ox 18 Conco rd 2137 Telephone (02) 747 2022 HOnlNE 02 747 1888 Telex 72293 FOR ORDERS ONLY FACSIMILE (02) 744 0.7 67 ~LFREE (008) 022 888 MAIL ORDER VIA YOUR 117 Yorlc St (02) 267 1614 Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Church St (Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 9 - 5.30 Thurn R.30 pm - Sat 9 • 4pm 115 Parramatla Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sat 8.30 - 12 121 Forest Rd (02) 570 7000 Mon·Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 12 U : 3.75 OVER $100 $8.00 $ : : :· ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 GORE HILL BURANDA QLD MELBOURNE-CITY SPRINGVALE VIC sz4_99 $25- $49.99 $50-$99_99 $lO. 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 479S• Mon-Fri !! • 5.30 Sat 9 - 4pm 144 Logan Rd (07) 393 0777 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 12 Shop 2. 45 A"Beckett St City (03) 663 2030 Mon-Fri 9 • 5.30 Fri 8.30- Sat9 -12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 • Sat 9 • 2 ANALOGUE MULTIMETER B FRE FLING CAMERA 1TH EVERY 2 BOXES OF VERBATIM DISKS MARKED WITH • until 15th Dec or ■ 10,000 ohms/volt sensitivity ■ Fuse and diode overload protection ■ Total of 18 ranges ■ 0.25, 2.5, 25,250, 1000V ■ 10.50.250, 1000V AC ■ 0.1.10,500mAOCcurrent oc UHFNHF/FM INDOOR ANTENNA until stocks last Description 1-9 Boxes 3.5" 1S/20 $39.95 CatXC-4720 3.5" 2S/20 $46.95 • CatXC-4721 3.5" 2S/HO $99.00 CatXC-4722 5.25" 1S/20 $22.00 CatXC-4725 5.25" 2s/2D $26.00 CatXC-4726 5.25" 2S/HO $41.00 • CatXC-4727 ■ 0.10M ohm in 3 ranges ■ Safetyoffpositionto ~ protect meter movement Size: 63 X 105 X30 Cat OM-1015 ■ WAS $26.50 SAVE $4 NOW $22.50 other surplus buy. Save $10 over normal ce. Rotating inner loop UHF/v'HF/FM xer. Slim line design. Can be wall moun ogle 75 ohm cable and plug connection. ~ 111 ,u~ \ NLY I . 24.95 - ~ I .. " ,P'( ) . Are you sick of paying high prices for mini PCB drill bits? We were. Now you don't have to pay outrageous prices anymore. Jaycars direct imports save you money. DRILL PACK Includes all those commen ones: ■ 1 x 3.5mm - for PC supports. relays ■ 2 x 1.2mm • for PC pins, hook-up wire ■ 3 x 1mm • for resistors, capacitors etc ■ 4 x 0.8mm - IC's etc. TOTAL 10 DRILLS FOR ONLY $12.95 Cat T0-2400 • WERE SELLING FOR $24 ..___, MINI DRILLS IN PKTS OF10 ■ ■ ■ 0.8mm x 10 (Cat TD-2420) 1mmx 10(Cat. TD-2421) 1.2mm x 10 (Cat. TD-2422) ANY PACK ONLY $9.95 LOWER PRICES ON SINGLE BUYS ■ 0 8mm Cat T0-2408 SAVE 7~ ■ 1mm Cat T0-2410 SAVE oot ■ 1.2mm , -~ Cat T0-2412 SAVE oot ANYONEONLY / ; : $1.50 : 6264 STATIC RAM BARGAIN ,,. SPEEO 150ns NORMALLY $22 NOW $10 CatZZ-8440 nsulation and braided shiel lly~ ml 100 MT FOR $45 B-2000 LEVEL CONTROL BARGAIN 80 watts handling. See the Jaycar 1989 catalogue for full •· *".::'" '-tf'' • details. Horizontal mount , ' Cat AC-1684 Vertical mount Cat. AC- 1685. Catalogue price $9.95 . NOW ONLY $2.95 . Will operate one 300 band full duplex and 1200/75 half duplex. Connect to AS 232 serial part of your PC. Was $169 SAVE $30 ONLY $139 Cat. KM-3040 catalogue Free with every purchase MIXED SEMICONDUCTOR PACK Guaranteed min. 100 units supplied but packs generally exceed this amount. IC's, Transistors. Oiodes. LEO's, A A M ~ t c . Cat. ZP-8990 ,' . :i 0NLY$10 ~ ERSONAL DATABANK/CALCULATOR UNDER $40 * GREENCAP PACK UNG CHANG 20 MHZ CRO Metallised Polyester. 60 top quality prime spec greencaps supplied. From 0.001 uF to 0.22uF. all ~ 100V. 60 IN PACK Cat. RG-5199 This personal databank will store your telephone numbers as well as being a pocket calculator. The databank has 2K memory which is 1,936 characters which will accommodate more than 100 names and telephone numbers. It measures only 88 x 57 x 4mm thick. about the same size as a credit card. It also has a special security code. so those private phone numbers can't be retrieved by anyone but you. WAS $7.95 SAVE $2 ONLY $5.95 LOWER PRICES ON HIGH INTENSITY LEDs 200MCD RED 79C Cat ZD-1790 Don't pay $1.75 - Wide bandwidth and high sensitivity- Internal graticule rectangular bright CAT - Built in component tester - Front panel trace rotater - TV video syno filter -Z axis (intensity modulation)- High sensitivity X-Y mode - Very low power consumption - Regulated power supply circuit Cat. OC-1900 Probes to suit Cat. OC-1902 Other features include: • Auto power off • Edit feature • 10 digit calculator • Includes battery We have seen these foras much as $79.95. But with our direct importing we can offer them at about 1/2 that price. 500MCD RED lOOOMCD RED Was.$4.95 $699 Cat. PP-4000 WAS $1.95 WAS $39.95 NOW $1.65 SAVE $5 ONLY $34.95 10+ $1.50 Cat. ZD-1792 $2.95 .. Cat. ZD-1793 .· ~:.:::: $49.50 ea :~i!~!PLUG ~ $1 .50 Was$2.50 JUMBO LCD CLOCK Huge, easy to read 20mm high digits. Unit measures 57 x 32 x 11mm and is supplied with a slip in bracket and double sided tape for easy mounting. Complete with light for night reading and battery. Ideal for cars. homes, boats. virtually anywhere. Cat. XC-0220 ONLY $7.95 DIGITAL MULTIMETER WITH EVERYTHING This really is the all singing, all dancing DMM. Jaycar's direct import saves you money again. Just look at the features! ■ Frequency counter ■ Temp measurement ■ Transistor tester ■ Capacitance tester ■ Diode tester ■ Continuity button ■ Data hold ■ 20 amp current ■ 28ranges Cat OM-1450 NORMALLY $169 SAVE $20 NOW $149 MICROSWITCH NOW $1.95 Cat. LA-5262 save $22.55 10+ $1.75 ONLY $19.95 LOW COST MAINS FILTER KIT Refer EA Oct 1009 Uses our 4 AMP mount mains filter. Kit also includes PCB varistors. fuse holder and fuse. Ideal kit to mount inside equipment Short form kit Cat. KA-1722 Another direct import which saves you money. WAS $18.95 NOW $13.95 SAVE $5 $18.95 SLIDER POT BARGAIN NOW ONLY $1.25 ea GIVEAWAY PRICEONLY $25 ea 10 of each value of 1/ 4W 5% from 1 ohm to 10 M ohm. 850 resistors in all. WAS $2.95 As used in the Equalizer Kits - 2801 and ETI 5000. Normally $3.95 Cat. RP-3912 We used to sell this unit years ago for $35. Today, it would cost about double that. Ideal for car alarms and home burglar alarms. It's very loud, the specs Sf'lf 112dB. But we think it's louder than that It has a nylon case and the noisemaker is a nylon 4' speaker. It's weatherproof and operates from 6-1 2 volts. Current drain 2 amps and the frequency is 1200-1500Hz oscillating. Supplied with mounting bracket. Size: 110 x 100mm. JAYCAR RESISTOR PACK SPOT 240V at 1.5 amp. Size 29 x 10mm x 11 (H)mm (body only). Supplied with actuator 60mm long which can be removed. Cat SM-1040 1.5V BATI6RY TESTERS The latest in battery testers. Consists of a very flexible piece of plastic with a conductive strip on the rear. Simply place over the battery terminals and the indicator will show if the battery is good, reasonable or bad. Re-useable. Every desk drawer. workshop. toolbox needs at least one. And at the price - who cares. 5 different designs available. • . I . . NiCad BATTERY ADAPTORS Why buy expensive C& D size NiCads when these adaptors allow you to use low cost AA NiCads instead. These adaptors look like a normal battery except that they are hollow and an AA NiCad can be inserted inside. These can then be used in place of the C or D NiCads. CSize Pkt of 4 was $4.95 Cat SB-2462 D Size Pkt of 4 was $4.95 Cat. SB-:...:2'464 -"" " - - ~ NOW $3.95 ~ M - 3 (Q1 ONLY 65~ EACH PENLIGHT Ni~ OR 4 FOR $2 Cat. SB-2350 SAVE EVEN MORE 500mA/Hr Cat. SB-2452 Was $3.50 ea NOW $3 EA or 4 for $11 JAYCAR SOLDERING IRON LOWEST PRICE EVER Ideal for the hobbyist and handyman. Ou lowest price 240 volt quality iron has a stainless steel barrel. 30 watt Cat TS-1450 PORTASOL PROFESSIONAL Fully comprehensive portable gas powered heat tool. It incorporates a soldering iron. hot knife. blow ton:h and hot blow for heatshrinking. Supplied in a case with 4 tips, sponge and stand. See catalogue for full detials. cat TS-1425 - Catalogue price $99.95 SAVE $20 ONLY $79.95 Replacementtipsavailable. ~~- WAS $16.95 SAVE $3 NOW $13.95 -- \ 12V CAR ANALOGUE CLOCK MOVEMENT Convert the broken/unreliable or inaccurate mechanical clock in your car to spage age precision. Made in West Germany t,,, VOO, this module measures roughly 45 x 38 x 40mm deep. Cat XC-0108 Was$9.95 NOW$6. SAVE This direct import product is outstanding value for money. It is moulded in a high impact dark grey plastic case with inbuilt tilting ball, includes spare fuse (built-in) and colour coded panel. A very comprehensive instruction manual is provided. CAPACITANCE RANGE 2nf • 20nf • 200nf • 2uF • 20uF • 200uF INDUCTANCE RANGE 2mH • 20mH • 200mH • 2H • 20H See catalogue for full specs Cat OM-1575 WAS $219 NOW $189 SAVE $30 8 SECTOR BURGLAR ALARM KIT 8 sectors and many features. See catalogue for full details. Cat. KA-1582 Was $169 SAVE$20 ONLY $149 M. -v-6 AUTO TUNE UP ADAPTOR KIT Make believe car burglar alarm. alarm stickers. Cat. KA-1630 Was $12,95 NOW $9.95 SAVE $3 f1ef. EA April 89 Turns your multimeter into a tacho/dwell meter. Suits 4. 6 or 8 cylinder petrol engines. Was $29.95 NOW $25.00 ot unlike our x 105mm) and is This is rare as Sound level is 1 volts, current d Ideal for car and burglar alarms. Normally worth about $38. A bargain at Cat. LA-5265 t- ,! l l l l ~JARLY .CHRIS1'MA$ SALE ~ ·, . ~~.: ' . ,~I -- •••• .... .··: ., ~ . ... . ......._ -~ ? SAVE ON DIGITAL MULTIMETERS ~~=oMvl■IFfo:~~.~~s PLUS • Diode Checker '1,_•a1■l■l■-■ lil■•••·•• ■ •ll--11' Continuity B_uzzer • Dne Hand Operation • 20 MHz Logic Probe Capacitance Tester $ • - Frequency Counter -DiodeTester - One hand Operation · - ONLY 49 95 SAVE $10 SCREAMER BARGAIN SAVE44% Don't miss this. Grey in colour, made in Italy, unbearable sound, 12 volt Ideal for burglar alarms inside cars and houses. Size 57l x 33H mm. Was $17.95 NOW ONLY $9.95 HORN MIDRANGE This metal horn speaker will add life to your sound system. Rated at 30 watts rms, in a system they will hanlde over 100 watts rms. Size 4" x 10.3" - Impedance: 8 ohms Rating: 30watts rms-Response:1.5kHz -12 kHz• Dimensions: 102 x 288 x 182 mm Cat CM-2082 WAS $44.50 NOW $34.50 SAVE $10 WAS $99.95 NOW $89.95 SAVE $10 MACHINED AIRCRAFT GRADE ALUMINIUM FLASHLIGHT What an excellent product! It measures 145mm long and runs off 2 x AA batteries. It is 70 times brighter than a normal torch and the beam is adjustable from spot to beam, and it's waterproof and shockproof. Durable anodised abrasion resistant finish, with a non slip knurled grip. It can also be used as a lantern. Unscrew the top and the bulb is exposed to give 360" light A spare bulb is supplied and mounts in the torch. We have seen these torches for $19. Spare bulbs available WAS $9.95 foronly$1.50(CatST-3002) SAVE$.,~.m 1N 4003 for 50 1N 4007 for 50 1 AMP '300v Cal ZR-1003 1 AMP 1000V Cal ZR-1009 $2.50 $5.00 NEW KIT FM WIRELESS INTERCOM FOR MOTOR BIKES Ref: Silicon Chip October 1989 Will provide communications between rider and pillion passenger, or between riders on seperate bikes. Communicate with more than one rider at a time, and also includes and FM stereo. ONLY $69.95 Cal KC-5056 PORTASOL SOLDERING IRON Cat SB-2459 SUNRISE BRAND D size Was $11.98 ea NOW $6.95 EA al SB-2460 rm generation gas sodering iron. No cards, batteries or bottles. Adjustable 10 - 60 watts. Up 60 mins use before filling, fills in seconds. Tips available. Used by electricians ewry.vhere. at TS-1420 ormally $39.95 SAVE $3 ONLY $36.95 I : '>t:::f.- •. BARGAIN BAGS CURRENTLY AVAILABLE Contains approximately 3kg of assorted electronic goodies· 'JUNK' if you like, but all brand nrm components etc. Ideal to fill up your junk box. We expect to have these available at most times. but availability does depend on how much junk we find. Unfortunately, due to the massive weight, p & p is normal rates plus $5. Cat. XB-9000 ■ $14 95 BUY 10 ASSORTED $1 BARGAINS FROM THIS PAGE AND WE'LL GIVE YOU ONE EXTRA OF YOUR CHOICE - FREE GREEN RECTANGULAR LEDs Green Yellow Orange NORMALLY 40~ each NOW 10 FOR $1 ARLEC TRANSFORMER BARGAINS ARLEC No. 61365 A chassis type tranny that gives 240V to 24V CT<at> 500mA and 9V <at>5A/ This tranny could give you a ±12V 500mA and +5V<at> 5A DC power supply (with rectifiers, regs, and electros of course). Caal. MA-2600 Normally $25 NORMALLY 40~ each BC556 TRANSISTOR PNP T0-92 65V 1OOmA Cat. ZT-2162 NORMALLY 65~ each NOW 10 FOR $1 SPOT· black toggle Cat. ST-0594 A bargain at $9.95 NORMALLY $2.95 10+ $8.95 P& P$4 extra NOW $1 EACH ARLEC No. 61435 A grain oriented steel chassis type unit giving 240V to 'iN AC<at> 3A, 16V AC<at> 2A, 16V AC <at> 1A The secondaries can be wired to give 16V<at> 3A or 24V<at> 3A This is ideal for burglar alarm power . supply as burglar alarms use 16V. You could also make a 13.BV regulated power supply from this. Normally $30 - ~5 ONLY $9,95 10+ $8.95 Cat. MA-2602 P & P$4 extra IQ. \ I --eo:,i( ' ~, Cat SL-2654 NORMALLy SWITCH SPDT CENTRE OFF RIGHT ANGLE MINI TOGGLE so~ NOW4 FOR $1 On special last month for $1.95 Cat. ST-0563 NOW $1 each 100uF 16V TAG TANTALUM NORMALLY $2.50 ~ OW $1 EACH - Cat. RQ-5291 NORMALLY $1.95 · ~ •- ·- I 20-90pF TRIMMER CAP Hi-quality Japanese 5mm spacing Cat. RV-5710 ~ , _ - Cat. RG-5256 NORMALLY $2.25 Cat. RG-5247 NOW $1 EACH NOW 2 FOR $1 , PS-820 PLUG PACK A standard style plug pack of 10.5V DC <at> 300mA. We don't know what to use them for, but at $3.95 each, who cares. (Output lead same as 61439.) i~.~:-~~ e:)l., ~·· . •·· ARLEC No. 61071 · A large chasis grain oriented steel transformer that gives a massive 20V centre tap at 15 AMPS! This would enable you to, say build a regulated DC supply of :!J3V<at> around 10 AMPS. A tranny of this size would normally cost over $60 ONLY $15 Cat. MA-2604 P & Pextra $6 each LIMITED QTYS Cat. RG-5222 0.047uF 630V GREEN-CAP NORMALLY $1.60 NORMALLY 95~ NOW 3 FOR $1 Cat. RG-5205 _ NOW 4 FOR $1 ====Cat. RG-5202 PLUG ADAPTOR NORMALLY 70~ 6.5mm plug to3.5mmsocket Cat. PA-3504 . NOW 5 FOR $1 ~ , ~~ NORMALLY $1.95 PLUG ADAPTOR NOW $1 EACH PLUG ADAPTOR RCA plug to 6.5mm socket Cat. PA-3510 WAS $1.95 RCA plug to 3.5mm socket Cat. PA-3508 c~;:;::;;;;;:;:;::;;;;;:;:;::;;;;;:~g c;;;;::;='"' a-~ ·~~~~ NORMALLY $1.95 NOW $1 EACH NOW $1 EACH ARLEC PS-561 A "Maxi box· plug pack adaptor. 240V to 7.5 DC<at> 600 mA (Output flying lead same as 61439.) Cat. MA-2606 ONLY $6.95 * ~ , OW 5 FOR $1 NORMALLY $2 ARLEC LIMITED QTYS r. ;. · NOWS FOR $1 ONLY $9.95-..:c~ 10+ $8.95 Cat. MA-2608 l~l _ __ NOR MALLy so~ An in-line "Maxi box· type power supply. 240V to 6V AC <at>3 AMP. (Output lead fitted with 5.5 DD 22.110 DC plug.) Normally worth $40 C&K ~ Cat.RZ-6678 - ARLEC No. 61439 10+ $3.50 Cat. ZD-1781 Cat. ZD-1782 Cat. ZD-1783 1DwaCy CONNECTORS RIGHT ANGLE 16 26way 34 way Cat. PP-0951 Cat. PP-0954 Cat. PP-0955 ONLY $1 EACH :,. . 1 ., ,\ • J • ·- ,;w_;.;_,,.,<·o/:,,;_._C/.}). ~ 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. ,-----➔------------....-----------+----A .047 100k 4.7k TL072 o--:t RIGHT ~ 1 0 + INPUT 7 5.6k .,. .0022 TREBLE VR2a 100k + .0022 100k .,.. 33+ - 0.1 ME 3a k + 'I' 2.2 - 100pf! 33k 33k., 100pf! .,. .,.. . - - - - - - - _ ; : . . __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ A .047 r 10 LEFT ~-::a+ INPUT .0022 TREBLE VR2b 100k .0022 100k 33k-:- lDOpf+ .,. .,. +12VO-----r~--+-----,,..._-..,r~-+ 4.1V TO PERSONAL CASSETTE PLAYER 22{1 5W Walkman car stereo amplifier The sound quality from most Walkman-type cassette players is quite good and their low operating voltages make them ideal for in-car use. This circuit is basically a small stereo booster amplifier so that you can use the cassette player to drive a pair of loudspeakers in the car or in the den. The left and right channel outputs from the cassette player are fed to tone control stages ICla & IClb (TL072). These have the tone controls connected in their negative feedback networks, with VR1 & VR2 providing bass and treble control respectively. The outputs ap- pear at pins 1 & 7 of IC1 and are AC-coupled to the balance control VR2 and to volume control VR3. IC2, IC3 , IC4 & IC5 form the power output stages and are simply LM380 audio amplifier ICs wired in bridge configuration. For the right channel, the signal is fed to IC2's inverting input and to IC3's noninverting input so that the loudspeaker is driven in antiphase. This effectively doubles the peak-to-peak voltage across the load, thus quadrupling the power output. In practice, the power output is about 6W into an 80 loudspeaker. The left channel (IC4 & IC5) works in exactly the same way as the right channel. 40 loudspeakers should not be us- Fig.1: the circuit uses two tone control stages (ICla & IClb) to drive bridged power amplifier ICs (IC2-IC5). The bridge arrangement effectively doubles the peak-to-peak voltage across the load, thus quadrupling the power output. ed since they will represent an excessive load on the LM380s. Power for the circuit is derived from the car battery. Ql and Q2 function as capacitance multipliers to provide filtering and bypassing of the supply rail. Zener diode ZD1 sets the voltage on the base of Q2. Its value should be adjusted to suit the particular cassette player. Note that you should drive the circuit with the cassette player volume set to about half way. This will ensure a good signal to noise ratio. Darren Yates, French's Forest, NSW. ($30) NOVEMBER 1989 61 LED3 -4 YELLOW LED1-2 GREEN +9V D4 1N914 .,. D17 1N914 +9V +12V 220 + m•r . .I 100 ,son .,. + 100k 100k 470!l .,. Traffic light system for model railways Realism counts for everything as far as most model railway enthusiasts are concerned. And in trying to reach that goal, a town layout isn't complete without traffic lights. This simple circuit drives green, red and yellow LEDs to accurately simulate traffic lights at an intersection. NAND gates IC la & ICl b form a simple square wave oscillator and this clocks IC2, a 4017 decade counter. Its o to 9 outputs go high in turn on each successive positive edge of the clock signal. IC2's outputs drive several sets of OR gates made up of diodes Dl-D20. These OR gates drive transistors Ql-Q6 which in turn control the traffic light LEDs. Note that each transistor drives two LEDs of the same col62 SILICON CHIP .,. our, one for each opposing light set. Thus, when pins 3, 2 or 4 are high, Ql will turn on and so LEDs 1 & 2 (green) for one set of lights will also be on. Q4 will also be on during this time and this turns on the two red LEDs (LEDs 7 & 8) for the other set of lights. The remaining diode OR gates ensure that the remaining LEDs for each set of lights turn on in the correct sequence and stay on for the correct amount of time as the 4017 counts up. As with normal traffic lights, there is a brief period when both sets of lights are red (ie, pins 10 or 11 of IC2 high). Each complete cycle takes about 25 seconds and is then repeated. The timing period can be altered by changing the timing components in the oscillator. Darren Yates, French's Forest. ($40) .,. 4-channel mixer with effects send This simple mixer was designed for use in a home recording studio. It features four inputs, tone controls and an "effects send" junction for mixing in reverberation, delay, chorus etc with the original signal. Each input stage is based on a transistor which includes a Baxandall tone control stage in its feedback loop. The output signals from these stages appear at the transistor collectors and are fed to an auxiliary bus via 0.47 µF capacitors a;11d 47k0 resistors. From there, the signal passes to summing amplifier IC2c which provides an output for an effects unit. The output from each tone control stage is also fed into an op amp panning circuit (ICl). In the case of channel 1, VR4 allows the signal to be panned either left or right into inverting op amp stages ICla and ...-----11-------'21,\10Mn,------.------.------1p----+1sv 330k 68k 0.22 27k BASS VR2 500k 100k 27k lNH,,LIT LEVEL VR1 10k cr -:" 0.47 LEFT OUTPUT T" ms----t--------➔-~,-----.--➔---. 100k RIGHT OUTPUT TREBLE VR3 68k 500k 330k RIGHT BUS LEFT BUS 1....._ _ __.;;_ _ _ _ _ _ _ _ _ _ _ -15V ALL ICS LM324 47k 47k INPUT 1 I ~EFFECTS SEND 12k CH 2 .,. .,. INPUT Cf AUX BUS CH 3 .,. INPUT 1 CH 4 47k ICl b. This circuitry is duplicated in the other three channels. The outputs from the panning stages are fed via 47k0 resistors to output stages IC2a & IC2b where they are mixed with the left and right signal returns from the effects unit. As with IC2c, IC2a & IC2b also function as summing amplifiers. Their outputs appear at pins 8 & 14 and are fed to the tape recorder via lµF capacitors and the 10k0 Fade control pot [VR5). The unit must be built into a metal enclosure and should be powered from well-regulated ± 9-15V supply rails. Steve Massey, Collaroy, NSW. ($40) Fig.4 (right): the mixer can be hooked ► up to a stereo effects unit for mixing in reverb, chorus, delay and other special effects. INPUTS LEFT LEFT OUTPUT RIGHT RIGHT OUTPUT MIXER SEND LEFT RIGHT RETURN STEREO EFFECTS UNIT NOVEMBER1989 63 FM radio intercom for motorbikes Last month, we described the circuit and gave the constructional details for our new FM radio intercom. This month, we conclude with the test and alignment details. By JOHN CLARKE & GREG SWAIN Before connecting power to the intercom, you should first go back over your work and check carefully for wiring errors. Are all parts installed the right way around? Are the parts values correct? Are there any missed solder joints or solder bridges? Some careful checking at this stage may save a lot of frustration later on. Once you are satisfied that there are no errors, temporarily hook up the loudspeaker and microphones, 64 SILICON CHIP then connect a suitable power supply. Either batteries (3 x 1.5V) or a variable power supply set to 4.5V can be used to power the unit. Make sure that you don't set the supply above 5V otherwise you could damage the tr~nsmitter chip (IC2). Apply power and switch the intercom to the 'FM' mode. Now, using your multimeter, check that the + 4.5V supply is present on pin 4 of IC1, pin 5 of IC3, and pin 9 of IC4. If these voltages are all correct, switch to the 'intercom' mode and check that the transmit LED lights when you speak into one of the microphones (note: VR1 & VR2 should initially by set to midposition). Now check the voltage on pin 15 of IC2 - it should be about 2.9V (not 2.5V as shown on last month's circuit diagram). Finally, check the voltages across the supply pins of IC3 (pins 5 & 16) and IC4 (pins 9 & 11) in the 'intercom' mode. You should get a reading of about 0.7V when the transmit LED is on and + 4.5V when the transmit LED is off. If you don't get the correct readings switch off and check for wiring errors. If you have problems, there is a brief troubleshooting procedure at the end of the article, so you should also refer to that. L1 The alignment procedure involves making adjustments to the parts indicated here. Be sure to use an insulated alignment tool when adjusting the coils (L1-L3). A metal screwdriver will affect the coil inductance and could crack the ferrite slugs. Alignment If everything is OK, you are now ready for the alignment procedure. This can be done without the use of any test equipment but does require the use of a commercial FM receiver (preferably one with a digital readout). You will also need a plastic alignment tool to adjust the slugs in the coil formers (Ll-13). Do not use a screwdriver here, otherwise you could crack the fer rite slugs. A metal screwdriver will also make adjustments extremely difficult since its presence affects the coil inductance. Make up a suitable alignment tool if you don't already have one. A plastic knitting needle can be easily modified to fit the slot in the ferrite slugs. The slugs should be screwed into 11, 12 and 13 together with a short piece of dental floss (available from supermarkets and chemist shops) or very fine elastic. This will ensure that the slugs stay in position when adjusted. Don't use wax to hold the slugs in position - it won't work and will make a mess. Now for the alignment adjustments. The procedure is set out below on a step-by-step basis to make it easy to follow. • Switch on your reference FM receiver and tune it to a station near the 88MHz end of the dial. Rotate the dial on the intercom so that the dial indicates the same frequency as the tuned station. Switch the intercom to the 'FM' mode and set the volume control to about 25% of full rotation. • Adjust 13 until the same station is heard on the intercom. Now tune the reference FM receiver to a station near the 108MHz end of the band and set the tuning dial on the intercom to the same indicated frequency. Adjust the trimmer capacitor on the top of the tuning gang (VCl) to receive the same station as the reference FM receiver. Note that the trimmer requiring adjustment is the one closest to the front panel. The other trimmer is not used. • Retune the reference FM receiver to the station at the 88MHz. end of the band and set the tuning dial of the intercom to show the station frequency. Readjust 13 until the station is heard. This done, retune the reference FM receiver to the station at the 108MHz end of the band and set the intercom tuning dial to show the frequency of this station. Readjust the tuning gang trimmer so that the station is heard. The above procedure adjusts the tuned circuit in the intercom's receiver so that it covers the commercial FM band. If you like, you can repeat the procedure once more to ensure that everything is correct. • Tune the reference FM receiver to 88.0MHz and check that trimpots VRl & VR2 are at mid-position. Select the 'intercom' mode and activate the transmitter by speaking NOVEMBER 1989 65 The metal shield (at end of pen) must be installed before the alignment procedure. Note how the O.lµF capacitor adjacent to L2 is installed. into one of the microphones (the transmit LED should come on). Adjust slugs 11 and 12 until your voice is heard on the reference receiver. Note that 12 sets the transmit frequency while 11 forms part of a bandpass filter. The two slugs should be adjusted together so that they are at about the same depth in the slug core. Our prototypes tuned to 88.0MHz when the slugs were about 113rd of the way into the core from the top. When the frequency is tuned, adjust L1 for best signal quality. • Adjust VRl and VR2 so that the signal does not sound overloaded or cut out altogether. Rotating the wipers clockwise (as seen from the front panel) will reduce the signal level. Both trimpots should be set to the same position. • That completes the adjustments for the first intercom. Now you need to adjust the second intercom in exactly the same manner. Testing The two intercoms can now be tested for range and clarity. Make The coiled cord is clamped to the front panel using a cord grip grommet. Don't forget the earth connection to the body of the pot. 66 SILICON CHIP sure that the antenna leads are supported with the same orientation. We recommend that the antenna lead be clipped to your collar. Some slight retuning of the transmitters may be required for best results. This is simply a matter of tweaking 12 in each unit to give maximum range (about 50 metres). Don't touch 13 - it's best to adjust the transmitter frequency only. Note also that the components located around tuning coils 11, 12 and 13 will alter the tuning if moved. These parts include the capacitors and the tinplate shield. If you do move any of these components, you may have to go back over the alignment procedure again. As pointed out last month, the O. lµF capacitor adjacent to 12 must be laid flat against the PCB. If you don't to this, it will affect the tuning of the coil, particularly with changes in temperature. Helmet wiring The loudspeakers and microphones are installed in the helmet as shown in Fig.1. Note that the loudspeakers must be small enough to fit behind the helmet lining. Very small headphone loudspeakers can be used if there is little space within the helmet. The electret microphones must be secured in the positions indicated; ie, one directly in front of the rider's mouth and the other mounted to one side. Make sure that the addition of these components will not cause injury if there is an accident. The leads running from the microphones and loudspeakers connect to the 6.5mm stereo and mono line sockets. These leads are run beneath the helmet lining and secured to the base of the helmet. Note that if glue is used to secure the wires and microphones, be sure to use a type which will not affect the helmet. Some glues, such as contact adhesive, give off fumes which may damage the polystyrene helmet liner. Epoxy resin glues should be safe, provided there is adequate ventilation during the curing process. Once the intercom is completed, it can be tested on the motorcycle. The antenna lead should be clipped to the collar of your jacket so that it extends to maximum length. Of course, common sense dictates that you don't attempt to make any adjustments to the intercom while the bike is in motion. Troubleshooting If it doesn't work, don't dive in and replace all the ICs and transistors. That seldom fixes anything and only wastes money. Most faults in kits are due to faulty soldering, wiring errors and incorrect parts. The first step in troubleshooting is to check all these possibilities very carefully. In particular, check the wiring to switch S1. The diagrams show the wiring for the Dick Smith Electronics switch but if you use a switch from another supplier, then the connections may be different. If necessary, use your multimeter to determine the switch terminals. If all the wiring checks out, try to determine which part of the circuit is not working. For example, if the unit won't receive FM stations, then the fault could lie in either IC3 (the receiver chip) or IC4 (the audio amplifier). You can then check IC4 by applying a low-level audio signal from an external source across the volume control (VR3). If the receiver circuitry works but the unit won't transmit, the fault could lie in the microphone preamp circuit (ICla, IClb), the VOX circuit (IClc, ICld & Q1-Q3), or the transmitter (IC2). You can easily check whether or not the microphone preamp and VOX circuit is working by selecting the 'intercom' mode and speaking into the microphone. If the transmit LED lights, the VOX circuit is OK. If it doesn't, there is a fault in the VOX circuit or IC2 is faulty (or the LED is wired back to front). To determine where the trouble lies, short the collector and emitter leads of Ql. If the LED now lights, the fault is in the VOX circuit; if not, the fault lies with IC2. If the VOX circuit isn't working, use your DMM to monitor the voltage on pin 8 of IClc. This pin should normally be close to 0V but should give a reading of over 1V when you speak into the micro- WIRING TO - - - MICROPHONES 6.5mm STEREO LINE SOCKET ANTENNA □-- LOUDSPEAKERS -o MOTORCYCLE INTERCOM -HELMET Fig.1: this diagram shows how the electret microphones and loudspeakers are installed in the helmet. Note that one of the microphones goes directly in front of the rider's mouth while the other is placed to one side. The speakers go behind the helmet lining. phone. If nothing happens, then the microphone preamplifier circuit is at fault. Note: the output of IClc is actually a square wave which is averaged by the DMM to give a reading. If everything is OK here, check the voltages on pins 12 & 13 ofICld. Pin 13 should be at about 0.8V while pin 12 should jump from 0V to over 1V when you speak into the microphone. At the same time, pin 14 of ICld should go from 0V to about 3.2V. Assuming ICld is working, transistors Qt, Q2 & Q3 can be checked by measuring their collector voltages. Normally (ie, VOX not activated & pin 14 of ICld low), Qt & Q2 should be off and Q3 should be on. Qt 's collector should be at + 2.4V, Q2's collector at + 0.7V and Q3's collector close to 0V. If this checks out, connect a jumper lead between the cathode (K) of D2 and the + 4.5V supply rail. Qt & Q2 should both now turn on which means that their collectors should be close to 0V. At the same time, Q3 should turn off and its collector should go to about 4.1 V. Another way of checking the transistors is to measure their baseemitter voltages. When the jumper lead is connected, Qt and Q2 should both have a base-emitter voltage of about 0.7V. When the jumper lead is removed, Q3 should have a base-emitter voltage of 0. 7V (ie, the transistor is turned on). Check the transistors carefully if you fail at get the correct voltage readings at any stage. Their correct operation is crucial for supplying power to the rest of the circuit when in the 'intercom' mode. ~ NOVEMBER 1989 67 COMPUTER BITS By JENNIFER BONNITCHA Floppy disc drives: formats & options Despite their limited storage capacity, floppy discs are still vital to your PC. You need them to transfer files to and from your computer and to back up data on your hard disc. A computer system can be divided into several main parts. First, the CPU (central processing unit) controls all parts of the computer system while carrying out the instructions of the currently active program. The main memory (Random Access Memory or RAM) ex- ecutes or runs the program by reading each instruction in sequence and performing the requested action. Any data used in the calculations and the results are stored in memory. The remainder of the computer system is concerned with the way in - - - - - - - - - (5¼ I n c h ) - - - - - - - - - - - Sealed protective jacket Liner Fig.1: a floppy disc is made of flexible mylar which is coated on both sides with a thin layer of metallic oxide particles and enclosed in a protective jacket. In operation, the read/write heads move across the disc surface at the head aperture. 68 SILICON CHIP which you communicate with the CPU and RAM. Data and programs are entered via some input device such as a keyboard or disc drive, while the results are displayed on an output device such as a monitor or printer. There are hundreds of operations to keep track of during the operation of something like a disc drive, so the I/O (Input/Output) interfaces take care of the details of connecting an input or output device to the CPU. Allowing the I/O interface to worry about these details translates to smaller programs (at least in theory), since the program need not concern itself with the exact whys and wherefores. Inside most system units there js sufficient space to mount two 5 ¼-inch floppy disc drives. Aithough a floppy disc drive can take milliseconds to jump from data area to data area on the disc, the CPU can carry out thousands of calculations in that time. Thus a program which needs to go back and forth to the disc during calculations will run at a very sluggish pace indeed. A hard disc drive rotates constantly at 3600rpm and it takes about three milliseconds for the read/write head to move from track to track. By contrast, a floppy disc rotates at 300rpm only during read/write operations and it takes about eight milliseconds to move. For most users, a hard disc is the usual place to store all those precious bytes but not everyone has the necessary dollars for this luxury. So from here on in, let's concentrate on the increasingly maligned floppy disc. connector on the signal ea ble from the floppy disc controller card. If you want the new drive to be drive 0, swap the connector with the one currently on the other disc drive. Switch 1 O 2 3 4 5 6 7 8 ; □ LJ □□□□□□ Position 1-7-8 2 3-4 5-6 System switches Function Number of 5'/4inch diskette drives installed Reserved for co-processor Amount of RAM on system board Type of monitor you are using Switch 2 Position 1-2-3-4 5-6-7-8 Function Amount of memory options installed Always in the off position Fig.2,3: these diagrams show how DIP switch 1 is used to select the number of floppy disc drives in an IBM PC. Check the manual for your particular machine, as there can be differences between models. Number of 5-1/4" diskette drives installed Switch I ODrives I Drive 2-Drives The floppy disc A floppy disc (Fig .1) is inade of flexible Mylar coated on both sides with a thin layer of metallic oxide particles and enclosed in a protective jacket. The centre hole ,is generally reinforced around its edge since it is here that the disc is clamped by the drive mechanism. The disc's recording surface can store information as binaryencoded data (ls and 0s), the value at each point on the disc depending on the magnetic polarity. In operation, the read/write heads move across the disc surface, either reading or writing data as required. Data is stored on the disc by delivering a series of magnetic pulses from the heads as they move across the disc surface. Conversely, data is read from the disc by deter- Switch 2 1 □□0000 □□ 11000000001 ,~□DODD □□ I l □□ODODDDI l □ DDOOD □□ l l □ DDODODOI mining the polarity of the magnetic field at various points on the disc. The disc drive or read/write head differs considerably for floppy disc drives, high capacity drives and fixed discs. Installation It's usually quite easy to add an extra floppy disc drive to your PC if you currently only have one drive. To do this, first remove the system top cover and faceplate, then slide the drive through the front panel. Depending on the make of your computer, the drive will either be secured solely by screws or you may need to attach plastic rails to the sides of the drive. Slide the drive into the system unit until it is flush with the front panel, then install the mounting screws. Now attach the power supply connector and plug in the spare The lower left section of the XT motherboard contains sockets for the memory chips while an 8-way DIP (dual in-line package) switch is located below and to the right of the expansion slots (the PC has two 8-way DIP switches). These switches define which options - such as the number of disc drives, the amount of memory or the presence of a maths co-processor - are installed or connected to the PC. Depending on the make and model of your computer, you may need to change these DIP switch settings. Figs.2 & 3 show the switch settings for the number of disc drives in the IBM PC while Figs.4 & 5 are for the IBM XT. Remember, however, that these figures are a ppropriate to the "genuine article" (ie, IBM machines) only. If you have a PC-compatible, you are strongly advised to check the manual to determine the correct switch positions. It is a good idea to write down the current DIP switch settings before you make any changes. That way, if you encounter difficulties with the new installation, you can at least go back to the old configuration. Formatting When you have moved the DIP switches to their appropriate positions, replace the system unit cover. Now the fun of testing your installation prowess begins! All discs must be formatted before use. The process of formatting prepares the disc for use by DOS by defining a structure of concentric tracks and a filing system to keep track of just what is stored on the disc. The formatting process also analyses any defective areas on the disc and prepares the disc for file storage by establishing a directory and the File Allocation Table (FAT). When Format divides the disc into tracks, each track is then further divided into sectors. The disc capacity is measured in kilobytes (Kb), with 1Kb represenNOVEMBER 1989 69 Switch I 2 3 5 4 I Drive 6 7 8 of~ (j □ □ □ □ □ □ Position Function For normal operation is off Co-processor Amount of RAM on system board lype of monitor you are using Number or 5¼-inch diskette drives installed 2 3-4 5-6 7-8 ting 1024 bytes. Generally one byte is equivalent to one character so it is a simple matter to calculate the amount of space required to store one page of single-spaced A4 typing. In practice, 80 columns of type over 25 lines requires approximately 2Kb of storage space. Early IBM disc drives were single-sided only with a storage capacity of 160Kb. The data was recorded on 40 concentric tracks, with each track containing eight sectors and each sector capable of storing 512 bytes of information. Thus, 40 tracks x 8 sectors/track x 512 bytes/sector gave a formatted capacity of 163,840 bytes. DOS 1.1 extended disc I/O support to the double-sided disc with a formatted capacity of 327,680 bytes. Introduction of the XT also saw the introduction of DOS 2.0. This enabled the formatting of either single sided or double sided discs using either 8 or 9 sectors per track. Thus, a single sided disc could now store 184,320 bytes and a double sided disc could store 368,640 bytes of data (assuming nine sectors per track). 2 DrNeS I IOOOOOOU□ I ID DODOO □□ Fig.4,5: the XT machine only has a single configuration switch. Positions 7 & 8 select the number of floppy disc drives installed as shown above. Further advances, both to the operating system and to drive technology, now mean that the 5¼-inch disc on the AT is capable of storing 1,228,800 bytes (1.2 Megabytes) of information - a far cry from the original 160Kb! DOS 3.0 formats the high capacity disc to 80 tracks with 15 sectors per track. Subsequent introduction of the 3 ½-inch micro-disc has pushed disc storage limits further by storing the same amount of information in an even smaller area. The difference between the storage capacity of a hard disc and a floppy disc is a function of the number of tracks and sectors. The 360Kb floppy disc has 9 sectors per track with 40 tracks per side; the XT's 10Mb hard disc consists of two platters and each of the four surfaces formats to 306 tracks. Finally, the AT's 20Mb disc has four surfaces, each of which format to 615 tracks. Both the XT and AT hard discs have 17 sectors per track compared with the 15 sectors per track for the high capacity floppy disc (see Table 1). The AT-style computer generally Table 1: Floppy Disc Formats Sides 1 1 2 2 2 Tracks Sectors/Track 40 8 40 9 40 8 40 9 15 80 Storage Capacity (Bytes) 163,840 184,320 327,680 368,640 1,228,800 Table 1: floppy disc capacity has increased steadily with advances in system and drive technology. The 5¼-inch floppy disc for the AT machine is now capable of storing 1.2Mb of information. 70 SILICON CHIP has a high capacity disc drive which is capable of reading and writing to the low capacity 360Kb disc. However the 360Kb drive cannot format, read from or write to the high capacity disc. A good rule of thumb when formatting a 360Kb disc in a high capacity drive is to use a fresh disc with the "/4" option. Format switches The Format command has several switches available for use. Note that individual manufacturers may further customise the options available with the Format command. Fig.6 shows the result of formatting a typical disc. The Format command is as follows: FORMAT Drive:/S/1/8/V/B/4 Note that everything after "Drive:" is optional, depending on how you wish to format the disc. Here's what the various options mean: Drive: this specifies the drive containing the disc you want to format. IS supported by all DOS versions, this switch tells DOS to format the disc and include the operating system files. These system files are IQ.SYS (IBMIO.SYS); MSDOS.SYS (IBMDOS.SYS); & COMMAND.COM. The *.SYS files are hidden and are "seen" only when the CHKDSK command is used. when this switch is includ/1 ed, DOS 1.1 and above formats the floppy disc as single sided. If it is not included in the command, DOS formats discs as double sided, double density. DOS 2.0 and above uses /8 this switch to format a floppy disc with 8 sectors per track instead of the usual 9. It may not be used when formatting a hard disc. DOS 2 .0 and a hove IV enables the writing of a magnetic label to the disc. DOS prompts the user to Sector 4 Sector 5 Sector 3 Sector 7 Sector 2 Track 39 Head aperture provides access to each sector on a track as the disk spins. Fig.6: this 40-track disc has been formatted into eight sectors for a capacity of 327,680 bytes. Each sector appears in sequence at the head aperture as the disc spins. /B enter a volume label of up to 11 characters. Note that the label serves no practical purpose; it simply identifies the disc. with this switch, DOS 2.0 and above formats a disc with 8 sectors per track and creates two dummy files in the root directory to leave space for later addition of the operating system files. It is also used to create a disc onto'which any version of DOS (1.0, 1.1 or 2.0) can be placed. It may NOT be used in formatting the hard disc or with the /S or /V switches. /4 this option, introduced in DOS 3.0, is for. formatting 360Kb discs in a high capacity drive. Caution: 360Kb discs formatted in a high capacity drive may not be read or written to reliably in the 360Kb drive. Generally, however, there are few problems. If you own an AT, you can always consider installing an additional 360Kb drive in your system unit. Dummy data When a disc is formatted, any data stored on the disc is destroyed. The general procedure is that DOS Table 2: Format Options Disk Capacity 320/360Kb 1.2Mb Hard Disk Parameters /S /1 /8 N /B /4 /SN /SN Table 2: the format options available for various disc capacities. Each option is explained in the text. puts dummy data on the disc and then reads it back one track at a time. Any defective tracks are flagged as bad tracks in the File Allocation Table (FAT) to prevent them from being used for subsequent data storage. When writing and reading is finished, the Format command writes a new DOS boot sector then initialises the first FAT by filling it with zeros. The FAT begins with a Media Descriptor Byte (MDB) which tells DOS and programs like CHKDSK what type of disc it is, together with the Bad Track information. Generally, DOS maintains two copies of the FAT so that if one is physically damaged, it can use the other. Note that DOS, in the event of conflict, can't decide which of the two FATs is correct. The blank Root Directory follows the last copy of the FAT since this is the main directory from which all others branch and yes, a floppy disc may have a directory structure. The Root Directory on the floppy disc typically holds from 64 to 224 entries, depending on the disc type. From the Root Directory to the end of the disc, data storage takes place. The CHKDSK command The CHKDSK command is used to determine the total number of bytes available on the disc. It must be issued from a drive or directory where system files are present. For example, if the system files are the C drive, the command is: C:)CHKDSK A: The system then displays the following information: 362496 bytes total disc space 362496 bytes available on disc xxxxxx bytes total memory xxxxxx bytes free Note that if a disc is not formatted, the directory and file allocation table are not present. Thus, if you enter the CHKDSK command, DOS will report the •'Diskette not initialised" error message. Note also that the figures for "bytes total memory" and "bytes free" do not refer to the floppy disc but to the amount of available RAM in your computer. ~ NOVEMBER 1989 71 PHONEORDER TOLL FREE ALTRONICS 008 999 007 - Don't waste your time and hard-earned cash! Do your shopping at ALTRONICS Just phone your order on 008 - 999 - 007 for the best service in Australia. 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Operates on 9V battery ...... 0 0 en en en C0 0 0 -~z 0 Normally $499 • PA mixing • Fantastic tape recording • Stereo/mcno VCR recording • R/L 5 band graphic equalisers • T alkover facility • Separate headphone level control • Patch switch bank • Individual controls for Microphone, Phono 1&2, Aux. line 1&2, and Master slide level controls. • Outgoing moaage variable &om 30 to 120 .. c. • Amouncemmt-ouly mode • Incoming ........, ii voice anmollcd • Incoming call can be monitmod •R.opidcruc • Hu built-in mic,q>ha>e - great for dictatian Blend up to two magnetic or cryatal turntable•, two tape decka and two microphone. - all at oncell FULLY PROFESSIONAL SPECS: month 50 only at $149 (No back orders at this price) This Month $399 You Save $100.00 Resolution: Direct coun111r: I, I 0, I OOHz 1witch oek:ctable, pn:scalcd: 10, I 00, IOO<lh switch tclectablc Gate Time: 0.0IS, 0.IS, I.OS, switch telcctablc Accuracy: +/· I count +/- time buc error x &equcocy CHANNEL B Range: 100MHz to !GHz Reaolutlon: IOOHZ to !kHz ,witch ,electable Gate Time: 0.027S, 0.27S, 2.7S switch 1electable Period M ... urements (Channel A) Range: Hilz to 2.5MHz Resolution: 10-7S, 10-SS, 10-9S switch 1elcctable Tolallr.e Measuremenll (Channel A) Range: IOHz to 10MHz Resolution: +/-1 count of input Display: 8 digits. 7mmffld UID display with decimal point, ga.,, .,. overflow. kHz, MHZ and uS indicatian. l ~,; ~- .. .!!:.~~~ ~ )( 1060 $19.95 ::!,J a: 0 w z 0 :::c: D. I ,,r- s.. .., 1989 CtlUUOflll• r•• 62 for J,,U .,,.,ifk,,li,,,u oftw top ,,,..lily ....,.,.,, 110w Ill •n• grMler Nlu• for o,u ww""'- o-',. a 1530 Normally $499.oo This Month Only $399.00 SAVE $100.00 m m ~ • 8-digit mini-desk-top calculator• 3 key memory• Pen:ent key with add on/discount calculatian • Square root key • Larw:: plus key Sim: 123 x 107 x 23.5mm Weight 110g :c 0 z HEAVY DUTY PCB RELAYS -0en • Low profile ocly 25mm high s 4077 $5.00 each 10up $4.00ea s 4078 $5.00 each 10up $4.00ea 12V DC coil,. 1 X ro. 5A 24V DC coil, IX CX), 5A :c Labtech Dual Trace 20MHz CRO l> With Component Tester P,rf,ct for Ito- or offie• w FREQUENCY CouNTER Range: l<Hz to 10MHz duect counw, 10MHz to 100MHz ~ e d by 10 .:! C 1 GHz AMAZING OFFER! SAVE$100 THIS MONTH Measuring Mode: Frequency Measurements CHANNEL A Solar Powered Desktop Calculator '' ~ a: A 0512 Normally $199. This Input• Mic 1: O.SmV, 600 Ohms. Mic 2: O.SmV, 6000hma(Lowimp.), 2.SmV, 10k0hms(low Imp.); Phono 1&2 (Mag.) 3mV, 50k0hma; Phono 1&2 (Cry.), 150mV, 100k0hma; Tape/Tuner 1&2150mV, 100k0hma. Equ•II- • 5 ~eq,oncy bands: 60Hz. 250Hz. 1kHz, 4kHz, 12kHz • 80011 Cul Range, plus°' minua 12db O :I.!Qi..J,.r: -I -I This month only $1 o.oo -.,.-......1 Save an Incredible 37.5% A 2570 240V Mains Operated Ideal for "live" recording, our NEW Audio Mixing Console has truly sophisticated featurea: VAL.LE Pin Point Earru itr c08I 1111...uru oftiM•• o...,. UI d•"'""6 co1111eclors, PCB'•, ULTRASONIC CLEANER swilcl•••,.few•U.r,, glaa.•, wlllcleu, m. A wnotl Ila• Gootl Protli,ct O.,ie11 A-rtl for CETDCi1119B7 tlrwfti"II p,ru, WIii even clean your teelhl W ao 't ICl'atch or damage - UICI ordinary tap wer and aeaza milli of super-penetrating bubblet. Hoopilal tests shOW that lntruonic cleaning produces be- icsults safer than conventional m=thods. In Jw,t 3 minutes you wtll be amaud at the dlfl'erencel 0 0 (X) DESCRIPTION: Thi, model ii a dual -trace 20MHz Otcillotcq,e u.ing high brightncu CRT. The vertical unplif"'n ha"" high IIClllitivity of 5mV/Div and the &equency clmacu,riltic reoponae with the omooth roll off cxcc,eding 20MHz. The special circuit ii de1igncd 10 that a single compoocnt or components in or out of the actual circuit board can easily be 1c1111:d, ,equirlng no power to drive the circuit. The display shows component faults, component value, chanu:tcristia and 1cm components dynamically. FEATURES: • Compooonl Tetw • Wide bandwidth & high tcmitivity • Very low power consumption • High 10D11itivity X •Y mode • Z axia (intemity modulatioo) • Prom pone! electrical nee rotator • Rguallcd power supply for greau:r accuracy. $100 FREE BONUS OFFER Q 0155 LABTECH DUAL TRACE CRO $899 Q 0175 2 OFF 10:1 PROBE KITS $100 USUAL TOTAL$999 THIS MONTH YOU PA y ON Ly $899 Typical Component Test Status Patterns A 0100 TOP VALUE NORMALLY $199.00, ONLY t~~:THISSAVE '$25.00! Labtech Test Equipment for Life PHONEORDER TOLL FREE ALTRONICS 008 999 007 (0 (0 (0 0 0 ...... PHONEORDER TOLL FREE ALTRONICS 008 999 007 UHF 305MHz MICROPROCESSOR CONTROLLED Passive Infra Red Movement Detector WIRELESS SECURITY SYSTEM Why spend hundreds of doHars lnstalllng cabin and knocking holes In your walls? This UHF Alarm System uses no wires and Installs In an hour or so. Main Control Receiver Ideal for tbo lOWJF!OOllt, family rocm or hallways. Mounlll up on tbo wall or 011 top of boobbclvc■ otc. DcllOcll movcmolll within an:aof9Mby9M. s 5280 $129.00 Remote Piezo Alarm This unit is m optional lino carrier ieceivcr. ~ivc1 ■igna1 through' AC' lino i.e. it would ideally be locallOd in, uy, tbo roof ■pace and pluucd into maim power. Detector/Transmitter Unit (Reed Switch) "" 0 0 0, 0, 0, CX) 0 0 en -0z 0 • Wlret... reception ot external or Internal ..naors or ct,,tecton • Selectable home or away modes. Ali-s Internal or exter,al arml111 or JIIII external lo pro.tct,, protected movement Inside the bulldl"I • Bullt-ln pluo electric siren gives dllferent signals ror dllferent • functions • Sends signals down po,rer line lo acthate one or more remote • sirens The nwn COD!rol n:ccivcr rum on 2AOV AC with a 12V 1.2AH bl11my for emergency bock-up. All other unibl with the exception of the line cmricr run on a 9V bsttcry each. The avcrago lilio expectancy is approx. one :i-r• Systmn worlu aroond 305MHz f=iuency where then: is lcu chance of a lil,e alum. The nnge of the unit is normally 80 metro■ in open opoce. S 5265 Take It with you when you move $349.00 <( w w a: LI. ...J ...J ~ a: w z J: D. • • • With each ■y111:m onlcn,d we will include 3 wge • (HOUJO Window) dcmmmt llticbn, 200 x 75mm • and 3 (Car Window) dcmmmt llicb,n, 70 x 25mm. • Hand Held Control transmitter Unit Keep it 11 tbo bcd■ idc table - allow• you to arm the houae perimetm"I when you retire or you can tab it with you when you go out, armin& ~ur 1)'111:m af1IOr ~u lock the door. m s 5275 $59.00 $10.00 VALUE IN ALL ••••••••••••••••• -- Front Door Keypad Control Unit This handy ac=uory virtually duplicate, the function of the Mu1IOr Controller unit but at a mon, cooveniont location. Syllem can thu■ be ll'IDOd or diurmod without the uocd to go to tbo MutmuniL s 5285 $99.00 Country clients please allow an additional 48-72 hours ALTilOnlCl 174 Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept . Sydney (NSW Only) .Colin Fobister (02) 437 4077 Melbe,urne (Vic / Tas Only ) Brian Sorensen (03) 811 9967 Perth (WA , SA. OLD , N .T .) (09) 328 2199 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS a: 0 FREE THIS MONTH P 0 . Box 8350 Perth Mail Exchange W.A.6000 ALTRONICS RESELLERS Chances are there ,s an Al!ronics Reseller oght near you - c heck this 11st or ph o ne us to r detatls of the nearest dealer Ple ■ H Nole: Resellers have to pay the cost of freight and insurance and therefore the prices charged by 1nd1v1dual Dealers may vary slfghlly from this Catalogue - 1n many cases . however . Dealer prices wil l still represent a significant cost saving from prices cnarged b y Altronics Competitors Oon'I forget our E1pre11 Mall and Phone Order Servtce - for the coel of • local e11II, Bankcard, YIN or Mutercard holder ■ e11n phon• order tor aame day de ■ oatch. Blue Ribbon DHlera are highlighted with a ■ These Dealers generally carry a comprehensive range of Altronic products & kits or will order any reQuired item for you STANDARD DELIVERY I PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA WIDE - Wo proc ess yo ur order the da y recei ved and despatc h via Australia Post Allow appro• 7 days from day you post order to when you receive goods $7.00 OVERNIGHT JETSERVICE - We process your order the day received and despatch via Overnlghl JetMrvlce Courter for delivery next day Country areas please allow add1t10nal 24-48 hours Weight l1m1t 3Kgs (3Kgs covers 95% of Orders ) $10.00 HEAVY HEAVY SERVICE - All orders ol 10Kgs or more must travel Express Road - Please allow 7 days for delivery INSURANCE - As with virtually every other Australian supplier. we send goods at cons ignees risk Should you require comprehensive insurance co ver against loss or damage please add 1% to order value (minimum charge $1 ) When phone ordering please request " Insurance· TOLL FREE PHONE ORDER - Bankcard .Visa . Mastercard Holders can phone order toll free up to 6pm Eastern ~ tandard Time Remember with our OYernlght J•tNntce we deliver next day ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALOTON K.B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521713 Farmer Electronics 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOURNE Winscott Trading 6995740 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 ,QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN FORTITUDE VALLEY Economic Electronics 62523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058Xanthos Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 SA CITY Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 COUNTRY COFFS HARBOUR Coifs Habour Electronics 525684GOSFORD Tomorrows Electronics 247246 GRAFTON East Coast Electronic 431250 NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 WA "'C :I: 0 z m 0 e BANKCARD e VISA e MASTERCARD e PHONE TOLL FREE 008 999 007 e NEXT DAY JETSERVICE DELIVERY C 0 w • •• • s 5290 $125.00 s 5270 $55.00 ••••••••••••••••• a: ~ Suitable for window■ and doon of cncl.-d n,od ■witch and mnoYable enclomdllllpot. COll■ isbl Fealurt1: COUNTRY PHONEORDER TOLL FREE ALTRONICS 008 999 007 :a C :a a rr- .,, :a m m )> !:i' :a -z 0 ( ') en 0 0 0) (0 (0 (0 0 0 ...... EI.ECTROMCS FOR EVERYONE On the face of it, switches are easy to understand devices which are either on or off. But there are many different sizes and types. Some are designed for high voltages and high currents but most carry only flea power currents. PT.5: WHAT YOU NEED TO KNOW ABOUT SWITCHES By L-XO-SIMPSON Most electronic devices have an on/off switch and even those that don't, such as some calculators, watches and clocks, still have switches to control their various functions. Switches can range from single contact single position devices to multiwafer multi-position devices that cost big dollars. If you wanted to count up all the different types, sizes, styles, ratings and so on, you would run into thousands. Single pole, single throw The simplest switch of all is the single pole single throw type. It has a single moving contact (the pole) which is either on, so that current flows, or off, so .that current can't flow. This simple on/off action is referred to as 'single throw'. Fig.l(a) shows how a single pole, single throw switch is usually depicted while Fig.l(b) shows a variation whereby the on and off conditions are labelled. For a single pole, single throw switch, the pole may be shown as a short straight line or as an arrow, as in Fig.l(b). There are only two terminals on this type of switch. "Single pole single throw" is usually abbreviated to SPST. SPST switches are probably the most common type of all. They are used in the hundreds of millions (maybe even billions) as on/off switches in all sorts of electronic gear, mains appliances, light switches and power points. Many power switches in appliances have two moving contacts so that both the active and neutral lines can be switched. These switches are referred to as 'double pole single throw'. These are shown on circuits as in Fig.2. Each switch section is distinguished by a label such as Sla and Slb, or perhaps SWla, SWtb. Single pole, double throw Off (b) ----<I" o!!L- ~0-- Ag. 1 SPST SWITCH Fig. 2 OPST SWITCH ~ S10-Flg. 3 SPDT SWITCH ~ s1ao-~ S1b0--Fig. 4 DPDT SWITCH These diagrams show some simple switch configurations, ranging from SPST to DPDT. In the double pole types, the two switching contacts move together. 76 SILICON CHIP A step up in complexity from the single throw switch is the 'single pole double throw' switch, normally referred to in textbooks as an SPDT switch. In this type, the moving pole of the switch can be moved to one contact or the other. In this way, a SPOT switch can be used to connect power to one circuit or another, as shown in Fig.3. Note that an SPDT switch has three terminals, usually with the centre terminal being for the moving contact. SPDT switches are sometimes referred to as 'two way' switches. If you have two-way light switches in your home, you will find that B 0 F G E H There are many different types of toggle switches. Types A, B, C, D and H are DPDT while types E and G are SPDT. SPDT and DPDT switches are also known as changeover switches. Type Fis the simplest, SPST (single pole single throw). each switch is, in fact, an SPDT type. Next step up from the SPDT type is the 'double pole double throw' or DPDT switch. This has two poles and two positions. It is shown in Fig.4. Again, these usually have two sets of three terminals, with t,h e centre ones being for the moving contacts. SPDT and DPDT switches are often referred to as having "changeover" contacts because they change from one set of contacts to another. You'll also come across relays with changeover contacts and these provide essentially the same switch function. Double throw switches also come with more poles than two. You can have 3 pole, double throw (3PDT), 4 pole double throw (4PDT) and so on. Toggles, sliders and rockers Having discussed some basic switch contact arrangements, let's Slider switches are easily recognised. The two on the right of the photo are DPDT types. At the left are two DIP switches. Both contain 10 SPST switches with the one at top being miniature rockers and the one below using sliders. NOVEMBER 1989 77 B Rocker switches are often illuminated. Type A uses a miniature 12V incandescent lamp while type B uses a neon and is therefore suitable only for high voltage switching. Type C is a paddle operated toggle. Toggle switches are also said to have an "over centre" action which refers to the fact that you have to move the lever past the centre point of its travel before the switch contact flicks to the wanted position. In 240VAC mains appliances and also in cars, you will generally find that toggle switches are springloaded more strongly for the 'off' position than for 'on'. You'll also find two conventions for 'on' and 'off'. Equipment designed for the American market generally has toggle switches which are up for 'on'. Most of the rest of the world uses the same convention as in Australia: down for 'on'. You could argue all day as to which is the right or most sensible convention but it's largely a matter of what you've become used to. Rocker switches On a multiwafer switch the wafers can be close together or spaced apart to reduce the capacitive coupling between them. Type A uses a mains-rated switch section at its rear while type B has a shield plate between its two wafers, to further reduce the capacitance between them. Rocker switches are very common and simply use a rocker in place of the lever of the toggle switch. They have the same overcentre snap action so you can operate them by feel. Are they any better than toggle switches? Probably not. The choice of a rocker switch over a toggle or any other switch is more usually a matter of styling than engineering considerations but rockers do have two drawbacks. First, it is not so easy to see whether a rocker switch is up or down (or on or off) - the so-called "visual status". Second, rocker switches usually require a rectangular cut-out to mount them in a panel and often two screws as well. By contrast, a toggle switch only requires a circular mounting hole. Slide switches look at switch types such as toggles and sliders. The toggle is the most common of all and is used by the squillion in all sorts of applications in every field of electrical, electronic and automotive engineering. Superficially, you might think that the word "toggle" merely refers to the stubby lever by which you operate the switch but it goes further than that. A toggle actually consists of two levers connected by a knuckle joint and spring loaded to take up one position or the other. 78 SILICON CHIP When force is applied to the top lever, the sping is extended so that eventually, the bottom lever suddenly flicks over to the other position in a very positive fashion. In a toggle switch, the bottom lever is actually the moving contact. Toggles were among the very first switches to be developed because they provided a means of very positively breaking a circuit. Toggles provide good "tactile feedback" which means that you can operate them by feel. As the name suggests, slide switches operate by sliding from one position to the other. They don't have any spring-loading so they have to be pushed all the way in one direction or the other to make sure they operate properly. Because their switching action is not positive (compared to toggle switches), slide switches are not suitable for many applications. They are not used on mains appliances or in cars. They are generally confined to applications Wafer switches come in all shapes and sizes. Types A, C, D, E and F are all single wafer designs while types B and G have two wafers each. Type F is a lever operated three pole three position switch. All except type D are of open construction. Type D is available with an adjustable stop so that the number of operating positions can be varied. where only very low power has to be switched and where a compact switch is required, such as on calculators. Fig.5a shows the symbol for the simplest slide switch, an SPDT type, but most slide switches you will come across will be of the DPDT type with 6 terminals as shown in Fig.5b. Just to confuse the issue, slide switches are available with three or four positions. These generally have a 'detent' action so that they have slight stops to identify the intermediate positions of the slider. - -- (a) SPDT SLIDE Fig. 5 (b) DPDT SLIDE Slide switches operate by sliding the moving contact(s) from one position to the other. Fig.5a is the symbol for a SPDT type while Fig.5b shows a DPDT type. Fig.6 shows single pole 3-position and 4-position slide switches. While the terminals of DPDT and SPDT slide switches are easy to identify (the moving contacts are the centre terminals), those on 3 position and 4 position switches are in a class by themselves. The only practical way to identify their contacts is to use a multimeter to test for continuity. DIP switches DIP switches are really just a bunch of very small slide or rocker switches in the same size package as a dual in line package integrated circuit. Each switch is a SPST type and they commonly come in packages of 4 (8 pin) or 8 (16 pin), although they are also made in 2-way, 3-way, 5-way, 6-way and up to 12-way. Other variations are available with vertical switch operation with up for 'on' or down for 'on'. You'll also see DIP switches referred to as DIL switches. DIP switches are widely used in fig. 6 These two circuit symbols show a single pole 3-position slide switch (top) and a single pole 4-position slide switch (bottom). computers and printers to program the endless options that this equipment offers. Rotary switches For switches with more than 2 poles and more than 2 positions, the rotary switch is the answer. It can provide lots of poles and lots of settings. Naturally, as the number of poles and positions increase, the cost goes up. Most of the rotary switches you'll NOVEMBER 1989 79 _/F o-S1ao--- S1a 0-0>---- __/F. 0-- S1b 0---- S1b _/;;=- 0-0>---- (a) S1c Fig. 7 (b) 0-- 0---- If lots of switch positions are required, the rotary switch is the answer. Fig.7a shows a 2-pole 5-position switch while Fig. 7h shows a 3-pole 4-position type. come across at parts suppliers will be single wafer designs and they come in the following configurations: 1 pole 12 position, 2 pole 6 position, 3 pole 4 position and 4 pole 3 position. In other words, if you multiply the number of poles by the number of positions, you will always get the figure 12. The switches just described are said to have 30° indexing because there is 30° of rotation between each switch setting. Other indexing figures you'll come across from time to time are 45° , 60° and 90° . Fig. 7 shows a 2 pole 5 position switch and a 3 pole 4 position switch. Note that each pole of each switch is in the same relative position. Multiwafer designs Where larger numbers of poles and positions are required, rotary switches have more than one wafer. For example, with two wafers, you can have 2 poles 12 positions or twice any of the combinations listed above; with three wafers, you can have 3 poles 12 positions and so on. Our photos show a number of multiwafer switches. You can also have differing numbers of poles on each wafer, as you might, for example, on a 5-pole 3 position switch. This could have 3 poles on the first wafer and 2 poles on the second. The wafers usually have spacers When you want a large number of switch poles, nothing can heat a large multiwafer switch. This printer switch has 25 poles and 4 positions. 80 SILICON CHIP between them which makes them easier to wire up but where space is at a premium the wafers may be butted up together. In printer switchers, you can find really massive multiwafer switches, as shown in another of the photos accompanying this article. Multiwafer switches can be fitted with shield plates in between the wafers. This reduces the capacitance between the switch sections and is useful where the coupling between switch wafers must be kept to a minimum. Some single wafer switches are of closed construction. This has the · advantage of keeping dirt out of the switch contacts and probably also reduces corrosion. Another feature you will find on many wafer switches is an adjustable stop. This enables you to change the number of available switch positions. For example, you may have a 2 pole 6 position switch and you only want to use 4 positions. To achieve that, all you do is lift out the washer/stop on the switch bush (the threaded mounting portion of the switch) and set it back for the required number of stops. There are a number of other variations of rotary switches you will come across. One is the lever operated wafer switch shown in a photo accompanying this article. Another is the rotary PCB mounted slide switch. This is a multipole, This photo clearly shows the action of a "make before break" switch. Notice that each of the three poles (or wipers) is at a point between two adjacent switch contacts. Since the adjacent contacts are shorted together at this point, this type of switch is referred to as having "shorting" contacts. Pushbutton switches come in a wide variety of types, some of which are shown here. Most of these are "alternate action" meaning that you push them once to turn them on and then push again to turn them off. The remainder are momentary contact types, meaning that they "make" the circuit only while they are pushed. Type C is an illuminated pushbutton, using a 6V incandescent lamp. Types A, H and N are DPDT alternate action switches. The contacts on one side allow installation on a printed circuit. The contacts on the other side allow conventional wiring. Type M is a pin switch, used as a boot or bonnet switch in car burglar alarms. It grounds or "makes" the circuit when the plunger is released. Type L is a normally on switch, similar in principle to those for refrigerator and car doors. multi-position switch in which the linear actuator is operated by a flat Bowden cable from a rotary knob. Made by the Alps Corporation in Japan, these are widely used in hifi amplifiers and receivers. Incidentally, you will sometimes see the moving contact of a switch referred to as the wiper. This applies particularly in rotary multiposition switches. In fact, most rotary switches are said to have "wiping contacts" a good feature because it keeps the switch contacts clean. Make before break contacts Two terms that you'll occasional- ly come across when dealing with switches is "make before break" and "break before make". This describes the action of contacts in a changeover switch or in a multiposition switch. Let's take "make before break" contacts for example. In a DPDT switch with make-before-break contacts, the moving contacts stay in contact with the first set of contacts while they are being moved over to the second set of contacts. The switch "makes" the second set of contacts before "breaking" the first set of contacts. In some circuits it is most important that 'make before break' swit- ches are used. For example, in an amplifier where a multi-position switch is used to vary the feedback settings, it is most important that the feedback circuit is connected at all times. If the feedback circuit was broken, at the moment of switching from one setting to another, the amplifier would momentarily lose all its feedback and would generate a tremendous voltage spike which could damage it or its load. Another place where 'make before break' switches are important is in the range switch of a multimeter. It is important that the measuring circuit not be broken when switching ranges on the multimeter, particularly when measuring current. 'Make before break' switches are also referred to as having 'shorting' contacts because the two adjacent contacts are shorted together during the act of switching. Break before make switches Inevitably, there have to be NOVEMBER 1989 81 - (a)-----e e- (b)~ Ag. 8 Pushbutton switches can be either normally open (Fig.Ba) or normally closed (Fig.Sb). Pushbutton switches This is an 8-way latching switchbanlc. Pressing one switch cancels and previously pressed switch. Each switch is a DPDT changeover. Numeric keyboards like these use matrix wiring, with four rows and three columns. They need to be used with an encoder IC which continually scans the rows and columns to detect when a particular button has been pressed. While separate buttons are used in these two keyboards, they both use membrane switches. 'break before make' switches, don't there? In fact, all toggle switches are 'break before make' types. Many circuits must use 'break before make' switches otherwise overloads could occur during switching. How do you tell the difference between 'make before break' and 'break before make' switches? On wafer switches with open construction, it is quite easy. Just have a look at the switch wiper (or wipers) and watch their action as the switch is 82 SILICON CHIP slowly switched from one position to the next. Are two adjacent contacts shorted together momentarily at some point in the switching? If so, the switch is a 'make before break' switch. If the switch is of closed construction, you can use your multimeter to test for the shorting of adjacent contacts during switching. Preferably you need to use an analog meter [ie, not a digital meter) for this test because the shorting actions may be very brief. Pushbutton switches generally come in one of two forms: momentary contact and alternate action. "Momentary contact" is easy enough to understand - the switch makes contact only while you push the button down. They are the type used in doorbells and any application where the circuit should be on for a short time. Momentary contact switches are also referred to as having "normally open" (NO) contacts since they are "closed" only when the button is pushed. "Alternate action" is another term for push on, push off. These are often used as the on/off switch on TV sets and hifi equipment. These normally have DPDT contacts. Another type of pushbutton switch is one with normally closed contacts. When you push the button, the contacts are opened. These are widely used as door switches in refrigerators and in cars. These normally have an SPST switch. A variation on these is the pin switch, as used in car burglar alarms for boot and bonnet protection. These connect a single wire to the car chassis. When the switch pin is depressed, the circuit is opened. Switch banks Pushbuttons are often mounted together in banks and they may be latching and/or interlocked. When the buttons are interlocked, you push one button to unlatch a previously pushed button. These are often used as selector and mode switches on high fidelity audio equipment and as mode switches on some multimeters [eg, the Fluke 8060A). • ~ ~ These are microswitches as used in a lot of machinery to "limit" movement. They are also commonly referred to as "limit" switches. You'll find them in the door interlocks on microwave ovens, in photocopiers, garage door openers, juke boxes, ten-pin bowling machines and virtually all electrically powered machinery. Keyboards All keyboards, whether used on calculators, telephones, computers, microwave ovens or whatever, are simply a bank of SPST momentary contact switches arranged in a matrix. Typically, for a numeric keyboard used on a telephone, there are four rows and three columns, giving 12 possible selections. COL 1 COL 3 COL 2 Fig. 9 All keyboards use a bank of SPST momentary contact switches arranged in a matrix. Digital circuitry is used to determine which switch is pressed. When one button is pressed, it connects a row line to a column line. The rows and columns are continually scanned by associated digital circuitry which 'decodes' the row and column selected to determine which button has been pressed. The digital circuitry then generates a code in serial form which can be sent via a pair of wires to the device being controlled. Fig.9 shows a switch matrix for a 12 button numeric keyboard, as used on telephones. By using a matrix arrangement and accompanying decoding circuitry, the number of switch wires is greatly reduced. If a matrix wasn't used, the minimum number of connecting wires for a 12 button numeric switch would be 13 (one wire for each switch plus a common wire). Instead, by using a matrix, the number of wires is only 7. For computer keybards, the advantages of matrix switching are even greater. Instead of having 102 wires lfor a 101 button keyboard), the number is 32 (16 rows, 16 columns) or less. " Ahah" , you might say. " The cable from my computer keyboard uses a 5-pin DIN socket, so it must only have 5 wires. How do you get 32 wires? " The answer is that there are 32 wires, give or take a few, from the keyboard matrix to the microprocessor chip inside the keyboard. Not many people are aware that a separate microprocessor is inside their computer's keyboard but it is. This microprocessor continually scans the keyboard matrix to detect when keys have been pressed and also generates the corresponding ASCII code. This code is fed serially down the keyboard cable to the computer so only 5 wires are needed. This is just one of many circuit techniques used these days to reduce the number of connecting wires. Connecting wires cost money in terms of material and labour cost and they a lso contribute to unreliability in electronic equipment. Hence, designers are continually on the lookout for ways to reduce connecting wires. Switch matrices, as used in digital keyNOVEMBER 1989 83 They may be lever or roller actuated and normally are of the SPDT format. They are often used as limit switches for electrically controlled doors, in juke boxes and as the door interlock switches in microwave ovens. Since they are so often used for limiting the travel of machinery, they are also referred to as "limit" switches. Illuminated switches These switches are an interesting combination. They are PCB mounted multipole slide switches which are operated by a flat Bowden cable by the front panel rotary knobs. The advantage of these over conventional wafer switches is that they allow more flexibility in the design of the control panel and allow the switch elements to be placed where needed on the printed circuit board. boards, offer big advantages in this respect. Membrane switches Membrane switches are commonly used in numeric keyboards where water, dust and dirt is likely to be a problem. The switch contacts are usually in the form of conductive tracks deposited on plastic sheets which are pressed together to make contact. Since they are completely sealed, dust and dirt is not a problem. That is why they are so commonly used 84 SILICON CHIP on the control panel of microwave ovens. They are also used as the keys on credit card sized calculators. Membrane keyboards were also used on early low-cost personal computers such as the Sinclair ZX-80. They are not good for this application though, because they don't have any 'feel'. Micro switches Micro switches are used where a very small switch lever travel is required, hence the term "micro". Many rocker and pushbutton switches are illuminated. When they are turned on, they are illuminated, often by the supply voltage they are being used to switch. The main point to watch when using these switches is the type of illumination. For example, illuminated switches for 240V AC mains employ an internal neon lamp together with a current limiting resistor of lOOkO or thereabouts. Because the neon lamps require at least 70 volts across them to light, these switches are not suitable for low voltage operation; not because they won't switch but because they won't light. Many illuminated switches use a miniature 6.3 volt or 12 volt inGandescent lamp. These usually have separate pins for the lamp supply. Other illuminated switches use light emitting diodes. These have the advantage of very long life but they're not so good in brightly lit areas or in cars, especially when sunlight falls onto the instrument panel. Reed switches These really shouldn't be called switches. More correctly, they are reed relays. They normally have one pair of SPST contacts sealed into a glass tube. The relay is operated when a strong magnetic field is applied, either by a small permanent magnet or by an energising coil fitted over the glass tube. Mercury switches Mercury switches are also referred to as 'tilt' switches. They are basically two contacts sealed into a small glass bulb containing a small blob of mercury. When the switch is tipped one way, the mercury shorts the contacts and is made. When tipped way, the mercury moves the contacts and the broken. the circuit the other away from circuit is Thumbwheel switches These are in a class of their own. Essentially they are an edge mounted rotary switch with 10 positions. Often used on digital equipment, they can be designed to provide a decimal output, BCD output or hexadecimal output. The original thumbwheel switches were operated by the thumb, as the name suggests, but now there are variations which have little buttons to increase (increment) or decrease (decrement) the switch setting. These are sometimes called digital pushbutton switches but they are functionally the same as thumbwheel switches. The means of encoding to provide decimal, BCD or hexadecimal output is mechanical and is achieved by the arrangement of the switch contacts and the internal printed circuit pattern. A BCD thumbwheel This is a 40-position channel selector switch as used in a CB radio. Its operating principle is similar to that used in thumhwheel BCD and hexadecimal switches. By using an output code, it greatly cuts down on the number of switch wires used. While this particular sample has a lot of pins they are duplicates. Only 8 wires are needed to encode the 40 separate channels. switch usually has five terminals, three for the BCD output and two as common. ANTRIM TOROIDAL TRANSFORMERS Interestingly, the 40 position switches used in CB radios use the same operating principle as thumbwheels. They produce an encoded digital output which is decoded by an associated integrated circuit to determine the channel selected. This enables the switch construction to be simplified and the number of connecting wires greatly reduced. In keeping with the trend to making everything smaller, there are now miniature thumbwheel switches designed for mounting directly onto a printed board. As the name suggests they again perform the same function as a · thumbwheel switch except that they are far too small to be operated by anyone's thumb. Instead, they are set by a small screwdriver. Other types There some switches we have not mentioned but after reading this article you will be able to recognise their basic types such as knife switches (DPDT) and key-operated switches (nsually DPDT). ~ General Construction OUTER WINDING QUALITY TOROIDAL POWER TRANSFORMERS, MANUFACTURED IN U.K. NOW AVAILABLE EX-STOCK AT REALISTIC PRICES. TAX PAID PRICES 15VA 30VA 50VA BOVA 120VA 160VA 225VA 300VA 500VA 625VA 10+ 1- 9 32.80 31.70 36.00 35.00 38.50 37.20 41.75 40.35 44.95 43.50 55.70 52.20 62.00 58.20 72.80 68.25 100.00 93.75 112.00 105.00 Enquiries from resellers and OEMs welcome. Quantity prices and data sheets available on request. Distributed in Australia by Harbuch Electronics Pty Ltd, 90 George St., HORNSBY, NSW, 2077 Phone (02)476-5854 Fax (02)476-3231 NOVEMBER 1989 85 THE WAY I SEE IT By NEVILLE WILLIAMS Electronic identification: a boon or a catastrophe? If the proponents of electronic or RF identification are to be believed, it could turn out to be revolutionary. Applications currently being discussed range from freight wagons, road vehicles and containers to living creatures - including human beings! As you may recall, the subject of electronic identification was raised last month by a reader who drew attention to an article in "Farm" magazine which described a subminiature electronic identification device. Especially applicable to animal breeding stock, it is being distributed - and used in their own stud - by an Adelaide-based company: AGTEC Australia Pty Ltd. Essentially a tiny integrated circuit chip in a 10mm-long plastic capsule, it can be implanted under the hide of an animal, with minimal pain and disfigurement, using a special hand-held syringe. During manufacture, each capsule is encoded with a different number, which can be read electronically with the aid of a suitable interrogator. By referring the encoded number to a data bank, the identity of the animal can be checked, along with other relevant information. The reader in question (P.D. of Murchison, Vic) was intrigued by the article in "Farm" magazine but was also disturbed by it. His reasoning: if we develop a high level of expertise in electronically tagging animals, who is to say that the next step won't be to tag people? 86 SILICON CHIP As I write, the October issue carrying the arlicle has not yet reached the newsagents and I have no way of knowing if other readers will share P.D's apprehension; or if they do, how many will put pen to paper. Another approach In the meantime, I came across an article in the computer section of the "Sydney Morning Herald" (August 14th, 1989} detailing another ID/information system. This is currently being put in place at Harry M. Miller's SimmentalHereford Dunmore stud at Manilla, NSW. It rates a mention here, if only because it illustrates a different approach to that adopted by AGTEC. At Dunmore, they are still using ordinary ear tags to identify individual animals but are concentrating instead on the development of a comprehensive on-site computer data bank. This is based on a program called "Ag-Vantage", developed by Alan Morgan of Far South Coast Computer Specialists, Bega, NSW (phone 064 923 066}. According to the article, reaction to the system by the management at Dunmore is nothing if not enthusiastic. I quote: "We have been using AgVantage for about 2½ years and it has saved us more time, given us better results, earned us more money than you would believe. With it, we have a complete history of each animal. We know which are the good producers, which are not; which are earning their keep, which are on the bludge". The next step at Dunmore is to install automatic electronic weighing as the animals pass through a race, with provision to feed the information into the data bank. Together, the AGTEC and Dunmore stories provide a practical illustration of what's said to be ahead for Australia's huge livestock industry: electronic tagging of individual animals and computerbased information storage, management, handling and marketing. That could add up to a lot of equipment. Outback electronics As an urban dweller, you may find all this a bit of a yawn; something the "cockies" are up to, out beyond the black stump. If they want to mess about with ID or AID (animal ID) or EID (electronic ID) or RF ID (radio frequency ID}, so be it - as long as they keep on sending us meat to eat and horses to race! In that case, you might be interested in a totally different story from the Barrier Reef, featured recently in the TV show "Beyond 2000". For years, crown of thorns starfish have been gnawing away at the coral, while frustrating attempts to document their migratory habits. They dispose of ordinary tags by shedding the arm to which they're attached and growing a new one! But researchers appear to have come up with an effective answer. You've guessed it: a tiny integrated circuit in a 10mm-long plastic capsule which is injected into the crown of thorns' body by means of a hand-held syringe - both items remarkably like those in last month's AGTEC story. Not surprisingly, the underwater interrogator is different and uses a loop which is lowered over the starfish. But the result is the same. A low frequency radio signal energises the chip in the capsule which obliges with its own unique number - in the case of the "Beyond 2000" story: 7F7E3F4565. Still not convinced? Well, what about the nationwide TV interview, in the same week, with an American judge who's been promoting the use of RF ID devices to keep track of plain, ordinary human beings? Sentenced to home detention rather than prison, they are fitted with an electronic ankle bracelet which sounds an alarm at the control centre if the detainee ventures beyond the allotted boundary'. I concede that home detention may be preferable to a prison cell and less of a burden on the public purse. But the interview wasn't limited to lawbreakers; the conversation turned quite casually to other possible uses for the device - like keeping track of. the aged and menta:lly handicapped. It was all about the capability of the equipment with not one word about the broader implications of attaching it to humans who are socially somewhat inconvenient. Ankle straps today; implants tomorrow? ID - the broad background Last month, I mentioned papers made available to me by two departments at the University of New England, Armidale, NSW: the AGBU (Animal Genetic & Breeding Unit) headed up by Dr Keith Hammond, and the CEA (Centre of Electronics in Agriculture) which is headed by Dr Royden Lake. INTERROGATE/RECEIVE ANTENNA '-....,_ SENSING/TRANSMIT ANTENNA "cT/ 'f'I rI - - - - INTERROGATOR (AXED OR PORTABLE) f POSSIBLE DATA LINE I / I II ~- {~ \ POSSIBLE OPTICAL TRIGGER J 13-~ POSSIBLE OPTICAL RECEPTOR POSSIBLE TRIGGER/ SUPPLY SIGNAL Fig.1: concept diagram for an electronic ID system. The interrogator sends an RF interrogation signal, plus a possible second RF signal to power the transponder. Some systems use an optical activating signal. The return signal is intercepted and displayed by the interrogator. In fixed installations, the interrogator may be linked to the central computer data bank. By way of background, one such paper points out that RF ID dates back to at least the 1960s, when it was adopted as a way to keep track of railway freight wagons, particularly in marshalling yards or when crossing state or national borders. Readers with still longer memories may recall wartime IFF (Identification Friend/Foe) units, which enabled night fighter planes to interrogate other aircraft before launching an attack. Of necessity, early interrogators and transponders used valve based circuitry, limited in its usefulness by bulk, power needs, complexity and cost. The amount of data which c9uld be exchanged was also very small. One early system, for example, relied simply on measuring the resonant frequency of a presettable tuned circuit in the transponder. In the 1970s, transistor technology brought about a sharp reduction in the size, power requirements and cost of ID equipment. It also became possible to transfer more information, even if only by the application of "brute force" methods. In the late 1970s, SAW (surface acoustic wave) technology provided a breakthrough in transponder design. I quote from a seminar paper by Robert Gouldson and Graham Murdoch (Magellan Technology Pty Ltd, Perth): "SAW transponders utilised a tapped microwave acoustic delay line to generate a coded sequence of microwave pulses - a very elegant solution to the production of ID codes". With the level of miniaturisation available in the 1980s, it has become possible not only to reduce radically the size and cost of both interrogators and transponders but to record, store and retrieve large amounts of digitised data under what would once have been intolerable environmental conditions. Progress in ID/information technology over the past five years is described in the literature as "drama tic", with the industry reportedly set to take off in a big way on farms, in factories, bulk stores, transport, etc right through to personnel management. Protocols & pipedreams Whether this can happen in the same structured way as the bar code revolution is debatable. If the ID/information industry does "take off" , it may well do so in the manner of pen full of startled chooks: madly and in every direction at once! Last month I mentioned that Dr Hammond of the AGBU had expressed the fervent hope that a common protocol could be adopted for recorded data in the livestock industry, to simplify the exchange of information. Perhaps " forlorn" would have been a better word. In a survey of their needs, breeders, dairy farmers, pastoralists, beef producers and abbatoir operators have at least agreed that NOVEMBER 1989 87 Typical Electronic ID Systems e ACTIVE MICROWAVE: a 10.5 GHz interrogation signal triggers a battery powered transmitter on the transponder which repetitively retransmits a 2 .45GHz signal modulated by the ID code. 64 bits, including 30 bits reprogrammable "on the fly". Range: 2 metres. • ACTIVE UHF: a 930MHz interrogation signal is reflected by a field disturbance antenna on the transponder. A battery powered circuit switches the antenna in accordance with the ID code. 128 bits, re-programmable by purchaser. Range: 40 metres. • ACTIVE HF: an optical trigger pulse activates a battery powered transmitter on the transponder. Re-transmitted HF signal is modulated by the ID code . 20 bits or more. Range: 30 metres, depending on the optical path and future ID/information technology must be better than present manual methods. But their expectations of such equipment were diverse in the extreme: its physical characteristics, ruggedness, role, operating life, portability, reading distance, data capacity, compatibility with data banks, and so on. Some of the requirements were extravagant, others impractical with present technology. A none-too-optimistic Dr Hammond summed up the situation thus: "The inital approach by virtually all concerned is to envisage one ideal system that copes, cost effectively, with all requirements and suits all environments. A single ideal system is a pipe dream. "There is a range of specific and quite different operating environments and requirements. The most cost effective specifications for each will be quite different. In addition, there are at least half a dozen generic technologies, all of which are immature. "Strong competition should be encouraged if the best systems are to be developed and made available at lowest cost". 88 SILICON CHIP beam intensity. • ACTIVE LF: a 132kHz interrogation signal activates a battery powered transmitter on the transponder. The 132kHz signal is divided down, modulated by the ID code and re-transmitted. 64 bits, reprogrammable by purchaser. Range: 3 metres. • PASSIVE MICROWAVE: interrogation signal swept between 2.9GHz and 4.1 GHz at 4kHz rate. Preset cavities in transponder antenna resonate at selected frequencies. Timing of signal reflected by the cavities with respect to sweep frequency give the ID coding. 65 bits preset at manufacture. Range: 2.5 metres. • PASSIVE UHF: a pulsed 91 5MHz interrogation signal converted into surface acoustic waves on a lithium niobate crystal in the Typical systems Competition there certainly will be. Typical system concepts are listed by Murdoch and Gouldson (mentioned earlier) and are summarised in the accompanying panel. Incidentally, the description " Active" means that the transponder has its own battery such as a longlife lithium cell, the same as used in heart pacemakers. They are very reliable, with a shelf life of 15 to 20 years, but the actual in-service life depends on usage. "Passive" transponders have no battery. Some simply reflect the interrogation signal back to its source, but modified in some way in accordance with in-built ID coding. Others convert portion of the interrogation signal into electrical power to operate their own internal circuitry. Some passive transponders use both techniques. Compared with passive transponders, active systems offer greater reading range and higher data capacity, and can support more complex functions such as a reprogrammable memory and a real time clock. They can usually get by with a weaker interrogation transponder. Delayed versions of the interrogation pulse are retransmitted as per the ID code. 30 bits preset at manufacture. Range: 2 metres . • PASSIVE HF/LF: a low frequency field powers the transponder. An RF interrogation signal is reflected by a field disturbance antenna on the transponder which is switched in accordance with the ID code. 34 bits, programmable by the purchaser. Range: 0.6 metres. • PASSIVE LF: a 1 00kHz interrogation field is received by the transponder. A 50kHz subharmonic field is generated by selectively connecting the tuned antenna. The sub-harmonic field is phase modulated by the ID code and re-transmitted. 30 bits or more normally preset on manufacture. Range: 1 metre. signal and may therefore be easier to license. Without batteries, on the other hand, passive transponders tend to be less expensive and more reliable over long periods, even to offering "unlimited" service life. Either way, systems using high signal frequencies are more compact and efficient, and have better range, directivity and speed of data transfer. On the other hand, lower frequency systems are less sensitive to antenna orientation, less susceptible to man-made electrical interference and on-site contaminents and again, easier to license. One other point: the smaller the transponder, the smaller the effective antenna, and the less the potential reading range. There is much more in the discussion papers but enough has been said to indicate that ID design engineers are faced with a daunting array of variables to sort out. If they also manage to come up with industry standards, they'll have really earned their keep. "Smart" tags Finally , among the articles February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players . May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show. August 1988: Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Switchmode Charger for 12V Gel Batteries; Vader Voice. October 1988: Stereo FM Transmitter; High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number. November 1988: 120W PA Amplifier Module; Poor Man's Plasma Display; Car Safety Light; How to Quieten the Fan in Your Computer. December 1988: 120W PA Amplifier; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Re·ceivers . January 1989: Line Filter for Computers; Proximity Detector for Cars; How to Service Car Cassette Players. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher for Model Railways; Lightning & Electronic Appliances. March 1989: LED Message Board; 32-Band Graphic Equaliser; CD Compressor; Amateur Band FM Receiver April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For PCs; Simple Stub Filter For Suppressing TV Interference. June 1989: Touch-Lamp Dimmer; Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes. July 1989: Exhaust Gas Monitor; Extension for Touch-Lamp Dimmer; Mains Hum Sniffers; Ultrasonic Car Alarm. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser; Garbage Reminder; Introduction to Stepper Motors. September 1989: 2-Chip Portable AM Stereo Radio; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector; Simple DTMF Encoder. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes; 1 Mb Printer Buffer; Installing A Hard Disc in the PC Note: November 1987, December 1987 & January 1 988 are now sold out. Use this handy form to order your back copies ~ r---------------------------------- • --, Please send me a back issue for: D February 1 988 D March 1988 D April 1 988 D May 1988 D June 1988 D July 1988 D August 1988 D September 1 988 D October 1 988 D November 1 988 D December 1 988 D January 1989 D February 1989 D March 1989 D April 1989 D May 1989 □ June 1989 D July 1989 D August 1989 D September 1 989 D October 1989 Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my □ Bankcard □ Visa Card □ MasterCard Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_ _ / _ _ / _ _ Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __ _ __ (PLEASE PRINT) Stree~-----------------------Suburb/town. _ _ _ _ _ _ _ _ _ _ _ _ Postcode.____ Price: $A5 .00 each (includes postage). Overseas orders add $A 1 .00 per issue for postage. NZ & PNG orders are sent by air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 OR FAX: (02) 982 9553 ~-------------------------------------~ NOVEMBER 1989 89 THE WAY I SEE IT - CTD drawn to my attention by Dr Royden Lake was one in the "IEE Review" (UK) for June 1989: "Smart Tags, The Distributed Memory Revolution", by Peter Hewkin of Scientific Generics. Peter Hewkin defines smart tags as "small devices containing a combination of memory, data processing and communications capabilities. They can communicate without physical contact with purpose-built stations over a range from a few millimetres up to several metres". He goes on to explain that smart tags typically contain semiconductor memories (ROM, EPROM or EEPROM), along with stamped, etched or wound inductors and miniature batteries in the case of active devices. Smart tags range in size, says Peter Hewkin, from that of a brick down to a capsule a few millimetres in diameter. In price, they range from around 30 pounds sterling ($A60) to less than one pound for simple devices holding only a few bits of memory. Certainly, all the transponders (tags?) covered in the accompanying panel respond to an electronic signal and all have a memory function of some kind. Some are userprogramma ble, others are not. Presumably they're all "smart", with some more so than others! According to Peter Hewkin, car manufacturers are also moving away from reliance on a central factory database to the use of smart tags which attach to each individual body shell and ensure that the options nominated by the customer and dealer are available in time and observed at each station in the assembly line. The tag could also be used to record faults which need to be corrected before despatch. In other situations, smart tags can selectively control the movement of individual animals, warn if miners approach too close to dangerous machinery and, in security situations, selectively grant or deny access to particular individuals, depending on how their tag is programmed. More intelligent, interactive tags (cards?) are also in the pipeline for financial transactions, even to the point where transactions would be possible without even removing them from one's wallet. That thought stopped me in my tracks. What a challenge for a new breed of "hacker". Get yourself an interrogator, ride a crowded suburban train and see how many pockets or purses you can pick electronically - without touching the wallet inside! Isn't technology wonderful? ~ Simple program for resistor calculations Do you need to make up non-standard resistor values? This simple program will show you what series or parallel combinations from the E12 range can be used. You simply type in the value you want plus the tolerance. By STEVE PAYOR Ever tried to measure 240V AC on the ohms range of your multimeter and burnt out a string of odd-value resistors? Ever calculated the resistor values for an active filter and found that none of them were anywhere near a standard E12 value? If so, the following BASIC program will help. It will tell you whether the resistor value(s) you 90 SILICON CHIP are seeking can be made up from two E12 values in series or parallel, within a specified tolerance. The sample printout shows 9 possible ways of making up a 1230 ± 1 % resistor. In choosing the most suitable combination, a little thought should be given to the wattage and tolerance of the individual resistors. For example, if this resistor is to be used in an am- meter, you would choose a combination where the two E12 resistors were fairly close in value to maximise the power rating; eg, 3900 1 % in parallel with 1800 1 %. Alternatively, if dissipation is not a problem, as in an active filter, then 1200 1 % in series with 3.30 10% would be another possibility. The program performs a "brute force" search of all possible series and parallel resistor combinations, to see which fall within the required tolerance. This is not a very efficient approach but even on the slowest IBM compatibles, the search only takes 10 seconds. Lines 20 to 100 set up (also by brute force) an array of 7 decades of E12 values, from .01 to 100,000. The desired resistance should be between 1 and 999.9; ie, within the middle 3 decades of this table. This Program Listing 10' PROGRAM TO FIND COMBINATIONS OF TWO E12 RESISTORS IN SERIES OR PARALLEL 20 DATA .01, .012, .015, .018, .022, .027, .033, .039, .047, .056, .068, .082 30 DATA .1, .12, .15, .18, .22, .27, .33, .39, .47, .56, .68, .82 40 DATA l,1.2,1.5,1.8,2.2,2.7,3.3,3.9,4.7,5.6,6.8,8.2 50 DATA 10,12,15,18,22,27,33,39,47,56,68,82 60 DATA 100,120,150,180,220,270,330,390,470,560,680,820 70 DATA 1000,1200,1500,1800,2200,2700,3300,3900,4700,5600,6800,8200 80 DATA 10000,12000,15000,18000,22000,27000,33000,39000,47000,56000,68000,82000 90 DATA 100000 100 DIM E12C85):FOR I=l TO 85:READ El2<I>:NEXT I 110 CLS 120 INPUT"DESIRED RESISTANCE Cl to 999.9) ... ",R:IF R=O THEN END 130 INPUT"WITHIN +/- PERCENT . . . . . . . . . . . . . . . . ",TOL 140 RMIN=R*<l-TOL/100):RMAX=R*(l+TOL/100) 150 PRINT"Looking for a value between";RMIN;"and";RMAX 160' Find nearest <next lowest) El2 value 170 NEAREST=25 180 IF E12CNEAREST+l)<R THEN NEAREST=NEAREST+l:GOTO 180 190' Try all series combinations 2 for decades lower than R 200 FOR I=NEAREST-24 TO NEAREST:FOR J=NEAREST-24 TO I 210 Rl =E12CI)+E12(J):IF Rl<RMIN OR Rl>RMAX THEN 240 220 PRINT El2CI);"and";El2CJ>;"in SERIES, "; 230 PRINT USING"+#.#";(Rl/R-1J*100;:PRINT"%" 240 NEXT J,l 250 • Try all parallel combinations for 2 decades higher than R 260 FOR I=NEAREST+l TO NEAREST+25:FOR J=NEAREST+l TO I 270 Rl=l/Cl/E12(l)tl/E12CJ)):IF Rl<RMIN OR Rl>RMAX THEN 300 280 PRINT El2(l);"and";E12CJJ;"in PARALLEL , "; 290 PRINT USING"+#.#";CR1/R-1)*100;:PRINT"%" 300 NEXT J,I:PRINT"Search complete.":PRINT:GOTO 120 Fig.1 (above): the program is written in GWBASIC but conversion to other BASICs should pose no problem. The program asks you to type in the value you want and the tolerance. Sample Printout DESIRED RESISTANCE Cl to 999.9) ... 123 WITHIN +/- PERCENT . . . . . . . . . . . . . . . . I Looking for a value between 121.77 and 124 . 23 68 and 56 in SERIES, +0.8% 100 and 22 in SERIES, -0.8% 120 and 1.8 in SERIES, -1.0% 120 and 2.2 in SERIES, -0.7% 120 and 2.7 in SERIES, -0.2% 120 and 3.3 in SERIES, +0.2% 120 and 3.9 in SERIES, +0.7% 390 and 180 in PARALLEL, +0.1% 680 and 150 in PARALLEL, -0.1% Search complete. Fig.2 (right): this sample printout ► shows 9 possible ways of making up a 1230 1% resistor. The program calculates both series and parallel combinations. DESIRED RESISTANCE (1 to 999.9) enables the program to search a full two decades above and below the desired value, which is a reasonable range to search if 1 % resistors are to be used. For resistances outside the range of 1 to 999.9, just enter the value in kO or MO etc and pretend that the answers are in the same units. This program was written in GWBASIC, but conversion to other BASICs should not pose any problem. ~ ,:': .) ~. ;:lllA\Dli((}) P'lhr, . - •~1r.~rr: \ . . .. ~-~aililuil•■l~:f:111111 RCS Radio Pty Ltd is the only company which manufactures and sells every PCB £, front panel published in SILICON CHIP, ETI and EA . 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. NOVEMBER1989 91 PT.25: THE PH.BARA IRON ORE RAII..WAYS THE EVOLUTION OF ELECTRIC RAILWAYS Despite what you may think about Australia's federal and state railway systems, the biggest and best railway systems in this country are privately owned. These railways are all in the Pilbara region, in the far north of Western Australia. By BRYAN MAHER Here is a quick quiz on Australian railways: where are the heaviest trains? Or the longest? And who uses the biggest locomotives? Where's the best track? And which rail system moves the most net tonnage of one commodity annually? If you are thinking of the Victorian or NSW systems, you are wrong. The railways in question are all in the Pilbara iron ore region of Western Australia. Western Australia is the biggest state and has the most remote capital city. Many readers may also be surprised to learn that WA has the nation's longest and heaviest trains, the biggest locos and the best track. Imagine a 31,000 tonne train, 2.3km long, with 240 wagons hauled by three head-end diesel electric locomotives, travelling for 8 hours at a steady B0km/h, almost nonstop. Trains of this size run several times every day in the Pilbara. The Pilbara The half million square km Pilbara region lies on the extreme western side of Australia. It is an arid mountainous area extending roughly 750km north to south and 700km east to west. To the east lie 92 SILICON CHIP forbidding regions like the Little Sandy Desert and the dry Lake Disappointment. Northwards, only 60km away, is Marble Bar, claimed as the hottest town in Australia. To the north east lies the Great Sandy Desert. A thousand kilometres to the south are Perth and Kalgoorlie. On the northern limits, the developed sea ports of Dampier and Port Hedland are gateways to interstate and overseas shipping transport. Deep in the Pilbara where its severe climate threatens any traveller are the Hamersley, Chichester, Opthalmia, Kenneth and W alburg ranges. Inside these desolate mountains are huge deposits of copper, tin, asbestos, manganese and iron ore. The iron ore (iron oxide, hematite, Fe2O3) in these ranges is remarkably pure with as much as 64 % iron content (possibly the world's richest metal concentration). While iron is the second most abundant metal on earth, about one tenth of the world's known iron ore deposits are in the Pilbara. The mines A handful of large mining companies have opened up the rugged Pilbara region. Iron ore mines are well established at Paraburdoo, Mt Tom Price, Mt Newman, Mt Whaleback, Pannawonica, Goldsworthy and Shay Gap. Most of their production is shipped to Japan, amounting to about half that country's ore purchases. Other production goes to Australian and European steelworks. New developments continue to open up more areas. Only a mining prospector could think up a name like McCamey's Monster Mine, which commenced iron ore production in March this year (1989), at 2.2 million tonnes per year. The Hancock Prospecting Company has arrangements to supply iron ore to Czechoslovakia and Romania, with expansion contracts tipped to involve Poland and all Eastern Europe. These countries prefer the Pilbara's very pure iron ore to the previous low grade Russian ores. The BHP company plans to supp- ly the Newcastle and Pt Kembla steelworks with ore from their new Marillana Creek mine. Supplies from this mine will replace the present Koolan Island ore mine when it cuts out in three years time. The brand new Channar mine, a development of Hamersley Iron with the Chinese government, will supply up to 10 million tonnes of rich ore to China every year - this despite China already having the world's second largest iron ore reserves (their ore is of much lower purity than ours). Railway companies As always happens in today's mechanised world, large mines beget large railways. Three private railway systems were built and operated by the three major mining companies. All continuously haul the high grade ore to the seaports. The companies, Cliff Robe River Iron Associates (CRRIA), Hamersley Iron (HI) and Mount Newman MOST IRON ORE TRAINS in the Pilbara use three locos at the head-end and three at the end. A typical train has 240 wagons and a gross weight of over 30-,000 tonnes. The lead loco here is a rebuilt Alco model rated at 2.686MW. Railroad between them have over 1300km of heavy standard gauge track. Any one of the three companies' railways can claim many Australian records. The Hamersley system has the capacity to shift 56 million tonnes of ore a year on one single track. Though perhaps not an Australian record for total system capability, it must go close to a record for what one pair of steel rails can carry. Harnersley Iron Hamersley Iron Pty Ltd is the largest of the companies in the Pilbara, producing half the state's total iron ore output. This is a big contribution to Australia's total production of 108 million tonnes a year. Everything needed at the mines, from fuel or oils to machines, must be transported nearly 400km from the seaport at Dampier. And every tonne of iron ore produced has to be carried the same distance to the coast. The Hamersley reserves contain 8 billion tonnes of the best iron ore. There are two mine sites, one at Mt Tom Price (one of Australia's largest known ore deposits) and the other at Paraburdoo. At present capacity, these two mines combine to produce 46 million tonnes a year. Hamersley Iron has also built a plant to make iron ore pellets for the export market. Harnersley route Hamersley Iron's one and only main line is nearly all single track. On the most difficult section, Paraburdoo to Mt Tom Price, loaded trains face a steady climb, the ruling gradient being a consistent NOVEMBER 1989 93 However, a quick calculation of the power needed to haul 24,00ot to 30,000t of train [plus 1200t of locos) up that modest gradient shows that over 16MW (22,000hp) is required! When the train gets to Mt Tom Price, the tail end locos are uncoupled and the train proceeds with only the three head end locomotives over the next 288km run to Dampier. On this section the grade is gently downhill except for an 18km-long uphill gradient of 0.3% about 80km from Dampier. Returning empty trains from Dampier face an uphill climb over all the 288km to Mt Tom Price (740m above sea level) except for the 18km downhill section, 6 7km out. A total of 56km of dual tracks have been built on three sections. This allows full and empty trains to cross without stopping. Passing loops allow trains to pass each other on the remaining single track sections. In general, unloaded trains stop and wait for loaded trains to pass. This saves considerable time and fuel by avoiding unnecessary acceleration of heavily loaded trains. More than eight loaded trains per day make the trip to the seaboard from the mines, five from Mt Tom Price and three from the newer Paraburdoo loading points. At 75km out from Dampier the Hamersley line crosses over the CRRIA tracks which run from the Pannawonica mines to the coast. Mt Newman Mining THE PILBARA RAILWAY TRACKS are the heaviest and best maintained in Australia. They have to be, since they carry such enormous quantities of ore. Hamersley's tracks have carried as much as 52 million tonnes of ore in one year. 0.42 % over most of the 98km route. Three head-end diesel electric locomotives haul the train of 180, 210 or 240 wagons with three banker locomotives pushing at the rear. These trains are so long that head and tail drivers rarely see each other. As the head locos start, the driver at the front tells the driver in the tail locomotives, by radio, to apply power. This radio contact continually advises which controller notch is to be used in ac94 SILICON CHIP celerating to full power (8th notch), steady running, power down and braking. In the event of an emergency brake application by the head end driver, the reduction of air pressure in the train brakeline cuts the power in the tail end locos. Now you may ask: why six locomotives on a grade of only 0.42 % ? It doesn't sound much of a grade does it? After all, the grade on the Blue Mountains is 3 % to 3.3%! The Mt Newman Mining company was formed to win ore from the Opthalmia ranges, principally from the Whaleback-Newman mountain group which contains one of the world's largest concentrations of hematite. Work began in 1967 to prepare the minesite, loading facilities and heavy standard gauge railway. The system was opened for production two years later. Another two years on and the production rate exceeded 12 million tonnes a year, shipped to steel works in Newcastle, Pt Kembla. Europe and Japan. This new industry gave rise to a . new town 8km from the port to people and the structure of the industry. From Paraburdoo mine to the nearest city, Perth, is almost 2000km by rail and sea, and only about 300km shorter by road. In this (usually) dry, bleached, dusty atmosphere, locomotives and rolling stock need constant maintenance and repair. This means that the mining companies must be self-sufficient in spares, heavy workshops with engineering support, design, computing and reference facilities. The infrastructure and recreational amenities for all staff must also be provided and maintained. Environment ALL COMPANY-OWNED LOCOMOTIVES are maintained in tip top condition. They are specified for heavy duty work in very hot and dusty conditions and their motors are required to deliver full power for many hours at a time. These are EMO SD50S locos rated at 2.7MW. house staff of the railway and loader. worthy. This railway also extends to Shay Gap. Mt Newman route Robe River The Mt Newman railway runs direct from the mines 426km northwards to the ship-loading facility at Port Hedland on the Indian Ocean. The railway hauls its iron ore trains over typical Pilbara country. While stiflingly hot and bone dry most of the summer, during a cyclone the line is beset by destructive gales and torrential rain, with rivers in roaring floods. On the way this line crosses the Opthalmia and Chichester ranges, the Yule River and three of its tributaries. A railway also runs eastwards from Port Hedland, crossing the De Gray River to the mines at Golds- Cliffs Robe River Iron Associates opened its ore mine at Pannawonica in the western Pilbara, just south of the Robe river. Their railway, also of heavy standard gauge, runs northeast 200km to the port at Wickham on Cape Lambert. The route crosses the Robe and Fostescue rivers, on through the Mt Leal .National Park, to cross the Hamersley line on an overbridge 75km southeast of Dampier. The arduous Pilbara climate is taxing on humans and machines alike. Most of the year the rainfall is almost nil, with bursts of torrential downpours, sometimes 100mm/ hour during cyclones, bringing the yearly average to 330mm/year. Winds of up to 210km/hr are experienced for sustained periods in the cyclone season. Added to the tropical conditions in summer is the bitter cold in the mountainous regions in winter. The Mt Tom Price mine is 750 metres above sea level while Mt Newman is at 1055 metres. How do you keep trains running continuously when temperatures range from zero in winter to 74 ° C in summer? Can locomotive diesel engines and electric traction motors be expected to cope? Of course. Isolation All three railroad companies and their employees feel the great outback isolation. This affects both Large locomotives The three railway companies all use modern, very powerful loco- THE DIESEL ELECTRIC LOCOMOTIVES used in the Pilbara by the iron ore mining companies are much bigger and heavier than diesel electrics used elsewhere in Australia. When originally delivered, the 2.05MW Alco C-628 loco was the most powerful diesel electric in Australia. NOVEMBER 1989 95 ◄ ALL THE PILBARA RAILWAY companies have excellent workshop facilities for their locomotives. This is Hamerley's workshop near Dampier. motives based on American machines. However, the hot working conditions and the long runs at full power have dictated many improvements to the original designs. At various times, Hamersley Iron has used Alco class C628, C636 and M636, General Electric C36/7, and EMD (General Motors) SD50 Super series diesel electric locomotives. Five Alco C628 Co-Co diesel electric locomotives, each of 2.05MW (2750hp) and weighing 178 tonnes, were built in the USA and shipped to Hamersley Iron railway in 1965. At that time, these were the heaviest and most powerful diesel electrics ever exported from the United States. With a length of 21.3 metres, a width of 3.1 metres and a height of 4. 7 metres, these locomotives were (and still are) much larger and heavier than could be run on any of the Government-owned railway system in Australia. Originally they were used singly hauling ore trains, then in multiple as production of ore increased and longer trains were required. All C628s were decommissioned in 1981/82 as newer locomotives like the more powerful Alco C636 became available. In 1968, Alco of USA licensed the A.E. Goodwin company of Auburn, NSW to build locos using Alco designs. Goodwin subsequently manufactured Alco C636 locomotives for all three Pilbara iron ore lines. Developing 2.460MW (3298hp) at the traction motors, these C636 class locos could haul even longer trains than the C628s. In 1975, in the winter months, the Mt Newman railway created an Australian record with a train of 230 ore wagons hauled by five head-end C636 class locos. The train had a gross weight of 31,000 tonnes and was 2.3km long. Trains of this size have since become common on all three Pilbara railways. However, this has only been made possible during the summer months by upgrading the ALL THREE MINING COMPANIES in the Pilbara use very powerful locos based on American designs. Two Alco C-636 locos are shown here but longer trains use three locos at the front and another three at the rear. engines and the cooling systems. Loco rebuilds The Hamersley Alco C636 class locos have now been considerably upgraded so that the diesel engine, traction motors and air conditioned driver's cab are more suitable for the hot, dusty climate. Many of these new Alco models were produced by Comeng in Granville, NSW and now feature extended range dynamic braking and Westinghouse air brakes. During the upgrade, many improvements were made to increase loco performance in the high desert temper- atures. These included increased oil and water pump rates, improved air filters and radiators, and modified engines. To allow consistent speed on the 4.5° curves in hilly sections, flange lubricators were fitted to the locomotives and the bogie middle axles were given more lateral play. These modifications, along with a better steel specification for the loco wheels, are expected to prolong wheel life to 500,000km. Diesel engine The Alco V16 4-stroke engines were upgraded using an improved NOVEMBER 1989 97 ,--------------, : AMATEUR RADIO I Hobbyists communicating world wide using state-of-the-art electronics. Are you a radio amateur but not a member of the WIA? Do you know what you are missing? Do you like using VHF/ UHF repeaters? Enjoy working DX? Want to preserve your ban s? THIS IS HAMERSLEY IRON'S fines loader at Mt Tom Price. The ore is loaded into the wagons from a slewing conveyor at about 5000 tonnes per hour for shipment to the port of Dampier. Join the WIA - the oldest and most experienced radio society in the world - always at the forefront of radio communications for hobbyists. Receive AMATEUR RADIO, the monthly magazine for members of the WIA, full of news of DX, clubs, satellites, technical articles and lots more. I • • • • • • I Other WIA services include: A wor1d wide QSL card service Weekly news broadcasts Classes for all grades of amateur licences Correspondence lessons available Meetings, contests, field days Representation for radio amateurs at Government level Learn more about the WIA and Amateur Radio Forward this coupon, or write to: WIA EXECUTIVE OFFICE P.O. BOX300 CAULFIELD SOUTH VICTORIA 3162 Hawthorn Road Registered address. Caulfield North, 316 Please send a WIA information package to: NAME: ............................................................ ADDRESS: ..................................................... . ................................... POSTCODE ................. ~-------------~ E003S1 98 SILICON CHIP turbocharger, redesigned pistons for more efficient combustion, and improved valve locations. At 1100rpm, the engine produces 2.909MW (3900hp) to drive the alternator. Allowing for electrical and fan losses, 2.686MW (3600hp) of electrical power is available to drive the traction motors, each of which is rated at 448kW. The complete locomotive weighs 192 tonnes. Load factors You may imagine that the engine and traction motors have an easy run with a loaded train on the downhill and flat sections but such is not the case. Any train of about 200 wagons has 1600 wheels, each causing some friction on curves. Then there are acceleration forces to provide, not forgetting the continuous uphill climb for 98km out of Paraburdoo. These factors combine to require full engine power for 98 % of the time on the journey from Paraburdoo to Mr Tom Price, and 3 7 % of the time on the remainder of the journey to Dampier. Empty trains use full power for 73 % of the time over the whole 288km from the seaport to Mt Tom Price. These ratios are much higher than encountered on other rail- roads, either in Australia or the USA. It means that a 1-hour power rating for the traction motors is meaningless. Motors must be designed to deliver full power continuously, a requirement not envisaged anywhere but on the Pilbara lines. All locos have wheel slip indicators, hump control and automatic sanding. The latest units are equipped for electronic control and feature digital recording of engine parameters. The driver can control the locomotives to minimise the concertina action of a long train in starting. On the latest units the driver can also set the loco control parameters for any one of the following requirements: (a) maximum traffic throughput; (b) minimum fuel usage; and (c) minimum system cost. Next month we'll look in more detail at these most efficient of Australian railways and see how they are helping to maximise our export effort. Acknowledgement Our thanks to the Hamersley Iron and Mt Newman railways, and to Comeng of Granville, NSW, for data, photos, drawings and permission to publish. [§;I I PRODUCT SHOWCASE I Frequency response is quoted as 5Hz to 1MHz ± 10% or 20Hz to 20kHz ± 3 % and measuring accuracy is ± 3 % of full scale deflection. A handy feature of the millivoltmeter is the provision of a 600 ohm impedance output, from the binding post terminals, which delivers 1 volt AC for full scale deflection on any range. It can ther.efore be used as a sensitive Protohoard for IBM XT and AT computers from Geoff Wood Electronics. Phone (02) 428 4111. Fax (02) 428 5198. Now here's a nifty product - a prototyping board which installs right into a standard card position in an XT, AT or compatible computer. It will accommodate up to 24 14-pin !Cs and has all the IBM signals brought out to pin sockets on the board. A DB-25 female socket is provided for external connections. Neat, huh? Priced at $78.55, it is available AC millivoltmeter from Jaycar Made by Lodestar, the MV-3002 AC Millivoltmeter has 12 measuring ranges from 100 volts to 300 microvolts (fsd) and an input impedance of 10 megohms with input capacitance of less than 50 picofarads. The input socket is a standard BNC type. Deluxe frames and cabinets for rack mounting equipment Altronics has a range of rack frames and cabinets which will handsomely mount standard 19-inch equipment. The rack frames are made of a specially tooled aluminium extrusion which locks into ABS plastic corner connectors to give a very strong assembly. To turn a rack frame into a rack cabinet, you add aluminium side pieces which are finished in a very hard and durable powder coat enamel in "electron grey blue" - a light sky blue colour. We unwittingly put the hardness of the enamel finish to a test by dropping one of Altronics' 7V A transformers onto one of the side panels. It made a loud crash l;>ut when we looked for a dint or paint chip we could find none. The racks and cabinets are freighted in flat packs and are quite easy to assemble. For further information, contact Altronics Distributors Pty Ltd, 174 Roe Street, Perth, WA 6000. Phone (09) 328 2199 or toll free (008) 999 007. wideband audio preamplifier for waveform monitoring. The unit is mains powered. The mirror-backed meter movement has four scales: 1V and 3.16V plus dB and dBm ranges. Each of the voltage ranges has dB markings. The unit can be used for measuring signals and noise down to below - 80dB below 1V RMS. As with most test equipment, the MV-3002 comes with a circuit diagram which is incorporated into the instruction manual. The Lodestar MV-3002 is available from all Jaycar Electronics stores at $199 including sales tax. Pin and jumper wires for prototyping If you are wiring up proto boards, making up little jumper wires can be a pain. These little jumper wires are just the ticket for the job - they are fitted with pins NOVEMBER 1989 99 . . ,, . :, ~ ·..· 1·.-.·..-.• . .· . ,~-· ff Mini vacuum cleaner for delicate dusting Now here is the ideal tool for dusting and cleaning delicate or precision equipment. It is ideal for cleaning model train layouts, vacuuming tiny PC boards or electronic equipment which is hard to get at, and for cleaning camera equipment, computer keyboards and so on. A particularly useful feature at each end and are sleeved to make them easy to handle. They are also available with spade lugs at one end so you can use them for supply and output connections. Get them at Geoff Wood Electronics, 229 Burns Bay Road, Lane Cove West, NSW 2066. Phone (02) 428 4111. Fax (02) 428 5198. Automatic printer sharer There are plenty of printer sharers around which will allow one printer to be driven by up to four computers but they all need to 100 SILICON CHIP . . of the cleaner is that it has a cleaning head with a filter in it. That way, if you are vacuuming a model layout and some part is dislodged, it won't be sucked right through the cleaner. It is powered by 4 AA-size cells and you can use it as a blower too. Priced at $14.95, it is available from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone(02)2671385.Fax(02)261 The PEPsharer costs $339 including sales tax. For further information contact Banksia Information Technology (Australia) Pty Ltd, 205/83 Longueville Road, Lane Cove, NSW 2066. Phone (02) 418 6033. Fax (02) 428 5460. PC Breeze: a low cost CAD package .8905. be manually switched to the right computer to do the job. This PEPsharer from Banksia Information Technology does the job automatically. You plug in up to four Centronics cables from separate computers and the sole printer is connected via a standard female DB-25 socket. Each of the parallel printer outputs is then polled continuously for activity. Any active output is then automatically connected to the printer. All other outputs are locked out until the task in hand is finished. Polling then recommences until the next printing task. The unit is powered from an external plugpack and is meant to be wall-mounted so it neatly accommodates the four cable inputs. That explains its unobtrusive appearance. A LED indicator associated with each printer input shows which one is active at the time. Well supported CAD packages with a low entry cost are fairly rare so this package from Kepic Pty Ltd is welcome. Called PC Breeze, it is written for the IBM XT or AT although it would perform much faster on an AT or compatible. Minimum equipment requirements are 448K of memory and a graphics board of CGA, HGC, EGA or VGA standard. For printed output, a plotter which is DMPL or HPGL compatible or an Epson FX/LQ dot matrix printer is required. Alternatively, the output can be produced on a Postscript compatible device such as the Apple Laserwriter or a Linotronics 300 typesetter. Getting the best from such a package takes quite a while but the supporting literature provided with PC Breeze is comprehensive and well written. Ultimately, the results you get will depend on the library of symbols you create. In the hands of a practised user, PC Breeze delivers the goods. At just $295 including freight anywhere in Australia, it is very well priced. For further information, contact Kepic Pty Ltd, 4 Steinbeck Place, Spearwood, WA 6163 . Phone (09) 418 5512. Dealer enquiries are welcome. IC pin strips for custom sockets A big problem with the great range of ICs in use is that they come in just about every size from six pins and up and with packages of different widths . . No one wants to keep sockets for all these as you might not use some types for ages. A solution is to use these IV pin socket strips from Geoff Wood Electronics. They can be cut to any length and they make up the equivalent of high grade machine sockets. A single 36-pin strip is available for $6.95 - that's not bad considering it will make up into two 18 pin machine sockets or any other combination with 36 pins. Also available from Geoff Wood Electronics are the wire wrap pin strips pictured. One 36 pin strip is $2. They are more elegant than the usual PC pins. Geoff Wood Electronics are at 229 Burns Bay Road, Lane Cove West, NSW 2066. Phone (02) 428 4111. Fax (02) 428 5198. Balanced line driver for audio equipment If you need to have long audio lines then you need a balanced line driver such as the TA-1010. This will prevent hum, high frequency degradation and spurious noise pickup. Just one of a series of audio modules for audio installations, the New UHF handheld transceiver Recently released, along with the IC-2SA, the UHF learn IC-4SA covers the 430-440MHz section of the 70cm amateur band. Packed into a very small case is a transceiver with exceptional capabilities. With a 13.8 volt DC supply it will deliver around 5 watts RF output or around 500 milliwatts if you warit to conserve the batteries. Naturally, it has its own rechargeable nickel cadmium battery pack (from 1 lOmA.h to l000mA.h) as well as being able to operate on an external DC supply. With no less than 48 memories, you can just about make it talk! It has full scanning facilities and you can define scanning limits, memory scanning and memory skipping. It has Set and Private modes which prevent casual users tampering with your critical settings. The IC-4SA also has a programmable clock with timer functions so TA-1010 has a locally made balanced line transformer driven by an integrated circuit amplifier, both mounted on a printed circuit board measuring 75 x 45mm. The board needs a + 24V DC input to run. For further information on their range contact the manufacturer, Harbuch Electronics Pty Ltd, 90 George Street, Hornsby, NSW 2077. Phone (02) 476 5854. I. you can turn the transceiver on at preset times, and it has dial selection for changing frequency in 1MHz, lO0kHz or 10kHz steps. All this is packed into an aluminium diecast case measuring 103mm high, 49mm wide, 33mm deep and weighing just 270 grams (including the 1 l0mA.h battery pack). It is supplied complete with plugpack charger and flexible antenna. For further information, contact your nearest learn retailer. NOVEMBER 1989 101 Mini stereo amplifier for Walkmans W alkman style radios and tape players are fine when you are on the move or travelling in public transport but when you are at home it is nice to listen without the headphones. That is what this little stereo amplifier is intended for. Just hook it up to your W alkman, connect a pair of 80 speakers and then sit back and enjoy the music. It is not high power or hifi but that is not what you'd expect from such a tiny unit. It runs from 4 AA-size 1.5V cells and puts out a claimed 500 milliwatts per channel. Price? Just $29.95 from Jaycar Electronics. Silicon surge suppressors This range of silicon surge suppressors normally have a high impedance (open circuit) but drop to a low impedance if a high voltage transient occurs. They have sharp breakdown voltages, fast response times and a high surge capability. They are available with breakdown voltage ratings from 6.8V to 440V and in four electrical configurations. New company has XT motherboard A new company has recently started up to provide a comprehensive range of XT, AT and 386 computer boards. Called Board Solutions, the people concerned have over 10 years experience in the mail order industry and have lined up some very attractive deals to kick start the operation. Included among these is a turbo XT motherboard which runs at either 10MHz or 4.77MHz (switchable) and has a capacity for up to 1 megabyte of RAM. The price for this board, without RAM, is an incredible $129. Just how low can you go? Anyway, if your old IBM PC com102 SILICON CHIP ting and are washable and submersible for ultrasonic cleaning. For further information, contact Siemens Ltd, Communications Equipment Department, 544 Church Street, Richmond, Vic 3121 . Phone (03) 420 7308. Cushion handle side cutters CUTTER For further information, contact Multicorp Pty Ltd, 35 Wells Street, Redfern, NSW 2016. Phone (02) 698 5238. patible is getting long in the tooth, why not consider souping it up with this new XT motherboard? For further information, contact Board Solutions, PO Box 1120, Lane Cove, NSW 2066. Phone (02) 906 5696. Fax (02) 906 5222. Miniature relays from Siemens Siemens has extended their range of miniature relays with the release of the MR Pl which is available in both bistable and monostable versions. These have very low power requirements of 65 milliwatts for the mono version and 30 milliwatts for the bistable type. They are suitable for surface moun- These handy side cutters from Scope are spring loaded and have very comfortable cushion handles for ease of use and less handle fatigue when they are used for a protracted period. Heavy duty and long life cutters are included in the range. As well, there are safety models which have a clip designed to hold cut leads to stop them flying about. For further information, contact Scope Laboratories, PO Box 63, Niddrie, Vic 3042. Phone (03) 338 1566. POLYSTYRENE CAPACITORS Made here in Australia? Made Special to Type? Qwerty keyboard from Mayer Krieg Need a Qwerty keyboard for a computer project? This German made unit from Mayer Krieg & Co could be just what you are looking for. It is a light action membrane keyboard with flex- ible circuit outputs which are terminated in two 19-way board sockets (which are supplied). Price is $35 plus sales tax where applicable. For further information contact Mayer Krieg & Co, 50 May Street, Unley, SA 5061. Phone (08) 373 0444. Fax (08) 272 2492. Giant tower case for big systems If you have a really big computer system in mind, you can now obtain a full-size tower case which will take a 386 or 286 motherboard and has provision for up to six halfheight disc drives or a mixture of full height and half height drives. It can be supplied with or without a 220 watt power supply which will cope with mains variations from 180 to 260 volts AC and has a typical efficiency of 68%. Its rated outputs are + 5V at up to 23 amps, + 12V at up to 9 amps, and two - 5V rails at 0.5 amps. The supply also comes with full over-voltage and short circuit protection. Other facilities fitted to the tower case include turbo drive, disc drive and power LEDs, power and key switches, and an outlet for a front or rear mounted keyboard connector. Dimensions are 600mm high, 420mm deep and 190mm wide. Price with the power supply fitted is $492 and $299 without. The case comes with a 14-day money Polystryrene Capacitors - 1 0pF to 1mF Voltage Range 63VDCW to 10,000 VDCW Tolerance - 0.25% to 10% Allied Capacitors Australia manufactures capacitors to the specification of the customers using high quality, imported polystyrene and aluminium foil with a tolerance of 1 micron. Our capacitors are manufactured to the system of Total Quality Control. We can provide Just In Time delivery if required, together with a Certificate of Conformance if requested . Specific values between 1 0pF and . 1uF are no more expensive than standard value components. You can now design circuits to use a single capacitor rather than a number in parallel or series to achieve a desired value. Personalised labelling is available at no extra cost. Your component code or name can be built into the capacitor. Minimum runs of only 25 allow you to specify a particular value for a prototype run. Delivery lead time for short runs is 3 to 4 working days, and for longer runs is less than 2 weeks. We are also able to produce capacitor styles for applications such as dual mount, end filled and mini style capacitors. INTERESTED? Call us now on: (02) 938 4690 back guarantee and a 3-month warranty. For further information, contact Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 906 6666. Fax (02) 906 5222. ALLIED CAPACITORS AUSTRALIA PO Box 740 Brookvale, NSW 2100 NOVEMBER1989 103 "NO BRAND" DISKS Now you can buy absolute top quality disks that are also the cheapest In Australia! They even come with a lifetime warranty, which Indicates the quality of these disks. So why pay 2·3 times the price for the same quality? Packs of 10, DIS DID without boxes, or brand name, just their whltepaper jacket, and Index label. (5 114" disks includes write protects) (ALL PRICES PER 10 DISKS) 51 /4" 2S/2D "NO BRAND" DISKS 10+ DISKS 100+ DISKS 1,000+ DISKS $6.00 $5.75 $5.50 DISK BOXES COPY HOLDERS CASES 5 1/4" HIGH DENSITY DISKS (DOUBLE SIDED) 100+ DISKS 10+ DISKS 1,000+ DISKS $21 $22 $23 3 1/2" 2S/2D "NO BRAND" DISKS $21 DISK STORAGE UNITS • 80 x 3 112" • Lockable C16038 .... ..... .........$16.95 3 1/2" 2S/HD "NO BRAND" DISKS 100+ DISKS 10+ DISKS 1,000+ DISKS $53 $59 $65 • 40 x 3 112 ... Lockable C16035 ..................$14.95 • 40 x 3 112 .. "Eclipse" C16040 ....................$8.99 Suitable for IBM, PS/2, Macihtosh, Atari, etc. • 120 x 3112 ... Lockable COPY HOLDER (YU-H32) C16025 ..................$14.95 • Adjustable arms allows easy positioning • Copy area 9 112" x 11" • Sliding line guide • Clamp mounting • 100 x 5114 ""Eclipse" C21062 .................. $39.95 C16039 ..................$21.95 • 50 x 5 114 ... Lockable COMPUTER CASES YOU WOULD'NT BELIEVE THE PRICE • Limited stock so get in quick • IBM' PC/ XT, Apple'•ll/1le Compatible Computer Case ..................... ONLY $50 C16042 ....................$9.95 • 100 x 5114 ... Lockable C16020 ..................$15.95 • 120 x 5 114 ". Lockable C16028.................. $19.95 KEYBOARD ACCESSORIES VERBATIM DISKS DESCRIPTION (ALL PRICES PER BOX OF 10 DISKS) 1·9 BOXES 3 1/2" 2S/2D ...............$37.95 3 1/2" 2S/HD .............. $78.95 51/4" 1S/2D............... $21.95 5 1/4" 2S/2D ...............$25.95 5 1/4" 2S/4D ...............$33.95 5 1/4" 2S/HD ..............$33.95 (Each pack of 10 consists of 2 Red, Blue, Yellow, G,een & Orange Disks) $39.95 $26.95 $35.50 Teflon* Coated (ALL PRICES PER BOX OF 10 DISKS) 1·9 X11093 ....................... $99 COPY HOLDER (YU-H33) • Copy area 9112" x 11" • Sliding llne guide • Flat metal base C21060 .................. $39.95 10+ $27.95 $35.95 IBM* XT COMPATIBLE CASE WITH AT* STYLING Features security key switch, 8 slots, and mounting accessories Size: 490(W) x 145(H) x 400(0) KEYBOARD SLIDEAWAY MOUSE Slide your keyboard neatly away when not in use. Gives you more desk space. Securely holds any keyboard, wide or narrow. MICROSOFT• COMPATIBLE P.C ACCESSORIES Stores keyboard under the PC or monitor conveniently out of the way. Fits PC/AT keyboard or 2 3/4"(H) X 221I4"(W) X 91/2"(0) •YU· E21B • Auto-selection and auto• transfer between mouse system PC mouse mode and Microsoft serlal·mouse mode • Microsoft Serial Mouse and Mouse System compatible • Super high tracking speed: 600mmlsec • Super high resolution: 200 DPI (0.12mmldot) • Silicon rubber coated ball • Optical rotary encoder A working bench for your Mouse. •High quality ABS plastic and antl•static rubberised top •Stationary holder •Includes pull-out shelf for Mouse •Dimensions: 280 x 260 x 25mm • Fits over keyboard C21081 ..................$84. 75 X19955 .................. $94.95 C21080 ................. $24.95 C21083 ..................$64.95 KEYBOARD STORAGE DRAWER VERBATIM DATALIFE PLUS 5 1/4" DS/DD............. $29.95 5 1/4" DS/DD.............$38.95 Small footprint. Features security key switch, 8 slots and mounting accessories Size: 360(W) x175(H) x405(D)mm 10+ BOXES $34.95 $74.95 $19.95 $23.95 $31.95 $31.95 COLOURED VERBATIM DISKS 3 1/2" 2S/2D ............... $41.95 5 1/4" 2S/2D ...............$28.95 5 1/4'' 2S/HD ..............$37.50 BABY AT* STYLE COMPUTER CASING X11091 .......................$99 QUICK MOUSE MAGIC STAGE COMPUTERS UPGRADE NOW! AMAZING Y.E DATA 3.5" 1.44/ 720/ 360 DRIVE ,4. BABY AT* COMPATIBLE COMPUTER! 2M/B RAM $2,195 • Final assembling and testing In Australia! • 4 M/Byte Main Board, 2 M/Byte fitted • Switchable 8/10/12 MHz • 1.2 M/Byte Floppy Disk Drive •80286CPU • Colour Graphics Display Card •8Slots • Floppy & Hard Disk Controller • Printer Card and RS232 • Keyboard • 200W Power Supply • Manual • 6 Months Warranty • Size: 360(W) x 175(H) x 405{D)mm With 20 M/Byte Hard Dlsk.$2, 195 With 40 M/Byte V.C. H.D.... $2,395 With 80 M/Byte Hard Disk .. CALL AC ADAPTOR • output: 6V 300 mA M19008.................$8.95 1/0 ACCESSORIES If you have two or four compatible devices that need to share a third or fifth, then these inexpensive data transfer switches will save you the time and hassle of constantly changing cables and leads around. • 2 Way RS232 X19125 ....................... $79 • 2 Way Centronics X19130 ....................... $69 • 4 Way Centronics X19135 ....................... $79 • RS232 2 X 2 Auto Switch X19140 ....................... $79 • Centronics 2 x 2 Auto Switch 640K RAM TURBO COMPATIBLE COMPUTER 2 x 360K Disk Drives, Multi• function Card, Colour Graphics, Disk Controller, 1 Serial, Parallel Port (Clock) .................... $1,050 WITH 20 M/BYTE HARD DISK: & single 360K Disk Drive ..$1,450 & dual 360K Disk Drives ... $1,600 WITH 40 M/BYTE HARD DISK: & single 360K H.D...... $1,n5 & dual 360K V.C. H.D ......... $1,925 v.c. :; .~ ) . -.4. .... . ,,.... ;•., ,...., , ;• CARDS X19145 ....................... $79 POCKET AUTO AB SWITCHES • Pocket size, auto-scanning • Allows 2 PCs IQ share one Printer • Serial model: MS-201 - Hostpowered X19150 .................. $79.95 POCKET AUTO AB SWITCHES • Pocket size, auto-scanning • Allows 2 PC's to share one Printer • Parallel model : MP-201 Protocol transparent X19155 .................. $89.95 CENTRONICS PLUG • 36 Way Centronlcs Plug to 36 Way Centronics Plug P19013 ..................$29.95 CL21 COMPUTER LEAD • 25 pin D Plug to 25 pin D plug • all pins wired straight through (removable terminals) • Length 1.5metres. P19007 .................. $36.95 • 51 /4" Mounting bracket • Power supply adapter • Floppy Disk controller card which controls 1.44/ 720/ 360/ drives • Cable adapter Complete instructions to install a 3.5" drive in your existing computer. Enjoy the higher ' density and easy handling of 3.5" Floppy diskettes. . ..... ....................... ONLY $355 :r;1:e DATA TRANSFER SWITCHES X19120 ....................... $59 Check these features and our prices. We're sure you'll agree they're exceptional value for money! • Final assembling and testing In Australia! • Fast TURBO Motherboard • AT' style keyboard • Tested by us for 24 hours prior to delivery! • 8 Slot motherboard • 12 months warranty! • 150W power supply ·r). ~ • 4 Way RS232 IBM* XT* 640K RAM TURBO COMPATIBLE COMPUTER ~l:m'III" 386SX 16MHz MOTHERBOARD • Processor: 80386SX-16MHz (0/1 wait state) • Co-processor:80387SX-16 (optional) • CHIPS & TECH NEAT chipsets • (SMT) Surface Mount Technology tor chipsets & CPU • Supports up to 2MB on board, (Sixteen 44256 and Eight 41256 sockets) • Three 8 BIT slots • Five 16 BIT slots • Memory Expansion Slot • Optional 2-8MB memory card • Supports LOTUS-INTELMICROSOFT (LIM) Expanded Memory Spee. (EMS) version 4.0 • Supports Page Interleave Mode using 100NS DRAM • BIOS: AMI or PHOENIX • Turbo Light and Hardware Reset connector • Keyboard or Hardware Reset connector • Power Good Signal on board • Baby size main board •Without Ram MULTI-CHIP PROGRAMMER CARD • Model LP-A1 • Module: Multi-Chip • Good for programming • SRAM TEST 6116-62256 • EPROM 8 BIT ICs • 2716-27512, 2716A-27512A, 27012-27012, 27C16-27C512, 2804-5,8064, 28256-52B13 • EPROM 16 BIT ICs • 271024, 27102, 27210 • MCS-48 series of ICs • 8741-8750, 8748-8748H, 8749-8749H • MCS-51 series ol lCs. 8751-8752 X18020 ..................... $575 NEW MIDI CARD MELBOURNE : 48 A'Beckett St Phone: (03) 663 6151 NORTHCOTE: 425 High St. Phone: (03) 489 8866 MAIL ORDER& CORRESPONDENCE : P.O. Box 620, CLAYTON 3168 Order Hotline : 008 33 5757 (Toll free , strictly orders only) Inquiries: (03) 543 7877 Telex: AA 151938 Fax : (03) 543 2648 ORDER HOTLINE 286 NEAT MOTHERBOARD 008 33 5757 (TOLL FREE) STRICTLY ORDERS ONLY MIDI INTERFACE CARD - 05/401 • 20MHz The MIDI DS-401 Card is the PC standard MIDI interface that runs most popular PC music programs tor sequencing, recording, composing, music printing, patch editing, music instruction and many other applications. • Run all programs designed for the Roland MPU-401 architecture • Socketed EPROM for easy user replacement • 1/3 length (short) card will lit in any computer accepting standard expansion card, Including laptops • Including "Y" cable, external connector box to transport Is unnecessary X18092 ..................... $895 X18164 ..................... $245 X18090 ..................... $700 Please quote this advertisement for the prices listed for this month. SYDNEY: 74 Parramatta Rd. Stanmore 2048 Phone: (02) 519 3134 Fax: (02) 519 3868 All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE 56 Renver Road, Clayton. Phone :(03) 543 2166 (3 lines) Fax: (03) 543 2648 X18094 ..................... $900 • Processor: 80286-12, -16MHz or -20MHz (0/1 wait state) • Co-processor: 80287 (optional) • CHIPS & TECH NEAT chlpsets • 1-4MB dual RAM socket • 1-4MB module RAM socket on board • 640KB-384KB memory relocation • Three 8 BIT expansion slots • Five 16 BIT expansion slots • Memory expansion to 8MB • Supports EMS 4.0 • Page Interleave Technology • BIOS: AMI or PHOENIX • Hardware and keyboard switchable Clock Speed • LED speed display • Power Good Signal on board • Baby size main board • 16MHz ROD IRVING ELECTRONICS ----- LOCAL ORDEAS & INQUIRES (03) 543 7877 POSTAGE RATES : $1 - $9.99 ··············· ··········$2.00 $10 - $24.99 ·····················$3.00 $25 - $49.99 ·····················$4.00 $50 - $99.99 ·····················$5.00 $100 + ..............................$7.50 The above postage rates are for basic postage only. Road Freight, bulky and fragile items will be charged at different rates. Errors and omissions excepted. Prices and specifications subject to change. IBM·, PC" . xr·, Ar . are reg 1Stered trademarks of Intern at io nal Busin ess Machi nes . • Apple is a re g istered tr ade mar k. Tef lon · i s a reg istered tr ad e ma rk ol Dupont. · o enontes re g istered trademarks of their respective owners. Rechargeable batteries Closed circuit TV system Captain Communications has a complete closed circuit TV system which would be ideal for security monitoring in business or for watching over the home pool when children are in it. It comes with a black & white camera and a compact 15cm diagonal monitor. The camera is rugged and weatherproof and comes with swivel brackets for easy mounting. The system can be expanded with additonal cameras and switchers. For further information, contact Captain Communications, 26-28 Parkes St, Parramatta, NSW 2124. Phone (02) 633 4333. Premier Batteries Pty Ltd has a wide range of rechargeable nickel cadmium and lithium batteries to suit diverse applications. For further information, contact Premier Batteries Pty Ltd, 7/27 Childs Road, Chipping Norton NSW 2170. Phone (02) 726 7701. 12-way numeric keypad for DTMF * GREAT VALUE AND TECHNOLOGY * 2S&P S85: FOG $97 .25; 101KBD $88.43; ED-CGMA $99; VGA MON $775: 1.2MB FOO $161 .20; 1.44MB FOO $181 .35: Case & 200W PS S207; FOC/HDC $235.30. COMPUTER PRODUCTS ... AT-4000 Motherboard 12MHz 80286 AT u/g for XT . . $ 489 AT-4000 System 12MHz 512k 101kbd, 200w , PS, etc $1499 ECI VGA-16 EGA, CGA, HGA modes Card 800x600x16 Ros $ 300 SAVE 30¾ on Industrial Control Cards ... EC111 6511 2MHz SBC w_ith A/0 0/A Clk Bat. EC109 6809 CPU 2MHz w/Clk Bat 2xRS232 Cent 1/F . EC545 Colour Crt (RGB) 16k/4 page SAAM 512 Char . EC-1F124 IND CONTRLR Forth 10-bit A/D, D/A Opto lsol . LEDS (Min Buy 100 pcs) DIODES 3 & 5mm Red . . . .. $0.05 IN4001 .. 3 & 5mm Red H/B.... $0.06 IN4004 ........... 3 & 5mm Green ...... SO.Q7 IN914 . .. 3 & 5mm Yellow .. . . . $0.08 IN4148 .. . ...... 3 & 5mm Orange . . .. S0.08 $336 $304 $238 $392 $0.05 $0.05 $0.05 $0.05 GAL PAL Programmer - 1 only - Was $750 . . $400.00 G65SC01 ·2 . . $ 3.90 G65SC51 ·2 . . $ 4.00 IBM AT/XT R/T Clk w/Bat .. ..... . $49.95 SAAM Batt B/U Skt. . . $19.95 Quafity DISKETTES . . . (Pkt of 10) 51/," DSDD 306K . . . $ 6.25 51/,' DSHD 1.2m . . . . $17.88 3½" DSDD 720K .. .. $19.75 3½" DSHD 1.44mm .. $39.99 P&P $8.50 PRICES INCL S/TAX 26 Boron St, Sumner Park, Brisbane, Old 407 4 Ph: (07) 376 2955 Fax: (07) 376 3286 WELLINGTON NZ: Ph: (04) 85 87 42 Fax: (04) _82 8850 106 Ken Curry Managing Director SILICON CHIP High speed PC drills from Jaycar If you are building projects you'll want a set of PC drills before too long. This set of ten high speed steel drills comprises one 3.5mm, 2 x 1.2mm, 3 x 1mm and 4 x 0.8mm bits - just about all you'll ever need. They are $12.95 for the set from all Jaycar stores. Looking for a numeric keypad for the DTMF encoder circuit described in last September's issue of SILICON CHIP? This membrane unit from All Electronic Components in Melbourne is a little different from the normal run-of-the-mill keypads which are readily available. Thi~ keypad comes with its own bezel surround and a clear plastic membrane under which a coloured background can be placed. The coloured background will also take whatever transfer lettering you desire so you can label the keypad differently from standard numeric types. It is priced at $32.70 including the header connector. For further information contact All Electronic Components, 118-122 Lonsdale Street, Melbourne, Vic 3000. Phone (03) 662 3506. Fax (03) 663 3822. Get a plastic minigrip tool ·, .:..,_'\-. _ __ :-.,· ' If you are sick of trying to manipulate teensy components into protoboards or inacessible spots on printed boards, try these neat locking pliers with plastic insulated handles. There are two models, with straight or curved serrated jaws. A pair of tweezers with curved serrated jaws is also available. The locking pliers will sell for around $11.00 plus sales tax while the tweezers will sell for around $6.00 plus tax. For further information, contact Scope Laboratories, PO Box 63, Niddrie, Vic 3042. Phone (03) 338 1566. Pocket microscope for PCB inspection How are you on examining PCB solder joints under poor lighting? Ever notice that when the lighting is improved it is still very hard to examine a closely spaced board? What you need is a little microscope with its own built-in illumination. Now you can have it with this handy pocket microscope from Scope laboratories. This lightweight (only 80 grams) instrument has a 4-lens optical system giving 30 times magnification and it has its own built-in light source. It can be easily focussed above or below the surface on which it is placed too, which could be a bonus when inspecting components. The pocket microscope will be available shortly at a price expected to be around $41 plus sales tax where applicable. It should Build a multimeter: ctd from page 6 If that checks out, you can solder in the battery connections. As supplied these are rightangle brackets of what looks to be tinplate. These should be soldered in and bent as shown in the relevant photo. That done, fit the board to the meter housing and secure it with the self tapping screws provided. Now connect the red and blue wires to the meter movement (red to + and blue to - ). The black wire from the buzzer connects to the centre connection and the red wire goes to the terminal marked "to BZ +" next to R6. Mailbag: ctd from page 3 AC 240 volts and DC via batteries or they could be AC or DC 240 volt mains and DC via internal batteries. Not all sets were the AC-DC death traps that John refers to. To quote two brands, AW A sets were equipped with a transformer and were safe to handle while the Astor sets could easily have a live chassis. As a serviceman I made very sure that the chassis was "cold". (9). Sets that worked on both AC or AC/DC and batteries ran their valve That completes the wmng and assembly. All that remains to be done is to screw the back on to the meter and then use it to measure a few known voltages. Alternatively, you can make several AC and DC measurements and compare them to the same measurements made on a digital multimeter. If necessary, tweak trimpot R21 to give the best accuracy. Where to buy it The multimeter is available in kit form from all Jaycar Electronics stores at $34.95 (Cat No KC-5058). It is also available from Jaycar in built-up form at $39.95 (Cat No QM-1022). ~ filaments in series and were run off 9 volts DC at 50mA instead of 1.5 volts at 300mA for 5 valve sets. If the filaments had been run in parallel, the current drain would have been excessive on mains and in some circumstances hum on the filament line would have been difficult to eliminate. (10). Some valve portables, when used on mains, had a battery rejuvenating charging system that improved battery life a bit. I trust these points are of some interest to other readers who like the old valve radios. R. Champness Benalla, Vic Niddrie, Vic 3042. Phone (03) 338 1566. Fax (03) 338 5675. MEMORY CHIPS Prices at October 16, 1989 Type 256 Description Price ex tax 150ns XTs $4.00 120ns ATs $4.25 1 OOns 12MHz $5.00 80ns $6.25 ?Ons 20MHz $7.50 100ns 20pin $17.80 100ns $17.00 80ns $17.80 9x100 SimmLP $190.00 9x100 Simm HP $160.00 9 x 80 Fast Simm LP $210.00 Bx100 MacSimmLP $180.00 8x100 Mac2HP $155.00 Sales Tax 20%. Overnight Delivery 4x256 1Mb 1Mb - Credit Cards Welcome prove invaluable for both servicing and for quality control work. For further information, contact Scope Laboratories, PO Box 63, PELHAM Tel (02) 427 0011 Fax (02) 428 5460 NOVEMBER 1989 107 BOOKSHELF Gateway to packet radio Your Gateway to Packet Radio by Stan Horzepa, WA1LOU. Published 1988 by Tha American Radio Relay League. Soft covers, 216 x 140mm, 233 pages. ISBN O 87259 203 0. $24.95. Packet radio is a very recent form of radio communication for amateurs. It merges the now readily available modems and personal computers with standard amateur communications equipment. It has the advantage of very efficient communication using a very narrow part of the radio spectrum. It also has the ability to store information when the operator is not present, for retrieval at a later time. Basically packet radio uses a computer and modem to modulate the transmitter and also to decode modulation from the receiver using an agreed protocol. The information sent or received consists of packets or bursts of digitally coded information. In practice, the packets consist of smaller blocks of information called frames. These comprise the information frame, the supervisory frame and the un-numbered frame. 108 SILICON CHIP You can either use computer software to create and decode the packet information or use a dedicated hardware unit called a Terminal Node Controller, or TNC for short. One of the many advantages of using packet radio is that because your transmission is addressed, you can direct your information to a particular station. The message will be left whether or not the station is manned at the time. In summary, this book is a throughly informative and useful guide for both the newcomer to packet radio and the experienced user. We would recommend this book to any packet radio operator and to any amateur interested in starting up this interesting form of radio communication. Our copy came from Dick Smith Electronics. Industrial control handbook Industrial Control Handbook, Vol.3: Theory and Applications, by E. A. Parr. Published 1989 by BSP Professional Books, Division of Blackwell Scientific Publications Ltd. Hard covers, 163 x 242 x 400 pages. ISBN 0-632-01859-3. Price $160. While many books which deal with industrial control delve heavily into the mathematics of control theory, this book presents a refreshing change to those of us who prefer to understand concepts without being loaded down by complex mathematics. It is a very readable book which covers the background theory to process control. There are seven chapters including an introductory chapter which deals with such topics as proportional control, plant modelling, non-linear elements and stability. The following chapters deal with system modelling; stability; controllers; complex systems; signals, noise and data systems; and finally, applications of real control situations. Mathematics covered in the modelling and stability chapters include the Bode diagram, Nyquist diagram and the frequency response. Routh-Hurwitz criteria, Root Locus and Laplace Transforms are covered with good detail. Readers are expected to refer to books on mathematics to understand the underlying principles, particularly the Laplace Transform. The remaining chapters discuss various controller types, such as digital, analog and pneumatic; and characteristics of real systems. The sixth chapter covers filters and types of modulation such as AM, FM etc. Finally, the seventh chapter gives three real world control applications. They are a steel mill reheat furnace , a chemical plant and a power station. One of the three appendices is for two computer programs. The first is for evaluation of open and closed loop frequency response, drawing Bode diagrams, Nichols charts, Nyquist diagrams and step response. The second program draws the step response of a system as described by a transfer function. The second and third appendices cover complex numbers and trigonometrical relationships. We recommend this book to undergraduate students of engineering and engineers working in process control. It is excellent for explaining many of the control theory aspects that are normally obscured in more advanced books by heavy mathematics. Our copy came from Blackwell Scientific Publications (Australia) Pty Ltd, 107 Barry Street, Carlton, Victoria 3053. Phone (03) 347 0300. Satellite adventures for amateur radio cribe the receiving and transceiving aspects of operating via a satellite. This includes equipment such as receivers, transmitters, antennas, frequencies and satellite location. Some of the information on finding and tracking satellites will need to be obtained elsewhere and may be in graphical form or a computer program. The details on these are all included in this book. Overall, the 'Satellite Anthology' is packed with lots of useful information for amateurs interested in satellite communications. If you want to get involved in the practical side of satellite operations, this book is an excellent starting point. The price is no problem either. It sells for just $13.95. Our copy came from Dick Smith Electronics. (J.C.) Troubleshooting with the oscilloscope The ARRL Satellite Anthology. First edition, Published 1988 by The American Radio Relay League. Soft covers, 275 x 209mm, 97 pages. ISBN0 87259 210 3. Price $13.95. This book is a collection of articles reprinted from the ARRL magazine "QST" explaining the current active satellites and those planned for the future. The aim of the book is to enthuse and inform amateur radio operators to extend their contacts using satellites. The satellites are the OSCARs (Orbiting Satellite Carrying Amateur Radio). OSCARs 9, 10 & t:.. are included, along with the latest satellite, OSCAR 13 (also known as the phase 3C satellite). Phase 4 is a planned series of geosynchronous satellites, one of which (Amstar W) will have a footprint covering the USA and the east of Australia. Several r.hapters are devoted to general satellite DXing and des- Troubleshooting With The Oscilloscope, by Robert G. Middleton. Revised by Joseph J. Carr. Fifth edition, Published 1988 by Howard W Sams & Company. Soft covers 216 x 136mm, 227 pages. ISBN 0 672 22473 9. Price $39.95. This is the fifth edition of a book which was first published in 1962 and although some of the photographs are of more recent origin, much of the content fails to hide its heritage. Much of the book (six of the eleven chapters) is concerned with operating an oscilloscope on typical (for that time) NTSC television circuits. One or two of the circuits actually use an IC but most are discrete transistor sets. TV troubleshooting starts at Chapter 4 which is headed "TV Signal Tracing in RF, IF and Video Amplifiers". Chapter 5 is titled "Signal Tracing in the TV Sync Section" and then follows Chapter 6 "Trouble Shooting the TV AFC and Horizontal Oscillator Section". Chapter 7 covers "Waveform Tests in the Horizontal Sweep", Chapter 8 the "TV Vertical Sweep", and Chapter 9 "Signal Tracing in the TV Sound IF and Audio Section". Chapter 10 is titled "Special Oscilloscopes and Applications" and is worth passing over. The application (singular) is to build your own time domain reflectometer using a piece of coax ea ble and a NAND gate for a pulse generator. You send the pulse down the coax with various end loads and see what happens on the oscilloscope. Its purpose? To check out TV antenna transmission line problems. The "special oscilloscope" is really a block diagram for a spectrum analyser using a standard oscilloscope - a bit of a joke really. The final chapter shows how to troubleshoot digital logic with the oscilloscope. Here it shows how to check out AND, OR, NAND, NOR and XOR gates, which is fair enough. It also shows a 4-bit binary counter circuit and its timing waveforms. This is not particularly helpful since few people these days would build up a counter using discrete flipflops and gates. They buy the chip which does the job and if it is faulty internally, they try a new one. To be fair to the title of the book (remember it is "Troubleshooting With The Oscilloscope" not "Servicing American TV Sets"), the first three chapters do introduce osciHoscopes, show how to operate them and discuss the all important oscilloscope probes. All of this information could be found in the manual accompanying the oscilloscope of your choice. Keep your money and put it towards a good oscilloscope. Our copy came from Altronics (Cat. B-2120). (J.C.) NOVEMBER 1989 109 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Electronic ignition for a Mazda I am about to construct the High Energy Ignition System as described in the May and June 1988 issues of SILICON CHIP for my 1982 Mazda 929 Hardtop. I am having trouble obtaining the required vane and rotor for my distributor via my local Repco branch. They told me that Bosch manufactures vanes for Bosch distributors only and not for my distributor. They are not aware of other makers. I can obtain a whole distributor from my local wrecker which I think should do the job. It's an imported unit but I am not sure if it's got a Hall Effect unit or a reluctor unit. In your June 1988 article you mention that the Motorola MC3334P ignition IC was specifically designed for reluctor type pickups. Could you please tell me (a) how to identify a reluctor pickup and how it works; (b) the maker of a vane and rotor for the Mazda 929 distributor; and (c) what modification to the circuit is necessary if I decide to fit a reluctor type pickup? (G.D., Morwell, Vic). • As far as we know, Bosch is the only manufacturer to make vane and rotor assemblies to suit the Siemens HKZ-101 Hall Effect pickup. Bosch also make complete distributors fitted with Hall Effect pickups, as fitted to the Australian made engine on the Holden Camira. The ignition systems on the locally made Falcons, early Commodores and Sigmas use distributors with reluctor pickups. These are easily recognised when you remove the distributor cap. Inside you will see a large toothed wheel with the number of teeth corresponding to the number of cylinders in the engine. The toothed wheel is the reluctor. The reluctor works in conjunction with a pickup coil wound on a permanent magnet. As each tooth of the reluctor passes in front of the coil, the amount of magnetic flux passing through the coil is varied; ie, the magnetic reluctance is varied by the reluctor. This causes a varying signal voltage to be produced by the pickup coil and this is Wants source for Toshiba TA7376P? Could you please advise me where I could purchase two Toshiba TA7376P stereo audio amplifier ICs as used in the AM Stereo Radio featured in the September and October 1989 issues of SILICON CHIP? I suffer from hearing problems and require these to build stereo amplifiers for both the TV set and car audio systems. These items are not available in this state. (H.S., Lesmurdie, WA). • As far as we know, there is no retail outlet for these chips as yet. Dick Smith Electronics now has a full kit for the AM Stereo Radio but they have not put the TA73 76Ps into regular stock. 110 SILICON CHIP However, they expect that in a few months or so the ICs will be available as a spare part. In the meantime, you could consider the LM831 dual amplifier IC which we used in the Motorcycle Intercom. This has the advantage that it will deliver more power than the TA7376P which is really only intended as a headphone driver. We will be running a short article on the technical specs of this chip next month. We are informed that Geoff Wood Electronics will have the device in stock shortly. Expected retail price is $3.95. Give them a call on (02) 428 4111. used to control the following ignition circuitry. In the May 1988 issue we published some technical data on the MC3334P which included a circuit using a reluctor pickup. This circuit also had a feature for reducing the coil dissipation at low engine speeds. The circuit could be built onto the board designed for the High Energy Ignition System although without the dissipation reducing components. We understand that some readers have already done this successfully. If there is sufficient demand from readers we could do an article showing how to build the High Energy Ignition using reluctor pickups. Wireless loudspeakers This idea needs some thought but would be very useful. How about using the FM stereo transmitter described in the October 1988 issue of SILICON CHIP together with a receiver fitted into each loudspeaker box to eliminate speaker leads. This would allow more freedom for speaker placement. You could take a speaker to the bedroom or out to the barbecue. Maybe you could design a low power unit for a small speaker and incorporate overload protection if power handling capacity is a problem. Maybe you could use the TDA7000 IC as the FM receiver. (A.M., Browns Plains, Qld). • Designing and making a separate FM tuner and power amplifier for each stereo speaker would not · be a cheap proposition. Since you propose using the FM stereo transmitter, each tuner would need a stereo multiplex decoder. In other words, each powered loudspeaker would need its own stereo tuner, even though only the left or right channel info would be needed in each case. Wants high quality recording system I am still very green with modern electronics but I am learning fast. I wish to build a quality sound system/recording facility from kits but am having trouble deciding what kits to use. How does this sound to you: 8 channel stereo mixer (to mix inputs from phono, tape, CD and tuner) to the Studio Series Half Octave 20-Band Stereo Equaliser to the Studio Series 200 Stereo Power Amplifier to high quality loudspeakers? If this is OK to listen to will I be able to record from it? (K.G., Port Augusta, SA). The TDA7000 would not be suitable because it is a mono receiver. Also, as we point out in the motorcycle intercom project published last month, because it is a narrowband receiver, it uses a cunning technique to limit the FM deviation fed to its detector circuitry. This effectively compresses the recovered audio signal. This is an ideal solution when you are listening to an FM station while riding a bike at 110km/h down the freeway but it does limit the dynamic range of the music. Really, if you just want to listen in a casual way in a bedroom or out at the barbecue, the solution is to use the FM . stereo transmitter as originally described and use a standard "ghetto blaster" portable receiver to pick up the signal. It won't be real hifi but the sound will be acceptable. Wants advice on soldering stations I am writing to you for some advice on buying a soldering station. I have been interested in electronics for some time and have decided that it is about time to get myself a decent soldering set-up. After examining all the available information in catalogs, I have come up with a few questions. The most important question I • Yes. If such a set up sounds good, and we have every reason to believe that it will sound excellent, then it will be equally good as far as recording goes although ultimately the standard of reproduction will depend on your tape recorder. Incidentally, if you are contemplating building an 8-channel mixer (from Jaycar we presume?) watch out for our new 16 channel mixer which will be published soon. This will be a very comprehensive high performance unit with everything that opens and shuts and much cheaper than equivalent commercial units costing many thousands of dollars. have concerns tip life. All the sales pitches seem to say that their iron tips last at least x times as long as the competition. Do you know of any irons whose tips do not last? I have had quite enough experience of trying to solder with an iron that needs to be filed every half an hour and do not wish to spend $200 on a new one with the same problem. Secondly, there is the matter of temperature adjustment. Most of the stations seem to have a temperature infinitely variable between about 200° and 400°. The station that I think is the best value - the Micron T2440 from Altronics - has only 5 switched temperature positions. Additionally, the minimum temperature is a relatively high 320°. Finally, if you have any general suggestions about a soldering station that is particularly good, I would be keen to hear them. I am prepared to spend up to about the $200 mark. (W.K., Macquarie, ACT). • We have mixed feelings about soldering stations as far as many hobbyists are concerned. For the technician who has a soldering iron going all day, a temperature controlled soldering station is undoubtedly a good idea but we would hesitate to recommend a particular model. Soldering stations are like cars and people have strong personal preferences. Advertising Index Allied Capacitors . . . . . . . . 1 03 Altronics . . . . . . .. 72-75 Arista Electronics . . . . . 11 Board Solutions . . . . IBC Dauner Electronics. . . .. 49 David Reid Electronics . . .. IFC Dick Smith Electronics . .. 26-31 Electronic Solutions. . . 38,39 Elmeasco . . OBC Energy Control. . . . . . . . . 106 Geoff Wood Electronics .... 45 Harbuch Electronics .... 37 ,85 Hycal Instruments .. . .... . 49 Jaycar Electronics . . . . . . 53-60 Pacific Microelectronics . ... 37 PC Marketplace . . . . . 1 2, 1 3 Pelham. . .... 107 RCS Radio . . . . . . . . . . . . . 91 Rod Irving Electronics . 104,105 WIA . ....... . ... . ..... 98 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491 . • Jemal Products, 5 Forge St, Welshpool, WA 6106 . Phone (09) 350 5555. • Marday Services, PO Box Avondale, Auckland, NZ. Phone 88 5730. 19-189, For the person who does not frequently use a soldering iron though, we are inclined to think that the temperature adjustable 240V AC soldering iron is a much better proposition as it represents quite a saving over a soldering station. Strictly speaking though, you then need a soldering stand to keep the iron safely anchored while it is not in use. A hot soldering iron just resting on your workbench is a dangerous implement; it can burn you badly if it is dragged off the bench onto your lap. Chrome plated iron clad tips are very worthwhile as they do last much longer but there is a catch. Many of the iron clad tips are a bit useless because their shape is unsuitable; you need a chisel shape tip for most work. Remember that you can't file an iron clad tip to shape. NOVEMBER 1989 111 TCEN Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON 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 run your own classified ad, put one word on each of the lines below and send this 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) 18 ($820) 19 ($8.60) 20 ($9.00) 21 ($9.40) 22 ($9.80) 23 ($10.20) 24 ($10.60) 25 ($11.00) Name · · · ······· ·•· •· ·• · · · · •· •· •·· ·· · ·· · ··· ·· ·· · · •· · · ••·· Street Postcode Suburb/Town Enclosed is my cneque or money order for $ .. Bankcard D Visa Card D MasterCard . or please debit my D Card No I I I ..... ....... Card expiry date ..... . ./ . .... ../. ...... . Signature FAX THIS COUPON WITH YOUR CREDIT CARD DETAILS TO (02) 982 9553 FOR SALE PUBLIC DOMAIN & shareware software for IBM & compatibles. Catalog disc $4.00. Also TV-REPAIR.TXT which covers faults in most popular brands. It can save hours of work. On a 5¼-inch disc. Just $28.00 inc. p/post. Martins Television Service, PO Box 1013, Taree, NSW 2430. SATF AX: WEATHER SATELLITE picture receiving program for IBM XT/AT. Displays in 64 colours . Needs EGA colour monitor & card, AM demodulator & ADC interface. $45 plus $3 postage. RADFAX2: HF WEATHER FAX, Morse & RTTY receiving program for IBM 112 SILICON CHIP XT/AT. Needs CGA, SSB HF, FSK/tone decoder. Also "RF2HERC" & "RF2EGA", same as RADFAX2 but suitable for Hercules & EGA cards respectively. $35 plus $3 postage. All programs are on 5 .25-inch 360K floppy disc & include full documentation. Only from M. Delahunty, 42 Villiers St, New Farm, Old 4005 . Phone (07) 358 2785. RETAIL SALES Retail sales person required to join Australia's fastest growing electronics retailer. Must be an enthusiast. Contact Jeff Yaeger, David Reid Electronics Pty Ltd. Phone (02) 267 1385. 1M PRINTER BUFFER KIT. Rev H boards now available. Supports 8Kb to 1 Mb. $39 kit consists of double sided PCB, EPROM and instructions. Optional additions include 2 x 7 -segment LED front panel display of percentage full, 1 to 99 copies select, 3 polled computer inputs, printer switches, computer switches and serial converter boards. For a free catalog send a 39c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. ACTIVE TRANSMISSION line stereo speakers. Includes preamp. $760 .00. Send SAE to 36 Palmer St, Nambucca Heads. NSW 2448. SIEMENS HKZ101 HALL EFFECT sensors. Three only, $20 each. Never used. Phone (02) 744 8881 (AH) John. TUNING IN - announcing a new concept in news bulletins. Join our dynamic team of over-unity researchers by subscribing today. News, views, feedback & linkup. All the latest on the free energy scene. Only $25.00 for 12 issues. Write today. Free Energy Connection, PO Box 255SC, Ivanhoe, 3079. FUEL COSTS TOO high? Build your own high mileage vapour-carb. Up to 70mpg achieved on big 6 Valiants. Write today: E.P.M. Power Systems, PO Box 255SC, Ivanhoe 3079. THE HOMEBUILT DYNAMO by Alfred T. Forbes. Published by Todd-Forbes Publishing, Oratia, Auckland, New Zealand. Hard cover, 8½ x 12-inch, 182 pages with over 300 illustrations. ISBN 0-95977 49-0-4. Price $A85 postpaid airmail direct from ToddForbes Publishing, Dept. D3, PO Box 3919, Auckland, New Zealand. Trade enquiries invited. "What a delight this book will be to any lover of anything to do with DIY, ingenuity and devotion to the completion of a job once started. It is the complete pictorial history of how Alfred Forbes built a dynamo to power his house in New Zealand ... Definitely a book to put on your list of wanted Christmas presents" . - Practical Electronics. Board Solutions PO BOX 1120 Lane Cove 2066. Telephone: 906 5696 Facsimile: 906 5222 51/4" disks With any order over Sl 00, you can order up to 5 boxes of these DSDD That's below manufacturer's cost!! Miniscribe 20MB Drive & Controller 101 Key XT/AT Keyboard We will match Electronic Solutions prices on all products we sell. Phone for pricing on other products and complete systems o Superb quality with Japanese keyswitches. o o XT/ AT switchable Baby AT Case O o We've put together two fantasic hard disk deals. Both include the superb Miniscribe drive and high speed controlers. Flip top design Caters for up to 8 expansion slots o Heavy duty 200W AT power supply o Internal tray fits 3 half height drives Full AT "enhanced" layout 0 Turbo XT Motherboard o G~e your old XT a new lease of life with this 10MHz motherboard. o Over 2 times faster than PC. 4. 77MHz/l OM Hz switchable o 8 expansion slots o Accepts 640K on motherboard normally $494.00 Cheap Chips now only $399.00 o AT Controller and Drive EGA Graphics card O Fully IBM EGA compatible, as well as back compatible with CGA MDA and Hercules TTL monochrome. o Perfect for Windows, Ventura. AutoCAD etc . normally $574.00 normally $249.00 now only $229.00 now only $425.00 41256 256K 1OOnS RAM Chips normally $16.00 now only $9. 95