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Installing A Hard Disc In The IBM PC Registered by Australia Post. Publ ication No NBP 9047 1 legabyte Printer Buffer GaAsFet Preamplifler FI Radio lnterc 111 Implants For Anl■als: WIii Humans Ba Next? wpoo FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR C MORE GOODIES FROM WOODIES DATA BOOKS GALORE!! Now stocking quality AT&M Kits At last a range of super high quality kits for the professional user. Saves the bother of designing and building many of the commonly used circuit blocks. These kits have been locally developed and come complete with instructions for construction and testing. All components are professional grade and the very latest techniques are used. Ideal for industrial and educational use. As and example the ATMOS Fibre Optic Modem Kit uses Siemens We've built our reputation as suppliers of the widest range of chips. Remember ~wood for Chips"? Well soon you'll be calling "Wood /or Data·. 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August for full range details Kit Description Price ATM01 3 digit Counter $31.80 ATM02 4 digit Counter 45.60 ATM03 3 1/2 digit DVM 51.00 ATM04 1Hz Timebase 29 .40 ATMOS Fibre Optic Modem 75 .00 ATM06 Reciprocal Calculator 29 .40 ATM0710MHz Timebase 45.60 ATMOB V/f- Converter 34.20 ATM09 FN converier 34.20 ATM10 Triple Power Supply 51.00 ATM1110 Minute Controller 45.60 ATM126 dig Batch Counter 75.00 ATM13 IR Proximity Detector29.40 ATM14 FM Transcoder 34.20 ATM15 DC Amp/Attenuator 41.40 ATM1610kV Isolator 65 .40 ATM17 8 AID and D/A ATM188 bit UART 50.40 ATM196 dig Up/On Counter 69.60 , ATM20 IR Transceiver 39.60 GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road , (Corner Beatrice St.) INC INNsw Lane Cove West, N.S.W P.O. Box 671 , Lane Cove N.S.W. 2066 Telephone: (02) 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. All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED ~ a c:, .,., a ::0 C) :i: ~ ~ a c:, .,., a ::0 2 ~ ~ a c:, .,., a ::0 C) :i: ~ ~ a c:, .,., a ::0 C) :i: "ii "' ~ a c:, .,., a ::0 C) :t "ii "' OCTOBER 1 989 THIS FM RADIO INTERCOM can provide communications between motorbike riders or can be used in power boats, rally cars or open cockpit aircraft. See page 20. FEATURES 16 Making You r Electric Radiator Safe by Leo Simpson Replace that inadequate cord & plug 98 The Technology Letters by Richard Kopf More adventures in America 104 The Evolution of Electric Railways by Bryan Maher Pt.24: A look at Australian monorails PROJECTS TO BUILD 20 FM Radio Intercom For Motorbikes by John Clarke Can also be used in power boats & rally cars 32 The Gladesville GaAsFet Amplifier by 'Julie' Kentwell Easy-to-build design for amateur TV 40 1-Megabyte Printer Buffer by Don McKenzie Frees your computer during file printouts 58 2-Chip Portable AM Stereo Radio by Steve Payor Pt.2: construction details LAST MONTH-, WE described the circuit details of our exciting new stereo AM radio. This month, we show you how to build it. See page 58. I SPECIAL COLUMNS "~ 4 Remote Control 10 50 76 84 86 by Bob Young The beginnings of remote control Vintage Rad io by John Hill Collectables & non-collectables Serviceman's Log by the TV serviceman "Bar humbug!" - as Scrooge would say Computer Bits by Jennifer Bonnitcha Installing a hard disc in the IBM PC Amateur Radio by Garry Cratt SWR - just how important is it? The Way I See It by Neville Williams Today they're tagging animals; tomorrow it might be humans! -· =1=\ _I NO! - THE SERVICEMAN didn't stick his head in the oven this month. But he did use a head tester. Why? All is revealed starting page 50. DEPARTMENTS 2 Publisher's Letter 3 Mailbag 55 Bookshelf 67 Back Issues 74 Circuit Notebook 91 Subscription Page Product Showcase Ask Silicon Chip Notes & Errata Market Centre 92 110 111 112 THERE'S NO NEED to tie your computer up for long periods when printing out files. This easily built 1Mb printer buffer will free your computer for those other tasks. Turn to page 40. OCTOBER 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. Typesetting/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 LE'l.l'ER The joys of remote control Some people have written to us suggesting that we don't need to change the content of SILICON CHIP - it's just right. However, no change soon leads to stagnation. With that thought in mind, we are introducing a new column this month on the subject of remote control. We hope that this generates a big following, as have our other regular columns. We know that many of our readers are deeply involved in one or more aspects of remote control although they possibly think of it under the more specific heading of "radio control". You only have to consider the widespread popularity of radio-controlled models of all sorts, such as cars, fixed wing aircraft and helicopters, boats and yachts, to realise just how wide the field is. Nevertheless, the new column will use the more general heading of "Remote Control" and will also cover such equipment as garage door controllers, infrared controls (such as for VCRs, TV sets and audio gear) and remote controlled industrial and defence equipment. We are very pleased to have an acknowledged authority writing the column, Bob Young, of the well known firm Silvertone Electronics. Bob has been in the game for many years, both as a keen modeller and as a manufacturer of remote controlled equipment of all kinds. This month Bob Young will start off with a general introduction to the subject of remote control and he will continue in this vein for another month or so before getting down to specific aspects of the subject. With such a large subject to write about we expect that he will never run out of topics. Remote control is yet another fascinating field in the world of electronics. Just consider some of the possibilities: radio controlled electric powered aircraft, helicopters with gyroscopic control, submarines, cars with full gearboxes and suspension. It is a short step from these to target and surveillance vehicles for defence purposes and large remote controlled equipment like road construction machinery, window washing machines and props for film making. Serious stuff, but fascinating nonetheless. Go to it, Bob, and welcome to SILICON CHIP magazine. Leo Simpson MAILBAG Liked the July issue Congratulations on a refreshing magazine. It's good to see once again something for the electronics enthusiast. I have every copy so far. I have recently purchased two small 6V gel cells, intended as rechargeable batteries for torches. The next problem is a charger to suit and several ideas have come along, but none better than the special chip used in Garry Cratt's July effort. The UC3906 seems like the ideal solution providing it can be modified for 6V batteries. The $64,000 question - can you or Garry please supply a circuit to suit 6V charging. This may also interest many others and warrant publishing in Garry's regular column? Regarding exhaust gas analysis, while calibration may present a problem at home how would one attach a meter to the output to the Exhaust Gas Monitor in the July issue to take (at least) comparative readings? A. Watson Mudgee, NSW Comment: we will be doing a follow up article on the UC3906 intelligent battery charger chip and will provide a modified circuit for 6V batteries. The Exhaust Gas Monitor is a comparator circuit and is not really suitable for driving an analog meter. Vintage radio series appreciated Thanks very much for SILICON CHIP magazine. I look forward to each issue every month. I particularly enjoy the Vintage Radio (maybe it should be called "wireless") column. "Rebuilding a Vintage Radio" in the August issue was great. I have recently finished a 5-valve mantle radio and it performs very well. I obtained it as a kit from Antique Electronic Supplies in the US. It's based on the age-old design '' AllAmerican Five". I guess millions must have been made. It's "transformerless" so I had to get a suitable step-down transformer from Jaycar. I had a lot of fun building it and, once a problem of motor-boating in the frequency-changer valve had been fixed, it worked superbly. I haven't been able to measure the audio amplifier's frequency response but the general sound quality is good - much better than today's transistor equivalents. Antique Electronic also has an 8-valve stereo hifi amp available (as a kit). I'm hoping to build it sometime soon. Keep up the good work. I have purchased every issue of SILICON CHIP since issue 1. T. Robinson Woodend, Vic Hercules graphics card not mentioned Gudday. Just a brief note to say that I was a little disappointed that Jennifer Bonnitcha did not mention Hercules Graphics in her Computer Bits column. Jennifer states that the two adaptors which represent a large majority of those currently in use are the monochrome with printer and the CGA. While I have seen many different adaptors over the years, I have never come across the monochrome adaptor which does not have graphics capabilities as mentioned in the article. The monochrome adaptors which I have seen all have a very high graphics resolution (720 x 348 pixels) and are very easy (and fast) to drive since the pixels are arranged in continuous memory locations, each pixel taking one bit, 90 bytes for each row of pixels . Also, it appears that EGA could be out-selling CGA at present due to the better resolution without having to fork out big bucks, while monochrome continues to sell (lets face it, word processing with CGA is awful). SILICON CHIP, PO Box 139, Collaroy Beach 2097. Also I have noticed quite a few PC projects lately, all of which make bigger demands on my PC's power supply. I have upgraded my PC to AT but I still have a 150 watt power, supply driving two floppies, a 30Mb hard disk and a Cypher tape drive. Has anyone designed an upgrade power module (200W or better) so that my XT supply can · retire before it dies? Or am I better off buying an AT supply for about 200 bucks? I look forward to each issue of SILICON CHIP it's the best magazine for electronics in Australia. Keep up the good work. S. Rollinson (Address not supplied) Comment: the standard monochrome display adapter card in IBM PCs and compatibles will not work with software which calls for the colour graphics adapter card. This does not mean that you can't produce graphics displays via the monochrome display - you can but a lot of software, particularly games, will not work. The best way to upgrade your XT computer supply is to buy an AT supply as you suggest. Likes articles on electric railways I would like you to know how much I have enjoyed SILICON CHIP'S series "The Evolution of Electric Railways". ! would think that if all the parts were gathered together into one publication it would make a most interesting book that I for one would most certainly buy. T. Salmons Brackenridge, Qld Cover acknowledgement Our thanks to Toy Traders, Ermington, NSW for this month's cover illustration of the Tamiya Porsche 959 radio controlled model car. Tamiya products are available from toy & hobby stores. OCTOBER 1989 3 REMOTE CONTROL By BOB YOUNG The beginnings of remote control Bob Young has had over thirty years experience as a designer and manufacturer in the field of remote control, particularly radio control. He is the proprietor or Silvertone Electronics, which has been notable for radio control products for many years. In this, his first article in SILICON CHIP, he introduces the subject of radio control. When Leo Simpson approached me to do a monthly column on remote control, I was a little hesitant at first. While I have written quite a lot for radio control model aircraft magazines during my 26 years as a radio control manufacturer, I have never had the chance to discuss all aspects of remote con-. trol, either model, industrial or · commercial. , Not that this presents any real problem, for during those years I have undertaken projects covering :an of those aspects and many more, including some low key military applications. I Perhaps by way of introduction then, a brief description of some of the more interesting projects in remote control I have been involved in would be in order. But first to the name. Originally, or as the Bible puts it, " In the beginning", remote control was generally accomplished by the "wireless" transmission of one or more frequenies in the electromagnetic spectrum. This was the system used by Tesla in his model submarine, the very first R/C [radio control) model, demonstrated in 1896. Tesla used two separate carrier frequencies and an AND gate [another of his inventions). Thus, as a general rule, remote control became "radio control". Technology has rendered this term obsolete with the development of ultrasonic, infrared, laser and long range wire-guided systems, and a host of other mediums of transmission. To further complicate things we now have radio controlled people, as many service vans tell us on their advertising panels: "Radio Controlled, 24 Hour Service". Thus our field of interest is better described as the ''Remote Control of Mechanical Devices" or if a vehicle, the more common "Remotely Piloted Vehicle" or RPV. This now leaves the way open to employ any transmission medium we choose. The early days It appears that Leo remembers me from the early days at Silvertone Electronics. Around 1965 or thereabouts I developed a single channel TX (transmitter) and Rx [receiver) for use in models. This early super-regenerative receiver from Silvertone Electronics was a hybrid unit employing an XFY34 valve and three germanium transistors. 4 SILICON CHIP Before servos became available, model aircraft were controlled by rubber-driven escapements which gave left & right rudder control. This wa:s very popular with radio control modellers of the time and was regarded as state of the art. It had a one valve super-regenerative front end using an XFY 34 to give a bandwidth of 300 to 400kHz. Following the front end were three transistors, the final stage driving a miniature relay, which in turn drove an escapement. The escapement was a rubber band driven actuator which was used to turn the rudder; the only control available. It was operated in sequence: first left, then right. There were no steps in between. If you forgot which you used last, left or right, you just found out the hard way. All this was driven by a 1.5V penlite cell and a 22.5V hearing aid battery supplying the HT (high tension). Oddly enough, these sets were extremely reliable and gave good results in practice. We did some very satisfying flying with them and the only reason we stopped servicing them was that hearing aid technology zoomed ahead and valves and 22.5V batteries became difficult to obtain. Over the years we gradually developed these sets into a fully transistorised unit which was much nicer to handle, with its single 6V battery and no delicate valve filament to worry about. And of course super-regen gave way to superheterodyne. Electrically-driven servo units eventually took over from escapements. This early unit is Japanese made and is big & bulky by modern day standards. Reed units Single channel receivers gradually gave way to tuned reed units. These were a real eye-opener and I tend to feel sorry for any modeller who missed this era. Here we used a bank of 10 or 12 tuned reeds to filter out the audio tone modulation, thus giving true multi-channel operation. Heaven had arrived on Earth at last. These 12 tones had to be tuned inside a full octave to avoid har- Tuned reed units were used to fiter the audio tone modulation on the receiver output to give multi-channel control. This unit employed 10 separate reeds. monies and placed extraordinary demands on the tone generator, for they had a bandwidth measured in just a few Hertz (typically 4-BHz), or as we used to say in those days, a few "cycles per second". If there was any drift in the receiver, it would be all over for the model. Modern solid state oscillators have no problem achieving this degree of stability but in the late 50s it was almost impossible to achieve in a portable unit. The reedbank itself was very cleverly constructed right from the very beginnings and changed little in the 10 or so years they were in commercial production. Practical results were poor though, until Bob Dunham of Orbit in America, produced a toroid stabilised tone generator which revolutionised the sport of radio controlled model aircraft. Reliability became accepted as the norm and the really good flyers produced results which were almost indistinguishable from those seen from modern proportional control units in use today. This was quite a feat, keeping in mind that we only had on or off servos, no proportional. You learned to pulse the controls for half throw. The other major problem and one that still shows up today in modern remote control systems, was the lack of simultaneous control. Modern garage door units, for exOCTOBER 1989 5 This view shows the works of a modern radio-controlled model aircraft. The multi-channel receiver at left drives a number of servo units for full control over throttle, ailerons, flaps, elevators, rudder & nose gear steering. ample, now give up to 10 separate switching channels (in remote control a decoded data stream is called a channel) but not simultaneously. This is no problem when switching on lights but in a model aircraft travelling at 50 metres per second there is no time for queued commands. Also some manoeuvres call for the application of three or more controls simultaneously. Thus a successful remote control system for vehicular work must be capable of simultaneous multi-channel transmission with a response time of less than 100 milliseconds. Modern digital systems can deliver 32 channels very easily in less time than this. Interestingly enough, despite this being faster than the human response time (200 milliseconds), you can still notice the slight lag in control response. For competition flying, 50ms is the absolute maximum cycle time with the typical figure being around 14 to 20ms. To arrive at this modern system was a constant technological battle every inch of the way. I started by producing a super-regen valve/ transistor hybrid unit, using 10 miniature relays and a 22.5V HT 6 SILICON CHIP battery, which had to be large enough to drive the relays. The whole airborne system including batteries came out at about 22 ounces (this was before the days of metrics, remember) and it was big and bulky. To give simultaneous control of two channels, we mixed two tones which halved the power to each reed and made tuning even more difficult. Reed gaps had to be adjusted and in the early days before transistorised amplifiers to drive the servo motors, you had the inductive load of the relay on the reed points which resulted in pitting. The relay contacts had to be adjusted and kept clean as well. No instructors On top of all of this you had to teach yourself to fly. No RCAS (Radio Controlled Aircraft Society of NSW) qualified instructors on flying fields in those days. Ah ... they were the good old days. But we really did enjoy it. The incredible difficulties that each of us faced in bringing home the model intact after a day's flying generated a sense of camaraderie no longer seen these days. And the sense of achievement - it was indescribable. However above all of this the thing that sustained our interest was the constant dream of the big one: simultaneous proportional control. When we got that, we could build scale Spitfires with retracts. To cut a long story short, we did eventually get just that and much, much more but very few of us ever built that scale Spitfire with retracts. Such is the stuff that dreams are made of. My first production proportional set was a fully transistorised, 5-channel PPM (Pulse Position Modulation), superhet unit with an airborne weight of 450 grams (I measured it as 16oz but I've converted it for the benefit of those who have forgotten ounces). I could not believe that I had finally achieved true three dimensional flight with five simultaneous controls and the freedom and accuracy of manoeuvres that accompanied this amazing technological achievement. And it was amazing; make no mistake about it. I still look in wonder at the incredible cleverness of the men who made all of this possible. I dislike intensely the modern jaded consumer who has everything This modern radio-control transmitter uses pulse code modulation (PCM) techniques to provide simultaneous 7-channel control. The aircraft is flown by manipulating two joystick controls on the front panel while optional channel mixing is provided by the front-panel switches. and never stops complaining, or worse still, never stops to consider the magic of it all. They were heady days, for we were blazing trails where no.man had gone before. But the most amazing thing of all, from my point of view as a technician, was the lack of tuning resulting from the use of .Pulse Position Modulation (PPM). It was unbelievable. These days it seems incredible when I look back at just how difficult it all was. When I look at the modern control unit with microprocessor control, inbuilt memory, voltage monitor, liquid crystal display and everything else that opens and shuts, it takes my breath away. It all seems so long ago and I guess it was, for I flew my first R/C model in 1955. Yet even today I have not lost my fascination for the concept of wireless control of model aircraft. To me, it is the ultimate in technological achievements and yet Tesla was sailing his multi-channel radio controlled model submarine long before Marconi ever achieved his reputation. That man was absolutely incredible. But that's another story. Other applications As a result of my experience in radio control, I gradually became interested in the wider applications and thus began to involve myself in industrial and commercial projects. Some of the early ones included radio control of flag poles, the window washing robot for the Sydney Opera House, a full size Volkswagen 1600 TLE, toasters, chairs and so on. You name it, I have done it or at least, thought about doing it. It was all good fun but very dangerous at times. Hanging off a flag pole in a high wind, 22 storeys above the ground is not my idea of the best way to spend an afternoon. Flying military target models, in which people are constantly putting bullets through receivers and batteries and servos, and which results in aircraft digging furrows near where you are standing, is another. Nearly running over a curious policeman with a driverless Volkswagen rates low on the scale also. And of course there was the day we had to test the droparm switch on the Opera House window washing robot, only to see it skid to a stop, totter at the end of the glass roof, and vanish over the edge of a 20 metre drop, nearly taking an apprentice with it. When we peered cautiously over the edge, there was 90 kilograms of robot dangling in space at the end of a rubber hose, with a quick disconnect fitting the only thing between it and oblivion. All of this on a wet, glass roof, pitched at a very unpleasant angle. But all in all, I would have to be listed among those who really did enjoy my work, that is until the economic system fell over in Australia and manufacturing became a dirty word, particularly in consumer electronics. Thus, in keeping with all of the survivors, we fled to the niche market. Here we found much of interest including radio control of military targets, robots for film companies, radio controlled concrete placement booms and so on. So from the occasionally dangerous we now moved into the really scary: machines six storeys high, fullsize pilotless aircraft that fly over the horizon, robots that require 24 channels of simultaneous control to do the job (and operators with only two hands), trolleys weighing 80 tonnes, and much more. New technology Now we began to call upon the very best technology had to supply. The new techniques include pulse code modulation (PCM), microprocessor coding and decoding, input noise algorithms, multiple OCTOBER 1989 7 ' I I This remote-controlled model ship was designed by Nikola Tesla in the mid 1890s and relied on a two-carrier system. Another of his designs was submersible. verification of valid data, stringent fail safe requirements and many, many more safety features. Which leads us nicely into the item at the very heart of R/C applications. That is, just how applicable is R/C and the technology involved, to your application? For example, PCM (Pulse Code Modulation) is ideal for industrial control of machinery but can be too rigid for model aircraft work. This sounds a little confusing so let me explain. When we began flying proportional control in 1964, all of the first generation PPM sets had a built in "fail safe". Thus the incoming pulse train was examined and any spurious pulses a hove a limit previously defined as tolerable resulted in the set being shut down, the servos neutralised and the throttle run back to low. All this sounded highly desirable until the practical results came in. Very quickly fail safe was defined as " That circuit which neutralised the controls on the way to the crash". What the designers had forgotten was that the modern aerobatic model aircraft was doom8 SILICON CHIP ed once the controls were neutralised. Cutting the throttle wa s a very big help however and reduced damage significantly. Second generation systems did away with the failsafe system and relied upon random noise to average out the controls, or even the odd snatch of restored control, to keep the aircraft flying until the interference passed. Sometimes the interference did not pass and you just fought the model all the way to the ground but at least you could fight. Once that failsafe locks out, it' s all over, that is unless the model has good inherent stability. Then you just lost it, for it flew away. I once lost a model in Sydney and had it returned from Leeton (in Victoria) months later. Flying through noise and interference was the system used until recently and served us well for over 20 years, giving excellent reliability in use. Someone then r ediscovered the failsaf e when PCM sets arrived on the market and even now after several years, the correct way to use PCM sets is still causing confusion in the model aircraft field. The big difference between the two systems is that PCM uses microprocessors for encoding/ decoding and the old PPM (Pulse Position Modulation) system uses logic. Thus, you must choose your technology very carefully to suit your application. At least the modern PCM set now gives the option to configure your own fail-safe parameters, even to switching it out completely if desired. The situation in industrial control is quite different. As zero deviation. from the norm is required, any interfe rence can be made to shut down the system immediately until the signal is once again valid. PCM is ideal in this application. Wired controls But is R/C the correct technology for your application? There is nothing cheaper and more reliable than a piece of wire (except perhaps two pieces of wire in parallel) and designers of wire guided missiles realise this only too well. The Argentinian Cruiser " General Belgrano" was reportedly sunk from a range of 45 kilometres by two Mark 24 "Tigerfish" wire guided torpedoes. Now that is a lot of wire but it is one way of ensuring the torpedo is not interfered with on its way to the target. As it turned out the report was incorrect and the torpedo was an old Mark 8 non guided. One interesting sidelight here is that the Tigerfish was thought to be unsuitable for sinking a surface vessel. By introducing a radio link, you increase the complexity and cost and reduce the reliability. There are many ways to make the link continued on page 111 This early single-channel superhet receiver was designed for use with motordriven escapements or could be used to drive a single servo. Board Solutions PO BOX 1120 Lane Cove 2066. Telephone: 9065696 Facsimile: 9065222 51/4" disks With any order over $100, 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 XT/ AT switchable o Full AT "enhanced" layout o Compact low profile design 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 Turbo XT Motherboard o Give your old XT a new lease of life with this 1OM Hz motherboard. o Over 2 times faster than PC. 4.77MHz/10MHz swtchable 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 l OOnS RAM Chips normally $16.00 now only $9. 95 VINTAGE RADIO 1, By JOHN HILL Collectables & non-collectables One problem that confronts the vintage radio enthusiast is knowing which radios are worth collecting. Some radios are well worth the effort of restoration but others definitely are not. Collectors of old radios have different ideas as to what is worth collecting and what is not. Personally, I prefer pre-war models although there were plenty of good radios made up until about the early 1950s. I classify valve radios into three categories: very collectable, collectable and non-collectable. Collectability has only been touched on briefly in this column in the past so it's time to delve into the subject more deeply. Of course, the following are purely my own impressions of the subject so readers will have little choice other than to agree or disagree with my comments. Radios in the "very collectable" category are collectable because they are comparatively rare, not because they are particularly good radios. Naturally, the receivers in question are the very early types from the 1920s era. These ancient radios can be lumped together to some extent as they have many things in common. Firstly, they will have squarish, coffin-like cabinets of either timber or pressed steel. They will most likely be battery operated, use a separate loudspeaker (probably a horn speaker), have a complement of triode valves and use a reaction type circuit. There are also a few variations on the theme. Some may be of the console type with turned legs and a built in horn speaker. The odd one may even be an early superhet and operate on AC power. As far as I'm concerned, the "very collectable" category dates from 1923 to 1930. No doubt other collectors would differ on this point and many would perhaps suggest 1928 as a cutoff point for these truly vintage receivers. They could well be right because that was a time of great change, marking as it did the beginning of the superhet era. However, I like to conveniently round things off so I'll stick to 1930. Any radio that is pre-1930 is really a valuable item but finding such a receiver is another matter. Those who own old radios usually wish to keep them. The 1920s-style battery operated receivers present a few problems to restorers as usable valves are hard to come by and most sets no longer have their original speakers. Finding a 90 volt "B" battery is also a problem if one does not have a "B" battery eliminator. Even when fully restored and going, the sound reproduction is so poor they really are a pain to listen to and one soon tires of the thin, metallic sound of a horn speaker. But love them or hate them, going or not going, these early receivers are very collectable and always make an interesting display. Superhet receivers Unusual features such as a "dial a station" dial make this old Astor receiver a collectable item. (Photo courtesy "Orpheous" Radio Museum). 10 SILICON CHIP The "collectable" era, as far as I'm concerned, covers from about Early receivers from the 1920s era are in the "very collectable" category. Shown is a 5-valve Astor of about 1927 vintage. Early loudspeakers are also valuable collectors items. This photograph shows an early Amplion horn speaker of about 1926 vintage. This odd looking early post war Radiola has survived well because of its durable Bakelite cabinet. Bakelite cabinets were far superior to the plastic cabinets which superseded them. 1930 to the mid 1950s or thereabouts. This period is characterised by several things - the total changeover to the superhet receiver, the use of wood veneers as distinct from solid timber, and the introduction of synthetic cabinet materials for the smaller mantle and table models. Many of these old sets restore so well that they outperform some modern receivers to quite a considerable degree. A valve radio may not be anywhere near as power efficient or reliable as a transistorised radio but when it comes to sound quality, some of those oldies are remarkably good. Of course not all of them turn out as well as just intimated. Some sets were lacking a little in design and speaker quality and odd ones were so austere that they never even had automatic gain control. Then as now, there was a range of goods at varying prices, with quality being proportional to price. The 1930s saw the first of the Bakelite radio cabinets and Bakelite proved to be a material that performed well in this role. Bakelite had been in use since the early days of radio where it was used in sheet form, as well as for valve bases, control knobs and other small electronic components. Bakelite is a very long lasting material. There are several Bakelite radios in my collection that are more than 50 years old and despite this considerable time span, their ea binets are in very good condition. Provided a Bakelite cabinet is not dropped it will just about last forever. Age has a dulling effect on Bakelite cabinets but the original sheen can be easily restored by rubbing down the surface with a metal polish such as Brasso, or an automotive paint cutting and polishing compound. One of the big advantages of Bakelite is that it is impervious to moisture. Often one sees an otherwise good timber cabinet radio with OCT0BER1989 11 This particular model HMV cabinet always cracks above the hot rectifier and output valves. Despite this, the receiver still works well. This Radiola 5 is a popular receiver from the mid 1950s. Although the author classifies it as "uncollectable", it is nevertheless quite a good receiver. the plywood separated and the outside veneer blistered, lifted or broken away. With the exception of radios with badly damaged timber cabinets, most receivers from the 1930s and 1940s survive the years fairly well. Generally speaking, the majority of sets manufactured in this era were well made and can be restored to a high standard. If properly restored, they will continue to work for many years to come. Bakelite vs. plastic The last category of receivers is what I call the "non-collectables". 12 SILICON CHIP The radios in this category were usually made in the 1950s or early 1960s, have plastic cabinets and have very little aesthetic appeal. No doubt some readers may object to my classification but I'm sure a lot will agree with me wholeheartedly. Compared to pre-war radios, radios from the 19 50s and 1960s were built to a price rather than to specifications. Competition between manufacturers must have been intense at the time and many cost cutting exercises are fairly obvious when these radios are examined closely. In simple terms, the last generation of valve radios were fairly cheap and nasty. These radios were not all bad, however. From a performance point of view they went OK and were generally a little more reliable than their earlier counterparts. But (and it's a big but), from a collector's point of view, they simply lack the appeal of the older pre-war models. Plastic had almost completely taken over from timber and Bakelite and this in itself makes them far less attractive. Now readers have taken me to task before about this Bakelite and plastic technicality, claiming that both materials are plastics. Of this fact I'm well aware, but as a collector of old radios I view these supposedly similar materials quite differently. Bakelite is a thermosetting type of plastic that is formed under heat and pressure and when cooled it stays that way - permanently! In other words, once formed into a shape it cannot be remelted or reshaped. Plastic radio cabinets (as distinct from Bakelite) are made of various thermoplastic materials which can be remelted and reshaped after they have been initially formed. It is this type of plastic that has proven to be relatively unsuitable for radio cabinets when viewed in a long term perspective. Hence I refer to Bakelite and plastic as being two different materials. Technically speaking, they can be lumped together under the broad heading of "plastics" but as far as I'm concerned, Bakelite and plastic are not to be compared because they are so different. One lasts; the other does not! Early radios also had metal or Bakelite dial escutcheons that usually survived the years without casualty. Their plastic counterparts haven't done so well, even though only half the age. Likewise with control knobs. The old Bakelite variety often had brass centres and hardened steel set screws to secure them to the shaft. Even the cheaper ones without the brass centres gave very little trouble. On the other hand, how many readers have experienced the frustration of removing old plastic control knobs, only to have them FIX-A-KIT Kit Repairs - $1 5 per hour. Normal Rate - $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. Radios with timber cabinets make very worthwhile collectors' items. This 4-valve HMV receiver uses several different timbers and has been fully restored. separate into many pieces. The centre piece frequently pulls away from the rest of the knob. The plastics used in the radios of 30-40 years ago were quite OK at the time. In fact, some of those receivers appear to be surviving reasonably well whereas others simply fall apart. It would be interesting to know their past history. Maybe the ones exposed to years of sunlight crack up sooner than those which lived more sheltered lives. Heat plays a significant role in the life of a plastic cabinet and many such cabinets develop cracks in particular places; usually over the hot rectifier and output valves. In some instances, the heat even softens and deforms the ea binet. Little Nipper The HMV "Little Nipper" was a popular radio for many years and I have picked up about a dozen or so since I started collecting. Out of that number, only one has a crack free cabinet. Although I consider these late model radios as noncollectable, I have restored this particular Little Nipper because it is one of the few good examples of that model. I recently wrecked an HMV tablegram only to find that the radio unit was nothing more than an upgraded Little Nipper. The upgrading bit amounted to the addition of shortwave, something I have yet to see on a Little Nipper mantle set. Now I might knock these so called non-collectable radios a bit but that tablegram chassis has turned out to be one of my favourite radios. After giving it the full treatment, including a 3.5mm mono socket to accept an 8-inch wall mounted speaker, the result was quite amazing. It might not be much to look at but it performs really well. This is the unfortunate aspect of this last generation of valve radios. The radios themselves were OK; it was the plastic cabinets they were placed in that is the main cause of the trouble. They simply weren't designed with longevity in mind and do not stand up to the passing of time as do the older receivers. Although I refer to late model valve radios as non-collectables, I must confess that I also have a plastic cased "Astor Mickey" and a mid 1950s Radiola. The occasional good one is still worth preserving. However, if ever I have a sale, it will be the non-collectables that go first. Well, we have run out of space again which is a good thing really because I have become depressed talking a bout all those noncollectable radios . I will have to go into my den and have a look at my collectables in order to get myself all enthused again so I can write something for next month. ~ HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment. (02) 633 5897 Unit 4, 62 Great Western Highway, Parramatta, NSW 2150. Trading hours: Barn to 3pm Monday to Friday. D.DAUNER ELECTRONIC COMPONENTS WE STOCK A WIDE RANGE OF ELECTRONIC PARTS for • Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST Nl::OSID 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. OCT0BER1989 13 Prices lili.e you'd got a PC GAMES PORT JOYSTICK CATACJOY These Joystick are ruggedly constructed to withstand the rigours of enthusiastic playing. • Easy fingertip control of the "fire" button. • Trim adjustments on both axes. • Automatic spring return on both axes for autocentring • Terminates in the games port standard 15 pin male connector. GET50%MORE HARD DISK CAPACITY WITH RLL CONTROLLER only$30 TICK TOCK CARD CATDCAHR 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 DISKDRIVE PARADISE NEW!! PC/XT HARD DISK controller CAT DC-2200 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 up to 1:1. • Data transfer rate of 660KBytes/Sec • 50% more formatted capacity from the sarne 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. !~1005 This card suits all IBM PCl)('I's' 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.) • Games 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 CATPOWER6P only$492 14 11 AMBER or GREEN MONITOR CAT. ACMG only$249 Miniscribe model 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 5¼" 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. 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NEE2 CAT NEEi 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 CAr. 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. • 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. 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If so, you should think seriously about installing a cord and plug more suited to the job. These days many electric radiators have plugs and cords which are just not suitable for the task. We're talking particularly about appliances rated at between 2000 and 2400 watts and which draw between B and 10 amps from the mains. If they're used on the lower power settings, they're OK but when you switch up to full power on those cold winter nights, the cord and plug starts to go a bit limp literally. Two of the photos accompanying this article show a particular type of plastic 3-pin plug which is commonly fitted to the cords of electric radiators. It is nominally rated at 10 amps [as indicated by the lOA marking between the pins) but when the appliance is drawing this current, the plug gets very hot - so much so, that the plastic starts to melt. This shows up where the cord enters the rear of the plug [Fig.1) and around the brass Active and Neutral pins (Fig.2). Part of the problem is that the pins are fabricated out of thin brass and thus have a higher resistance to the current flow than plugs with solid brass pins. When you are drawing 10 amps, even quite a small resistance will result in a lot of power dissipation. Say, for example, that the total resistance associated with the pin of a power plug is only 50 milliohms or 0.050 [this figure includes the contact resistance plus the resis16 SILICON CHIP tance of the pin itself). With 10 amps flowing, there will be 5 watts dissipated. With two pins having the same resistance, the total power dissipated in the plug will be 10 watts. Now 10 watts of heat dissipated in a plug is enough to make it stinking hot. It certainly is enough to melt it. So you can see that resistance must be avoided as much as possible. Often combined with these puny plugs is a puny power cord which also has a nominal rating of 10 amps. The operative word here is "nominal". As far as we're concerned, it doesn't mean 10 fairdinkum, full-on continuous amps; it means pony sized amps which probably come out of the same labs that used to do the exaggerated horsepower tests for cars. Such cords are OK if used for a short period but are not adequate for radiators that are used at maximum setting for hours on end. These puny 10-amp power cords have a plastic sheath with an overall diameter of about 8mm. When they are running at 10 amps they get quite warm and limp. If they are running over a shag pile carpet or are in any situation where air circulation around the cord is poor, the cord will get surprisingly hot. Some blower type radiators are of all plastic construction and so are double insulated. This means that they have a 2-core flex which is even thinner in overall diameter at only 6mm. In some situations, we believe these cords and plugs get so hot that they could eventually lead to a fire. In our opinion, they should not be approved by the electrical authorities for 10 amp applications. We reckon they're OK for any appliance drawing up to 5 amps on a continuous basis but for anything more than that they are not suitable. Replace the cord and plug Fig.1: carefully inspect the rear of the plug. If the insulation is starting to melt, the plug should he replaced. There is only one type of 3-pin plug which is suitable for an appliance which draws 10 amps and this is the HPM Cat. 99. This is not made of soft plastic but hard white phenolic. It has solid brass pins and a large cord entry at the rear. Heat will not distort these plugs. So even if you have poor connections inside the plug, the plug will not melt. And there is only one type of Problems? ... and you don't have our .120page catalogue . .. Fig.2: the pins on plastic plugs used at high current can loosen as the plastic melts. Here, the active pin (at the end of the screwdriver blade) has worked quite loose, creating a hazardous situation. 3-core flex which we would recommend. It is rated at 15 amps continuous and has an overall diameter of 10.5mm. It is labelled 301.25mm and 1.5 sq mm. What this means is that the three cores are each made up of 30 strands of 0.25mm copper wire which gives an overall conductor cross section of 1. 5 sq mm. Why go for a 3-core flex which is rated at 15 amps'? There are two reasons but they add up to the same result - the cord won't get hot. The first reason is that this heavy duty cord has thicker insulation and is therefore less likely to kink and strain the internal conductors. Second, the voltage drop along the cable for a given current is a lot less than in the so-called 10-amp cables. This means more voltage in the radiator and less heat in the cable. cable. That way, if you decide that it looks too hard to mess about with, you can let an electrician do the job. By the way, many radiators don't have a long enough power cord - if you decide to replace the cord you can make it longer. Let's assume now that you have . purchased two or three metres of the recommended cable and the HPM plug. Remove the existing power cord from the radiator and note the length of the Active, Neutral and Earth wires. Depending on how the cord is installed, these will probably have different lengths. You must duplicate these. The longest wire determines how much of the outer insulation must be removed. Stripping the cable When you buy your HPM Cat. 99 plug it will come with instructions on how to wire it and how much to strip the cable. That's OK for the plug end but what about where it terminates inside your radiator'? What you have to do is to duplicate the connections inside your radiator. In fact, it would be a good idea to have a look at these connections before you go to purchase any Fig.3: the HPM Cat. 99 plug is the one that we recommend for 2400W radiators. It has solid brass pins and will not distort due to heat build-up. 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 converters . . . 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 OCT0BER1989 17 Fig.4: a Stanley utility knife with a sharp blade is the recommended tool for stripping mains cable. Fig.6: use the Stanley knife to strip about 12mm from the ends of the inner cores but be careful not to nick the individual strands of wire. The inner cores should duplicate the lengths of those on the original cable. Fig.5: be careful not to nick the insulation of the inner wires. If you do, cut off the damaged section and start again. Naturally, you have to strip both ends of the cable, one end to suit the radiator and the other to suit the plug. But many people are not sure how to go about stripping cable. The recommended tool is a Stanley utility knife with a sharp blade. The idea when stripping the outer sheath from the flex is to make sure that you don't nick or cut the insulation of the three individual insulated wires. If you cut the insulation of these, you can't safely wire the plug. A cut in the insulation can eventually lead to a flashover in the cord and perhaps even a fire. 18 SILICON CHIP So if you do nick one of the three cores, you must cut off the damaged portion and start again. Fig.4 shows how to start stripping the cord. You bend it over and carefully cut around half the circumference but don't go deeper than 1mm. As you bend it, the cable covering will then split open as shown in Fig.5. Having done that, bend the cable over in the other direction and cut it in the same way. The outer covering will then slip off. Note that if you have nicked one of the inner cores it will be immediately visible as you bend it over. Now strip about 12mm from the inner cores as shown in Fig.6. Again, go easy with the knife otherwise you will nick the individual strands of wire. As you can see in Fig.6, you just roll the wire along the blade edge so that it penetrates but doesn't cut through. Then by bending the core back and forth, the insulation will break and can be slid off. Terminate the cable inside the radiator first. Make sure that all connections are secure and that the cable is anchored exactly as before. Incidentally, if the radiator is a double-insulated appliance, do not connect the Earth wire - just clip it off. You can now terminate each of the three wires on the mains plug. Don't forget to slip the plug back over the cable before you terminate the wires. There is nothing more annoying than wiring up a mains plug and finding you have left the plug cover on the table, or on the floor! Now before you apply power, get out your multimeter and switch it to a low Ohms range. Check that you have continuity between the Earth pin of the mains plug and exposed metalwork on the radiator. Check that you have continuity between the Active and Neutral pins. If the radiator has a switch you will have to move this to the on position to obtain a reading. If the radiator has a rating of 2400W, its resistance in the highest heat setting will be about 240. Finally, switch your multimeter to the highest available Ohms setting and check that there is an open circuit (ie, no reading or no pointer deflection) between the Earth pin on the plug and either the Active or Neutral pins. That done, your radiator can be put back into use. One further point: if the power plug still gets hot when the radiator is at the maximum heat setting, then the mains power point itself may be a little tired and may need replacing. ~ Bits like this . • • BC 546, 547, 548, 549, 557, 558, 559 Transistors ...... . . 1-99 . . ........... .... $0.15 ea 100+ .......... .. . ... $0.10 ea BC327,337 Transistors .... .. . 1-99 ................ . $0.20 ea 100+ .... . ... . ....... $0.15 ea Male & Female and covers 9-way, 1S-way, 2S-way ...... ..... .. ~.00 ea ~~ Voltage Regulators & linear IC's VOLTAGE REGULAlORS: Code 7805 7809 7812 7815 7824 7905 7906 7912 7915 7918 7924 1-9 10+ $0.80ea $ 0 .80ea $ 0.80ea $0.80ea $0.80ea $ 0.80ea $0.80ea $0.80ea $0.80ea $0.85ea $0.80ea $0.70ea $0.70ea $0.70ea $0.70ea $0.70ea $0.70ea $0.70ea $0.70ea $0.70ea $0.75ea $0.70ea '' LINEAR IC's: Code 324 339 393 555 1-9 10+ $0.46ea $0.53ea $0.46ea $ 0 .37ea $0.37ea $0.42ea $0.37ea $0.34ea Portasol gas powered soldering iron t39.9Sea Portasol Pro gas powered ~ soldering kit f 79 • 95 ea Hakko 926 20 watt hand• held soldering iron. 50 watt soldering station. ~s9 TI Hakko 7008 40 watt solder/desolder station ~020 Only one p ace to go. . . ,..----. Novocastrian Electronic Supplies Pty. Ltd. P.O. Box 87, Broadmeadow, N .S.W. 2292 Phone: (049) 62-1358 Fax: (049) 62-2005 ) J 01 LI:\ · (008) 02-5942 - The postage rates shown cover basic postage only. Any spec ialised freight requirements will be charged at di fferenl rates. Prices subject to change without notice. Prices include Sales Tax. * * Mail or Telephone Orders Welcome Bankcard - Mastercard - Visa - accepted Delivery Rates: Orders: Postage: $1 - $9.99 $2 .00 $10 - $24.99 $3.00 $25 - $49.99 $4.00 $50 - $99.99 $5.00 $100+ $7.50 FM radio intercom for IDotorbikes This motorcycle intercom provides communications between rider and pillion passenger or between riders on separate bikes. Because it is a 2-way radio system, it allows you to communicate with more than one rider at a time and can even tune in your favourite FM station when not being used in the intercom role. By JOHN CLARKE Motorcycle intercom systems have always been popular but until recently, have been restricted for use between rider and pillion passenger only. Communication between separate bikes has been left to special sign language such as sticking both arms out to ask "shall 20 SILICON CHIP we turn left or right?" and other more subtle communication forms. These sign languages are often misinterpreted. The above rider with the outstretched arms was later to discover why he received no response - the following rider assumed he was just showing off. This problem can be overcome by using a radio intercom. These are available commercially but cost a fortune. With that in mind, we set about designing a unit that you can build yourself and save quite a lot of money. Before going further though, we should point out that this is not really a project for the beginner. There are a number of coils to be wound during construction and the PC board is fairly closely packed with parts, so you will need to have some experience with kit construction to successfully tackle this project. Also, depending on where the kitset suppliers have sourced their parts, one of the integrated circuits may be a surface mount type. These are a lot smaller than conventional ICs and so are harder to mount. It's not just a matter of assembling all the parts either. You must also be able to follow the alignment instructions. Have we put you off? We are sure we haven't. Main features The SILICON CHIP Radio Intercom has a number of features which are not normally found in intercom systems. Because it is a radio intercom, it can be used for communications between riders on separate motorcycles. And because the intercom transmits and receives on the · same frequency, any number of riders can listen in to a transmission at the same time (provided they also have intercoms or FM receivers). In use, the Radio Intercom normally operates in receive mode so that it can pick up any transmissions from other riders. But when you speak into the microphone, the intercom automatically switches to the transmit mode due to its voiceoperated switching (VOX) circuitry. This feature greatly increases safety and convenience since it eliminates the need for a PTT (press-to-talk) switch. As with a CB radio, only one person can transmit at any one time. If two people try to speak at the same time, nothing will be heard by either party since the receiver is switched off during transmission. This means that some form of agreed procedure must be followed when using these units. For example, most radio operators use the word "over" to indicate the end of transmission and that the other party can speak. Apart from that, the unit operates very much like a CB radio except that it operates in the commercial FM band (88 to 108MHz) and on one channel only. Noise cancelling mikes Because of the high ambient noise from a motorcycle, the SILICON CHIP intercom uses special noise cancelling microphone circuitry. This involves using two separate microphones which are connected so that noise signals are largely cancelled by the following circuitry. In practice, the microphones are set up so that the rider speaks only into one of them and this provides the signal to be transmitted. All the circuitry fits neatly into a compact plastic case from Dick Smith Electronics. When not used in the intercom role, the unit can be used to tune your favourite FM station. Because the intercom operates in the commercial FM band, it can also be used as an FM radio receiver. Tuning is by means of a small thumbwheel on the front panel. To use the unit as an intercom, the thumbwheel dial is simply set to the 88MHz position (at one end of the dial travel). A small slider switch adjacent to the thumbwheel selects between FM, Intercom and Off. We don't recommend that you try tuning the unit while the bike is in motion, however. That would be dangerous to say the least. The unit should be set for one mode or the other before starting off and should only be tuned when the bike is stopped. Handy case As can be seen from the photographs, all the electronic circuitry is housed in a small plastic case. This can be easily fitted into the pocket of a motorcycle jacket and the short wire lead antenna clipped to the jacket collar. A coiled cord connects the intercom to the helmet which is modified to accommodate a miniature loudspeaker and the two electret microphones. Power for the intercom is derived from three AA cells, thus making the unit completely portable. Other applications Just because we have described this project as a motorcyle intercom OCT0BER1989 21 FM RADIO INTERCOM - CTD does not mean that it is suitable only for this use. We invisage that it would also be suitable for use by hang glider pilots, power boat racers (for communication between the crew), rally car drivers, in helicopters and open-cockpit and ultra-light aircraft. How it works The Radio Intercom is built around four ICs, all of which are low voltage, low current devices suitable for battery operation. On the receive side, we used a Philips · TDA7000 IC which is virtually a complete FM radio receiver on a single chip. Its output drives a National Semiconductor LM831 power amplifier IC which in turn drives the loudspeakers (or headphones). The transmitter section is based on a Rohm BA1404 stereo transmitter IC (the same as used in our Stereo Minimitter project in the October 1988 issue). An LM324 quad op amp and three transistors are used for microphone amplification and for the voice operated switch (VOX). Fig.1 shows the circuit details. We'll start with the microphone amplifier and VOX switching which is built around IC1. Differential microphone amplifier Both voice and noise signals are picked up by two small electret microphones mounted inside the motorbike helmet. These are supplied with power from the + 4.5V rail via separate 1.2k0 resistors. The signal from each microphone is AC coupled to signal attenuators VR1 and VR2 and then fed to the non-inverting inputs of ICla and IClb. ICla functions as a non-inverting buffer amplifier with a gain of 1 + 1/47 and amplifies the signal from the wiper of VR2. The output appears at pin 7 and is coupled via a 1kn resistor to the inverting input (pin 2) of IC1 b. IClb is wired as a differential amplifier. It functions as an inverting amplifier with a gain of - 47 22 SILICON CHIP for signals from ICla and as a noninverting amplifier with a gain of 48 for signals from the wiper of VR1. Note, however, that the overall gain for signals from the wiper of VR2 is - 47(1 + 1/47) = - 48. This means that there will be no output from IC1 b when the two microphone signals are the same and thus noise signals common to both are cancelled out. On the other hand, speech signals will be amplified since the microphones in the helmet are arranged so that only one is near the rider's mouth. DC bias for ICla & IClb is derived via VR1 & VR2 from a 15k0/10k0 voltage divider across the supply rails. This voltage divider also provides DC bias for op amp stage IClc in the VOX circuit. The VOX circuit IClc is wired as a Schmitt trigger with its inverting input (pin 9) biased via a 47k0 resistor. A 3.3k0 resistor at the non-inverting input and a 220k0 positive feedback resistor set the hysteresis of the Schmitt trigger. This stage squares up the output from IC1 b and couples the resulting square wave signal to a charge pump circuit consisting of a 4. 7µF capacitor, diodes Dl and D2, a 47µF capacitor and a 4 .7k0 resistor. When a speech signal is received, the 47 µF capacitor is rapidly charged towards the + 4.5V supply rail. Following the charge pump circuit is another Schmitt trigger stage based on ICld. This stage compares the voltage across the 47µF capacitor with the voltage at its inverting input as set by the 100k0/10k0 voltage divider. The 150k0 feedback resistor and the 10k0 resistor in series with pin 12 set the hysteresis level of the Schmitt trigger. This hysteresis is necessary to ensure that pin 14 of ICld switches cleanly from one state to the other instead of dithering about at the threshold point. The output of ICld drives transistors Ql and Q2. When the output is high (ie, when speech is present), Ql and Q2 are turned on via 6.8k0 current limiting resistors. This does two things. First, when Ql turns on, it powers up the transmitter (IC2) by connecting the ground rail of this stage to the negative line from the battery. At the same time, when Q2 turns on, it turns off Q3 which then disables the receiver and audio amplifier (IC3 & IC4). Conversely, when the output of ICld is low, Ql and Q2 are off and the transmitter (IC2) is disabled. Thus, when no speech signal is present, Q3 turns on and powers up IC3 & IC4. The .OlµF capacitor between the collectors of Ql & Q3 provides RF grounding for the circuits at all times. Transmitter stage The output of the microphone differential amplifier !Cl b is coupled to the modulator input (pin 12) of IC2 via a voltage divider (5.6k0 & 4.7k0) and a O.lµF capacitor. The .001µF capacitor filters any RF on this input. IC2 is a Rohm BA1404 stereo FM transmitter IC but is used here in mono mode only. Because of this, only the RF section of the IC is used in this circuit. Those sections of the chip associated with stereo signal multiplexing are simply left unused. No 38kHz crystal is required. The circuit operates by mixing the audio signal on the modulation input (pin 12) with a local oscillator. The resulting RF output signal on pin 7 is then fed to a tuned filter stage and used to drive the antenna via balun L5. The oscillator output at pin 10 is tuned using L2 and a 39pF NPO capacitor. Similarly, the RF output at pin 7 is tuned using L1 and the series 56pF and 120pF NPO capacitors. These capacitors are connected in series so that an antenna can be connected at their junction without loading the tuned Fig.1 (right): the complete circuit ► diagram. ICla & IClb function as a differential amplifier for the microphone signals, while IClc, ICld & Ql-Q3 form a VOX circuit. IC2 is the transmitter stage, IC3 the FM receiver & IC4 the audio output stage. ~ t,.,') CX) '° '° ....... :::0 tri t:c 0 '-l 0 n 3 0 •• .0 1_;i 1k , _.j _ &M324 7 lk T1 • NPO * NPO • 56pF ■: VC1 20-60pFJ~ ELECTRET w ~ .,. ~ ECTRET MICS 100 + 47k~ r1 / ,c 10k 1 MUTING 2NO I 6 +---'tVCO 5 V+ * G,.:Jg 4 LOOP FILTER .0033 12 18 u ls ~ ls !;;; B MIXER GNO g •CERAMIC 16 GNO 15pF ---< 47k ■■ 0.1 •· * + 1 AF OUT MIXER RF IN 0 IF FILTER I~ .ot22 :,: 2 14 L4 13 4.71! 39 pF * NPO: = * 18k 47 F N~O == rgt VR3 ■■ * ~-~ .t1: = K VOLUME ,_ .0039 == .,__ I I I II 11 •~ii ,1 ., :: ••~If +2. 5V * :· " + .,. - - .,. ',:; VANTENN~ ~K - 22k \2,1 22011 - + 10 : = 12 . INTERCOM 6.8k 6.8k ) 220n 10: = + AV(2) 2 47 : ;_ + BYPASS 16 IC4 LM831 OUT 1 BRIDGE 1 · . t1:: _ I E 5 ::4 811 + m::- +4.5V VIEWED FROM BELOW E • • • C B 0 .,.E _ Bll + + ~eli=~ - 47 ~F. - o 33: : LOUDSPEAKERS OR HEADPHONES V02F-- - - - +--e,a--+--<e-- - _ , 8 VOl 10 I 12 BSP GND BSP ~6 E... 9 +::- ------+-. _ S1b • Ol 8C548 . . - - - - - C B • ~ B ~c 03 BC548 :1. 4.5V½ iP INTERCOMe FM... OFF FMi OFF . . - Bro:: C 02 BC548 2 2k . 2.5T 0.8mm ECW ON 5mm FORMER F29 FERRITE SLUG 2T 0.8mm ECW ON 5mm FORMER F29 FERRITE SLUG 2.5T 0.8mm ECW ON 5mm FORMER F29 FERRITE SLUG 6.5T 0.8mm ECW 5mm INSIDE DIAMETER, 5mm LONG NEOSIO F29 BALUN FORMER 2 BIFILAR TURNS O.Bmm ECW . _ - ,..: 22I V IT ·--~ 14 t----. 150k IC1d ----11""3..1 _·-/ -.:- 22k r o *l L1 L2 L3 L4 L5 - 100k 10k 13 IN- (1) AV(1) 15 14 ,...... IN +(1) . .J,; . f 47 1 ....---, IN+ (2) 1N4~~8 ... -- K 02 1N4148 Al:;\K ,Gv +!·;_ TRi~~~IT€9 8 A ~ MOTORCYCLE RADIO INTERCOM 11 IF FILTER ~ .0033:: • NPO:: 15pF 120oF.l .,.11 .,'j(~•NPOh L1 56pF • NPO L' !r] 10 / -;..,_ci + 9 ~4 IClc 220k .Ol _1t ~ :J * NPO: = 15 12 CURRENT IF SOURCE LIMITER o*1:: 15tpF== IC3 TDA7000 ~ lg 2I 17 ls !;;; 15 ::~== IC2 RF OUT 7 BA1404 osc 10 4 MOO IN 22~pF: = 33~pF: : .01:: 1ST INTEGRATOR ..---..---- INTEGRATOR * ~t.J .01 * • • .001• ■ 0*1 :: 0.15== 4.7k 5.6k .,. ,.•_.,_.- __________________, 22I"".. 01 ~= _e:--:: T- 2~ 47k ICla >,_."'""W.-+-"1- _~ v -+-V 1 1b 5 R2~---+-5 Dk + ·- ; _ / ' 15k *,:: 3.3k O.l ,______.,__-411---<11-----------------il-----_. L - - - - - - -- l 2 .,. 471 + V R 1 ~ - - + - - - - + - - - - + - - - - - - - - -.....' 2 R 50k •• ::> 33 F" ■ ::> p ■ ■ tj + 1.2k -~15 ~ < 4701) -------~~-------------------------.------------......---------------,---.1 l ls1, A great deal of the circuitry operates at RF so keep all leads as short as possible. The circuit board is mounted on two plastic pillars on the case bottom and secured using self-tapping screws. Note the metal shield between coils L1 & L4. circuit. This means that the overall capacitance across 11 is about 39pF. The three .OlµF capacitors between the + 4.5V rail and ground provide decoupling for the circuit. Note that the positive supply for, IC2 is fed via LED 1 which lights whenever a transmission is in progress. That's handy but the real reason for the LED is to drop the supply to IC2 by 2V so that it is within the specified 1-3V. FM receiver IC3 (Philips TDA 7000} and its associated components form the FM receiver. The TDA7000 is virtually a complete FM tuner on a single chip and is easy to get going since only the local oscillator requires adjustment during alignment. All the other components are fixed. Incoming signals are picked up by the antenna and fed to the RF in24 SILICON CHIP put (pin 13} of IC3 via balun 15 and a bandpass filter consisting of 14 and two NPO capacitors (39pF & 47pF). This filter covers the entire FM broadcast band and does not require any adjustment . The .0022µF capacitor on pin 14 provides RF grounding for the internal mixer circuitry. IC3 functions pretty much as a conventional superheterodyne tuner. This means that the incoming signal is mixed with a local oscillator signal to produce an intermediate frequency (IF). The IF is then filtered to remove any mixer artifacts and demodulated to produce an audio signal. There's just one deviation from normal practice. The majority of FM receivers use an IF of 10. 7MHz whereas the TDA7000 uses the very low intermediate frequency of 70kHz. The advantage of such a low IF is that it can be filtered with standard active op amp filter circuits instead of coils or ceramic filters. Normally though, a low IF results in really bad distortion when it is used with wide deviation FM; ie, the normal broadcast FM which has a maximum deviation of ± 75kHz. This is why we used the TDA7000 instead of the Motorola MC3362 narrowband FM receiver which was featured in our March 1989 issue. The TDA7000 manages to demodulate wideband deviation of up to ± 75kHz while only having a 70kHz IF by a special bit of skullduggery. What happens is that the recovered audio is actually used to modulate the local oscillator so that the received FM deviation is always less than ± 15kHz. In effect, the recovered audio signal has been compressed to reduce its dynamic range. In a hifi FM receiver this would not be desirable but in this application, on a noisy motorbike, it is ideal. Distortion is kept reasonably low too, and is less than 2.3% at ± 75kHz deviation. 13, VCl and the fixed 56pF and 33pF capacitors form the tuned circuit for the local oscillator. By varying VCl (and thus the oscillator frequency), the receiver can be tuned over the entire FM broadcast band from 88-108MHz. The remaining capacitors on the circuit are used for decoupling, filtering and demodulation. To prevent instability, a 4. 70 resistor is included in series with the positive supply rail. The audio output signal appears at pin 2 where the necessary 50µs de-emphasis is provided by the 18k0 resistor, the .0039µF capacitor and volume control VR3 (50k0). Audio amplifier The output from the volume control is fed to pin 3 of IC4 which is a National Semiconductor LM831 low voltage dual power amplifier. For this application, the two amplifier stages have been connected in bridge configuration (ie, the two amplifiers drive the loudspeakers in antiphase ). This eliminates the need for output coupling capacitors and increases the available power output to about 400mW. The 2200 resistors at pins 2 & 15 of IC4 set the gain of each amplifier stage to about 54. The audio output signals appear at pins 8 and 10, with each output driving one side of the loudspeaker load. In addition, the outputs are connected to the bootstrapping inputs at pins 5 & ,12 via 47 µF capacitors. This gives the absolute maximum peak-to-peak swing from the amplifier outputs. The amplifier outputs at pins 8 & 10 drive two 80 loudspeakers connected in parallel to give a 40 load. In addition, a 0.33µF capacitor has been included between each amplifier output and ground as a stability measure. Mode switching Switch S 1 is used as an on/off switch and also selects between the two operating modes (FM or Intercom). When FM is selected, power is supplied to the FM receiver and audio amplifier ICs only (IC3 & IC4), PARTS LIST 1 PCB, code SC06111891, 82 x 92mm 1 front panel label, 90 x 43mm 1 dial scale label 1 plastic case, 95 x 45 x 145mm, DSE Cat. H-2503 1 microphone cable with 4 conductors plus one shield, Tandy Cat. 278-355 1 miniature tuning gang, DSE Cat. R-2970 1 Neosid balun transformer core, type 1050/2/F29, DSE Cat. L-1352 3 Neosid 722/ 1 coil formers (L 1,L2 ,L3), DSE Cat. L 1010 3 Neosid F29 slugs, DSE Cat. L-1307 1 DP3P slider switch, DSE Cat. S-2030 2 electret microphone inserts 2 miniature 80 loudspeakers 1 4 x AA square battery holder 3 1.5V AA cells 1 battery snap connector 7 PC stakes 1 cord grip grommet 1 6.5mm stereo line socket 1 6.5mm stereo plug 1 6 .5mm mono line socket 1 6.5mm mono plug 1 650mm length of 0.8mm enamelled copper wire 1 7 50mm length of stiff hookup wire for antenna 1 tinplate shield, 22 x 12mm 2 1.6mm dia. x 4mm screws 2 2mm dia. x 3mm screws 2 50k0 trimpots 1 50k0 log potentiometer Semiconductors 1 LM324 quad op amp (IC 1) 1 BA 1 404 Rohm stereo FM transmitter (IC2) 1 TDA7000 Philips mono FM radio (IC3) while the transmitter stages (ICl & IC2) are disabled. In the Intercom mode, the + 4.5V supply rail is connected to both the transmitter and receiver stages, with the ground rails now switched by the VOX circuitry as described earlier. Construction Most of the parts for the Motorcycle Radio Intercom are mounted 1 LM831 dual audio amplifier (IC4) 3 BC548 NPN transistors (01-03) 2 1 N4148, 1 N914 signal diodes (D1 ,D2) 1 3mm red LED (LED 1 ) Capacitors 1 4 70µF 1 OVW PC electrolytic 1 1 OOµF 16VW PC electrolytic 5 4 7µF 1 6VW PC electrolytic 2 22µF 16VW PC electrolytic 2 1 OµF 16VW PC electrolytic 1 4 . 7µF 16VW PC electrolytic 2 0.33µF 16VW PC electrolytic 1 0 .15µF metallised polyester 6 0.1 µF monolithic ceramic 2 .015µF metallised polyester 5 .01 µF ceramic 1 .01 µF metallised polyester 1 .0039µF metallised polyester 2 .0033µF metallised polyester 1 .0022µF ceramic 1 .001 µF ceramic 2 330pF ceramic 1 220pF ceramic 1 180pF ceramic 1 1 50pF ceramic 1 120pF NPO ceramic 2 56pF NPO ceramic 1 4 7pF NPO ceramic 2 39pF NPO ceramic 1 33pF NPO ceramic 2 1 5pF NPO ceramic Resistors (0.25W, 5%) 1 220k0 1 5.6k0 1 150k0 1 4.7k0 1 100k0 1 3.3k0 3 47k0 1 2.2k0 2 22k0 2 1.2k0 1 18k0 2 1 kO 1 4700 1 15k0 2 10kQ 2 220Q 2 6 .8kQ 1 4 .7Q on a small PC board coded SC 06111891 (82 x 92mm). This is housed in a clip-together plastic case measuring 95 x 45 x 145mm. The completed prototypes were given a professional finish by fitting Scotchcal labels to the front panels and thumbwheels. Before installing the parts on the PCB, it is necessary to enlarge some of the holes and do some work on the case. Fig.2 shows the locations OCT0BER1989 25 POLYESTER AND CERAMIC CAPACITORS □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ No. 6 2 6 1 2 1 1 2 1 1 1 1 2 1 2 1 2 Value 0 .1 uF .015uF .01uF .0039uF .0033uF .0022uF .001 uF 330pF 220pF 180pF 150pF 120pF 56pF 47pF 39pF 33pF 15pF IEC 100n 15n 1 On 3n9 3n3 2n2 1n0 330p 220p 180p 150p 120p 56p 47p 39p 33p 15p EIA 104K 153K 103K 392K 332K 222K 102K 331K 221K 181K 151K 121K 56K 47K 39K 33K 15K Fig.2: this diagram shows the locations of all holes on the PCB that are larger than 1mm in diameter. The holes for the three coil formers (D) also require matching keyways. RESISTORS □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ No. 1 1 1 3 2 1 1 2 2 1 1 1 1 2 2 1 2 1 Value 220k0 150k0 100k0 47k0 22k0 18k0 15k0 10k0 6.8k0 5.6k0 4.7k0 3.3k0 , 2.2k0 1.2k0 1k0 4700 2200 4.70 of all holes on the PCB that are larger than 1mm diameter. Follow this diagram carefully and drill all holes as shown. Note that the holes for the 5mm coil formers also require small matching notches. These can be made using a small file so that the formers are a tight fit. 26 SILICON CHIP 4-Band Code red red yellow gold brown green yellow gold brown black yellow gold yellow purple orange gold red red orange gold brown grey orange gold brown green orange gold brown black orange gold blue grey red gold green blue red gold yellow purple red gold orange orange red gold red red red gold brown red red gold brown black red gold yellow purple brown gold red red brown gold yellow purple gold gold 5-Band Code red red black orange brown brown green black orange brown brown black black orange brown yellow purple black red brown red red black red brown brown grey black red brown brown green black red brown brown black black red brown blue grey black brown brown green blue black brown brown yellow purple black brown brown orange orange brown brown brown red red black brown brown brown red brown brown brown brown black black brown brown yellow purple black black brown red red black black brown yellow black blue brown The case must be modified by filing down the inside sections of the clip pillars on the base so that the PCB will sit directly on the mounting pillars (see photo). Try mounting the PCB inside the case and you will quickly understand what needs to be done. In addition, the two catches on the lid must be filed off so that the clip pillars can slide past the PCB when the lid is attached. To understand what is required, temporarily mount the PCB in the base and then try putting the lid on. The front panel also requires drilling and filing to accommodate the thumbwheel dial, volume con- Fig.3: begin construction of the PCB by installing all the parts as shown here. Be sure to orient all parts exactly as on the diagram and note that the .01µF bypass capacitor for IC3 is mounted on the copper side of the board. Do not use IC sockets as these could . upset the circuit performance. Fig.4 (below): install the tuning capacitor, coils and LED as shown in this wiring diagram. The LED is mounted on the underside of the board so that it protrudes through a matching hole in the front panel. Similarly, all the wiring to switch S1 and to the battery should be run directly to the copper side of the PCB. - 1 : ,MICROPHONE GNO 2 : MICROPHONE 1 + 3 : MICROPHONE 2 + 4,5 : LOUDSPEAKERS ~ ANTENNA 750mm LONG trol pot, slide switch, LED and cord grip grommet. This can be done by using the front panel artwork as a drilling template. Check that all items fit correctly by installing them in position. Figs.3 & 4 show the assembly details for the PCB. Begin by installing PC stakes at the 1-5 wiring points and for the antenna lead, plus two more to support the metal shield (see Fig.4). Once this has been done, the 5mm formers for L1 , LZ and L3 should be glued to the board using an epoxy adhesive. The remaining parts can now be installed on the PCB as shown in Fig.3. Note that most of the resistors and all of the diodes are mounted end on. Take care with the orientation of polarised components. These include the ICs, transistors, diodes and electrolytic capacitors. The 0. lJ.LF capacitors are all monolithic types. Note that the O,lJ.LF capacitor adjacent to IC2 must be laid flat against the PCB, as shown in Fig.3. This is important because otherwise the capacitor body will affect the tuning of LZ, particularly with changes in temperature. OCT0BER1989 27 ~4 I 5mm 1.. L2 L3 fillID a A I! I I L4 L1 Fig.5: coils L1-L3 are close wound on 5mm coil formers using 100mm lengths of 0.8mm enamelled copper wire (ECW). L4 is made by winding 6 turns of 0.8mm ECW onto a 13/64-inch drill bit. c£=b ~ L5 i ~ Fig.6: the balun transformer is bifilar wound using two 100mm lengths of 0.8mm ECW. The finish of one winding connects to the start of the other to form the centre tap. The .0lµF decoupling capacitor for IC3 is mounted on the copper side of the PCB. This was done so that the capacitor can be connected as close as possible to the IC supply pins. Coil winding Above: full size artwork for the PC board (code SC 06111891). The inside sections of the clip pillars on the case bottom must be filed down as shown here. This is to allow the PCB to sit directly on the mounting pillars. 28 SILICON CHIP Work can now begin on the coils. Fig.5 shows the winding details for Ll-14 while Fig.6 shows the winding details for the balun (L5). 11 , 12 and L3 are all wound on the 5mm coil formers using 100mm lengths of 0.8mm enamelled copper wire (ECW). To begin each winding, strip 3-4mm of enamel from one end The two catches on the case lid (one on either side) are filed away so that the clip pillars can slide past the PCB when the lid is attrached. ( ROUND Off CORNERS J gJ TINPLATE SHIELD Fig.7: here are the dimensions for the tinplate shield. It is supported by two PC stakes between L1 & L4. of the wire and solder this end to the start pad on the PCB (see Figs.4 & 5). This done, wind on the correct number of turns for the particular coil as shown in Fig.5, starting at the bottom and moving up the former . Finally, insert the free end of the coil into the finish pad, strip back the enamel and solder. You can easily identify the start and finish of each coil by comparing Figs.4 & 5. 14 is made by winding six turns of 0.8mm ECW onto a 5mm former (eg, a 13/64-inch drill bit). It should be pushed all the way down onto the PCB and soldered in position as shown in Fig.4. 15 is wound on a Neosid balun transformer core using two 100mm lengths of 0.8mm ECW. Wind the balun exactly as shown in Fig.6 (one wire is shown black, the other in colour), then connect two of the leads together to form the centre tap. Strip back the enamel from the All the wiring to switch S1 and to the battery is run directly to the copper side of the PCB. Note that many of the tracks are close together so be careful to avoid solder bridges. The pen points to the .01uF capacitor beneath IC3. centre tap and the other two leads before soldering them to the PCB. The PCB assembly can now be completed by installing the small metal shield adjacent to 11. Fig.7 The leads from the coiled cord are terminated in a 6.5mm stereo jack plug for the microphones & a mono plug for the speakers. Use heatshrink tubing to sheath the leads to the plugs. shows the shield dimensions. It can be cut out from a piece of tinplate. Wiring Fig.4 shows the wiring details. The 4-way battery holder must be modified by soldering a wire link across one of the battery positions. Be careful - too much heat can melt the plastic around the terminals. OCT0BER1989 29 Begin by installing the LED on the copper side of the PCB. It should be positioned so that it protrudes through the hole in the front panel when the board is mounted in the case. The wiring to switch S1 and to the battery should also be run to the copper side of the PCB. The pot can be wired to the top of the PCB using short lengths of hookup wire. Note the link between one of the pot terminals and the pot case. The next step is to fit the Scotchcal labels to the front panel and to the thumbwheel. Fit the front panel label first, then temporarily fit the thumbwheel to the tuning capacitor and mount the PCB in the case. Now rotate the thumbwheel fully clockwise and use a pencil to mark the rim where it aligns with the line on the front panel. This done, remove the thumbwheel and fit the dial label so that the 88MHz marking aligns with the : pencil mark. Note that the dial faces toward the PCB when the thumbwheel is fitted to the tuning capacitor. Be careful here - it's all too easy to affix the dial to the wrong side of the thumbwheel. The coiled cord and antenna lead can now be installed. These both pass through a hole in the front panel and are clamped by a cord grip grommet. Fig.4 shows the wiring details. Note that the wire colours shown on Fig.4 are for the specified Tandy cord. This cord has four colour coded wires (white, red, blue & black) and the white lead is shielded (ie, there are five conductors in all). We've wired the cable in an unconventional way which gives the best overall performance from the unit. Note in particular that the white wire is used for the microphone ground connection and its shield is used for one of the speaker connections. The leads at the other end of the coiled cord are connected to a 6.5mm stereo jack plug for the microphones and to a 6.5mm mono jack plug for the loudspeakers (see Fig.8). Connect the white lead to the common earth on the microphone jack and the red and blue wires to the left and right jack terminals. 30 SILICON CHIP 6.5mm STEREO LINE SOCKET □- LOUDSPEAKERS - □ MOTORCYCLE INTERCOM - - HELMET Fig.8: here's how to mount the microphones and loudspeakers inside the helmet. Note that only one of the microphones is positioned directly in front of the user's mouth. The loudspeakers are fixed in position behind the helmet lining. RADIO INTERCOM • • • • • • • • ·- VOLUME TUNING 8 TRANSMIT • ' OFF FM INTERCOM Here is an actual size artwork for the front panel. The black lead and the shield go to the terminals of the mono jack plug (the polarity is unimportant). To make the wiring neat, use heatshrink tubing to sheath the leads to the plugs at the end of the cord and to sheath the "Y" intersection. Finally, the 4-way battery holder must be modified so that it will take only three cells. The fourth cell position should have a wire strap soldered between its positive and negative terminals. Be quick about it when soldering in this wire strap as too much heat will melt the plastic around the terminals. That's all we have space for this month. Next month we'll continue with testing and alignment. 1§:;i MOTHERB OARDS IBM PC[1J COMPATIBLE TURBO 10MHZ MOTHERBOARD CONTROLLER CARDS 360KBll20KB/1.2MB/1.44MB FLOPPY DISK DRIVE CONTROLLER CARD FOR IBM PCf1J/AT AND COMPATIBLE COMPUTERS -Allows connection of one or two 360KB, 720KB, 1.2MB or 1.33MB floppy disk drives. 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It will allow connection of up to two hard disks and two flOP.PY 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 XT -Norton SI rating of 2.0 -Size (12" x 8.5") -Weight (1.75lbs) 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 connect a second hard disk drive an additional cable will be requ ired. $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 IBM PC/XT/AT COMPATIBLE KEYBOARD -101 Key -Enhanced keyboard layout -Tactile touch keyswitches -12 Function keys -lluminated LED indicators for Num Lock, Caps Lock and Scroll Lock -Seperate 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'h) -Weight (4.6Ibs) $109 84 KEY $99 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 and extended memory capabilities -Features auto-parity check -EMS compatible driver -RAM disk and print spooler software included -Manual included ND RAM MEMORY CARD PCf1J for 640K $245 $99 ALL PCM CARDS COME WITH A 12 MONTH WARRANTY All other prducts with manufacturers warranty DON'T BUY ELSEWHERE CHECK WITH US FIRST CASES 8088 BABY 8088 BABY 80286 $99 $129 $129 S299 MINI TOWER MAXI TOWER S699 bothwith power supply DISK DRIVES 720k 3.5" 1.44Mb 3.5" BOTH INCLUDE 5.25" mounting 360k 5.25" 1.2Mb 5.25" $199 $225 $179 $225 PROTOTYPE DEVELOPMENT CARD - NEW Basic circuit already built-in. Has 3290 holes - this will save prototypers lots of time and energy. $199 SLOT EXTENSION KIT - NEW FOR DETAILS ON OTHER PRODUCTS PLEASE RING. 1/0 CARDS RS232 HALF CARD FOR IBM PC[1J AND COMPATIBLE COMPUTER -Fits the difficult to use half card slot or any long slot -RS232 card comes with one ready to go serial port -Expandable to 2 ports by user (parts for expansion not included) -Selectable for COM1 thru COM4 -The user is able to select addresses for ports A and B as well as interrupt requests -Manual included 1/0 CARD FOR PC[1J W/GMS CLCK 1/0 CARD 2 PO RT FOR AT 1/0 CARD FOR AT WITH GAMES MULTI 1/0 CARD WITH MONO GA MULTI 1/0 CARD $125 $65 $125 $229 $149 -Expandable to 1MB RAM using 256K DRAM chips -Expandable to 4MB RAM using 1MB DRAM chips -Expandable 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 BIDS ROMs included -Zero wait state -Selectable RAM chips speed (80 or 100 nanosecond) -80287-8 Math co-processor capability -Norton SI rating of 13.7 -Size (13" c 8.75") -Weight (2.25lbs) $499 IBM AT COMPATIBLE 200W POWER SUPPLY -Input <at>47 -400Hz (110/240V switchable) -Output +5v <at> 20A, -5V<at> 0.5A,+12v<at> 8A,-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 Compatible with AT and XT. Excellent for test and repair of PC add-on cards $199 NOTE: No RAM on any board unless specified. All prices include tax and are subject to change without notice. SPECIALS FOR THIS MONTH OR WHILE STOCKS LAST 1. NEAT MOTHERBOARD 16MHz - AT compatible and expandable to 8Mb RAM $649 2. 42Mb HARD DISK DRIVE - American manufacture $499 3. VGA MONITOR including VGA card $999 ring for details PERSONAL COMPUTER MARKETPLACE Pty Ltd PHONE (02) 418 6711 FAX (02) 418 6713 Mail Order Address: P.O. Box 1100 Lane Cove NSW 2066 $149 IBM AT COMPATIBLE 12MHZ 80286 MOTHERBOARD FREIGHT CHARGES Include $10 with order for all nonnal items • heavy items, e.g. monitors add $15. 14 day money back guarantee Order by phone (use credit card), by fax or by mail. VISA --...... -- $125 $145 Improve your amateur TV reception The Gladesville GaAsFet alllplifier This simple masthead amplifier can greatly improve reception on the 50cm and 70cm amateur TV bands. It's a low-noise design that's easy to build and get going. By 'BIG JULIE' KENTWELL, VKZXBR effect transistor. This project was originally designed by "Big Julie" VK2XBR, of the Sydney Amateur Television Group, to assist viewers of the Gladesville Amateur Radio Club's TV Group. The original version was a high-performance unit which was, however, rather difficult to build. This printed board version offers less gain but is vastly easier to knock up and get going; in fact it's Interested in watching your local amateur TV station to see what they're up to? If so, you'll need a UHF band 4 antenna (such as the bowtie design featured in the January 1988 issue of SILICON CHIP). And since amateur TV stations operate at low power, you will also need a masthead amplifier with decent gain and, more importantly, low noise. To fill those two requirements, this amplifier uses a GaAsFet, a gallium arsenide field 01 MIIF9S6 751) OUTPUT L2 + 2v._..,.c2,,c;.,~o. .:.+.::a&.sa.av_ _ _--41 751l INPUT FROM ANTENNA DV 61 R1 4.7k C3 .001 S L1 C2 .001 C4 0.5-7pF G1Jll=O u=ROM S TYPE NO. SIDE THE GLADESVILLE GaAsFET PREAMPLIFIER Fig.I: the circuit is based on Ql which is an MRF966 dual gate GaAsFet (Ql). Cl and 11 form the input tuned circuit while C4 and L2 form the output tuned circuit. Power is fed to the amplifier via the coaxial downlead. 32 SILICON CHIP just about foolproof. It is described here for use with 50cm (580MHz) amateur TV but covers 70cm (426MHz or 444MHz) just as well. The unit is not a substitute for a good antenna; if you want more signal, stick up more metal! Nothing replaces an appropriate antenna. Where this amplifier shines is in achieving a low RF noise figure (which equates to less "snow" and more picture) and in offsetting some or all of your antenna cable loss. Here too, nothing substitutes for quality. Choose a good, coppersheathed, semi-airspaced cable such as Hills DSC21. Also, amateur television transmitters are low power, so fringe antennas such as the Hills XG21 (channel 35 version) or the Fuba equivalent cost plenty but work the best. This amplifier was tested on a typical suburban UHF TV system about 60km away from the 40 watt (peak sync power) Gladesville amateur TV station. The antenna was a Matchmaster D18 channel 28 version at "average TV antenna height", connected through 10 metres of Hills DSC21 cable to a Sanyo CTP 3620 television set. This TV uses a rotary UHF tuner with a rather mediocre RF noise figure. The Gladesville picture on this system was Pl.5; ie, only the large print was readable with over 50% audio noise. With the amplifier added at the TV set end (where it would have the least effect), the picture was P3.5; ie, a moderate amount of snow but fine print and detail all clear and no noise on sound. The consensus in the Sydney ATV group is that P2.5 is the minimum acceptable for serious viewing. 7511 OUTPUT 7511 INPUT FROM ANTE NA Fig.2: the parts for the amplifier are all mounted on the copper side of the PC board. Keep all lead lengths as short as possible and note that the .001µF capacitors are leadless chip ceramic types. Right: the Gladesville GaAsFet is hardly a thing of ► beauty but it works! The metal shield across the middle of the board separates the input and output tuned circuits to ensure stability . .\:Os'T I. I 19mm Fig.3: the input inductor (11) consists of a single turn of 1mm tinned copper wire wound on a 7mm former. 7511 COAX 'TO TV TUNER CERAMIC CAPACITOR . - - 47-47OpF VERY SHORT LEADS TV ANTENNA SOCKET .TO+ V+ SUPPLY RESISTOR Fig.4: here's how to modify your TV set to provide power for the amplifier. Note that the DC supply must come from a low impedance source (see text). All in all, this amplifier is a cheap and easy way to improve your amateur TV viewing enjoyment. Note: Matchmaster now have a UHF antenna with somewhat ·higher gain, the MX21. This retails for $130 plus 30% sales tax and is available from Matchmaster TV Sales Pty Ltd, 2 Mimosa Street, Bexley, NSW 2207. Phone (02) 587 4499. Circuit details Fig.1 shows the circuit details of the preamplifier. It's based on Ql which is a Motorola MRF966 dualgate GaAsFet (gallium arsenide field effect transistor). This pro- vides about 20dB of gain with a noise figure of less than ldB. Ql is operated in common source mode with DC bias for gate 2 provided via R2 (10k0) and Rl (4.7k0). Trimmer capacitor Cl and inductor L1 tune the input to gate 1 and the amplified output appears at the drain. The signal is then coupled to the output via a second tuned circuit consisting of C4 and L2. To ensure stability, it is important to use good quality capacitors for the gate 2 and source bypasses (.OOlµF). For this reason, leadless chip ceramic types have been specified in the parts list. The preamp circuit requires a + 6.5V DC supply and this can either be derived from the TV set itself or from an external power supply such as a 12V DC plugpack via an adaptor board. This DC voltage is fed to the preamp via the coaxial downlead. Construction A shortform kit for this project is available from the Gladesville Amateur Radio Club and contains 2 circuit boards, 3 chip capacitors, an MRF966 GaAsFet, 2 trimmer capacitors and a ferrite cylinder. You will then need to obtain separately four (or three) resistors, the input coil and three (or two) capacitors, depending on whether you use the power adaptor board or not. Construction is simple and follows the layout diagram (Fig.2). The three .OOlµF chip capacitors are mounted first; these are tricky little devils to install. They will cling lovingly to your soldering iron tip if you don't hold them exactly in place. Don't squash them; they are easily broken. Don't use excess solder; remove same if you use too much. The input trimmer capacitor (Cl) is fitted next, followed by inductor 11. The input inductor is noncritical and can be made from any short piece of bare or tinned copper PARTS LIST 1 PC board for preamplifier, 65 x 43mm 1 PC board for power adaptor, 60 x 42mm 1 MRF966 dual gate GaAsFet (01) 1 F29 ferrite cylinder Capacitors C1 ,C4 0 .5-7pF trimmers C2,C3 ,C7 .001 µF leadless chip ceramic C5 4 .7µF 25VW tantalum C6 .0 1 µF miniature ceramic Resistors (0.25W, 5%) R1 R2 R3 R4 4 . 7k0 10k0 1000 see text, 1 W Note: a shortform kit for this project· (see text) is available from the Gladesville Amateur Radio Club, PO Box 48 , Gladesville NSW 21 1 1. The cost is $25 plus postage and packing . Phone enquiries to the club may be made on Monday, Thursday and Friday evenings after 6 .30pm by dialling (02) 427 0530 . OCT0BER1989 33 R4 1W TO SUIT SUPPLY r---W'lf---+--0+11-19V FERRITE BEAD ea 2.7-47pF C9 1-.041 DUTPUT TD TV Fig.5: this is the circuit for the external power adaptor board, which is used if you don't wish to derive power from your TV set. The text shows you how to calculate the value of R4. INPUT -JAR (TAPED OR HOSE CLAMPED TO MAST) +11-19V TAPE HERE INPUT FROM AMPLIFIER DUTPUT TO TV ~GROMMETS_/ DSC21 TO TV Fig.6: here's how to install the parts on the power adaptor board. Power can be derived from a 12V DC plugpack supply. wire around 1mm in diameter. Fig.3 shows the details. Wind it once around a drill shank or other suitable former and shape it according to the diagram. This done, fit the resistors, bypass capacitors and output trimmer capacitor (C4). You don't have to worry about making up inductor L2. It's already there as part of the PC board pattern. The MRF966 GaAsFet is mounted right in the middle of the board. First, drill a small pilot hole, then enlarge it so that the body of the MRF966 is a snug fit (3/16-inch is exact although 5mm will do). Note that this will remove some gate 2 circuit board track, which is of no concern. If you like, you can simply sit the device on top of the boq.rd but we recommend the clearance hole, as it makes it easier to locate and solder. The MRF966 can now be fitted. Take care! - this device is a dualgate Mosfet which doesn't take kindly to static discharges. The drain (longest) lead should be cut off to leave just the small square section next to the case. Solder this lead to the PC board first, then the source, then gate 2. Gate 1 requires comment there is no copper track for it because this would have introduced unwanted stray inductance and capacitance effects. Instead, the gate 1 lead is "kinked up" slightly 34 SILICON CHIP Fig.7: the circuit can be weatherproofed by installing it inside a glass jar which is then clamped to the mast. The lid must be sealed to prevent water entry using either silicone sealant or Teflon tape. and soldered directly to the terminal of trimmer capacitor Cl, along with inductor Ll. DC supply Now let's look at the DC supply. This should be 6.5 volts and is fed to the amplifier via the coaxial downlead. The required voltage is derived by applying 11-19V DC to a series resistor which can be located in the TV set or on the separate power adaptor board. Deriving power directly from the TV set is the best solution. Forget about modifying your VCR if, as do many people, you use it to receive ATV. VCR RF boosters can be modified but it's such a hideously difficult task that the result would probably be a defunct VCR. Use the adaptor board instead. TV sets are easy to modify if they are not "live chassis" . There is no easy way to pick a hot-chassis TV set because: (1). Not all sets with a live chassis warning on the back are in fact livechassis; (2). Not all sets with mainsisolation safety capacitors in the antenna socket are live-chassis. Be absolutely certain that your TV chassis is not connected to 240V AC power (usually through a 4-diode bridge rectifier) before modifying it. Failure to do so could either destroy your set or kill you. An almost certain clue is that if the set has a 2-core power flex , it will have a live chassis. But there is only one way to be certain: check the AC voltage between mains earth and chassis. It's safe only if you get a reading of OV. If your TV is safe, disconnect the TABLE 1 • Sydney Amateur TV Group, PO Box 142, Winmalee, NSW 2777 . • Wagga Amateur Radio Club , PO Box 294, Wagga Wagga. Contact: Peter O'Leary, VK2 DOL. Phone (069) 22 5738 AH . • Melbourne: contact Doug White, VK3BOW. Phone (03) 8 70 9151 . • Adelaide: contact Rod Rees, VK5AWA , 5 Wynette St, Penn- ington , SA 5013 . Phone (08) 47 2 161 . • South East Queensland ATV Group , PO Box 3, Chermside , Old 4032 . Footnote : the above list is by no means comprehensive . Other amateur TV groups are invited to submit details of their activities for publication in a future issue of SILICON CHIP. centre wire to its coaxial antenna socket and reconnect it through a l00pF disc capacitor as shown in Fig.4 (47pF to 470pF will do). From the set's circuit diagram, find the low-voltage (11-19V) power supply which usually comes from a diode and low-voltage winding on the horizontal output transformer. Don't waste time picking up 12V from the tuner or elsewhere unless it is a direct line with little or no series resistance to the point of origin. When you have found your nice low-impedance line you may connect a length of insulated wire to this line and route it to the antenna socket. Solder the dropping resistor to the end of this lead, slip the ferrite cylinder into position, and solder the resistor to the centre pin of the antenna socket (see Fig.5). The value of the dropping resistor will depend on the supply voltage. Quite a few of these preamplifiers have now been built and they all draw around 20 milliamps. Once the current is known, you can use Ohm's Law to calculate the value of the dropping resistor. For example, if your preamplifier draws 23mA from a 6.5V supply, then for a 12V rail you will require R = V/1 or 5.5/0.023 = 2390. Such resistors don't grow on trees but two 1200 ½ W resistors in series will be close enough. Power adaptor The power adaptor board is used only if ybu are unable or don't wish to derive power from your TV set (eg, if it has a live chassis). This board carries the dropping resistor( s) plus the ferrite cylinder and a small signal coupling capacitor. The capacitor can be any good ceramic type (eg, chip or disc ceramic) ranging in value from 2.7pF to 47pF (lower values preferred). Be sure to keep its leads as short as possible. All you have to do is follow the wiring diagram (Fig.6); we won't say "you can't go wrong" but it's very difficult to foul up on this one! Alignment Alignment is simple if you have the correct tool. Metal screw- The jar can then be taped, hosec~amped or otherwise attached upside down to a convenient point on the mast near your antenna. Don't put it lid-up or you will drown your amplifier. The 70cm band This is the completed power adaptor board. Use good quality coaxial cable for the input & output leads (eg, Hills DSC21). This view of the amplifier board clearly shows the metal shield and the mounting details for inductor Ll. drivers are useless on the input trimmer; instead, use a plastic tool with the smallest possible metal tip. Simply align both trimmers for best picture on your local 50cm ATV station. This operation can be done in your shack with the amplifier mounted close to your TV set. The amplifier can now be mastmounted. The cheapest, easiest way is to get a large screw-top glass or plastic jar. Drill two holes in its lid to take rubber grommets through which the input and output cables will pass. Assemble the unit by passing both feedlines through the grommets and connecting them as shown in Fig.7. Screw the jar onto the lid and seal it to prevent water entry. This can be done by coating the jar thread with sealant but pity help you if you ever need to service the unit. A better method is to firmly tape around the seal with plumbers' Teflon tape, then tape over this equally firmly with black PVC electricians' tape. If you wish to try this unit on 70cm amateur TV (where XG21 's, D18's etc will not work), you will need two turns on the input inductor. As an extra, you may add another 7pF trimmer capacitor from gate 1 to ground. This makes alignment more difficult and you may not need the extra capacitor but it's worth a try. Incidentally, if you modify your TV set to drive this unit through the TV antenna socket as described earlier, the normal TV performance on VHF/UHF is unaffected. This is because the coupling capacitor specified (47pF to 470pF disc ceramic, short leads) passes all TV frequencies. The use of a resistor with a 1W rating inside the TV set, and the insistence on its connection to a lowimpedance voltage source, is to ensure that normal use of the TV set is unaffected. Most driven elements in an ordinary VHF/UHF TV antenna are a DC short circuit. Connection of such an antenna to a modified TV set merely grounds the series resistor which then dissipates around half a watt. If your finished amplifier oscillates or otherwise takes off when aligned (unlikely!) you may: (1) reduce the supply voltage slightly; (2) detune the circuit, remembering that best picture alignment as seen on the TV does not correspond ~ith maximum-gain alignment; (3) fit a small metal shield across the MRF966 as shown in the photos; or (4) employ a combination of some or all of the above. Instability has not been a problem with these units, although it can occur when no antenna is connected at the input but this hardly matters, does it? One does not normally watch distant TV stations without an antenna. Finally, Table 1 lists a number of amateur TV operators and these can be contacted for further information. lt:i OCT0BER1989 35 ltSHNING POST • Dual Tracking Power Supply Kit This power supply can provide voltages from Oto ±21.SV at currents up to 2 amps. It also features overload protection. a fused +5V 1 amp output, and output voltage metering. Cat. KA-1682 $12 9.95 buffer for your printer A 1 This easily built unit installs between your computer's Centronics printer port and your printer. By feeding your printout files to a buffer, you and your computer can proceed with other tasks while the printer operates in the background. Design by DON McKENZIE Waiting for your printer to do a printout can be a real pain, particularly if the file concerned occupies several hundred kilobytes of memory. With an average printer, printing out a file of this size could take several hours. That's a long time to have your computer tied up , if you are anxious to get on with other computing tasks. If you use your computer for CAD work, the files can be very large when fed to a plotter. Here's where this buffer really finds its niche. By having a printer buffer with a large memory, you can dump your files to it and it can then feed the printer at the pace it requires, leav- ing the computer free for other things. Printer buffers are not cheap though and those with large memory can set you back quite a bit. For example, a buffer with 256Kb of memory is likely to cost around $339 [eg, the BIT PEPbuffer) while a unit with one megabyte (1Mb) will set you back a lot more. Some printers can also be fitted with fair-sized buffers which achieves the same result but they're often even dearer for a given amount of memory. RAM chips have come down drastically in price in the last year or so, so you really can save quite a The printer buffer is built into a standard plastic instrument case. The two pushbutton switches are for Reset and Test, while the two toggle switches are for printer Pause and Copy control. 40 SILICON CHIP lot of money by building your own printer buffer to this design. You can also tailor it to suit your needs, building in as much or as little memory as you need. We expect that you could build the 1MB printer buffer described here for $300 or less. To build the printer buffer you will need a reasonably well equipped tool kit which will include a multimeter. A logic probe could also be a help with any hardware problems that you could run into. The logic probe suggested by the designer is a 3800A which is available at most electronic outlets for around $30.00. Don't buy a logic probe right now but if you do run into strife then it may be needed. While you can build the buffer into virtually any box, the prototype was housed in standard plastic instrument case available from most kitset suppliers. It is powered by a 12V DC plugpack which means there is no 240V AC mains wiring to mess about with. Main features On the front panel of the buffer there are two LED indicators, one of which flashes when the unit is handling data. There are two toggle switches: one to pause the printer and one as the copy control. There are also two pushbuttons: one to reset the unit and one for the test routine. As the name suggests, the Copy control lets you print out the contents of the buffer. Thus, you can print out more than once without having to go back to your computer. On the rear panel of the buffer, there is a standard female Centronics printer port and a DB25 female socket. We'll talk more about these later. Inside, there are two printed cir- ~ ,-,. CD CXl CD .... ~ t'I:I 6ttl 0 (") .0 C R 10 3.58M X1 R1 100 12 B +5V CB .01 I _ INPUT _ - IV AC lR DC J4 I 2 ~ C4 ,: : W! - 1 4 IN GND --"'i 7805 ,-0+12V .,c....._.... 01 ~13\ _ lc9• 74SLOO 1 2 IC9b 9 10 D7 r 4 GND OUT \w ==- sc1-01-11:: 16 TANT c~ OUT ; IN 3 D7 DO 01 02 03 04 05 06 8255/CS fW !- PORT D J1 PIN 18 sr 2 20 19 11 12 13 15 16 17 1f 10 9 8 7 6 5 4 3 2s 24 21 23 22 " CS K ->- 1M PRINTER BUFFER 2!090 - P~Si°E~ le~ A K ~ A +5V IC 13 j1° c"'?a 11 26 11 IC11 BK EPROM 2764 OR 27128 120 121 I T j,!!..., I 1~ 4 RAS 15 14 13 9 18 19 11 12 13 15 16 17 IC1 I 22 OE 1 27 WE IC14 6364 28 14 ' ~ S3 DO 01 02 03 D4 05 06 07 02 IC2 IC3 10 04 tl1e 06 IC12 8255 26 ::i 4 PC4 13 A14 IC5 l10 IC6 IC7 1k IC13 e 6 1-s· 3_ D. 2 D - D OUTPU 130+ 5V PAUSE 120GI _ ~B: 10-Al 9;; s-D Dt 7 O 6- 0 5 . 4 - D: ~i . ,. R5 = 16- D 15-~ 14 - S 17 = 24_ 8 22;; 0 21;; D 20 D 19;; 0 10;;0 25o 6 ND 23-A J2 INPUl 260 ➔ 5V r---------- A13 J ·RN2 4.7k 5 ICB 5 16 17 8 = +n - 1M: o----:f. CAS AO A3 AB o----~- CAS =- ~ 1M 256- 256 1M- 2:~- - AS M2 TO M5 A D D I T I O N A L ~ GND BUS FOR 1 MEG ,. M2 M3 M4 M5 l 1 l l 256 __ 1M- ......25__s,.,_._M.1,_....., u MS AND M7 ADDITIONAL +5V FOR S4 Kl~:K M 7 12"'+7 'i;718 07 ~ l RN4 4n RN 3 47 - k + I 13~-" - , ~ ) 6 I IC9c ~ D ' ' - - - - - + - ~ . +5V RN5 4.7k + 5V 5 6~ LED1 DATA'i; K R4 IC13d 3300 2 r> PC 12 5 PA 7 37 PAS 38 PA 39 5 PA 40 4 PA3 1 2 PA 2 1s PCS 11 PC 2 16 25 PB7 24 P86 PB 5 23 P84 22 21 PB3 20 2 PB 19 CS PB1 18 PBD RESET RD WR 35 5 36 PC7 - n ◄;i18 L L L - 05 '\ BxDYNAMIC RAMS 4164 ,41256,4&1024 IC4 ◄;718 03 'I 7 15DpFI C5 •~ ...Ji ~ 9 ~ AO __] --F°" 34 33 32 31 30 29 28 27 ,----1J! COPY\( RN6 4.7k L...1...._.,_,..__1..._..,_,,,__1..._..,_,,,__.__.,._,,,_,--.__.,._,,,__.L-_...,,, __,-..__...,,,,__,--'--..,,,_.,,.....,19 A2 A3 A4 A5 A7 A11 _ ~ 7 l2 •-=---',i 1 D1 'I 06 01 DO 01 02 03 04 05 9 8 7 6 5 4 3 25 24 21 2 2 20 CS1 26 CS 2 10 - '-------~--➔------< . ➔_,, A1 A2 A3 A4 A5 A6 A7 AB A9 A10 A11 A12 A14 A1 5 AO 4 iz71s 10 ';718 10 tl1e 10 3 WR DC ADDRESS BUS --.....,-::::::::~::: 'DATA BUS _ _ I AO A1 A2 A3 A4 A5 A6 A7 AB A9 A10 A11 A15 N?-,.L i ___J S ~ bH n _ , o lI 22 WR 21 Ml lORO 20 27 19 13 9 10 00 01 02 03 04 05 06 A2 A3 A4 A5 ., A6 A7 AB A9 A10 A11 A12 A13 A14 A15 AO A1 ------- '-----.l!.j-~)2..----___. 9 14 15 12 8 ~ I MREQ ' - -- ~.J;2!9_ _ - :1i1i 32 33 34 j 35 36 '7 38 39 1 40 1 2 3 4 5 i I 31 1 30 L-------~---•.---~--~ ~ - .,. ,------:'.:J AC TANT 1lv2wI 16 INT 17 NMI 6 CLOCK 111 25 lz4 VCC BSRQ WT 26 , _ RESET 4 ~ I l + 5V -. 7 _J; :I 5 I3 R6 4 .7k _j_ • 11e 14 • .,. -:- 555 IC1 5 4 +5V 4 m~ 1 7 14 7 ~.,. .,. 3"" RN 7 4.7k T~JT l R2 2700 E 1~~ RltETI . .- - - ~ ,____. 6 ....__] I , I 1 8 0 E C VIEWED FROM BELOW ~ •= C1 220pF' I c:, CS ,:= 680pF -------"+~-I 8~48 .,-.,,,.C 8£ r"'< The circuitry for the printer buffer is built onto two PC boards, one carrying the microprocessor and memory chips, and the other the two parallel interface sockets. Note the heatsink on the 3-terminal regulator. cuit boards, one to carry the microprocessor and memory chips while the other is for the two parallel interface sockets. Z80A microprocessor The printer buffer is designed around the good old Z80A which can be had for peanuts. The operating system and instructions for the Z80A are stored in a 2764 EPROM (Electrically Programmable Read Only Memory) while a 6264 static RAM (Random Access Memory)serves as a stack for the microprocessor's instructions. Input and output interfacing to the outside world is provided by the 8255 PPI (Programmable Peripheral Interface). The main concept of the design is to cut down the hardware required to produce a microprocessor controlled printer buffer with a large capacity and perform all the bells and whistles in the software. No address or data buffers are used or required. As already noted, the only port addressed device is the 8255 PPL This is the interface to the computer input and printer output bus. 42 SILICON CHIP The Z80A's IORQ line is connected to the chip select of the 8255. Any time an 1/0 instruction is executed the 8255 responds. Any port from zero to 255 is the 8255's port decode. The power up routines program the 8255's three ports to mode 1: Port A input, Port B output, and Port C handshaking for A and B. Capacitor C5 hanging on the chip select line to ground produces enough of a delay to satisfy the timing restrictions of Z80A to 8255 interfacing. The printer output strobe is produced by one inverter of the 74LS04 which inverts CPU signal A13. Any time the program sets A13 high, a printer strobe pulse is produced. The setting of A13 is actually done with a BC register pair port instruction, not a memory address. During a power up or reset of the CPU all address and data bus signals go to a high impedance state. The high to A13 appears as a printer output strobe every time the buffer is reset. This is where resistor R5 is useful. Without R5 installed some printers will hang up. They detect the output pr-inter strobe during reset, read the data and issue an acknowledge (ACK) to the buffer. The buffer doesn't pay much attention to this ACK because it has just had a reset and now wants to do initialisation. With R5 installed, instead of A13 tri-stating during a reset, it is held low by R5 to ground and this spurious strobe isn't produced. Pin 12 of the 8255 is the input BUSY to the computer. This signal is inverted by the 74LS04 to produce the ACK signal. This means that while the 8255 is holding the ACK active (low) it sends the BUSY signal to the computer. The ACK is also connected to R4 and the Data LED. The Data LED lights up when the BUSY is high and ACK is low, and switches off when BUSY is low and ACK is high. This LED is used for the ROM diagnostic routines to aid kit builders, and also indicates data entry into the buffer. When the buffer is full, the LED lights up brightly to indicate a full BUSY condition. The value of R4 is a compromise between lighting the LED up brightly enough to see data activity, and not loading the ACK line to the computer excessively. The Reset signal to the 8255 is a positive going pulse, which is the inverse of that for the CPU. One gate of the 74LS04 is used to generate this pulse from the CPU reset. The dynamic RAMs are enabled when address lines A14 and A15 are high. This gives a starting address of C000H. A15 high disables the EPROM. The Z80A takes care of refreshing the DRAMs (D for dynamic) in the normal refresh register mode. The data in the refresh counter is sent on the lower portion of the address bus (A0-A6) along with a refresh control signal while the CPU is decoding and executing the fetched instruction. This mode is totally transparent to the programmer and does not slow down the CPU operation. The program must constantly service this refresh requirement. This involves calling a refresh routine approximately every 256 instructions. So the DRAMs aren't really part of a typical memory map; it's soft- ware deception. The true map of the DRAMs as far as the CPU addressing is concerned is C000H to C0FFH (only 256 addresses). H register set to C0H and L register set to LSB select each byte. The MSB (most significant bit) of the DRAMs is dependent on the contents of the R register during a read or write procedure. What we are left with is a lump of DRAM that is not much good for anything except storing great chunks of data. You can't run a machine language program in it. It's a complete wraparound buffer. When the storage pointer gets to FFFFH, its next location is zero, and round and round it goes. So what is the 6264 static RAM used for? It actually functions as an external stack for the microprocessor since the Z80's internal stack is not big enough for the program. Short form kit If you want to build this printer buffer, there's only one way to do it. The designer, Don McKenzie, owns the copyright on the printed circuit board patterns and the software in the EPROM. He sells a short form kit which comprises the double sided buffer printed board, an EPROM containing the software and the assembly instructions for $39 plus $3 for packing and postage. If you want the small DB25 to Centronics socket adaptor board, that will be an extra $9.00. All the rest of the components have to be obtained separately by you, the builder. If you are looking for a one stop shop, one good possibility is Rod Irving Electronics who have stores in Sydney and Melbourne (see their adverts elsewhere in this magazine). You can build the buffer in three memory sizes: 64Kb, 256Kb or 1Mb. The software in the EPROM will sense how much memory is installed and operate accordingly. No fuss, no bother. Assembly The first step in assembly is to check the double sided printed board for manufacturing faults . These are rare but it is highly desirable that you find any problems before components are in- PARTS LIST 1 plastic instrument case, 200 x 160 x 65mm, DSE Cat. H-2505 or equivalent (see t~xt) 1 9V 500-600mA DC plugpack, DSE Cat. M-9560 or equivalent 1 double sided plated through printed board, code PBUFF (available from Don McKenzie) 1 single sided printed board, code BPIO (available from Don McKenzie) 1 3 .58MHz crystal 1 DB25F socket 1 Centronics female socket 1 IBM printer cable 2 SPST toggle switches 2 momentary contact pushbutton switches 1 LED bezel 1 T0-220 clip heatsink (for 7805 regulator) 2 40-pin IC sockets 2 28-pin IC sockets 8 20-pin IC sockets 2 1 4-pin IC sockets 1 8-pin IC socket 1 26-way dual row male header socket (J2) 1 1 6-way dual row male header socket (J3) Semiconductors 1 Z80A microprocessor (IC10) 1 2764 EPROM (IC11), available from Don McKenzie 1 6264 8K static RAM (IC14) 1 8255 programmable peripheral interface (IC12) stalled. If a track fault is under an installed IC it can be impossible to find. So check it thoroughly, now. IC sockets are recommended by the designer for all the large chips and the memory. The memory chips are very close together so you can't use bulky sockets. Use the good quality slimline types. Take note of the orientation of pin 1 of all ICs, as they do not all face the same way. This has been done to minimise the size of the board. Regardless of what size memory you intend using it is a good idea to install all the memory IC sockets and their accompanying .01µ,F ceramic bypass capacitors. Install the 8-pin resistor network 8 41256 256K bit dynamic RAMs (IC1 -IC8) for 256Kb version or 8 4C1024 1024K bit dynamic RAMs (IC1 -IC8) for 1 Mb version 1 555 timer (IC15) 1 7 4LSOO TTL hex buffer (IC13) 1 7 4LS04 TTL quad 2-input NANO gate (IC9) 1 BC548 NPN transistor (01) 1 7805 3-terminal +5V regulator 1 W02 or W04 bridge rectifier (DSE Cat. Z-3304) Capacitors 1 2200µ,F 16VW PC electrolytic (C4) 1 22µ,F 16VW tantalum electrolytic (C2) 1 1 Oµ,F 16VW tantalum electrolytic (C3) 11 0.1 µ,F ceramic (BC1-BC11) 2 .01 µ,F ceramics (C7 ,C8) 1 680pF ceramic (C6) 1 220pF ceramic (C1) 1 150pF ceramic (C5) Resistors (¼W, 5%) 2 100k0 (R1 ,R7) 1 10k0 (R3) 1 4.7k0 (R6) 2 1 kO (R5,R8) 1 3300 (R4) 1 2700 (R2) 1 2200 (R9) 1 SIP resistor network package with 7 x 4 .7 kO resistors with one common pin into the board as shown on the overlay; ie, with pin 1 towards the dynamic RAMs. This done, install all the resistors as shown on the overlay. They can now be soldered in and the legs cut off flush with the solder joint. Watch the polarity of the three electrolytic capacitors C2, C3 and C4. They must be soldered in the correct way around. The same goes for the diode bridge Dl. Take notice of the markings on the bridge and make sure that these line up with the overlay. Solder in the 7805 regulator. The words " 7805 " must be facing towards the diode bridge. Fit the heatsink to the 7805. OCT0BER1989 43 DB-25 connector tracks so that the DB-25 connector will push hard onto the board without damage. Looking at the overlay side of the board, the two female connectors should be soldered with the widest part facing down. A 1k0 and a 4.7k0 resistor can be soldered into position as shown on the overlay, followed by the 26-pin dual row male header. The BPIO board is now finished. 9V AC OR DC INPUT Mounting the hardware 2 COPY 3 TEST 4 LED15 PAUSE 6 LED2- 10 COPY 11 TEST 12 LE01+ 13 PAUSE 14 LE02+ r~~~~:?-c~· Fig.2: this wiring diagram is for the 1Mb version of the printer buffer. The PBUFF board is connected to the PBIO board via a 26-way cable fitted with IDC female headers at either end. Position transistor Q1 into the board. If you use a DS548, the CBE connections are marked on the case and line up with the overlay as far as the flat side is concerned. The BC548 and the others, although not marked, should mount into the board the same way. Now solder in the 3.58MHz crystal. Don't push it fully into the board but leave enough length on the legs so that the crystal body will not short out the tracks immediately underneath it. BPIO hoard This is an adapter board to allow you to use an IBM to Centronics printer which is the cheapest you can buy. The BPIO board makes use of the IBM cable and standard connectors to save cost and simplify cable interfacing. Flat ribbon cable with standard 26-pin crimp type connectors is used to connect this board to the PBUFF board. 44 SILICON CHIP The BPIO board overlay is drawn showing the component side of the board. A standard DB-25F (female) solder type connector is soldered onto the edge of the board in the position shown. The female Centronics solder tail connector (or chassis type mount) will not be hard to obtain, but there are several types around. Some have spring clips that lock onto the male connector. The clips are nice but the standard (non-clip) connectors do lock hard onto the male connector quite firmly. The point to watch out for with the Centronics female connector is the distance between the two rows of solder tails. Look for a connector that has the two rows close enough together to be able to solder to the edge of a printed circuit board. The pin numbers of the two connectors are marked on the BPIO board. You may need to use a file to bevel a slight 45° angle along the The BPIO adaptor board can be mounted using the two outer mounting holes of the DB25 and Centronics connectors only. Board inter-connections can be done with a 200mm-long 26-wire flat ribbon cable fitted with a 26-pin dual row IDC type female crimp header at each end. When drilling holes in the front of the case to mount the switches, make sure that they don't interfere with the components on your PBUFF board. All the connections to the front panel hardware are made via a cable from the 16-pin dual row header J3 on the PBUFF board. This provides wires to the Reset button, Copy switch, Test button, Data LED, Power LED and the optional Pause switch. Powering up When all your assembly work is complete, you are ready to install the chips. But before doing that, connect up the plugpack transformer. The power pack connection points are shown on the overlay. With your multimeter check that ground and + 5V are not shorted together. Power up the unit and check that the + 5V is there before proceeding. All OK? Power down and install chips IC12 (8255) and IC13 (74LS04). Power up again and check the + 5V. If the LED is not already on, press the Reset button. The LED should light up brightly. If the LED is not flashing, then you have one of the following faulty: IC12, IC13, the reset circuit or, more likely, you have the data LED wired in back to front. With that sorted out, you can install IC9 (74LSOO), IC10 (ZBOA) and The rear panel of the printer buffer carries a DB25 female socket (left) and a standard female Centronics printer port. This allows you to use a standard IBM printer cable which is cheaper than other types. Fig.3: here are the linking details for the 64Kb and 256Kb versions. Note particularly the different arrangement for Mt. ICl 1 (EPROM), and power up. The Data LED should now be flashing at about once per second. If the LED is flashing, it indicates that the Z80A is running and the software is doing its job but that a RAM fault exists. With no RAM installed this is to be expected. Now it's time to insert one RAM chip. Power down and insert a RAM chip into socket IC8 (Data bit 7). Watch out for pin 1 (look at the overlay). Switch to Copy ON, power up and check your + 5V again. At this stage, the LED should be flashing at 3 cycles per second, which indicates that RAM is present and can be written to and read from. Switch to Copy OFF. The LED should go out. Press the Reset button. The Data LED should light up brightly. Release the Reset button and the LED should go out. This indicates that the software is working. All looking OK'? Power down, install additional RAM chips to suit your memory requirements, and power up again. Repeat the above test procedures using the Copy and Reset switches. A simple RAM test is performed before the LED will flash. This test may not show up a shorted track, or a faulty RAM in some cases. If you have a suspect RAM, it can be further tested on its own in the Data bit 7 position by setting Copy ON and power up. The LED should flash at approximately 3Hz. If at any time the LED flashes at lHz, then a RAM fault has been detected. Loopback test Now power down, connect the output port pins 1 (STROBE), 10 (ACK) and 11 (BUSY) to the input port pins 1, 10 and 11. This can be done by simply plugging the input and output of your IBM printer cable into the BPIO board. If your input and output can't readily be connected together, then three jumper leads can be used to connect pin 1 to pin 1 etc. When this has been done, set Copy OFF, power up and press Test. This Test function outputs a sign on message to the printer. In this case, it outputs a string of characters to its own input port that keeps cycling through the buffer until the Reset button is press- ed. The Test function will light up the Data LED to about half brilliance. Now power down, connect a printer, set Copy OFF, power up and press Test. If all is well you should get the sign on message complete with memory size information. When the test facility is used, a ROM check is also done. If any byte in the ROM is incorrect then an error will be reported on the printout. Power down, have a quick read through the operating instructions and connect your computer and printer. Power up, and try printing a file. It either works OK or doesn't work at all. If it works then you can slap on the lid and forget it. If it doesn't work then Don McKenzie's instructions include an extensive troubleshooting procedure which should get you out of trouble. Thousands of this printer buffer have already been built so it's been well debugged. At the price you can build it yourself, it will make a very good add-on for your computer. ~ Where to buy the parts A short form kit of parts for this project is available from the designer, Don McKenzie, for $39 plus $3 for packaging and postage. This kit comprises the double-sided PBUFF board , an EPROM containing the software, and the assembly instructions. If you want the small 0B25 to Centronics socket adaptor board, that will be an extra $9.00. Write to Don McKenzie, 29 Ellesmere Crescent, Tullamarine, Victoria 3043. Note: copyright of the PCB patterns and the software in the EPROM is retained by Don McKenzie. 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( ) :"\ ~ ( ) • Talkover facility • Separate headphone level control • Parch switch bank • Individual controls for Microphone, Phone 1&2, Aux. line 1&2, and Master slide level controls. Bleryl up to two magnetic or crystal tumllblea, two tape decka and two microphone■ • all at once II FULLY PROFESSIONAL SPECS: II ~ 10" WOOFER :FLEX C 3280 WERE $1, 199pair S599 A PAIR m m J> :a 368D x 'JIXJW X 940Hmm LY .,,:a SA-130 Conl>fete with crossovers and cabinets. 1'JOWRMS ~rhandling. Cabinet size C 3270 WERE $799 NO i1.r u ar-r- j 1, I ( ) I I \ 11 \ I · I~ . Input· Mlc 1: 0.5mV, 600 Ohms, Mlc 2 : O.SmV, 600 Ohms (I.ow Imp.), 2.SmV, 10k0hmo (low Imp.I; Phono 1&2 (Mag .) 3mV, SOkOhms; Phono 1&2 (Cry,). 150mV, 10a(OhmI; Tape/TLW'I« 1&2150mV, 10GI.Ohma. 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C9010 Normally $39.50 ....... 0 0 0) 0) 0) co 0 0 en (.) -z CALLMASTER DUAL TAPE TELEPHONE ANSWERING MACHINE Why pay $299.00? 0 a: w w ~ a: d,al,rs.) 12" Guitar/Piano Loudspeaker MINI ALARM Great for door, window, cupboard, swimming pool gate etc Unit fixes to stationary surface while magnet fixes to moving part. When set off the unit emit5 an ear piercing schrreeech , (90db at 30cm), simply switch on toann. S 5315 Normally $16.00 < ...J ...J (ExcbuiJ1e to Allro11.i.cs 11,u/. Pacifu: AJ1ialio11. outlets in Australia - sorry, 11.ol aYailable from Altro11.ics Operates on 9V battery ~ a: u. Y $169.00 c9010ONL Now an amazingly low $25.00 Save more than 36% A 0512 $179.00 C r- ,, ::D $300.00 a: C 2015 10 Watt PVC For one month only reduced from ' 1 $1 5 .95 to $10.00. Buy 6 or more for only $9.00each z 0 J: Solar Powered D. Desktop Calculator This impressive new 12" speaker will enhance any musical instrument Amp system. 97db SPL at .SM. Designed principally for guitar and piano, this reproducer will handle '2J)QW intermittently or 150W continuous. 8 Ohm, 50mm voice call, MASSIVE 4kg magnet. Fantastic Value! I Weatherproof Horn I Loudspeaker I 5 I I ExcrU.nJ,ff1ei<ncyands,,,u,dcwrity. C 2027 Normally $69.00 I During October only $60.00 Professional Horn Speaker for lOOV line PA systems. Multiple input transformers enables power settings between 1.25 and lOOWatts. 6 or more $50.00 each Save $19.00 each I Solar Powered LED SPECIALS I Pocket Calculator · z 0140 3mm RED LED 'Runs/or,,,, without bo#,ri,s/ . I~ !each, 10up S.c each . :;, .J ·; ~ t ,"< i L !:-<:; : I J " I f ·· I rubber keys. I• I calculation• Chain I • Square ki::y With positive feel push button, 8-digit display • Standard four function • Full memory .,. '.:., ,_. _,, J.t<..., • 8-digit mini-desk-top calculator • 3 key memory • l'ercent key with add on/discount calculation• Square root key • Large plus key Size: 123 x 107 x 23.5mm Weight l!Og multiplication and division • Auto-constant calculation root 1 HEAVY DUT PCB RELAYS NEW NEW NEW PRODUCT 1 "" 1 ' 1 81 9 Pe, f•ctfor h;;,._ o: ~jµ.- K 1915 Was $45.00 A special bargain this month $39.00 --===--a Were 20c each Now 10c X 1060 This project will sense a door opening in a large or small room and sound a two--tonc chime. It docs not have to be anywhere near the doorway as it uses an ingenious sensor to detect the pressure change caused when the door opens. Ideal for use in office, shops, doctors surgeries, chemists etc. a pair Alpha-numeric gnd. Pre-drilled 0.9mm. 2.5mm spacing x 95mm wide. H 0711 95 x 304 $5.95 This month $5.00 H 0712 95 x 152 $3.50 This month $3.00 H 0714 95 x 76 $1.95 This monlh SI.SO 8 Ohm 0 w d r- each or Economy Series Weatherproof Re-Entrant Horn Speaker w ::D $160.00 Vero Type Board Features: C m C3100 This month only $10.00 Save an incredible 37.5% • Outgoing ~ssage variable from 30 to 120 sec. • Announcement-only mode • Incoming message is voice controlled • Incoming call can be monitored • Rapid erase • Has built-in microphone - great for dictation 0 z m - ::D 0 I Massive Magnet and Sturdy Diecast Frame I "'C ::r;: - Z 0150 5mm R-E ..D Q L~EiD~~;~:~:~""·· · I Were 18c each Now 10c ' each, 10up Sc_each Z 0149 SUPERBRIGHT 5mm RED LED Were 40c each Now 30c each, 10up 25c each • Low profile only 25mm high• 12V DC coil, • l xC0,5A S 4077 $5.00 each 10up $4.00ea 24V DC coil, 1 x CO, 5A S 4078 $5.00 each 10up $4.00ea PHONEORDER TOLL FREE ALTRONICS 008 999 007 m m )> ~ ::D 0 -0z CJ) 0 0 0) (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 dollars installing cables 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 the loungeroom, family room or hallways. Mowits up on the wall or on top of bookshelves etc. Detects m ovement within area of 9M by 9M. s 5280 $129.00 MINIMUM Remote Piezo Alarm FUSS MAXIMUM SECURITY r,... 0 0 a, O') O') a) 0 0 en s 5290 $125.00 Features: • Wireless receptiun of external or internal sensors or detectors • Selectable home or away modes. Allows internal or external arming or just external to provi de protected movement inside the bu ilding • Built-in piezoele ctric siren g.ives different signals for different functions • Sends signals do wn power lin:: to activate one or more remote sirens S 5265 Take It with you when you move 0 Detector/Transmitter Unit (Reed Switch) a: ~ <( w w .... a: s 5270 :c c. :0 s 5275 $59.00 m a r r :0 m m $55.00 4LTilOnlC) PHONE TOLL FREE 008 999 007 PHONE TOLL FREE 008 999 007 Perth Metro & After Houri (09) 328 1599 ALL MAIL ORDERS P 0 . Bo x 83 50 Perth Mail Exchange WA6000 ALTRONICS RESELLERS Chan c es are ther e 1s an A ltro n, cs Rese ller right n e ar yo u - c hec k this I1s1 or p no ne u s for detai ls o t t he neare st deal er PleaH Note : Rese ll ers ha ve to pa y the c o st of fre ight and in suran c e and therefor e the price s charg ed b y 1nd 1v1 d u al Oea te r s may va ry s11g nt1y from t t'l1 s C atalogue - in many c as es. howe ver . De ale r pfl c e s w ill sttl l repr esent a s1gn 1f 1c ant co st saving fr om pric es cha rge d by Altr cn 1cs Com pe ti to rs Don 't forget our Expre11 Mall and Phone Order Servtce • tor the co■ t of I local call, Bankcard. Vl aa or M ■■ te rc ■ rd holder ■ can phone order tor aame day d ■ 1s,atch . Blue Rlboon DHle,1 are highlighted with a ■ These Dealers generally carr y a comprehensive range of A ltro n i c products & ki t s or wil l order an y required ,tern for you l> ~ :0 Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept . Sydney ( NSW Onl y) Colin Fobister (02 ) 437 4077 Melbcume (Vic / Tas Only) Bri an Sorensen (03 ) 811 9967 Perth (WA , SA , OLD , NT ) (09) 328 2199 174 Roe St . Perth WA 6000 WA :0 C .,, Country clients please allow an additional 48-72 hours a: z Keep it at the bedside ta.ble - allows you to arm the house perimeters when you retire or you can take it with you when you go out, arming your system after you lock the door. e NEXT DAY JETSERVICE DELIVERY C 0 s 5285 $99.00 e BANKCARD e VISA e MASTERCARD e w 0 w $349.00 0 z m 0 Consists of enclosed reed switch and remov able enclo:st:d magnet. a: 0 This handy accessory virtually duplicates the function of the Master Controller un it but at a more convenient location. System can thus be armed or disarmed without tlx: need to go to the Master unit. ""C :c Hand Held Control transmitter Unit Suitable fo r windows and doors LL ..J ..J Front Door Keypad Control Unit The main control receiver runs on 240V AC with a 12V l. 2AH battery for emergency back-up. All other units with the exception of the line carrier run on 3. 9V battery each. The average life expectancy is approx. one year . System works around 305MJ-U. frequency wOCre there is less chance of a false alann . The range of the unit is normal ly 80 nx:tres in open space . {.) -z This unit is an optional line carrier receiver. Receives signal through• AC' lUJ,e i.e. it would ideally be located in, say, the roof space and plugged into mains power. 0 -z (") en STANDARD DELIVERY 6 PACKING CHARGE $,1 .00 to 1Kg $7 over 1Kg AUSTRALIA WIDE - We pr oc ess yo u r o rder the day rece ive d and despatc h via Australia Post A llo w approx 7 d ay s from da y you po st o rder 10 when you rece ive g oods $7 .00 OVERNIGHT JETSERVICE - We p r oc ess your o rd er !h e da y rec e ived a n d despa l c h vi a Overnight JetMrvlce Courter tor d e liv er y ne xt d ay Coun l ry ar eas p lease all o w add1t 1o na t 24-48 hours We igh! l1m 11 3Kgs (3K gs cove rs 95% of O rde rs ) $10.00 HEAVY HEAVY SERVICE - - All o rders o f. 10 Kgs or m o re must tra vel Express Roa d - Please a llo w 7 days to r deliv er y INSURANCE - As w11h v111ua ll y ever y o the r A u str alia n sup p lier . we sen d g o Ods at co ns,g nees ri sk Sh ould you requ ire c om p re h ens ive i ns uranc e cov er aga inst los.s o r da m age p lease add 1% to or der value (m 1n1 mum c ha r ge $ 1) W hen p h o ne o rdering please requesl ·i nsurance· TOLL FREE PHONE ORDER - Bank c ar d .Vi sa . Mast e rcar d H o ld ers c a n phone o rder 101 1 free u p to 6p m Easte rn "" ta n da rd T ime Remem b er w 1l h ou r C>Yernlght JetMrYlce we d el i ver next d ay COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K .B.Electronics & Marine 212176 KALGODRLIE 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 C ITY 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 TODWOOMBA 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 WHY.ALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTO N George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 COUNTRY CDFFS 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 PHONEORDER TOLL FREE ALTRONICS 008 999 007 0 0 0) (0 (0 (0 0 0 -..J SERVICEMAN'S LOG ' ''Bar humbug'' - as Scrooge G) <at> <at> <at> Transmit Button Bar Code Reader Display contained, hand-held device, the business end of which contains a sensor unit consisting of a LED and a photo transistor. The body of the device carries a liquid crystal display and a couple of switches and there is also an infrared LED at the far end of the unit (see Fig.1). The scanner is held vertically above the bar code pattern, in contact with the page, and moved smoothly across it. If done correctly this will store the information in the scanner and present it on the liquid crystal display panel for checking. The scanner will also beep to confirm that the code has been read completely. The display shows the day, starting time, finishing time and channel (see Fig.2). Ideally the bar code would be published as part of TV program guides but as mentioned last month guide publishers have been slow t~ respond. Possibly because of this, the VCR makers include a set of stock bar codes in the instruction manual. While this may not be as convenient to use, it certainly overcomes the lack of published data. Having fed the information into the scanner and checked it, the user then points the rear end of the scanner towards the , VCR and presses the transmit button. This transfers the data to the VCR via an infrared beam. The VCR confirms that the message has been received and understood by saying "Roger". Well, sorry about that, it doesn't really. No - most VCRs give an audible beep and present the scanner reading on the VCR display. But I offer the "Roger" idea to the manufacturers for what it's worth - no charge! <at> Transmitting Section The problem -- OK, so Scrooge never serviced a VCR. But if he had I imagine he would have used that expression in more than its original sense, because there is a certain amount of "bar" humbug around at the moment. What's this leading up to? - well, we're going to dig a little deeper into one of the bar (bah) code systems mentioned briefly last month. I have two stories concerning the National Panasonic model NV-D48 VCR and one of them deals with bar coding problems. This is the first time I have encountered any of the bar coding systems at service level. I've read about them, seen them demonstrated and played with them - but I have never had to service one. The most generous explanation for this would be that they are inherently reliable devices and this may well be so. But I think there is another factor - the "up-market" factor - which also has a lot to do with it. Although these systems have 4 been available for some two years now, their price tags have limited sales quite severely. One of my retailer colleagues tells me that he would have sold only about four such types in the last 12 months, compared with over 100 of the more conventional variety. Anyway, whatever the reason, this was the first time I had to put theory into practice. And it occurred to me that many of my readers may also have lacked the opportunity to gain hands-on experience with these devices. A brief run-down on how they are used may therefore be in order. The bar code scanner is a self- Bar Code Reading Section Digital Scanner On/Off Switch Fig.1: simplified diagram of the Panasonic bar coder with the essential features identified. Data is transferred to the VCR via an infrared beam. 50 SILICON CHIP would say Now for the specific problem. The customer rang to say that he had a National bar-code type VCR which he had bought about nine 1 V"~~~flrl -~::t~t~~~ C ~~,'fir/~·. f -:3 SOROOGE: Ft:><E:.'S -n-tE:. Ft'R.'SI ~ CO'D~.,oo months previously (ie, it was still under warranty). Apparently the bar coder had worked well until recently but was now behaving erratically. Sometimes it would record the information correctly but at other times it would baulk, either recording only part of the code or failing to record anything. There wasn't much I could do over the phone but I did establish that, when the scanner did load correctly, there was no problem in transferring the data to the VCR. In short, the problem appeared to be confined to the scanner so I suggested he bring it in, along with the instruction manual and the stock bar codes. He turned up a couple of days later and from the instruction manual I established that it was the model NV-D48; a model for which I had a service manual. A quick demonstration by the customer confirmed the symptoms so I suggested he leave it with me until I had time to delve deeper. When I finally addressed the problem I went through the same ritual as the customer - and came up with the same result; at best some of the code would be recorded, at worst nothing. My next move was to study the instruction manual in detail. As far as I could determine I was doing all the right things but one point did emerge. The instructions were quite emphatic about the need to clean the opening at the tip of the scanner, in front of the sensor, to remove any fibres picked up froni the bar-code paper. They even provide a small cleaning brush. My immediate reaction was to query whether the customer had followed this routine and I took the trouble to phone him and raise the point. He was quite adamant - he had cleaned the unit regularly, particularly after it had started to misbehave. Nevertheless, I went through the cleaning routine myself but without result - the thing was as cranky as ever. I tried again - still no joy. So I had to admit defeat and ask for help. I rang the National service department and contacted one of the technicians whom I know particularly well. Having listened to my story his first question was: "Have you cleaned the sensor opening?'' When I assured him that I had · several times - he was somewhat taken aback. As far as he could recall, there had been no electronic problems with these units so he was not able to suggest any approach. More to the point, if it was an electronic fault it was likely to be a nasty one; something not lending itself to field service. He was anxious to see it and suggested that I send it in to him. That was fine by me and I had it in the post in short order. And in due course it was returned, in full working order, and repaired nocharge under warranty. But in the manner of many service departments, there was no indication as to the nature of the fault, or what had been done. This is a most frustrating situation and one which the organisations concerned could well investigate. How do they expect their agents in the field to provide the best possible service without adequate feedback? After all, experience is the name of the game. Cat with cream Fortunately, I was due to meet the technician at a semi-social level within a few days, so I bided my time. When I did catch up with him, he smirked like the cat that had swallowed the cream. "Oh, there was nothing really wrong with it" . "What do you mean - if there was nothing really wrong with it, what was wrong with it? Come clean". "Well, the sensor unit was all fouled up with paper fibres and it needed cleaning properly". That was a bit of a blow. "Now wait a minute", I replied. "Come clean again. The customer had cleaned it several times and I cleaned it several times. And you say you cleaned it and it came good. What gives?" And that's when he stopped smirking and gave me the full story. It appears that the brush cleaning technique wasn't really good enough (more on that in a moment) and it was necessary to dismantle the device, remove the board and withdraw the sensor unit from the tunnel in which it sits, then thoroughly clean the face of the sensor unit. (The face of the sensor unit is set back from the opening by some 2-3mm). That's all very interesting from a servicing point of view but it does E) SU M© TU WE TH FR SA ON I ' ,_,c,c, ,_, D '-':,c,.c,c, ,_, .u ,_, OFF -, ,-, .,-, ,:,c,.c,: 0 Date Display e Start Time Display E) End Time Display 0 0 Channel Display Check Indicator Fig.2: this is what the display on the Panasonic bar coder looks like. Other makes and models would be similar. OCT0BER1989 51 SERVICEMAN'S LOG -CTD raise a question about the basic design. Although nobody is saying very much, reading between the lines I get the impression that this is now an acknowledged problem. But what the answer is I'm not sure. However, there are some additional points to consider. On the one hand the customer is a prolific user of the scanner; he would use it at least once every day. On the other hand the paper on which his bar codes are printed is a fairly good quality semi-gloss art paper which should not shed many fibres. So what happens if a similarly prolific user has access to codes printed on common newsprint? I shudder to think. At the very least I feel that a better cleaning brush or cleaning technique is required. Hopefully, something may eventuate. In the meantime, be prepared to do a thorough cleaning job. The next job As noted earlier, my next story also concerns an NV-D48 VCR. But there the similarity ends because it had a completely different fault. However, it did provide an opportunity to study some of the "digital" features more closely and learn something about their appeal. This machine was brought in by a lady customer, who simply turned up at the shop with it and a tale of woe,. The machine was quite new similar to the previous one - and therefore still under warranty. And the lady's complaint was that there were three or four white bars across the screen whenever she tried to play a tape on it. As well, a tape recorded on it would exhibit similar symptoms when played on another machine. It wasn't convenient to try the machine while the lady was there and in any case, my impression was that her description was quite accurate. So I said, "Leave it with me." When I did get around to checking it, I found that the lady's description was in fact very accurate. It was also rather disturbing because I hadn't seen anything as bad as this before. There were three or four noise bars, about 12mm wide, across the picture, similar to the single noise bar sometimes caused by a minor tracking error but far worse. The first thing I tried, without much conviction, was the user's tracking control, just in case it might provide a hint. It had no effect whatever - which probably meant something but I wasn't sure what. Bur WHEN ·11-\\S -PA"tr6-'RN CAN\E:. UP \"\ W~-S L-\KE:. NOT'\-\\NG 1 ~t> ~'R 'SE.E-N ~ ~ 0 1 • 52 SILICON CHIP Upper Cylinder Remover Jig (VFK0341) Handle LJ \. Soldered Portions Fig.3: this diagram shows the upper and bottom cylinders of the Panasonic drum assembly (separated for clarity), as well as the puller used to remove the upper cylinder. I then pulled the machine apart to the point where I could view the drum and transport system, while leaving it in playable condition. My first move was to check for any signs of oxide fouling. In fact, it was virtually spotless as I would have expected in such a new machine. Nevertheless, I went through the motions of giving it a thorough clean just in case but I wasn't really surprised when that achieved nothing. So where to next? I decided to set up the CRO and examine the output from the video heads in the playback mode (this procedure was covered in some detail in my April notes). In this case, test point TP3001 on the main board provides the RF output from the heads, following the head amplifier, and test point TP2001 provides the switching pulses to lock the timebase. The resultant CRO pattern from · this setup, using a standard test tape, should be a series of rectangular blocks which run together almost indistinguishably. Any suggestion of a triangular shape indicates a tracking error. But when this pattern came up it was like nothing I had ever seen before, either in real life or in the text books. It was not simply a mat- ter of each block being triangular; each block had three or four triangles in it. And, at the same time, the waveform amplitude was substantially reduced. Initial checks But what would cause such a gross tracking error? Or was it something more subtle? In desperation I decided to attack the left and right guide posts which are normally used to adjust the tracking. I shifted each guide post adjusting screw by half a turn, being very careful to note the original setting so that I could return to it. This had absolutely no effect one way or the other, which in itself seemed surprising. I was rapidly running out of ideas by now. Since it didn't seem to be a tracking error, at least in the conventional sense, the only possibility I could think of was a head problem of some kind. It was a long shot but it could not be ignored. One way of testing heads for wear is to use a head tester. This is a device which measures the "Q" of the windings and presents the result on an arbitary scale running from five on tlie left, to zero, then into a red area on the right. Five indicates a perfect head, anything between one and zero is poor, and anything into the red has really had it (my model is a Telesonic TE225). The major advantage of this approach is that the heads can be tested in-situ, the only requirement being to disconnect the lead to one side of each winding - four in this case - which is simple enough. So this was done - and produced exactly what I would expect from a near-new machine; "fives" all round. So that was that. I was really scratching now and the only thing I could think of was to unsolder the remaining four head drum connections and remove it for a more detailed examination, though I had no idea what I expected to find. Removing a head drum can be almost impossibly difficult or quite easy, depending on how one goes about it. You can try pulling it off with your fingers, which can be tough on both the fingers and the drum or heads. depending on how - . . I • t . f-~- . / t·. ~· ~ --•3 ff3 ~ ' ;;;[~/ . ... ( 3 ~ \ I ONE. w~'-t Ol= -rE:'Si\NG ~t>S ~ \,JEAR \6 "'t"'O use:. ~ \-\eA'O 1"E:-S"$1< lucky you are. Or you can do it properly, using a puller which is made for the job. It's really just a scaled down and refined version of an automotive wheel puller [see Fig.3). So I pulled the drum and gave it the best possible visual examination I could, even though such a check is of limited value. And, in fact, I found nothing about it to make me suspicious. But I did find something else. A complete drum assembly consists of two drums: a rotating portion which carries the heads [the upper cylinder) and a fixed drum, or bottom cylinder, which sits beneath it. This latter serves to guide the tape off the upper cylinder while holding it accurately TETIA TV TIPS Sony KV1300AS Symptom: Erratic horizontal sync, even with horizontal hold adjustment turned hard on. Picture usually out of sync at switch on but pulls in after a minute or two. Resulting picture is out of centre with wavy edges. Cure: C523 (1 00µF 25V electro) unserviceable. The cap showed no leakage and normal capacitance but would not work in this circuit. The cap is a filter on the main 18V rail but its failure only showed up on the horizontal sync. AWA-Thorn VCR ATV4 Symptom: All functions normal except that when Forward Speed Search is released the capstan motor speeds up instead of slow- ing down. Sounds as though it's going into orbit! Full servo alignment will correct this fault but introduces another - very slow recovery from Forward Speed Search with the sound unmuted. Cure: Adjust "speed search circuit" with VR408 and VR409, as per item 2-8 on manual page 24. This adjustment is a vital part of servo alignment but in the manual it's separated by 1 0 pages from those fnstructions and is often overlooked. 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. OCT0BER1989 53 its location was such that the tape would have been approximately half on the upper cylinder and half on the bottom one. And the gunk would have been lifting the tape clear of the upper cylinder and the heads at that point. It may also have allowed the tape to move up and down slightly. But what was this gunk, and where did it come from? I'm afraid I can only guess. Although I recovered it, it was so small that its composition was impossible to determine, short of a well equipped laboratory. For what it's worth, my impression is that it was some kind of bituminous material. When the lady came to collect the machine I quizzed her as to the brands of tapes she used. I wasn't really surprised to learn that she used only the top brands; no el cheapos for her. Nevertheless, I feel that a tape is the most likely source of the gunk. Maybe it was one chance in a million whereby a good tape became contaminated, but that seems the most likely explanation. There was only one mildly sour note about the whole thing; the fault, not being inherent in the machine, was not covered by warranty. But the lady didn't quibble; she was happy enough to see the machine working again. SERVICEMAN'S LOG -CTD in position. It is formed with channels or " lands" in which the tape sits. And now that I had removed the upper cylinder I had a better view of the front of the lower cylinder, which is otherwise difficult to see because of its proximity to the cassette carrier. Using a large "reading glass" type of magnifier I was able to to give this section a much better examination. And that's when I saw it; a tiny black speck on the land area, at the top of the cylinder, directly in front of the cassette carrier. Once having seen it I was able to juggle a jeweller's loupe into the available space and get a rather better look at it. It was truly black, not at all like oxide, and appeared to be about half the size of a pin's head. And it wasn't just discolouration; it was a solid raised lump. I tried to remove it using a cotton bud but it wouldn't budge. Then I tried an alcohol soaked tissue around the end of my finger and even this didn't move it the first time. But it came away at the second attempt, leaving a faint dark stain behind. This was cleaned away with a few more wipes of the tissue. What was it? So, was that it? It seemed to be stretching things to blame such a gross fault on such a tiny particle but there was only one way to find out. I replaced the drum, resoldered the connections, and ran the tape again. And up came an almost perfect picture. By that I mean it was visually perfect, although the CRO pattern indicated a marginal tracking error. This responded to a very small adjustment of the guides and was, I imagine, an aftermath of my previous adjustments. And yes, that was it; all that trauma was caused by a near invisible speck of gunk. I'm not certain as to the exact mechanism by which it caused the effect it did but The thirst for knowledge / 1m, 'J: "D\SC.'f<~E:"i""L-Y ~,zze:-p "11-\~ t..A'D'-f A'BOV'r' 1lHS A'SPE:°' O F 11-1 ~ (V'\ACH IN e:..,u~.... 54 SILICON CHIP On a broader note, seeking to add to my knowledge of bar coders and how useful they are, I discreetly quizzed the lady about this aspect of the machine. Alas for my attempted survey; it appeared that she had hardly used this facility. The reason she and her husband had selected this machine was because they also owned a video camera and had a need for good editing facilities. Apparently the picture-in-picture, the various search facilities and the indexing system were just what they needed to provide precise and convenient editing. Warming to the subject, she went into this is some detail but I have to admit she lost me half way; she was much better informed about this aspect of the machine than I. I shall have to try to catch up. ~ BOOKSHELF Transistor handbook sistors, it is the ultimate reference. It costs $214 for each annual edi- tion or $253 if the update edition, due March 1990, is included. Our copy came from the Australian agents for D.A.T.A. books, J.H. Book Services Pty Ltd, PO Box 311, Chatswood, NSW 2067. Theory handbook for radio amateurs D.A.T.A. Digest: Transistors. 59th edition published 1988 by D.A.T.A. Business Publishing, San Diego, California. Soft covers, 215 x 279mm, 1423 pages. ISSN 1040 0230. Price $214.00. This huge reference is updated regularly and is acknowledged as the most comprehensive source book for transistors. Data Business Publishing has editions on digital, linear, interface, memory and microprocessor ICs, on diodes, thyristors, power semiconductors and optoelectronics. All are huge and encompass a mind-boggling number of semiconductor devices. This 1988 edition on transistors features 56,802 current devices. No doubt the 1989 edition (due in September) will have even more. The D.A.T.A. Transistor Digest is far more comprehensive than some of the transistor substitution handbooks that are currently available. It has an alphanumeric index of all the current transistors which refers you to a page and row number where all the transistor specs are listed out. Another section lists all the transistors and gives a substitution together with the name of the manufacturer. After that, what can you say. The listing goes on and on for hundreds and hundreds of pages, 1423 in fact. If you need to source tran- Radio Theory Handbook for Amateur Operators, by Fred Swainston. Published 1988 by Prentice-Hall of Australia. Soft covers, 211 x 277mm, 345 pages. ISBN O 7248 1044 7. According to the preface, this text "has been written to cover the Department of Communications syllabus for the Novice and Amateur Operator Certificate of Proficiency (AOCP). It contains the theory necessary to pass the Certificate of Proficiency and is written to be concise and easy to understand''. Superficially, this book does what it sets out to do. It presents subject matter applicable to the complete syllabus for an Amateur Radio Operator's ticket and I daresay that someone who went through the text and used the answers presented for the sample questions in each chapter would get a ticket. But whoever wrote it or edited it does not appear to know very much about electronics. The explanations of how circuits work are poorly written and often quite wrong. Furthermore, quite a few of the diagrams are badly drawn, often with wrong battery polarities or just plain wrong. In fact, the book comes with a loose correction to a mains filter circuit which is shown on page 218 with the Active and Neutral transposed at the output. The amended circuit shows the Active and Neutral terminals correctly but shows .047µF 500V capacitors connected between both sides of the mains (ie, Active and Neutral) to Earth. That's two mistakes in one go. First, the capacitors concerned should be no larger in capacitance than .0lµF and second, they should be rated at 250V AC. As another example, on page 212 is a circuit of a lead acid battery charger which supposedly can be varied in output current from 1 amp to 4 amps. No values are shown on the circuit (as is the case on circuits throughout the book) but as shown the circuit can only vary the output voltage, not the output current. If the above is not sufficient criticism (we can cite plenty more examples), then we should also say that the book is solidly rooted in the past. For a book that was first published in 1988 it ignores a great deal of electronics that has been developed in the last twenty years or so; it makes virtually no mention at all of integrated circuits or digital circuitry (OK, there are a couple of pages, 102 to 104). As far as we are concerned, the book can't be recommended at all. There are so many examples of poor writing, errors in fact and in circuit diagrams that it deserves to be thoroughly rubbished. Our copy came from the NSW division of the Wireless Institute of Australia. We suggest that they send their remaining copies to the paper recyclers. OCT0BER1989 55 C1-118A 20MHz DUAL TRACE OSCILLOSCOPE * Frequency range: 10Hz to * Display: CH1, CH2. * * * * 20MHz. * Deflection Factor: 5mV steps (up to 10V) 1, 2, 5 sequence. * Pulse Rise Time: 17.5ns. * Sweep Rate: 0.05us to 50ms/DIV. 1, 2, 5 sequence. * Free-running sweep mode with synchronization * * * NOW $399.00 WAS $499.00 from 10Hz-20MHz signals and manual setting of the required triggering level. 60 x 80mm screen. Includes 2 x 1 :1 10: 1 probes. 1 2 months warranty. * * * * ONLY $499.00 SEW ST-3501 DIGITAL MULTIMETER LABTECH 1 Frequency Range: CH A: 1OHz to 100MHz, CH B: 100MHz to 1GHz. Input Sensitivity: CH A: 20mV RMS, CH B: 15mV RMS. Display 8 digit. Gate Time CH A: 0.01 s, 0.1 s, 1s, CH B: 0.027s, 0.27s, 2. 7s. GOODWILL GFG-801 SG 2MHz FUNCTION GENERATOR Frequency Range: 0.2Hz to 2MHz, continuously variable. Output Waveforms: Sine, Triangle, Square, TTL pulse and Ramp. Output Level: >20V P·P Open Circuit, 1DV p-p into 50ohms. Variable Duty Cycle: of 1 :1 O to 10:1. ONLY $299.00 FINEST 3487A AUTO RANGING DIGITAL MULTIMETER ESCORT EDM-1122 DIGITAL MULTIMETER * * INCLUDES FREE SOFT CASE * * * * Display: 3.75 digit LCD with 41 segment Bargraph display. Autoranging: AC V, DC V, Ohms, Current (20A AC/DC), Freq. Diode Test and Continuity Test. Manual ranging and Data Hold. Relative Mode and Min/Max display. 12 months warranty. ONLY $144.00 * Display: 3.5 digit LCD. * Ranges: AC V, DC V, Ohms, AC/DC A (1 OA), Capacitance, Transistor Test, Diode Test. * Audible continuity. * Includes probes. * 12 months warranty. ONLY $98.00 LCD DIGITAL * * * * THERMOMETER Temperature range: -40 to +SOC. Presettable Hi-Lo alarm. Stainless steel probe with 1m cable. 1 sec/15 sec sampling cycle. ONLY $39.95 * * * ONLY $150.00 * * * * 50MHz trequency response. 1 Ons pulse detectable. LED displays logic Hi/Lo, pulse , high impedance, V+ & V-. Pulse latch and TTL/CMOS selection. ONLY $39.95 * * Display: 3.5 digit LCD. Ranges: AC V, DC V, Ohms, Current (20A AC/DC), Capacitance, Frequency, Diode Test, Transistor Test, Logic Level Test. Audible continuity. Includes probes. 1 2 months warranty. LOGIC PULSER 50MHz LOGIC PROBE * * * * * 12 MONTHS WARRANTY 0.5Hz/500Hz purse rate. Automatic output polarity. Trigger input & output. Overvoltage protection. 1 OOOmA output with low duty cycle pulse. ONLY $39.95 Business HOU's DAVID REID ELECTRONICS 127 York St. Sydney NSW 2000 Phone: (02) 267 1385 Mon - Ffi Tlusday SatlJ'day 8.30 - 5.30 8.30 · 7.00 9.00 - 1.00 ARLEC DIGI-SCALE BLOOD PRESSURE MONITOR ULTRA-SONIC CLEANER * DIG I-SCALE will measure from 1 gram or 0.1 ounce up to 2kg or 4Ib 4 oz. * Convert from grams to ounces or ounces to grams using a select key * Various items can be individually weighed in the same container using the reset key * 240 volt ( plugpack not supplied) or battery operated * 12 month warranty * * Measuring: Oscillo-Metric method • Range: 0-300mmHg cuff pressure 40-150 pulse/min pulse rate * Accuracy :!3mmHg. pulse rate +5% of reading * Pressure build-up: squeeze bulb Ideal for cleaning drafting pens, watches, photographic filters, or even dentures. * 240 volt operation. ONLY $150.00 ONLY $59.95 NOW $99.00 SAVE!!! 5.25 " D.S.D.D. DISKS NO NAME BRAND PKT-10 NOW $6.45 SAVE!!! " SP-4.4" WOOFER 6.5 " POLY WOOFER * Freq. response: 62Hz-8kHz. * Sensitivity: 80d8. * * * 8 watts RMS. 8 ohms. * * * * WAS $11.95 NOW $10.00 * 100 watts RMS. * Freq. response: T0-2kHz. * Res. frequency: 23Hz. * Sensitivity: 93d8. * 8 ohms. 30 watts RMS . Freq. response: T0-3kHz. Res. freq: 36Hz. Sensitivity: 87d8. 8 ohms. NOW $89.00 ONLY $29.95ea. 12 volt to 240 volt INVERTER WELLER SOLDERING STATION WTCPS 12 " POLY WOOFER AS USED IN SUB-WOOFER KIT . . . (E.A. SEPT '89) 300 watt version . was $279.00 now $269.00 was $379.00 now $350.00 • Complete kit ADVANCED TEMPERATURE:: CONTROL SYSTEM * Complete with iron, PTA? tip, Sponge, • Fully built . 600 watt version Tip storage tray and Transformer. • Complete kit • Fully built WAS $149.95 40 watt version • This inverter is ideally suited to power low wattage mains appliances. • Kit only . now $85.00 NOW $129.95 QUICK MOUSE MICROSOFT COMPATIBLE * * * Tracking speed: 600mm/sec. Resolution: 200 DPI. Includes driver, test program and pad . wasmouse $99.95 NOW $89.95 . was $425.00 now$399.00 . ...... was $525.00 now$499.00 COMPUTER DATA SWITCH BOXES J b - -"'~':..;. _,;_~ -m ·....~ .. ;~ . ~ 1 , .. DB SERIES COMPUTER CONNECTORS ~ (SOLDER TYPE) ~ DB-25 TYPE and CENTRONICS TYPE 2-WAY . . was $59.00 / NOW $49.00 / ;::-,_,;;._ _ _ _ _____,_ 4 WAY .. was $89.00 \ """"' '"~.~ NOW $79.00 • BE QUICK!!! _ * *** * ** COMPUTER FAN 120mm. * *** Air Flow: 80CFM 240 Volt was $28.95 NOW $19.95 * Speed: 2600 RPM * DB-9 PLUG ALL ONE D8-9 SOCKET DB-9 BACKSHELL PRICE DB-15 PLUG $1.00 DB-1 5 SOCKET h D8-15 BACKSHELL eac D8-25 PLUG ~ DB-25 SOCKET ~ DB-25 BACKSHELL "' ·', FONEBUGALERT MINI PASSIVE INFRA-RED DETECTOR A must for all who value their privacy. A simple plug-in BUG detection device for your telephone . This little unit only measures 65mm H, 45mm W , 3 5mm D. Distance of 15mtrs <at> 1 05d eg range. Voltage requirements are 9 to 16 volts DC , and has NC alarm contacts , NC anti-tamper contacts both rated ONLY $34.95 <at> 24V DC 0 .5A. Mail Orders: P.O. Box 0103 Sydney NSW 2000 Fax: (02) 261 8905 WAS $99.00 P&P Rates $5-$25 $4 $26-$50 $6 $51+ $8 NOW $74.50 2-Chip Stereo Radio Last month, we described the main features and gave the circuit details of our new highperformance AM stereo receiver. This month, we show you how to build it. By STEVE PAYOR The AM stereo receiver is built on a small PC board coded SC 06108891. This board accommodates virtually all the parts and comes in two versions (Rev.1 & Rev.2), depending on the type of headphone socket used. As can be seen from the photos, the PCB assembly is mounted on the lid of a small plastic case. 58 SILICON CHIP Before you start soldering components on the PCB, a little preparatory work needs to be done to ensure that the tuning gang, volume control and headphone socket fit correctly. Also, the empty PCB makes an ideal template for marking out the front panel. The first step is to trim the edges of the PCB with a sharp file, stopp- ing just as you reach the copper. Do not remove the copper border as this forms part of the electrostatic shielding. The small gap in the border track is intentional without it this track would form a short-circuit for some of the magnetic flux around the ferrite rod aerial. Note also that the two corners at the headphone socket end of the board need to be cut away to clear the internal pillars of the plastic case. There are three slotted holes which need to be cut in the board. Two are for the tuning gang lugs and the other is for the anti-rotation lug on the volume control pot. Start each slot by drilling three 1mm holes side-by-side, then open these out into a complete slot with an Arlec Supertool or some similar device. Next, open out the hole for the tuning gang shaft to 6.5mm and the hole for the pot bushing to 11mm. Use a progressively larger series of drills to start the holes, then enlarge them using a tapered reamer until the parts fit perfectly. The tuning gang must be fitted with an 18.5mm long extension shaft. Fig.2 shows the details. It is held in place with a long 1OBA screw and should be a tight fit on the tuning gang shaft. In a pinch, a loose shaft can be pressed into service by coating the inside of the recess with Araldite (not the 5-minute type} or a high-strength anaerobic cement such as green Loctite 601, Permabond A168 etc. Headphone socket The headphone socket requires special attention. Currently, there are three versions available which can be used. The first version (for the Rev.1 board} has a plain, unthreaded bush which doesn't quite reach through the thick wall of the plastic case. To use this socket, the outside of the case needs to be spotfaced to On this style of headphone socket with threaded bush, you have to dig in with a screwdriver and break away the ground contact to prevent it shorting the right channel. After that, use a pair of needle-nosed pliers to crimp the metal bush so that it makes good contact with the ground sleeve of the plug. a depth of a little less than 1mm to enable the plug to reach the socket (more on this later}. The second version (also for the Rev.1 board} has a threaded bush which does reach comfortably through the case wall. Unfortunately, the internal ground contact of this socket rests right on the insulation between the right channel and ground sections of the 3.5mm stereo plug. On some headphones, it shorts the right channel to ground. The best thing to do here is to dig in with a fine screwdriver and bend the ground contact up and out of the top of the socket (see photo}. Next, reach in with a fine pair of needle-nosed pliers and crimp one corner of the metal bush inwards so that it makes firm contact with the ground sleeve of the plug. The horizontal location of the PCB is critical. It must be mounted so that the rectangular shoulder of the headphone socket is in line with the outer edge of the locating ridge on the case lid. OCT0BER1989 59 Virtually all the parts are mounted on the PC board. When installing the parts, keep all leads as short as possible and make sure that you don't mix the coils up. The four test points are used during the alignment procedure. The third style of headphone socket comes from Dick Smith Electronics. It's easily recognised because it has three asymmetrical pins towards the rear of its body and one near the threaded bush for the ground contact (the others have five pins). You don't have to modify the ground contact on this socket but, because its terminal arrangement is different, you do have to use a modified PC board. For this reason, kits for this project from Dick Smith Electronics will use the Rev.2 version of the PC board to suit the DSE headphone socket. Note that the left and right audio channels are reversed with the DSE socket. To correct this, two in- I I0.25± .001 INCH 10 BA SCREW-l¥OUTSl:EDIA ALUMINIUM E j; ""~""H™"1 I ' • ENO OF SHAFT 4mm INSIDE DIAMETER (TIGHT FIT ON TOKO TUNING GANG SHAFT) Fig.2: details for the 18.5mm extension shaft. It should be a tight fit onto the tuning gang shaft and is secured with a long 10BA screw. 60 SILICON CHIP sulated links are used to swap the L & R signals over at the audio amplifier inputs (pins 1 & 9) - see Fig.4. Note also that one of the "R" pins· on the socket is soldered on one side only, to avoid a short to the nearby IC pads. One final point here: the pins on all types of headphone sockets are likely to be quite short - barely long enough to reach through the PCB, in fact. Tin the pins thoroughly before insertion, so that the solder will flow down into the PCB holes. A secure connection is vital here, because the headphone socket will be subjected to quite a bit of mechanical stress during normal use. Five of the holes in the PCB are for the tiny plastic locating pins on the underside of the socket (Rev.1 board sockets only). Drilling the front panel Having satisfied yourself that the tuning gang, volume control and headphone socket all fit snugly in the board, remove all but the headphone socket and place the board against the inside of the case lid to mark the outlines of the front panel holes. There are six holes in all: one for the 1/4-inch diameter tuning gang shaft, one for the 3/8-inch pot bush, one for the 3mm LED, and three for the board mounting screws. Two of the board mounting screws are directly under the ferrite rod, while the third mounting point is located right next to the tuning capacitor for mechanical stability. The horizontal location of the PCB is critical. The rectangular shoulder of the headphone socket must be in line with the outer edge of the locating ridge on the case lid. Vertically, the PCB is centred with respect to the front panel (see photo). Having marked and drilled the holes, the next step is to turn the front panel over and countersink the three holes for the board mounting screws. Do this carefully, so that the screw heads will be exactly flush with the surface. They will be covered over by the front panel label later on. Now fit the three countersunk screws with washers and nuts so that the board will sit 3.5mm from the panel. Tighten the nuts firmly as these screws stay permanently STEREO HEADPHONES 680pF 3300 Fig.3: install the parts on the PCB exactly as shown in this diagram. Don't use IC sockets as the extra stray capacitance could upset the performance of the MC13024. The 3mm LED is mounted on the underside of the PCB (see text). fixed in place on the front panel. One final test of your workmanship: temporarily refit the tuning gang and volume control, then drop the board down over the mounting screws. The capacitor shaft and pot bush should fit snugly in their holes and the two solder pads for the LED should be visible directly below its hole. If you are using the same metal knobs as on the prototype (Jaycar Cat. HK-7024 and HK-7022), the tuning capacitor shaft should extend 12.5mm above the front panel and the volume control shaft 11. 5mm. These shaft lengths should also suit the equivalent metal knobs from Dick Smith Electronics but check first before trimming the pot shaft. PCB assembly You can now start soldering the components to the PCB as shown in Fig.3. Mount the links and low profile components first, otherwise things will get awfully squeezy when the board starts to fill up. PC stakes should be installed at the GND, + 1V REF, AGC and Buffered AGC points along the bottom righthand coner of the board. To save space, we have mounted all the resistors end on. A lot of the resistors have a "hot" end and a "cold" end as far as RF voltage is The PCB assembly is supported on the case lid using countersunk machine screws, full nuts and washers. The screw heads should sit exactly flush with the lid surface so that they can be covered by the label later on. concerned, so it is important to orient the resistors as shown in the parts overlay diagram for best results. For example, if you reverse the 100k0 resistor across 14 (ie, have its other end long), there will be sufficient IF radiation to cause a noticeable whistle as you tune through the weaker stations. Take care with the polarity of the electrolytic capacitors. Note that the two .04 7µF capacitors in the 25Hz bandpass filter should be 2 o/o types with 5mm lead spacing. If you can't get 2 o/o types, 5 o/o greencaps can be used, provided they are selected to be within 2 o/o of value (ie, .046µF to .04 7µF). Now for the tuning capacitor. This must be mounted so that the OCT0BER1989 61 '_/ - R• The ferrite rod antenna is mounted using right-angled aluminium brackets and plastic P-clips. Don't use metal clips, as these will form a shorted turn. The coil can be secured with a cardboard wedge. INSULATED LINKS • Fig.4: this diagram shows the wiring changes for the Rev.2 board with DSE headphone socket. The two insulated links swap over the audio amplifier outputs to compensate for the headphone socket connections. either wide, medium or sharp. These options are selected by bridging solder pads on the PCB as shown in Fig.5. For city dwellers, the wide setting is the one to go for. Mounting the ferrite rod You will need a soldering iron with a fine tip to mount the LED in position. The top of the LED should just poke through the front panel when the board is installed on the mounting screws. wider of the two earth lugs goes towards the bottom of the PCB. Also, if you have keen eyesight, you will see that there is lettering on the back of the tuning gang. Just mount the tuning gang with "C3" towards top left. The Tako coils can be installed next. This job is straightforward since the pinouts are polarised but make sure that you don't mix the coils up. The 3mm LED is mounted on the underside of the board. Use a soldering iron with a fine tip and keep the temperature as low as possible. If you pre-tin the leads, you will only need a quick touch to finish the job. The top of the LED should just poke through above the front panel when the board is in62 SILICON CHIP stalled on the mounting screws but not by more than 0.25mm otherwise is will foul the perspex cursor attached to the tuning knob. Note carefully the orientation of the two !Cs when you install them on the PCB. Don't use IC sockets the extra stray capacitance from the socket could compromise the performance of the MC13024. The volume control pot specified is a PC mounting type. It is installed by bending the lugs for the front section through goo so that they mate with the holes in the PCB. The lugs for the rear section are also bent through goo and are connected to the board via short lengths of tinned copper wire. At this stage, you are ready to select the bandwidth option - As you can see from the photographs, we chose to mount the ferrite rod high above the PCB using two small right-angled brackets and plastic P-clips. Other mounting schemes could also be used, depending upon the available hardware. There are two points to watch here. First, don't use a metal clip around the ferrite rod as it will form a shorted turn. Second, leave one half of the rod unsupported so that the coil can be slid up and down to adjust the inductance. After the rod is mounted, check that it doesn't foul anything on the inside of the plastic case. A 100mmlong rod will fit comfortably. If the rod is any longer you will have to cut it. You can do this by filing right around it with a file, then snapping it like a piece of glass. The aerial coil is a standard prewound unit from Dick Smith Electronics. This normally comes supplied on a short length of flat ferrite rod but can be easily slid off and reshaped to suit the round rod. We wedged a strip of thick cardboard between the coil and the rod to give it a very firm grip. Don't rely on a blob of melted wax to hold the coil in place, because it won't. The coil must not move except when you want it to. The colour code for the coil leads appears to be fairly standard but if there is any doubt, you can identify the large and small windings with an ohmmeter. The "hot" end of the main winding (usually the plain lead) should be the furthest away from the secondary winding and closest to the end of the rod. Trim the leads so they will just reach their respective PCB holes with the coil sitting about 10mm from the end of the rod. Unnecessary lead length must be avoided since any vibration of the leads may cause phase shifts, thus disturbing the stereo image. To prepare the leads, carefully unwind the ends of the three silk covered strands and tin each strand separately with a hotterthan-normal iron. The silk covering and enamel insulation will melt away. Now twist the three strands back together again and solder them as one unit (two of the strands are for mechanical strength only). Does it work? Once the coil has been connected, the radio is electrically complete and you can give it a brief power-up to see if it works. We fitted a 2-pin PCB header plug for the 3V power connection to the board, which made testing and assembly much more convenient. At this stage though, the performance will be far from optimum since you have yet to go through the alignment procedure. Even so, you should be able to tune in local stations. Front panel Accompanying this article are two separate artworks for the front panel. One shows the main Sydney AM station call signs as well as the tuning frequencies in kHz. The other shows no station callsigns, just the frequencies. For Melbourne readers, we will publish an artwork to suit their station callsigns next month. Our apologies to readers from other parts of Australia but the author wanted a proper, oldfashioned tuning scale for his own use, hence the Sydney station callsigns on the upper label. · If yo·u live outside the Sydney or Fig.5: the bandwidth option is chosen by bridging solder pads on the PCB. We recommend that you select the 'Wide' option by bridging two of the pads as shown at far right. Fig.6: here are the dimensions for the perspex cursor. The edges can be smoothed with very fine abrasive paper and polished with "Brasso". Melbourne listening areas, it is well worth the effort to letter in a tuning scale for your own area, as tuning by numbers is a real nuisance when the frequencies are ·all multiples of 9kHz. Letraset is the answer here, and you can use a matt acrylic spray to fix the lettering in place. Tuning dials with station callsigns have all but disappeared these days, since most radios are now made overseas. This puts our little tuner one up on even the most expensive imports. Fixing the label Affixing the Dynamark label on the front panel requires great care to ensure that is accurately centred on the tuning capacitor shaft. The adhesive is so aggressive that you will not have a second chance to reposition it. The 3M literature suggests that you use a weak, mild detergent solution to "float" the label into place, much like the rego label for a car. We chose a different method. After the label has been trimmed, remove it from its backing and cut the backing in half. Now stick the backing back on to the label, leaving a central strip of adhesive exposed. If you have a light table, lay the plastic front panel on it and position the label using the targets and the light through the holes as a guide (the label material is semitransparent). Press down on the centre section to tack it in place, then remove the strips of backing and smooth out the label, always working outward from the centre to avoid bubbles. Small bubbles will disappear by themselves in a day or two, so you don't have to spoil the finish of the label by bursting them with a pin. The best way to open out the holes in the label is with the tip of a very sharp, pointy knife. The PC board can now be fitted to the front panel and secured with three nuts. Knobs and perspex cursor We chose solid aluminium knobs for our prototype. The larger tuning knob is fitted with a clear Perspex cursor which is something you will have to make from scratch. The cursor has a valuable role to play in the alignment procedure, so it is definitely worth the extra effort. Start with a small scrap of 1.6mm thick Perspex and cut and file it to the dimensions indicated in Fig.6. The edges can be smoothed on very fine "wet or dry" abrasive paper, using kerosene as a lubricant. The edges can then be polished by rubbing on a strip of cloth soaked with "Brasso". To scribe a really neat line on the cursor, you will need to grind a piece of old hacksaw blade so that OCT0BER1989 63 can be adjusted to a perpendicular position. You will notice that the tuning capacitor has a total rotation of slightly less than 180°. When tightening the grubscrew in . the knob, rotate the tuning shaft fully anticlockwise and set the cursor exactly in line with the horizontal line on the dial. The clockwise limit of rotation will then be at approximately 1620kHz on the scale. 2Bmm ALUMINIUM KNOB COUNTERSUNK SCREW (UNDER DECORATIVE LABEL) CASE LID PCB Teflon washer Fig.7: this cross-sectional diagram shows the mounting details for the PC hoard, tuning gang, LED and tuning knob. Note the Teflon washer between the Perspex cursor and the front panel. ing ink, allow it to dry for a few hours, then remove the excess ink by rubbing with a piece of clean paper. "Super Glue" (cyanoacrylate) is the only readily available adhesive which will glue Perspex to aluminium. On no account use epoxy. This may hold the Perspex for a few days but it will fall off when the epoxy hardens fully. Degrease the aluminium surface with acetone before glueing but don't let the solvent near the Perspex. With "Super Glue" you only get one shot at it, so fit a short stub of ¼-inch rod into the knob to act as a guide for centring the cursor. The perspex cursor is attached to the bottom of the tuning knob using "Super Glue". The line on the cursor should line up with the groove in the knob. Setting the dial there is just one tooth left on the end. File the tooth down to a width of about 0.25mm. This tool can then be used to scrape a neat, rectangular channel in the Perspex, whereas a scriber will only made a raggedy-edged scratch. Fill the groove with black draw- Now try the tuning knob (plus cursor) on the tuning shaft. Fig.7 shows the assembly details. If the cursor doesn't run parallel to the front panel, you can correct this situation by re-melting the tuning gang solder joints so that the shaft A useful finishing touch is some sort of thin, low-friction washer between the case and the underside of the cursor (see Fig.7). This takes some of the load off the tuning shaft when the radio is bumped and reduces the tendency for it to drop out of stereo mode. The washer is easily punched from Teflon sheet or you can look around for something in Delrin, Nylon, red fibre etc. Just before tightening up the grub screw, lightly squeeze the tuning gang and knob together to preload the washer and tuning gang bearings. Battery clamp The battery clamp consists of four countersunk screws, two tapped spacers and a scrap of Perspex sheet (see Fig.8 & Fig.9). To find out how to bend Perspex, refer to page 45 of the July 1989 issue of SILICON CHIP. Alternatively, you can use 1.6mm aluminium sheet instead of Perspex. Study the location of the batteries carefully from the photographs. They won't fit anywhere else. The top right hand corner of the battery holder comes very close 1.6mm PERSPEX OR ALUMINIUM SHEET .......,,. ..... ~ .! COUNTERSINK~ SNAP CONNECTOR TOP COVER (SEE DIAGRAM) ~ 2xAA BATTERY HOLDER 71mm I Fig.8: the battery clamp can he made from 1.6mm Perspex or aluminium sheet. The corners are cut off the cover plate to clear the dual gang volume control. 64 SILICON CHIP CASE BOTTOM Fig.9: the battery clamp cover is secured to two tapped spacers using countersunk screws. Note that the batteries must he positioned in the bottom left hand corner of the case. POLYSTYRENE CAPACITORS Made here in Australia? Made Special to Type? A Teflon washer must be installed between the front panel and the Perspex cursor. Before tightening the grub screw on the tuning knob, lightly squeeze the tuning gang and knob together to preload the washer and tuning gang bearings. This makes tuning easier and reduces the tendency for the radio to drop out of stereo if it is bumped. +Trim to outside of board outline f SILICON CHIP AM STEREO Fig.10: this full-size artwork is for the Rev.1 version of the PC board. The Rev.2 version will be supplied only with the Dick Smith Electronics kit. to fouling the dual gang volume control, which is why the corners are cut off the cover plate. We also used countersunk screws to keep the height to an a bsolute minimum. Finishing the case The on/off slider switch is located low down on the bottom right hand corner of the case, again to avoid fouling the components on the circuit board. The hole for the headphone socket should be drilled mid way along one edge of the case, at a height determined by measurement from the actual job. This end of the PCB can flex up and down quite a bit, allowing the headphone socket to align itself with the hole which should be a very snug fit. Use a 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 . 1 uF 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 ALLIED CAPACITORS AUSTRALIA PO Box 740 Brookvale, NSW 2100 OCT0BER1989 65 =-..,,;11=1-.T,i -·· 1 : -: 1 7. "J ; 1 ii• :..1 -==~•11 -1,= ':!!!!!f:Z - 'i'=<at> = I.,•, ~ i)\\ ,soo 1-----0-----' l<HZ sharp knife to bevel the upper inside edge of the hole to help guide the socket into it on assembly. If the socket you are using doesn't reach comfortably through the case wall, counterbore the outside surface 0.5mm to 1mm. A 3/8-inch milling cutter will do the job nicely but note that the plastic case must be securely clamped in a drill press, or disaster may result. Final assembly WIDE-BAND AM STEREO® [ Trim label to inside of line - - ••,=r- --=~1-/:.-Jii 1E!f=.<at> -=:a:!E:r-:r:; ::::=. ~ ~ ~ - ~ ~ ., • • ,,. _,:.ilff. 7 I Ii « ,·- = ◊~~ ,~~~ \f;,\\\\ ,soo l<Hz~-------1 o 1-----0-----' l<Hz LOCl<ED ;STEREO: WIDE-BAND AM STEREO ® [ Trim label to inside of line Fig.11: alternative artworks for the front panel. The artwork at top shows the callsigns for the Sydney stations in addition to the kHz dial markings. An artwork showing the Melbourne station callsigns will be published next month. When wiring the battery connector to the switch and the switch to the PCB, keep the power leads as short as possible. The power leads should also be tightly twisted together. This is most important as even a small inductive loop here will couple power supply currents · back into the ferrite rod antenna and may result in oscillation. Finally, if the self-tapping screws supplied with the plastic case are of the thread cutting grooved type, look around for some that will do less damage to the plastic when they are repeatedly removed and replaced. The idea is to use a screw which will cut a proper thread. Even metal theaded machine screws will do. Screw them into the pillars warm, then heat them with your soldering iron until the plastic softens and shrinks around the screw threads. When cold they will come out easily. Next month, we'll conclude with the full alignment details. ~ The batteries must be mounted in the bottom left hand corner of the case (they won't fit anywhere else). Twist the power supply leads together as shown to avoid inductive loops which could radiate supply currents back to the iclntenna. 66 SILICON CHIP 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. Monitor/Transmitter; LED Message Board Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For PCs; Simple Stub Filter For Suppressing TV Interference. March 1989: LED Message Board; 32-Band Graphic Equaliser; CD Compressor; Amateur Band FM Receiver. June 1989: Touch-Lamp Dimmer; Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CAO Probes. July 1989: Exhaust Gas Monitor; Extension for Touch-Lamp Dimmer; Mains Hum Sniffers ; Ultrasonic Car Burglar 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. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; Telephone Bell Note: November 1 98 7, December 1 98 7 & January 1988 are now sold out. December 1988: 120W PA Amplifier; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Receivers. 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. Use this handy form to order your back copies .---------------------------------Please send me a back issue for: □ February 1 988 □ July 1988 □ March 1988 □ August 1988 □ December 1 988 D May 1989 □ January 1 989 □ June 1989 □ □ □ D --7 □ June 1988 D November 1 988 February 1 989 □ May 1988 □ October 1 988 □ March 1989 July 1989 □ August 1989 □ September 1989 April 1988 September 1 988 n April 1 989 Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my D Bankcard D Visa Card D MasterCard Price: $A5.00 each (includes postage). Overseas orders add $A 1 .00 per issue for postage. Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_ _ / __ / _ _ NZ & PNG orders are sent by air mail. Name ___________________________ (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 Stree~-----------------------COLLAROY BEACH NSW 2097 Suburb/town _ _ _ _ _ _ _ __ _ __ Postcode____ OR FAX: (02) 982 9553 l I ~-------------------------------------J OCT0BER198Y 67 I ft THE AMAZING 3-IN-1 MODULAR TOOL... • • • • • It's a DRILL It's a SOLDERING IRON It's a SCREWDRIVER It's totally PORTABLE And It's RECHARGEABLE It's easy to handle and the pistol grip action leaves one hand free to make working a breeze! Comes complete with assorted drills, screwdrivers, solder accessories and charger. Check out our great price ... it's the best around. Cat T-5712 ~ POCKET SOLDERING IRON ERED' , ~ ~ THE PROFESSIONAL 'POCKET' SOLDERING SYSTEM The convenient soldering system from Portasol! Ifs a complete kit with the equivalent of 10-60 watts of power and temperature adjustment up to 400 degrees Ceisius. • A Pocket sized, temperature adjustable iron • 4 tips including hot knife and blow torch • Tip cleaning sponge • Heavy duty plastic case with clip-on iron stand • Butane powered • refills in seconds • Average 90 minutes continuous use A BARGAIN' s359s • Cat T-1370 Budget Mini Multimeter Hand-Held RC Oscillator The ideal meter for anyone who's starting out, or to use a rough and tumble model for the too~box. Ifs a well const1Ucted litt1e number that fits easily in your pocket and has inbuilt diode and fuse protection. 2K ohm/volt, $1 15 ranges plus dB and mirrored scale make it great for general test/ setvice work. cat Q-1000 A hand-held oscillator that's small enough to take anywhere. About the some size as a digital multimeter, it gives you 23 ranges of sine and square waves (switchable) between 20Hz and 1.5kHz, plus a x 100 range: 46 settings in all. cat Q-1220 7· s1 395 s~vE s3 1 G Digital capacitance Meter Ideal for the workshop, hobby bench, schools, labs ... anywhere! With 3.5 digit LCD readings over 9 ranges. Covers virtually all general usage capacitolS. Battery operated, it's lightweight and comes with handy carry case and leads. CatQ-1222 Complete with clip test leads. THIS MONTH Universal Panel Meter Universal 100uA panel meter that can be easily adapted for just about any situation - Volts, Amp, mA .. anything! Cat Q-2045 s9995 ----Safety Yellow 3.5 Digit with / ~ Plus FREE Portasole Cap and Hot Knife Tip! ft05 $ GREAT VALUE AT ® - Totally portable, butane powered soldered iron that fits easily in the shut pocket. Pro111des up to 60 minutes continuous use at lull power (equivalent of 60 watts). Temperature control from 10 to 60 watts. Ideal for setvice people, handymen, technicians, etc. 99 This has to be one of the smartest tools for hobbyist, handyman and tradesman alike. Modular components fix to a rechargeable battery pack (handle) and in seconds you can switch from a soldering iron to a drill, from a drill to a reversible screwdriver, etc. etc. A thousand and one uses around the home, office, etc. Just plug it into the mains socket and set it to turn appliances on/off up to 24 times in one day. Comes 95 with 3 sets of timer pins. Cat P-5700 $29 11.a.W.: • BALLINA: Ballina Electronics 897022• BOWRAL: F.R.H. Electrical 811881 • BROKEN HILL: Hobbies & Electronics 814091 • COFFS HARBOUR: Coffs Harbour Electronics 525884 • DENILIQUIN: Deni Electronics 813 872 • DUBBO: Chris's Hi Fi 821711 • FORSTER: Forster Village Electronics 545008 • GLEN INNES: John Sommerlad Electronics 323891 • GRAFTON: Repairs and Spares 421911 • GRIFFITH: Miatronics 624534 • INVERELL: lnverell Electronics 221121 • LEETON: Leeton Audiotronic 532800 • LISMORE: Decro Electronic Services 214137 • MOREE: Moree Electronic• 523451 • MUDGEE: Headware 723895 • ORANGE: Central West Electronics 829491 • NOWRA: Nowra Electronics 210722 • PARKES: Strad Music Centre 823388 • TA.REE: Brads Electronics 529 803 • WAGG A WAGG A: Phillips Electronics 218558 VIC:• Ml LOURA: Pullman Auto Pro 232 882 •MORW!LL: Morwell Electronics 348133 • SHEPPARTON: Phillips Electronics Pty Ltd 219497 • WARRNAM· BOOL: Marrtronics 829870 QLD: • AYR: Delta Electrix 131 5H •BUNDA.BERG: Bob Elkin Electronics 721785 • MACKAY: Stevens Electronics 511723 • MARY BOROUGH: Keller Electronics 214559 TAS:• BURNIE: Electronic City 314 780 •DEVONPORT: A.I.Electronics 248322 SA: •LOXTON: G & S Electrical 847495 • MT GAMBIER: Hutchesson's Communication Centre 250400 • PORT LINCOLN: Basshams TV & Comp World 822 788 • WHYALLA: Eyr Electronics 454 714 WAI ALBANY: Micro Electronics 412077 • BUNBURY: Micro Electronics 211222•0 A T · . i hi I ri I 11 • T · . . 3 $99 Cat N-1220 $195 oo sr,.VE S1· Tr, Diode & Continuity plus Battery Checking This one has all the usual ranges, including current to 10A and resistance to 200 megs, but it also has a continuity checker with a fast 100ms response time, a diode and transistor checker, plus a battery checker - it tests under actual load conditions. $ Cat Q-1445 SUper Glue 5000 Instant repaitS to \ virtually anything. Thousands of applications. There's no clamping, no fuss. In 3ml tube. CatT-1374 . • · . ,' SAVE S5 lmMI 7 9 95 Super Glue Remover If you oops! with the Super Glue, you don't have to be stuck with a problem. Super Glue Remover In hondy10ml container. Cat N-1221 i No wiring necessary - Installation is a breezel COMPLETE WIRELESS HOME ALARM All for only $399 Central Control Module Locate anywhere in the house - bookshelf, cupboard, etc. Just plug it into the mains and it's working. Our wireless home alarm system features instant/delay modes, five zones of protection, 4 function modes, builtin speaker and provision for an external speaker Includes: Remote Control Unit Central Control Module Remote Control Unit Remote Reed Switch Remote lnfrared Sensor Power Supply Carry it with you - all functions are in the palm of your hand. Remote command unit is used to switch the alarm system. Select any operating mode or use the emergency switch. Fits easily in pocket or purse. Cat L-5129 Col L-5125 Remote lnfrared Sensor s5419s Ideal for room, entrance or hallway security. lnfrared sensors are arguably the best security sensors you can get. This one gives 64 sq. metres coverage, Incorporates transmitter and has adjustable zone control. Cat L-5128 Remote Reed SWitch Magnetic switch and digital coding transmitter for u 9 with the wireless alarm syste1 '- Just the thing for securing do~ -s, windows, etc. Cat L-5127 0 s129 s5419s Additional Units Available Remote Control Unit Cat L-5129 $59.95 Remote lnfrared Sensor Cat L-5128 $129 Remote Reed Switch Cat L-5127 $59.95 Install It Yourselfl THE COMPLETE HOME SECURITY PACK Everything you need for professional quality security in one carry-home pack! It's the most complete home security system we've ever had in one pack and it's exceptional value to boot. You won't need anything else. Security for your home or business has never been so easy. Just look at what you get...... . • High quality 4 Sector Control Panel with steel case, key1ock and battery back-up facility. • Two Passive lnfrared Detectors for hall, entrance or room surveillance. • Two magnetic Reed Switches for door or window protection. · External Horn Speaker & Hom Cover with taper protection. • Flashing Strobe Warning light • Panic Button for manual alarm triggering • High pitched internal siren · Back-up Battery and Mains Power Pack • 100 metres of cable • Two Alarm Deterrent stickers • Complete installation Instructions. Cat L-5150 You Get The Lot For Only s599 BUILD YOUR OWN! 1 OOW HF Linear A miniature Stereo FM Transmitter powered by one 1.5V penlite cell. You can connect your CD player to the Mini-Mitter and then listen to your favourite CD's SILICON anywhere in the house, via your CHIP Walkman Personal Portable. Cat K-5004 . o" Ill Cat K-6331 STEREO FM TRANSMITTER This amazing little receiver can be constructed in a matter of hours and gives superb performance. A dual conversion receiver it uses the Motorola MC3362 integrated circuit, is of low-power design with excellent sensitivity, low power drain and good image rejection in narrow band voice and data link applications. Cat K-6000 s59so Specifications: Frequency: All amateur bands from 2-30MHz Output Power: 100W, (CW & AM), 150W PEP (SSB) Input Power: SW max (CW), 10-15W PEP max (SSB) Supply: 13.8V DC 3rd Order IMD: <-0.SdB Very latest IC technology Optical Motion A fantastic idea! Allows 20 second delay before the interior light turns off - enough time to find the keyhole, fasten seat belts, etc. Plus there's a dimmer control for map reading, etc and more! Easy to build, easy to install. Cat K-4002 Designed for the HF Transceiver but also perfect for use with a huge range of QRP commercial gear, in the range of 3 to 15 watts output. Based on 2SC2290 RF power transistors, it gives around 10 to 14dB gain so up to 100W output could be obtained from a very modest input. The circuit is wide band and has only 3dB drop-off at 28 MHz. A switchable low-pass filter is included. Includes carrier-operated Rx/Tx switching. Use as part of an alarm - or as a door minder, etc. A special optical IC actually detects movement by change in light level. Two modes - 'guard' for sensing movement, and 'search' for beam cutting operation. Self contained (battery operated). Cat K-2721 NEW KITS SOON TO BE RELEASED/I! Design your own garden sprinkler system for about half the cost of commercial units! The Sprinkler Timer allows you to control up to 14 sectors (2 x 7) with the aid of any standard Distributor Tap (prototype used SABCO) and only one or two solenoid valves you can have the healthiest garden in the street. Mains powered, the kit comes with case, pre-punched front panel, panel label and all components. Cat K-3588 Small, lightweight, incredibly easy to tune and superb stereo sound! The Wide Band AM Stereo Radio is easy to build and requires no fancy tools or equipment. Comes complete with case, stereo headphones, prepunched front panel and all components. All you do is put it together, add 2 AA batteries and you're away! Cat K-5200 ........,~====7<";1 12V<at> 1.5A Regulated Just right for CB's, car radio/stereo's, small amateur transceivers (hand-helds especially), etc. 12 volts DC regulated with terminals for easy connection . Makes a great service supply, too. Cat M-9545 s79e5 e 3-6-9-12V DC <at>1 Amp 109 1595 12V AC <at> 500mA Ideal power supply for projects that require 12V AC at 500mA. Because the whole of the plug-pack is a transformer, you get a much higher current rating than other plug-packs. Cat M-9555 Cat'M-9526 s13e5 QUALITY CHARGERS llp to 8 batt1ri1s at one,... n s19e5 Save with these quality NiCads. There's one to suit most applications. (180m Ah) (500m Ah) (600m Ah) (1.2 Ah) (2.0 Ah) (1.2 Ah) f4-.0 Ah) (Varta) For all equipment requiring 9V DC at a 9V transistor type battery or many other static hobby models that require 9V. Eliminator modules simply plugs into a 240V AC power socket. An extremely versatile supply ready for Cat M-9514 just about any application. Switchable output gives 6 different voltages ranging from 3V to 12V, at up to 300mA. s29e5 Most battery devices include an external DC connection. Use them in the car from your car battery via this voltage converter. Suitable for high current device, simply plugs into cigar lighter.Cat M-9584 $ Type This battery eliminator is one of the most superb buys in this catalogue many thousands have been purchased by people who know how to save money. It is a small plug-in unit that has three output voltages of 3,6 and 9 volts DC at 200 milliamps - possibly the three most used voltages on battery powered equipment. It is ideal for many battery driven items. Cat M-9525 3-4.5-6-7.5-9-12¥ <at>300mA 6, 7.5 and 9 volts output at BOOmA 'AAA' 'AA' 'AA' 'C' 'C' 'D' 'D' 9 Volt The biggest problem with most projects is fitting in the transformer! This one obviates the problem - keep the supply components inside, but the plug-pack hangs on the power point! With a very healthy 16V at 900mA. It's perfect for 12 volt DC supplies. Energy a.uthoritv approved. , Cat M-95'67 9VDC<at>200mA Invaluable around the home or workshop. It will gives a maximum of 1 amp at 3, 6, 9 and 12 volts DC. Simply plugs into 240V AC power socket - DC connections via screw terminals on front of unit. Ideal for use with alarm systems, intercoms, etc. Cat M-9530 Car Voltag 3-6-9¥ DC <at>200mA s15e5 The high power Panther. With a 3 amp Q continuous (or 4A continuous at 75% duty cycle!) and a huge 8 amp instantaneous peak rating, it's deal for those higher current and higher peak demand applications.Cat M-9547 5 AC Supply 16V 900mA Cat No Price S-3305 S-3300 S-3312 S-3301 S-3311 S-3303 S-3310 S-3308 $3.95 $3.95 $4.95 $9.95 $11.95 $9.95 $14.95 $19.95 Features indicator lights for each cell, reverse polarity protection , mains operation, test meter and more! Cat M-9505 s39e5 ea NiCad Charger Most devices these days allow for an external charger to be plugged in to charge NiCads (usually a 2.5mm socket). This charger is ideal for all NiCad packs from 6 to 10 cells (ie 7.2 to 12 volts). Fully approved by Electricity Authority. Cat M-95'17 s17e5 1'--~1111__, YOU'LL NEED OUR INPUT RS-232 Serial Breakout Box A complete in-line tester/adaptor which makes complex and time consuming Serial connections a breeze. Comes with 25 pin male connector at one end and 25 pin female connector at the other. With jumper pads and wires, as well as 24 in-line swtches, for quick selection for any RS-232 configuration. The tester itself has 8 bi-colour LED's which monitor the lines and tell you at a glance when you've got it right. $ Cat X-2654 4995 3-Way Switch Boxes An easy to use line tester with 25 male and 25 pin female connectors. 18 bright LED's monitor the lines so you'll know immediately where the problem lies. A great time and headache saver! s995 RS-232 Quick Tester Just like the male gender changer above, except this one has DE9 female connector; on ;~eh end. ~ 9 :'.::,oo. •9"5 A 11,'I, 25 Pin Male Gender Changer RS-232 9 Pin to 25 Pin Adaptor Changes the gender on any 25 pin plug from female to male. D825 male connectors at each end. Wired pin for In line adaptor with DE9 female connector one end and D825 male at the other. :;:,,sas "995 RS-232 Serial Jumper Box 25 pin male and 25 pin female connectors. With jumper pads and wires which allow permanent soldering for RS-232 connections. Cat X-3569 CO Cat X-2660 s9 ~ RS-232 Null Modem Adaptor Changes the configuration of any 25 pin male connector to 25 female. D825 female connectors at each end. Wired pin for pin. With D825 connectors at each end. Wired for full handshaking. Allows the connection of two computers 'back to s995 s9 95 Monitor Extension Cable 5 :::,oo, sg 95 ~: • . :~ • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • CampbeHtown (046)27 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Liverpool 600 9888 • Maiaand 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Rail.way Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Warringah MaH 905 0441 • Wollongong 28 3800 • ACT • Fyshwick 80 4944 • VIC • BaHarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg (03) 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 1614 • Ringwood 879 5338 • Springvale 547 0522 •OLD• Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Tocwoomba 38 4300 • Town1ville 72 5722 • Underwood 341 0844 •SA• Adelaide City 232 1200 • Beverley 347 1900 • St Marya 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 • WA• Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • Midland 250 1460 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 25 Pin M/F Serial Cable Cable fitted with 25 female and 25 pin Male 'D' conn ectors on either end. All lines connected straight through. s2495 Cat X-3564 1295 ~ - ::- ~ ~ 9 Pin(F) - 25 Pin(M) Serial Cable Ideal for modem connection to 9 Pin Serial port. Fitted with DE9 female connector one end and D825 male connector at the other. Cat X-8007 s2495 Centronics Printer Cable A standard printer cable with DB 25 pin male connector and 36 pin Centronics plug. Suits Atari and all computers that support a PC compatible type parallel port. /',f, Cat X-8614 s249s 11 _n,__ 95 25 Pin Female Gender Changer Cat X-3566 3995 RS-232 25 Pin to 9 Pin Adaptor A line adaptor with D825 pin female connector one end and DE9 male at the • . An in-line tester which has both 25 male and 25 pin female connectors. Three switches and 6 LED's allow quick selection for the most popular RS-232 configurations. You simply set the switch to select the connection you need. Cat X-2602 Cat X-2656 5 A 2 metre extension cable with 9 pin 'D' connectors that allows you to distance monitor and CPU. ~ 1/ 9 Pin Female Gender Changer . . 95 19 l n~~~,i;~.;.:::.:.~=r::::.;:::--- - nrmm~m Cat X-2650 Cat X-2652 $ A great idea! The switch box : , allows the switching of a 1/, 1/, common input or output to any one of three other devices. All lines are switched. Ideal to, sha<ing a printer or modem with more than one computer or connecting several printers 9 Pin Male Gender to one Centronics port. Changer 25 Pin With DB25 Connectors An in-line gender changer which has Cat X-3575 DE9 male connectors at each end. Changes the gender of a plug or 36 Pin With Centronics connector from female to male. Connectors. Cat X-3576 Cat X-2657 RS-232 Serial 9 Line Tester ;----, ••• Cl Disk Drive Power Splitter Cable A great idea! This "Y" adaptor allows you to connect two disk drives to one power connector. Splits a 4-line Molex male into two females. !;5 $695 CatX-2604 25 Pin M/M Serial Cable i' • ~ Floppy IDC Universal Data Cable FOR THE MAXIMUM OUTPUT VGA Multi-Scanning Colour Monitor Analogue or TTL! A superb monitor from ACER! Performs beautifully as a high resolution full colour monitor or for easy to read text and graphics in green, amber or white on blue when connected to Hercules (mono) cards. With 14" screen and built-in pan tilt base so positioning is a breeze. Compatible with all video standards including MDA, MGA, Hercules, CGA, EGA, VGA, PGC and MCGA. Comes complete with 9 Pin cable and 15 Pin analogue cable for VGA and most other cards. AceR Features include .31 mm dot pitch, The Word for Value non-glare etched screen and high resolution -800 dots x 600 lines. Once you've seen this in action you'll want to ~r:~~~;u;;;, sa 99 IT'S NEIN! Super VGA Graphics Adaptor! You won't believe your eyes! More colours, higher resolution and more options are just some of the outstanding features of the Super VGA A New Look For All Your Software! With Drivers! AutoCAD, games, text, paint programs, graphics, charts, desktop publishing , business software .... .astonishing clarity and versatility at the touch of a button. Comes complete with drivers for Lotus (release 2), AutoCAD (Versions 2.18) , GEM , Word Perfect (Version 4.2), Framework II (release 1.1), Wordstar (release 3 & 4) , Ventura (Versions 1 & 2) and MS Windows (Version 2). You 'll get a total ly new perspective on all your computer work with the sensational Super VGA Graphics Adaptor. And it costs much less than anything that's comparable! Powerful! The VGA Graphics Adaptor fits into any IBM compatible (XT or AT) and comes with 256K RAM on board . And that's easily expandable to 512K for even more amazing colour and graphics capabilities. VGA Graphics Adaptor 8 Bit Version. Selectable Resolution The VGA is supplied with utilities which allow emulation of EGA, Hercules and CGA with boot disk option. All standard IBM VGA modes are supported plus, 640 x 400 (256 colours) and 800 X 600 (16 colours). With full expansion (512K) selectable resolution modes are 132 x 60 (text), 640 x 480 and an incredible 1024 x 768. In fact, there are so many graphics modes available there's just no room to list them all here! The inexpensive way to add superb graphics on your IBM compatible. Fitted with 256K (expandable to 512K) Cat X-2018 VGA Graphics Adaptor 16 Bit Version Faster graphics/ text update on screen for 286 / 386 machines. Cat X-2019 COMPUTERS 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. LED1 I S1 100k 10k IC1 555 1000, + 16VW _ IC2 555 I T ..,_ 9·12V: .0047 Siren & flash generator for toy cars This circuit was built to replace the module in a Matchbox police car. When the batteries in these modules go flat they cannot be replaced. Transistors Ql and QZ are connected together as a simple multivibrator with two parallel- ed LEDs being driven by Ql. 555 timers ICl and IC2 then provide the siren function with the slow waveform of ICl frequency modulating the fast waveform of IC2. Both timers are connected identically, with the capacitor at pins 2 & 6 being charged via a lOOkQ resistor from the output at pin 3. This arrangement gives an almost ideal square wave (ie, with a duty cycle of 1:1) without r-------------, Balanced outputs from a single supply Have you ever wanted to add an extra piece of circuitry to an existing system only to be thwarted by the fact your new gizmo requires a balanced supply and you only have a single rail supply? Several options are available, such as rearranging the existing supply or adding another transformer. Neither is ideal, especially when the negative rail is only required to supply a few tens of milliamps to feed that new preamp or whatever. This circuit was added to an existing regulated supply to provide a negative regulated voltage. It takes up little space and requires no alteration to the existing supply components. The existing supply using a 7812 12V regulator is shown within the dotted lines. The add on negative rail consists of a voltage doubler using diodes Dl-D4, capacitors Cl-C4 74 SILICON CHIP the circuit complications necessary with the conventional connection of a 555 timer. ICl 's output is connected via a 1OkQ resistor to the pin 5 modulation input of IC2 to provide a siren tone which rises and falls at a slow rate. IC2 drives a BD140 transistor directly to provide audio output from an 80 loudspeaker. S. Thorley, Townsville, Qld ($20) ..------------. I I ,___ _I o+12V I + I - I I I -----------......,.,oov 1 L _____ _ The add on negative rail consists of a voltage doubler based on diodes D1-D4, capacitors C1-C4 and a 7912 - 12V regulator. The circuit operates by alternately using Cl & C2 to charge C3. and a 7912 - 12V regulator IC. The circuit operates by using capacitors Cl and C2 to alternately charge capacitor C3 as follows. Capacitor Cl charges through Dl when the voltage at point A is positive relative to point B. During the next half-cycle, point A swings negative and therefore the negative end of Cl swings even further negative so that C3 is charged via DZ. During the next half cycle, when point B again swings negative with respect to point A, C2 will be charged via D3 . Then, in the following half-cycle, the negative end of C2 will be pushed even further negative to charge C3 via D4. The voltage developed across C3 is then fed to the 7912 regulator to provide a precise - 12V output. G. Small, Greystanes, NSW. ($25) .--------------------------------....o~v S13 01 BC547 10k 16 012t-.a1--t-N-l,---O VR1 1M 01 1 010 TO CAMERA MOTOR SOCKET 15 [F 14 09 12 2.2M 4~~\ 08 07 06 IC1 150k 555 05 _ ___,.2 04 03 02 S14b o§fCDNDS .J: .,. 3.3 16VWI Timer for motor driven cameras Here's an economical timer circuit that can be used to fire a motor-driven camera at preset intervals. It's just the shot for time lapse photography and can count any number from 1 to 4095, either in seconds or in minutes. The circuit uses only a few low-cost parts. ICl is a 555 timer that delivers a brief low-going pulse at its pin 3 output at one second or one minute intervals, depending on the position of S14. These pulses clock IC2 which is a 4040 12-stage binary counter. IC2's Q1-Q12 outputs are fed to DIP switches S 1-S 12 via isolating diodes D1-D12. When the outputs that connect to closed switches all go high, the output line also goes high due to the 10k0 pullup resistor. This then turns on Ql which activates the reed relay and fires the camera (ie, when the reed relay contacts are shorted). At the same time, the O.lµF capacitor on pin 11 of IC2 charges via the lMO resistor. After about O. ls, pin 11 goes high, IC2 resets and the timing cycle starts again. The O. ls delay is necessary to ensure that the output line has sufficient time to fire the camera via Ql. 4 2 D1- 12 1N 14 REED RELAY S1· 12 DIP SWITCHES 3 5 6 7 9 011"'--+-N--I--O RESET .,. 11 1M Trimpots VRl & VR2 allow the circuit to be calibrated to one second and one minute time intervals. Note that the 22µF and 3.3µF capacitors should be low leakage (LL) types. Finally, Table 1 shows the time intervals (in seconds or minutes) for various DIP switch settings. If more than one switch is closed at any one time, the time interval can be found simply by adding the individual values together. For example, if S5 and S7 are closed, the time interval becomes 16 + 64 = 80 (seconds or minutes). R. Beinke, Quorn, SA. ($25) II DIP Switch Time Interval S1 S2 S3 S4 S5 S6 S7 S8 S9 S 10 S 11 S12 2 4 8 16 32 64 128 256 512 1024 2048 1 Table 1: the time intervals for various DIP switch settings. If more than one switch is closed, the times are added. The DIP switches are mounted on the lid of the case to allow for easy alteration. A label on the side of the case shows the corresponding time intervals. OCT0BER1989 75 COMPUTER BITS By JENNIFER BONNITCHA Setting up your hard disc Enough is enough. The time has come! For what seems the hundredth time, you swap your program and data discs to continue working. While waiting for the files to load from disc, you ponder the possibility of finally taking the plunge and buying a hard disc. Alternatively, you could be a victim of the dreaded "1701 Error No Boot Device Available" - your whole life flashes before you as, with growing dread, you search for the last set of backup discs. The PC hard disc is a typical "black box" where a light blinks when you put data in and when you get it out again. As noted last month, hard discs store much larger amounts of data and access it faster than floppy discs. They have been available for about as long as the PC has been around. However, it wasn't until the introduction of the XT computer from IBM that the hard disc was offered as a feature. Increased storage capacity and a considerable reduction in the time required to read or write data means that the hard disc has become almost essential for even This DC-2200 hard disc controller card from Electronic Solutions will work with older IBM PC/XTs or compatibles, as well as with the newer turbo XT machines. It is installed in a vacant expansion slot on the motherboard. 76 SILICON CHIP the generally conservative computer user. And now you have decided to join that group. However, before you can utilize all those megabytes, you need to install the hard disc - and that can be a daunting experience for many users. Finally all those megabytes are at your fingertips and the moment has arrived to tackle the installation. Make sure you have plenty of time to spare so you don't have to rush through the procedure. A good start is to turn the radio or stereo on, select a soothing tune, then begin. Opening the case Have close at hand an assortment of screwdrivers, your computer's reference manual and the new hard disc. Disconnect the keyboard and ensure the system power unit switch is off. Disconnect the power cord from the wall outlet for added security. Now either place the system unit on a suitable table or turn it around to allow easy access to the rear cover mounting screws (generally anything from two to five screws), and arm yourself with the appropriate screwdriver. Fig.1 shows the locations of the cover mounting screws for an IBM-style case. Remove the screws, set them aside, then slide the system unit cover from the rear and toward the front as illustrated in Fig.2. Finally, when the cover will move no further forward, tilt it at a 15° angle and remove it from the base as shown in Fig.3. So far , so good. Set the cover to one side with the cover mounting screws and examine the inside of the system unit. The power supply amount of memory or the presence of a maths co-processor - are installed or connected to the PC. Fig.1: here are the locations of the cover screws for an IBMstyle case. Hard disc controller Fig.2: remove the screws, then slide the cover forwards as far as it will go. 1/ Fig.3: the cover is removed from the base by tilting it upwards at a 15° angle. in an XT is located in the same posi- tion as the PC power supply at the top right of the system unit. The lower left section of the XT contains sockets for memory chip installation, while a single configuration switch containing eight DIP (Dual In-line Package) switches is located below and to the right of the system expansion slots (the PC has two 8-position switches). These switches, shown in Figs.4 and 5, define which options - such as the number of disc drives, the The hard disc itself is just a recording device so a hard disc controller (in conjunction with the operating system) is required to determine what the disc actually receives, how fast and where it will be placed. The hard disc controller handles a multitude of tasks: formatting the disc for later use, encoding the data it receives from DOS, instructing the hard disc where to place the read/write heads, writing, reading and verifying the data, correcting errors and reporting back to DOS with the data and status concerning success or failure. Install the controller card in one of the vacant expansion slots (it doesn't matter which one) and connect the signal and power cables. Mount the hard disc as required in your system unit, then connect the cables. Once all the options are installed in the system unit, make sure the appropriate DIP switches are set to reflect the current state of your computer. Caution here! The functions of the DIP switches shown in Fig.4 are for one model of the IBM PC and there are differences between models. You should read your computer's reference manual very carefully to ascertain the correct settings of the DIP switches for your machine. Make sure you note the position of all DIP switches before you begin. Fig.5 shows the DIP switch settings for the PC XT. You may find your compatible does not have as many switches. Before leaving the factory, the hard disc is erased so that it contains no information at all. The disc manufacturer has no way of knowing what type of disc controller will be used with the disc and while the connector that attaches the drive to the controller is standard, the way controllers encode data isn't. Low level format Once the disc is installed, it is a good idea to perform a system checkout using your computer's Diagnostic Diskette. This disc also OCT0BER1989 77 Switch 2 Switch l 2 01 3 4 5 6 7 8 ~□~□□□□□□ Position 1 7-8 2 34 5-6 Function SYSTEM BOARD Switch I l6Kl310 32KB 48KB 6 41 <0 Switch 2 □□ □ 00001 I □ □□□ 00001 l□□□□ oo□□ l l□□□□oo□ol I□ on 00000 I l□□□□ooo □I I□ LIU □DODD 11 □ □a □ ODO DI MEMORY OPTIONS 96 KB Position 100□□ 00001 1 □□□□00001 l□□□□□o □□ I l □□□□boo □I I6 100□□ 000011 □□□□ 00001 196KB 1□ 0 □□00001 1□□□□00 □□1 228 100□□ 00001 1 □□□□ 00001 Amount of memory options installed Always in the off position Number of 5-1/4" diskette drives installed Switch I Switch 2 0-Drives l □ oooo□a□ I l□ aooo□ oo I I-Drive 1000000□□ 1100000000 I 2-Drives l□□oooo□□ l l□□ooooo□ I Monitor type Switch I No monitors 128KB 40 x 25 Color 0KB 80 x 25 Color I Switch 2 I00000000 IOOOOOOOO I IO000 □□ 00 IIO0000000 I I0000 □□ 00110 00000 00 I Note: The 80 x 25 color setting. when used with home television and various monitors can cause loss of character/quality. 10000□□001 l □□oomrn□ I KB 256l~Bl□ ouuououl l □□□ auo □□I Function 1-2-3-4 5-6- 7-8 Number of 5¼-inch diskette drives installed Reserved for co-processor Amount of RAM on system board Type of monitor you are using IBM Monochrome Display or more than one monitor Fig.4: this diagram shows how the DIP switches are set to select the memory, drive & monitor options for one particular model IBM PC. Check the manual for your particular machine carefully as there are differences between models. Note that Switch 1 selects the number of floppy disc drives only. contains the low-level format information. For many computer users, the low-level format is never seen as the dealer takes care of this basic but very important step. However, it is a very important process which can affect future performance. The low-level format is performed using the manufacturer's disc diagnostics, or a program built into the disc controller and accessed generally through the DOS command Debug. 78 SILICON CHIP Your computer is capable of running UNIX, XENIX, PICK, CP/M-86 or OS/2. All it needs is an entry to the MBR (Master Boot Record) indicating where the operating system begins on the disc, how much space it takes, whether it is currently active and a unique character for future identification. The format program instructs the controller to format the disc one surface at a time, dividing up each side of each platter into concentric rings, or tracks, and breaking each ring into manageable pieces (sectors). Each sector begins with a distinctive data pattern to help the disc controller determine the sector's start position. Most hard discs are formatted with 17 sectors per track and each sector contains 512 bytes of information. The newer IBM PS/2 series computers support larger sectors, commonly as many as 37 per track. The controller level format performs two other functions. First, it sets the interleave (the sequence in which sectors on a hard disc are organised). Second, every sector on the disc is tested for its ability to record and store data. Sectors which fail this test will give errors and can be locked out by the controller to ensure that DOS never tries to store data in that sector. FDISK Once all sides of all platters are formatted and the bad track information entered, the disc is ready for the FDISK program which creates the Master Boot Record (MBR) on track 0, head 0. Boot your computer from Drive A using your DOS disc. When you use FDISK, it is a good idea to view the partition information before you go any further to see the current status of the disc. Type FDISK then press (Enter) to display the main menu of the FDISK program. The options include: (1). Create DOS Partition (2). Change Active Partition (3). Delete DOS Partition (4). Display Partition Data If you had installed two hard discs, a fifth choice permitting you to select the next hard disc drive would display. Select Option 1 so you can create Switch I 2 3 4 5 6 7 Fig.5: XT machines have a single configuration switch located below and to the right of the system expansion slots. Positions 7 & 8 select the number of floppy disc drives installed. 8 of~~ □□□□□□ Position 2 3-4 5-6 7-8 Function For normal operation is off Co-processor Amount of r~AM on system board lype of monitor you are using Number of 5¼-inch diskette drives installed Memory options 128K 192 K 2551 \ l □□□ UUUUUI Ioo□ uoouo I Without co-processor 1 Drive IDDOOO ODQI 2 Drives IOaOLI OOu□ I Monitor type Co -processor With co-processor Root directory Number of 5¼-inch diskette drives installed I□ a□□ oooo I IO OOOOOOI IO~ 0000 OI O LJ No display 1 □ 000000 □1 IBM Coler Display or other color display in the 40 x 25 Coler mode 1 0000 □□0~1 IBM Color Display or other color display in the 80 x 25 Color mode 1000 □□□0 □1 I_ODO O□ noW n1LI _ IBM Monochrome Display or more than one display a DOS partition and decide how to split your disc. Note that you can have partitions other than DOS on the disc (when running UNIX for example) and that DOS won't touch the MBR entries for these other systems. Decide whether or not you want to use the entire hard disc for DOS and continue. Note that some versions of FDISK don't automatically activate the partition so you may need to choose Option 2. Review the partition data before you exit FDISK. Using FORMAT Once the DOS partition is created and activated, you must format the disc as final preparation for use. To do this, you use the familiar DOS program FORMAT. This program makes the DOS partition usable by establishing the DOS Boot Sector, a File Allocation Table disc to show what area the file occupies on the disc and where the next piece of data, if applicable, can be found. The FAT functions in much the same way as the table of contents in a book. DOS generally maintains two copies of the FAT so that if one is damaged, it can use the other. However, it can't decide which is correct if there is a conflict. (FAT) and an empty Root Directory. The DOS Boot Sector is what the Master Boot Record helps point the computer to when you turn on the power or perform a system reset. It is actually a small program containing some important pieces of data specific to DOS such as how big the boot sector is, how many FATs and their size, the size of data clusters, the size of the root directory and what the system files are called. Disc structure Without a valid DOS Boot Sector, the computer usually freezes or may boot straight to BASIC (on IBM PCs which have BASIC in ROM). Right after the Boot Sector comes the first copy of the File Allocation Table (FAT). The FAT has one entry for every place on the disc where data can be stored. The table is updated each time a file is written to Finally, after the second copy of the FAT comes the Root Directory which is the main directory from which all others branch. Unlike other directories, it is fixed in length and typically contains a maximum of 512 entries (although larger discs may hold 1024 entries). Following the root directory, data storage commences and extends to the end of the partition. Typical Format options include: FORMAT C :/S/V the /S parameter causes the transfer of system files like IQ.SYS, DOS.SYS and COMMAND.COM from the DOS disc to the hard disc. The two SYS files are hidden from view to prevent accidental erasure and are only reported when the CHKDSK program is run. Using DOS version 3.X, the program issues a warning before it commences formatting the hard disc . Previous versions simply issued the standard message and commenced formatting immediately. Since you want to format the new DOS partition, you would respond in the affirmative. After several minutes, the messages "Format Complete" and "System Transferred" will be displayed because you included the /S option. Next you will be asked to enter a label for the disc. This label is optional and has no real significance for the computer's operation. A new life Once you have partitioned and formatted your hard disc you are ready to copy DOS to the DOS directory on Drive C and begin a whole new life as a computer user. The system will now automatically recognise that your computer has a hard disc and you can now boot programs directly from it. ~ OCT0BER1989 79 t:\ YLAH JAYCAH JAY LAM JA fl..AM JATU\11 JAYlJ\H JAYU\H JAYlAH JAYU\H JAYt.;AH JA YCAH JAYCAH JAYU\H JAYCAH JAYU\11 JA YLAH JAYCA.11 JA Tl.Al1 JATLAM JATl...'1in JA Tl.An .JATLAn JA TI..An JA TI..An JI-\ Tl.1-m JA Tl.1-\n JI-\ J\..,1-\n JI-\ TI.A n JM J\..,1-\ n JI-\ TL.i ~YCAH JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYCAR JAye, AYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYC, AYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYC, i\YCARJAYCAA I AVl"•o 1• vl"11.o 1, v,..A Q , ., ._,,.. ,. ., , • .,,. ,. n ,..,,,, • ., I AV,.. • n •• vr-. 11. n •• " ""!1 •" "" " ., •11vl" .• ~ 11>v,-,1 0 111vr , o • Av,.11.n _uvr,1n 1-'.Vf'AO 1-'. V f' <\.'l lo\Vf'AD !A.Vf'/ID IAVf'/\0 l,l~Vf'Aq 1/.Vf'IIQ: l~Vf''i.ll I.A Vf' ~ D l i\¥rh-.A l liW'AQ: I AVf',1',~~~ AYCAR JAYCAR JAYCAA 4YCAH JAYCAR JAYCAA 4YCAR JAYCAR JAYCAA 4YCARJAYCAR JAYCAR AYCAR JAYCAR ' JAYCAR ~YCAR JAYCAR JAYCAR AYCARJAYCAR JAYCAR ~YCARJAYCAR JAYCAR AYCAR JAYCAR Ref. Silicon Chip Feb '89 JAYCAA Each transformer has 26.5 - 0 ~ YCAR JAYCAR JAYCAR 26.5 (ie 53 V CT) secondary. This is a co-operative speaker project between Silicon Chip AYCAR JAYCAR JAYCAR Fully compatible with IBM PC/XT. Metal case. Provides and Jaycar. Using an 8' woofer and a dome tweeter with You could use two of these for ~YCAR JAYCAR JAYCAR +3V / 13A, .5V / 1A, +12V / 3A &-12V / 1A from 240V input. pre-built crossover unit the system has been acclaimed for WCARJAYCAR a power supply for 300 W + JAYCAR Cat. XC-5080 ~YCAR JAYCAR its superb sound reproduction. The cabinets measure 40C(H) RMS amp. Also has 13.6 V CT JAYCAR ~YCARJAYCAR x 300{W) x 290(D)mm. For further information see our 1989 secondary as well. JAYCAR WCARJAYCAR catalogue. JAYCAR Transformer weighs a massive WCARJAYCAR JAYCAR Pair of speakers and crossovers 7.5 kg so add an extra $8 to ~YCAR JAYCAR JAYCAR normal P& P rates. ~YCAR JAYCAR Cat. CS-2540 JAYCAR Cat. MM-2022 WCARJAYCAR Cabinets (pair) JAYCAR ~ YCAR JAYCAR JAYCAR Cat CS-2542 ~ YCAR JAYCAR JAYC,AR WCARJAYCAR JAYCAR AYCAR JAYCAR JAYCAR ~YCARJAYCAR .JAYCAR ~ YCAR JAYCAR JAYCAR AYCAR JAYCAR JAYCAR AYCAR JAYCAR JAYCAR ~YCAR JAYCAR JAYCAR 4YCAR JAYCAR JAYCAR ~YCAR JAYCAR JAYCAR ~ YCAR JAYCAR JAYCAR 4YCAR JAYCAR JAYCAR 4YCAR JAYCAR JAYCAR 4YCARJAYCAR JAYCAR 4YCAR JAYCAR JAYCAR 4YCAR JAYCAR JAYC,AR 4YCARJAYCAR JAYCAR 4YCARJAYCAR JAYCAR 4YCAR JAYCAR JAYCAR AYG.4R JAYG.4R JAYCAR AYCAR JAYCAR JAYCAR AYCARJAYCAR JAYCAR AYCAR JAYCAR JAYCAR AYCAR JAYCAR Ideal for car alarms. JAYCAR AYCAR JAYCAR JAYCAR This unit measuring 63 x 43 AYCAR JAYCAR JAYCAR x 30 has a piezo element in it AYCAR JAYCAR JAYCAR which has a weight attached AYCAR JAYCAR JAYCAR AYCAR JAYCAR to one end. Any movement JAYCAR AYCAR JAYCAR causes the piezo to flex and JAYCAR AYCAR JAYCAR generate a voltage. The JAYCAR AYCAR JAYCAR JAYCAR 10+ $13.95 voltage is then processed AYCAR JAYCAR JAYCAR Cat SB-2482 through a circuit. The end AYCAR JAYCAR JAYCAR result is a detector that is AYCARJAYCAR JAYCAR AYCAR JAYCAR capable of triggering out as 10+ $18.95 JAYCAR AYCAR JAYCAR little as a hand clap nearby to not noticing a heafty jolt. You can Cat. SB-2484 JAYCAR AYCAR JAYCAR adjust it anywhere in between. JAYCAR AYCAR JAYCAR The module is simple to connect using only 3 wires. two for JAYCAR 10+ $75.00 AYCAR JAYCAR JAYCAR power and one which will trigger an alarm. Comes complete AYCAR JAYCAR Cat. SB-2490 JAYCAR with mounting screws and double sided mounting tape. AYCAR JAYCAR JAYCAR I - - - - - - - - - - -AYCAR JAYCAR JAYCAR AYCAR JAYCAR Cat. LA-5062 JAYCAR AYCAR JAYCAR JAYCAR AYCAR JAYCAR JAYCAR AYCARJAYCAR 111• 1!iHU!ltl fllH ~~( nMI IN Al 10tl JAYCAR f1f:1'0lT Tf U Hf.RY AYCARJAYCAR JAYCAR AYCAR JAYCAR JAYCAR Another surplus deal. Japanese SATO brand knobs in different AYCAR JAYCAR JAYCAR types all imperial. Also quantity of Rean knobs with different AYCAR JAYCAR JAYCAR AYCAR JAYCAR coloured caps these are metric. Pack includes minimum 50 knobs. JAYCAR AYCAR JAYCAR generally more - majority Rean. We figure about $60 worth of JAYCAR AYCAR JAYCAR knobs. Another Jaycar direct import. Would you believe - computer (on goods of the JAYCAR AYCAR JAYCAR JAYCAP Cat HK-7050 disks with a LIFETIME GUARANTEE for less money than you same quality) AYCAR JAYCAR JAYCAR have ever had to pay before. AYCAR JAYCAR JAYCAR 51/4" DSDD 48TPI DOUBLE SIDED/DOUBlf AYCAR JAYCAR JAYCAR DENSITY Cat. 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AYCAR JAYCAR JAYCAR Normal price would be about $25 AYCAR JAYCAR JAYCAR AYCAR JAYCAR We can offer these at an absolute bargain basement price of JAYCAR AYCAR JAYCAR JAYCAR AYCARJAYCAR JAYCAR 5 + $12 each Cat. 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Do you worry about the SWR (standing wave ratio) of the antenna system for amateur or CB radio transmitters? Maybe you have nothing to worry about. After all, what is really important is just how efficiently the antenna radiates your signal. MODEL 111 One of the most common misconceptions held by communications enthusiasts and amateur operators alike is the importance above all else of antenna SWR. Most operators agree that a standing wave ratio of 1:1 is the ultimate goal when it comes to antenna performance but is it real1y? A resistive dummy load presents that ideal ratio but it is lousy as a radiator of RF power. To understand the importance (or unimportance) of SWR, one needs to think back to some basic antenna theory. Without going into the complicated mathematical analysis, a few facts can be stated. Firstly, the load for any transmission line, be it open wire feeder or coaxial cable, can be any device capable of dissipating RF energy. This load is the only factor that determines the standing wave ratio which exists on the line. If, in the case of a line having a characteristic impedance of 500, the load is a 500 resistor, there will be no standing waves. If the load is not equal to the characteristic impedance of the line, then there will be standing waves. Secondly, there is nothing that can be done at the transmitter end of a feed line to change the SWR which exists on any particular transmission line. This includes making the transmission line longer or shorter! Standing waves Basically, standing waves are the distribution of voltage and current along the transmission line, and the subsequent interference pattern formed by the superposition of the forward and reflected waves. Under normal conditions we refer to VSWR, or voltage standing wave ratio, simply because it is easier to make a probe that samples the electric field in the line than it is to make a shielded loop that samples the magnetic field. In any case, the voltage and current distributions have exactly the same shape. They vary only in position, as the voltage and current standing Fig.1: the voltage and current standing waves in a transmission cable are displaced relative to each other by a quarter wavelength. V 84 SILICON CHIP I This handy instrument from Dick Smith Electronics can measure SWR, RF power & field strength. It is installed in series with the antenna feedline. waves are displaced relative to each other by a quarter wavelength (see Fig.1). If the VSWR is to be made as low as possible, it is essential that the load, at the point of connection to the transmission line, be made as close to a purely resistive value as possible. This means that the load must be resonant at the operating frequency. From basic theory, we know that the nominal impedance of a half wave dipole is in the vicinity of 700 or so. We also know that a folded dipole has an impedance of four times that value (ie, 2800), so it is relatively easy to use a suitable feed system having a similar characteristic impedance. At VHF and UHF, things get a bit more difficult, in that theory says that the characteristic impedance of a quarter wave groundplane is around 200, which is quite a poor match if using (as most amateurs do) 500 coaxial cable. However, we also know that a quarter wave ground plane antenna has quite useable gain and can provide quite reasonable results due to its relatively low angle of radiation. So while the antenna presents a poor match to 500 cable, it has quite good performance as a radiator. Theory says that we should try to match the antenna impedance to the line impedance, thus eliminating standing waves. This could be done by using a quarter wave transformer or a matching circuit using inductors and capacitors. However the practicality and the necessity to go to this trouble can readily be overlooked, once we understand more about the consequences of a less than ideal SWR. In practice, most transmitter output stages are designed to have a very low source impedance. This is done to minimise the amount of energy dissipated in the output stage itself. Inevitably, this means that there is quite a mismatch at the transmitter end of the transmission line, causing reflected "waves" of RF energy. Many amateurs are under the misapprehension that this energy is lost, wasted by heating the feedline. In fact, energy which is reflected back down the transmission line by an ante.nna mismatch is rereflected by the transmitter output stage/feedline mismatch and reappears at the antenna where it is radiated. So in practice, as long as the transmitter is stable and not likely to be damaged or subject to overheating due to line mismatch, the effect of a high VSWR will have no affect on the radiated power of the antenna system. In fact, the only affect that should be taken into account is the propagation delay between the initial wavefront and subsequent reflected waves. In particular, amateur television operators do need to pay attention to antenna and feedline characteristics and construction to avoid the transmission of multiple images or ghosts. Measuring VSWR When it comes to measuring VSWR, the most accurate method is to measure both the forward and reflected transmitter power with an insertion type wattmeter and calculate the VSWR from Fig.2a & Fig.2b. Precisely where the watt- "' 1· 0 1- 5 2-0 3 -0 4 -0 5 ·0 100 10 15 20 2 530 4 0 50 Fo rward po wer (Wa t ts } (a ) 15 0 200 300 4 00 500 Fig.2a: this graph plots the VSWR for measured reverse powers between .01 W and 1W. A less than ideal VSWR is generally of little consequence. 20 1B 16 14 12 I 10 B 6 4 __ / / ,'; .,...._ ; V / I/ i, i, /lf'/I'/ / ~ ; "' ./ / I/ I/ ,,, I, : ' ' 'i ! I 1· 0 1·5 2·0 3·0 4 -0 5 ·0 10 15 20 2 5 30 40 50 100 150 200 3 004 00 500 For ward p o w er (Watt s) Fig.2b: this graph can be used for reverse powers up to 20W. The VSWR indicates whether the transmitter is being presented with a satisfactory load. meter should be placed is another point on which there are several theories. Suffice to say, the most convenient place to measure forward and reflected power is at the transmitter, even though it can be argued that cable losses will cause the reflected power to be indicated at a level lower than actually present. The most accurate results will be obtained by measuring the ratio using the shortest possible feedline, even if this involves moving the transmitter close to the antenna during the antenna set-up. So VSWR is really an indication as to whether or not the transmitter is being presented with a satisfactory load. While this is an important consideration, it has no bearing upon the performance of the antenna system. Further reading (1). VHF/UHF Manual; G.R. Jessop; published by the RSGB. (2). The ARRL Handbook; published by the ARRL. (3). Handbook of Coaxial Microwave Measurements; published by General Radio. OCT0BER1989 85 THE WAY I SEE IT By NEVILLE WILLIAMS Today they're tagging animals tomorrow, it might be humans! Electronic implants are becoming more common. Now there is an electronic implant system which makes it possible to identify individual animals, with virtually 100% accuracy. The idea is intriguing until you realise that similar technology might be all too easily applicable to humans. So that you'll have some idea of what I'm on about, I suggest that you read the letter in the accompanying panel. The article referred to in the reader's letter appears on pages 73/74 of "Farm" magazine for June 1989, being featured in a segment headed - significantly - "Farm Computer News". Described in the article as a "microchip transponder" the identification device is permanently sealed inside a tiny, biologically inert glass capsule about 12mm long and a couple of millimetres in diameter. A half-dozen of them, each weighing about 54 milligrams, could be laid side-by-side within the area of a 5-cent coin, The capsule is normally implanted in a position clear of potentially edible flesh, using a springloaded 12-gauge syringe. A retractable needle and an in-built depth limiter allows the capsule to be implanted at a depth of 13-32mm, depending on the animal and implant area. Each tiny transponder is preprogrammed with a distinctive number - one of the 34 billion said to be available with the particular coding. The number can be checked and displayed with a portable scan86 SILICON CHIP ner both before and after implant and recorded in a computer data bank, along with other relevant information about the animal. The reading range is about 75mm. Should an animal need to be identified, the implant can be read at any time with a suitable scanner. The new "Destron Electronic Identification" system is said to enjoy the enthusiastic support of the RSPCA and other animal welfare groups and is being evaluated by a number of other organisations concerned with the positive identification of livestock. It is being offered here and in New Zealand through AGTEC AustraHa Pty Ltd, based in Adel- THE AGTEC MICROCHIP transponder is only about 12mm long and 2mm in diameter. It is programmed with one of 34 billion different codes. aide (phone 08 388 8344). According to AGTEC, the system can provide positive identification of individual animals, a big advance on conventional branding. As well, an implant is less disfiguring than either fire or freeze branding and not as vulnerable to loss, damage or interference as external tags. AGTEC uses the equipment to monitor its own breeding herds. At any one time, there may be more than 1000 cows implanted with expensive imported embryos, so there can be no room for mistakes with animal identification. If universally adopted, according to AGTEC, The Destron Electronic Identification system would effectively eliminate the substitution racket in the racing industry and greatly reduce cattle rustling. The wider picture "Im sure you will have heard about the system", says our correspondent P.D. Well, yes and no! I vaguely recall having seen something about it in a TV program but at the time, I had no opportunity to seek out the technical details. Logically, subminiature implants had to be more "humane" than fire branding and I simply assumed that such a system would involve yet another application of the now ubiquitous bar code. One way and another, scientists and research workers have been electronically tagging animals for years to learn more a bout their movements and behaviour. Right now, for example, an Australian team is monitoring penguins in the A pain in the posterior! Dear sir, I'm sure that you will have heard about the electronic identification system described in the attached clipping from a recent issue of "Farm" magazine. I first did so when it was in the final s tages of development and, at the time, regarded it simply as yet another marvel of electronics. Now it is a fact , I see implications of another kind, rais ing questions that need to be asked and answered. Today, it is being used on animals. After it passes that test, could it become the next s tep up from present impositions like tax fil e number, credit card Antarctic, in an effort to gain a better understanding of the food chain. Prompted by P.D.'s letter, however, I began asking specific questions, which brought me into contact firstly with the NSW Department of Agriculture and later with the University of New England, at Armidale, NSW. Based at the university, I learned, are two specialist research groups more or less unique in Australia: the AGBU [Animal Genetic & Breeding Unit) headed up by Dr Keith Hammond, and the University Centre of Electronics in Agriculture, headed by Dr Royden Lake. Dr Hammond kindly offered me a copy of his own recent paper entitled "Electronic Identification of Animals and Automatic Cattle Handling". He also referred me to AMLRDC in Sydney - short for the Australian Meat & Livestock Research and Development Corporation. As I write, literature from both sources has just landed on my table. By the time it's been digested and discussed with an acquaintance who happens to be well versed in the cattle business, I should have a much clearer picture of the whole subject. In the meantime, I gather that AGTEC's Destron Electronic Identification system is best seen as one interesting piece in an electronic jigsaw that is gradually being number, licence number and so on? With 34 billion possible codes, the system could identify the world! Technically, I'd be interested to know how it works and how reliable it is throughout the life of a typical animal , especially if subjected to electrical storms. But what about the implications? Assuming that the device would be injected into humans in the same place as in animals , a lot of people might find it a real pain in the posterior! P.O. (Murchison, Vic) . superimposed on Australia's huge meat and livestock industry, estimated to be worth about 14 billion dollars in annual export earnings. It is one of more than a dozen electronic identification systems listed by an AMLRDC report as being in existence or under development. "Automation", the key word In fact, Dr Hammond was disinclined to talk just about identification. Research at the University of New England, he said, is best described by the term "automation", aimed towards higher efficiency and increased productivity in all areas of the livestock industry. As such, identification of animals is but one aspect of it. The section "Farm Computer News" in "Farm" magazine indicates an evolution in rural attitudes and methodology, covering records, management and communication. The gradual replacement of cattle yards and cattle sales with video and computer-based auctions is yet another important development, minimising unproductive shipping of livestock. At the other extreme, satellite surveillance promises closer monitoring of overall water and pastoral conditions. As far as animal identification goes, Dr Hammond suggested that AGTEC's Destron Electronic Identification system is more suitable for "intensive" situations, involving detailed supervision of relatively small numbers of valuable animals as for stud and breeding purposes. The mere fact that the reading range is less than 10cm means that you have to walk right up to each animal to obtain the required data. This would be too time-consuming for most operations involving larger numbers of cattle. For these, a reading range of at least one metre is needed, so that cattle can be checked as they pass through a race. For more open situations, a reading range of from 5 to 25 metres would be an advantage. Subminiature implants face an inherent problem in this context because sensitivity is limited by their small physical size and because of signal attenuation due to the body of the animal. With these aspects in mind, the university group itself has four different systems under development. Two of them, one optically enabled, the other using ear tags, are apparently well advanced; the remaining two are still in the prototype stage. According to Dr Hammond, it is unlikely that any one method will satisfy all stock situations. However, he hopes that the cattle industry will adopt a common standard for all recorded data. This would allow it to be transferred easily, irrespective of how it is recorded, stored and read at the property. Back to P.D's letter P.D. wonders how reliable electronic implants might be over the life of an animal and whether they will be vulnerable to lightning. Frankly, I doubt whether any device that depended on a magnetic pattern would be taken seriously vulnerable not only to lightning but to a mains-powered eraser! Much more rugged technology is available in the form of SAW [surface acoustic wave) devices chip-like resonators with a coding pattern of microscopic metal OCT0BER1989 87 plant device which, as fas as animals are concerned, involves a routine that differs little from an ordinary injection. What concerns P.D. is whether the experience and expertise gained by implanting livestock will end up as a routine that, for humans, would be no more difficult than an inoculation. Indeed, in terms of after-effect, it might well prove to be less traumatic than some of them! Real or imaginary? THE MICROCHIP TRANSPONDER is injected into the animal's rump to a depth of 13-32mm using a spring-loaded 12-guage syringe. The implant is far less vulnerable to damage or loss than external ear tags. fingers deposited on the surface. An incoming pulse of RF energy initiates a piezo-like surface wave, which is affected, in turn, by the metal fingers . When triggered, the device radiates an RF pulse of its own, modulated according to the coding pattern. At present, the industry is talking in terms of a 5 to 10 year life for electronic tags, even when battery powered. The life of Destron Electronic Identification capsules, activated by external HF induction, is rated as "indefinite". Details aside, however, P.D's interest in implant tagging is understandable. The idea would appear to be particularly attractive for island countries like Australia 88 SILICON CHIP and New Zealand, where a properly maintained national registration system should make it possible to identify valuable animals - or carcases. But if there is reason for P.D. to show initial enthusiasm for the scheme, I can also understand his reasons for having second thoughts about it: animals today, humans tomorrow! Looking back over the past 100 years in particular, homo sapiens has established a brilliant record in developing new technology. Unfortunately, over the same period, society has failed dismally to take proper account of its possible effects and implications. So now we have an electronic im- The tagging of humans couldn't happen, of course. People, as distinct from animals, wouldn't put up with such a blatant invasion of their rights as an individual. Or would they'? It's amazing what people can be forced to put up with under duress from a dominant military, political or religious dictatorship. Fit names to that statement if you want to! Nor are we talking about simple matters of right or wrong. As with our own tax file numbers and credit listings, a powerful " Yes" case can be assembled in terms of communal responsibility. But the more pervasive a measure, the more it can be abused by anyone who has a mind to do so. Technically, the step from animal to human implants would seem to be relatively small. It is conceivable that an administration, somewhere, in the forseeable future could decide that this was the most effective way to regiment the citizenry, for whatever purpose. But humans are resourceful, cantankerous creatures and it wouldn't be too long before the technogical peers of those who devised the implant in the first place would come up with a way to falsify, remove or replace it. Electronic implants might, in fact, prove easier to deal with than the tattoos which many victims of the infamous holocaust still carry. On an international scale, the organisation needed for a truly universal and unambiguous implant/registration scheme would seem to be impossible of achievement. Historically, nations fail to reach consensus on just about everything. I fail to see why it would be any different with a PHILIPS FLUKE should be without them! 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(*RRP) BANKSIA INFORMATION TECHNOLOGY (AUSTRALIA) PTY LTD 205/83 Longuevi lle Road, Lane Cove , NSW 2066. Telephone (02) 418 6033 Fax (02) 428 5460. TL20: Industrial Test Lead Set 80i-Kw: Current/Power probe 1A-1300Adc lA-l000Aac 0.5 kw to 330 kw ~ 80T-150u: High accuracy probe that converts your DMMintoa thermometer plus a wide variety of soft and hard carrying cases, probes for RF, current, high voltage, temperature and much more. Next time you need a DMM accessory, remember Fluke. N o DMM should be without one. Available from: A.C. T.- John Pope Electrical 80 6576, - Ae rom o tive Main te nance services 85 2377, Geo r ge Brown Group 00 4355, N.S.W. - Am es Agen cy 699 45 24, - George Brown & Co. 519 5855, -DGE Systemsf049I 691625, - W.F. Di xon f049J 69 5177, -Ebson 707 2111 , Macelec f042I 29 1455, -Novaca strlan Elect r onic Supplyf049I 62 1358, -0biat 698 4776. - Petro-Ject696 9655, -David Reid 267 1385, N. T. - J. Blackw ood &Son 84 4255, -Thew & Mccann 84 4999, OLD . -AuSlec 277 6055, - Petro-J ect f07I252 2777, -st. Lucia Electronics 252 7466, - l.E . Boughen 369 1277, - Haytech 844 9396, - Th o mpson Instruments f070J 51 2404, - Nortek f077I 79 8600, - Colou rvl ew Electroni cs 275 31 88, s.A. - Electecn 277 1533, - Petro-Ject 363 1353, - George Brown Gro up 35 2 2222, TA S. - George Harvey Electric 31 6533, - Petro-Ject 10031 44 8400, VIC. - Radi o Pa rts Group 329 7888, - George Brown Group 878 8111 , -Electech 482 1577, - Petro-Ject 1031419 937 7, - Factory controlS 10521 78 8222, - Mektron ics !031 587 3888, W.A. - Atkin s Ca rl yle 481 1233, - oobb ie Instr uments 276 8888, - Petro-Ject 479 1822, OCT0BER 1989 89 context, "imaginary" ailments may indeed respond to imaginary cures. The above is a mere precis of K.W. 's original remarks enlivened, I gather, by the fact that, years ago, he shared a flat with a lady who _was so far into all this that some may have considered her to be "a couple of sandwiches short of a picnic, having already mislaid the thermos"! Among her prized possessions was what she described as a "Radioaesthesia" transmitter obtained, apparently, from a company that appeared to specialise in electronic gadgets for alternative practitioners. Unfortunately, something appeared to be loose inside and while the unit was still "working"'. K.W. was entrusted with the job of checking it out. He says (somewhat abbreviated): "The unit was housed in a wooden box, a little larger than a house brick and covered with leatherette, much like an old-time portable radio. The front and sides carried an array of knobs, all identical and marked with the numbers 1-10 but with no clue as to their function. Under the lid was a sort of control panel, with a mains switch a pilot light and a couple of shin; plates. The non-circuitry THE NU~BER ~NCODED into the transponder can be checked and displayed at any bme using a portable scanner. The reading range is about 75mm. universal identification scheme. But that certainly doesn't mean that we shouldn't remain alert to the possibility. In the meantime, let's change the subject from hightech to the other end of the electronic spectrum. "Snake oil" machines Keith Walters, whose observations about high definition television were featured in these columns in the last couple of issues, has come up with some further observations about "alternative" therapeutic treatments and what he calls "snake oil" machines. That he should have outspoken views on the subject is not 90 SILICON CHIP altogether surprismg, since he is apparently associated with Australian Skeptics. A lot of "ailments", he claims, are psychosomatic in origin; the symptoms are real enough to the person concerned but they still have their origin in the brain. Conventional medical practitioners are well aware of this but they are also aware of patients' reluctance to accept such a diagnosis. But introduce them to someone who is prepared to blame food additives, or recommend colonic irrigation, or specify a special diet, or pills and potions from a health shop, or endorse a crystal whatnot ... and they go along with it. In that "Unscrewing this panel revealed what looked like an array of army surplus pots, wired together higgledy-piggledy, with no evidence of any logical wiring pattern or of other associated components. I could find no internal connection whatever to the shiny plates. "There was also a circuit board and a small power transformer the latter being responsible for the 'something loose' complaint, having come adrift along with the PK screws that were supposed to secure it to the wooden baseboard. In the process it had crunched three germanium diodes on the circuit board. "As for the latter, any electronics enthusiast from the 1960s and 1970s would have recognised it as a Burroughs (or other such) computer board that represented hightech for the era but which ultimatecontinued on page 111 New column on computer hardware SUBSCRIBE SUBSCRIBE SUBSCRIBE Have SILICON CHIP delivered direct to your door at no additional cost. Each month, we'll bring you the best and brightest electronics magazine, put together by Australia's most experienced team. • • • • • • i ' ~- i Police radar: it's not always right ' J Intelligent charger 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. SUBSCRI PTION 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. (P LEASE 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 □ $A130 Overseas airmail □ $A 1 20 □ $ A240 Enclosed is my cheque/money order for $. _ _ _ or please debit my □ □ Bankcard Card No. I 1 11 □ Visa Card 11 i 11 MasterCard 11 11 111 I Signature _ _ __ _ _ __ _ Card expiry date _ _ /_ _ / _ _ OCT0BER1989 ~ Of() 91 I PRODUCT SHOWCASE I Miniature transformers PC slot extension cards These two extension cards can be very handy when evaluating new cards or peripherals for your IBM PC XT and AT. The PCL-755A can be regarded as a vertical extender - you plug it into a motherboard slot and then you plug cards and cables into its edge sockets. It has fuses on board for the + 5V and + 12V rails and + 5V and GND pins for logic probe connections. The PCL-755C slot extension kit adds cables to the PCL-755A to allow another card, the PL-755B, to be used outside the computer. As supplied, it can take three standard extension cards. Price for the two cards, cables and hardware is $199 all up. For further information on these extension cards contact PC Marketplace, PO Box 1100, Lane Cove 2066. Phone (02) 418 6711. These days there are too few local manufacturers of small transformers who can deliver quality units quickly. The 4VA units pictured are available in voltages of 2 x 6V, 2 x 9V, 2 x 12V and 2 x 15V. They are wound on glass filled nylon safety bobbins and with grain oriented steel laminations. Naturally, they comply with the relevant clauses of Australian Standard AS3126. For further information on the complete range of transformers available, contact Harbuch Electronics Pty Ltd, 90 George Street, Hornsby, NSW 2077. Phone (02) 476 5854. Mercury wetted reed relay in OIL format Digital blood pressure monitor Many people need to take medication to control their blood pressure and they need to have it monitored regularly. For best results this should be done at home where you are most relaxed - patients' blood pressure often rises during a visit to the doctor. This digital blood pressure monitor makes the job easy. Just fit the cuff around your upper arm, blow it up with the hand puffer and the machine does the rest. It takes your pulse and measures the systolic and the 92 SILICON CHIP diastolic pressure. No stethoscope is needed! The unit sells for $119 and is available from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385. Now available from IRH is this Clare MSS2 mercury wetted relay in DIL format. It has a contact resistance of less than 100 milliohms and is available with coil voltages of 5, 12 or 24V DC. Nominal input power is as low as 178 milliwatts and operating time is less than 1.5 milliseconds. For further information, contact IRH Components, 32 Parramatta Road, Lidcombe, NSW 2141. Phone (02) 648 5455. Nifty nibbler from Altronics Control board attaches to PC printer port Fancy a nibble on some tasty sheetmetal? Why not? We all need a certain mineral intake. However, if you don't want to use your teeth, this handy nibbler from Altronics is ideal. It will handle almost any metal (except stainless steel) up to 18 gauge. It is priced at $19.95 [Cat T-2355) and is available from all Altronics dealers. Polarity guarded tantalum capacitors If you insert a tantalum capacitor into circuit the wrong way around, it will ultimately fail. If the voltage across it is relatively high, it might fail straight away, possibly with catastrophic results. If the reversed voltage is low, the capacitor might function for months or even years before failing and then possibly causing an expensive repair job. Recognising this, Siemens has now produced a range of tantalum capacitors which have polarity guarded leads. This works provided the PCB holes are of the correct diameter. The positive lead is 1mm in diameter while the negative lead is 0.7mm in diameter. For further information, contact the Electrical Components Department, Siemens Ltd, 544 Church Street, Richmond, Vic 3121. Phone (03) 420 7716. Do you wish to use your PC for process monitoring, laboratory automation, energy management or home or business security. If so, this digital I/O (input/output) board from Procon Technology will be of interest. Designed to be controlled from the standard parallel printer port on an IBM PC or compatible, the PC-IO-NR board provides 8 SPDT relay outputs and 8 optoisolated 24V AC or DC inputs. Four DIP switches on the board select the address setting on the PA-BUS and so up to 15 such boards can be connected to a single printer interface. Software to operate the board is supplied on a 5 ¼-inch floppy disc drive and the connecting cable to the printer port is included in the price of $270. For further information, contact Procon Technology, PO Box 43, Essendon, Vic 3040. Phone (03) 336 4956. New card allows colour graphics software on mono monitors That heading is not wrong. One of the big drawbacks of the IBM PC standard is that programs written for the colour graphics adaptor will not run if you have a monochrome display adapter card and a monochrome monitor. As soon as we heard about the "Magic Combo" card we thought it would be ideal in one of our IBM PC compatible machines. These are used primarily for magazine production and so employ MDA cards and monochrome monitors. We have ac-. cess to an IBM PC compatible with a CGA card and colour monitor but we decided it would be more convenient if we could run software calling for a CGA card in one of our office machines. What the magic combo card effectively does is to provide a standard TTL monochrome signal for all software requiring an MDA (monochrome display adapter) and CGA (colour graphics adaptor) card. As well, it provides a parallel printer port as found on standard MDA cards. To do this, it must transform the normal CGA 640 x 200 pixel format [with 15.75kHz horizontal scan, 60Hz vertical scan) into the MDA's 720 x 350 pixel format [with 18.4kHz horizontal and 50Hz vertical scan). To depict the 16 colours of a CGA display, it translates them into a 16-step grey scale. It does all this transformation without any distorOCTOBER1989 93 NEWPRODUCTS-CTD tion of the images. Pretty clever, eh? Compared with the full size monochrome plus parallel printer card which is fitted as standard in our PC-compatible machines, this new Magic Combo card is really small, about one third the size of the full size card. It measures only 106 x 106mm. It effectively replaces the full size card which you really can't use any longer anyway. When installing the new card you must change the settings on the DIP switches on your computer's motherboard. The card comes with quite a good instruction manual plus some supporting software on a 5 ¼ -inch floppy. How does it work? It works very well we found . It also provides compa tibilty with Hercules graphics and the light pen used in some CGA software. The price of the Magic Combo card is $129 from Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 906 36666 or fax (02) 906 5222. Five new PC-mount transformers wound PC-mount transformers are very welcome. They have a nominal power rating of 7V A (ie, approximately 7 watts) and are available with secondary output voltages of 6V + 6V, 7.5V + 7.5V, 9V + 9V, 12V + 12V and 15V + 15V. In each case the secondary windings can be connected in series to double (add) the voltage or connected in parallel to double the current. Their type numbers are M7112, M7115, M7124 and M7130 respectively. For further information, contact Altronic Distributors Pty Ltd, 17 4 Roe Street, Perth, WA 6000. Phone (09) 328 2199. Assorted wire packs from Arista Looking for a transformer for that new project? Sometimes the selection available from existing suppliers can seem very limited. All of which means these new bobbin These handy packs of wire can be shot into your toolkit and since they're in a blister pack they won't get tangled up. They're available in a large range of wire sizes and colours with the larger sizes being especially useful since so few kitset suppliers have them. POWER TRANSFORMED TV TEST EQUIPMENT (AUSTRALIAN MADE) SHORTED TURNS TESTER Built in meter to check EHT transformers includ ing split diode type , yokes and drive transformers. $78.00 + $3.00 p&p HI-VOLT AGE PROBE Built in meter reads positive or negative 0-50kV. For checking TVs, microwave ovens. $84.00 + $5.00 p&p. t J ~ A comprehensive range of Aust- TELE-TEST TUBE TESTER & REJUVENATOR Removes cathode grid shorts & rejuvenates picture tube. Suitable for all colour tubes 12 months warranty $420.00 + p&p. TV TUNER REPAIRS PYE LMD3 1 Turret repair only . . .. $18.00 + $2.00 PHILIPS (ELC 2060) repair & exchange ... . . $17.00 + PHILIPS (UV 461) repair only .......... .. $18 .00 + PHILIPS Turret repair & exchange .. $18.00 + AWA MITS Varicap repair only . . .......... $18.00 + p&p p&p p&p p&p p&p Cheque, Money Order, Bankcard or MasterCard =r-.V.TuNERs) 94 SILICON CHIP 216 Canterbury Road, Revesby, NSW 2212. Phone (02) 77 4 1154 ralian made safety-designed PCB mount power transformers in 6 power ratings and 7 vo ltages are now ava ilable ex-stock. Mains pins are offset so that the transforme r cannot be inserted in the PCB in the incorrect manner. To special order the mains connection can be removed from t he PCB and taken to quick disco nnect lugs on the top of the transformer. In all sizes frofn 6V A up a multiple winding model is availab le whi ch with the correct 3 terminal regu lators will provide +/-1 SV for audio circuits and +SV for CMOS and LSTTL circuits. 6 CONVENIENT SIZES 2.SVA, 4VA, 6VA, lOVA, 15VA, 25VA STANDARD VOLTAGES 2 x 6V, 2 x 7.5V, 2 x 9V, 2 x 12V, 2 x 15V, 2 x 20V at 15VA and larger, 32Vct + 8V at 6VA and larger .. Data sheets and prices are available direct from the manufacturer. HARBUCH ELECTRONICS PTY LTD 90 George St., HORNSBY NSW 20 77 Phone (02)476-5854 New CD players from Sony Each pack weighs the same so the lighter gauge packs have a longer length of wire. All packs sell for the one price, $8.95 , and they are available from all Arista outlets. While it has been possible to purchase a CD player at under $300 for some time now, their quality has often been suspect. Now Sony has released two players which offer a good range of playing facilities at under $350 and, importantly, they both Low cost, low noise dual PNP transistors Anyone designing very low noise audio equipment will be interested in this very low noise matched PNP transistor pair from the SSM Audio Products division of Precision Monolithics Inc (PMI). Designated the SSM-2220, it offers a very low input noise voltage of about 0.7 nanovolts per root Hertz over the range from 20Hz to 20kHz. In addition, it offers high current ga in, excellent log conformance, and low offset voltage which makes it ideal for use in preamplifiers, multiplier/divider circuits, voltage controlled amplifiers, current sources and current mirrors. The SSM-2220 is packaged in an carry the Sony name. Both offer 4-times oversampling and an edit feature which allows time and program editing, as well as time fade track selection for transfer to tape. The CDP-M27 (355mm midi size) sells for just $319 while the large CDP-270 (430mm wide) sells for $349. They are available from all Sony dealers. 8-pin epoxy DIP and its performance is guaranteed over the temperature range fr om - 40°C to + 85°C. For further information, contact VSI Electronics (Aust), 16 Dickson Avenue, Artarmon, NSW 2064. Phone (02) 439 8622. PCBreeze II $295 The First Truly Affordable Software for Printed Circuit Board Artwork Easy to Use and Learn Pop up Menus and Mouse support 50 mil (1.27 mm) Grid Variety of Pad and Line sizes Interactive and Netlist Autorouting Text and Component Overlay Hardware Supported 448K IBM PC/XT/AT/PS2 or compatible CGA,EGA,VGA & Hercules graphics HP-GL, DM-PL, PostScript dev ices Epson FX/LQ type dot matri x printers Microsoft Mouse or compatible device KEPIC Pty Ltd 4 Steinbeck Place Spearwood 6163 Western Australia ph: (09) 418 5512 Free shipping within Australas ia Dealer inquiries Welcome OCT0BER 1989 95 DISK BOXES DISK STORAGE UNITS • 80 x 3 1/2" - Lockable C16038 ......... .. .. ..... $16.95 "NO BRAND" DISKS • 40 x 3 1/2 ". Lockable 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 ol 10, D/S DID without box es, or brand name, just their ----•■ whitepaper jacket, and index label. (5 1/4" disks includes write protects) C16035 ........... ....... $14.95 • 40 x 3 1/2 ·· "Eclipse·· C16040 .................... $8.99 r. ----------,I 386SX 16MHz MOTHERBOARD I. I. I I I. I. I I ._ I Processor: 80386SX-16MHz (0/1 wait state) Co-processor:80387SX-16 (optional) CHIPS & TECH NEAT chipsets • (SMT) Surface Mount Technology for 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 5 1/4" 2S/2D "NO BRAND" DISKS 1,000+ DISKS $6.00 $5.75 $5.50 __________ CASES IBM* XT COMPATIBLE CASE WITH AT* STYLING C16025 .......... ... ..... $14.95 • 100 x 51 /4 ""Eclipse" C16042 ................ .. .. $9.95 Features security key switch. 8 slots, and mounting accessories Size: 490(W) x 145(H) x 400(D) • 100 x 5 114 ". Lockable C16020 ..................$15.95 5 1/4" HIGH DENSITY DISKS 10+ DISKS (DOUBLE SIDED) 100+ DISKS • 120 x 5 1/4 .. _ Lockable 1,000+ DISKS $21 $22 $23 .., • 120 x 3 1/2 ". Lockable • 50 x 5 1/4 ". Lockable 100+ DISKS I I I I I I I _.I X18094 .................... $900 4.o C16039 ...... ... ......... $21.95 (ALL PRICES PER 10 DISKS) 10+ DISKS • Supports Page interleave Mode using 100NS DRAM • BIOS: AMI or PHOENIX • Turbo Light and Hardware Reset connector , Keyboard or Hardware Reset connector • Power Good ~1gnal on board • Baby size main board 3 1/2" 2S/2D "NO BRAND" DISKS $21 C16028 .................. $19.95 BABY AT* STYLE COMPUTER CASING DISK DRIVE Small footprint. Features security key switch, 8 slots and mounting accessories Size: 360(W) x175(H) x405(D)mm UPGRADE YOUR COMPUTER WITH A 3 1/2 " DRIVE KIT X11093 ....................... $99 X11091 .. .... ................. $99 MIDI CARD 3 1/2" 2S/HD "NO BRAND" DISKS 10+ DISKS $65 100+ DISKS 1,000+ DISKS $59 $53 MIDI INTERFACE CARD - DS/401 Remount your computer to give it that professional look , • Accepts XT, AT, Baby AT and 386 boards • Horizontal full height hard disk drive mounting • Room for 2 x3 112" and 2 x 5 1/4" floppy drives • Full height HOD plus Ian mount • Size: 165(W) x 600(H) x 500(0) The MIDI DS-401 Card is the PC standard MIDI interlace that runs most popular PC music programs for 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 fit in any computer accepting standard expansion card, including laptops • Including "Y" cable, external connector box to transport is unnecessary X11105 ..................... $250 X18164 ... ..... ........ .. ...$195 Y.E DATA 3.5" 1.44/ 720/ 360 DRIVE • 5 1/4" Mounting bracket • Power supply adapter • Floppy Disk controller card which controls 1.441 7201 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. VERBATIM DISKS (ALL PRICES PER BOX OF 10 DISKS) DESCRIPTION 1-9 BOXES 10+ BOXES 3 3 3 5 5 5 5 $29.95 $34.95 $74.95 $19.95 $23.95 $31.95 $31.95 1/2" 1/2" 1/2" 1/4" 1/4" 1/4" 1/4" 1S/2D ...............$32.95 2S/2D ............... $37.95 2S/HD .............. $78.95 1S/2D ............... $21.95 2S/2D ............... $25.95 2S/4D ... .. ...... ... .$33.95 2S/HD .............. $33.95 TEFLON COATED DISKS VERBATIM DATALIFE PLUS Teflon* Coated (ALL PRICES PER BOX OF 10 DISKS) 5 1/4" DS/DD 1-9 C12522 ...................... $29.95 5 1/4" High Density 1-9 C12523 ...................... $38.95 10+ ....................... ONLY $355 HARD DISK ' REMOVABLE CARTRIDGE HARD DISK Ricoh R260 20 M/Byte Removable Hard Disk is a subsystem for AT or 386 systems. Extra 20 M/Byte cartridges are available. To enable the end user to build a library that can be safely locked away. Or taken to another site that is using the same sub-system. It's the ultimate in hard disk back up ' systems or for transport ability of data. $27.95 Includes a cartridge X20022 .................. $1,27 4 10+ Extra 5 1/4" 20 M/Byte cartridge for disk (Ricoh RH5260) $35.95 X20024 ..................... $220 TOWER COMPUTER CASING r ---- -----,I 286 NEAT MOTHERBOARD I I I I I I I ._ I I • • Processor: 80286-12, -16MHz or -20MHz (0/1 wait state) • Co-processor: 80287 (optional) • CHIPS & TECH NEAT chipsets • 1-4MB dual RAM socket • ~~4~:.,;odule RAM socket • 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 X18090 ................. ·• · $ 00 7 20MHz X18092 .................... $895 • I II I I _________ _.J1 I -- I GENERAL POWER SUPPLIES NEWCRO'S SUPER FAST DYNAMIC RAM • 4164·120ns U20832 ........ ............ $4.50 SUPER BRIGHT LEDS • 4464•100ns • Red .......... ..... Z10146 • Green ........... z10147 • Yellow........... Z10148 1·9 10+ $1 .00 150W SWITCH MODE POWER SUPPLY FOR IBM* PC/ XT* & COMPATIBLES DC OUTPUT: • +5/ 13A, •SV/ 0.SA • +12VI 4.5 - 12V/0.5A X11096 ............. ........ $149 U48262 .................. $12.30 • 41256·100ns U48260 ....................... $10 • 1MB•100ns CANNON TYPE CONNECTORS AT SPECIAL PRICES!! Cat. no. Description Price P10960 3 pin line male ... .. .. $2.90 P10962 3 pin chassis male$3.25 P10966 3 pin chassis female$3.75 DC OUTPUT: +5116A, -SV/ O.SA +12V/5A • 12V/ 0.5A 20MHZ DUAL TRACE OSCILLOSCOPE JUMP WIRE KIT (KS-350) Contains: 14 k inds of length from 0.1 " to 5" with different colors 011278 ... ... ............ $19.95 TEST EQUIPMENT MULTIMETER (YF-100) • Autoranging for DCV, ACV, OHM & continuity measurement • AC DC O • 500 Volts • 10mm thickness & 80g light weight for easy operation • Dimension & weight= 108 x 54 x 8mm and 60g approx 011264 ....................... $69 U48270 .................. $26.50 VERTICAL DEFLECTION • Deflection Factor: 5mV to 20V/ Div on 12 ranges in 1·2·5 step with fine control • Bandwidth DC : DC to 20MHz (·3dB) AC: 10Hz to 20MHz (·3dB) • Operating Modes: CH·A, CH·B, DUAL and ADD (ALT/CHOP L202 only) • Chop Frequency: 200KHz Approx. • Channel Separation : Better than 60dB at 1KHz • 6116 U20950 •••••.••••.••..•.... $9 .95 • 6264•10 U20952 .................. $19 .95 • 62256•10 U20954 ....................... $45 TIME BASE • Type: Automatic and normal triggered in automatic mode , sweep is obtained without input signal :r;le STATIC RAM TRIGGERING • Sensitivity In! : 1 Div or more Ext: 1Vp•p or more • Source : INT, CH•B , LINE or EXT • Triggering Level: Positive and Negative, continuously variable level ; Pull for Auto • Sync: AC, HF Rej , TV (each+ or·) at TV Sync. TV•H (line) and TV•V (Frame) sync. are switched automatically by SWEEP TIME/Div switch. HORIZONTAL DEFLECTION • Deflection factor: 5mV to 20VI Div on 12 ranges in 1·2·5 step with fine control • Frequency Response: DC to MHz (-3dB) • Max Input Voltage: 300V DC + AC Peak of 600Vp•p • X•Y Operation: X-Y mode is selected by SWEEP TIME/ Div switch • Intensity Modulation Z Axis: TTL Level (3Vp-p - 50V) + bright, • dark OTHER SPECIFICATIONS • Weight: 7Kg Approx • Dimensions: 162(H) x 294(W) x 352(0) mm 012105 .... ..... ........ .. ....... ..... ... ........... ..... ................ $695 -· MULTIMETER (YF-2100) LOGIC PROBE (LP-2800) • Useful for TTL or CMOS has high and low indicator leds and also with pulse memory. • This is a very handy tool for the hobbyist or serious technician for tracing those hard to find faults on logic boards. 011272 .................. $34.95 • Large display 41 /2 dgt o.5'· height LCD with maximum reading of 19999 • AC DC O -1000 Volts • Automatic polarity."•" display for negative input • High over•load protection for all ranges • Over load display, the highest digit "1" or "·1 " alone glows • Power consumption 20mW approx. • Dimension & weight= 162 x 86 x28mm and 200g approx 011266 ..... ... ....... ...... $199 8 • MULTIMETER (YF-3000) • Instantly shows the open/short position of PCB • It can test whether PCB or solid wire open/short by Buzzer • Large display 3 112 digit 0.5" height LCD for easy readout • AC DC O • 1000 Volts • Auto/manual range select easy to operate • Automatic low battery" • + " display for battery Indication • Memory•comparative function available for allowance within ±5% f .s • Warning sound for overload and conductance • Dimension & Weight = 170 x 80 x 33mm , 260gram approx • Data hold function for easy readout 011276 ..... ......... .... $22.95 011268 ..................... $110 SHORT TESTER U48265 ....................... $25 • 1MB•80ns CRT DISPLAY • 150mm rectangular • Sweep Time: O.~µ Sec to 0.5 Sec/ Div on 20 ranges in 1·2·5 step with fine control and X· Y • Magnifier: X5 at all ranges X11097 ..................... $199 180W SWITCH MODE POWER SUPPLY FOR BABY AT* COMPATIBLES X11098 ..................... $175 U20842 ..................$10.00 • 41256-BOns $0.90 P10964 3 pin line female . .....$3.50 200W SWITCH MODE POWER SUPPLY FOR IBM* AT* & COMPATIBLE RAM I 4 ·. ~ -,ea._ □ a . ·, .... c I .,_ I ._ .. ROD IRVING ELECTRONICS SYDNEY: 74 Parram atta Rd . Stan more 2048 Phone : (02) 519 3 134 Fax: (02) 519 3868 MELBOURNE : 48 A'Bec kett St Phone: (03) 663 6 151 NORTHCOTE: 425 High St . Phone : (03 ) 489 8866 MAIL ORDER & CORRESPONDENCE : P.O . Box 620 , CLAYTO N 31 68 O rd er Hotl ine: 008 33 5757 (Toll fre e. strictl y orders on ly) Inqu iries : (03) 543 7877 Telex : AA 15 1938 Fax: (03) 543 2648 All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE· 56 Renver Road . Clayton . Phone :(03) 543 2166 (3 lines) Fax : (03) 543 2648 ORDER HOTLINE 008 33 5757 40MHZ READ-OUT OSCILLOSCOPE CRT DISPLAY • 150mm rectangular VERTICAL AMPLIFIER (CH1 and CH2 Identical) • Operational Modes: CH1 , CH2, ADD, DUAL, ALT, CHOP • Sensitivity: 5mV•5V/ Div 3% in 1·2•5 steps 1mV•1V/ Div x5% x5MAG • Bandwidth DC: DC to 40MHz (·3dB) AC: 5Hz to 40MHz (·3dB) • Rise Time: Less than 8.7nS HORIZONTAL AMPLIFIER • Operating Modes: X·Y operation CH1·X axis, CH2·Y axis • Sensitivity : 5mV•5VI Div± 3% in 1·2·5 steps ..,.,..--,--,-=-=---, • Input Impedance: 1M!l±2%, 25pF±3% • Bandwidth DC : DC to 1MHz (·3dB) AC: 5Hz to 1MHz (·3dB) TIME BASE • Sweep Method: AUTO, NORM, SINGLE • Sweep Time (A): 0.2µs•0.5S/ Div±3% in 1·2·5 steps (X1 only) (B): 0.2µ$-0.SmS/ Div±3% in 1•2-5 steps (X1 only) • Magnified Sweep: 10 tlmes±5%, Max 20ns • Linearity: ±3% or better 012107 •••••••••••••• •••••••••••••• •••••••••• ••• •••••••••••••••••••••• $1,695 (TOLL FREE) STR ICTLY O RDERS O NLY LOCAL ORDERS & 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 fo r basic pos1age only. Road Fre ight. bulky and fragile items will be charged at differe nt rates. Errors and omissi ons excepted . Prices and specification s subject to change. IBM· PC· xr AT' a1e registered trademarks ot ln ternat1onat Business M acri 1nes ·Apple 1s a reg is tered Ir a d emark Teflon · Is a reg Is1e 1ed iradema rk ot Dupon1 ·oenonte s regis tered trademark s o! theu res pect,veowners 7th December 197Zenith, USA. G'day Dick, I guess this date must be etched in your memory. It surprised me that a lot of Americans still feel so bitter about it. The chief engineer where I'm at mentioned the sneak attack along with comments that the Japanese were good copiers but couldn't originate ideas. When I mentioned the Yagi antenna and the Esaki diode he feJl ' - --ri· ll'i'et:- I-Wa's7 oo nice to point out that he drives a Japanese car or that his loungeroom houses the flashiest Jap hifi I've ever seen. The last time I wrote, I expected to be staying in Zenith for a couple more weeks. But my company had other ideas. They sent me with a brief to look in on several stations, then they got an emergency call which took me straight away to a little New England TV station. It was a case of the wheel squeaking loudest getting the grease, I guess. Anyway, the field service manager called me and said drop everything and proceed to the problem spot. I sometimes wonder how big companies get and stay big - so much money gets spent on inefficient gyerhaads-ancl-¥e-inven ·· wheel. But I got on a plane, then switched to a smaller one on the East Coast for the connecting flight to a small town I'm surprised even had a TV station. Some time back, I saw a news story on a Mom & Pop TV station in some backwater like Idaho or North Dakota. It was real amateur hour, unbelievably funny. But the producers really missed the boat for the station I went to in a hurry was By RICHARD KOPF ers 98 SILICON CHIP a real one-man band. The entire operation was run by a single person. He was transmitter tech, station operator and on-air talent all at the same time! The news desk even had lever switches underneath by which he could start the telecine or VTRs (two of those). Foot switches were used to operate the studio camera or other sources. Watching him doing the evening news was like seeing someone play the mighty Wurlitzer. Of course, a bloke can't take much of that. It's only the unfortunates down on their luck that end up at such a place. Or young 'uns starting out who are willing to put up with just about anything. I worked out that the average span of employment over an 11-year pertod was three months. It only took me a couple of hours to get their VTRs up to scratch. The previous operator reckoned he was an engineering whiz. The things some people do to servos! The owner screamed to high heaven when I told him he would have to pay a service call. He maintained it should be free, under new equipment warranty. I told him no mechanical or electronic faults had been found - only proper adjustment procedures had been followed to get the machine to meet specs. Well I was only passing on policy, as delivered to me. This bloke took exception and immediately called my boss to complain. He had to ad- 1B =·~ ' : , . .,.· o,0 0 ,,.,oHE- WA-S ~MlTr6R -re.cH, SU\TlON ~AATOR ANP Ot--l-A\'R ~L~ ALL. A, ,He: SP\N\E: .,-\t../\'cmit he did not take the extended warranty option, which included a 2-year service contract - nor did he intend to. His final threat was that he would never again buy anything from our company. At that, the field engineering manager asked to speak to me, promptly blamed me for the altercation and said we would wear the costs involved. I put the owner back on, who smiled when he heard this decision. Now the bloke had never bought equipment from us before and chances are it would be years before he could afford more gear. So I don't believe we would have lost anything by making him pay his way. But that's not the way you Americans approach business. For instance, OCV A bid low on that Middle East contract. It was so low, the Minister of Information told them to raise the tender by half-amillion. Their reply: we don't care if we lose money on this contract. Once we prove ourselves in international television, there's Greece, Morocco, South Africa and so on. No sooner had the Arabs welcomed the fools with open arms than the head office was scheming how to cut corners. But every ploy they tried cost them more money. They spent so much on sending disaffected engineers home that they could have bought an airline probably. While I was there, one bloke wrote an 11-page letter back to head office, telling them what was wrong with their operation. Naturally, they took no notice of his advice and constructive criticisms - but censured him for being a troublemaker. The dreaded IRS I didn't understand the subtleties of the situation when I first went there. Now that I have had experience with the Internal Revenue Service, I can appreciate it from another point of view. The company signed Americans up for a one-yt;Jar contract, pointing up the advantages of tax-free income in foreign countries. The lurk was, you had to be out of the US for 18 months to be exempt OCT0BER1989 99 THE TECHNOLOGY LETTERS - CTD from US tax. Thus, at the end of your first contract, one couldn't afford to go back and hand over a big lump sum to the IRS. So you accepted the contract re-negotiation on the company's terms. The "troublemaker" was told he would only get a 5 % increase. Three months after reluctantly taking it, they sacked him on a pretext. If they hadn't liked him before, they really hated the outcome. This bloke had really got into the Atab culture. He was learning the language, used to be invited to eat their food by the studio crew, and generally socialised with them offduty. In the station, he had trained one local into a crack videotape operator. So he was owed favours. Three weeks after yet another chief engineer arrived, he called the "troublemaker" in and said: "I don't know what's going on and I don't want to get involved but the project manager wants you out of here. Resign or be sacked". Swift justice The troublemaker had a fair idea of the Arab ground rules. He chose to be sacked. The VTR operator spoke to his uncle at the Labour Ministry and a claim against OCV A for unjust dismissal was filed and accepted. About 10 days later, all interested parties attended a preliminary hearing. The Arab came along as an unofficial translator. He and the troublemaker arrived early and had tea with the magistrate. The company representatives sauntered in about 20 minutes late. By then, it was a foregone conclusion. The Arabs are even more "face" conscious than the Orientals . The magistrate felt offended •• 011-te:. ANCHoR MAN AN'D 1SPORT'S RE.~OR \ E:.R EN't"ERe:D ,~ CON\~-r UN\R>RMoo, 100 SILICON CHIP and ignored the company representatives. It came to a question of negotiated damages. Funny thing is, if the bloke had elected not to accept the company offer, he would have been kept on the payroll until such time as the case came before the court proper. The magistrate explained that of course he would not be allowed to work, since the company did not want him. We were a bit surprised he took the quick settlement. He explained that the lag in the courts was anywhere from eight months to well over a year and that he might get too used to being paid for nothing. Besides, he said, he had the satisfaction of having had the first settled case by an American against an American co,m pany there. So five more airline tickets - his family was there also you see. I think I mentioned the chief engineer with heart problems, or something. When he was diagnosed, he was advised to go to American University Hospital (in a different country) for some tests. The project manager refused his petition for time off but the chief went anyway. No sooner had he got on the plane than the project manager called the ministry and revoked the man's work visa. In theory, he could not get back into the country again. So there he was, in another foreign country, his personal possessions beyond his grasp - until he called a mate in Washington DC. Problem solved. In short, there were lots of payouts, payoffs and generally inefficient overheads. Well I finished my one and only year and was off like a shot. I didn't have the same tax problems as you Yanks. I found out later that we were ripped off anyway. After we all arrived there, we were told it had been decided we would have to pay Arab income tax. It was only a few percent, so nobody minded too much. But it turns out that the tax levied was supposed to be paid by the company, not by individuals. Ah, well . When their contract was running out, OCV A re-tendered at a realistic figure. The Minister told them such an increase was not justified and hired independent consultants. Current adventures After that digression, I'll return to current adventures. What brought it on, of course, was the strange idea of losing money now being an investment in the future. My field engineering junketing has been due to a conflict in the corridors of power. The services manager wanted to empire build, started hiring more engineers and selling more service contracts. The financial side of the empire loved the idea of more service contracts but told service to cut back on staff. So people who've been there only a few weeks are already being put off. I suppose my turn will come sooner or later. But the nasty thing about customers with service contracts is that most of them actually expect service. And now there aren't enough warm bodies to go around. Which is why I have been moving like a yo-yo. From New England, I made a quick stop in Virginia, then across country to Seattle. Whilst there, the boss complained that the Zenith stations had been bugging him. Since I was now on the West Coast however, they would have to wait, as I received new orders to go to Hollywood. There's something about the Tinsel Town mentality. I had jobs to do at a network station. They were anticipating some big special and the excuse of the day was: "We're genlocked to New York". I started looking at one telecine and told the area supervisor I needed a working waveform monitor and pointed to the erratic trace on the CRT. "That's because we're genlocked to New York". Abandoning that project for the moment, I found a VTR in another area and cleared its use with the operations supervisor. During my alignment, an engineer told me "You won't get that machine to lock up properly. We're gen ..." " .. .locked to the Big Apple", I finished. In a few minutes, I had the beast colour locking from a dead start in under three seconds. The expert nodded and walked away, saying: "Looks like you synchronised with New York". One of the technical directors I met there was spot-on, though. Jim had started out as a junior maintenance technician to get into television. He always had plans to get into producing and had written several scripts. He told me a wild story from his army experience. Back in the days of the peacetime draft (about 1968 for him), he realised his number would soon be up. Some of his mates had waited to be called up and ended up serving two years in work which did not further their careers at all. Jim enlisted on the proviso that he would be assigned radio or television work after basic training. Fortunately, he was in luck. Some blokes who tried this approach were diddled, despite the assurances they received. He spent some time in Washington DC doing recordings for Armed Forces Radio. Then they asked him if he could produce a TV program for Armed Forces Day. From what he says, he took on the assignment and did a good job, despite some difficulty with a certain major. After the program went to air, Jim was re-assigned to Korea. After he'd been there a few months, working in the military TV station in Seoul, the new CO arrived; the major who was the bane of his life in Washington. This officer was a real "book" soldier and interpreted an order which came down the line about a training exercise to mean that all troops were to be in the uniform of the day. Now the long-serving men there had gradually eased into a rather civilian look. Their evening news looked just like ordinary network TV with blokes in blazers etc. The major got pretty hard-nosed about "orders is orders". One evening, the news program started with a fade-up from black to - a jungle scene, night effect. Sound and lighting effects gave an impression of impending battle. The lights came up, and the anchor man and sports reporter entered from the wings in combat uniform, rifles at ~L'-<\Ne;. 1)\J\CI-\N\AN AN"D "POR.1-:.... OCT0BER1989 101 port arms. They marched toward one another. The lights came to full brightness, the mortar and machine-gun sounds faded away. They took their places and the news program went off normally. Everyone got a big giggle out of it, except a visiting two-star general. When he got to the truth of the situation, the major was reassigned - to Greenland. Everything returned to business as usual. Incoming missiles My boss decided that, for my next trick, I could go back to Zenith. One thing about long plane trips, you can sometimes strike up some interesting conversations. The bloke next to me on the flight had worked for Ma Bell for 20-odd years. I don't know if his yarns were true but they sure were entertaining. According to him, back when the DEW line was being developed, we nearly had World War III. Once the chain of high-power radar sites was completed and linked together, the military and site contractors did a preliminary test. Everything seemed to be performing properly, as many inspections and checks had been incurred along the way. Suddenly, the chief operator announced: "My God! There are missiles coming over the pole". Near panic ensued. System malfunction was their first thought, but self-tests proved no fault. The ranking officer speculated that "they" had decided on a preemptive strike, hoping to catch America unprepared. He got on the hot-line to Washington DC. With 12 minutes before Armageddon, Presi- dent Eisenhower decided: "It must be a mistake ... " For the observers, those must have been the longest 12 minutes in history. It makes me wonder about the wisdom of spending millions of dollars on a high-technology system and then ignoring it. But mankind was lucky the electronic advice was not heeded. Because - this was the discovery of moonbounce! Apparently no one had anticipated the high-power signals ripping through the atmosphere and reflecting off our satellite and then returning. The half-million mile leg with the Moon just coming over the horizon was interpreted by the system as multi-path signals from objects that were much closer. This AT&T bloke had another story less scary and much funnier. With my acquired pessimism about business, I can well imagine it to be true. Once upon a time ... no it was back in 1918, he said, and the famous Blue Bell symbol had been in use for years and years. In Dayton, Ohio, a local telephone company engineer quit to start up his own business: a telephone answering service. He chose the name Blue Bell Telephone Service. Not too surprisingly, a company lawyer called on him soon after, making dire respresentations about his usurping their name. A couple of weeks later, his work vehicle was sporting a big, wellknown logo: a cream coloured circle with a blue bell! Again, the legal person came to visit. Again, his threats were ignored. Whilst they were preparing to file a court peti- .,.s.,.;. r.:.1;~:.1;: 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. 102 SILICON CHIP tion, they received a letter from another law firm, offering them the rights to the trademark and logo. It seems that the intention had not been the deed in the early days. Neither had been properly registered with the US Patent Office. The former employee had obviously discovered this and seen it as a grand pretext to set up his business and make a quid. He'd registered both properly and sold them back to Ma Bell for a quarter of a million dollars! The FCC's revenge When I finally got to Zenith and checked into the usual hotel, I found a message waiting from my boss. He wanted me to go to a small Kentucky station first! Well, I felt like the Flying Dutchman, never getting to port. So I did the only reasonable thing. Pretending I didn't know about it, I called the main problem station and arranged to go there that afternoon. The facility was combined AM, FM & TV in one old building. They had put in perhaps the second computerised automation system in the world. And cut their engineering staff from 41 to 14 in the process. The management was as happy as Larry at the thought of the savings in wages. Before the first week had finished, they knew there was trouble right there in River City. The log was transcribed to punch tape by a girl from the traffic department. One reel of tape ran the entire facility for a whole day. No one vetted her work. The operation was contingent on all equipment being available at all times. It was possible to g3t the computer to relinquish control, but two people had to hold down pushbuttons 10 feet apart for 20 seconds. When the fertilizer impacts the air conditioning, that 20 seconds must seem like an eternity. Half the problem, maybe more, was administrative. The operators were getting loading information that varied from the master log. Even when the plan and the implementation was in agreement, it didn't take into account a VTR rolling over and dying, or broken film splices. And an open gate to air for ____ ___ ,--------------, (\ l~-'IT\JC I-<'< .,:..~1 AMATEUR RADIO ~ I Hobbyists communicating world wide using state-of-the-art electronics. ! I 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 bands? 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. a couple of minutes is pretty boring. I'd arrived on a Friday and on Sunday, in my hotel room, settled down to watch my favourite science fiction movie, "Forbidden Planet". On automated TV, of course. Well, the feature started on reel two and eventually finished. No-one was aware of it. I tried calling the channel but there was no answer. Too bad they hadn't tied the computer to the phones. That night, before the 11pm news, the network movie ended at about 10.40. After a promo for a special, with a local voice-over tag, the net logo came up, followed by nothing. Vision went to black and stayed there. Out of the darkness came some voices, somewhat muffled. The strange conversation became explicit concerning the physical attributes of the girl who did the morning exercise show. Need I say more? Suddenly, one voice said: "Hey, we're in black. What the #' + ("*/;*!! is network doing. That #&*!! computer ... why is the red light on? You don't think ... oh, my God!" Silence descended. The next morning, a little grey man in a grey suit was found wandering around the equipment room. He'd been inspecting the engineer's log. The production manager told him to leave or they'd call security. "Not necessary ", said the stranger. "Please take me to the station manager's office" . He walked in there, saying 'Tm from the FCC". They copped a $10,000 fine for the foul language and the inspector ticketed them for every tiny infraction of the regs he could find. I don't know what the final figure was but it was substantial. After six months of low wage outlay, they have decided to scrap the automation and hire warm bodies again. The management reckon they'll have to run a further three months just doing make-goods on lost commercials. I'm on my way South, Dickie. See ~, ~ 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. BOX 300 CAULFIELD SOUTH VICTORIA 3162 Registered address: 3/105 Hawthom Road Caulfield Nll1h, 3161 Please sehd aWIA information package to: NAME: ........................................................... . ADDRESS: ...................................................... : ........................................................................ I I ................................... POSTCODE ................. I 1--------------~ EO03S1 • BRISBANE'S EXPO 88 MONORAIL was very successful. In 6 months each train travelled 39,000 kilometres and provided a total of 32 million passenger journeys. Note the current busbars on the side of the box beam. THE EVOLUTION OF ELECTRIC RAILWAYS Monorails are often touted as the solution to mass transit problems but they do have considerable drawbacks. In this episode we take a close look at two new monorail systems in Australia. Many myths (mostly false) circulate in any public discussion on monorail systems. Do they really carry many people? Are they about to replace railways? Are they an asset or a liability in any citv? In the author's opinion monorails should not be compared with railways. These two types of people movers should be seen as complementary. Both are in the business of moving people. For long distance travel or commuting to outlying suburbs of a busy metropolis, no-one denies the effectiveness of high speed electric trains. For example, what other mode of transport can shift 2120 passengers at a time from Sydney's Town Hall station to Bondi Junction so quickly? But for a delightful tour of Brisbane's Expo 88 what could have been more enjoyable than to travel by any of their four monorail trains? If we must make comparisons, PT.24: AUSTRALIAN MONORAILS 104 SILICON CHIP why not pit monorails against buses; those diesel monsters that clog the city's traffic more completely than trams ever did? And pollute the air with diesel fumes! Let's look at the successes enjoyed by monorail systems in their short but popular history. Australia's first Australia's first monorail system, at Sea world .on Queensland's Gold Coast, was commissioned during August 1986. Installed at a cost of $4 million, the two monorail trains follow a 2km oval circuit around the amusement park, giving passengers an excellent elevated view of dolphins, whales and other attractions. At one point the monorail passes over the "corkscrew" roller coaster; at another, passengers are delighted by views of kilometres of coastline, yachts and blue water. The 9-car trains travel at 27km/h, stopping at two stations, one on an upper level of the Seaworld Nara Hotel. Each aluminium bodied car seats 12 passengers with provision for handicapped persons. The doors are electrically operated by the driver. Drivers are in continuous radio contact with the control station and operate from a streamlined control console in the front car. The 40-metre long trains, weighing 23 tonnes loaded, are driven by eight incredibly quiet DC motors. AC power comes from 3-phase 415VAC covered busbars mounted on the sides of the box section track. Sliding contacts on the train bogies collect this supply, one phase being grounded. On each train, thyristor bridges rectify the 3-phase AC to drive the DC traction motors. Gate trigger circuits control the thyristors for motor control and regenerative braking. The system incorporates a backup power supply. Each train runs on 20 pneumatic steel-belted radial tyres which provide traction and braking. In addition, 60 other rubber tyred wheels provide location in the horizontal and vertical dimensions. The track box section is of welded steel, 750mm wide and 600mm deep, erected in spans 24 metres long and supported on concrete columns. AUSTRALIA'S FIRST MONORAIL was at Seaworld on the Queensland Gold Coast. It is definitely a tourist attraction. What other monorail passes over a corkscrew roller coaster? The system was supplied by Von Roll Habegger of Thun, Switzerland and installed by the Gold Coast McMasters construction company. Expo monorail The popularity of monorails was confirmed by the millions of delighted visitors to Brisbane's Expo 88. Four trains each of nine cars circled the 2.3km loop track at speeds up to 24km/h. Installed at a cost of $12 million, these trains were also operated from a 415V 3-phase 50Hz supply, with on-board rectification and DC motors. The Expo monorail was installed and serviced during the six months Expo period by the Von Roll Habegger company. The reliability of the system allowed more than 32 million passenger journeys, day and night. The total downtime of the four trains was approximately 3 minutes per train over 6 months, a remarkable achievement. Expo was an example of a monorail installation adding significantly to the environment created. With nearly 18 million visitors to the site, no criticism was heard on aesthetic or other grounds against the monorail system. Rather, it was enjoyed to the full. Monorail design All Australian monorails have many common features, though size, power, voltage, suspension and other details vary in the difOCT0BER 1989 105 monorail was proposed and construction began. True, the Sydney installation was more difficult with most of the track necessarily fitted around finished buildings and overcrowded streets. This is far from the ideal of integrating the monorail into city building architecture. Though the temporary station in Pitt Street generated little applause, the mirror-faced steel pylons are an excellent step towards hiding trackwork. Credit must be given to Sydney's monorail for its clean, efficient and reasonably quiet operation. Automatic operation THIS PHOTO SHOWS A CLOSEUP view of the current collectors on the Expo 88 monorail. You can also see the rubber types which take lateral forces and those that provide downward thrust, preventing derailments. The Sydney system is designed for continuous running of 6 to 8 trains under completely automatic control. Control officers watch the operation directly and on video screens in the Darling Harbour control room. Normal train control relies on a computer system centred in Darling Harbour, with train position and speed information relayed via a fourth busbar installed throughout the system. By this means, starting and stopping at stations can be automatic, with halt times regulated by the boarding and alighting of passengers. At stations, doors open and close automatically then lock before the train departs the station. Automatic operation gives the system an average 3.5km round trip time of 12 minutes, with 6 trains capable of carrying 5000 passengers per hour. Power system THIS SPECTACULAR CURVED SPAN on the Broadbeach monorail is the largest in Australia and weighs 135 tonnes. ferent installations. The articulated cars are mounted on motor driven bogies, each bogie carrying one end of two adjoining cars. Rubber tyred wheels take the downward weight and left and right sideways thrust, with extra wheels restraining the cars against any upward movement. In principle, derailments are impossible. Power for monorail trains of this design is supplied by busbars 106 SILICON CHIP mounted on the track girder sides. Each aluminium busbar has a stainless steel facing along which the train current pickup contacts slide. Contact pressure is maintained by steel tension springs, with duplicate pickup arms for reliability. Darling Harbour Much criticism arose when Sydney's City-to-Darling Harbour Power for the Sydney monorail is derived from 1lkV 3-phase city mains, stepped down by 11kV/500V 700kVA transformers installed at 8 sites around the city. Within the nose-cone ends of the train, the 500V 3-phase supply is rectified and controlled by thyristor bridge circuits to drive the 35kW DC traction motors. A 7-car train has one traction motor driving each bogie except for the end bogies which are not powered. Thus each Sydney monorail train is driven by 6 motors. At starting each motor can deliver 75kW for a short duration to accelerate the train at a rate of 0.9m/s2, SYDNEY'S MONORAIL HAS A NOVEL arrangement whereby the Pyrmont horizontal swing bridge can swivel independently of the monorail above it, to let small boats pass through. To let larger boats pass, the bridge and the monorail swing together. The maximum speed of 35km/h is attained on the Pitt Street and Pyrmont Bridge sections. With optimum traffic control, the interval between trains can be as close as 90 seconds. In the event of a city power failure, a 400kVA diesel driven alternator at Darling Harbour provides enough power to move all trains to the stations. Pyrmont Bridge This bridge is interesting, being a rejuvenated horizontal swing bridge with the monorail track supported on a swivel pillar on the bridge central axis. To allow passage of small boats up to 15-metre mast height into inner Darling Harbour the bridge deck swings horizontally 90° on a vertical axis, leaving the monorail track above intact. In this mode trains can still cross. But to allow larger ships to pass, the bridge deck and the monorail track swing together, giving clearance for ship's masts of any height. This open-track mode is used only after all trains on the system are brought to a stop at a station, monorail track busbars isolated and the bridge track section unlocked by the system computer. Track curvature is 20-metres minimum radius, the gradients being limited to 4.4% uphill and 6.6% downhill. On test a fully laden train is required to successfully negotiate the whole track circuit in reverse. The heaviest Sydney grade occurs on the east side Pyrmont Bridge approach from the city. Certain support columns are fitted with sensors to detect any track misalignment. Dimensions Suspension Each of the mid-train cars of the Sydney monorail is 4.12m long, 2.06m wide and 2.6m high and weighs 4.5 tonnes. This short car length allows trains to negotiate sharp curves. Because of their nose cones, the end cars are longer, at 5.55m each. A complete train is 32.5m in length, weighing 31 tonnes empty. Each train is capable of seating 56 passengers and a maximum of 114 standing. The box section steel tracks are 700mm wide and 832mm deep, with a 940mm wide top flange plate. Average track span length is 30 metres on straights and 23 metres on curves. Unlike the Seaworld and Expo systems, the Sydney monorail trains are supported on air bag suspensions and pneumatic rubber tyred wheels. The wheel rims have special flat-tyre protection. In common with other Australian monorails the suspension system used in Sydney incorporates side thrust wheels. In addition, vertical restraining wheels running on the track flange underside prevent any possibility of derailment of the train. The traverser The monorail systems are designed for continuous forward operaOCT0BER 1989 107 45 tonnes, nearly three times the weight of the train which traverses it. Having crossed the river the Broadbeach monorail gains 8 metres elevation in the next two spans on a 6.5% slope. This is to give sufficient vertical height to enable it to cross both the Gold Coast Highway and the proposed Gold Coast North-South monorail tracks. The two trains each consist of four cars, the middle cars being 3.7 metres long and the complete train 21.4 metres long. It weighs 16 tonnes when empty. Power THIS PHOTO SHOWS THE HEAVY braced construction of a box beam for a monorail. MONORAIL POINTS ARE LARGE, expensive and cumbersome. This assembly rotates to change tracks. tion around the loop track, without points, track crossovers or direction reversal. However every system must allow for train maintenance. The storage and maintenance yard is at Ultimo on the Sydney system. It consists of a horizontal traverser feeding parallel yard tracks, each capable of accommodating a complete train. The traverser itself is a short section of the main line which can be moved sideways, carrying one whole stationary train with it. Sideways movement brings the traverser track in line with one of four parallel storage/maintenance tracks onto which the train is driven. Meanwhile, a second traverser track section moves to fill in the gap in the main line to allow other trains to continue operating. Comprehensive interlocks safeguard 108 SILICON CHIP running trains while traversing manoeuvres are proceeding. Broadbeach monorail Australia's newest monorail, in operation since August 1989, connects Jupiter's Casino, Conrad Hotel, Pan Pacific Hotel/Oasis shopping plaza and Broadbeach. Situated on Queensland's Gold Coast, this monorail crosses the Gold Coast Highway and a tributary of the Nerang River. Some of the track spans in this river crossing are fine examples of engineering. One span in particular is unique. From Jupiter's station the track immediately crosses the river on a 52-metre span girder which turns through 135° before the next support column. This, the heaviest span on the system, consists of a box girder 940mm wide at the top and 1.6m deep. This girder weighs Because of the heavy facing grades, the 4-car trains are equipped with five 35kW traction motors, one in every bogie. Under normal conditions only four of these motors are used, the leading bogie motor idling unpowered. The four motors, each exerting 75-B0kW for a short time, are capable of full acceleration (0.9m/s2) up the 6.5 % grade with a fully loaded train. The power supplied from the track mounted busbars is 500V 3-phase, with one phase grounded. The current pickup, thyristor bridges and control systems are similar to those used in Sydney, however the Broadbeach trains each carry a driver. Another difference is the emergency power arrangement. To cope with a mains power failure, a large diesel driven alternator starts up within the Oasis/Pan Pacific complex, giving the monorail emergency supply. But should this supply also fail the monorail train driver starts up a diesel-alternator carried in the nosecone of the leading car. This provides lights for the train as well as power to the normally unpowered bogie motor. The architectural design of the Broadbeach monorail, like the Expo system, is a model for monorails everywhere. At the Broadbeach Pan Pacific Hotel, the monorail train, tracks and station are fully integrated into the building design rather than being an add-on. The North-South monorail Soon to come is the Gold Coast SYDNEY'S MONORAIL HAS SOME quite steep slopes. This section is near the old Paddy's Markets. The beauty of a monorail is that it takes very little space, does not pollute and makes little noise. THIS IS THE SYDNEY MONORAIL traverser at the Ultimo storage yard. It looks quite different from a conventional railway shunting yard doesn't it? North-South monorail system. At present in the design stage, this extensive monorail system will connect Southport, Seaworld, Surfers Paradise, Broadbeach, Pacific Fair and suburbs in between. With a total track length of about 24km and a mainline junction near Main Beach, this will be the largest monorail system in Australia when completed. It will cost about $200 million, with construction to begin about the end of 1990 and scheduled for completion by 1993. Monorail points Will monorails eventually take over the role of railways? Probably not but they do have advantages in that they do not take up anywhere near as much space or cost as much to build as conventional light railways. Until now though, they have been mainly used as a tourist attraction and usually operate fairly slowly. One big problem inhibiting the monorail concept mushrooming into complex systems (as railways have) is the difficult construction of track points. Regular railway tracks were conceived to allow easy switching of trains from one track to another as well as providing for diamond and multiple track intersections. Facing points in some cases can be negotiated at 125km/h. Trailing points can be designed for safe runthrough from the wrong track. To date none of these facilities have been incorporated into monorail systems. Though it is difficult to conceive how they could be implemented, we would be foolish indeed to say they 'never' could! Who knows what the future will bring concerning this interesting mode of transportation. Acknowledgements Our thanks to Seaworld and Von Roll Habegger companies and their engineers for photos, information and permission to publish. ~ OCT0BER1989 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. More thoughts on engine monitoring I have some comments on engine monitoring systems. I recall seeing a device on a GM (now Detroit) Diesel engine. This was a temperature probe with a water jacket inserted in the exhaust. A bleed from the water pump kept it cool. It was part of a shut down system for unattended engines. For automotive use it could be used in conjunction with a VDO low water alarm which gives an audio/visual warning. Additional connections for temperature, oil pressure/level and over revving can be made. I would question the advisability of using such a system to cut the ignition, as suggested by A.G. in the August 1989 issue. This could give rise to a life threatening situation. Congratulations on your magazine - it's tops! (J.U., Charbon, NSW]. Building a hifi FM transmitter I am a violinist in the "Outback Bush Band" and have tried several FM transmitter circuits without much success. I (and several colleagues) would be very interested in a good quality Tx/Rx (transmitter/receiver] combo or Tx (for an FM radio) project. The main specs would be crystal frequency control, high impedance input , tange greater than 90 metres, frequency response from lO0Hz. to at least 16kHz, good dynamic range ()90dB), good signal to noise ratio and low distortion. How viable would such a project be at say around $160? (G.H., Kotara South, NSW). • You may be interested to know that your requirements are far better than the very best commercial FM stereo transmitters. Their quoted signal/noise ratio (and therefore dynamic range) is rarely much better than 70dB and their audio frequency response is limited to 15kHz. Even the very best commercial FM stereo tuners (such as the Sony ST-S444ESX) are flat out achieving a signal/noise ratio of better than 90dB and that is never achieved "off air" but only under laboratory test conditions. With these facts in mind, we'd be brilliant to achieve your requirements for only $160. Now if you'd said $1600, there might be a chance. However, we don't think that this quantum improvement in FM specs is required if you want a good quali- Stub filters for the CB band II In the May 1989 issue of SILICON CHIP, Garry Cratt wrote about the subject of TVI (television interference) at great length but only in regards to the amateur radio band. As I am an avid CBer, I was wondering if it would be possible to give me some advice for making a stub filter to suit 27MHz. Also, in November last year, I asked if it would be possible for SILICON CHIP to publish a circuit for a capacitance meter that 110 SILICON CHIP could drive an analog multimeter. I'm sure that there must be many others who would appreciate such a handy addition to their workbench. (M.B., Loganlea, Qld). • It's quite an easy matter to adapt the stub filter described in May to the 27MHz band. All you have to do is multiply the stub lengths by 5.4. We'll have a look at publishing a circuit for a capacitance meter to drive an analog multimeter. ty wireless microphone (or instrument pickup ). One of the real problems of wireless microphones is that they tend to have fading problems or signal dropout as the performer moves around the stage. This effect is almost impossible to avoid with any low powered transmitter in a confined space. The solution is to go to a diversity tuner which will do a great deal to cancel out signal fading. Diversity tuners actually employ two tuner front ends and a microprocessor controlled switching circuit to continually choose the best received signal. Since each tuner front end is fed from a separate antenna, so that you have two antennas spaced some distance apart, one of the tuner front ends should always be getting a good signal. As far as we know, there is only one readily available diversity tuner to suit your needs and that is the Redford wireless microphone system which is available from Altronics in Perth. All up cost of a single wireless microphone and the diversity receiver is just over $1000. Pools/Lotto selector kit is available Where can I get the kit for the Pools/Lotto Selector described in the May 1989 issue of SILICON CHIP and for how much? I'm 12 years old and getting right into electronics. When I'm older I would love to be an electronics engineer. (D.B., Chapman, ACT). • The Pools/Lotto Selector is available from all Dick Smith Electronics stores at $59.50. We like your ambition, D.B. Go for it. Light at the end of the tunnel I need help. I require a tunnel diode for a project but I can't find anyone that sells them. Could you Notes & Errata Touch Lamp Dimmer, June 1989: As noted in the article, the revised version of the SLB0586 does not require diodes D1 and D2 but they will not affect circuit operation if they are left in. However, now that the revised chip has been released, as SLB0586A, it has been found not to work in the circuit as published. To make it work, two components must be changed. The 680k0 resistor must be swapped for a 0.33µF capacitor while the .0022µF capacitor should be swapped for a 1ookn resistor. These components will fit without any modifications to the PCB pattern being required. If your kit has the original SLB0586 IC, no circuit changes are necessary. Studio Series 32-Band 1/3 Oct- ave Equaliser, March, April 1989: one of the four 220µF electrolytic capacitors shown on the main equaliser in the wiring diagram (Fig.1(b} on page 48 of the April issue} is reversed in polarity. The capacitor in question is connected to pin 4 of IC2. Ultrasonic Car Burglar Alarm, July 1989: the wiring diagram on page 63 shows one side of the siren connected to chassis. It should connect to + 12V, as shown on the circuit on page 61. Garbage Reminder, August 1989: the .047 µF supply bypass capacitor shown between IC6 and IC7 on the wiring diagram of page 50 is shown as 0.1µF on the circuit of page 49. The value is not critical though and either 0.lµF or .047µF is OK. Advertising Index Allied Capacitors .... .... .. .... .... 65 Altronics ...... .. ...... .. ....... 46-49 Arista Electronics ............. .. .. 1 7 Banksia Information Tech ...... 89 Board Solutions .. .... .. ... .......... 9 Dauner Electronics .. .. .. .. . .. ... 1 3 David Reid Electronics ..... 56,57 Dick Smith Electronics ..... 68-73 Electronic Solutions .. ..... . 14, 15 Elmeasco .... ..... .. .. ..... .... .. OBC Geoff Wood Electronics ..... .. IFC Harbuch Electronics .. ... .. ... .. . 94 Hycal Instruments .. .... .. .. ...... 13 Jaycar Electronics .. .. .. .... 36-39 80-83 J.V. Tuners .. ... ............. .. ..... 94 Kepic .... ... .. .... ... .. ........ .. .... . 95 Novocastrian Electronics .... .. 1 9 PC Marketplace ....... .. ..... ..... 31 Pelham .. .. .. .................... .. . 112 Power-Sonic Corp .... .... ..... . IBC Philips Test & Measurement .. 89 RCS Radio ... .... .. ...... .. .. .. ... 102 Rod Irving Electronics .. ... 96,97 WIA .. .. .. .. .... .. .... ............... 103 tell me where I can get one? SILICON CHIP is a great magazine. I like the Vintage Radio section and the Serviceman's Log. What happened to the Technology Letters? (A.R., St George, Qld}. • Tunnel diodes have become very rare. In the 1960s they were regarded as the wonder diode but very largely they look to have been a solution looking for a problem. Their special claim to fame is that they have a "negative resistance" characteristic which enables them to be used as amplifiers or oscillators right up to microwave frequencies. Now, most of the applications for tunnel diodes appear to be fulfilled by more conventional devices such as microwave transistors and Gunn diodes. General Electric was at one time the major manufacturer of tunnel diodes but this is no longer the case. However, we have been in contact with the agents for General Electric, GEC Components, and they have indicated that they may be able to source tunnel diodes, depending on the type number and quantity required. If you want to make further enquiries, you can contact GEC Components by phone on (02} 887 6222 or by fax on (02} 805 0272. Remote Control ctd from page 8 secure and military designers are constantly searching for better ones. Some of the more complex included frequency hopping, chopped chirp, exotic encoding and above all else, making the vehicle as intelligent as possible, so that it can perform its task with as little outside assistance as possible. All of this and more will be discussed in columns to come. There'll be simple explanations covering the installation of the equipment into models, care and feeding of nicads, and the correct use of servo arms, plus the exotic. It should be a lot of fun. See you next month. ~ The Way I See It ctd from page 90 ly turned up in disposals stores for 50c each or three for a dollar! "As far as I could see, the only thing the power transformer did was to operate the pilot light. A single wire ran to the nest of pots and another to the circuit board, 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, being soldered, of all things, to the piece of PCB foil spelling out the manufacturer's part number! "What does a friend do in this situation? Does one protest that the $300 miracle healing machine is just a con and refuse to proceed any further with the farce? "Knowing the lady as I did, I replaced the crunched diodes with three new ones and assured her that they were a close equivalent to the originals. And of course, as soon as she turned it on, she noticed the difference!" K.W. observes that "thousands of electronic enthusiasts have pulled apart discarded computer boards. How many can claim that they've actually repaired one?" ~ OCT0BER1989 111 CEN'l 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 SEP ARA TEL Y, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7 .00) 16 ($740) 17 ($7.80) 18 ($820) 19 ($860) 20 ($9 00) Street .................. .. ..... ... . Postcode Enclosed is my cneque or money order for $ Bankcard D Visa Card D MasterCard . ... .......... .. . ... . or please debit my D Card No I I Signature.. . BUILD YOUR OWN LED Moving Message board. $75 for a 4-character display experimenter's short form kit and $1 50 for 16 characters. Kit consists of PC boards, EPROM and full instructions to complete the project to a professional standard. Loaded from Centronics printer port or PC/XT keyboard. Equivalent commercial units start at around $1 000. For more info send a 39c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. SATFAX: 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. 112 SILICON CHIP 4 x 256 1Mb 1Mb - 150ns 120ns 100ns 100ns ?Ons ?Ons 100ns 100ns 80ns 9 X 100 9 X 100 9 X 80 8 X 10 0 8 X 100 Description XTs ATs 12MHz Nee 20MHz Compaq 20 pin Price ex tax $4.25 $4.80 $5.20 $5.60 $7.80 $9.00 $17.80 $17.00 $17 .80 Simm LP $210.00 Simm HP $180.00 Fast Simm LP $230.00 Mac Simm LP $198 .00 Mac 2 HP $172.00 PELHAM Tel (02) 427 0011 Fax (02) 428 5460 Secure your future! Develop your communication skills and enhance your employment opportunities. How? Invest in the world famous SMI training kit and you too can join the hundreds of success stories . Telephone (02) 891 1282 today for more details . .. Card expiry date ..... . ./. . .... ./. FAX THIS COUPON WITH YOUR CREDIT CARD DETAILS TO (02) 982 9553 FOR SALE Prices at September 8th, 1989 Type 256 TECHNICIANS Name ... .... ... ... ........ ........... .. ... ... .... .... ..... ... ...... ... .... . Suburb/Town MEMORY CHIPS RADFAX2: HF weather fax, Morse & RTTY receiving program for IBM 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 Michael Delahunty, 42 Villiers St, New Farm, Old 4005. Phone (07) 358 2785. ACTIVE TRANSMISSION line stereo speakers. Includes preamp. $760.00. Send SAE to 36 Palmer St, Nambucca Heads, NSW 2448 . RESISTORS, 1 % METAL film, 0 .6 watt. Finest German quality, 7c each, $6 per hundred, any mixed values. SAE for free sample & data sheet. Also BUX80 $7, 2N3055 $2.35, BC547 12c, 2N3019 $1.20, HEF4050B 80c, 1 0nF greencap 20c, 1 00nF monolithic 1 5c, 220nF 630 volt polycarbonate $2. P&P NSW $2 .50, interstate $3 .50 . Extended Pulse Burn Electronic Ignition: full kit $70, fully built and tested $99 postpaid. Chipspeed Electronics, PO Box 337, Wentworthville, NSW 2145 . AM/FM STEREO TUNER, EA kit 1986, professionally built. FM partially working, AM needs alignment and a coil. Documentation supplied. $250. Peter Wolf (02) 898 6269; AH (02) 597 1707. WANTED WANTED: MANUAL for APF Mark 90 calculator. Phone 069 25422 or send to 29 Gormly Avenue, Wagga Wagga, NSW 2650. 4 REASONS TO CHOOSE POWER-SONIC BATIERIES PERFORMANCE RELIABILITY Bold claims are made by battery manufacturers old and new claiming one "breakthrough" or another. The fact is, only time will tell the true quality of a product. POWER-SONIC has been building sealed rechargeable batteries for over 20 years and its state-of-the-art design and unmatched track record for dependable performance have earned it the confidence of engineers and buyers the world over. You can rely on POWER-SONIC sealed rechargeable lead-acid and nickel-cadmium batteries in the toughest environment - be it extended power outages, high or low ambient temperatures, months of storage, or years of service. POWER-SONIC batteries are designed to power your equipment when needed. You can depend on it and so can your customer. AVAILABILITY VALUE POWER-SONIC batteries may not always be the lowest priced on the market, but you get what you paid for trouble-free service for years, enhancing the reputation of your product or installation. Success is measured by the bottom line, not short-sighted savings gained at the expense of high quality components. A full line of standard sizes is available along with a few unique but well conceived special designs. This extensive array of models, recognized by U.L.'s component program, puts design and sourcing flexibility at your fingertips. Fully stocked warehouses allow off-the-shelf shipments and guarantee on-time deliveries. ,om.ER;$~ s DNI' e//l/l/l/lll//ll///llllllll/l/llll/l// /IIII//////I/I/I//Q///ll////////l/llliffffu111111'!!i POWER-SONIC CORPORATION Vic: 9/260 Wickham Road, Moorabin, Victoria 3189 Tel: (03) 553 4195. Fax: (03) 553 4917 NSW: Unit 5/60 Fairford Rd., Padstow, 2211 Tel: (02) 790-4444 Fax (02) 790-0246