Rs. 7.50 Sensitive light meter The battle for supertelevision Indoor unit for satellite TV recepjtiojj-2' VASAVI’s VLCR7 SAVES YOU FROM AGONY OF BRIDGES. Measurement of INDUCTANCE, CAPACITANCE, RESISTANCE are greatly simplified by VLCR 7. No balancing, no adjustments. VLCR 7 gives you directly the digital reading of value and its loss factor simultaneously. VLCR 7 is the only instrument in India covering the widest ranges of 0.1 pf/uH/m ohm lie. 0.0001 ohm) to 20,000 uf/200H/20 M ohm. Component tester in our oscilloscopes is altogether different from other’s. In addition to all Oscilloscope funtions component tester provision can test all components passive and active, in circuit and out of circuit. ONLY OUR SCOPESCAN recognise NPN/PNP. Distinguish HIGH/LOWGain, Distinguish AUDIO, R.F., SWITCHING transistors. > DIGITAL FREQUENCY COUNTER VDC 1 8 Smallest size ever made in INDIA Battery cum mains operated wide frequency range 30MHz (our model VDC 19 is Basic sensitivity of lOmv Bright LED display 7 digit MULTI FUNCTION OSCILLATOR r\jJ~LA/ * Pure Sine wave output. * Amplitude settable with ease down to millivolts. X 1, X 1/10 and X 1/100 attenuated outputs available. * No amplitude bounce when frequency varied. VASAVI ELECTRONICS (Marketing division) 630, Alkarim Trade Centre, Ranigunj SECUNDERABAD-500 003. ph: 70995 gms: VELSCOPE Dear friends, Way back in 1974, someone gave me issue No 5 of Elektor Magazine as a gift. I found it to be so interesting and fascinating that I placed an order with the publishers in England for all available back issues along with an annual subscription of the same. Since then, I became an avid reader and collector of this superb magazine. Gradually, my fiercely guarded pile of Elektor Magazines grew up to great proportions. Later on, I switched over to the Indian edition as it was cheaper compared to the UK edition though the contents lagged behind by a month which really did not matter. Lately, I discovered that no one had posted any issues of Elektor Magazine prior to the year 1990. I therefore found myself in a unique position to fill the gap and to help collectors of this magazine by scanning and posting my vintage collection on the internet. I toyed with the idea for a very long time until my enthusiasm overcame my laziness. I went out and bought a portable scanner just for this purpose. I have scanned and posted over 125 issues from my vintage collection over the last few months. At 65, with bad eyes and poor health my enthusiasm is wearing out. I, therefore, seek your pardon for the long intervals between my postings. I have been informed that sadly, someone is trying to sell my scanned vintage issues of Elektor magazines on e-Bay. I was sure that sooner or later someone would try to make money out my efforts. However, it does not make me angry but it certainly make me sad. For me it has been purely a labour of love without any commercial value whatsoever. I wish it had remained free for all to share as intended. Alas, greed takes out all the fun from sharing. I thank all of you for the great encouragement in my venture . A Merry Christmas & A Very Happy New Year to all of you. if vouar eabuddha@amai 1 .com December 13, 2010 SAVE ON AMPLIFIERS H elektor india decamber 1986 1 2 "03 Publisher: C.R. Chandarana Editor: Surendra Iyer Editorial Assistance: Ashok Dongre General Manager: J. Dhas Advertising: B.M. Mehta Production: C N Mithagan Address. ELEKTOR ELECTRONICS PVT. LTD. 52. C Proctor Road Bombay - 400 007 INDIA Telex: (011) 76661 ELEK IN Overseas editions: Elektor Electronics Standfast House Bath Place High Street, Barnet Herts EN5 5XE U K. Editor: Len Seymour Publitron Publicacoes Tecnicas Ltda Av Ipiranga 1100, 9° andar CEP 01040 Sao Paulo — Brazil Editor: Juliano Barsali Elektor sari Route Nationale; Le Seau; B.P. 53 59270 Bailleul — France Editors: D R S Meyer; G C P Raedersdorf Elektor Verlag GmbH Susterfeld-StralJe 25 100 Aachen — West Germany Editor: E J A Krempelsauer Elektor EPE Karaiskaki 14 t 16673 Voula — Athens - Greece Editor: E Xanthoulis Elektuur B.V. Peter Treckpoelstraat 2-4 6191 VK Beek — the Netherlands Editor: PEL Kersemake Ferreira & Berito Lda. R.D. Estefania, 32-1° 1000 Lisboa - Portugal Editor: Jorge Goncalves Ingelek S.A. Av. Alfonso XIII, 141 Madrid 16 — Spain Editor: A M Ferrer In part: Kedhorn Holdings PTY Li Cnr c ox Valley Road & Kiogle Street Wahroonga NSW 2076 - Australia Editor: Roger Harrison Electronic Press AB Box 63 182 11 Da.ideryd — Sweden Editor: Bill Cedrum The Circuits are for domestic use only. The submission of designs of articles of Elektor India implies permission to the publishers to alter and translate the text and designand to use the contents in other Elektor publications and activities. The publishers cannot guarantee to return any material submitted to them. All drawings, photographs, printed cirucit boards and articles published in Elektor India are copyright and may not be reproduced or imitated in whole or part without prior written permission of the publishers. Patent protection may exist in respect of circuits, devices, components etc. described in this magazine. The publishers do not accept responsibility for failing to identify such patent or other protection. Distributors: Blaze Publishers & Distributors Pvt. Ltd Printed At: Trupti Offset Bombay 400 013 Ph 4923261. 4921354 Copyright © 1 986 Elektuur B.V. The Netherlands Volume-4 Number 12 December - 1 986 Electronics technology Actuation system for flight control 12.26 Sound sampling and digital synthesis 12.36 The battle for supertelevision 12.44 Tell-tale magnetism of heart-throbs 12.47 Projects Top-of-the-range preamplifier - Part-1 12.19 Indoor unit for Satellite TV reception-part-2 12.28 Sensitive light meter 12.41 RF circuit design 12.50 Information News and views 12.15 New products 12.60 Licences & letters of intent 12.66 Switch board 12.71 Guide lines Classified ads Index of advertisers Selex-18 Relays 12.52 Wire movement in a magnetic field 12.54 Bicycle dynamo 12.57 NOTE: Computerscope-2 will be featured in one of our forthcoming issue and not in this issue as mentioned earlier. SEND COLOURFUL GREETINGS TO YOUR FRIENDS. Simply detach the card in this issue, write your message, affix appropriate stamps and mail them. 12.74 12.74 elektor mdia december 1986 12-05 Range of ‘TV’ speakers COLOR T V. SPEAKERS 8*13 LCI 3/5 10x15LCT6-D 10 LOT 3 10 LOT 5 9 LOT 3 9x5.5 LWCT2 C0NTEC/T0SHIBA GRUNDIG/PHILLIPS SON Y/SHARP/J.VC. -Do- CONTEC/J.V.C. TOSHIBA/CORE TEWEETER Teweeters And Flat Cone Woofers □ Manufactured by Cl Distributors for Maharashtra. LUXCO Electronics Gujarat and South India: Allahabad— 211 003 □ Sole Selling Agents: LUXMI & CO. 56. Johnstonganj Allahabad -211 003. Phone. 54041, Telex 540-286 □ Distributors for Delhi & Haryana: Railton Electronics Radio Place. ChandniChowk Delhi-110 006 Phone 239944. 23318/. sound technology from a sound source precious Electronics Corporation • Chotani Building. 52. Proctor Road Grant Road (East). Bombay-400 007 Phones: 367459. 369478 • 9 Atmpattan Street. Mount Road. Madras— 600 002. Phone: 842718. Get your international conference to take off with the right man behind you. Air-India’s Congresses & Conventions team. They work as one man to see your conference successfully through. By offering all their advice— absolutely free! They work with you right from inception by helping you promote your conference. Advising you how to bid for India as your conference venue. Liaising with your delegates. And transporting them to India on a wide range of low, low group and individual fares. Of course, they’re backed by Air-India’s worldwide network of 145 offices. So that your conference gets all the publicity and promotion it needs. And by Delhi’s superb conference venues. Like the Talkatora Stadium or the Indira Gandhi Stadium. Or, the many new hotels in Delhi, most of which offer excellent conference facilities. Or even the ultra-modem Sher-i-Kashmir International Conference Centre at Srinagar. Attached to the superb 5-star Centaur Lake View Hotel next to Dal Lake. Naturally, with such services, it’s no surprise that Air-India has been closely involved with the 12th International Leprosy Congress, the World Energy Conference, the World Mining Congress and many more. The next time you want to host an international conference, make sure you have the right sort of backing. Get in touch with: Air-India Congresses & Conventions 6th Floor, ‘Vandhana’ 11, Tolstoy Marg NEW DELHI-110 001 Tel: 3311225 Cable: AIRINDIA You host it. We’ll help promote it. Member International Congress & Convention Association etehtor India decembor 1986 1 2-09 J.M. ENTERPRISES 382 LAJPAT RAI MARKET DELHI-110 006 PH-235455,238919 •lektor india december 1986 1 2-1 3 TOP-OF-THE- RANGE PRE- AMPLIFIER-Part 1 The accent throughout the design of this preamplifier has been on quality and the avoidance of unnecessary features, such as tone control and remote operation, tt is not cheap to build: probably around £ 200 -£ 250 , but then, a commercial preamplifier of comparable quality is at least twice as expensive. Hi-fi is probably the most misused term in the audio and music world. Properly used in connection with sound reproduction equipment it means that the equipment can pro- duce sounds that are as nearly as possible a faithful reproduction of the original, and at a level that offers the listener almost the same ampli- tude as he would have obtained from the original source. The limitations of most sound reproduction equipment and the general acoustics of the room in which the equipment operates prevent these conditions being satisfied in virtually all cases. Not much can generally be done about the room acoustics, but the equipment can be made as nearly perfect as modem technology allows. Fortunately for the constructor, com- ponents get better all the time, and our knowledge of audio engineering progresses steadily. Today, there is a tremendous variety of sound repro- duction equipment on the market at a price ratio of, perhaps, as high as 1:30. As far as the design of this equipment is concerned, it can be divided into roughly two categories: (1) that with an imposing appearance and a row of controls that is almost entirely dependent on price, and (2) that in which above all the quality of the reproduced sound has been considered. There are, of course, many variants in each of these categories, but the broad division is very pertinent. Music lovers and audiophiles, by definition, are only interested in category 2 equipment, Fig. 1. Block diagram of the preamplifier. phono amplilier 15 iQ{>i balance volume TUNER Qo- CD [)o- AUX 0o- TAPEOUT $ O- T APE IN QO— tape / source svelch -o» r — i — t- :x i power supply relay control 1 i i elektor indi a december 1986 12-19 because they know that it pays to in- vest in high-quality sound process- ing rather than in a range of interesting, but stricly unnecessary, facilities, such as complex tone con- trols and remote operation. After all, audio equipment is all about reproducing music to as faithful an original quality as possible. As stated, category 2 can be sub- divided into a number of variants. The remarkable observation that can be made here is that there is a cer- tain connection between the price and the number of operating con- trols. As the quality and, sub- sequently, the price rise, the number of controls decreases. This is not always strictly true, but there is a definite trend. At the top, there is equipment de- signed by and for purists from which anything that has no direct bearing on the sound quality has been omit- ted. Such equipment is geared to the utmost perfection of the reproduced sound. Often, the preamplifiers of this kind of equipment have only an on-off switch, input selector, and volume control. The preamplifiier proposed here belongs to this class of equipment, although it has three more controls than mentioned: mono-stereo; tape-source; and balance. Basic layout The block diagram in Fig. 1 shows the layout of the preamplifier. Each of the three sections in dashed lines is located on a separate printed- circuit board. That at the top is the preamplifier proper, which is, of course, a stereo set-up, although only one channel has been shown. The section underneath it is the busboard which contains the input and output connectors, the various selectors, and associated parts. The third board contains the power supply, with the exception of the mains transformer which is mounted in a separate box, and the relay con- trol circuits. The relay control circuits enable selection of various modes of oper- ation to be made as close as possible to the relevant input. The preamplifier is almost entirely DC-coupled: where this proved diffi- cult or impossible, high-quality polypropylene capacitors are used, which obviate the usual drawbacks of capacitor coupling. The charac- te’ristics of these capacitors and of the special semiconductors used will be discussed in detail in next month's continuation of this article. The preamplifier proper consists of two parts: a phono amplifier that can be fed from either an MC (moving- Fig. 2 The IEC recommended recording and playback characteristics. Fig. 3. Input and relay circuits. f (Hz) 86111-2 1 2~20 etaklor ind»a dacembw 1986 coil) or an MD (magneto-dynamic) cartridge, and a line amplifier with inputs for TUNER, CD (compact disc), AUX, and TAPE. The phono section is rather special, because it is not the usual combination of MD preamplifier and MC pre- preamplifier, but a single stage whose amplification can be set to suit both MC and MD cartridges. The input stage of the phono ampli- fier offers the facility of terminating the pick-up cartridge used into the correct capacitance and resistance: an indispensable feature in this class of amplifier. The voltage gain,. Av, of the second stage can be arranged not only to ac- commodate either an MC or an MD element, but also— in. two steps— to suit the output voltage of these elements. The active off-set correc- tion— AOC— stage ensures that the off-set voltage at the output of the linear amplifier remains negligible i small at all times without the need of 1 any adjustments. The final stage in this section pro- vides the necessary de-emphasis for record reproduction. The de- emphasis characteristic is within 0.1 dB of the relevant requirements of the IEC (International Elec- trotechnical Commission); the corre- sponding pre-emphasis character- istic— see Fig. 2— has been adopted by all major broadcasting organiz- ations, virtually the whole of the re- cording industry in the western i Fig. 4 The busboard. Parts list (Fig. 41 Note. Starting with the preamplifier, parts lists will in future be pub lished in full accordance with BS 1852; hitherto, these lists deviated from that standard-in some respects. See infocard opposite inside back cover. Resistors (all metal film): R37;R37-;R4t;R4i';R43; R 43 =2K21F R38;R38';R42;R42;R44; R44 =48K7F R39,R39- - tOKOF R40;R40- - 10K2F R4S,R45' = 4K75F R46;R46 = 475KF Capacitors: C33;C34;C35;C36;C37; C 39 - lOOnM ceramic Semiconductors: Dt;D2;D3;D4,D5; De= 1N4148 Relays: ReA;ReB;Rec;Reo;Ret; Ref - sub miniature PCB mounting relay two-pole change-over; 12 V* Miscellaneous: Kt = 10 way PCB mounted socket' ' 16 screened phone chassis sockets with mating plugs' ' 'Available from Electromail • P 0 Box 33 • Corby • Northants NN17 9EL • Telephone: 105361 204555 ' 'Available from Verospeed • Standsted Road • Boyatt Wood • Eastleigh • Hants S05 4ZY •Telephone: (07031 644555 elefclor indie decomber 19B6 12-21 Fig. 5. The relay control circuits. world, and such organizations as the AES (Audio Engineering Society), the RIAA (Record Industry Associ- ation of America), and the NARTB (National Association of Radio and Television Broadcasters). The linear line amplifier contains the volume as well as the balance con- trol, and also the stereo-mono selec- tion facility. Busboord The busboard contains not only all input and output connectors and relays, but also the voltage dividers required for level matching. Its cir- cuit diagram is shown in Fig. 3. At the left are all the inputs, and at the right all the outputs. The relays (with associated capacitors and free- wheeling diodes) take care of all the switching. Since a compact disc player pro- vides a much higher output voltage than, say, a tuner or a tape recorder, the CD input is attenuated by voltage divider R39-R40 (R39-R40). The volt- age dividers on the other inputs serve merely to reduce near-end crosstalk even further and are, strictly speaking, not necessary. In- puts not in use are taken to ground via resistors Rm, R40, R42, and R44 (R 38 \ R40', R42', and R44 ). The relays are. controlled from the relay control section on the power supply board. The busboard— see Fig. 4— has been designed in a way that facilitates its direct mounting onto (screened) phono sockets. The relays are miniature PCB types which must be of the best quality to ensure that no unnecessary resistances are introduced in the (low-level) signal paths. It is rec- ommended to use phono connectors and relays with gold-plated contacts if at all possible. Relay control The relays on the busboard are con- trolled by a number of driver stages on the supply board, which have been designed to ensure virtually noiseless switching operation. The 1 2-22 otoktof india docambni 1986 circuit diagram of the relay control section is shown in Fig. 5 . When the supply is first switched on, the output relay is energized after a slight delay; when the supply is switched off, however, the output relay is deactivated immediately. Source selection When either the input selector or the tape-monitor switch is operated, the output relay is de-energized before the relevant change is effected, and reactuated only after the new input or tape position has been selected. The non-used contacts of the source selector, Sr, are logic high via resistors Rre to R19 inch, while the selected input contact is logic low via the switch wiper. The switching arrangement is passed on to inputs Ao to A3 of comparator ICe, where it is compared (nibble) with the situ- ation at pins Bo to Bx Because of the time delay introduced by R25-C30; R26-C31; R27-C32; and R26-C33 respect- ively, the two compared nibbles will differ by a few microseconds. This will cause the output (pin 6) of IC 6 momentarily to go low when S2 is turned. This negative pulse triggers monostables MMV. and MMV2, which introduce delays of 0.5 s and 1 s respectively. If both are triggered simultaneously, the selected input and the line out relay, ReF, are disconnected instantaneously by Ni, N2, N3, or N* and N18-N19-N20-N10-N15 respectively. After the delay caused by MMVi has lapsed, the newly selected input is connected, and after the delay caused by MMV2 has lapsed, the line out relay is re- energized. Tape monitor When tape monitor switch S3 is closed, a positive pulse is generated with the aid of Ns, delay network R29-C29, and XOR gate N22-N23-N2.1- N25. This pulse triggers MMV2 so that line out relay ReF is deactuated. After a delay R21-C24, tape monitor relay ReE is energized. The line out relay is re-energized when the delay introduced by MMV2 has lapsed. It is important to note that during the above operation the input relays re- main energized, and the connection with tape out is not broken. Power on The line out relay is energized after a delay R24-C27. This time constant is just a little longer than the time re- quired by the power supply to attain full output. Diode Du ensures a rapid discharge of C27 when the power is switched off. Power failure The secondary voltage of the mains transformer is rectified by Du and D16 and smoothed to some extent by C2S. It is then roughly halved by voltage divider R32-R33 to provide a suitable input (<12 V) to pin 1 of Nro. Diode D13 affords protection against noise peaks. Because of the very short time constant Rj 2 -R 3 j-C 28 (about 20 ms), the line out relay is de- energized the instant the power is switched off or fails. Fig. 6a. Power supply for the audio section. Fig. 6b. Power supply for the relays and relay control circuits. Power supply The power supply is rather more ex- tensive than is usual with this type of equipment: this is because of the re- quirement for different voltages for the audio sections, the relays, and the relay control. The supply for the audio section- see Fig. 6a— provides a symmetrical voltage of + 18.5 V. Everything feas- ible has been done to reduce hum and other noise to a minimum, and the circuit therefore contains com- ponents not often found in power supplies. The mains transformer should have eleklor mdia decomber 1986 1 2-23 two secondary windings, each pro- viding 18 V at 1 A. The ILP Type 11014 is perfect. The transformer is not housed in the preamplifier en- closure but in a separate box; this is again to reduce hum in the preampli- fier to an absolute minimum. The mains on-off switch, Si, is de- bounced by C? and C»; noise peaks on the mains are shorted to ground by Cs and C 6 . Resistors Ri to R< in series with rec- tifiers Di to Di limit current peaks at switch-on. Capacitors Ci to C« effec- tively suppress the internal noise of the rectifiers. Reservoir capacitors C 9 and C 10 are shunted by foil capacitors Cn and C 12 to improve the suppression of RF noise. Stabilization of the + 18 V lines is ef- fected by IC» and IC9. The action of these regulators is enhanced by tran- sistors Ti and T 2 , which act as vari- able zener diodes; presets Pi and P 2 enable the output voltage to be set to the precise level. Fig. 7. Printed- circuit board for the power sup- plies and relay control circuits . Note. Starting with the pre- amplifier. parts lists will in future be published in full accordance with BS 1852; hitherto, these lists deviated from that stan- dard in some respects. See in- focard opposite inside back cover. Parts list (Fig. 71 Resistors: Ri;R2|R3;R. = 1R8 Rs;R2i;R22;R23;R2«~ 1M0 Re = 2K7 Rr=1K5 R 2 - 220R Rs = 120R Rio;Rh;R 32;R33 = 47K Ri2;Ri3 = 10R Rh = 680R Ris = 47R Ri6;Ri7;Rib;Ri9;R2o;R25; R2s;R27;R29;R29 = 10K R3o:R3i = 1K0 Pi;P 2 = 1K preset Capacitors: Ci;C2;C3,C4 = 22n; 250 V; MKT Cs;Ce = 10n; 250 V; MKT Cr;C« = 47n: 250 V; MKT C9;Cio = 4700p; 40 V; electrolytic Cn;Ci 2 = lOOn Ci3;Ci4=4 M 7, 25 V; electrolytic Cis;Ci« = 4700p; 25 V; electrolytic C 12 = 1000p;40 V; electrolytic C.»= 10 h: t6 V; electrolytic Ci9 = 100m; 16 V; electrolytic C2o;C2i;C22;C23;C34 = 22n ’ 12-24 elektor incSa docembor 1 986 Networks R12-C15 and Ru-Cis are low-pass filters with a very low cut-off frequency which ensure the virtually complete elimination of any noise from the supply lines. The supply for the relays and the relay control circuits— see Fig. 6b— is fairly simple. The output voltage of regulator IC 10 is increased some- 7 what by connecting the ground pin to earth via diode Du. This LED also functions as the on-off indicator. Zener diode Du is a safety pre- caution that ensures correct oper- ation if for some reason the LED breaks down. The printed-circuit board for the power supply and the relay control circuits is shown in Fig. 7. Note that voltage regulators ICe, IC9, and IC10 must be mounted on a suitable heat sink. This article will be continued in our January 1987 issue. (see Tables 2a & 2b in Satellite TV reception, Elektor India, October 1986) by adding a 25 Hz component to the up- link CVBS signal. The triangular wave has a fixed phase relation to the 50 Hz field sync-pulse and causes the received picture to flicker if it is not removed by filtering. The previously mentioned period has been dimensioned to do just that, and the result is a stable picture from all transponders employing dispersal. A simple T-filter composed of C 46 , Ln and Cj? suppresses baseband signals below some 5 MHz (fc = l/[2iq 2LCJ) and at the same time pro- vides some matching to the base of the oscillator transistors in IC 4 . The up-converted 10.7 MHz IF signal is next coupled out via Lis and band transformer Lu. IC4 has been configured to offer op- timum performance of the contained symmetrical mixer. The S042P also has an on-chip oscillator which can be tuned over 16-20 MHz in the pro- posed design. Tuning is ac- complished by applying an adjust- able (Pz) voltage to varactor D 7 , which, together with Lis-Cso-Csi, forms the external tuned circuit for the oscillator transistors in IC4. The up-convened 10.7 MHz IF signal is next coupled out via Lis and passed through a matched ceramic filter providing a bandwidth of about 280 kHz. ICs is the well-known Type TBA120S quadrature FM detector connected in a conventional arrangement which includes de-emphasis capacitor C67. The AF output signal is buffered by Ki, and the output volume may be set as required by P3. The S-meter driver is basically an in- verting voltage-to-current converter; the lower the direct voltage at the base of T 10 , the more current will flow through the meter coil, whose Fig. 10. Block diagram of the second board in the indoor tuner. Although this shows quite a number of stages, relatively few of these do the necessary work. The CCIR Comitd Con- sultant International de Radio' forms part of the International Telecommunications Union-nxj, which is a UN Specialized Agency with headquarters at the Place des Nations, Geneva. Through the CCIR, the ITU sets up international regulations for radio and TV ser- vices; allocates the radio frequency spectrum and registeis all radio fre- quency assignments. It also studies, recom- mends, collects, and publishes information on all telecommunication matters, including space radio and TV communi- cations. ' In English: Inter- national Radio Con- sultative Committee. •lefctor india decambar 1986 1 2-29 All values are typical and within 10%. All voltages measured with respect to ground with a DMM IZm 1 MQ). Fig. 11. Circuit diagram of the vision and sound processing stages. S-meter driver, and the combined power supply /LNB theft alarm. The dots at certain con- nections of Lis denote the start- ing points of coupled windings. sensitivity can be accommodated by setting shunt preset Ps. Pa determines the stabilized emitter voltage of Tio and thereby the threshold below which the voltage at the S input must fall for minimum vis- ible meter deflection. Any type of small, rectangular mov- ing coil meter will work fine in this circuit, provided the fsd current lies in the 100 \nh — 1 mA range. As the indication is merely relative, the meter need not have a specific scale division. The power supply for the indoor tuner is of conventional design incor- porating an LNB alarm relay driver, Tn, and a voltage doubler section C73-D10-D1 1-C74 which provides the raw input for 33 V stabilizer D12. Some care should be taken in the dimensioning of Rsi, as the temperature-compensated zener- diode should not dissipate too much power in the case of a fairly high transformer secondary voltage, Urn. The value of Rsi is calculated from R51 ®>( 2 .SUtii— 0 . 6 — Uz)/L [Q] where Uz and Iz are the zener voltage and current respectively. The stated value of R 51 gives a zener current of about 13 mA with a loaded transformer output of 18 V rms. Ob- viously the resulting dissipation of about 430 mW requires the T018 case of D 12 to be fitted with a small heatsink. I Constructors should note that the ! Type TAA5S0 has a production toler- ! ance of 10%; therefore its zener voltage may lie between about 30 \ and 36 V. kmaxi of the device is stated as 20 mA by its manufacturer, SGS. Experiments have shown that the Type ZTK33 can also be used for D 12 , provided R 51 is redimensioned for Iztmax) of 7 mA. The LNB alarm relay is de-energized, and its contacts are opened, when the voltage across current sense re- sistor R 53 drops below about 0.7 V, as is the case when the LNB is discon- nected. The relay contacts will also open when the downlead cable is short-circuited, e.g. by cutting, as F 2 blows which de-energizes the relay coil. The relay contacts may be wired to an existing alarm circuit. Finally, shown inset are the fine & coarse tuning controls and polariz- ation selector S3, which is -shown unconnected as there is, at present, a wide variety of methods for the remote selection of linear (H/V) or circular (cw/ccw) polarization. Any constructor is therefore left free to make his own control circuit to go with the specific system configur- ation (steerable polarizer, coax-relay, remote-controlled ortho-mode feed, etc.). Construction As compared with last’s month’s con- structional intricacies, life is more or less back to normal with the present board. In fact, with component over- 12-30 elektor india decembet 1 9 lay and track layout Fig. 13 to hand no problems are envisaged. The voltage regulators may be mounted either on the enclosure rear panel or on the bottom lid, whichever you think more con- venient. Especially in the case of the 7812, adequate cooling is called for, and this should be duly observed if you insist on leaving the regulator on the board, where it can be expected to get very hot if it is only fitted with a TO220-style heatsink. The wire leading to the regulator input may conveniently be replaced by an empirically determined 5 W resistor, Rx- (10-20 Q). Rsi and Rs 3 are mounted slightly off the board, and D 12 must be fitted with a smallish heat-sink. Beware of shortcircuits as the cooling fins are at ground potential. All terminal holes on the PCB edges should be fitted with soldering pins (quite a few are required. . .). Ready-made inductors Lis and Lu should not cause problems, as their positions are governed by the rel- evant PCB holes. Sockets may be used in all IC positions. Refer to Table 2 for data on home- wound inductors Lis and Lis. The former is readily made, the latter re- quires a bit of constructional de- tailing, as it is critical in regard of the correct phase relationship between the three windings, whose starting points have been indicated as dots in the circuit diagram. Refer to Fig. 14 to see how the Type 10 K 1 former has its base modified to create an additional "pin”. If you are less familiar with winding inductors of this size, practise scraping off all enamel coating over a length of some S mm at the wire end without breaking it. Next, pre-tin it, scrape lightly again and check for a smooth surface. The wire end thus prepared should be revolved around the rel- evant base pin (use pliers) and joined to it direct where this is seated in the ABS material, soldering rapidly to prevent damaging the base. And now for L15. 1. Cut off a strip of 30 x S mm Sello- tape and put this somewhere within easy reach. 2. Wind f ' — e, starting with f at the base of the former, winding 25 closewound turns upwards. Deter- mine the length of wire to connect to pin e; prepare the end as stated but do not actually make the connection yet. Instead, leave the wire end fly- ing as you press the f ' — e winding into place to make a closewound coil. Next, fix the winding with the strip of Sellotape, still leaving the e end unconnected. 3. Starting from b ' connect and close-wind the wire 12 turns up- ward, onto f — e; the exact location is irrelevant. Connect to a. 4. Starting from d ' (the wire end functions as a pin) wind four turns straight into the centre of b — a. Connect to c. 5. Connect the flying top wire end to e. 6 . Check for any short-circuits be- tween windings and verify correct continuity at the pins. 7. The windings may be secured with a few drops of wax or Araldite. 8 . Put the inductor assembly together and double-check its PCB position before fitting. Do not yet mount the screening can. Check the completed board in the usual manner before wiring the re- ceiver as shown in Fig. 15. Do not fit the units in the enclosure yet, con- nect all controls in a provisional man- ner only, and hook up an ammeter to take the function of Mi while testing the S-meter driver. Alignment Apart from the standard tools and measuring equipment available in most workshops, you need the fol- lowing items for setting up the in- door tuner; — A CVBS-input colour monitor or a suitable VHF/UHF vision modu- lator; — an AF amplifier; — a simple to control, preferably manually tuned, monochrome or colour TV set. Make a simple UHF pick-up device by plugging in a short length of coaxial cable, the open end of which is fitted with a 10 cm long probe wire; — a nylon trim tool set; — an LNB connected to Ki by a short length of low-loss coax cable. It is, of course, even better to have it fitted and fully operative onto the dish, which should preferably be pointed at ECS-1 (vertical polarization). Once this is all done, the downlead cable should be connected to Ki. Handy, but not strictly necessary to achieve good results, are a grid dip oscillator (GDO), an oscilloscope, and a 1.2 GHz frequency meter. After switching on, check all measurement values given in Figs. 2 and 11. If necessary, correct R 4 and Re to achieve correct biasing of T 2 and Ts, respectively. Commence the alignment pro- cedure by concentrating on the sec- ond board. Pre- and de-emphasis is a technique used to im- prove the signal-to-noise ratio in a radio com munication system that employs frequency modulation IFM) or phase modulation (PM) . At the transmitter side the modulating signal is passed through a net- work that causes the higher frequencies to be less attenuated than the lower ones. At the re- ceiver the reverse pro- cess (de-emphasis) is used to restore the original relative strengths of the modulating fre- quencies. In the case of satellite TV reception, the trans- mitter is in fact the uplink centre, and the receiver is the indoor unit (note that satellite TV transponders merely convert and re-transmit the received uplink power; no modulation correction of any kind takes place, therefore). Fig. 12. Pre - emphasis (I) and de-emphasis (II) characteristics to CCIR recommen- dation 405-1, which is ap- plicable to most, if not all, 12 GHz transponders currently or- biting the earth. The dashed curve represents the response of a prototype ver- sion of the de- emphasis filter incorporated in the present design. fllofctor indix december 1986 1 2-31 Fig. 13. Track pattern and com- ponent overlay of the single- sided second board in the IDU. Parts list Resistors: R 22 ; Ras; R 24 ; R 2 S; R 29 ; Rsi = 75 Q 1% R 2 $ = 300 Q 1% R 27 = 20 Q 1% R 2 $ = 6k8 Rjo;R 3 2 = 470 Q Rjj = 8k2 Rj 4 = 1k5 Rjs = 180 Q R36;R< 2 ;R4«= 1 k R 3 t = 10 k R3«;R 52 = 680 Q R3*;Rs4 = 330 Q R4 0 = 4k7 R4i = 100 Q R 43 ,R 4 # -2k2 R44 = 220 Q R4j = 18 k R4*;R47;R5o = 22 k Rsi = 1 k % W * Rm = 10 Q % W Pi;Pa= 10 k preset P 2 ;Pe = 10 k linear potentiometer P 4 = 5 k preset Ps = 2k5 preset P 7 = 100 k linear stereo potentiometer Capacitors: C46,C47;Cei = 22 p C&o = 22 p * C 48 = 4n7 polystyrene 5% C<9 = 680 p polystyrene 5% Cso;C54;Css;C6» = 100 m ;16 V Csi;C7o - 100 n Sibatit Cs 2 = 10 m;16 V C53 = 100 n MKT C36;C6 2 ;C66 = 10 n ceramic C»7;Cs8;C9»;C7i = 1 n ceramic C63;C64;C&7 = 22 n ceramic Cm = 47 m;16 V Cm = 4^7; 16 V C7 2 = 2200 m; 40 V C73.C74 = 220 j<;63 V C75 = 10 m;63 V C7$;C77 = 10 n',25 V * See text. All electrolytic capacitors are axial types. Specified working voltage is minimum. Semiconductors: Te = BF199 T7;Ta = BC547B T«;Tto;Tit = BC557B Ds = 6V2 zener 0.4 W De;Dn * 1N4148 Dr = BB405G 1. Set Pa and Ps to the centre of their travel, and connect the CVBS monitor to K2. 2. Check whether the voltage across D? can be varied from 0-12 V, and subsequently peak Lie and Li? for maximum AF noise output. The core in Lie should be adjusted until its top just protrudes from the former. 3. Set P7 to produce 10 V at Vmne; select LOl. 4. Tune the TV set to UHF channel 36 or 37 (600 MHz, roughly) and care- fully locate the probe wire close to the VCO inductor, Le. Adjust C27 until the screen is observed to go black for an instant, indicating the recep- tion of the VCO carrier. As soon as this happens, C27 should be left alone and the TV set is tuned over a few adjacent channels to locate the carrier. The initial adjustment for C27 should be reached with the trim- mer’s rotor plates at about one third of their travel. If you use a frequency meter, simply adjust C27 for a reading of 610 MHz (use inductive coupling). Set the wiper of Pi to point at ICs (% of its travel). 5. The four bandfilter trimmers should now be peaked for maxi- mum noise on the CVBS monitor. The indoor tuner only produces out- put video noise with an LNB connec- ted to Ku The point where maximum noise is observed should be reached with all bandfilter trimmers set to about 40% of their travel; this is a good way of checking the correct functioning of the four line inductors. Any trimmer with a widely deviating setting is in- dicative of wrong adjustment and/or a circuit malfunction. Output noise should be stable and free of tearing and horizontal lines. If necessary, correct the setting of Pi to preclude overdriving the monitor (a scope should measure about 3 V PP at the CVBS-1 output). Spend some time in adjusting the trimmers, as their set- tings interact slightly due to the critical coupling between the associ- ated line inductors. From the next step onwards it is as- sumed that a stable, relatively strong (C/N =2 10 dB) downlead signal is fed to Ki. A suggested dish positioning method will be given in part 3 of this series. 6. Turn P7 to check whether LOl has any undesirable dips in its output band. The dips are visible as a decrease in output noise, owing to j the BFW 92 switching to another i mode of oscillation; the effect can be mode of oscillation; the effect can be ruled out quite effectively by care- fully pressing Cx towards the PCB. Over the entire tuning range, how- ever, the occurence of two or three of such dips is quite normal; but these should, of course, not coincide with satellite signals, as in that case reception of a specific transponder may be considerably impaired ow- ing to lack of oscillator power. 7 . Set Vmne to about 3 .S V and care- fully press down Cx (LOl) until a TV signal is observed to swish past; this is most likely Teleclub Switzerland (ECS-1, 7WV). Do not alter the position of Cx anymore; in- stead, tune P?-Pe until the picture is at least stable. Now realign the bandfilters, observ- ing that the optimum trimmer set- tings do not differ dramatically from those obtained by peaking for maxi- mum noise. Again, take the inductor interaction into account as you peak for optimum definion of the test chart Table 2 Home-wound inductors inductor winding SWG wire turns . remarks Ln a-b 24 enam. 14 closewound on T50-2 core c-d 24 enam. 5 (red & green; O.D. = 12.7 mm) Lis f-e 36 enam. 25 all closewound on Neosid b-a 36 enam. 12 dia. 4 mm former Type d-c 36 enam. 4 10K1; see Fig. 14. 1 2~32 elektor irtdia d«cember 1986 15 on the screen. Realign Pi, if necessary. Tune across the LOl band to observe the other transpon- ders, which should be receivable with equal signal strength, exept RTL-plus, which is beamed down on the satellite’s east spot. LOl should tune right up to SAT-1. 8. To get the most out of the indoor tuner, it may be worthwhile to carry out some experiments with slightly different settings of C27, as the VCO output power is far from be- ing stable over the 550-650 MHz range. Therefore, try a few ad- justments of C27, correct the tuning to capture the signal again, and realign the bandfilter trimmers for best reception (note that the requisite cor- rections should be very small). With a 10 dB C/N input signal fed to the tuner, reception should be clear and virtually free of sparklies. 9. Tune to SAT-1 (LOh, ECS-1 10WV), and set P 2 to the centre of its travel. Carefully adjust the core in Lis until the main audio channel is heard. Peak Li 7 for undistorted audio at maximum amplitude. SAT-1 transmits two more audio programmes: the VOA (Voice of America) and ever- present background music; both, however, at reduced power and bandwidth with respect to the main subcarrier. This fact makes the background music channel emi- nently suited for the fine adjustment of Lie. If correctly aligned, the tuner will output this channel with virtually no noise, given the previously stated C/N value. Europa TV (ECS-1, 3WH), like no other transponder, demonstrates the quality of the proposed sound pro- cessing method; all five subcarriers carrying simultaneous translations of the daily broadcast news bulletin can be received by simply tuning P 2 . 10 . In case you are unable to receive any audio programme, check the os- cillator frequency of IC« by means of a GDO or a frequency meter connec- ted capacjtively to pin 10 or 12. A scope is also usable, provided its bandwidth is adequate. Ceo deter- mines the centre frequency of 18 MHz, while Cd determines the tuning range, which should be a minimum 4 MHz to cover the full sub- carrier band. 11 . Finally, adjust Pi and Ps for an am- meter indication corresponding to the fsd current of Mi when reception is optimum. The meter should also indicate the relative strength of spot- east transponders RTL+ (8EV) and 3-SAT (2EH), i.e. P 4 and Ps should be set to produce any, rather than no meter deflection at all, while the higher PFD channels still produce full scale deflection on Mi. The ad- justment of Pi is quite critical in this respect, and care should be taken to avoid overloading the meter coil. 12. Assuming that ECS-1 is still being received with vertical polarization, Cx’ in LOh should be bent down as far as possible without losing Music Box from the tuning dial. It is per- fectly possible that either LOl or LOh covers the full LO injection band. However, in that case there are likely to be rather more dips, jeop- ardizing reception of some of the transponders. The enclosure Not much needs to be said about the fitting of the tuner into the stated enclosure, but a few details require attention. Ki should protrude from a 15 mm hole in the rear panel; the socket flange should rest against the panel inside, while the bottom lid of the RF unit is secured onto the utmost left of the enclosure bottom lid. In this way, the RF unit is readily removable. Note, however, that the foregoing set- up may require all eight mounting D#;D«;Dio;Dn = 1N4002 Di2 = TAA550 * Du = panel-mount LED ICi = NE592 (SGS-Ates) IC« = S042P (Siemens! ICs = TBA120S ICs = CA3240E 1C; = 7812 or 7812CV v ICa = 7815 or 7815CV^ * See text. t Preferred type in view of higher permissible output current (1.5 A). Inductors: Li 2 = 33 mH axial choke Li3 = 22 uH axial choke Lu = T50-2 core * Lis = 10K 1 assembly * (Neosid! Lie = KACSK3893A (Toko) Li7 = KACSK586HM (Toko! * See text for winding details. Miscellaneous: CFi = CFSH10.7M1 (Toko! Fi =200 mA slow F 2 = 250 mA slow K 2 = flange-type BNC socket Kj= 5-way DIN socket Mi = 200 fiA fsd rectangular S -meter, e.g. Cirkit 900 series.* Rei = 24 V OIL type, e.g. Hamlin HE721A5025 S 2 = miniature SPST Si = miniature SPDT TR1 =2x 18 V; 1 A Panel-mount fuseholder PCB mount fuseholder Heat-sinks for D 12 , IC; and ICs.* PCB Type 86082-2 Front panel foil Type 86082 F Enclosure Retex Type Ecobox 7610 dmhof- Bedco Standard Prod acts Ltd, Uxbridge. Telephone: (0895) 37123) Size of the box is 300 x 200 x 70 mm. 'See text. Fig. 15. Wiring diagram of the indoor tuner. For' reasons of clar- ity. the two boards are shown further apart than they are in actual practice. elekior india decembwr 1986 1 2-33 Fig. 14. Inductor Li 5 is the main part of the tuned tank circuit, of a symmetrically- ended oscillator contained in /CV All windings should be made bottom to top of the former, and in counterclock- wise direction as shown. Fig. 16. The front panel of the tuner makes for a neat appear- ance in the living room. The foil for it is available through our READERS SER- VICES (see p. 78). Since suitable rec- tangular S- meters come in a variety of sizes, the relevant aperture should be made only when the dimen- sions of the meter are known. Fig 1 7 Further in the photographs published on P. 29 in our October issue here are some more showing test cards re- ceived from ECS-1 brackets in the Ecobox to be re- moved. The second board must be mounted on 5 mm spacers, right next to the RF unit, leaving ample space at the right for the power transformer and fuseholder for Fi . Drilling the front panel should not cause problems, as the front panel foil for this project may serve as the template (see Fig. 16). Note that the MODE selector is part of the optional circuitry to be de- tailed in Part 3; for now, a 2-pole, 3-way rotary switch plus knob may already be mounted. Next time The third and final article in this series will be published in the j February 1987 issue of Elektor India. Details will be presented of a final, optional board, to be mounted on top of the one you have just com- pleted. It holds an AFC circuit, a VHF vision & sound remodulator plus video test source, and a scanner circuit to sweep across the receiver frequency range to facilitate dish positioning. Also, the measurement data, prom- ised last month but too bulky for in- 1 2-34 elektor india decembef 1986 elusion in the present instalment, will be discussed in some detail. RGK;Bu Corrigenda to part 1 (Elektor India, November 1986) 1. Please correct the following tex- tual errors: p. 56: . . that a 1.2 m and 1.8 m dish aerial..'.' should read "...that a I . 2 m to 1.8 m dish aerial. . '.'. p. 57: . .to give an output of 10.95- II. 75GHz" should read "...to give an output of 950-1750 MHz'.' Component availability All semiconductors for the board described in this article are available from Universal Semiconductor Devices; 17 Granville Court, Granville Road, Hornsey, London. Telephone 01-348 9420/9425; telex 25157 usco g. A kit comprising all parts for the RF section detailed in part 1 will shortly be available from Piper Communications; 4 Severn Road; Chilton- Didcot; Ox- on 0X11 OPW. Telephone: (0235) 834328. Neosid inductor assemblies are available from Neosid; Eduard House; Brownfields; Welwyn Garden City; Hertfordshire AL7 IAN. Telephone: (0707) 325011; telex: 25423. 86082-2 IDU for satellite TV reception Hot ICs - no need for fear It is perfectly normal for ICs particularly bipolar digital ICs such as TTL, to become very warm in operation. These ICs draw considerable power which is finally dissipated as heat. An example is the common TTL 1C 74145, Typical dissipation for this device is 215 mW and approximately 360mW maximum; this is in the quiescent state with unloaded outputs. When these are loaded the dissipation is even higher Since the area of the 1C package is relatively small, the 1C becomes very warm indeed. This is no problem, however; it is rated appropriately and operates perfectly even at ambient temperatures of upto 70°C. When the computer is installed in a housing, care should be taken to provide ventilation slots for the heat to dissipate In the event of doubt regarding the temperature rise of ICs, the data sheet should be consulted; an 1C with a maximum dissipation of 10 mW for instance, should not exhibit noticeable temperature rise. The Microcomputer as a source of interference Every microcomputer system operates with relatively fast logic ICs. such as Schottky TTLs. This means that the digital signals have rapid-rise slopes which produce harmonics extending far into the VHF/UHF region. This cause interference, and not only to FM stereo reception. The problem is not restricted to home made microcomputers; some commercially built microcomputers, particularly teaching and experimental system, can unfortunately be classed as sources of electro- magnetic pollution. The only solution is to install the mcrocomputer in a (metal) screened housing with an earth connection; it may also be necessary to fit a mains RF- suppression filter. Scree ned (coaxial) cable should be used for connections between the computer and peripheral equipment. These precautions apply to all digital equipment using fast logic. elektor india december 1986 1 2 “35 SOUND SAMPLING AND DIGITAL SYNTHESIS by D Doepfer & C Assail Nowadays, phrases such as sound sampling and digital synthesis crop up more and more often when "insiders” are talking about electronic music or eiectrophonic instruments Although on the face of it these two concepts have little in common, this is a false impression as the following article shows A sound sampler Is in- tended to be fed with a random range of sounds, process this if required, and output it as a series of discrete tones. Chang- ing the frequency of the tones is normally effected by means of a keyboard, so that a sound sampler can be played like any other keyboard instrument. Operation The AF output signal of a microphone, tape recorder, or record player is stored and then reproduced. To this end, the signal is transformed into a series of (binary) digits in an analogue-to- digital converter (ADC), after which the digits are stored in a digital random-access memory (RAM) or read-only memory (ROM). The converter is not able to scan the entire audio frequency range of 20 Hz to 20 kHz continuously. In- stead, it samples the signal at regular, defined intervals of time, and only these samples are con- verted and stored. Research has shown that a band of signals must be sampled at a frequency of 12-36 elekior india decembar 1986 not less than twice the highest frequency occur- ing in the band to prevent loss of information. For the present purposes, the upper audio fre- quency will be taken as 16 kHz, which means that the sampling rate must not be less than 32 kHz. Lower sampling fre- quencies would result in aliasing: the alias signal has a frequency that cor- responds to an harmonic of the sampled signal. Since the bandwidth of the incoming AF signal varies according to the signal source, the input of a sound sampler is in- variably provided with an anti-aliasing (low-pass) filter as shown in Fig. 1. The cut-off frequency of this filter must not be greater than half the sam- pling rate. It may be vari- able as, for instance, in an integrated voltage- controlled filter (VCF), so that a variable sample rate can be used. Sam- pling rates greater than 32 kHz result in improved sound quality (because of the greater scanned bandwidth), but, since more digits then have to be stored during the same time interval, mean that the memory must have a correspondingly larger ca- pacity. Because the level ot the input signal to the ADC must not change during the conversion process (since useless binary digits would result), a sample- and-hold (S&H) circuit is in- troduced between the ADC and the filter. This cir- cuit derives a sample from ♦he AF signal at fixed fime intervalr. (every 31.25 ms at a sample rate of 32 kHz) and holds the level of fhis sample sfeady at its out- put until the next sample is taken. Basically, a sample-and-hold circuit consists of a switch, a ca- pacitor, and a buffer- amplifier. When fhe switch is closed, the output of the circuit follows the input; when it is open, the last voltage level at the output is retained. The switch is an electronic type such as a field-effect transistor (FET) or CMOS switch. Sample- and-hold circuits are also available as integrated units. The conversion of the analogue signal into a digital code must be com- pleted within a slightly shorter time than 31.25 ^s (at a sample rate of 32 kHz), because the S&H circuit also needs a finite time to come into oper- ation. At the same time, no distortions must be in- troduced that would im- pair the final sound qualify! The resolution (in bits=binary digits) of the ADC stands in direct re- lation to the signal-to- noise (S/N) ratio and the dynamic range. The dynamic range is the range over which the ADC can produce a suitable output signal in response to an input signal. It is often quoted as the differ- ence in decibels between the noise level of the device and the level at which the ADC is saturated (i.e. the overload level). In practice, good resol- ution is taken as 1 bit for a dynamic range of 6 dB: ♦hat is, an 8-bit resolution gives a range of 48 dB; 10-bit=60 dB; 12-bit=72 dB; and 16-bit=96 dB. The choice of resolution is largely a matter of cost: on purely technical con- siderations, 16-bit resol- ution is, of course, preferable to 10-bit, but unfortunately good-quality 16-bit ADCs cost around Fig. I. Block diagram of a typical sound sampler. £300. Furthermore, 16-bit resolution would put heavy demands on the S&H circuit as well as on the tilter, and this would further increase costs. Fi- nally, 16-bit resolution re- quires double the storage capacity of that for 8-bit resolution. Fortunately, 8-bit resolution is perfectly satisfactory for mosf applications, but it requires optimum use of the dynamic range. Prob- lems are only likely to arise with signals that cover a large range, for instance, those that have a large peak value at the onset and a very small one at the end. The quan- tization distortion will be quite audible at the end of such signals. This prob- lem can be cured by higher resolution, e.g. 12-bit, or by an inexpens- ive compander. A com- pander is a combination of compressor and ex- pander. A compressor automatically reduces the range of amplitude vari- ations of an AF signal at the input of a system, whereas an expander automatically extends the range of amplitude vari- ations at the output of the system. An 8-bit system with a suitable com- pander yields results that are comparable to those of a 12-bit system. The bit stream at the out- put of the ADC is stored serially in a digital sound 1 memory. The capacity of this memory for a sound of 1 s duration, 8-bit resol- ution, and 32 kHz sam- pling rate must be 32 Kbyte [1 Kbyte=1024 (2'°) bytes]. The run-off control for writing the data into the memory can be ef- fected by means of the software of a microproces- sor system. This software (in machine language) must be fast enough to read the output of the ADC, write the value into the memory, and increase the memory address (high/low byte) by 1 every 31.25 ^s. Even simple 8-bit pro- cessors with an 8-bit index register are suitable for this. Writing may be started manually (pressing a key or pushbutton), or auto- matically as soon as the AF signal exceeds a given threshold level. Manual starting is normally used when from a range of sounds only a particular band needs to be sampled. Automatic start- ing is preferred for the sampling of the sound from individual instru- ments. When the memory is full, writing is stopped, and the sound is available as a series of 32x2'° bytes. This series can be further pro- cessed with the aid of customer-made software and/or transferred to a main store such as a floppy disk. To reproduce the stored digital code as an analogue sound, the bits are converted in a digital- to-analogue converter (DAC) at the output. The timing rate resulting from the reconversion process determines the cut-off fre- quency of the (low-pass) re-assembling filter that follows the DAC. Since the timing frequency varies with the frequency of the reproduced signal, it is im- portant that the cut-off fre- quency is in tandem with the clock. The re- assembling filter should, therefore, preferably be an integrated, voltage- controlled type, for in- stance, the CEM3320. If the data are read from the memory at the same speed as they were writ- ten, the output signal is a replica of that at the in- put. If, however, the reading speed is varied, the frequency of the out- put signal is altered. If the reading speed is con- trolled from a keyboard, it is thus possible to play back the original signal at a different pitch. The run-off control for reading the data from the memory may be provided by a computer or specially designed hard- ware. This hardware is basically a binary counter the clock of which is fed by a signal whose fre- quency is determined by whichever key on the keyboard is pressed. Traditional systems operating with the 1 V/oc- tave standard contain a fast voltage-controlled os- cillator (VCO) that converts the voltage from the keyboard into the requisite frequency. The control voltage is also supplied to the frequency-control in- put of the re-assembling filter, so that the filter operates in tandem with the play-back sampling rate. A gating pulse, also provided by the keyboard, starts the actual play-back. In digital systems operating in accordance with the MIDI standard, the MIDI data are obtained from a suitable peripheral device, such as the 6850. The MIDI data are con- verted by a computer into a suitable signal to drive a high-speed oscillator whose output is used to read the memory. If the computer is fitted with a fast processor, such as the 68000, a programmable counter, for instance an 8254, may be used in- stead of the high-speed oscillator, in conjunction with suitable customer- designed software. The memory is then not read with a variable frequency, but at a fixed sample rate with variable increment. In this manner, the output signal will deviate from the input according to the increments. Unfortunately, slefclor indiB decwmber 1986 1 2 37 2 loop phase II H ii this mode of operation causes other problems, such as digital aliasing, which can not be dis- cussed here. Every time a key is pressed, the sound starts afresh, irrespective of whether the previous sound has finished or not. To enable stationary sounds to be generated, loops have been provided in the roll-oft control cir- cuit. The sound can then be divided into three phases as shown in Fig. 2: the build-up phase; the stationary or loop phase; and the decay phase. When a key is pressed, the sound builds up (as, for in- stance, when a violin string is bowed); then re- mains stationary (like the sound from the violin after it has been bowed) as long as the key is pressed; and finally decays when the key is released. The instants at which the standing phase begins and ends are under the control of the musician, although a computer can be a very useful tool here, as when, for instance, it is predetermined that only zero crossing of the signal will be used as starting and finishing points. The loop must be a whole multiple of the period of the signal to avoid annoy- ing clicks at the change- over points. Determining the loop is normally quite straightfor- ward with monophonic (from Greek for "single sound’! instruments. Gen- erally, the loop will em- brace at least a couple of periods, as this will make the sound rather livelier. Occasionally, beats, fre- quency fluctuations, and other spurious effects may cause a dimunition of the liveliness; a chorus, phasing, flanging, or delay unit connected at the output may improve matters again. If the input signal has already been processed with a periodic effect, such as vibrato (=slow fre- quency modulation); tremolo (=slow amplitude modulation); phasing; or flanging, the effects fre- 12-38 elekior india dacembar 1 986 quency must be taken into account in the loop, other- wise the effect would be lost in the standing phase, although it is present in the two other phases. With polyphonic (from Greek "simultaneous sounding of different notes”) inputs, such as from a choir or orchestra, determining a properly working loop is at best difficult and often im- possible. The difficulty revolves around finding two change-over points that are suitable for all in- struments contributing to the polyphonic sound. It is often possible to arrive at a compromise by taking a very wide loop (up to 100 periods) and negating the ensuing slight distortion by using a chorus unit or delay line at the output. The crucial information of most instru- ments is contained in the build-up phase, so that the storage allocation for the standing phase can be kept relatively small. The signal output by the DAC may undergo further analogue processes. It is, for instance, possible to modify the high-frequency content with the aid of a voltage-controlled filter (VCF) and a wave-form (envelope) generator, or the loudness level with a voltage-controlled ampli- fier (VCA) and a wave-form generator. Independent of such further analogue pro- cesses, the signal may also be digitally modified by a computer while still stored in the memory. In conjunction with a graphics display on the monitor, the sound can be partially erased, shifted, duplicated, or inverted (backwards). Inversion of percussive sounds particu- larly leads to interesting structures. The signal may be given a completely new ampli- tude envelope and be displayed graphically in different forms. If the com- puter is sufficiently power- ful, the sound may also be subject to Fourier analysis, and after appropriate modification be syn- thesized anew. As already stated, the computer is also a power- ful tool in the determi- nation of the loop start and finish. If, for instance, it has a mass storage device, such as a floppy disk, sounds and associ- ated loop values can be stored Indefinitely, which makes it possible to build up a complete sound library. Musicians can in- terchange all kinds of sound, while manufac- 3 Sample 1 Sample 2 Sample 3 1 \ 1 n 111 86065-3 Fig. 2. Division of the sampled sound into three phases: the (central) stand- ing, or stationary phase is shown with extended time axis in 2b. Fig. 3. Typical keyboard . for use in multi-sampling. turers can produce and market standard sounds on chips. Making the output signal faster or slower than the input signal gives rise to the so-called Mickey Mouse effect, because the sound becomes more and more unnatural the farther the output speed is from the input speed. The effect is caused by a shift in the resonance frequency or formant structure when the output pitch is changed by varying the reading speed. Each instrument has its own distinct vari- ation of the effect: the less pronounced its formants are, the less noticeable the effect is. The effect is kept in check by multi- sampling, in which in dif- ferent tone ranges (e.g. each octave) several sounds are sampled (see Fig. 3). During playback, only the input sound nearest in frequency to the required output tone is used. In extreme cases, each semitone is stored at its own address. Since this requires an enormous memory capacity, such extremes are not (yet) en- countered in practice. A not insignificant prob- lem with multi-sampling is the proper matching of the various frequency ranges (as, for instance, equal loudness level) so that the transition from one range to another is not noticeable. There is another, not so well-known, method of multi-sampling, which does not depend on the selection of different fre- quencies, but on the dynamics of the iristru- ment. A lightly struck piano key causes a differ- ent sound than when it is struck hard; the same is true for virtually all instru- ments. It is, therefore, poss- ible to use different memories for different degrees of touch. During playback, it depends on the dynamics of the key, or on the MIDI information as to the dynamics, which memory will be read. Un- fortunately, this method of multi-sampling requires very expensive equipment and is, therefore, hardly found in commercially available equipment. Sound samplers are available as monophonic or polyphonic instruments. Monophonic models can generate only one sound at a time, whereas polyphonic types produce several sounds simul- taneously. The latter are sub-divided into models with one common memory for all sounds, and models that have a memory for each different register. In the latter, each register can produce its own distinct sound, which, in conjunction with multi- register sequences, has, of course, fhe greaf advan- tage that each register can be used with a differ- ent instrument (MIDI mono mode possible). Polyphonic equipment with only one sound memory generates the same sound for each register, but can, simul- taneously, do so at differ- ent pitch. Digital synthesis It has been seen that dur- ing the recording of a sound a series of data, representing that sound, is stored in a memory. Any computing technique by which a series of signifi- cant data could be created in the memory without sampling would afford pure synthetic sounds. In principle, there are many methods by which random series of data can be produced, but for the purposes here the series must be musically acceptable, clearly arranged, and, moreover, there should be a simple relation between the recording character- istics and the sound out- put. These requirements reduce the available techiques to: • Fourier synthesis (also called harmonic syn- thesis); • frequency-modulation (FM) synthesis; • waveshaping synthesis; • phase distortion syn- thesis. Since the tones are available in digital code, it is possible to manipulate them in all possible variations. It is, for example, possible to play back a digital sound backwards, or to mix, combine, or modulate it with a second tone. Other effects, including doub- ling; echo; reverberation; flanging; chorus; harmon- izing; ring modulation; im- posing on a new envel- ope; and fast Fourier transform with subsequent re-synthesis are possible with the aid of suitable software. It is noteworthy that all these effects can be realized with hardly any extension of the hard- ware. Manipulation of natural sounds, extending beyond mere sampling and stor- ing, belongs to a new technique of sound gener- ation: digital sound sythesis. In its pure form, it obviates the need for an analogue input unit. In this technique, a waveform is produced direct by a computer system that is controlled by a math- ematical algorithm. The tone is determined by the method which, in the truest sense of the word, synthesizes a waveform. The main difficulty here is to describe the waveform as precisely as possible with only a limited number of parameters. An extreme example would be to read the tone point by point, but, apart from making the reading pro- cedure a very longwinded Fig. 4. Sounds generated by the Fourier synthesis technique: M is the per- centage modulation and C=1 indicates that the fun- damental and modulating frequencies are equal. affair, there is also the diffi- culty of determining the spectral constitution of any given sound. Modern synthesis tech- niques seek a compro- mise between the number of defining parameters and the specified output. Since each method can only take account of cer- tain aspects, its mathe- matical structure results in definite characteristics which are clearly identifi- able in the final sound. Fourier synthesis Since synthesis is the op- posite of analysis, and Fourier analysis enables any waveform, no matter how complex, to be represented by a series of simple sine waves that are harmonically related, it is possible to build a com- plex waveform from a number of sine waves. This mathematical concept does not need a digital synthesizer to put it into practical form, for it has been used for a very long time in the generation of sounds in organs. Flowever, because of technical elektor india decamber 1986 12-39 limitations, only a rela- tively small number of controlled harmonics can be realized in these in- struments. The modern computer has made it possible, at least in theory, to make a virtu- ally unlimited number of harmonics available, whose amplitude can be controlled very precisely. In practice, however, only thirty-two harmonics are generally used, because the computing time rises with each harmonic. The great benefit of digital Fourier synthesis is that it makes it possible to give each sound its own har- monic spectrum. To prevent too great an in- put (writing) complexity, only two reading methods are used in practice. With the first, a separate ampli- tude envelope is input for each harmonic; the envelope extends over the entire length of the sound to be computed. With the second method, the overall spectrum is written for each separate period; the intermediate values of the as yet undefined periods are then inter- polated by the software. The second method has some advantages as well as some disadvantages as compared with the first. Advantages are: • the input is strictly analytical and there is, therefore, a direct relation between the input and the final output; • there is accurate con- trol of tones in each in- dividual period. Disadvantages are: • greater input com- plexity; • relatively long comput- ing times; • harmonics that fall out- side the proposed frame can not be used; • the computed wave- form does not by itself attain maximum ampli- tude so that additional and intricate regulation is required before and after the computation. FM synthesis In analogue synthesizers, 12-40 elektor india decomber 1 986 the output of the tone os- cillator is modulated by the signal from a second oscillator to give the generated sound more liveliness (vibrato). Such frequency modulation has also been used in radio broadcasting for many years. In the 1970s, J Chowning, an acoustic engineer searching for an alterna- tive to the complex Fourier synthesis method of tone generation, found that fre- quency modulation can also be used for the direct generation of sounds. In the ensuing FM synthesis technique, one sine wave is controlled by another. The range of harmonics and, therefore, the colour of the output sound are determined solely by the difference in frequency between the two waves and the depth of modulation. Although FM synthesis of- fers a real easing of the writing procedures, it does not provide a direct re- lation between the input and final output signal. Consequently, it requires much experience and trial and error to produce sounds of a predeter- mined character. It is not possible to deliberately in- fluence the harmonics in the output signal. Summarizing, FM synthesis has the following ad- vantages: • fairly easy writing pro- cedure; • short computing time; • depending on the re- lation between the two sine waves, even non- harmonic frequencies may be generated; • the waveshape is always computed with maximum amplitude; and the disadvantage that analytic tone gener- ation is not possible. Waveshaping synthesis If a sinusoidal signal is ap- plied to the input of a non-linear network, the output will not be a sine wave, but be distorted to a degree that depends on the characteristics of the network. If this output is analysed, it is found that a number of frequencies has been added to that of the original input signal. This property is the basis of waveshaping synthesis. It is, however, practically impossible to predict the sound spectrum resulting from the application of a sine wave to a non-linear network. The relation be- tween the non-linearity and the output sound has been analysed mathematically. This analysis has shown that for each harmonic wanted in the output the network re- quires a separate poly- nomial characteristic. 'The individual polynomials are mathematically related and are calculated with the aid of a recursion for- mula and the ordinal number of the relevant harmonic. The resulting row of polynomials is known as the Chebishev polynomial. To obtain a number of suit- ably weighted harmonics in the output spectrum, each relevant non-linear characteristic is calcu- lated with the appropriate weighting factor. The resulting polynomials are added together lo arrive at the composite non- linear function from which the network constituents can be computed. A sinusoidal signal applied to the resulting network will give rise to an output sound that contains all the predetermined harmonics in correct proportion. The waveform of the output sound can be varied simply by altering the content of the non-linear function, i.e. by changing the value of one or more components contained in the network. Summarizing, waveshap- ing synthesis combines certain aspects of Fourier synthesis, i.e. the analytical sound construc- tion, and FM synthesis, particularly the simple writing procedures and the short computing time required. It has these ad- vantages: • simple writing pro- cedure; • analytical input character; • short computing time; • the technique of waveshape distortion is modelled on the tone generation by "natural" in- struments, so that in many situations it is possible to synthesize simple and natural sounding tones. Disadvantages of waveshaping synthesis are: • harmonics can not be controlled as accu- rately as with Fourier syn- thesis; • it is difficult to achieve optimum control of the final waveshape; • it involves complex mathematical relations and operations. Phase distortion synthesis Phase distortion synthesis is, to some extent, a com- bination of FM synthesis and waveshaping syn- thesis in that a non-linear network is used to alter the phase angle of the sinusoidal input signal. From a mathematical point of view, this tech- nique is a special case ot FM synthesis. Here again, there is no clear relation between the non-linear function that causes the change in phase angle and the resulting sound. None the less, this tech- nique enables a fairly easy simulation of the tone generation of analogue synthesizers operating with the sub- tractive synthesis method. In practical terms, the non-linear network causes the output sound to have a shape that can be varied between sinusoidal and sawtooth. The resulting sound could be said to vary between "analogue” and "digital". sensilriw iglnhmetet The hghtmeter described in this article utilises a silicon photo- diode, the most up-to-date method of light measurement, and may be used either for photographic purposes or for the measurement of illumination. output voltage from IC1. To overcome this difficulty the output of 1C1 is attenuated by a factor of 10 by R4 and R5. This also gives the possibility of an extra range, as will be explained later. Three basic ranges are provided, 10 lux, 100 lux and 1000 lux, selected by means of SI and calibrated by PI, P2 and P3. Pressing S2 shorts out the attenuator on the output of 1C1, thus allowing a times ten multiplication of the ranges, or a maximum reading of 10,000 lux. If this highest range is not required then S2 can be omitted; R5 can be 1 k in this case. If, on the other hand, the lowest range is not required, S2 and R5 can be omitted and R4 replaced by a wire link. Most commercially available lightmeters still use cadmium sulphide photoresistive cells, which suffer from such disadvan- tages as slow response time, especially at low light levels, and a spectral response that does not match that of the human eye. A lightmeter using a silicon photo- diode has considerable advantages over meters using photoresistive cells: the spectral response can be made much closer to that of the human eye (and of photographic film), the response time is sufficiently fast, and finally, the response to light is linear. Unfortunately, from the photographer’s point of view, silicon photodiode metering is available only in the most expensive cameras with built-in metering, so a design for a home-built, hand-held silicon photodiode lightmeter would seem to be a good idea. The cir- cuit given here will measure light levels from 10 lux to 10,000 lux in four ranges, which is adequate both for the measurement of illumination and for photographic purposes. The complete circuit of the lightmeter is given in figure 1, and operates as fol- lows: light falling on photodiode D1 causes it to generate a negative voltage with respect to the 0 V rail. This causes the output of IC1 to swing positive, driving current round the feedback loop into D 1 . This current causes a' voltage drop across the diode’s internal resist- ance, which is in opposition to the volt- age generated by Dl. The output of IC1 takes up a positive voltage such that the two voltages cancel, i.e. the voltage at the inverting input of IC1 assumes the same potential as the non-inverting input - zero volts. The output voltage which IC1 assumes is proportional to the feedback loop current required to cancel the photo- diode voltage. This is proportional to the photodiode voltage, which in turn is proportional to the light falling on the photodiode. In other words, the output voltage of IC1 is proportional to the amount of light falling on Dl . Since the current through the photo- diode is fairly small, if the feedback resistors were connected direct to the output of IC1 they would have to be impossibly large to obtain a reasonable Construction A printed circuit board and component layout for the sensitive lightmeter are given in figure 2. The compact layout allows the lightmeter to be housed in a very small case, with ample room for a small 9 V battery such as a PP3 . The current consumption of the lightmeter is only a few mA, so the battery should last for many months of normal use. S3 may be a non-latching pushbutton to avoid the possibility of the meter being left switched on. Calibratign This )s always a problem with any home- built measuring instrument, especially a lightmeter, which should be calibrated against a standard light source. Fortu- nately, a sufficiently accurate cali- bration for most purposes can be achieved using ordinary domestic lamps. A normal 240 V, pearl, incandescent lamp has a light output between 10 and 15 lumens per watt. If it is assumed that the lamp radiates uniformly in all direc- tions then the illumination at any dis- tance from the lamp is easily found. The point at which the illumination is to be measured is taken as being on the sur- face of a sphere, at the centre of which is the lamp. The illumination in lux (lumens per square metre) is found simply by dividing the light output of elektor india december 1986 12-41 Figure 1. Complete circuit of the sensitive lightmeter. the lamp by the surface area of the sphere, i.e. where I is illumination in lux is light output in lumens r is distance from lamp in metres. This equation is valid only if the lamp radiates uniformly, and for this reason only standard pearl lamps must be used for the calibration procedure. Spot- lamps, high output lamps or lamps with any other internal reflector or coating are not suitable. Table 1 gives a list of useful distances with corresponding illumination levels. Two lamps are required for the cali- bration procedure, a 60 W lamp and a 1 00 W lamp. The lamp must be mounted in a plain lampholder without reflector, and should be the only source of illumi- nation. The calibration procedure must be carried out away from reflecting sur- faces such as mirrors or light painted walls. The calibration procedure is as follows: 1. Set the lightmeter to the 10 lux range and place it at a distance of 240 cm from the 60 W lamp. Adjust PI for full-scale deflection of the meter. Now place a piece of thick card between the lamp and the light- Figure 2. Printed circuit board and com- ponent layout for the sensitive lightmeter (EPS 9886). Figure 3. When used for photographic pur- poses the acceptance angle of the photo- diode is too great and must be reduced by a lens or tube. Table 1. lamp distance from lamp to photodiode illumination 60 W 240 cm 10 lux 60 W 105 cm 50 lux 100 w 100 cm 100 lux 100 w 45 cm 500 lux 100 w 30 cm 1000 lux (100 w 1 3 cm approx. 5000 lux) Parts list for figures 1 and 2. Resistors: R1 = 3M9 R2 = 390 k R3 = 39 k R4= 10 k R5 = Ikl (see text) R6 - 4k7 PI = 1 M P2 « 220 k P3 = 22 k Capacitors: Cl = 56 p C2 = 10 m/10 V tantalum C3 = 10 m/10 V Semiconductors: D1 = BPW21 (Siemens) IC1 =3130 Miscellaneous: 51 = single-pole 3-way switch 52 = push-to-make switch 53 = push-to-make switch M = 1 mA meter meter, when the reading should drop to less than 10% full-scale. If it does not then something in the room is reflecting light onto the photodiode. 2. Change to the 1 00 W lamp and set the lightmeter to the 1 00 lux range. Place the lightmeter 1 00 cm away from the lamp and adjust P2 for full- scale deflection. 3. Set the lightmeter to the 1000 lux range and place it 30 cm from the lamp. Adjust P3 for full-scale deflec- tion. 4. Check that the calibration still holds when the xlO button is pressed, e.g. the same reading is obtained on the 1000 lux range as on the 100 lux range with the xlO button pressed. 12-42 elektor mdta december 1 986 Table 2. Recommended lux for various tasks. class of visual task illumination values in example recommended illumination (lux) casual seeing hallway 100 ordinary tasks. making cabinets for electronic medium size detail projects; domestic living room 400 severe prolonged building a project on a tasks, small detail p.c. board; studying 800 very severe tasks. building a maximum-component- very small detail density prototype; 1500 detailed drafting exceptionally watchmaking 3000 severe tasks, minute detail Photographic use Calibration for photographic use pre- sents further problems, since an absol- ute calibration procedure is almost impossible. The best method of cali- bration is to beg, borrow or steal an existing exposure meter to use as a reference. Another problem exists with acceptance angle, since the BPW 21 photodiode will accept light over an angle of about 100°. This is much wider than the acceptance angle of the average camera lens, and means that the lightmeter will ‘see’ a different scene from that seen by the camera, including large areas of bright sky. This can easily result in false readings. The acceptance angle of the lightmeter must therefore be reduced by putting a convex lens in front of the photodiode, or by putting it in a tube. This principle is illustrated in figure 3. To calibrate the lightmeter against a commercial exposure meter, the two are placed side by side and pointed at scenes of varying brightness. A table of lightmeter reading versus exposure meter reading is made, and this can later be used to calibrate the scale of the lightmeter. The lightmeter reading is then used in conjunction with the photographic film speed to find the correct exposure, which is basically the correct combination of shutter speed and aperture setting. Unfortunately it is not possible to give a detailed calibration procedure for this method, since the scales of commercial exposure meters vary greatly, some giving a light reading that must be trans- lated into an exposure value, and others giving a direct readout of shutter speed and aperture setting. However, the calibration should not pose too much of a problem for the experienced photographer. A second calibration procedure is poss- ible, based on the calibration as lux- meter given above. The ‘calibrated’ lux scale can be converted to a photo- graphic lightmeter scale on the basis of the following knowledge: • fora 21 DIN (100 ASA) film, 120 lux on the scale is equivalent to a lens aperture of f 16 at a 1 sec. exposure time; • an increase by a factor 2 of the illumi- nation reading in lux corresponds to a 1-stop increase in lens aperture, or a decrease by a factor 2 of the exposure time, or an increase of 3 points on the DIN scale, or doub- ling of the film sensitivity value on the ASA scale. To give an example: if a 24 DIN (200 ASA) film is used (an increase by a factor 2 in sensitivity) and the light- meter gives an indication of 240 lux (also an increase by a factor 2), correct exposure could beobtained at fl6/!4sec, or f 1 l/t/8 sec, etc. Regrettably, this calibration will prob- ably prove insufficiently accurate for photographic use: it may well be one or two stops out. For this reason, it will be necessary to make a few test exposures for final calibration. M eloktor india december 1986 12 43 THE BATTLE FOR SUPERTELEVISION Europe and Japan are waging a technobattle over how best to provide the public with top-quality television pictures in the 1990s. Over the past dec- ade, the Japanese broad- casting authority, NHK, has been perfecting a high- definition television system that uses 1,125 horizontal lines across the screen, in- stead of the 525 lines they and the Americans use at present. This offers much finer grained pictures— better, in a sense, even than film. The Japanese, with the* Americans and Cana- dians in tow, have been pushing hard to get their high-definition television (HDTV) system adopted as a world standard- The Europeans are adamant that it should not be. At a recent meeting of the In- ternational Radio Con- sultative Committee in Yugoslavia, they man- aged to get the issue deferred for another four years of discussion. With better-quality pictures from 625-line television, Europe's broadcasting engineers do not see the NHK pro- posal as an answer to their own problems. The two sides have so little in common that four years may not be long enough to reach a consensus. For a start, America and Japan both have elec- tricity supplies that alter- nate at 60 Hertz (cycles per second), while Europe and most other places have 50-Hertz electricity. Television scenes il- luminated with light blink- ing 60 times a second (eg, in America) produce a shuddering effect when displayed on television sets which have their pic- tures refreshed 50 times a second. Europe's viewers tolerate shudder on the occasional American pro- 12-44 elektof india december 1986 I gramme. They would not like it all the time. Then there is cost. If adopted, the Japanese HDTV system would cost as much as did the switch from black-and-white to colour. HDTV viewers would have to buy a new tele- vision set to receive the super-quality pictures. Yet broadcasters would still have to transmit separate pictures for people with conventional colour and monochrome sets. Hence Europe's preference for a system that is evol- utionary rather than revol- utionary in design — and capable of being re- ceived by existing sets fit- ted with a cheap add-on box. The European Broadcast- ing Union has adopted a new family of television standards called MAC (multiplexed analog com- ponents), developed by the Independent Broad- casting Authority in Britain. These aim to provide all sorts of future television features — from wide- screen pictures, eight- channel sound and data to direct satellite broad- casting and better defi- nition. The intention is to have MAC pictures com- patible with all of Europe's existing television sets. The motives are not wholly altruistic. European equip- ment makers have been lobbying their govern- ments hard for fear that if (like the Americans) they accept the Japanese standard, they, too, will kiss their television businesses goodbye — as Sony, Hitachi, Sanyo, Toshiba, Mitsubishi and Matsushita tool up for a global price war in HDTV equipment for studios, transmission and home. From studio to home Yet Japan’s HDTV and Europe’s MAC are not in direct competition. Each represents a set of engineering standards for quite separate things, and serves different sectors of the television industry — which range from pro- gramme-making to distri- bution and display in the home. HDTV is seen as a studio standard for producers wanting to make features or commercials with the sharpness of 35mm film but taking advantage of the flexibility, faster turn- around and graphic tricks offered by video tape. Sony, Hitachi and Ikegami are all offering studio equipment based on HDTV standards. One of the first production companies to buy Sony's Sim HDTV system was Paris- based Captain Video, which has been using it to supply complex "matting" (ie, special optical effects) that would be too expens- ive using film, and imprac- tical with the video cameras and recorders used in studios today. The equipment promises pro- duction savings of 15-20%. HDTV studio equipment can also offer television stations better "prints" for broadcasting. After a commercial is in the can, successive generations of prints are made of it on 1-inch video tape for distribution — with a loss of quality compounded each time it is re-re- corded. An HDTV master tape made to 1,125-line television standards has a definition better than the electronic equivalent of 35mm film, while its con- version to 1-inch distribu- tion tape involves fewer quality-reducing stages. So distribution tapes emerging from HDTV studios tend to be superior to chose from film labora- tories. But HDTV is not a distribu- tion (ie, transmission) system in a television sense, still less a standard for domestic television sets. True, Japanese of- ficials are proposing a derivative called MUSE for transmitting HDTV pictures — but they have yet to win agreement among equip- ment makers in Japan, let alone the rest of the world. After that, they will need to develop standards for receiving and displaying HDTV pictures on domestic Never mind the quality, see the width television sets. Europe’s television engineers have, in con- trast, started in the middle. They argue that it is neither the studio nor the home, but the distribution link between them, which is in the greatest mess and needs to be stan- dardised. Mess? Broadcasters are finding that their medium no longer has a monopoly i over the distribution of pic- tures to the sitting room. Nowadays it has to com- pete for viewers’ time not only with cable television (and soon with two-way in- teractive cable), but also with video cassettes, video discs, video games, even home computers. Waiting in the wings are awesome new inventions like the CD- ROM (compact disc read- only memory), which stores encyclopedic vol- umes of pictures, text, music and commentaries, all capable of being inter- rogated by typing a few simple questions on the screen of a home com- puter. Studio in the sky The televison industry everywhere is under the same threat. Its great white hope is DBS — direct broadcasting satellites beaming television pro- grammes and other video delights down to viewers below. In 1977, the World Administrative Radio Con- ference allocated part of the frequency spectrum above 10 GHz (1 gigahertz is 1,000 megahertz) to satellite broadcasting. Ever since, broadcasters have been waiting impa- tiently for electronic firms to perfect the special microwave valves — known as travelling wave tubes — that would be powerful enough to transmit pictures direct from space to people's homes. The most powerful travel- ling wave tubes for broad- casting satellites look like | being the new 200-watt I devices being developed by Thomson-CSF in France and AEG-Telefunken in West Germany. The Mitter- rand government had hoped to have its TDF-1 DBS satellite with Thomson tubes in orbit by this year. The schedule has slipped by 18 months to two years, following troubles with the Ariane launcher and a change of heart by France's new conservative government. The French 200-watt tubes have never- theless been flown in two Japanese experimental satellites, BS-2a and BS-2b. One of these has now gone on the blink and nobody is yet sure how reliable the 200-watt transmitters are. If they can be made to work properly, DBS systems with 200 watts of power ought to be able to deliver pictures to dishes less than a tenth the size of the ground stations used for telecoms today. Unfortunately, even a 1.8 metre dish perched on a rooftop would be un- wieldy in a high wind. Mounted on the ground, it would need about half a ton of concrete to keep it steady. In Britain, it would also need to have plan- ning permission. Hence the pressure to develop ever more sensi- tive receivers — so that domestic dishes can be reduced to 90cm or even 60cm in diameter. These could be mounted in the loft. Their price would drop from SI, 000 or so for a 1.8-metre dish and its decoder box to around $350. At the 1977 conference, five channels plus "park- ing places" in geosyn- chronous orbif were allo- cated to each country in Europe. Britain and West Germany still say they hope to have their DBS services working by 1990. In April, the IBA in Britain started advertising fran- chises for three (out of Britain’s five) DBS channels. The offer closes on August 29th. But the satellites still have to be built and launched. With the setback to America's shuttle pro- gramme and problems stacking up for Europe's own Ariane launcher, few are now putting money on getting DBS services up and running in Europe (or anywhere) by the end of the decade. Overhaul for telly Europe's route to high- definition television — and other technological im- provements — is via DBS. The reasons are threefold: • Money. Most broad- casting authorities in Europe have already had to replace or upgrade much of their existing equipment for terrestrial transmission. They cannot justify upgrading it again for a decade or more. • Improvements. Though developed later than America's 525-line NTSC colour system (adopted by Japan), both of Europe’s 625-line systems, PAL and SECAM, are beginning to show their ages. Television engineers everywhere want to get rid of inherent problems in. first-gener- ation colour equipment — like the "edge” and "moire" effects caused by highcontrast colours on captions and closely- striped patterns. • New features. In their battle for the viewers’ attention, broadcasters want to be able to market technological refinements that give television an edge over its new video rivals. Top of the list are stereo sound, additional commentary and data channels, wider pictures and higher resolution. The MAC family of stan- dards has been designed to provide ail these and more. The principal stan- dard, C-MAC. has been optimised for satellite transmission. The version for cable television is D- MAC. A narrower-band derivative called D2-MAC, elektor India decembef 1986 12-45 carrying only half the number of sound chan- nels, has been added for early community-wide cable systems. Television engineers in Europe and Japan differ fundamentally on how they see the television set of the 1990s. Where Japanese engineers ex- pect it to be a bulky box built round a high-resol- ution cathode ray tube, the Europeans see flat- panel displays more than twice the size of today's largest television screens. The IBA in Britain argues that television tomorrow will be more cinema-like. People are not going to change their sitting rooms, but they will get wider and bigger pictures. The old 4x3 proportions of the cathode ray tube were designed to match the cinema screen of the pre- television era. But in response to competition, film went wider — to the extremes of Cinema- Scope's 7.05x3 proportions before settling down to be- tween 5x3 and 5.5x3 (not far trom the 4.85x3 “golden mean” favoured by artists). The new metre- wide flat-panel displays are being developed with heights of 60cm to give cinemalike proportions. Another visual effect which television engineers are cribbing from film is image size. The best seats • in a cinema are at 3-3.5 times the screen height trom the front (see chart). Viewers at home tend to Dates for your diary CONFERENCE ON QUALITY AND RELIABILITY IN ELECTRONICS 8. TELECOMMUNICATION The STQC Directorate of the Department of Electronics and the Confederation of Engineering Industry (CEI), formerly Association of Indian Engineering Industry (AIEI) are jointly organising a Conference on Quality & Reliability in Electronics & Telecommunications to be held on February 23-24, 1987atVigyan Bhavan, New Delhi, under the auspices of 12-46 elektor india dec«mb*r 1 986 sit around 10-12 times the screen height from the television set. Given a screen 60cm high, and keeping their seats in the same position, they would' be sitting at six to eight times the screen height — close enough in pro- portional terms to start picking up some of the “towering" effects pro- duced by cinema's larger images. Will such a television screen need more than 625 lines? No, say Europe’s television planners. HDTV, they argue, is fine for mak- ing high-quality videos for big cinema-sized screens. But its 1,125 line resolution is overkill for broadcasting to the home. Displaying even a 35mm film in an "electronic cinema" would need only 800 lines or so. Besides, they say, there are some technological tricks that allow C-MAC to otter the closest thing to HDTV — and still be viewed on existing tele- vision sets. So-called "enhanced C- MAC” uses digital tricks and microchips borrowed from the computer in- dustry to get a sharper and bigger picture. To provide the wider 5x3 pic- ture, engineers have bor- rowed six of C-MAC's eight sound and data channels. Wide-picture viewers would still be able to get stereo sound, but everybody would have to give up optional foreign language commentaries. On each television line, the sound signals would be sent not as the usual analog waves, but as a morse-like stream of "digital packets" (akin to a packetswitched data net- wo'rk) transmitting 3m bits of computer data a sec- ond. The colour signals would be transmitted sep- arately, one after another, instead of simultaneously but separated slightly in frequency. All colour television systems (NTSC, PAL or SECAM as well as MAC) use three separate signals to transmit the full range and brightness ot the colours. A mixture of red, blue and green (in the proportions 30%, 11% and 59%) is transmitted as the "luminance" signal. This provides the compatibility for black-and-white sets and carries the infor- mation used by the eye's monochrome receptors ("rods"). The two additional signals needed to supply the colour are sent as the blue component minus the luminance, and the red minus the luminance. Both trigger the eye's colour sensors (“cones”) which have lower resolving power. The trick adopted in the so-called C-MAC/Packets approach is to give the resolution-supplying luminance signal as much room as possible to do its job, while squeezing the colour components slightly — and, by separ- ating them in time, ensur- ing they do not get in the Asia Electronics Union, Japan. ELCINA and ITMA are co-sponsors of the Conference. CAPACIT- 86 Indian Electrical and Electronics Manufacturers' Association (IEEMA) is organising an International Seminar and Exhibition on Capacitors called CAPACIT - 86 in Bombay. The Seminar will be held on 5th and 6th December, 1986 and Exhibition from 5th - 7th December, 1986. The venue in Bombay is the Institution of Engineers. contact: CAPACIT - 86 Organising Secretary. Indian Electrical and Electronics Manufacturers' Association (IEEMA), 501. Kakad Chambers. 312, Dr. Annie Besant Road. Worli, Bombay - 400 018. INDIA COMM 87 India's first international Telecommunications 8i Computers exhibition and conference. Endorsed by Department of Electronics (Government of India). Telecommunications Consultants India Ltd. (Ministry of Telecommunications Chapter (IEEE) will be held on January 28-31, 1987 at Pragati Maidan, New Delhi., contact : Vlrs. Nita Singh each other's wav. As an optional extra, a "frame store" can be used to dispense with the con ventional interlacing pro- cess and all its problems. To reduce flickering, alter- nate lines of the picture have been sent since the beginning of television in the first cycle, followed by the alternate set in the next cycle, and so on. In Europe, that means interlacing 312.5 lines 50 times a second; in America and Japan. 262.5 lines 60 times a second. So the net result is only 25 full frames a second in Europe and 30 frames in America and Japan. However, future television sets could display their full complement ot lines (525 or 625) every cycle if they had a frame store to hold, juggle and derive their video signals — and would do so without flicker or any of the side-effects of interlacing. Used in conjunction with en- hanced C-MAC, this would be equivalent to 50 full frames being painted on the screen every second. Enough, say its pro- ponents, to give C-MAC more than sufficient pic- ture sharpness to cope with the most demanding of transmissions — while allowing viewers to use their existing sets by buy- ing only a small add-on box. Reproduced with per- mission from The Economist Executive Officer Confederation of Engineering Industry 1 72. Jor Bagh, New Delhi 1 10 003 INDUSTRIAL INDIA 2001 The 10th National Convention of the Institution of Industrial Managers India is to be held on March 27th 8i 28th, 1987. The theme of the Convention is INDUSTRIAL INDIA 2001. Please contact : INTERM A TECH CONSULTANCY. 43, Satyam (4th Floor), Opposite Odeon. PantNagar. Ghatkopar (East), Bombay - 400 075. TELL-TALE MAGNETISM OF HEART-THROBS by Mr Donald Longmore, Consultant Clinical Physiologist, National Heart Hospital, London A team of doctors and scientists working at the Magnetic Resonance Unit of the National Heart and Chest Hospital in London has succeeded in producing pictures of the heart that reveal blood vessels only two millimetres in diameter, never before seen by any non-invasive technique. Moreover, they have developed a procedure to measure accurately various blood flows, opening the way to painless detection of hidden cardiovascular disease before it leads to sudden death. Nuclear magnetic resonance (NMR) was discovered independently in 1948 by two scientists, Professor Bloch and Pro- fessor Purcell, both of whom were working in the USA. They received a joint Nobel Prize for their work. Since then, NMR has been used routinely as an analytical instrument in chemistry. It was a logical extension of NMR to apply it to studying biochemistry in the living body. Dr Radda, at Oxford University, has been studying this appli- cation for a decade; Dr Mansfield, at Nottingham University, was probably the first to produce a [ human image, in 1976. Magnetic resonance has the greatest potential of any non-invasive tech- nique that has been de- signed or even envisaged so far. It has been developed mainly as an imaging device to pro- duce pictures of hitherto inaccessible parts of the body in health and disease. While it is an immensely powerful diagnostic instru- | ment, it has even greater I potential in preventive medicine because it is safe, painless and can be used to screen normal people. About half of all deaths in the western world are caused by one disease process, the blockage of arteries with atheroma, and one-third l are due to cancer. So it is logical to apply magnetic resonance to screening for such diseases. To do that effectively it was necessary to develop the technique to measure the working of the heart and its blood flow. Dimensional accuracy The National Heart and Chest Hospitals Group in London has been able to measure these with great accuracy. It first showed the dimensional accuracy of the technique, by using static models called phantoms, designed to mimic the heart chambers. Results from ex- periments with phantoms showed that it was poss- ible to measure accu- rately volumes in cavities the size and shape of heart chambers. To study the heart, which is capable of rapid move- ment, a system of gating the procedure had to be devised and tested. So special, so-called dynamic phantoms were made, to pulse hearts and blood vessels artificially. The ability of MR imaging to 'freeze' motion was shown with a device known as a pulse duplicator which could, at various velocities, inflate a balloon inside a cadaver heart with varying volumes ot fluid to simulate its con- traction and filling. alaktor mdia dacembar 1986 12-47 The time-of-flight or downstream-slice technique for measuring blood flow. The spin-echo sequence is per- formed in halves: first, the pulse to tip the precession of nuclei to 90 degrees is applied to one slice of the body, and the pulse that tips precession by 180 degrees is ap- plied to a slice downstream of the first. Return signal from the body is then obtained only from material that has flowed between the two slices, and not at all from station- ary material. Simulation of the heart's movement in this way was triggered by the electro- cardiograph (ECG). The experiment tested the ECG gating and the volume measurements taken on a moving target. It also demonstrated how ac- curate were measure- ments on a living heart. Our next step was to prove the technique in Man. To do so, we compared the outputs of the right and left ventricles over a few minutes. The outputs of the two sides of the heart are identical: the basic tech- nique for measuring volume was to measure the areas of contiguous slices of known thickness in the heart and then sum them to find the volume of blood contained within each slice, rather like measuring the areas of slices of bread in a sliced loaf of known and consist- ent slice thickness. All the volume measurements of heart cavities were ac- curate to within two per cent. Measurements of heart wall thickness not available from X-rays were also found to be accurate. Although the heart con- tracts extremely rapidly, the gating technique (using the R-wave, which is the prominent first wave of the ECG) combined with various delays before the MR sequence was applied made it possible to cap- ture the heart when it was at its fullest, its emptiest and at any stage in be- tween. Using the ECG trig- ger, we found that at least in laboratory experiments it was possible to calculate very accurately the volumes within heart chambers. To show the clinical value of the technique in Man, the volumes of contracted and filled right and left ventricle chambers were measured in a large number of normal and diseased hearts. Over 256 beats of each heart have to be monitored to pro- vide the data. If no heart valve is leaking and there is no abnormal communi- cation between heart chambers, the two sides of the heart pump the same amount of blood. Any discrepancy in the measurements must be caused by a defect such as leaking valves or holes between heart chambers. MR was found to be more accurate than nuclear medicine, ultrasound and cardiac catheter tech- niques for detecting these. There are various ways of measuring the blood flow by MR. Before they are de- scribed, we need to take a look at the principle of MR itself. How does MR work? In an atom, positively charged and neutral subatomic particles, pro- tons and neutrons respect- ively, form the nucleus and the negatively charged electrons orbit about the nucleus at rela- tively great distances from it, moving at speeds ap- proaching that of light. The particles making up the nuclei spin on their own axes some 10 18 times a minute. The natural spins of protons and neutrons are in opposition; so, in certain atoms where they do not balance one another there is a net positive charge which, although very small, is rotating at a high speed and behaves like a tiny bar magnet which auto- matically aligns in a mag- netic field. Unlike compass needles, in which the North-seeking poles all face North and the South- seeking poles South, atomic nuclei line up with only a very small preponderance of those the correct way round over those the wrong way round. In a magnetic field of 0.495 T (tesla) the preponderance i_s only six in one million. The most commonly used nucleus in MR imaging is that of the hydrogen atom. The proton, as well as spinning in line with the magnetic field, precesses rather in the way a child's top wobbles before it runs down. It does this at a precession angle of 54 degrees and at 22 070 700 Hz (hertz). Energy can be fed into the system by applying an electromagnetic radio wave, the magnetic com-, ponent of which tips the net magnetic moment of the hydrogen nucleus through 90 degrees. This produces a radio signal, also at 22 070 700 Hz, which is picked up by a detector. The rate of precession relates exactly to the strength of the magnetic This magnetic resonance picture of a slice 05 cm thick through the upper end of the heart (A) was taken recently at the National Heart and Chest Hospitals, London. It is remarkable because the research team has shown, for the first time, detail of the left coronary artery (B) and its branches, some of them of only about two millimetres diam- eter, by non-invasive scanning. It means that it is now possible to see small coronary arteries and measure the blood flow in them for the diagnosis or prediction of heart disease. Among other details that can be clearly seen are the internal mammary arteries and veins to the chest wall (C) during certain operations on the heart they are sometimes plugged into the coronary vessels to bypass blockages. Prominent in the scan are the left and right ventricular outflow tracts (D, E), the left atrium (F). the backbone (G) and spinal cord (H). 12-48 eloktor mdia december 1986 In the saturation technique for measuring blood t low in the body, a slice is saturated magnetically with a pulse tipping the precession to 90 degrees. In a subsequent pulse, only blood that has flowed into the slice gives a signal, because only material that is magnetically clean can do so. The intensity of the signal increases with time until flowing blood has completely replaced the saturated blood, and the rate of that increase reflects the velocity of blood flow. The maximum signal reflects the diameter of the blood vessel. field. This has disadvan- tageous and beneficial ef- fects. It causes the signal given off by the nucleus to disappear quickly because certain chemicals nearby are more strongly magnetic than others, so some pro- tons precess faster than others and the coherency of the signal is lost. Spatial resolution is obtained using the relationship be- tween the rate of pre- cession and the magnetic field: supplementary mag- netic gradients are placed across, along, and up and down the field, so that nuclei emitting at one particular frequency must be at a unique place within the patient. There are three techniques for measuring blood flow. First is called the time-of- tlight or downstream-slice technique, in which a thin slice of the patient is sub- jected to the first half of a sequence, then the sec- ond half is applied to a slice at some distance from the first. Only the material that arrives in the second slice and which has been prepared by the first half of the sequence can be seen. By varying the time delays and distances apart of the slices, the velocity of flow can be assessed. The second technique relies on making a thin slice of the body un- suitable for MR imaging by pulsing it with random signals. That temporarily causes magnetic chaos, so no coherent signal can be obtained from it. An MR signal applied to the slice after a suitable inter- val will be sensitive only to the magnetically 'clean’ material that has flowed into it over that time; the amount of signal at any time relates to the amount of blood or other fluid that has flowed in. The experi- ment can be repeated with a number of different time delays, producing a graph of signal intensity against flow with a slope that flattens off acutely. The steepness of this slope relates to the flow velocity and the height of the plateau relates to the diameter of the blood vessel. Third, and most accurate way of measuring blood flow is to produce an im- age in the normal way but to apply a magnetic gradient across the body for a certain time, and then to reverse the pre- cession of the nuclei by changing the phase of the radio pulse by 180 degrees, reapplying the magnetic gradient as before. Stationary material in the sample experiences a phase change related to the magnetic gradient in one direction during the first application of the pulse and in the opposite direction during the sec- ond application, so the phase changes in all such material cancel out. But flowing blood moves into a different phase territory during both parts of the sequence, and the change in phase detected from it is pro- portional to the velocity of A spin-echo sequence is used in the phase-mapping tech- nique for measuring blood flow. After a radio pulse that tips the precession to 90 degrees has been delivered, a transient magnetic gradient is applied and it alters the phase of the excited material by an amount that depends upon its distance from the selected slice. After the next radio pulse, with its phase changed by 180 degrees, has been applied an identical magnetic gradient to the first is used to restore phase; blood that has moved in the mean- time retains a phase proportional to the velocity of its flow. The diagram shows the phase change in blood with the field gradient. its flow, which can be ac- curately found with a high special resolution. Hitherto, there has been no way of measuring blood flow in detail in the most intact vessels, though certain superficial vessels can be studied by Dop- pler ultrasound. Fortu- nately, a method of vali- dating the flow technique internally was available from the volume studies already described. A four- way comparison of the output of the right ven- tricle and the flow in the pulmonary artery, and the output of the left ventricle and the flow in the aorta, allows crosschecks to be made. It all four coincide, the flow sequence is validated. This technique is now being applied to smaller vessels. Experimen- tally, it is sometimes poss- ible even to measure flow in those moving coronary arteries which are difficult to find. The diagnostic power that is now available to us, of measuring heart function and blood flow, together with the ability to detect turbulence in the flow of blood mean that it has become possible to understand the natural history of occlusive vascular disease and to study its development throughout life. Much more important is that the technique enables us to monitor the efficacy of drugs that might be used in the control of arterial disease, such as pro- stacyclin analogues and mitotic inhibitors (which would control the growth of smooth muscle in the arterial wall, an essential step in the formation of atheroma) or a combi- nation of both. It promises to give us a rapid way of finding out whether or not therapeutic substances ar- rest or reverse the disease. Through these fundamen- tal discoveries, it seems certain that a new gener- ation of MR machines, cheaper and simpler fo use, will make an in- valuable contribufion to eradicating occlusive vasular disease. alakloi india dacambar 1 906 12-49 RF CIRCUIT DESIGN VHF/UHF NOISE GENERATOR Noise is a phenomenon most constructors of RF (and AF) equipment have come to know as an undesirable, yet inherent, property of active devices. Therefore, it is paramount to lay out input stages for minimum noise production, we are told in most textbooks. Then why purposely generate noise when it is to be suppressed with all means available? It was already noted in various ar- ticles in this magazine that aligning an RF input stage for maximum am- plification is not usually the best way of achieving optimum performance if the receiver is to detect input signal levels only just above the noise threshold. Setting-up pro- cedures for receivers therefore com- monly finish with some instruction to align the RF input stage for lowest noise, not maximum amplification. But how does one go about doing that? The present design of a wideband noise generator is based on the prin- ciple of audible comparison be- tween receiver and generator noise level. Where day-to-day repeatability is not a prime issue, the generator enables users to quickly find the op- timum settings for a variety of re- ceiver types, including FM tuners and home-made VHF/UHF con- verters; sufficient noise output is available up to about 1000 MHz. Circuit description Without going into theoretical details of controlled noise gener- ation, wideband noise is available at Ki thanks to the apparently random excitation of electrons in the base- emitter junction of SHF transistor T 2 12-50 eloktor India dacambaf 1986 (see Fig. 1). In this design, a current source, Ti, controls the amount of output noise by passing an adjust- able current through T 2 , which has been connected as a zenerdiode. Monostable multivibrator (MMV) ICi can pulse the current source and hence the output noise at Ki. Con- tinuous output noise is also available by setting Si accordingly. A LED has been included to indicate the presence (pulsating or continuous) of noise fed to the receiver. The noise generator is battery- operated and consumes a mere 10 mA, which mainly goes on the ac- count of D> . Construction Fig. 2 shows the component mount- ing plan and track layout of PCB Type 86081. Note that Ki, a single hole type BNC socket, is mounted in a recess hole to allow the threaded part to be soldered straight to the PCB ground plane. This method of construction ensures minimal loss of output noise as well as correct im- pedance matching to the receiver input. Two leadless ceramic capacitors, C< and Cs , have been incorporated for adequate RF decoupling and coup- ling, respectively. If this type of slot- mounted capacitor is new to you, consult Indoor unit lor satellite TV reception-1, Elektor India. November 1986, ‘for information on practical handling. The noise generator is preferably fit- ted into an RF-tight metal enclosure. The PCB should be fitted such that Ki protrudes from a hole in the enclosure rear panel. Controls Pi, Si and S 2 , and the LED, are mounted on the front panel. Practical use Initially, set Pi to maximum noise out- put, while listening for the increase in AF noise from the receiver. Then reduce the generator output level to a point where it is still 6 dB above the receiver threshold. (6 dB cor- responds to about one unit on the re- ceiver's S-meter, provided this is calibrated.) Switch to pulsed generator noise and align the relevant trimmers or presets in the receiver input stage for a maximum difference between the two audible noise outpuPlevels. Since the human ear can discriminate between signals only marginally different regarding level, the proposed method is quite reliable in practice. Fig. I. Circuit diagram of the wideband RF noise generator. Parts list Resistors: Ri = 100 k Rj = t M Ri = 1k2 R« = 220 Q Rs = 22 Q R« = 27 Q Pi = 2k2 potentiometer Capacitors: Ci = 470 n Cr;C3=i TOO n Cr;Cs = 1 n leadless cer- amic (trapezoidal ca- pacitor) Ce = 22 n ceramic Fig. 3 shows the periodically switched noise from the generator over the full 0-1 GHz output band. The high pulse levels on the spec- trum analyzer screen correspond to noise output from the generator, the low pulse levels correspond to the analyzer’s internal noise threshold. Although the actual increase in noise is relatively small, the fact that it is pulsed rather than constant pro- motes the audible effect in the re- ceiver. Finally, it should be noted that the generator output noise level falls with increasing frequency; at the highest UHF TV channel (about 800 MHz), however, input stage alignment is still possible, provided there is no excessive cable loss be- tween Ki and the receiver input. B Semiconductors: Di = LED ICi = 7555 Ti = BC557B Tj = BFT65 Miscellaneous: Si = miniature SPOT switch Sz = miniature SPST switch Ki= single-hole BNC socket PP3 battery 9 V plus clip PCB Type 86081 (see Readers Services) Suitable metal enclosure Fig. 2. PCB Type 86081 has been designed to meet the demands of very-high fre- quency design. Note that BNC socket Ki forms an integral part of the completed board. Fig. 3. Pulsed noise, integrated by means of the spectrum analyzer 's 300 Hz video filter. As can be seen from the set sweep range, noise is available over the entire 0-1 GHz band. The small peak at about 460 MHz was caused by a local cellular radio relay station. efektor tndja decentbor 1986 1 2-51 selex -is Press a button, and the lift starts moving. Press a button and the motor starts running. How does just a small push on the tiny button cause a heavy object to move? Here, a small control current causes a heavy current to be switched on or off - typically through a relay contact. Every relay consists of two main functional parts: one electromagnet and one or more switches. Even a door bell can be thought of as a vibrating relay. The equivalent circuit is shown in figure 1 to illustrate the comparison The electromagnet consists of an iron core and a coil wound on that. The rectangle with an oblique line shown in the figure is the standard symbol for a relay coil. In modern electronic circuits, the relay as shown in figure 2 is very commonly used. Such a relay has more than one contacts which are mostly change over type. A small current flowing through the electromagnet coil can activate these contacts to change over from one position to other. The normally open contacts will close and the normally closed contacts will open. Such a relay may require a coil current between 20 and 200 mA. The operating voltage is generally 6V. 12V or 24V etc. The higher is the voltage, the lower is the current. Figure 3 shows the modern type of miniatarised 'Reed Relay’. These relays have generally only one contact installed in a hermetically sealed glass tube. The coil is wound around the tube. A small current of about 10 to 20 mA is enough to operate a reed relay. Figure 4 shows a different type of relay. This relay is used to operate a siren and the principle is somewhat similar to that of the doorbell. One end of the relay contact is connected to the relay coil itself. RELAYS 12-52 elettoc india decern bar 1986 selex To battery Pressing the switch energises the coil momentarily and this activates the contact to change over and break the circuit. This throws the relay contact into oscillations and the siren is activated. The current requirement of such a relay is very high (about 500 mA) Many more types of relays are in use, and a small "collection " of such relays is shown in figure 5 . If you come across an unknown type of relay and want to establish its nature, first open the cover. Then, press the small lever which appears just above the coil with a finger. From this you can make out two things. One is the type of contacts - normally open and normally closed, ad second is the force required to press the lever which, in actual operation, will be supplied by the electromagnet coil. The greater is the required force - the greater must be the operating voltage (or current) for the relay. Next step is to check if any code numbers are marked on the coil. The code number may have the voltage, current or the coil resistance value embedded into- it. If you find more than i two terminals coming out j of the coil, you must see the resistance across the different pairs of terminals and finally try them outl A battery can be connected directly across the relay coil terminals momentarily to see the effect. Figure 6 shows an important requirement when operating a relay with a driving transistor. A diode must be connected in parallel connection with the coil. This is required to allow a passage to the reverse e.m.f. generated during the operation of relay. elofctor indis d«cemh«r 1 986 12-53 selex I WIRE MOVEMENT IN A MAGNETIC FIELD We have already seen how a high current flowing through two adjacent wires produces movement between the two wires. The reverse is also true. Movement of wires can also generate current. In fact this is the basic principle of modern power generation. One of the most simple arrangements to illustrate this principle is shown in figure 1 . Let us call it the wire trapezel This wire trapeze swings between the two poles of a horse shoe magnet. The movement of wire in the magnetic field causes a voltage to be induced across the wire and thus a current flows the wire if the circuit is completed. The induced voltage is however very small. The magnitude is about 0.0001 V. We can measure such tiny voltages by using a suitable amplifier stage between the wire trapeze and the Meter. Figure 2 shows a practical arrangement which can measure the induced voltage. The wire trapeze as well as the amplifier. Stage is built on SELEX PCB. Figure 1 : The movement of a wire trapeze in the magnetic field of the horse shoe shaped magnet induces a voltage. Figure 2: An operational amplifier with high gain is used to amplify the induced voltage. The wire trapeze is directly soldered on the PCB. 12-54 elektor mdia decambor 1 986 selex The Amplifier used is the 741 1C, which is the most commonly used Operational Amplifier. It requires only a couple of additional components to be externally connected, as shown in figure 3. The non inverted input (+) is connected to a voltage divider made of two 1 KA resistors, which halves the battery voltage The moving wire is connected between the (+) and (-) inputs for amplifying the induced voltage through the 741 1C. The amplification factor or the gain is determined by R4 and R3 and in this case it is 10,000. For a clear deflection of the needle, a low voltage range, i.e. 3V or even IV can be selected. The trimpot PI is adjusted in such a manner that the meter indicates a positive voltage. Since positive and negative voltages would be indicated, this adjustment is quite critical. Figure 4 shows the component layout using SELEX PCB. An 8-pin DIL socket should be used for the 1C 741 and proper position of the markings should be observed Connecting wires to the meter should be long enough and flexible, so that they do not obstruct the movement of the swinging PCB (The PCB itself is used as a trapeze in this case). A number of interesting trials can be carried out with this construction. The magnets can be changed, amplitude of swing can be changed and also the direction of magnetic field can be changed. It can be observed that the magnitude of deflection changes for each trial but one thing remains constant: the nature of deflection The direction of deflection of the needle changes with change in direction of movement of the wire in magnetic field. Thus we can see the wire trapeze to be a generator of AC voltage. We can also use different types of construction for the moving wire and see the effect on induced voltage. The efficiency of the swinging wire increases considerably when it is made to form several loops, (as in a coil) because the voltage produced in every loop adds up to give a higher induced voltage, this arrangement is shown in fiqure 5. The experiment can also be conducted by using a different kind of magnet. The horse shoe shaped magnet can be replaced by an electromagnet or a coil having about 8 to 10 turns and connected to a 4.5V - battery. In this experiment, however, the battery will have to supply a heavy current. Another interesting arrangement is shown in figure 6. Here the conductor loop stands still, but the coil forming the electromagnet is connected to the battery for a very short period and disconnected. Due to this, a high current flows through the coil momentarily. The meter needle shows a clear deflection as in all previous cases. This proves an important aspect, that for inducing a voltage the movement is not physically important but what is important is the change in the magnetic field which is cut by the wire or the loops of wire. Whether the change in field is a result of movement of wire or through change in current flowing through the electromagnet coil is not important. The last experiment also illustrates the basic principle of the transformer The voltage across the eletromagnet coil produces a magnetic field which cuts the wire loops connected to the meter circuit. The change in this magnetic field induces a voltage across the wire loops, which is known as the induced voltage. This is nothing but the transformer action — which induces a voltage in the secondary winding depending on voltage across the primary Figure 3: The Amplifier circuit using the Operational amplifier 1C 741. and a few external components. Figure 4: The component layout on SELEX PCB. Even the battery can comfortably fit on to the PCB. 4 Component List R1. R2 = 1 Kf 1 R3 = 100 n R4 = 1 Mil PI = 10K11 Trimpot. TCI r 741 Op-Amp. Other parts : 1 Standard SELEX PCB 40 mm x 100 mm 1 8-pin DIL socket 1 9V battery pack 1 battery clip 1 4.5V battery pack 1 Meter/ Multimeter 1 Horse Shoe shaped Magnet alektor india december 1986 12-55 winding. This experiment also makes it clear why transformers can work only with AC voltages. In case of practical transformers, the coils or the windings are placed around an iron core, through which the magnetic field is concentrated. In a most commonly used step down transformer, the AC Mains voltage is connected to the primary winding and output is taken across the secondary winding which has less number of loops (turns) than in the primary winding. Thus the induced voltage in secondary winding is less than the mains voltage. Figure 5: The induced voltage increases proportionally when the number of loops of wire are increased. Figure 6: The horse shoe shaped magnet is replaced by an electro-magnet. A momentary current through the electro- magnet coil induces a voltage in the wire loop and produces a clear deflection of the meter needle. Figure 7: A transformer is constructed by placing the primary and secondary windings on a core made out of Iron Stampings. The Core concentrates the magnetic field in the windings and avoids loss of magnetic energy. 230V selex 12-56 •toktor mdia decamber 1 986 selex 1 BICYCLE DYNAMO A Bicycle Dynamo is a generator of AC voltage. Even the giant power house generators operate on the same principle as that of the bicycle dynamo: a voltage is induced in a coil if the magnetic field passing through it is made to change. In case of the bicycle dynamo, the coil is fixed and a magnet is rotated in front of the coil The alternate magnetic poles running across the coil make the magnetic field through the coil to change. This induces an alternating voltage in the coil to supply the current required by the small lamp. Figure 1 : The dismantled dynamo. The cylindrical magnet is driven by the bicycle tyre. It rotates between the teeth of the coil core. This produces an alternating magnetic field through the coil and in turn induces a voltage across the coil terminals. Figure 2: The teeth are alternately fixed on the upper and lower side of the coil. This makes the magnetic field through the coil to alternate. olekior mdis d«c«mb«r 1986 1 2 _ 57 selex Let us dismantle a bicycle dynamo and see what happens inside it. The dynamo indeed contains a magnet and a coil, but the coil is not in front of the magnetic pole faces as expected. It lies below the cylindrical magnet. How does it induce the voltage then? A bit confusingl The solution to this puzzle however lies in the two crown like rims made of iron plate. These sheet metal teeth allow the magnetic field from the Figure 3: The waveform of the dynamo voltage as seen on an oscilloscope screen. The waveform shows eight halfwaves per rotation of the dynamo. The waveform is not exactly sinusoidal but is a little distorted. The power house generators produce a sinusoidal voltage. rotating magnet to pass through the coil at the bottom. Four teeth are fixed at the upper end of the coil and four at the lower end. The cylindrical magnet has eight poles; four north poles & four south poles - placed j alternately along the circumference. Due to this arrangement, the four upper teeth are always faced with the same type of poles and the four lower teeth are faced with the opposite type of poles. Thus on rotating the magnet, the upper teeth alternately face north and south poles, whereas the lower teeth alternately face south and north poles. The field in the coil is continuously reversed four times per rotation. This continuously changing magnetic field causes an alternating voltage to be induced across the coil terminals. The proof of this can be seen in figure 3. This is how the waveform of the dynamo voltage looks like, on an oscilloscope screen. Eight half waves are produced per rotation. The frequency depends on the speed of the bicycle. Open circuit voltage of the dynamo is roughly around 1 2V which drops to 6V when a 3W lamp is connected. Even the car dynamo works on the same principle. Only change being that it does not have a permanent magnet but has an electromagnet. The current through the electromagnet coil is regulated to produce a stable voltage. The Digilex-PCB is now available! Price: Rs. 85.00 + Maharashtra Sales Tax. Delivery charges extra: Rs. 6.00 Send full amount by DD/MO/PO. Available from: precious f ELECTRONICS CORPORATION Journal Division 1 1 , Shamrao Vithal Marg (Kiln Lane) Off Lamington Road, Bombay-400 007. 12-58 elektor indil december 1 986 ©l©kt©? Kits I 1 I LCD Thermometer Issue No. 26 EPS No. 82156 Simple! Easy to assemble. Based on 1C 71 06 This thermometer is very accurate with a temperature range — 50°C to + 1 50°C. Ideal for house or laboratory. Complete kit (with cabinet) Rs. 575.00 Capacitance Meter issue No. 11 EPS No. 81 1012- 1/2 To measure those elusive farads, this project features — Read out on a 3 1/2 digit LCD — A measuring range from 0.1 pf to 20 mfd. — high accuracy. It is a complete instrument at a hobbyists price Complete kit (without cabinet) Rs. 750.00 Digilex Digital Trainer Teach yourself digital electronics in a simple, unique manner. Broaden your horizons and improve your fundamental understanding of the changing world of electronics around you. This trainer gives you an opportunity to learn electronics at a very reasonable cost. Complete trainer at Rs. 325.00 Junior Computer Kit This kit enables you to have a practical orientation of the concepts explained in the Junior Computer Book I. Get actual 'hands — on’ experience. Learn the basics of hardware and software in an innovative step - by - step manner. And that too at an incredibly low price-! Complete kit (without cabinet) Rs. 1500.00 Elektor Binder — This reddish binder collects your loose copies of Elektor into one handy volume. A Kits currently available Issue No. EPS No. Title Price. 33 85110 Telephone Exchange Rs. 1200.00 36 9827 Magnetiser Rs. 65.00 37 80054 Talk Funny Rs. 210.00 39 86013 Single Trace CRT Convertor Rs. 190.00 39 9967 VHF/VHF Modulator Rs. 105.00 28/29 85447 Fault finding probe for Ups. Rs. 60.00 28/29 85431 Hi-fi headphone amplifier Rs. 75.00 28/29 85476 Brakelight Monitor Rs. 25.00 28/29 85448 Electronic Dog Rs. 180.00 I simple system enables you to add each copy as it arrives and to remove a single copy without disturbing the others. Price Rs. 25.00 plus Rs. 5 for Packing & Postage. Buying one of our kits will save you the frustration of tracking down those elusive components that hold up your projects. General information, Ordering Information 1 . All payments in Advance by M.O.R O.or D.D. only. 2, Items will be send by R.P.P. only 3, Price includes Packing & Postage. 4. For orders out of Maharashtra state, Please add 10% as a 'incidental Charges' Send payment to: precious® m ELECTRONICS CORPORATION Journal Division 1 1 , Kiln Lane, Off, Lamington Road, Bombay - 400 007. t I m- WIRE WOUND POTENTIOMETER SSI have introduced single turn wire wound potentidmeters for various applications. Available in all standard values from 10 ohms to 25K ohms with_t 10% tolerance, the potentiometer is rated at 1 W at 40°C and derated to zero at 125°C. Operable in a temperature range of 10°C to 85°C, it has a Ni-Cu alloy wire for close tolerance and low temperature co-efficient of resistivitiy. For further details, please write to: SOLID STATE INDUSTRIES. 1. Narayan Bhavan. Jivdani Road. Virar (E). Dist: Thane. vibrations and shocks and working on 24V DC/ 18V AC 1 - 0. Further, it is compact, immune to noise, and panel mounting type for occupying minimum space. For complex systems, multiples of this unit can be grouped together for use For further information, write quoting Ref. No. P/315/86 to: M/S. ADVANI OERLIKON LTD Post Box No. 1546 Bombay - 400 001 CABLE BINDERS These binders (saddles & clips) are manufactured in thermoplastic and Nylon and have high insulation values. Modification of cable looms canbe done quickly. Due to high grade material it combines the right degree of toughness with the necessary flexibility to hold any type of cables securely without damage For further details contact ADORGUARD Advani Oerlikon have developed a 4 point Alarm Annunciator Panel the ADORGUARD for application in petrochemical, fertilizer, steel plants, thermal power stations and other continuous process industries. The instrument provides continuous audio visual indication of faults. The Adorguard is solid state device capable of withstanding M/S. STARUTE ENTERPRISES. 1 24B. Vivekananda Road. Calcutta - 700 006. ELECTRONIC FILLING CUM WEIGHING MACHINE Delinters India have developed an Electronic filling cum weighing machine for on line continuous feeding, weighing and packaging operations. Useful for quantities between 100 gms & 7 Kgs (a version for 10 Kgs 50 Kgs is also available) the machine is suitable for solids like granules, crystals, seeds, flakes, pallets and powders. The machine has several features viz. single operator is required, presence of counting device, digital display for weight, fast/slow dribble action for feeding, and voltage stabilization. The unit can be hooked to a small computer and printer for daily packaging reports. For further information, please contact. DELINTERS INDIA Pratap Road. Raopura Vadodara-390 001 . M/s. Luxco Electronics, Allahabad, pioneers in the manufacture of speakers have introduced speakers suitable for any automobile. The speakers are supplied in different sizes, to suit internal design of different types of automobiles Normally the sizes in 6V4" and 4" x 6" type of speakers are available. These speakers are supplied in four different ratings to deliver 12 Watts. 20 Watts, 40 Watts and 60 Watts total power output. These speakers perfectly match with any sophisticated world class Moni Mono Stereo tape decks. The uniqueness of these speakers is that they are marketed as a complete system consisting pair of speakers grill, cords and template. They are scientifically packed in thermocole packing to protect against transit shocks and are housed in polylaminated packing for added grace. contact : Distributor for South and West: M/s Precious Electronics Corporation Chotani Building 52-C Proctor Road Grant Road (East) BOMBAY - 400 007. PLASTIC MOULDED INSTRUMENT BOX FOR BACK MOUNTING : TYPE T-77 Comtech T-77' is an elegently designed plastic moulded instruments box suitable for back mounted instruments such as Timers. & various other control instruments, having overall dimensions of 1 10mm. L x 77mm W x 100mm. B. it consists of a moulded box, a cover, & a M S plate for back mounting, the box has an inside space 73mm. X 71 mm. for various components. A six way terminal strip fixed at the top & bottom, in front of the box provides an easy access for the terminals. The cover can accommodate a PCB of 77 mm x 72 mm. from inside & has a 1 .2 mm deep recess in front to take an Aluminium plate of 65 mm x 66 mm. for control indications, the box offered in Black & Grey colour with either Glossy or Matt finish, is most suitable for small instruments to be mounted side by side from the back, like e g. counters, controllers & timers etc. For futher details contact: COMPONENT TECHNIQUE 8. Orion Appartment 29 -A Lallubhai Park Road Andheri (West) Bombay-400 058 PCB TERMINALS ELCOM offers a new PCB mounted screw terminal block. It is available as a standard 3 pin module, which is stackable in multiples of 3 without disturbing the 5 mm. Pitch. The pin diameter is 1 mm. and the maximum wire size that can be used with the block is 2.5 square mm. Current rating is 10 A at 380 V (RMS). Maximum operating temperature is 100°C. For further information : ELCOM 1 03. Jay go pa I Industrial Estate. B. Parulekar Marg. Dadar. Bombay 400 028 12-60 •lektpr india decamber 1 986 Appointments Appointments Appointments CTR Require DESIGN ENGINEER: BE/DEE/SERE with minimum experience in Design, Research and Development of professional grade components, preferably Capacitors. Must be conversant with IS, BS, DIN, IEC, MIL specifications and latest technology. Age: 35 years. Minimum emoluments Rs. 2000.00 per month with subsidised housing. Candidates meeting the above require- ments need only apply. Excellent pros- pects for the right candidate. Apply in English in your own hand writing to: Personnel & Administrative Manager CTR Mfg Ind Ltd El, Chikalthana Aurangabad 431210 Required SALESMEN with Electronic background apply Sales Manager, P.O. Box 9122 Bombay-25 Bharat Bijlee ELECTRONIC ENGINEERS Research & Development Design & Development Marketing Thane Rs. 24,000 to Rs. 36,000 p.a + perks Bharat Bijlee Limited, a leader in the Electrical Engineering Industry with professional manage- ment and an annual turnover of Rs. 40 crores needs Electronic Engineers for its R&D Centre and Electronics Control Division. For R&D Centre, graduate or post-graduate Engineers with specialization in Industrial Electronics, Power Electronics, Process Controls or Micro-processors and with about 5 years' experience in design and development of elec- tronic controls, are eligible. For Electronics Control Division, qualified elec- tronic engineers with minimum 2 years' experience in marketing of industrial electronic products will be preferred. Alternatively, Electrical Engineers with 2-4 years’ experience of marketing of indus- trial products with an aptitude for application engineering oriented marketing in electronics can also be considered. Selected candidates will have good prospects of advancement. Emoluments, designation and status will be commensurate with qualifications and experience. Please apply, within 1 0 days, giving details of age. qualifications, nature and length of experience, present and expected salary with break-up, marking the envelope “ Electronic Engineer" to : The General Manager (Personnel) Bharat Bijlee Limited P B 100, Kalwa, Thane 400 601 Maharashtra elektor imjia decsmber 1 986 1 2*61 Our advertisers will be pleased to know that our circulation has been steadily growing and our print order is now 16500 copies. You will also be pleased to know that our circulation will be certified by ABC shortly. Our advertising rates have remained the same since the first issue of elektor-lndia in May 1 983. We now find it difficult to continue the same rates in view of the escalating costs of every input that goes into publishing elektor- lndia. The new advertising rates with effect from 01-01 -1 987 are given mEco msTRumEnis private ltd. Bharat Industrial Estate. T.J. Road, Sewree, Bombay-400 015 Telex: 01 1 -71001 MECO IN V Phones: 41 3.-7423. 41 3-2435. Cable: "STANCOR" elektor iryjt. decamber 1 966 12-67 classified ads advertisers index 8085 MICROPROCESSOR TRAINER built in EPROM programmer, power supply, 2K CMOS/RAM with dry cell back up expaneable to 8 K, 12 K user EPROM installed Rs. 2975/- All inclusive. EPROM Eraser Rs. 500/- Contact: NEW AGE ELECTRONICS, Third Floor. Laxmi Mahal, Near Vandana Cinema, Agra Road, Thane - 400 602 Available Printer Interface card for 460 mechanism. Input 10 digit parallel BCD with Real time calender clock & self test facility. Open execution without Printer for Rs. 3500/- only. Contact: Process & Control Elements, 1 1 1 A, Hind Saurashtra Industrial Estate. Marol Naka, Andheri (E), Bombay-400 059 Ph: 6326579. Available 44 pin .1 ' card edge connectors 0/E/N, Part No. 04U-22-1 5-235-20-84 for Rs. 55/- + taxes. Delivery Ex stock. Limited quantity available. Payment through bank. Contact: SILICON-AIDS, 1 1 1 A, Hind Saurashtra Industrial Estate, Marol Naka, Andheri (E). Bombay-400 059 Ph. 6326579. IMPORTANT SUBSCRIPTION RENEWALS ARE ON! HAVE YOU RENEWED YOURS? 0n8 y 0ar U Rs. 75-00 G) Two years C5 Rs. 140-00 G) Three years Rs. 200-00 * To use the card in this issue * To quote your subscription number * To mention that it is a renewal * To send your renewal at least one month in advance * Timely renewal ensures continuous receipt of issues without irritating breaks ACE COMPONENTS 12.68 AIR INDIA 12.09 ARADHANA ELECTRONICS 12.68 APEX ELECTRONICS 12.69 APPOINTMENTS 12.61 COMTECH 12.08 CYCLO 12.12 DEWAN RADIO 12.06 DEVICE ELECTRONICS 12.63 DYNALOG MICRO SYSTEMS .. 12.76 ELCIAR 12 64 ELECTRONICA 12.08 ELTEK BOOKS N KITS 12.10 GALAXY ELECTRONICS 12.69 GENERAL ELECTRONICS 12.04 GRAFICA DISPLAY 12.12 IEAP 12.68 INSTRUMENT CONTROL 12.69 JETRONICS 12.69 J.M. ENTERPRISES 12.13 KIRLOSKAR 12.11 LEADER ELECTRONICS 12.72 LUXCO ELECTRONICS 12.07 MECO INSTRUMENTS 12.67 MELTRON 12.18 NAVIN FLUORINE IND 12.75 NCS ELECTRONICS 12.70 PHILIPS 12.14 PIONEER ELECTRONICS 12.70 PRECIOUS 12.59 12.72 ROCHER ELECTRONICS 12.06 SAINI ELECTRONICS 12.64 SMJ ELECTRONICS 12.73 SUPERB PRODUCTS ... 12.10 12.70 TEJUTRON 12.72 TEXONIC INSTRUMENTS 12.10 THERMAX 12.12 TRIMURTI ELECTRONICS 12.64 VASAVI ELECTRONICS 12.02 VISHA ELECTRONICS 12.03 VISTAR ELECTRONICS 12.08 ZENITH 12.65 12-74 elektor mdia decemb«r 1 986 elektc? electronics and its Methanol Azeotrope the ideal cleaning solvent used worldwide by the Electronic Industry Actual users please contact: HR Navin Fluorine Industries Chemical Division of THE MAFATLAL FINE SPG. & MFG.CO.LTD. Mafatlal Centre, Nariman Point, Bombay 400 021. Tel: 2024547 Grams: MAFINISED Telex: 011-4241 MGMC IN FERREIRA ASSOC/NFI/241/86 R N. No! 39881/83 MH/BYW- 228 LIC No 91 WHICH Microprocessor? Microprocessors are now being used in a wide range of products, from Mixers and Washing Machines to highly sophisticated Industrial Robots. Have you decided which microprocessor you will be using for your new products? Will it be 8085, Z-80, 8086, 8088, 6802, 6502 or will it be the powerful 32-Bit 68000? Whichever Microprocessor you select , Dynalog has a suitable Training and Development System for Training And Development Systems Based On : 8085, Z-80, 8086, 8088, 6802, 6502 And 68000. Dynalolg Micro Systems offer you the most comprehensive range of Microprocessor T raining and Development Systems. Starting with the Low Cost Systems based on 8085. Z-80 and 8088. the Top of the range covers Single Board Computers based on 6502 and Z-80, and a Full Fledged Single Board Development System based on 68000. The Single Board Compi[ter-Super80 based on Z-80 has on board interfacesfor Centronics Printer, Video Monitor, ASCI I Keyboard. RS-232- C Serial Communications and Floppy Disk Drives of both 5% and 8 inch types. It is fully compatible with CP/M Operating System. The standard features of the MICROFRIEND Series Training and Development Systems include Hex Keypad. Seven Segment LED Displays, On board EPROM Programmer, Timer/Counters, Parallel and Serial I/O Ports, STD Bus on edge connector, Powerful Monitor Firmware in EPROM. Detailed Documentation/Operating Manuals etc. Systems like the MICROFRIEND-III also offer facilities for programming in BASIC, FORTH or 8085 ASSEMBLY LANGUAGE with built in interfaces for Video Monitor, ASCII Keyboard and Printer. Dynalog Micro-Systems 14, Hanuman Terrace, Tara Temple Lane, Lamington Road, Bombay 400 007 Tel: 362421, 353029 Telex: 011-71801 DYNA IN Gram: ELMADEVICE Branches and representatives at: Pune. Bangalore. New Delhi. Hyderabad and Chandigarh Printer Sc Publisher — C.R. Chandarana, 2, Koumari, 14th A Road. Khar, Bombay 400 052. Printed at Trupti Offset. 103 Vasan Udyog Bhavan. Tulsi Pipe Road. Lower Parel. Bombay 400 013. ADDMark