| elekiter slsctromi IcsVolume-7, Number 10 October- 1989 Publishor: CR. Chandarana Ealtor: Surendra lyer Clreulation: Advertising: J. Dnes Production: C.N. Mithagari ‘Address: FLEKTOR ELECTRONICS PVT. LTD. 52. C Proctor Road, Bombay-A00 007 INDIA Telex: 11) 76661 ELEK IN OVERSEAS EDITIONS Elektor Eleetronies [Publiehing) ‘Down House, Sroombil Road, CONDON Swi ae Editor: Lon Seymour Eloktor san Route Nationale; Le Sea; LP. 52 159270 Balu Franco Estors: D'S Meyer GCP Raederedor! loko: Varian Gmbh Slater Strate 26 5100 Aachen = West Gormany Euitor: £8 Krempetsauer Elakior PE Keraieiaia 14 16673 Vouln Athens Gresee Egor € Xanthoule Pater Treeioelstrast 24 BYO1 VicBeek= the Netnelancts dor: PEL Keresmakors Eleva shop 5 Naseer Pace Usgbela chsh Keraoh9 Pakistan Manager: Zain Abmec Foneirs & Bonto Lea AD Estofaniae 3-1 1060 Usbos-Portgat o Editor: Jaremies Soave \ngeek SA Pla Repubiice Ecuador 228016 Meara Spain Editor: MFerrer Electronic Press AB ‘6c 5508 14105 Hudcinge ~ Sweden Editor: Bil Cedrus nage oars sce pimssen oe pale! Sty owh pert ov oe: psecion Printed at : Trupti Offset Bombay 400 012 Copyright ® 1889 Eloktuur B.V. CONTENTS Editorial Can Britain maintain its lead in mobile radio ... 10.05 Special Features. ‘The weather man speaks 10.06 Project Aristotle 10.08 10.10 Computers — an anti-view ‘Components Anew generation of analogue switches 10.33 om 10.49 ASIC microcontrollers Practical filter design (8) .. 10.62 Computers PROJECT: PC as tone generator 1 10.30 PROJECT: Centronics monitor .. 10.46 General Interest PROJECT: A high grade power unit 10.18 PROJECT: Stereo viewer... 10.26 PROJECT: The digital model train (6) . 10.38 PROJECT: Resonance meter 10.42 Radio & Television ‘Communication receiver front-end filtering, 10.22 Amateur Communication receivers: still a challenge? 10.24 Test & Measurement Simple transmission line experiments .. 10.32 Information, Electronics News .... 10.14 Telecom News 10.15 Industry News 10.16 Guide lines: Corrections ... 10.65 Classified Ads .. 10.66 10.66 Index of advertisers eo inci atone 1960 10.03,Front cover Clear compact dises prior to being metallized are seen during production at Numbus Records Ltd, Britain’s largest manufac- turer, whose development of a new laser-mastering system won the Queen's Award for Technological Achievement in 1987. Producing a cD master with the Nimbus laser- mastering system involves transferring up to 6,000 million bits oF information (secorded sound) on to a prepared glass master. ‘This is then transferred to metal stampers by an elec- tro-forming process. The ses are pressed from clear polycarbonate by fully automated injection moulding presses. CAN BRITAIN MAINTAIN ITS LEAD IN MOBILE RADIO? One of the great success stories in the United Kingdom electronics industry over the past few years has been, and still is, mobile radio. Britain's world lead in this, field has helped to push the number of two-way mobile radios in the UK to well over a million, Cellular radios. although they became available only in 1985, already account for over half that total. And demand keeps growing. But while demand continues to grow, there are increasing shortages of skilled engineers and technicians to produce, install and service the equipment. According to the Federation of Communication Services (FCS), the mobile radio, market is growing at well over 10 per cent per year, while a survey of its mem- bers shows that 90 per cent of them need more technical staff. One industry source estimates that 6,000 more specialist staff will be needed by 1995 ‘There are several initiatives that mobile radio firms should make the most of to demonstrate that mobile radio offers excellent career prospects. These include the Enterprise and Education Initiative, which aims to strengthen the partnership between business and education by offering young persons the opportunity of gaining work experience in both manufacturing and service industries, and teach- ers the chance to experience business first hand. Another effective way of draw- ing school-leavers' attention to the radio industry is through the Young Radio ‘Amateur of the Year Award. This is aimed at anyone under 18 who is keen on Drv radioconstruction or operation, uses radio for a community service, o is involved in amateur radio in some other way, for instance, a school science project. One of the main problems in mobile radio is the lack of nationally recognized qualifications for technicians. Trainees are often attracted to other sectors where structured training exists. The mobile radio industry itself faces difficulties when recruiting technicians of indeterminate abilities. Consequently, mobile radio users suffer because of the varying quality of service they receive. ‘These problems led the Department of Trade and Industry, the Mobile Radio Users Association (Mua), the Federation of Communications Services and the Electronics Engineering Association (EF) to start the Radiocommunications Quality Assurance Scheme, For a company to maintain certification with the scheme, technicians must be properly trained and qualified. Recognizing this, the prt and the MRUA earlier this year launched a joint initiative. This resulted in the Mobile Radio Training Committee (mirc), whose aim is the identification of the mobile radio community's education and training needs. ‘The dialogue between academics and industry is important, Academics have expressed the view that business people should participate in planning courses and helping to provide on-the-job experience. Educators and trainers should be up-dated by working with businesses, having contact with senior engineers and experiencing the use of modern equipment, The activities of the p11, the MRUA, the Pcs and the MRTC are drawing attention to the importance and growth of mobile radio. The United Kingdom currently has a Jeading role, but this position is threatened by the shortage of skilled personnel. ‘The Government is doing much to highlight the career opportunities and alleviate the problems, but the onus must be on business to form a partnership with education. Packages are required that will attract the people needed, in the numbers required, and provide them with the necessary skills. lear ins etozer 969 10.05A HIGH-GRADE POWER UNIT C. Bolton BSc These supplies were developed to power experimental electronic equipment including small RF os jators and amplifiers. There are two versions: a single-channel unit and a dual-channel unit in which the channels may be used independently or in series to give well-balanced positive and negative rails. Various circuits may be used to produce a variable, regulated output voltage: Chopper cireuits In these, the current is chopped into pul- ses which are fed to an energy storage device to givean outputvoltage. This type of circuit was discounted for the present Gesign since the switching involved pro- duces RF energy which readily interferes with other equipment Shunt regulators These circuits produce a larger current than is required, and shunt tne unwanted part away. The shunt regulator is particu- larly wasteful when the required current is much smaller than the available cur- ent, as is frequently the case in ex- perimental work Series regulators These are in essence series resistors that can be varied to maintain a constant out- put voltage. Their inefficiency is highest | Output voltage: 0-25 V fully variable | Output current: 1.50 max. | Guirent limit: 5OmAA.A ‘Output resistance: 2ma ‘Output change for 10% mains change: ensure a small current demand on ICI, Transistors Tsand Ty are connected in parallel with small emitter resistors to distribute heat dissipa- tion. The output voltage of IC) is deter- mined initially by a reference voltage ap- plied to its non-inverting input. The di ot fc i S Fig. 1 10.18 eiateorinaa cabo 1983 Circuit diagram of the single-channel version of the power supply.suman te sanders tetas ‘ne Fig. 2. Suggested construction of the high inverting input is a fixed fraction of the output voltage supplied by the unit. The high gain and diiferential operation of IC) enable the device to vary its output volt- age such that the voltage difference be- tween its inputs is almost zero. ‘The reference voltage for [Cr is derived from constant-current source T) and zener diode Ds. Components Rs and Cs form a simple noise filter. Zener diode Ds pro- duces a smail oif-set voltage to enable the ‘output voltage to go down to zero. Current limiting on the basis of voltage feedback is achieved by Ris, 1C2, To, Two and Ts. The current flow through Rie pro- duces a voltage across the resistor. Part of this voltage is selected by potential divider P2 and Ra, amplified by IC2 and applied toa trigger circuit around Ts and T», Normally To is off, but it is turned on when the output of IC? rises sufficiently because of a higher load current. This causes LED Ds to light, indicating current limiting activity, and Tia to be switched on. Transistors Ts, Tw and Te now act as ‘an amplifier to draw current through Rs, which in turn reduces the reference volt” age to IC and, consequently, the output voltage. Power to operate the reference source and associated circuitry is obtained inde- pendently of the output supply from Tr Br: and Cy, together with stabilizing cir- cuit Ti and Tz. Loading on this supply is le power unit, constant until current limiting occurs. The regulator for this supply thus acts only against fluctuations on the mains, which rarely reach 10%, This enables a steady reference to be obtained fairly simply. Practical points Component layout is not critical, but at- tention must be paid to a number of points, The can of C2 must be well sleeved to keep it insulated from the chassis. The wires carrying the output voltage must be routed such that they do not form loops enclosing other components (this is most likely to happen on the front panel). Ona similar note, the wires carrying the output current must be thick enough to prevent undue heating, and the wire connections at the output terminals must be made exactly as shown in the circuit diagram. ‘As to cooling, Ts and Ty must be mounted on a heat-sink with a thermal specification not exceeding 0.5 K/W. Re- member to insulate these transistors elec- trically from the heat-sink. Transistor requires only a small heat-sink Fuses Fz and Fs are intended to protect the rectifier bridges and the transformers against failure of the smoothing capacitor. ‘They consist of short lengths of 40 SWG copper wire: F: between vero-pins on the circuit hoard, and Fs between tags on a short length of tag strip, which can be mounted anywhere convenient to the transformer leads. Any type of non-steel cabinet may be used fo house the power supply. Steel may be used provided the main transfor- mer has sufficiently small magnetic leak- age to avoid magnetizing the steel near the leads to the inputs of IC2. ‘Constructional deiails of a cabinet that may be made from aluminium are given in Fig, 2. No dimensions are given since these will depend on the components used for Tr, C2 and the heat-sink. The L-section is extruded aluminium, which is available from many DIY suppliers. Setting up ‘The setting up procedure is concerned en. tirely with the current limit facility. 1. With the unit switched off, set the out- put voltage control, Pr, for zero volts, the current limit control, P2, for maximum current (maximum resistance), and Ps to zero resistance. 2. Connect a resistor of about 10 Q, ca- pable of carrying 1.5 A, across the output terminals (a length of electric fire spiral hhas been found useful). 3. Switch on the unit and raise the output until a current of 1.5 A flows. 4. Adjust Ps so that the current limit warn- ing light, Ds, is just on. 5. Increase the resistance of Ps until the letor nls ocr 1989 10.19current drops by between 50 and 100 mA. as indicated on an ammeter. 6. Reduce the output voltage to zero and check that the warning light goes out. 7. Raise the output voltage and check that the warning lamp comes on at 1.5 A. 8. Try to raise the current by raising the output voltage or reducing the load resis- tor, and check that there is little rise in output current. 9. Choose other settings of the current limit control, and. check that limiting oc- curs at lower currents. The lower limit should be between 30 and 50 mA. 10, If at any time the current limit indica- tor lights, but at less than full brightness, the limit circuit oscillates because Ps has been advanced too far and should be re- adjusted. This is best done by reducing its value to zero and repeating operations 3, 4and 5. ‘The current limit control can be calibrated by setting it to maximum, adjusting the output current to a value required as a calibration point, and then adjusting the limit control until limiting just occurs as indicated by the lamp coming on, Notes on the use The output of the single-channel unit is, floating so that either side, or none, may bbe grounded. The high degree of regula- tion is available only direct at the output terminals of the supply: bear in mind that six inches of ordinary connecting wire have a higher resistance than the output resistance of the unit. Under near short-circuit conditions, the current limit may produce a low-level oscillation on the output voltage. This is dependent on the reactance of the load, and is unlikely to be of any consequence since the supply is not normally used asa constant-current source. Dual-channel unit In the dual-channel unit, channel 1 is es- sentially the same as the single-channel unit. The modifications are the addition of a fine voltage control, Ps,a second current limit amplifier, ICs, which is operational only in the balanced mode, and a dis- charge circuit, Tu, Tz and Tis, which dis- charges Ce when the voltage setting is reduiced, enabling the output to follow the setting closely. ‘Channel 2s similar to channel 1 except 'OHP Ls. ‘Auxillary circuit for adjusting the Fig. 4. PSU. that it is complementary. For ease of fol- lowing, the circuit components with an identical function in channel 1 and the single-channel version are given the same reference numbers. Likewise, compo- nents in channel 2 serving the same func tion as those in channel 1 are given the same numbers with prefix ‘9’. Thus, [Ci of channel 1 becomes ICs) of channel 2. The complete circuit diagram of the dual- channel power supply is given in Fig. 3. The discharge circ! As the voltage setting is reduced, the out- put of ICi falls, anc will fall below the output terminal voltage unless Ci is di charged. The output voltage of [Ci is d veloped across i via emitter followers and Tit. Diode Dio produces a small volt- age to compensate for additional base- emitter deop in Darlington transistors Te and Tz, If the voltage across Ro is lower than that across Cs, Ti2 is turned on. This in turn switches T13 on, which discharges G until the voltage across it is almost equal to that across Ris when Tz turned off. Components Dia, Dis and Ros limit the base current in Tis fo a safe level. Diode Du prevents the base of Tis being driven dangerously positive if the voltage setting is raised suddenly. Balanced output mode In the balanced output mode, the oper ation of channel 1 is unchanged. In chan- nel 2, the reference voltage is obtained from the channel 1 reference via the ‘simes-l’ amplifier, ICs. This reference is compared with %4 of the voltage between the positive and negative rails produced by potential divider Rse-Roo Ifthe current in channel 1 exceeds the set limit, ICz causes the limit circuit to operate. If the current in channel 2 ex- ceeds the limitsetting, the output from ICs causes the limiter in channel | to operate, Since both channels use the channel 1 ref erence, they are limited equally in both cases. Hence, balance is maintained under current limiting conditions. Diodes Ds and Ds prevent competition for limiting between the channels. The current limit settings of the two channels are inde- pendent. Switching between modes of operation is accomplished by S:, which is a wafer switch made up of two 6-pole, 2-way wa- fers, Relay Re1 is operated by Si to switch the output current. Current for the relay coil is obtained from the channel? AC supply via Dis and. Cis. This supply also feeds D:, the ‘power- on’ indicator. Setting up procedure With the unit set for independent channel operation, set the current limit circuits as described for the single-channel unit. Use Prand Ps for channel 1, and Psa and Pus for channel 2, To adjust the balance, either a digital voltmeter capable of resolving millivolts at 25 V and below, or the auxiliary test circuit shown in Fig. 4, is required. The PSU must be switched on at least five minutes before the balance is adjusted. Turn S2 to balanced operation. Set channel 1 to about 10 V and adjust Pr so that channel 2, now the negative rail, also supplies 10 V. Setting up with aDVM 11. Set the output voltage to about 19 V with the aid of the channel 1 control. 32. Connect the digital meter to the + and terminals. Note the reading. 13. Connect the digital meter to the + and — terminals, Adjust P? to give the reading obtained in step 12 14, Reconnect the digital meter to the + and + terminals. Reduce the output volt- age to 1.3 V and note the exact reading. 15. Connect the digital meter to the + and ~ terminals. Adjust Ps to give the reading obtained in step 14 Setting up with the auxiliary test circuit 11, With the 18 V battery in the test circuit and the multimeter on the 25 V range, con- nect point X to the + terminal, and point ¥ to the + terminal. Adjust the output volt- age so that the multimeter reads zero Change to 100 mV and adjust the output voltage to give a multimeter reading of 50 mV. 12. Set the multimeter to the 5 V range. Connect X to the + terminal, and Y to the = terminal. Adjust P? until the multimeter reads zero, Change the multimeter range to 100 mV and adjust Pr to give a reading of 50 mV. 13. Disconnect the test circuit from the unit. Replace the 18 V battery by the 1.5 V cell in the test circuit. Reduce the output to about 2 V and set the multimeter to the 5 V range. Connect X to the + terminal, and Y to the + terminal. Adjust the unit until the multimeter reads zero. Change the multimeter range to 100 mV and ad- just the output voltage to give a reading, of 50 mV, 14, Set the multimeter to the 5 V range Connect X to the + terminal, and Y to the = terminal, Adjust Ps so that the multimeter reads zero. Change the multimeter range to 100 mV and adjust P+ to give a reading of 50 mV. Further settings common to both meth- ods: 16, Repeat steps 11 to 15. 17. Repeat steps 11, 12 and 13. If any ad- justment of Py is required, steps 14 and 15 must be repeated, followed by steps 11, 12, and 13 and so on until no further ad- justment is required. 18. Connect the 10 © resistor used for set- ting the current limit to the + and — termi- nals. Set the channel 2 current limit control for maximum current, and adjust Ps 50 that the channel 1 limit warning Jamp just comes on when the current in channel 2 (the negative rail) reaches 1.5 A. too indi onoder 1982 10.21COMMUNICATION RECEIVER FRONT-END FILTERING In communication receivers, whether intended for general coverage or for ama- teur bunds only, front-end design has changed considerably over the years. With the use of higher intermediate frequencies (ir) and the availability of high-frequency (ir) crystal filters, we no longer see the ‘multiple banks of tuned circuits and multi- gang capacitors Unfortunately, for most new develop- ‘ments there is a price to pay: the reduction in pre-mixer selectivity means that any amplifier preceding the mixer must offer superlative performance in terms of inter- modulation distortion and cross modula- tion. If it does not, the user may get the impression that the receiver is full of sig~ nals. ‘The old saying that “The wider the window's open, the more muck blows in” is very apt here 1 was with these thoughts in mind that the writer has designed some general-pur- pose front-end filters for the amateur bands. If you need more protection up front when Joe Bloggs just down the road fires up his 400 watts of sideband, these filters should help you to listen on the next adjacent band up or down, You may wish to incorporate them in your next receiver. What kind of filter? Frequency filters fall into four categories: low-pass (L2), high-pass (iP), band-pass (B®), and band-stop, ‘The design of a band-pass filter for tel- atively small bandwidths is not too diffi- cult, but the difficulty increases exponen- ly with increasing bandwidth! Band-pass and bund-stop filters may be constructed from a mix of low-pass und high-pass sections. In ap filters, these sec- bband-stop filters they are in parallel. The band-stop filler so con- structed is not often seen in print, but i nevertheless, a thoroughly practical design. It is, of course. a pity that the LP and HP sections can be used only for the construction of a band-pass or a band-stop filter, but not for both simultaneously! In modem filter design, « number of approximations to the ideal brickwall response have become popular. The low- pass responses of these are shown in Fig. 1. Their high-pass response is ‘obtained by network transformation, 10.22 eter ince october 1989 by A.B. Bradshaw Very flat pass band. Attenuation continues to e in stop band. Simple to set up. Very poor pass-stop band transition sition, ‘ Equally spaced ripples in pass band. Attenuation ‘continues to increase in stop band. More difficult to set up than Butterworth. Good pass-stop band tran- Unequally spaced ripples in pass band. Attenuation (minimum) is defined in stop band. Ripples in stop band. More difficult to set up than Butterworth. Very ag {good pass-stop band transition. Fig. 1. Froquency response characteristics of the ideal low-pass filter and three approximations, The operating impedance, band edge, attenuation in the stop band, pass-band ripple and component values are all de~ rived from a low-pass section normalized for a frequency of | radian and an impe- dance of 12. ‘The shape of the response, which determines the complexity (length) of the finished filter, is decided with the aid of ign tables. There is usually a trade-off between the ratio of the band-edge fre- ‘quency to the design attenuation frequency and the stop-band attenuation. This means that the “squarer” the response of a given filter is, the lower will be the stop-band attenuation, In the construction of a ar filter, the band edge of the tp section becomes the upper profile and that of the 1p section, the lower profile. In effect, the two res- ponses cross over each other. In the designs illustrated in this article, the elliptic function approximation is used With this, the minimum stop-band attenua- tion remains at its design figure, in con- trast to Butterworth or Chebishev func- tions where it increases the further the fre- ‘quency is away from the band edge. This is, however, a small price 0 pay for the excellent transition band selectivity of this type of filter, ‘The filters discussed here are designed for a stop-band attenuation of 40 dB or 80 dB to meet both light and stringent requirements. Also, they are designed for an input and output impedance of 50 Q. Although intended primarily for receiver applications, they may, of course, be used in transmitters, in which ease the compo- rent ratings MUST BE UPGRADED! Components Ideally, the filters should be constructed on @ printed-circuit board, but this is not essential. Capacitors should be low-loss types. They should be connected in parallel t0 get their tolerance within 1%, although sil- ver-mica capacitors with 1% tolerance are readily available. The Q of the inductors should be as high as can be obtained. However, as the filter impedance is 50 2, the values of inductance are low, s0 the coils can be wound manually quite easily. Take care to prevent inductive coupling berween sec- tions. When setting up the filter, trim the coils to their correct value by checking the stop-band nulls on an oscilloscope (or analyser if you are that lucky!). Check all frequencies with a suitable counter.Fig 2. Band-pass fier for the top band. The ~1 dB edges are at 1.8 MHz and 2.0 MHz. The pass band ripple is 1 dB. The -40 dB points are at 1.479 MHz and 2.494 MI The frequencies of infinite attenuation are at; LF 1.025 MHz and 1.44 Miz; HF 25 MHz and 3.51 MHz, #ptpre fe a - Fig. 4. Band-pass filer for the 80 m band. The -1 dB edges are at 3.5 MH2 and 3,8 MHz. The pass band ripple is 1 dB. The -40 dB points are at 2.875 Miz and 4.624 MHz, The frequencies of infinite attenuation are at: LF 2.8 Mz and 1.994 Miz; HF 4.75 MHz and 6.669 MHz, ope ce | ee | ) aA pire | re | es es /ERERU EEE: Fig. 3. Band-pass fiter forthe top band. Attenuation at 1.8 MHz and 2.0 MRz is 0.18 dB, The pass band ripple is 0.18 dB. The -80 dB points are at 3,178 MHz and 1.132 MHz, The frequencies of infinite attenuation are at: LF 0.9269 Miz, 1.1106 MHz and 0.54202 MHz; HF 3.88 MHz, 3.241 MHz and 6.641 Mi ier Fig. 5. Band-pass filter for the 80 m band. Attenuation at 3.5 MH2 and 38 MHz is 0.18 dB. Pass band ripple is 0.18 dB. The ~80 dB points are at 2.202 MHz and 6.038 MHz. The frequencies of infinite attenustion ar at: LF 1.802 1.053 MHz, 12.619 MH2, Miz and 2.159 MHz; HF 6.158 MHz, 7.378 MHz and Fig. 6. Bandpass filer for the 40 m band. The ~1 dB edges are at 7.0 MH ‘and 7.2 MHz, The pass band ripple is 1 dB. The -40 4B points are at 5.761 Miz and 8.762 MHz. The frequencies of infinite attenuation are at: LF 5,988 MHz and 5.6 MHz; HF 9.0 MHz and 12.63 MHz. Fig. 7. Band-pass filter for the 40 m band. Atienuation at 7.0 MHz and 7.2 MHz is 0.18 dB. The pass band ripple is 0.18 dB. The -80 dB points are at 4.405 Miz and 11.44 MHz. The frequencies of infinite attenuation are at: LF 2.407 MHz, 3.604 MHz and 4.319 MHz; HF 11.668 MHz, 13.961 MHz and 23.91 Mb. {IF Fig. 8. Band-pass filter for the 20 m band. The ~1 dB edges are at 14.0 MHz ‘and 14.2 MHz, The pass band ripple is 1 dB. The ~40 dB points are at 11.50 MHz and 17.28 MHz. The frequencies of infinite attenuation are at: LF 7.977 Miz and 11.2 MH; HF 17.75 MHz and 24.92 MHz, Thre i Fig. 10. Bond-pass fier forthe 10 m band. The -1 dB edges are at 28 Miz ‘and 30 MHz. The pass band ripple is 1 dB. The 40 4B points are at 23 MHz and 36.51 MHz. The frequencies of infinite attenuation are at: LF 15.954 MHz and 22.4 MHz; HF 37.5 MHz and 52.65 MHz. Fig. 9. Band-pass fitter for the 20 m band. Attenuation at 14.0 MHz and “4.2 Mz Is 0.18 dB. The pass band ripple is 0.18 dB. The -80 dB points are at 6.810 MHz and 22.564 MHz. The frequencies of infinite attenuation are at LF 4.215 MHz, 7.209 MHz and 6.636 MHz; HF 29.01 MHz, 27.57 MHz and 497356 Ma, Arar Tyo so 2 = a ‘ eo 2 ht ime ° Fig. 1. Bandpass tite or he 10m band Allenuaton at 28 ean 30 MHz is 0.10 dB. The pass band ripple is 0:18 dB. The ~80 dB points aro at 17.62 MHz and 47.6 MHz, The frequencies of infinite attenuation are: LF 1849 MHz, 14.419 MHz and 17.277 MHz; HF 48.619 MHz, 58.254 Miz and 99.625 MHz, ‘shor ina ocobr 1888 10.23AMATEUR COMMUNICATION RECEIVERS: STILL A CHALLENGE? The valve era Over the past forty years or so, communi- cation receiver design has undergone quite a revolution, In the days before transistors and ics, there were some remarkably good receivers around. Typical among these were the ARS8, the Hamerlund Super-Pro, the Marconi CR10O, the BC348, and the Racal RAI?. After the end of the Second World War, many radio amateurs were using either ‘one of these classical designs or one of the many ex-military receivers that had come ‘on to the surplus market. A large number of amateurs showed ‘great ingenuity in the use of various items of military equipment to make up their sta- tion receiver, and sometimes their trans- miter as well. There was a lot of ex-ser- vices expertise about and a considerable amount of technical discussion seemed to take place over the airwaves. Cobbling together all this readily obtainable gear was not entirely caused by the non-avail- ability of proprietary amateur equipment: most of us being broke had something. to do with it as well! ‘Towards the end of the valve era, there occurred a number of technical develop- ments in radio valve technology that had direct bearing on communication receiver design. One of these was the appearance of the frame grid pentode, like the E183. These new valves, 465 kHz IF trans- formers with @ good Q, and ex-govern- ment quartz crystals, such as the FT241/243, helped to achieve respectable IF response shapes for reception of the increasingly popular single-sideband (838) transmissions. ‘AL the same time, wide-range, stable aintomatic gain control (AGC) was becom- ing the norm, its control voltage no longer derived from the incoming cartier. ‘The emergence of the long-life stable double triodes, like the E88CC, originally developed for the then embryonic compu- er industry, further helped to improve amateur communication receiver design. Another milestone was the introduction of the beam deflection mixer valve, like the 6ARS and the 7360, which were devel oped for the American colour tv market. The remarkably linear mixing and large- 10.24 iets by A. B. Bradshaw signal handling capabilities of these new valves soon caught the eye of receiver designers and it did not take long before manufacturers like Collins, Squires- Sanders. Drake, and so on were incorpo- rating them in their new receivers, At about this time, a superb receiver, the Thornley G2DAF design, appeared on the UK amateur scene, Many of these excellent receivers were built and had a profound influence on our thinking of what kind of performance could be achieved with the technology then avail- able. I built my own and well remember the pleasure of using the receiver. which had the knife-edge selectivity of the Kokusai mechanical filter Type MF4SS. 10K. By then, we had the ingredients neces- sary for meeting the specification for a ‘z00d communication receiver: + good iF shape factor (in spite of the low te resulting from the multi-conversion necessary for the He end) + stable conversion oscillators, necessary for the increasingly popular ss8 mode of transmission; + ease of tuning with mechanical s/s drives (Edddystone 898, and so on). Nevertheless, these receivers still had some serious short-comings. They were complex (at the time); they usually embodied lots of ganged switching of tuned circuits; they used relatively expen- sive wound components; their front-end alignment and tracking, particularly in general coverage designs, was difficult; and lastly, these ‘magificent machines* could certainly not be regarded as portable. The solid-state era The transition to solid state electronics was not a sudden occurrence, and for some years hybrid designs were very pop- ular in the amateur press. Although these designs still used valves in their front- ends, much of the remaining circuitry had become solid-state. These early solid-state devices, however, could not produce the good intermodulation and cross modula- tion performance of their valved predeces- sos Over the past decade, solid-state devices have improved enormously, how- ever, and present-day communication receivers have very real benefits compared with those of yesteryear Unfortunately, in my view, we have allowed the Japanese industry to dominate the manufacture and design of good-quali- ty communication receivers. This is partic- ularly disappointing in view of our own earlier performance. In the solid-state era ‘we have managed t0 produce some inno- vative designs, but they are few and far between. Nevertheless, the radio amateur re- mains in a unique position. The receiver manufacturer is hamstrung by severe eco- nomic restraints and market forces. The amateur designer and constructor, on the ‘other hand, is still at liberty to explore and indulge his fancy in ways that would be ‘out of the question for the professional designer. [ am not suggesting for one mo- ‘ment that the radio amateur can challenge the Japanese giants, Nevertheless, there is still much innovation in Britain, well doc- umented in a variety of books, technical articles, application notes, and so on, Modern home construction If we regard the modern communication receiver at a system level, we have a good ‘opportunity to see what some British man- ufacturers and suppliers have on offer RF amplifiers: Plessey Types SL600; SL61IC; SL612; SLI610C; SLISIIC: SLIGI2C. High performance mixers: Plessey Type SL6440A/C (+30 dBm intercept point); Siliconix Type Si8901 double-balanced mixer (+35 dBm intercept point): vari diode bridge ring devices, from the ‘MD108 up to the SRA3 (£28 from Cirkit) 1 shaping filters: ceramic and mechani cal filters are available for the lower 1's (455 KH), while for the higher 1Fs there are quartz crystal lattices up to 10.7 MHz are available in bandwidths suitable for 388 and Cw from Cirkit 1 amplifiers: three Plessey Type SL612 ics will give most of the gain required in a normal iF amplifier. Demodulators for aM, ssB, and cw: Plessey Types SLO700A and SLO24 AGC generators: rather a limited choicehete, but the Plessey SL620 and SL62IC Ics are well proven. ‘This list shows that there is a good home-bred range of building blocks although I stil feel that there are areas of design that have been neglected. Some of these are receiver frontend filtering for the amateur bands, local oscillator design (cither upper conversion synthesis or lim- ited-range Bro conversion systems), while the required noise floor specification for ‘iF synthesizers isa real challenge, Conclusion As I glance through yesteryear copies of RSGB Bulletin, RAD COM, and others, 1 can not but be struck by the falling off in interest in innovative design. Can this malaise be halted? 1 certainly hope so. What are you going to do about it? References, ‘Communication Receivers” by G.R.B Thornley. RSGB Bulfetin, July-Now 1960 and March-April 1961 ‘An Amateur Bands Communication Receiver” by A.J. Shepherd, RSGB Bulle-tin July 1963 Prelude to a Communication Receiver” by 1 Pouson, Radio & Hobbies (Australia) Sept. 1964 (2 parts) “The Deltahet Mark 2 Solid State Version” by I. Pogsen, Radio & Hobbies (Australia) Feb, 1971 (in 2 pars) 10-80 Metre Amateur Transceiver” by D.R. Bowman, Wireless World, lune 1 “Defining and Measuring Receiver Dyna- mic Range” by W. Hayward, OST, July 1975, High Dynamic Range Receiver Input Stages” by U.L. Rhode, Ham Radio, Oct. 1976 “Receiver Noise Figure, Sensitivity, and Dynamic Range: What the Numbers Mean” by J. Fisk, Ham Radio, Oct. 1975, “Optimum Design for HF Communication Receivers” by U.L. Rhode, Ham Radio, Oct. 1976. IF Amplifier Design” bs Ham Radio, March 1977. “Noise Blanker Design Ham Radio, Nox. 1977. Etfects of Noise on Receiver Systems” by UL. Rhode, Ham Radio, Nov. 1977. “The PW Helford HF SSB Transceiver” by V. Goom, Practical Wireless, Nov. 1980 (in 6 paris). “The RX80 Mk2" by A.L Com, Jan, 1981 (in 6 parts). “A Dual-Conversion Multimode Receiver IF/AF Strip” by S. Niewiadomski, Rad Com, May 1985 (in 2 paris). A Home Built Frequency Synthesizer for 45-75 MHz” by J. Crawley, Rad Com, August 1986 (in 2 parts), ULL. Rhode, by W, Stewart Bailey, Rad W PRODUC Thick Film Resistor Arrays (DIP) Honest (YEC) Ine., Japan, offers Dip- ped Resistor Networks Dual in Line Pac- kage (DIP). As these are dipped compo- nents, they are cheaper when compared to moulded ones, Circuits are available in Isolated, Bussed and Dual Ter- minators, These arrays have a pitch of 2.54 mm and hence compatible with standard I.C. sockets, Power ratings of- fered are 0.063 W, 0.125 W and 0.25 W. Resistance tolerances offered are +20%, +10%, +5% +2% . Resis- tance range is from 50 ohms to 1 M ohm, T.C.R. available are 300, 250 and 200 ppnvC. Operating temperature range is from -55 Cto +125. Hi-Tech Resistors Pvt. Ltd. © 1003/4, Maker Chambers ¥, Nariman Point © Bombay-400 021 € Contact Cleaner ACCRA PAC (INDIA) PRIVATE LTD. in collaboration with Accra Pac Inc, USA, have introduced the SAFEGUARD Contact Cleaner, for electronic maintenance. ‘The Contact Cleaner is a specially for- mulated solvent which restores electrical continuity of all types of contacts and controls. Pure solvents under high pres- sure quickly penetrate the surface pores removing grease, dirt, oil and surface oxides, and evaporate quickly leaving behind clean contacts. It has excellent dielectric properties and improves per- formance and reliability of all electronic equipment, Non-flammable, non-toxic the Cleaner is useful for silver/precious ‘metal contacts, TV turners, miniature controls, solenoids, circuit breakers, potentiometers, selector switches, vol- ume and tone controls, relay contacts, thermostat controls, distribution panels and other electronic/electrical contacts. ACCRA PAC (INDIA) PRIVATELTD @ 917, Raheja Chambers @ Nariman Point © Bombay-400 021 Vinyl Hoses Udey Cables are manufacturing Parmyf= lex Flexible Vinyl Hoses for various ap- plications like electrical conduits in buildings, machine tool wirings, dust and rags collection hoses for textile machin- ery, Vacuum cleaner hoses, gas and fume removal, dust extractor for wood working cte. Reinforced with steel wire to ensure resistance to crushing forces and development of kinks the hoses are available in diameter 10 to 60 mm for medium duty application (Type SF) and from 60 to 200 mm for heavy duty appli- cations (Type MSF). Other sizes availa- ble against specific orders Udey Cables Clo. Jafkay Lights ¢ Dina Building ¢ 52M. Karve Road © Bombay- 400 002 © Tel: 314622/310870 © tage ndia erober 289 10.25,STEREO VIEWER This electronic ornament is ba: C.J. Ruissen & A.C. van Houwelingen lly 2n unconventional VU-meter. A ‘square matrix composed of 1010 LEDs indicates signal volume as ‘The circuit is perhaps best qualified as a simple X-Y display for audio signals, and the displayed patierns are, therefore, not unlike Lissajous figures. The heart of the circuit is formed by an integrated circuit from National Semiconductor, the Type LMB9L4. At first glance, this dot/bar dis- play driver is a quite conventional design. The IC houses ten comparators, a preci- sion linear-scale voltage divider and a ref- erence voltage source. The actual realization of these parts, however, gives the LM3914 a number of interesting fea~ tures: + outputs drive LEDs, LCDs, fluorescent displays or miniature bulbs + external input selects bar or dat display mode simple to cascade for displays with a resolution of up to 100 steps + intemal voltage reference; adjustable be tween 1.2 and 12 V ‘+ minimum supply voltage: 3 V + current-regulated open-collector out- puts + output current programmable from 2 to 30mA + no multiplex switehi + input withstands +35 V + outputs interface direct with TTL and CMOS logic + floating 10-step dividercanbeconnected to a wide range of voltages, including, internal reference Circuit description ‘The circuit diagram of the 1010 LED ma- trix which determines the appearance of the stereo viewer is given in Fig, 2. The dimensions of the matrix result in asquare arrangement. How the square is actually positioned is a matter of personal pref- erence, and not, of course, of any circuit configuration. The introductory photo- graph shows the prototype which has ma- trix co-ordinate X1-YI below and X10-Y10 at the top. The matrix arrangement allows any one of the 100 LEDs to be turned on and off individually. To select a particular LED, the relevant column, X1-X10, and row, YI-Y1O, is made high and low re- spectively. The circuit diagram of the row/column driver (Fig. 1) shows that two LM3914s are used: IC2 forms the col- umn driver (X-axis), and IC> the row Griver (Y-axis). Both LM3914s are set to 10.26 etetiorinss october 1980 well as stereo information. eS operate in the dot mode so that, strictly speaking, one row and one column are selected to light one LED at a time. The IC ouiputs have some overlap, however, so that two LEDs are on at the switch-over levels. ‘Transistors T2Tn function as inver- ters. They are required because the col- umn driver must switch to the positive supply rather than to ground. The pro- grammable current source in ICs is set to supply the relatively small base currents for the inverter transistors. The current source in IC2 is set toa much higher value to supply the required current direct to the LEDs. ‘The current source in the LM3914 is set in a rather unconventional manner: the ouiput current is ten times the current supplied by the reference voltage. So, all that is required is to load the reference with a resistor. Rit sets the output current of ICs to about 2 mA. A slightly different approach is used in the case of ICz: here, an LDR (light-dependent resistor), a tran- sistor, Ts, and a handful of other compo: nents form a load resistor whose value is 2 function of ambient light intensity. Since the output current of IC2 is used for driv- ing the LEDs, the display intensity isauto- matically controlled as a function of ambient light conditions. The component values used allow the LED current to vary between 8 and 25 mA ‘To make sure the LEDs are completely off when they have to be off, the LT out- puts of [C2 and ICs are fitted with a pull- up resistor. This is required because the TH output has an auxiliary current source that is used for cascading, driver chips to form a larger display. The pull-up resis- tors keep Tz from conducting, and oneT2711 = 10x BC559B AN,A2 = 161 =LM358 Fig. 1. Circuit diagram of the stereo viewer. . i 8 stocor na osaber 12 10.27> D1..0100 | eI Le Efe Bee a sel e ks aaparat att at | cies | | | Fig. 2. Matrix configuration with 100 LEDs. LED in the matrix from lighting, when the TT otitput is not actuated. The audio signals applied to the stereo aid of bias vol viewer are first attenuated to enable the drive levels for ICs and ICsto be set accur- ately. The sensitivity of the circuit is set jotentiometer Pi. Acceptable drive 10.28 steer naa ecooer 198 at the inputs are between 45 mV requir The zero point of the matrix is shifted to the centre of the square display with the es on to which Fig, 3. Track layout and component mounting pian. ‘a90084=92 hai the AF adjusted to supply hall oltage, A voltmeter is not for this adjustment, because the tel indication cane seen to shift tothe | -~ ee || Resistors (25%): RucRaRta = 10k Rise 1k5. RisiAte = 2k2 Ris= LOR Ke | | Re= 5600, Rio = 1h R= 15k. PX = 100k logarithmic potentiometer; ‘1Mo1 muitturn preset Pa Capacitors: rie =220n CaiG5;010;C12 = 100n Cam 47H; 10 0 = LED; cla. 5 mm ‘= BC547A ‘TeTi1 = BOSSOB ICs = L358 IGeiGs = LM3914 | Ce = 7805 | Miscellaneous: Fr = 180 mA fuse with PCB-mount olde. ‘S) = SPST mains switch ‘socket. pin header 2x10 contacts. Ks 2:way PCB terminal block. Ks = IDC header 2x10 contacts. PCB Type 690044centre of the display. ‘The circuit is powered by a conven- tional regulated 5 V supply, which fitted on to the printed-circuit board together with the associated mains trans- former. Construction: simple ‘The printed-circuit board shown in Fig.3 accommodates all parts except the LED matrix and the LDR for the display intens- ity control. Populating the PCB is entirely straightforward if the wire links are in- stalled first ‘The LED matrix is built separately on a square piece of veroboard. The installa- tion of the LEDs and the lozenge-shaped wiring at the rear of this board are greatly simplified when the matrix is turned 45° with respect to the hole pattern in the board, The LED matrix is connected via a short length of flat-ribbon cable, for which a mating 20-way pin header, Ks, is pro- vided on the main board. The stereo viewer is simple to align: simply adjust P2 and P) until the centre four LEDs in the matrix are on. The sensi- tivity can then be set as required with the aid of the volume control, P1 ieee W PRODUCTS Digital Multimeter PLA has developed the DM-20A a digi- tal multimeter. Having an LCD display with a resolution of 1 ouV on 200 mV range in both ACI DC models. It has an accuracy of 0.1% Maximum voltage measurable in DC ranges is 1000 V and 700 V rms in AC range. It has a resolution of 10 nA on 200 uA range in AC mode. It has wide fre- quency range of 20 KHz. in AC voltage and is battery operated. PLA ELECTRO APPLIANCES PYT. LTD. ® Thakor Estate © Kurla Kirol Road © Vidyavihar (W) ® Bombay-400 '5132667/5132668/5133048 © Photoelectric Fork Switch Electronic Swtiches, have developed Photoelectric Fork Switch also knows as Slot Sensor or Grooved Head Sensor. This is one piece device containing infra- red light emitting diode, photo transistor receiver an amplifier. A solid state con- struction give ita long maintenance free life. Requires 10-24 Volts DC supply is protected from reverse polarity connec- tions. Output is indicated by LED and is available through PNP/NPN transistor with light or dark switching modes, Ap- plication includes mark detection on transperant foils, Edge alignment, space detection on toothed wheels, position 12, for machine tools controls, other processing machinery etc. Electronic Switches (Nasik) P. Ltd. 1, Nabush © Gangapur Road © ‘Nasik-422 005 © Tel: 0253-78452 toto nin eter 1989 10.29)PC AS TONE GENERATOR A GW-BASIC program and a few modi J. Schiffer DL7PE tions to the loudspeaker circuit enable any PC, whether an XT, AT or compatible, to tunction as a precision tone generator with a frequency range of 20 Hz to 120 kHz, with a basic sweep function as a useful option. The nice generator is that it costs next to nothing, while thing about t! ‘The present PC tone generator, which is really a BASIC program only, is ideal for aligning a wide range of AF circuits, The frequency of the generated tone can be set accurately, so that the low-cost tone gen- trator is suitable for applications that in- clude the tuning of musical instruments (electronic tuning fork), the aligning of RTTY, fax and SSTV filters, and the dimensioning, and testing, of many other types of tone decoder. In many cases, the BASIC program obviates the useofa fanc- tion generator and a frequency meter. This is of particular interest for applica- tions in the audio range, where frequency meters are, in general, not very accurate. The PC tone generator allows AF frequen- cies to be defined with an accuracy of a fraction of a hertz PC as tone generator Apart from the possibilities offered by BASIC commands BEEP and SOUND, there exists a more powerful way of generating tones with the aid of a personal computer: direct control of the relevant hardware. ‘This enables frequencies to be generated at quartz-crystal stability in the range from 20 Hz to several hundred KH, inde pendently of the PC's clock frequency. ‘The lower frequency limit is fixed, but the upper limit can be made as high as allowed by the PC’s internal AF amplifier. The relevant BASIC commands may be found in lines 260 through 330 of the list ing ‘The frequency resolution is excellent, especially in the audible range: at a basic frequency of 10 kHz, the step size is as small as 85 Hz, oF 0.85%; between 2 and 3 kHz, the step size is 5 Hz (0.16%); and below 1 KHz it is 0.1 Hz (0.01%), ‘The PC generates the required tone via the built-in loudspeaker. This is adequate for nearly all calibration and adjustment work in the acoustic range. An oscillator, for instance, is simple to calibrate accur- ately by means of a beat-frequency meas- urement in which the PC functions as the reference. Just compare the two tones by listening to them simultaneously, and step the PC tone frequency until the dif- ference frequency decreases. When it becomes inaudible, the frequency gener- 10.30 etstorindia coder 1908 doubling as a frequency meter. ated by the equipment under test can be read from the PC screen, Similarly, the PC tone generator can be set to a particular frequency, so that the oscillator can be adjusted until zero-beat is achieved jing the PC’s AF signal with the aid of a small amplifi If the generated tone is required elec- trically also, the loudspeaker signal must be madie available on a jack socket — see Fig. 1. When a plug is inserted, the loud- speaker in the PC is automatically dis-abled, and the generated tone is available at a relatively low impedance. The 8 Q resistor protects the internal AF amplifier against short-circuits, The value of this resistor must be increased as required if the internal loudspeaker i a high-imped- ance type. It is, of course, also possible to wire the socket such that the loudspeaker isnot disabled, but taken up in series with the output signal. This arrangement obvi- ates the use of the protection resistor, By connecting a 16 Q resistor instead of the indicated 100.9 type to ground, the gener- ated tone is simultaneously audible via the internal loudspeaker. ‘A further possibility is shown in Fig. 2 A small amplifier with adjustable volume is connected to the jack socket, This solu- tion is particularly useful for PCs that have an internal loudspeaker with a rela- tively high impedance, or one that pro- duces insuificient output volume. The program ‘The frequency range of 20 Hz.to 120 kHz. is fixed in lines 180 and 200 of the the BASIC program. Keys are used to control the program: Key ‘e's enable tone Key ‘4 disable tone Key ‘+": increase frequency by previously eniered step size Key ~’: decrease frequency by previously entered step size Key ’s': terminate program A frequency sweep is obtained by holding the + or - key — the tone frequency then increases or decreases at the previously entered step size. Applications Here are a few of the many possible appli- cations of the computer-controlled tone generator: + test signal for aligning RTTY circuits, eg, 1275/2125 Hz. for VEF stations, and 1275/1445 Hz for SW stations. test signal for tone decoders 1,000 Hi frequency reference tuning fork elementary acoustics Table 1 is useful for the tuning fork appli- cation because it shows the tone irequen- cies for three octaves. Table 1. Commonly used frequencies for tuning musical instruments. 30 cus .tky OFF 28 osu 380, 0 Pras cPuina JaNFUr * Flssue onter stepwise 7 sre 128 couok 38.0.0 2s iocae 9,23. PRE ~ . 13s tSeare 2é,25\ emi" 1 Feoueney “patee. #4" PhG0; "LocaTe 10,59:°R1Nt ; 125 Locate 40°80 “PRIME 17 Secaneu? $0) va THEN FREO. 160 {F fneaeoss0000! ‘MEN FRED-1200001 + cosuB 260 180 1p See So TEN PAG FRED ~ GIP. Eig Up xen sor ox nese” THEN GosuS 620 20 13 uss a" On xes"o" THEN GOsus 60 350 fe Sas am Bn fiscar SEW 9509 G60 . GoTo 250 25 Our é7'tes fa sled 192 from ctzer biock 3be ter Coinmssissito! sieo RIM "aonpute cata for tixer block” bg Ler exmmssana (coust/3e0) "REM aone-eignifacont byte” 3b Ler entuosinriGount - elaHz"256) “ABW *ieant-oienificant byte 320 OUT e6,GWTLO REM “supply least-esenteteant by 330 out seleqii snaM “supply nortsnigniticant byte 3eo Ratu Sep Sein orcia7:"T ONE GENERATOR * 35s paint SRCCSa by SLPS print? @ Peis") a» couon 7.0 | Sout 7,0 tosare 2.26 3 GGT 97.2NeC97) OR 2 REN turn on PC ioudspesker Reruew CUT 87, 1NP(S7) AND 252 85M turn off FC loudapeeker Note 4th octave | 5th octave Gthoctave ore 261.6 iE 523.3 1048.5 or ara sad [> | aea7 | 587.9 [ 0» ain “sea, sal [= 205 SNS F 48.2 : = [re 2700 [es 020 a ee A 00 5 at | 466.2 | | H 493.9 ES eco ini ote 1988 10.31SIMPLE TRANSMISSION-LINE EXPERIMENTS by Roy C. Whitel ead, C-Eng., MIEE This article describes some simple transmission-line experiments that were developed for the uncLe scheme. Under this scheme, which was initiated by the ice, but later joined by other learned societies, members (usually retired) volunteer to go to schools to help teachers to bridge the gaps that exist between the academic world and the world of practical engineering. The material used in the experi- ments consisted of: a known length of coaxial le of which both ends were essibles +a twin-beam oscilloscope; + an HE generator with 75 Q output; + three 100 Q non-induetive potentiometers; + anohmmeter. Measurement of velocity ratio ‘The equipment should be con- LSet Pi nected as showin in Fi to its maximum resi and the wo Y sensitivity con. trols of the CRO to produce equal values of ¥ sensitivity Sct the signal generator to its minimum available frequency and note the small lateral dis- placement of the two wave- forms, Then, increase the gener- ator frequency, which causes the lateral displacement of the ‘waveforms 10 increase, until, for the first time, the two wave- forms are seen to be in phase The propagation time of the cable now equals one period ¢= Uf of the generator output. The velocity ratio of the cable then equals velocity in cable / velocity in free spac sable length in metres xf (3 x 108), A typical value is 0.8. Change the generator frequency to one quarter of the value used previously which makes the line one quarter wave- length long. Adjust P! to obtain vertical Y deflections on the cko of equal magnitude 10.32 eter ncn ectober 1969 ———} Adjust R2 to provide across the Fig. Disconnect Pi and measure its effective value, which is equal to the characteristic impedance, Z,, of the cable. Measurement of attenuation/ frequency characteristics Connect the equipment as shown in Fig. 2. Set Ri to equal Z,. Potentiometer Pi has been provided with a decibel scale (which can be done with the aid of the onmmeter). input end of the line an impe- dance equal to Z,, If the output impedance of the generator is 75, 2, this will be 43 Over a range of from 100 kHz to the maximum at which the available equipment will operate satisfactorily, adjust PI to produce Y deflections of equal magnitude, The cable atten- uations are then equal to the attenuations of the potentiometer. The attenuation/frequency char- acteristic of the cable roughly fol- requencies, say ows the emperical equation loss =(aif+ bf) [dB] where b< Ae Fig. 18, DG411s inthe head switching circuit of a disk drive, 10.36 slestorindia october 1580 Programmable one-shot multivibrator Another useful application for an analogue switch, a programmable one-shot multivi- brator, is shown in Fig. 14. This circuit produces pulses whose duration is deter mined by digitally selecting one of the wo timing resistors—see Fig. 15. Advanta, of the use of the DG419 in this circuit are small size (8-pin minipie or small-outline package), high speed, low on-resistance, and TTL compatibility even in single-sup- ply operation. Analogue switch powered by input signal The analogue switch in Fig. 17 derives operating power from its input signal, pro- vided that the amplitude of that signal exceeds 4 V and the frequency is greater than | kHz, This circuit is useful when signals are to be routed to either of two remote loads. Only three conductors are required: one for the signal to be switched one for the control signal and a common return, ‘A positive input pulse — see Fig. 16 — turns on clamping diode D and charges Cy]. The charge stored on the capacitor is used to power the chip; operation is satis: factory because the switch requires 1 sup ply current of not greater than 1 WA Loading of the signal source is impercepti- ble. The DG419's on-resistance has the respectable value of 100 © for an input signal of § V. Read/write disk-drive The circuit shown in Fig. 18 allows data to be written to or read from a disk. In the write mode, SW2 is closed. A ONE is ere ated by momentarily closing SWI. This causes current to flow in the left-hand half Of the head coil. A ZER0 is produced when $W3 is closed. This causes current to flov in the right-hand half of the coil and re verses the direction of the magnetic flux In the read mode, switches SW4 and SWS are closed. This connects the head coil to the read preamplifier so that the voltages picked up by the head as the disk slides by can be amplified. Single-supply operation with +12 V low-on resistance and high switching speed allow an improvement in data rates of roughly x10 when DG4Is are used in place of the more mature DG2s. ‘uit Micropower vrs transfer switch The purpose of the uninterrupted power supply (UPS) circuit in Fig, 19 is to pre- serve volatile memory contents in theFig. 19, Micropower ves circuit. event of a power failure. In this applica- tion, every tenth of a volt counts. This cir- cuit uses a micropower analogue switch that comes in an §:pin minipte or small- ouiline package, a 3-V lithium cell to sup- ply back-up power, a diode and 1wo resis. tors. Voltage losses under 0.1 V can be achie-ved During normal operation, currents of several hundreds milliamperes are sup- plied from Vcc. In this mode, SWI is open, so that the only drain. from the lithi- tum cell consists of leakage currents flow- ing into the Vj and $ terminals. The leak- age current is typically about 10 pA. Resistors Ry and Ry are continuously sampling Voc. When Vcc drops to 3.3 V, the DG417 changes states, closing SWI and connect- ing the back-up cell. Diode Dy prevents current from leaking back towards the rest of the circuit, Current consumption by the CMOS analogue switch is around 100 pA: this ensures that most of the available power is applied to the memory where it is really needed. In the stand-by mode, currents of some hundreds of milliam- a ain data When the +5 V supply comes back on, the potential divider senses the presence of at least 3.5 V and causes a new change of state in the analogue switch, restoring normal operation On-resistance is about 74 @ when Vee is +5 V and 128 Q when Vog is +3 V. For ‘example, an 800 {LA load, equivalent to a static RAM of 256 Kbit (MCM6IL16), will produce a voltage drop of 0.1 V on the analogue switch, which is much better than the 0.6 V drop occurring if a simple 2-diode circuit were used. Higher curtents and lower losses can be achieved by paralleling several sections in a multiple analogue switch such as the DG4OS. Line a in the photograph in Fi 20 Fig. 20. Oscilloscope waveforms show a clean power switch-over. illustrates how, in spite of Veg dropping to 0 V (line b), uninterrupted power is ap- plied to the load, Negligible voltage loss is caused by the switch. Line c shows that the DG417 changes state when its control input voltage decays to 1.4 V and changes again when it reaches 1.5 V on its way back to normal. The values of Ry and R2 may be adjusted for different trip points if desired. For the applications mentioned in this article, the DG4090 family of silicon-gate ‘€MOS switches comes a step closer to the ideal switch. Any application that uses industry-standard analogue switches can now be improved by choosing these fast, lower-power, versatile analogue switches. WV PRODUCT: Time Switch The MIL 2008 Q series Time Switch is fitted with a Quartz Electronic Drive Control and Stepper motor. The Quartz Frequency is 4.19 MHz and the Quartz stabilization guarantees the exact run- ning of the driving mechanism. These time switches are designed for the accu- rate and effortless control of oil heating installations, electric heaters, air condi- tioning plant, water processing plant, street lights, traffic signals, ete., ete., MIL 2008 Q is available with contact rat- ing of 16Amps. 250 V AC and with daily/ weekly programme dial. Operates on mains supply and continues to run for 150 hrs. after power failure on a battery back-up i Electronies Thakor Estate @ Kurla Kirol Road e Vidyavihar — (W) Bombay-400 086 @ Tel: $136601/ 5113094/5113095, Ferrite EE Cores ‘Available from M/s. Hilversum Elec tronics of Madras are a wide variety of ferrite FE cores for all applicatio ‘The FE cores feature a high permeabil- ity, low loss and are ideal for high fre- quency converters, inverters, SMPS etc. These cores are also available with air gaps and in a wide variety of sizes, Maruguppa Electronics Ltd. © Agency Division © 29 Ind Street Kamaraj ‘Avenue @ Adyar @ Madras-600 020 @ Tel: 413387 eho indi ctor 1808 10.37THE DIGITAL MODEL TRAIN — PART 6 by T. Wigmore The sixth part in the series deals in detail with the Booster Unit. Each of these amplifiers provides enough power for the control of up to fifteen trains on a digital model track. The booster is the last unit in the series that can be used with both the Marklin and the Elektor ElectronicsDigital Train System. The units featured in forthcoming parts in the series are peculiar to the ‘The power supply of a digitally controlled ‘model railway track is fundamentally dif- ferent from that of a conventional track, in that che supply voltage is switched rapidly between +18 V and -18 ¥. The switching is carried out by the booster (power amplifi- e ‘The booster ensures that the serial con- trol commands generated by the digital control circuits contain not only the infor- mation, but also the power to start lacomo- tives, tumouts (points) and signals, Since derailments, and the consequent short-circuits of the track, occur much more often on model railway tracks than on life-size ones, it is essential that the booster is provided with an efficient shor circuit protection facility. The concept (Our booster unit has two important advan tages over that from Marklin: higher out pul power and a regulated output voltage. The Marklin booster provides a maxi- mum output current of about 3 A. That is not much if you take the current drawn by one locomotive at about 700 mA , and add to this the current drawn by turnouts (points), signals, and coach lighting, It is on those considerations that our booster provides an output current of 10 A. The output voltage of the Marklin booster is fairly load-dependent: a 25% drop aver the normal range of loads is quite normal. That kind of variation has, of course, an adverse effect on the speed of the locomotives and the brightness of the ‘coach lights. ‘The output stage is an emitter follower Driving the bases by a voltage source ensures a virtually constant output volt- age, which resulls in independent speed control of the trains and constant bright- ness of the various lights. These properties are illustrated in Fig. 39 and Fig. 41 The use af an emitter follower also enables higher switching speeds since the transistors operate on the linear part of their characteristics: the switching times are, therefore, not adversely affected by saturation effects. ‘A draw>ack of the configuration is the higher voltage and the consequent greater 10.38 wear na october 1989 Elektor Electronics System. dissipation in the output transistors. Fortunately, this is easily rectified by the tuse of somewhat larger heat sinks, The circuit Since the switching pattern of the track voltage contains control information, it is important that the booster provides a clean ‘output signal. Much attention has, there- fore, been paid to the switching speed. The practical outcome is illustrated in Fig. 40, The bases of the emitter follower, T!-Ts in Fig. 42, are switched by TS and Ts respectively between +20 V and ~20 V. These voltages are provided by IC1-Ds and [C2-Ds respectively. The final output voltage is the difference between the base voltage and the sum of the base-emitter potential (about 1.5 V) of the output tran- sistors and the drop across the emitter resistors (maximum 0.6 V). In practice, the output vollage is 2 reasonably constant 418 V. See also the load characteristic in Fig. 41 ‘The emitter follower ensures a better bandwidth and regulation with complex loads than, for instance, feedback. Emitter resistors Ri2-Ris ensure an equal division of current to T1-T? on the ‘one hand and to Ts-Té on the other. Resistors Riz and Ris serve to measure the cuzrent in aid of short-circuit protec- tion transistors T9 and Tw. When the emit- ter current of Ti or TS tends to become too high, the drop across R12 or Rid rises suffi- ciently to switch on T9 or Tio, This causes a reduction in the base current of the output transistors and, consequently, in their col- lector and emitter currents, ‘The input stage is formed by Ty and Ts and is configured in a manner that makes a symmetrical input signal essential. If the input (pin 4 of Ka) is 0 V or not connected, Fig. 38. The booster unit without heat sinks and enclosure.Fig, 98, Date transfer by sultching the supply voltage. It's evident that the Marklin Booster (upper trace) does not provide a regulated out- putin contrast to the Elekor Electronics unit (lower trace) all transistors are switched off and the out- put presents a high impedance (that is, no voltage is supplied to the rails). When the input voltage is between +5 V and +20 V, Ty, Ts, Ti,and Te conduct and the output i8 switched to +18 V, With the input veltage between -5 V and -20 V, Ts, Ts, T3 and Ts conduct and the output voltage is switched to-18V. All transistors, except Ts and Ts, oper- ate on the linear part of their characteris tics. Transistors Ts and To are switched in the saturation region because switching transistors for voltages of 50 V and more are not available. Nevertheless, Cs ensures that these transistors switch at a sufficient ly high speed. Overload signal The circuit around Tin serves to indicate an overload condition. Note that only the negative output voltage is monitored. This is suificient since the loac on the negative line is sightly higher than that on the posi- tive rail. For instance, the turnout (points) decoders work with half-wave rectifiers And, therefore, load only the negative rai. Moreover, when no data are being trans- mitted the output voltage is negative When the booster is overloaded, To and Tro limit the current in the first instance. ‘The output voltage will then drop signifi cantly and this cases arise in the voltage fcross the outpnt transistors and thus in the dissipation If this situation is allowed to persist, there is a danger of the booster being thermally overloaded: the conse- quent risk of fire isa very real one Therefore, ifthe output voltage drops below 15 V, Th will switch off The signal at pin Sof Ki, aided by the pullup resistor on the main FD of the Elektor Flectronies system, goes Tow and this results in the removal of the drive to the booster with the aid of the software, Thermal overloads are, therefore, prevented; moreover, the system ‘knows’ that in this condition no data can be transmitted (even if they Fig. 40, Comparison of the switching behaviour under load of the Marklin Booster (upper traces) ‘and the Elektr Electronics unit (ower traces). Fig. 41. Load characteristic of the booster unit. could, they would not reach Fig 42, Circuit diagram ofthe booster unit 152220 the decoders). Capacitor C7 enables the ‘overload action to be delayed, so that the system is not dis- abled at every momentary short circuit. This will be reverted to later in the series. Construction If the recs shown in Fig. 45 is used, construction of the booster unit should not pre- sent any problems, Fit the wire links first: those close to the output tran- sistors should be of 1: mm dia. Mount resistors Ri2=-Ris well away from the board, because they get pretty hot during operation. ‘The board has provision fora 5-pin DIN connector, but if the booster is intended for use ina stationary position (which is normally the case), the respective wires may be sol- dered direct to the board. Circuits [C1 and 1Cz do not need a heat sink Do not fit C7 at this stage. ‘Transistors TI-Ts must be mounted on a heat sink with a thermal resistance of no} less than 0.8 K/W with the aid of good-quality insulating cfetor india acter 1969 10.39Fig, 43, Circuit diagram of a recommended power supply. washers. If BDX66/67 darlingtons (with TO33 housing) are used, they must first be mounted on fo the heat sink and then con nected to the board by not too long, heavy- duty wires, Power supply ‘The circuit diagram of a recommended power supply is shown in Fig. 43. The 2xi8 V transformer must preferably be a toroidal type. The rectifier must be a heavy-duty type and needs a heat sink (it may be mounted on to that for TI-T3). Tf you do not want to go to the expense of a new transformer, but rather use one that you have had lying around for some time, use the circuit shown in Fig. 44 Remember, however, that such a set-up will normally not be able to deliver more thaa a quarter of the power of the supply in Fig, 43, if that ‘nally, DO NoT connect transformers in parallel to increase the total available cur- rent:such a set-up can be a death trap. Fig. 45, Printed circuit board for the booster unit. 10.40 terns ectobe 1980 Fig. 44 f you are content (forthe time being) with a much smaller output current, this power supply will do neal. Assembly and test Since the booster is operated from the mains, great care and attention must be paid to correct assembly and insulatios Because there are always metal parts in a model railway system that can be touched Gike the rails), itis advisable to use a good= quality insulated enclosure. The insulation of the power supply transformer stated in the parts list is approved to Class I. This means that the mains cable should have three cores, one of which is earth. ‘All metal parts that can be touched Gncluding the heat sinks) should be con nected to earth, Connect the two secondary windings of the mains transformer in Fig. 43 in series and fit and solder the rectifier and the buffer capacitors (Ciot = Ci + C2 = C34 Ca = 2 20,000 UF rated at > 40 V). Before the supply is connected to the booster, switch on the mains and check that the direct voltage across the buffer capacitors is +25-29 V. If you measure 0 V, it is almost certain that the two secondary windings have been connected in anti- phase. Switch off the mains, discharge the capacitors via a resistor and reverse the connections of one of the secondary wind- ings. Then check the direct voltage again. If everything is all right, switch off the mains again and discharge the buffer capacitors via a resistor. Next, connect the supply to the booster via insulated wire of at least 0.5 mm dia and switch on the mains. Check that the Rise 4k7_ re = 1000; 1 W Ro 10k rosFis = 1k0 Rro(196R 15 = 0015; ‘TuiT2 = BDV 65 (Philips Components) Ts; = BDV 64 (Philips Components) Ts =BC640 Te BC639 y= BOS47B To = BC557B To=BOS37 Two = 80327 1 = 80557 IG; = 7805 IG = 7905, Miscellaneous: Ki = 5-way DIN sooket (180°) for PCB runing. Toten type spade eins for Poa ousting Ieuan mtorr Poa Type e918 Ta ‘Recommended power supply parts (not on PCB: F Mains transformer: 2x18 V @900 VA (e.9. ILP 73014) | ‘Smoothing capactiors: 4 of 10,000, 40 V | oc4 off 15,0000F: 40. | High current ge retir: min 20 A (2.0 8YW6' from Motorola). | One mains-tated fuse: 2 A slow. ‘Two low-voltage fuses: 10 A fast. Heatsink: 6.9, SK120-100mm (Dau Compo- ents; Fischer).output voltage of IC1 is +20 V and that of IC? is -20 V. There should be no voltage between B (earth) and R since there is as yet no input, Fit a 100 02,5 W, resistor between B and R and connect the input, pin 4 of Ki, to a positive voltage, for instance, +20 V at pin 3 of Ki. The output voltage should then be +18 V. With a negative input - obtained by interconnecting pins 1 and 4 of Ki - the output should be-18 V. Connecting to Marklin Digital The booster circuit is driven via Ki, which also carries the auxiliary +20 V and -20 V voltages. These are not of importance when the Marklin Digital is used, but in the Elektor Electronics system they power the RS232 interface, When the Marklin Digital is used, only pins 2 (earth) and 4 (input) of Kr need to be connected to the brown and red termi- nal at the rear of the Central Unit. Our booster, therefore, does Nor use the 5-pin connector on the Central Unit The overload signal (pin 5 of Kt) is also for use with our own system only. To arrange for the automatic switch-off of the Markiin unit during overloads, a diode must be added as shown in Fig. 46 Warning of a short circuit in the booster is then passed to the Central Unit, after whieh the current monitor in that unit arranges the switch-of The Central Unit may provide some of the power to the rails, but note that only the B connexions of the Central Unit and our booster may be interlinked. The R con- AUTO TEST SYSTEM FOR POWER SUPPLIES The Chroma 6000 Power Suppy Auto Test System, manuufactured by Chroma ATE Inc., Taiwan, is used for testing power supplies, both AC/DC and DC) DC types. It includes Switcher Analyz~ ers, Vin Sources, an Extended Measure- ment Unit and a System Controller (IBM PC-XT or compatible). The mod- ular hardware configuration allows the user to select and expand from one Switcher Analyzer module into. the ‘Chroma 6000 Power Supply ATS by in- crementing hardware modules. The Chroma-6000 ATS offers a MULTI- SYSTEM and PARALLEL testing ar- chitecture to improve the test efficiency and accuracy. Each of the su namely the Switcher Analyzers and the Extended Measurement Unit, contains a CPU, memory, dedicated control and measurement circuits, which is capable of distributed processing during test Fig. 6, How to connect the booster unit to Marklin's Central Unit. nexions (centre zail in the Marklin system) must be isolated from one another, Marklin supplies special parts to prevent the slide contacts from short-circuiling the electrically separated centre rails during For true-to-scale modellers The output voltage of the booster was cho execution Chroma 6000 ATS software packages provide a powerful menu driven, programmer free opera- tion, A.T.E. LIMITED ¢ (Electronics Divi- sion) ® 36, SDF 2 @ SEEPZ Andheri East) ¢ Bombay-400 096 The sen at £18 V to ensure that the maximum speed of the locomotives would be about equal to that in traditional model railway systems. Taken to scale, model trains trav- el faster than life-size ones. Modellers who want to have their locomotives travel at, proportionally, the same speed as life-size trains can arrange this by using 12 V zener diodes in the Ds, D and Dy positions, This, will result in an output voltage of #1 ini Infra Red Pyrometers L & Tismarketings non-contact temper- ature measuring systems havings wide applications is steel, cement, glass, heat treatment, bitumen mixings, food pro- cossings etc. ‘These systems use infra red radiation technology and are manufac- tured by Hozur Instruments Private Ltd in collaboration with hand Infrared Ltd of UK, Larsen & Toubro Ltd. @ Process Instru- ments Division @ Venkata remanna Centre ® Madras-600 018 © oaober 1909 10.4RESONANCE METER The test instrument discussed is a must for anyone working with RF signals, but with a limited budget. It enables the resonance frequency of tuned circuits to be measured within the range of 100 kHz to about 50 MHz, and can also be used as a capacitance meter, RF test ‘Traditionally, the name of the instrument of the type to be described has evolved from gritt dipper to gute dipper or simply ‘tipper. The first name, grid dipper, was used in the valve era and long after. When thermionic valves disappeared from con- sumer electronic equipment, the instru ‘ment was built from semiconductors and 10.42 eietnor india cetcbor 1900 generator and RF signal probe. J. Bareford baptized ‘gate dipper’ hecause the gate of a field effect transistor (FET) is electrically very similar to the first grid ofa valve, The instrament is basically an RF signal source with adjustable output frequency, coupled to a circuit that measures and indicates the amplitude of the output sig- nal — see Fig. 1. Because the terms ‘gate™ and ‘grid’ have been formed historically, but have really nothing to do with the basic function of the instrument, these misnomers are omitted here to be re- placed by the more universal term ‘reson- ance meter’ Tuned circuits and resonance Many constructors shy away from pro- jects that contain home-made inductors, because these, they feel, remain some- thing of a mystery owing to their lack of experience or suitable test and measuring equipment. And yet, many a radio ama- teur will confidently inform these con- structors that there is nothing mysterious about winding coils, Infact, dimensioning them and peaking the resultant tuned cir~ cuit at the right frequency is sheer plea- sure, provided, he will tell you, that a resonance meter is available, Without this simple instrument even experienced RF engineers are often at a loss in getting radio equipment to work correctly. ‘Any tuned circuit absorbs energy from another that is placed near it, and reson- ates at the same frequency. The RF energy is supplied by the resonance metet and an inductor that forms part of an oscillator. When this inductor is held near the coil under test, the oscillator output ampli- ‘tude drops if the two tuned circuits reson- ate at the same frequency. When the ‘dip’ is indicated by the signal level meter on the resonance meter, the resonance fre- quency of the tuned circuit under test can bbe read from the tuning dial, Mind you:Block diagram of the resonance Fig. 1. meter. the resonance frequency can be deter mined while the equipment of which the tuned circuit forms part is not powered. The coupling between the resonance meter and the tuned circuit under test is entirely inductive: all that is required is to hold the pick-up coil on the meter close to the tuned circuit under test. Tune the res- onance meter, and the signal level meter on it will tell you the resonance frequency of the L-C network under test. Resonance meter as an RF signal source... Since the resonance meter contains an 05- cillator capable of covering a faitly large frequency range, it may dovble as an RF signal generator. To align a receiver, for instance, the resonance meter is simply set to the required frequency and placed close to the aerial input. If tis too strong for a precise adjustment, the test signal can be attenuated by placing the resonance meter further away. ... as. a frequency meter or RF probe. The resonance meteris designed such that it can easily be used as a coarse frequency meter and signal strength meter (RF probe). These functions are achieved by switching off the internal oscillator, but leaving the pick-up coil and the signal rectifier plus level indicator in function Energy picked up from a resonating i | xu Fig. 2 ductor in equipment to be aligned thus ccatises the meter to deflect when the tun- ing dial is sct to the correct frequency. The meter indication isa measure of the signal strength, while the tuning dial shows the meastired frequency. These combined functions are particularly useful for alig- ning receivers and transmitters in which several frequencies are mixed. The probe function of the resonance meter is then ideal for, say, aligning the filter that fol- lows the mixer Stage, so that only the wanted frequency is passed. ..and aC or L meter Capacitance (C) and inductance (L) meas- urements are the last additional functions of the resonance meter. The value of a capacitor can be deter- mined with the aid of a parallel inductor with known inductance, L, and, of course, ‘a resonance meter. The capacitance, C, is simple to calculate from the resonance fre- quency, jo, of the parallel tuned circuit: Tho valuos of Lo. Table 1. 2aXLC Since the self-inductance is known, and the resonance frequency can be measured, the equation can be rewritten as 1 wf Similarly, inductance can be calculated with the aid of a reference capacitor: Circuit diagram of the budget resonance moter for 0.150 MHz in eight ranges. Three transistors The circuit diagram of the resonance meter is given in Fig. 2. All functions dis- cussed above are realized by three transis tors and a handful of passive components. Although perhaps a little difficult to de- luce from the circuit diagram, T1 and form an oscillator. The frequency of oscil- lation is determined by Ls and varicaps D: and Dz, The two diodes are connected in parallel to achieve the required capacit- ance range that can be adjusted with Pi ‘A total of eight plug-in inductors is required to cover the frequency range from 0.1 to 50 MHz. Preset Paallows the collector current in both transistors. to be adjusted, giving contro] over the amount of RF energy generated by the oscillator. Transistors Ts and T: forma differential amplifier in which Cr provides the feedback between the col- lector of Tz and the base of Ty The measuring amplifier is formed by ‘Ts. This transistor is operated in class C, so that it does not conduct until the vol age on Ls is about 0.6 V higher than the emitter voltage. This means that T> forms a basic rectifier because it conducts only during a part of the positive half-wave of the oscillator signal. This pulsating signal is converted into a clean direct voltage by Ce. Regulator IC: prevents fluctuations of the supply voltage degrading the stability of the oscillator. Should the supply volt- age be unstable, the voltageat Pi, and with it the varicap voltage, is unstable also. The varicap voltage, by the way, is not only dependent on the setting of Pr, Presets Ps and Ps are included to give Pi the correct, range, which is a must for the calibration of the scale on the front-panel designed slain cotobes 1908 10.43,Fig. 9. Printed-circult board for the reson- ance meter. Resistors (25%): | BuRr= 1k0 | Ra= 22001 Fo= 47k Rae = 33k Fe = 220k Pi = 100k linear potentiometer Pe =50k inear potentiometer PsP4= 5k preset H ‘Capacitors: C1= 1000 C2=22n Co= 474; 6V; radial Ca= 2200 Cs 10; 16V | Co= 1p0; 25 Cr=39n ‘Semiconductors: DrDe= BB2T2 TiiTe= F451 Ta = BFROT | IC) = 78110 | Miscellaneous: PCB Type 886071 radial choke (Toko). L2=.33mH radial choke (Toko). 132 00 Table 1 ‘Si = miniature SPST switch. ‘Mi = 250 HA moving-coll VU meter. 1 off DIN-type 2-way loudspeaker socket. +8 off DIN-type 2sway loudspeaker plugs. ABS enclosure. t mes) 10.44 cio for the resonance meter. The ranges of the resonance meter can only be calibrated if the standard choke values listed in Table 1 The circuit diagram shows that the supply voltage for the resonance meter is 18 V, obtained from two series-connected 9 V’ batteries. A mains adaptor with 12 VDC output is, however, also suitable iffthe resonance meter is fitted with a Type 7BLA0 voltage regulator Construction Resonance meters for frequencies up into the VHF range are not the easiest of con- struction projects. The main problem of many home-made as well as ready-made meters is that these produce ‘false’ dips when the pick-up coil is not held near a tuned circuit. According to Murphy's law, tliese false dips will typically occur in the most frequently used ranges. RESONANCE METER ® on Fig. 4 eao7T 12‘The printed-circuit board for the pres- ent resonance meter has been designed to minimize the risk of false dips. Figure 3 shows the component mounting plan and the track layout of the board, which is available ready-made. Mounting the parts on the board is fair ly straightforward. The only point to pay special attention to is that all component wires must be kept as short as possible. ‘The populated board is mounted in an ABS enclosure. This is not standard prac- ticein view of RF screening, but avoids the risk of a metal enclosure affecting the operation of the oscillator. As a result, false dips would occur, and the calibra- tion would have to be changed. All wires in the enclosure, and partieu- larly those between the board an the in- ductor socket should have the absolute minimum length. The front-panel design shown in Fig. 4 is copied and secured on to the enclosure. The pick-up coils are made from DIN- type 2-way loudspeaker plugs and ready- made chokes as shown in the photograph of Fig. 5. The chokes for the two lowest ranges must be types with plastic sleev- ing, not types with ferrite encapsulation. The other chokes are miniature axial types. Calibration The resonance meter can not be calibrated hefore it has been fitted into a suitable enclosure. Either a frequency meter or a short-wave receiver must be used for the adjustment procedure. If a frequency meter is available, the procedure is started by winding 10 turns of enamelled copper wire on to a lead pencil. Remove the pencil, and connect, the inductor to the input of the frequency meter. Plug one of the lower-range coils, into the resonance meter, switch on the instrument, and adjust P» for full-scale de- flection of the signal level meter, Mi. The frequency meter will display a frequency if the pick-up coil on the resonance meter is held near that on the frequency meter. Check whether the displayed frequency rises if Pi is turned anti-clockwise. If not, swap the outer wires on the poten- tiometer. Set the tuning to the highest fre- quency in the range, and adjust Ps until the frequency meter displays the scale fre- quency. Turn Pi to the lowest frequency, and adjust Pa similarly. Once again check the upper frequency and correct the set ting of Po if necessary ‘A short-wave receiver is also suitable for calibrating the resonance meter, but has the disadvantage of requiring to be re-tuned for every adjustment, Since every choke has its particular tolerance, itis necessary to check for scale deviations in every range of the resonance meter. If the deviation in a particular range is unacceptable, try using another choke from another batch but with the same value indication. Choke tolerance is typically 420% Practical use ‘The resonance meter is a test instrument that becomes easy to operate only grad- ually through regular practical use. Prior to any measurement, the frequency range must be determined, and the appropriate pick-up coil selected. In some cases, you will need to change coils if the resonance frequency is close to the end of the range. Switch on the instrument, and adjust the sensitivity control, Ps, for fs.d. (full-scale deflection) of the signal level meter. Line up the pick-up coil with the inductor in the equipment (Fig. 6), and tune carefully until the pointer of the level meter moves to the left. The frequency range is prob- ably fairly large at this stage. To achieve a more accurate dip, move the pick-up coil away from the inductor while still ensur- ing that they point in the same direction. Fig. 6. Now retune the resonance meter until a sharp dip is found. If the resonance frequency of a tuned circuit is not known, it is wise to start ‘examining it in the lowest range of the resonance meter, increasing the range until a sharp dip is found. This procedure avoids harmonics being mistaken for the natural frequency. ‘The resonance meter need not be very accurate since its main application is the coarse dimensioning and adjustment of inductors, or capacitors that form part of anL-C tuned circuit — precise adjustment is invariably done along the lines of the setting-up procedure with the equipment turned on. Also, itis useful to note that the resonance frequency of an L-C circuit is generally lowered when it is installed in the circuit, which introduces additional capacitance. ‘Not all tuned circuits can be tested with the aid of the resonance meter. In- ductors wound on a toroid core, or en closed by a metal cover, absorb very little externally applied energy, and do not pro- duce a dip unless a small external series inductor of one or two turns isadded tem- porarily. This lowers the resonance fre- quency to some extent, but allows a useful estimate to be made. Some in-circuit L-C networks will not dip either. Examples are the heavily damped tuned circuits in the emitter line of a grounded-base transistor circuit, To measure the resonance fre- quency, either the transistor or the tuned circuit must be removed Finally, the resonance frequency of series L-C tuned circuits can not be ‘measured unless a capacitoris included in the cireuit that provides a path from the inductor back to the series capacitor. This, in fact, creates a parallel tuned circuit Using the resonance meter to ‘dip’ an L-C tuned circuit. ator ina cbr 1089 10.45,CENTRONICS MONITOR The Centronics interface standart A. Rigby often said to be without problems in practical use. When a malfunction occurs, however, many more connections have to be checked than, for instance, on an RS-232 link. The monitor described here alleviates the plight in debugging a Centronics connection. It is a handy tester that indicates the levels on all lines simultaneously, including those that Nearly all of today’s personal computers are equipped with a Centronics port for connecting a printer. The general accept- ance of the Centronics interface standard has. been helped by the availability of ready-made eables of variouslengths, and the fact that the majority of printer manu- facturers have ensured compliance with the pinning of the ‘blue-ribbon’ input con- neetor on their products Sometimes, however, the installation of a new printer or cable gives rise to awkward problems that take a lot of precious time to analyse and resolve. In these eases, the present in-line indicator provides almost instant fault analysis be- cause it shows the logic state of the data- bits and a number of handshaking and control signals Data and handshaking To ensure that the computer-to-printer link works as required, a number of sig- nals must be present, while the use of others depends on the equipment used at either side of the Centronics cable. At the computer side, datalines D0-D7 must be 10.46 clei india ccicbor 1988 carry pulses. connected, as well as handshake lines STROBE, BUSY and/or ACK (ackrow- ledge). Especially the last two signals are prone to cause trouble if the relevant pins are correctly marked (according to the printer manual), but not used electrically. When the Centronics connection is fully functional, the computer puts the bit pattern to be sent to the printer on to the eight datalines, and actuates the STROBE line by pulling it low. This enables the printer to recognize that the databyte rep- resenting the printable character is stable and therefore valid. Reception of the byte is signalled to the computer by a low-to- high change on the BUSY line, BUSY re- mains high until the printer is ready. Depending on the type of printer, the re- ceived databyte is instantly printed, or stored in an internal buffer memory. In both cases, however, the processing (which is not necessarily the same as printing) of a characteris signalled to the computer by means of a high-to-low transition on the ACK line. ‘The processing of received characters differs from printer to printer. Older mod- cls print each character immediately after it has been received, halting the computer during the printing operation. Printers of allater generation typically feature a small buffer that allows a line of printable char- acters to be stored. The characters in this buffer are not printed until a carriage re- turn is received. Many modern matrix printers have buffers capable of storing many kilobytes of text, and handle print ing, data spooling and. communication with the computer simultaneously. Some top-range models house more data pro- cessing chips than the average PC com- patible ‘Apart form the data and handshaking lines, the Centronics standard specifies a number of other, auxiliary, functions: PE Paper Empty Goes high when the printer is out of paper. SEL Select Indicates that the printer is on line and ready to re- ceive data, Automatic line feed after a car- riage return, Resets the printer Indicates internal failure. AUTO Auto Feed INTE __ initialize ERROR ‘The last four lines must be given a fixed level, even if they are not used in the ac- tual connection between the computer and the printer. In other words: the mini- mum requirement is that non-connected active-low and active-high lines be fitted with a pull-up and pull-down resistor re- spectively. The monitor ‘The Centronics monitor indicates the cur- rent logic level on all lines by means of light-emitting diodes (LEDs). The databus lines are connected to a Type 74HCTS40 buffer that supplies sufficient output cur- rent to connect the LEDs direct to ground. A logic high level causes the LED associ- ated with a particular line to light. Each of the five status lines is connected direct to the associated LED. This can be done with impunity because the signal levels are= [+[>[=[=]» fairly steady. Signal lines STROBE, BUSY and ACK require a different configuration because they carry pulses rather than steady le- vels. Three monostables in the form of ‘Type 555 timer chips are therefore used to drive the relevant LEDs, Inverter Ts-Ris- Ri ensures that the BUSY LED lights when the associated line is actuated (Le, logic high), Such an inverter is not re~ quired for the ACK and STROBE lines, ‘which are active-iow. The associated 555 are housed in dual timer ICs, a 556. AIF ies Ap be ol Fig. 1. Circuit diagram of the Centronics monitor. All other signals that may be available, but are not strictly required for correct operation, are simply passed between the relevant pins of the input and output socket of the monitor. Many Centronics cables do not have separate ground wires, but use commoned connector pins at both ends. These pins are often connected by a single wire : Sixteen LEDs enable the user of the monitor to locate the possible source of trouble at a glance: 8 data LEDs, 3 for the handshaking lines, and 5 for the status lines. Power supply An external supply will not be required in most cases because virtually all modern printers supply #5 V at pin 18, 35 or both. Diodes Ds and Dio ensure compatibility of the monitor with these printers, and also allow the unit to be powered from an ex- ternal 10 V/50 mA power supply. Regula- tor ICs then provides the 5 V supply voltage for the ICs and LEDson the board. eto india asser 1880 10.47Connections Connector Ki is a 36-way Centronics socket with straight solder pins. Push the socket On to the PCB edge, while ensuring that the pins align with the copper islands. Soldering is then straightforward. Con- nector Ke is removed froma standard Cen- tronics cable plug, and secured as Ki. Two types of connector exist: versions with screws and versions with clamps for the screening hood. The screw type is the bet- ter for the present application 13 | SELECT | Printer Pin] Signal’ | Source [1 | STROBE | Computer | 2 | Datao | Computer | bata | Computer| | [4 | psta2 [computer | [5 | Data's | Computer 6 | bata | companer | [rf tetas | computer | lee esate eae Se: Data 7 _| Computer [_10 ACK } 1" Busy Printer [se | BARER [te 14 | ALES | Computer 13 | ne. 76 |_eround 17_| chassis 18 15V 19_| ground 20 | ground 21 | ground 22 | ground [eeees: ‘ground 24 | ground 25 ground | 26 | ground 27 | ground 28 | ground 29 ground | | 20 | ground a1 | iNT | computer | | 32__| FAROR | Printer | | 38 ne. a4 ne. a5 15V_| Printer 38 ne. 10.48 clezorinae octane 1989 at both sides of the printed-circuit board. Parts ist Resistors (5%): Fis = 1k0 SIL resistor aray Capacitors: (CisGai0s:Cr = 100n G2iCax0s;Ca = 330n Semiconductors: Di-DaiDi1-Drs = LED; 3 mm; red DeDro= 1Na148 Di= 1N4OOt TisTziTe = BOSS7B Ta= BC547B Miscellaneous: 2, Track layout and component mounting plan. A number of parts must be solderedASIC MICROCONTROLLERS by Simon Young* This article discusses the evolution of the MCS-51 architecture and how to use ASIC technology to extend the set of generic features contained in the family members. Intel offers the MCS-S1 architecture to customers in a number of ways. ‘The first is via standard products, such as the 80C51BH and 8052. These devices are designed for the general microcon- troller marker, where the internal hardware resources can be closely matched to the system requirements. The second is via Application Specific Standard Products (a8s°s) developed for a vertical market sharing a common set of additional features. An example is the 80CSIFA, which augments the MCS-51 core features with a programmable counter array, an enhanced serial port for ruultipro- cessor communications and an up/down timerfeounter. The third way to gain access to the MCS-5I architecture is via ASIC, and this is the subject of this article. Intel offers to customers the same capability it uses house to develop asses MCS-51 Microcontrollers The MCS-51 family of microcontrollers was designed 10 meet the needs of embed: ded control applications. The architecture and instruction set were optimized for the ‘movement of data between internal memo- ry and internal peripherals. Figure 1a shows the MCS-51 architec- ture. ‘The Special Function Register (5°) bus connects the internal resources (such as port latches, timers and peripheral con- trol registers) with the crv. Thel28 bytes of on-chip RAM (between 00 hex and 7E hex) can be addressed both with direct (Mov data addr) and indirect (ov @Ri) addressing modes. Some devices, ¢.g.. the 8052, provide an additional 128 bytes of on-chip RAM for temporary data storage between 80 hex and FF hex (dotted in Fig. 1b). This may be addressed only indi rectly ~ forming a useful area for the stack, The SFR space appears to the CPU as 128 bytes of memory located between 80 hex and FF hex. This area of memory is accessed only by direct addressing modes, in order to distinguish it from the addition- *Simon Young is with Intel Corporation (UK) Ltd at Swindon al data RAM discussed above. Of the 128 locations, 21 are used in the 80C51BH standard product (26 on the 805: The 64 Kbytes of external data memo- Fy space are accessed with the Movx instruction. Another powerful feature of the MCS- 31 architecture is the ability to address individual bits within certain sex and internal RAM locations. All MCS-S1 ‘Typical 80C51 core-based design. devices contain a complete Boolean (sin- gle-bit) processor. The MCS-51 instruc- tion set supports the Boolean processor with instructions to move, set, clear, com- plement, OR, AND, and conditional branch on bit. This ‘bit addressability’ allows individual bits to be tested and modified without the need of complex masking operations, with consequent significant improvements in speed, dekior indi ster 1808 10.49,inteJ- MCS-51 MEMORY STRUCTURE PROGRAM MEMORY FFF (ee (eal a [es [em| 0000 Ee PSEN DATA MEMORY Fig. ta r External Intcrpes C MCS-51 ARCHITECTURE TIMER? TIMER! wen Fig. 1b At the time the first members of the MCS-51 family were introduced, there was mo economic packaging for high pin- count devices. The parts were packaged in 40-pin bit. packages: only recently have PLCC packages been used. To provide access to the intemal hardware resources of the device, several functions, including port input and output signals, external multiplened address/data bus, serial port Vo, external interrupt signals and timer/counter input signals had to be mul- tiplexed, Clearly, functions multiplexed on the same pin may not be used concurrent- 1 10.50 atatorinaaceaber 19 As systems designers developed in- creasingly complex embedded control applications, the 8051 required additional memory, peripherals and/or 1/o ports. ‘These had to be added externally as mem- ory or memory-mapped peripherals, reducing the parallel io available on the 8051, Fully expanded in this way, only a single 8-bit Yo port is available. While the on-chip features and price-performance ratio of the 8051 make it still an attractive proposition when compared with other solutions, the end result is different from what the 8051 was designed to be: a sin- sle-chip, stand-alone microcontroller. UCS1: Intel's original microcontroller core In 1985, Intel introduced the UCS1, which was developed from the 1.5 jum cHMOS i 80C51BH standard product, The UCS1 allows designers to integrate the micro- controller core, memory, memory-mapped peripherals and cells from the 1.5 jim stan- dard cell library on to a single chip, In transforming the 80C51BH into the UCS1 core cell, the v0 pads and pin multi- plexers were removed. The internal peripherals, multiplexed address-data bus, control signals and input and output ports all have dedicated signals, With the ability to choose different amounts of program om (zero, 4 K, 8 K or 16 K bytes) and data Ram (up to 1K bytes) with no loss in functionality, the UCS1 has been a very successful part of Intel's ASIC offering, In summary, the UCS1 provides sys- tems designers the capability to integrate “fixed’ core and memory-mapped periph- crals, complete with user-defined logic, on to assingle ASIC device, The asic resembles an integrated version of the discrete solu- tion, with increased flexibility because of the. demultiplexed fo. However, it is not possible to apply the full power of the architecture and instruction set to memo- ry-mapped peripherals. UCS51: Intel's next genera- tion microcontroller core Infel have recently introduced the UCS51 family of microcontroller and peripheral cells into the 1.5 jum ciMos m standard cell library. The UCS51 permits systems designers to connect any of the available peripheral cells or user-defined logic directly into the SFR space. The UCSS1 cores then access the control registers within these peripherals in exactly the same way as any internal st register. There are great benefits to be gained from directly connecting peripherals to the sm bu + instructions operating on peripheral registers in the SFR space are more code- efficient then accessing memory-mapped registers indirectly (with MOVx), so that Jess program memory space is required; ‘+ register direct-instructions (ADD, aDBC, 'SUBB, INC, DEC, ANL, ORL, XRL, MOV, PUSH, POR, XCH, CINE and DINZ) execute more quickly, improved system through- put: + certain bytes in the SFR space (located at x0 hex and x8 hex) are bit addressable: ‘mapping peripherals into these locations permits the bit-banging capabilities of the Boolean processor to be applied to these registers;interface logic between the UCSSI core and UCSSI peripherals is eliminated: there is no need of an address latch, address decoder or tri-state bus driver. ‘The basic UCSSI core cell resembles a UCSI, Port! has been removed to provide access to the SFR bus, although it may be replaced easily as described later. Interfaces have been added for connecting kom medules (either none or one of 4 K, 8 K, or 16 K bytes), a Ram module (same RAM as 8052) and an interrupt expansion unit, A functional cell diagram is shown in Fig. 2. Additional interrupts enhance real-time performance Unexpanded UCSS1 cores have five inter- rupt signals available, as have the UCS1 and 80C5IBH. Users may configure the internal peripheral interrupts for use as general purpose interrupt signals, with no change in priority levels and vector loca- tions. It is also possible, by the use of the Interrupt Expansion Unit, to add a further five external interrupts, making a total of 10, with complete flexibility of interrupt source, peripherals, on-chip or off-chip logic. 1s! peripherals for configuring unique microcontroller cells The Bus Interface Unit is, perhaps, the most important UCSS1 peripheral cell Functionally, it is and 8-bit input, 8-bit ‘output SF bus interface. With it, designers may replace Port! and add further demul- tiplexed i/o ports as needed, This cell is also used to interface between on-chip user-defined logic and the sR bus. Thus, customer developed logic using cells from the 1.5 jum standard cell library may be mapped directly into the SFR space to gain the advantages dis- cussed previously. The 8-bit, B-channel successive approximation ADC has a nominal conver- sion speed of 20 us at a core frequency of 16 MHz. A conversion may be triggered by hardware or software, with an interrupt generated on completion. Timer2 is a 16-bit timer/counter cell, enhanced over the Timer2 found on the £8052 standard product and some asses. ‘The serial /o cell isa full-duplex serial port, enhanced from the serial channel contained in the 80C51BH by the addition of a new mode: Mode 4. This mode pro- vides 9-, 10-, 11- or 12-bit transfers with variable baud rate. In Mode 4, the UCSSISIO cell also generates parity for transmission and detects framing, overrun and parity errors on reception. Edwina Inert ROM {See ' ; ‘Demultiph y CPU ( REBSIEPSS ous) K UCS-51 ARCHITECTURE * Special Function Register Bus FD Asic\q) Fig.2 ‘The baud rate generator cell is used to ‘generate clocks for the serial 1/o peripheral or for user-defined logic. Operating trom the L6 MHz system clock, the 8&6 gener ales rates from 50 Hz to 4 MHz with an accuracy better than ().2%. ‘These five 151 peripheral cells and 16 distinct core configurations complete the UCSSI offering at the time of launch: more are in development. The 1.5 im standard cell library includes ssi, Msi and Vo functions and may also be integrated ona UCSS1-based asic cap tools aid development of microcontroller-based asics The Design Entry Tool, ner, provides a high-level, menu-driven means of config- uring the core hardware resources. The UCS51 core options are RAM, ROM oF interrupts. Adding a peripheral requires two data to be entered: the peripheral type and the address of its control registers in the SFR space ‘The DET outputs a symbol for this core. ‘The designer simply adds the user-defined logic he requires, surrounds this with the Yo pads and the design capture is com- plete. ‘Once captured, the designs netlist is transmitted 10 mpvs ~ Intel's Mainframe Design Verification System based on VAX/ZyCad hardware. Full-timing gate- level simulation of the entire chip is poss ble with vectors written in ropL — Intel's ‘Test Pattern Development Language ~ and EXtASMSI. ExiASM51 provides 8051 assembly source code and simulation stim- tulus, and synchronizes the execution of instructions with external stimulus applied to the asic. ‘The simulation output may be viewed fas text on the host, or retumed to the workstation for display and review in the graphies condition. The ICE-UCSSI In Circuit Emulator allows the designer to develop and test code for a UCSS1-based asic, and to emu- late the completed asic (core, peripherals and user-defined logic) in the target sys- tem. The ICé is a PC-based emulator sys- tem, offering the same advanced features as Intel's other 1CE systems, ‘The UCSS1 core is tested with a slight- ly modified version of the 80C51BH stan- dard product test program, guaranteeing functional and parametric equivalence to the standard part. The peripherals are test- ed in the same way. ‘The designer is responsible only for his user-defined logic, and provides Trot and ExtASMS1. The result is standard producty quality and reliability: an aot of 0.1% is guaran- teed Summary Intel's famnily of UCS51 core and peripher- al cells provides the systems designer with unprecedented flexibility in asic design. Not only is access provided to the basic core architecture of the 8051, but also to a specialized set of peripheral cells. The design tools guide the designer through design capture, simulation and test vector

You might also like

• GE Transistor Manual 1964

  

  No ratings yet

  GE Transistor Manual 1964

  664 pages
• Amateur Radio Technician Guide

  

  100% (4)

  Amateur Radio Technician Guide

  131 pages
• ETI Electronic Circuit Design No 2

  

  No ratings yet

  ETI Electronic Circuit Design No 2

  92 pages
• 1.1 The Roll of Electronics in Automobile: Chapter - 1

  

  No ratings yet

  1.1 The Roll of Electronics in Automobile: Chapter - 1

  71 pages
• Transistor AF and RF Circuits - Allan Lytel PDF

  

  100% (6)

  Transistor AF and RF Circuits - Allan Lytel PDF

  127 pages
• Principles of Electronics Redone

  

  100% (2)

  Principles of Electronics Redone

  153 pages
• Electronics Digest 1980 Summer Vol 1 No 1 OCR

  

  No ratings yet

  Electronics Digest 1980 Summer Vol 1 No 1 OCR

  100 pages
• Transistor Circuits Rufus P Turner

  

  No ratings yet

  Transistor Circuits Rufus P Turner

  161 pages
• Electrical & Electronics Department 2009-2010

  

  No ratings yet

  Electrical & Electronics Department 2009-2010

  20 pages
• Basic Electronics Interview Questions and Answers: Q1. What Is Electronics?

  

  No ratings yet

  Basic Electronics Interview Questions and Answers: Q1. What Is Electronics?

  7 pages
• Basic Electronics Interview Questions and Answers

  

  No ratings yet

  Basic Electronics Interview Questions and Answers

  7 pages
• ECG 315 TransistorManualThirdEdition

  

  100% (2)

  ECG 315 TransistorManualThirdEdition

  170 pages
• 2 Edn - Com-The Fully Digital Radio Transmitter - Is It Real or More Hype

  

  No ratings yet

  2 Edn - Com-The Fully Digital Radio Transmitter - Is It Real or More Hype

  7 pages
• Radio Transmitters

  

  No ratings yet

  Radio Transmitters

  95 pages
• Poptronics 1976 09.equalizer 8 Bands

  

  No ratings yet

  Poptronics 1976 09.equalizer 8 Bands

  134 pages
• 125 Transistor Projects Rufus Turner

  

  100% (2)

  125 Transistor Projects Rufus Turner

  100 pages
• Emetteur À Courant Porteur

  

  No ratings yet

  Emetteur À Courant Porteur

  116 pages
• Encyclopedia of Electronic Circuits Volume 1

  

  95% (20)

  Encyclopedia of Electronic Circuits Volume 1

  800 pages
• Chapter 4 Transmitter

  

  No ratings yet

  Chapter 4 Transmitter

  6 pages
• Transistor Circuits Gernsback 63 Rufus Turner

  

  No ratings yet

  Transistor Circuits Gernsback 63 Rufus Turner

  161 pages
• Basic Electronics Interview Questions and Answers q1 What Is Electronics

  

  No ratings yet

  Basic Electronics Interview Questions and Answers q1 What Is Electronics

  8 pages
• Pe 1994 10

  

  No ratings yet

  Pe 1994 10

  136 pages
• Ec2254 Nol

  

  No ratings yet

  Ec2254 Nol

  85 pages
• Paging Sys Report

  

  No ratings yet

  Paging Sys Report

  54 pages
• Radio Electronics January 1990

  

  100% (2)

  Radio Electronics January 1990

  100 pages
• An Introduction To Electronics: PDF Generated At: Mon, 05 Dec 2011 00:57:30 UTC

  

  100% (2)

  An Introduction To Electronics: PDF Generated At: Mon, 05 Dec 2011 00:57:30 UTC

  265 pages
• Re - 1985-09

  

  No ratings yet

  Re - 1985-09

  132 pages
• Radio Theroy Demystify

  

  No ratings yet

  Radio Theroy Demystify

  15 pages
• FM Transmitter Design for Engineers

  

  89% (9)

  FM Transmitter Design for Engineers

  52 pages
• FM Receiver Project Report

  

  No ratings yet

  FM Receiver Project Report

  20 pages
• RF Concepts

  

  No ratings yet

  RF Concepts

  109 pages
• ECE411 Panes Von Andrae Research Work

  

  No ratings yet

  ECE411 Panes Von Andrae Research Work

  9 pages
• ETI - Top Projects

  

  No ratings yet

  ETI - Top Projects

  132 pages
• EE 04 Electronics Communication Notes

  

  No ratings yet

  EE 04 Electronics Communication Notes

  17 pages
• 1.1 History of Electronics

  

  No ratings yet

  1.1 History of Electronics

  51 pages
• Electronic Devices and Circuits

  

  No ratings yet

  Electronic Devices and Circuits

  3 pages
• Coyne Electronics For Electricians and Radio Men

  

  No ratings yet

  Coyne Electronics For Electricians and Radio Men

  446 pages
• Hoverboard

  

  No ratings yet

  Hoverboard

  31 pages
• EC2254

  

  100% (1)

  EC2254

  375 pages
• 400 Ideas For Design

  

  100% (3)

  400 Ideas For Design

  243 pages
• GE - Transistor Manual 1964 PDF

  

  No ratings yet

  GE - Transistor Manual 1964 PDF

  338 pages
• Musical Siren Lab Project Report

  

  100% (3)

  Musical Siren Lab Project Report

  8 pages
• Power Amplifier1 1 (Recovered)

  

  No ratings yet

  Power Amplifier1 1 (Recovered)

  27 pages
• Wireless Home Automation Using Relay

  

  No ratings yet

  Wireless Home Automation Using Relay

  68 pages
• Analog Dialog

  

  No ratings yet

  Analog Dialog

  60 pages
• Re - 1988-11

  

  100% (2)

  Re - 1988-11

  116 pages
• Telephone Call Recording and Answering Machine System

  

  No ratings yet

  Telephone Call Recording and Answering Machine System

  33 pages
• Radio+Frequency+Integrated+Circ+ +Hooman+Darabi

  

  No ratings yet

  Radio+Frequency+Integrated+Circ+ +Hooman+Darabi

  958 pages
• Basic ND Digital Electronics

  

  No ratings yet

  Basic ND Digital Electronics

  28 pages
• ASSD 1st Revised 02115 SC PN 9

  

  No ratings yet

  ASSD 1st Revised 02115 SC PN 9

  318 pages
• Filters .Antenna Switch .. What Are They?

  

  No ratings yet

  Filters .Antenna Switch .. What Are They?

  5 pages
• Electronics 2

  

  No ratings yet

  Electronics 2

  8 pages
• ETI Circuits No 2

  

  No ratings yet

  ETI Circuits No 2

  100 pages
• Re - 1972-11

  

  100% (2)

  Re - 1972-11

  94 pages
• Modern Electronic Circuits Reference Manual

  

  100% (8)

  Modern Electronic Circuits Reference Manual

  1,256 pages
• Ee 1992 04

  

  100% (2)

  Ee 1992 04

  56 pages
• Ee 1992 01

  

  No ratings yet

  Ee 1992 01

  57 pages
• Ee 1992 12

  

  100% (2)

  Ee 1992 12

  89 pages
• Ee 1992 02

  

  100% (1)

  Ee 1992 02

  59 pages
• Ee 1991 07 08

  

  No ratings yet

  Ee 1991 07 08

  92 pages
• Ee 1991 06

  

  100% (1)

  Ee 1991 06

  59 pages
• Ee 1989 12extra

  

  100% (2)

  Ee 1989 12extra

  80 pages
• Ee 1990 01

  

  No ratings yet

  Ee 1990 01

  56 pages
• Ee 1990 02

  

  No ratings yet

  Ee 1990 02

  54 pages
• Ee 1990 03

  

  No ratings yet

  Ee 1990 03

  55 pages
• Elektor Electronics 1998-11

  

  No ratings yet

  Elektor Electronics 1998-11

  54 pages
• Ee 1988 03

  

  No ratings yet

  Ee 1988 03

  47 pages
• Elektor Electronics 1998-02

  

  No ratings yet

  Elektor Electronics 1998-02

  51 pages
• Ee 1987 11b

  

  No ratings yet

  Ee 1987 11b

  76 pages