Rnal of the Radio Society of Great Britain 110111000
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• I I II I • • IM!I rnal of the Radio Society of Great Britain A SELECTION OF RSGB PUBLICATIONS See inside back cover for full list teleprinter r a di o d a t a r e f r r c d e r b o o k V I-1F-11-11-4 F 111.• 1.1.411.,• test equip ment for the radio amateur 01,1 RADIO 301:111, 01 e-.14111113,1dAIN e e e e e et O S C AR 0 .111 1110111000 NE W FRO M 4átronics NO W THE BEST IS EVEN BETTER Introducing the most comprehensive R.T.T.Y. TER MINAL UNIT you can, or indeed need, ever buy—the Catronics CT100 Mk2 Now incorporating a number of modifications, YOU have asked fo,: including Completely automatic receive/transmit modes. Protected and buffered input provided for TTY keyboard. Automatic re-generation of incoming tones. 11111111111•11K Special ft. interference suppression circuit, etc, etc. e 1. • C•11.101.141 Inputs for: Outputs for: •••• - , MA. Audio FSK signal in V.D.U. or other TTL compatible equip ment 1111_11, Data in from V.D.U. (e.g. G3PLX) TTY Magnet - single or double current TTY Keyboard or Tape Reader AFSK to drive Transmitter Featuring a unique digitally controlled 'Autoprint' circuit which is a superior replacement for the 'Antispace and 'Autostart' facilities found on some other terminal units. The terminal will ignore most CW and phone signals but will respond to a correct RTTY signal Tuning correctly into an RTTY signal is made simple with a single 'correctly tuned' LED plus an additional 'Mark frequency' indicator. The FSK demodulator circuit utilises a special 'state-of-the-art' system to give excellent performance and stability at low cost. The demodulator is set to decode signals within 75Hz of nominal frequency i.e. 120P-1350Hz for space and 1370-15201-1z for mark, when in narrow shift position. The teleprinter interface unit incorporates electronic 'de-bounce circuitry to eliminate spurious switching from the Keyboard. The loop supply is protected by a separate fuse and is suitable for driving all single current and double current magnets known to be available. VAT inclusive prices are as follows: CT100 Receive only £0.00, CT101 Receive/Transmit £93.50. CT102 with Teleprinter interface £.94.50, CT103 Complete Terminal Unit £98.50. All models plus £3.50 Securicor delivery G3PLX RTTY VIDEO DISPLAY NEW 10 WATT 2M PA KIT (April 1977 Rad Corn) Kit (excluding modulator, keyboard and P.S.U.), £83.55 Set of printed circuit boards £15.20. UHF Modulator kit £11.95. Flashing cursor kit £8.60. Diode Matrix kit £13.25. Suitable mains P.S.U. Transformer £2.75. Catronics UHF Modulator. £15.00. NOTE regarding PROM program: The PCBs and programmed PROMs supplied by us make use of a slightly different program sequence resulting n different pin con- nections to those published in the 'Rad Corn' article. Whilst constructors buying PRO Ms and PCBs from us will have no difficulty, those producing their own PCBs or having PROMs programmed elsewhere should note this important difference. A detailed modification sheet is available with the PCBs. KEYBOARD KIT The printed circuit Ooard is designed to taxe a maximum of 70 keys but may be assembled with a smaller number of keys for a simpler keyboard. A 10 WATT output version of our famous 40 WATT 2M P.A. kit is now available, for The board is not dedicated to any specific coding, allowing it to be us- boosting the OUIPUI of 1 2 watt 2M FM transmitters. ed for any project whether it requires ASCII, Baudot or any other code. 12 volt supply Auto T/R switching This makes it suitable for many projects including; Complete with cabinet and full instructions Kit price £18.00 inc VAT • 65p post G3PLX RTTY VDU Also available ready.bullt at E28.00 Auto morse sender. etc. The Keyswitches themselves are single pole push-to-make type and require no extra mechanical mounting arrangements. 40 WATT PA KIT A legend sheet is provided with each kit enabling the constructor to label the keys to suit individual requirements. still available at C19.50+ 65p post Requires 12 volt supply and ID watts drive. Price: only M AO. Please add 50p for postage. Also available ready-built at E29.50 SEE ALL OUR PRODUCTS AT ALEXANDRA PALACE EXHIBITION All prices include VAT but please add minimu m of 30p for p&p. Data — Catalogue available at 45p + large (A4) 18;p SAE DEPT. 906 COM M U NIC ATIONS HOUSE, 20 WALLIN GTO N SQU ARE, W ALLIN GTO N, SURREY SM6 8RG Tel: 01-669 6700 Open 9am to 5.30p m Mon to Fri, 9am to 1pm Sat. Closed for lunch 12.45 to 1.45p m ISSNO033 780 EDITOR A. W. Hutchinson Assistant editor radio Mrs M. J. Collins communication Draughtsman D. E. Cole Editorial secretary May 1979 Volume 55 No5 Mrs J. D. Brown CONTENTS Contributions (including Members' Ads) and all 408 Current comment. QTC correspondence concerning the content of Radio 410 A frequency counter for a 144MHz transmitter— Communication should be addressed to: N. B. Pritchard, G8AYM The Editor, RSGB, 416 An inexpensive high-Z accurate transistor voltmeter— 88 Broomfield Road, R. E. Barber, BSc, G3NEF/ZC4RE Chelmsford, Essex CM1 1SS 418 A modification to the G3ZSS digital morse code generator— K. J. Marley, G3EIO/HB9ALV Tel 0245 84938 420 The "miracle sky hook"—A. D. Taylor, G8PG Office hours: 0845-1645 422 Technical topics—Pat Hawker, G3VA 428 International Conference on Antennas and Propagation— Correspondence concerning the distribution of L. A. Moxon, G6XN the lournal and all other Society matters should be 429 New products—Frequency counters addressed to: 430 Now it can be told—the Fareham "saga"—J. W. Swinnerton, RSGB Headquarters, G2YS 35 Doughty St, London WC1 N 2AE 432 Reception and processing of TIROS-N weather satellite telemetry (Part 2)-1. Gilbert, G4CEB, and T. J. Terrell, Tel 01 -837 8688 DipEE, MSc, PhD, CEng, MIEE Office hours:091 5-1 71 5 435 Microwaves—Charles Suckling, G3WDG 436 4-2-70—Graham Knight, GM8FFX 441 VHF/UHF hand planning—Tom Douglas, G3BA, and Ian ADVERTISING White, G3SEK Advertising, other than Members' Ads, 442 The month on the air—John Allaway, G3FKM should be sent to: 445 Propagation predictions Mr C. C. Lindsay, 446 IIF propagation study 2 Leyburn Gardens, 447 Solar and propagation information in GB2RS news Croydon, bulletins—C. E. Newton, G2FKZ Surrey CRO 5NL 448 Raynet—R. Bullard, G8NM W. RSGB committees, 1979 Tel 01 -686 5839 449 Your opinion Hours: 0915-1715 450 Contest news 451 Contests calendar EDITORIAL PANEL 452 Obituaries 453 Mobile rallies calendar. Special event stations J. P. Hawker, G3VA R. F. Stevens. G2BVN 454 Club news 461 Members' ads 464 Looking ahead Radio Communication is published by The Radio Society of Great Britain as its official journal on the first Thursday of each month and is sent free and post paid to all me mbers of the Society ABC 21,498 copies per Closing date for contributions issue average unless otherwise notified: ,C RADIO SOCIETY OF . 116 . •nd C MC .11110.1 circulation in 1978 1st of month preceding month of publication GREAT BRITAIN 1979 Ci) ICO M lol SOME ICO M PRICES ARE DOWN! (for the time being) SEE THE FULL RANGE AT ALLY-PALLY THE LEADER BASE STATION IC-211E Fast becoming one of the most popular base station rigs because of its superb performance and advanced technology, the IC-211E leads the field in 2M base stations. With a full synthesizer which employs state of the art technology it provides all you want for full coverage on FM USB. LSB or CW on 2 metres with that extra bit of quality for which ICOM are so renowned, plus the chance to use the latest digital technology and even drive it from your home computer if you wish! Less VAT = £464 With VAT= £522 THE MOBILES The IC-245E is probably the only multi-mode mobile on the market. Of course, it can also be used as a base station, and many own one for just this purpose. It employs all the same technology as the IC-211E, and is in fact virtually the same electronically with the exceptions that it only operates on USB, FM and CW and does not have VOX and sidetone or full seven digit readout. As with the 211 you have access, IC-245E via a multi-way plug on the back, to the LSI synthesizer for connection of a keypad, computer or other bit of home-brewed logic. NO W £399 inc. Less VAT=E354.67 With VAT =1399 IC-240 NO W £189 inc. The IC-240 is the ideal mobile rig for most people. Apart from the fact IC-280E that it is quite a lot cheaper than most, it is, in fact, more suitable than NO W £245 inc. many to use in the car while driving (and let's face it, it is under those conditions that most mobiles are used). It can be operated with ease without taking your eyes off the road and provides up to 22 channels lwhich is more than you are likely to need). Being synthesized, of course, there are no crystals to buy for extra channels. Full repeat, As usual, ICOM have kept ahead with technology and have produced reverse repeat and automatic tone burst plus a low power facility are their revolutionary new IC-280E which uses a microprocessor to selectable from the front panel.