0000

systems SL _

OPERATING:On 23 c mWe look atpropagation,aerials andequipment )--?-

TESTING:An RTTYterminalfrom yourCW autokeyer?

PUBLICATION

AYAPRIL'83

85p

-AMATEUR RADIOEXCHANGE

TS -430STrio's latest HFtransceiver for mobile orbase station usefeaturing 160-10m

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Yaesu's latest HFtransceiver, which fits neatlyinto their range between th,FT -102 and the FT -ONE...and is an obvious competitcfor the mythical (or merelyelusive?) Trio TS -930.Features like general coverage receive, notch filter, pass -bandtuning and IF shift will make this rig a top -of -the -market bargainat a price yet to be announced, but which we anticipate will benot a million miles from £1100

IC -R70Presenting thebest in today'sreceivertechnologyfrom ICOM,featuring:

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AMT -1This AMTORterminal unit (Amateur TelepontingOver Radio) is a micro -processor controlled error -correctingdata communication system, allowing virtually error -free datatransmission between suitably equipped stations. Made inEngland by ICS Electronics, it offers full AMTOR error -correctingfacilities plus RTTY, ASCII and CW (transmit only). Mode andconfiguration control from the keyboard of your terminal Crystal controlled AFSK generator and 4 -pole active receive filter

A milestone in amateur radio communications for just £275.

R-2000In their latestgeneral coveragereceiver Trio combinethe features which madethe R-1000 so successful with themost up-to-date micro -processor control techniques. Continuous coverage from 150kc to 30MHz SSB/CW/AM/FMTen memories to store frequency, band and mode data Memory scan Programmable band scan Three filters builtin with Narrow/Wide selector.Good value at its list price.Even better value from us at only £365

SONY ICF-2001Still unique in the market,a superb HF com-munications receiverwith keyboard entryand LCD coveringAM/SSB/CW from 150kcto 30MHz and FM from 76 to108MHz with six stationmemories.A masterpiece of compact modern technology for only £129.

IC -740The latest addition to theICOM transceiver range, thisgives all mode coverage-AM/CW/SSB/FM- rightacross the amateur bandsfrom 1.8 to 30MHz.

Incorporating suchfeatures as IF shift, pass -band tuning and notch -filter as standard, this is one rigthat has to be seen and tried by anyone in the market for a reallytop-quality base station.

OUR PRICE £675

FT -102A worthy successor in the Yaesu range to the evergreen FT -101series, with so many extra features. Notch filter Three 61466 final tubes IF shift control Bandwidth control from 2.7kHz to 500Hz APF control RF processing Tunable audio network for speech tailoring SSB/CW/AM/FMOUR PRICE OF £725 INCLUDES AM/FM BOARD

sum mu NE EN mi RN um IN mui373 UXBRIDGE ROAD, ACTON, LONDON W3 9RHTel: 01-992 5765/6/7 Just 500 yards east of Ealing Common stationon the District and Piccadilly Lines, and 207 bus stops outside.

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All prices include VAT and are correct as we go to press.However, we reserve the right to vary them if forced to do soby the time this advertisement appears. Phone for up-to-date

information, or send 50p for our full Stock List.

EditorFrank Ogden G4JST

Assistant EditorRichard Lamont G4DYAAdvertisement Manager

Neil TerryManaging Editor

Ron HarrisSales DirectorIan Herbertson

Managing DirectorT. J. Connell

Published by:Argus Specialist Publications Ltd.,145 Charing Cross Road,London WC2H OEE.Telephone: 01-437 1002.

Distributed by:SM Distribution Ltd.

Printed by:Q. B. Ltd.

Subscription Rate:UK £12.800/Seas Sur: £13.250/Seas Air £25.80Ham Radio Today,Sub Dept.,513 London Road,Thornton Heath,Surrey,CR4 6AR.

Ham Radio Today is normally published onthe- first Friday in the month precedingcover date. The contents of this publicationincluding all articles, designs, plans, draw-ings and programs and all copyright andother intellectual property rights thereinbelong to Argus Specialist PublicationsLimited. All rights conferred by the -Law ofCopyright and other intellectual propertyrights and by virtue of international copy-right conventions are specifically reservedto Argus Specialist Publications Limitedand any reproduction requires the priorwritten consent of the Company. '© 1983Argus Specialist Publications Ltd. All reas-onable care is taken in the preparation ofthe -magazine contents, but the -publisherscannot be held legally responsible for er-rors. Where mistakes do occur, a correctionwill normally by published as soon as possi-ble afterwards. All prices and data con-tained in advertisements are accepted by usin good faith as correct at time of going topress. Neither the advertisers nor the pub-lishers can be held responsible, however,for any variation affecting price or avail-ability which may occur after the publi-cation has closed for press.

CONTENTS VOLUME ONE NO. 4 APRIL 1983

REGULAR COLUMNSLETTERS 4You write and we comment

RADIO TODAY 7

News roundup from the world of amateur radio

CLUB NET 25

Around the clubs with Cyril Young G8KHH

TECHNICALITIES 48Main topic this month is successful RF design using a CW TX /R X as an example

54NEWCOMERS FORUMNEXT MONTH IN HAM RADIO TODAY plus HRT MORSE COURSE

CONSTRUCTIONSIMPLE TWO METRE LINEAR AMPLIFIER 29Get out better with this useful little homebrew box

AN AMATEUR TELEVISION STATION Pt 2 36This month: the character generator

FEATURESIMPROVISING ANTENNAS 8

Getting out needn't cost you a fortune

OPERATING ON 23 CENTIMETRES 12

This is one of the most interesting bands to operate on, By G3OSS

PLAIN MAN'S GUIDE TO MASTS AND TOWERS Pt 3 17

This month: the the pros and cons of various mast types

TAKING APART THE FT101 20

A purchase, modifications and servicing guide by Harry Leeming G3LLL

THIS IS RAYNET 42Amateur radio lends a helping hand

REVIEWSMBA -RC TERMINAL UNIT 57This remarkable device will turn a morse auto keyer into an RTTY set and more

HAM RADIO TODAY APRIL 1983 3

LETTERSTOP BANDFrank, Thanks for the February issue ofHam Radio Today, which I'm pleasedto see is just as absorbing as the first.The KW2000 series is excellent.

Could I make this one plan -don't leave out Top Band. It is too dearto the hearts of many people.

In many respects 160m is differentfrom the other amateur allocations. It isthe amateurs' only test area for MFpropagation, a subject that could nodoubt fill a whole chapter of yourseries on the mechanics of theionosphere. In home -brewing, the lowfrequency allows a high standard ofconstruction with easily available andcheap components, yet there areproblems in the size of antennas andsome tuning elements. It is a band onwhich dx-working and rag -chewingexist side by side and on which AM isnot yet considered 'old'.

Some of the above commentsmight apply to 80m too, but it isperhaps the area of operatingprocedures that is of greatest interest.How about an operators' guide to 160min a future issue? What are thosecoastal station frequencies to avoid,what are the allocations to overseasamateurs, the DX window, thesquiggles and bangs we hear? A lot ofthis worthwhile information seemsthinly spread throughout manypublications and some is not easilyavailable to the average amateur.

Maybe I've missed some previousdefinitive article somewhere, butplease don't give God's given band thecold shoulder!

STEVE RICHARDS G4HPE

I wouldn't dream of it. I love Top Bandtoo. You have put forward a great ideafor an article. Anybody prepared totake up the challenge? We pay jollywell - Ed.

HELP, PLEASEDear Ham Radio Today, I have justread your first magazine and found itvery useful expecially the bit onpropagation, which helped a lot withmy short-wave listening.

My receiver is a Lafayette HA 700and virtually unknown as I haven't seenany articles on it (hint, hint). But myreceiver has a send facility with the

SSB, CW and AM modes and I wouldlike to know from your technical staffwhat modes it transmits on and alsohow can it be made to transmit as thereis no plug at the back saying where toput a microphone or morse key.

There is a small hole at the backand I wondered if a plug wasconnected here and wires solderedinside.

Please could you help (I'm on myknees) as I'm hoping to take the RAEnext yhear after my GCE's and CSE'sand it would save me some money if Icould have this conversion done.

PAUL MARTIN

Sorry Paul. I don't know your set.Maybe somebody else does and wouldbe kind enough to write in. - Ed.

THE PROFESSIONALSSir, Of course the RAE is easy whenlooked at through the eyes of theelectronics and radio professionals whohide behind amateur radio call signs.They also have an eye to business,hence the proliferation of radio andelectronic magazines containingtechnical reviews with complicatedcircuit diagrams which use abbreviatedtechnical jargon which no-one elseunderstands. These people should becalled radio professionals and issuedwith an extra prefix in their callsign,eg. GK4XYZ where the K means knowit all.

Also, don't forget that no specifiedqualifications are required to sit theRAE, (Marconi hadn't any). Indeed, itis not even obligatory to have taken anRAE course.

R.T. FINCH G4PNE

Um, Yes. But what exactly is yourpoint, Mr Finch? - Ed.

THE BIG WAITFrank, Here's to success on thelaunching of "H.R.T."!

I am a SWL, currently studying forthe RAE for May '83 and fullyintending to make a beeline for a G4ticket. As my practising speed is nowaround 18 WPM I am going to take agamble (?!) and apply for a morse-testbefore sitting the RAE. There are toomany delays if you go through the slow

Please address correspondenceto:

Frank Ogden G4JSTHam Radio Today,145 Charing Cross Rd,London WC2 OEE.

sequence of RAE - WAIT MONTHSFOR RESULT - APPLY FOR G 6 -WAIT MONTHS FOR LICENCE -TAKE MORSE TEST AFTER WAITINGMORE MONTHS AFTERAPPLICATION - APPLY FOR G4LICENCE - WAIT AGAIN FOR G4PASSPORT. So I reckon it's worthtaking a gamble.

Another reason for by-passing G6stage is. the apparent state of 2 metres.It's becoming another waveband forCB'ers and having to use repeatersisn't my idea of communications. Youcan't beat the unpredictable HF bands!

I must say I like the look of yournew magazine. Practical Wireless andShort -Wave Magazine are superior toRadio Communication for beginnerscontent but it looks as though you maybecome No. 1 (!!!)

Is it possible for you start a regularfeature giving approximate up-to-datevalue of both valve and solid statereceivers, transmitters & transceivers,old or new, as a guide to the lessinformed SWL/HAM NOVICE etc???All the very 73's on your new venture.

BRIAN PATCHETT

Thanks for your comments, Brian. Weplan a regular 'Glasses Guide' typefeature - Ed.

PARROT FASHIONSir, I am writing to congratulate you ona superb first edition and to wish goodluck for the future (not that you'll needit!)

I would also like to make a fewpoints on matters raised in your letterscolumn.

Firstly, I would like to defend CW.It is difficult, indeed tedious to learnmorse but it does give a great deal ofpleasure in use and is still the bestmode for effective mode ofcommunication.

As for homebrew, I build all myown equipment. This is partly due tofinancial considerations but mainlybecause I enjoy building somethingwith my own hands then hearing itwork.

Finally, the RAE. I amdisheartened to read in Rad Corn thismonth that while 67% of candidatespassed, the C & G noted greatweakness in the 'electrical theory'

4HAM RADIO TODAY APRIL 1983

section and very good performance in'licensing conditons'.

This seems to indicate that whilecandidates can learn, parrot fashion allthe tiny details of who to send yourrevoked license to and when totransmit your call sign, they cannotapply very basic electrical theory.

Incidentally, I shall be taking theRAE myself in May, but I have nointention of claiming a Class B license;by this time next year I should havetaken the PO Morse Test and got aG4+3.

(Did I see an opinion to the effectthat the license should be confined tothose over 18?)

MARTIN SMITH RS4962

It's a personal opinion but I would loveto see radio amateurs becoming moreaware of the technical aspect of ourhobby. Power to your elbow, Martin.- Ed.

A very reasonable viewEditor, To quote a phrase "Morse Codeis an archaic form of communication":As a professional communicationsengineer and a confirmed CW addict Icouldn't agree more with thatsentiment.

The reason I use so much CW., isbecause I really do enjoy it! I like toloaf along at 35-40 wpm with mycontempories on 80 and 40m.Admittedly I use an electronic keyerand paddle or even sometimes akeyboard sender.

My point is, I don't want to forceCW on to any guy who doesn't want touse it. CW is another language, full ofnuances, varying styles and for me issheer pleasure. I also enjoy rockmusic, but loads of people don't. In theend it must be each guy to his own!

As a G3 of 1066 vintage I wouldlike to see Class B licensees givenevery opportunity to use morse.Perhaps on 144/70/28 and 1.8MHz forstarters. Usage is great practice andwould certainly keep the CW bandsegments alive.

I could even go along with theidea of a code free licence foreveryone because CW surely doesn'tmake you any better at mis-operatingan SSB TX and splattering over thebands!

On the other hand I get frustratedby people, usually Class B licenseeswho bleat about having to learn morseetc., etc. My attitude is, please don'tknock something unless you have triedit first!

All the standard CW argumentsabout bandwidth, better DXcapabilities and so on are probablytrue, but amateur radio is a hobby isn'tit? There are loads of differingtransmission modes available so why

not let everyone try their own thing ifthey so wish.

As a parting shot I must add Ifavour the American idea of gradedlicences, that would really improvestandards - technically where theyneed to be raised.

STEVE WILSON G3VMW

I agree completely with everything yousay. I must confess though that I don'tenjoy CW very much. Occasionally,personal bias creeps in even thoughyou don't intend it to - Ed.

MISTAKEN IDENTITYSir, I find your suggestion that theminimum age limit for a licence shouldbe raised to 18 to be detrimental to meand other young op's. I am 14 yearsold and have had by G6HZU call fornearly a year now. Not only have I(and other young op's I suspect) had toput up with being called a YL bypeople who know well that I am not,and a young whipsnapper etc., butnow the trend is to blame us for everybelch etc. on the repeaters. How oftenhave you heard "That's some kidplaying music on the repeater"? I havenot saved up the money to buyequipment for 3-4 years by doing oddjobs with no 'free gifts' from my parentsto be greeted that "all op's under 18are wallies!"

I hope to take my CW test soon.I'll have to scrimp and save forcomponents for the Homebrew HF CWrig that I'll build. I just hope that I'llget a slightly warmer welcome than Igot on VHF from the so-called 'realhams'. This is only half though, theothers have been helpful andconsiderate. I wish they were all so.

J. PELHAM G6HZU

PS What about a simple, cheap, 20meter CW TX/RX? 10 watts out?PPS Sorry about the long letter, but Ifeel very strongly about this.

Sorry, it wasn't my opinion. I've beenplaying around with radio gear since Iwas eight. I suspect that the GPOwould have called me more than awally if it had caught up with me then- Ed.

SPEECH PROCESSINGFrank, I read your article on speechprocessing with great interest.

When I first adopted ssb in 1952the usual mode was AM. At that timebaseband clipping was being widelyused by amateurs to increase their AMtalk power. Some ssb pioneers triedthis form of clipping, but it showed noapparant advantage. The explanationof this finding was later given in an

article by Dr D A Tong (1). SSBgenerated from baseband clippedaudio does not have an RF envelopewhose amplitude is well defined. Toavoid flat topping one is unable to usethe hoped for increase in AF gain,when compared with no clipping. Onthe other hand RF clipping producesan SSB signal of well definedamplitude, so one can keep theaverage output power high withoutsplatter. (But if the post -clipper gain istoo high splatter could be continuous!One should not assume that the ALCwill take care of this)

The other important advantage ofRF clipping is that the harmonicsgenerated fall at multiples of thesideband frequency and are allremoved by the second sideband filter,as are most of the intermodulationproducts. Compare this with thebaseband case where the "real nasties"the harmonics of audio frequenciesbelow fch/2 (i.e. below 1.5 KHz) fall inthe passband of the second filter. Muchof the power in speech lies in the lowerfrequencies so this is significant. Thusit is clear why RF clipped speechsounds much cleaner than that which isbaseband clipped. A 6 to 10 dBincrease in loudness can be achievedwith little audible distortion. Beyondthis level of clipping distortionincreases without much gain inloudness. One can play the clipperthrough a tape recorder to adjust theclipping level. Personally I increasethe pre -clipper gain with normalspeaking until all syllables soundclipped, then set up the rig for no flattopping with fairly close speaking. Icalculate that my legal ssb signal isequivalent to at least 10 kW of AM!The RF clipper seems like the onlyexception to Murphy's Law.

Good luck with the new mag. I'mglad to see it's not for licensedappliance operators".

JEREMY WHITFIELD G3IMW

(1) AF and RF clipping for speechprocessing. D A Tong, Wireless WorldFeb 1975. pp 79-82

I take your point but also take issue inthe nicest possible way. The effect ofclipping an SSB signal is to increasethe phase change rate on the zerocrossings as well as flat topping thesignal as one expects.

The final 'clean up' filter can onlyrespond to the rate of phase change asa precise function of its bandwidth.The result is that the filter puts backenvelope modulation on the 'squaredSSB' albeit with improved risetimes onthe uncliped SSB signal. What aboutan article on the subject, Les? -Ed.

HAM RADIO TODAY APRIL 1983 5

/B.PI.O.SELECTRONICS

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HIGH QUALITY NiCAD BATTERIESType 1-9 10-24 25-99

'AA' 0 -5Ah 0.90 0.85 0.82'C' 2 -2Ah 2.40 2.30 2.20SUB '0' 1 -5Ah 2.30 2.15 2.00'D' 4 -0Ah 3.40 3.20 3.06PP3 0 -11Ah 4.25 4.00 3.80

NiCAD CHARGERSAC.1 Charges up to 4 'AA' cells. £5.90MC.2 Charges up to 4 x 'AA', 'C' or '0'

cells or any combination of the aboveas well as PP3s. £8.50

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All battery prices include VAT, and FREEpostage on orders over f5, for orders under f5please add 60p to cover P&P.

BNOS 'A' SERIES POWER SUPPLIESPrimarily designed and ideally suited for both amateur and professional mobile transceivers. Nowextending our range to meet a growing requirement the model 12.'6A and 12/40A have beenintroduced.

The 'A' series of fixed voltage 113-8V1 power supplies are designed to operate at full ratedcurrent continuously with voltage regulation better than 0 1%. Short circuit protection, foldbackcurrent limit and over voltage crowbar protection circuits are incorporated, along with full RFprotection, to minimise equipment damage due to user error or equipment failure.

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cableSocketsBU 11 50259 souare.flange 0.40BU 12 50259 single hole, inside nut 0.47BU 13 S0259 single hole, outside nut 0.47CouplersBU 21 Back to back female 0.57BU 22 Back to back male 0.79BU 23 Male to female elbow 1.13BU 24 1 male, 3 female 'T' 1.35BU 25 3 female 'T' 1.46BU 26 Female to female lightning 1.22

arrestorAdaptorsBU 31 UHF plug to BNC plug 1.75BU 32 UHF plug to BNC socket 1.15BU 33 UHF socket to BNC plug 1.49BU 34 UHF socket to BNC socket 1.64BU 36 UHF plug to N socket 2.90BU 37 UHF socket to N plug 2.90

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impedance. 30W mar, 15Wcontinuous rating, DC -150MHz, VSWR less than 1.2 1

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PREAMP TRANSISTORS3SK88 145MHz, 26dB gain, 1.1dB NF 1.05BF981 145MHz, 1846 gain, 0.7dB NF 1.38BER91 432MHz, 1848 gain, 1.9dB NF 1 50

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OPTIONAL FEATURES Printer interface board (Centronics compatible) On -board 40 column printer (12V) External 80 column printer (SEIKOSHA GP100A)

Ham Radio Today, April 1983

War games for RAYNET

RAYNET may be invited totake part in the civil defenceexcercise , WARMON 83, acc-ording to a spokesman for theRSGB.

Originally set up to provideaid in peacetime emergencies,participation in the excercise,scheduled for March 12/13, rep-resents a new departure in theorganisation's original scope ofoperations.

According to sources at theMOD, RAYNET's functionwould be to pass on simulateddata about the position andstrength of nuclear explosionsand their radioactive fallout,from monitoring posts to Gov-ernment bunkers.

The organisation would onlytake part at the invitation ofthe local CEPO - Local Emerg-ency Planning Officer.

and peace games...

The Home Office has alsolifted other restrictions on RAY -NET. It is to be allowed toprovide radio links for eventslike sponsored walks and mar-athons. Each RAYNET groupwill be limited to one excercisea month.

Radio amateurs will also beable to call for help over theair if they arrive at the sceneof an emergency, but only if noother means of communicationis available. If, for example thereis an accident on the motorway,amateurs can only be used to callfor help if the emergency tele-phones are out of action.

Another valuable change allowspeople other than licenced amat-eurs to speak into the micro-phone in an emergency. Rescueworkers can now communicatedirectly, rather than having every-thing repeated by the operator.There will however still have tobe a licenced amateur keepingan eye on things.

At the moment emergencycommunications can only be senton behalf of the British RedCross, the St John AmbulanceBrigade, a CEPO or the police.But the Home office says that itis willing in principle to add otherorganisations to the licence ifrequested - so if, for example,a mountain rescue team wantedRAYNET to provide radio facil-ities for them, the Home Officewould consider their request.

G4DYA

RADIO TODAYCan you help?

Staff and students at the Hay -wards Heath College are strugg-ling to set up a permanent radiostation and general electronicsdepartment with, they add, verylittle cash. They would be 'over-joyed' to hear from anyonewho can offer them radio equip-ment, aerial cable, components,PET/BBC software or anythingat all in fact.

If you think that you maybe able to help them out pleasecontact Pete Metcalfe G8DCZat Haywards Heath Sixth FormCollege, Harlands Road, Hay -wards Heath, Sussex. Phone 0444456281 and ask for the PhysicsDepartment.

Wrong price

SMC, the Yaesu main agentwith headquarters in Southamp-ton asks us to point out thatit was not bargain time of thecentury as may have been bel-ieved by reading the company'sad in our March issue (p42/43).

The ad showed the FT902DMpriced at f185 when it shouldhave appeared as f885. The priceindicated in the advert was a

genuine printing error andtherefore the company has noobligation to supply any setsat that price even though therewere lots of potential custom-ers! In our defence we mustpoint out that the advertisingcopy was provided for our mag-azine via Practical Wireless whichalso carried the same error.

Wireless revival

The East Suffolk Wireless revival1983, a popular annual mobilerally, will take place on theBank Holiday Sunday, May 29at the usual venue of the CivilService Sportsground, TheHollies, Straight Road, Ipswich.The site is between BuckleshamRoad and Felixtowe Road and isadjacent to the Suffolk ShowGround.

PRACTICE RAE ANSWERS to thepapers which appeared in the Februaryedition of Ham Radio Today.

Page 58: licencing regulations1 b, 2 d, 3 a, 4 d, 5 c, 6 c, 7 d, 8 a,

9 d, 10 b.

Page 59: radio theory1 b, 2 d, 3 b, 4 d, 5 c, 6 a, 7 a, 8 c,

9 b, 10 c, 11 d, 12d, 13b, 14 a,15 c.

The rally will open at 10 amand will be similar to previousevents except that the 'bringand buy' stall will be replacedby a fleamarket and car boot sale.The transceiver clinic and aerialtesting range will be featuredas usual in addition to the tradersand stands, displays and otherattractions for the rest of thefamily.

More details will be availablenearer to the time and requestsfor stand space should be address-ed to George Spencer G6CRN,83 Tuddenham Avenue, IpswichIP1 6PX. Phone 0473 44047.

RAE changes

The people who set the RadioAmateurs' Exam are canvassingfor ideas about how the examcould be improved. If you didn'tlike the May Exam, or any ofthe other ones for that matter,now is the chance to air yourviews.

The City and Guilds is settingup a working party to reviewthe exam. It says 'The principleobjective of the examinationis to ascertain the candidate's

ability to operate an amateurstation within the terms of thelicence and not necessarily totest expertise in particular as-pects of the amateur service.'

Ideas for changes to the syl-labus should be sent to Mr SAllison, City and Guilds Instituteof London, 46 Britannia Street,London WC1X 9RG.

Judging by the postbag whichwe regularly receive on the topicthere are quite a few peoplewith something to say aboutthe matter. If you don't like°the RAE, write now (but notto us).

Show postponed

We regret that the SOUTHERNHAM RADIO SHOW, which wasto have been held on Sunday,April 17, has had to be postponedto a later date.

The organising of the newHorsham based event has beenseverely hampered by the shorttimescale upon which bothourselves, and the organisers,Corinthian Exhibitions had em -embarked on. Watch this columnfor details of the new date.

HAM RADIO TODAY APRIL 1983 7

IMPROVISINGANTENNAS

Custom made, fully trapped, multiple band commercial antenna systemslook as though they should provide the last word in performance. The idea

has been put about that to stand any chance of making worthwhilecontacts, you have to part with at least £60. Not true. Any piece of wire

will radiate RF with comparable efficiency provided that it is long enoughAmateur radio is now comparativelybereft of any substantial element ofDIY thanks to the influx of equip-ment from the Far East, and theever-expanding TV broadcast ser-vice. unless one can construct aneffective screened cage it is impos-sible for the large majority ofamateurs to carry out any experi-ments with transmitters, especiallythose for the HF bands, withoutcausing unacceptable QRM withneighbouring TV receivers, exceptduring the small hours of the night,when one ought to be DX-ing,anyway.

With the long -overdue demiseof the monochrome 405 -line TV ser-vice (Bands I and III) by the end of1984 this situation could improve alittle. At the moment the lower orderharmonics of HF band transmitterscan cause havoc to this service.

For the amateur who stillhankers after some form of experi-mentation, playing around withantennas may be the only answer.Given a Japanese "black box" with,usually excellent suppression ofharmonics, and a sensible,balanced antenna feeder a lot morefun can be had than might be im-

and high enough.agined. Surprisingly, the cost isnext to nothing, which is quite rarethese days. Wether it be ordinaryTV reception, VHF/FM stereo, orany other form of communication byradio, the simplest and cheapestmethod of improving the perfor-mance of the system is by attentionto the antenna system.

It is presumed that in addition tothe black box there is a standingwave ratio meter (SWR), most likelycombined with a powercator. This "indicator" in cheapermeters merely shows the relativeoutput rather than the absolutevalue but is still quite adequate formost purposes. Anyway, there isusually a similar indicator on thetransceiver. If one can afford to goto a meter measuring actual poweroutput, and SWR without anypreliminary adjustments, so muchthe better. One small point, ensurethat the meter is suitable for the out-put impedance of the transmitter,normally 50 ohms.

The only other item, whichshould be an absolute necessity inany AR station, is a "dummy" or

Transmitter

receiver

Coaxial links

FIG .1.

SWRpowermeter

Coaxialswitch

Tuned feedersA A

3:]

Incorporates dummy load

ATU

Fig. 1 Arrangement of equipmentwhich includes a coaxial switchincorporating a dummy load

enabling the rig to be tuned upwithout radiating

artificial load, also of the rightimpedance and of adequate powerrating see Fig. 1. This rating neednot be thee maximum power outputquoted for the transmitter providedthe rig is run at that level for onlyshort periods. A suitable design fora dummy load appeared in theJanuary issue of Practical Wireless.Any resistor used in a dummy loadmust be either carbon or carbon -

Fig. 2 Coaxial switch should havea ceramic wafer to minimiselosses. Wiring should be in heavycopper wire and be as short aspossible. Several coaxial outletsenable rapid choice of antenna

film otherwise it will show con-siderable reactance at the higherfrequencies and give entirelymisleading results.

The initial set-up is as shown inFig. 1 which is more or less perma-nent. The experiments start after theSWR/power meter. The coaxialswitch can be a bit expensive so aceramic wafer switch, using theshortest possible wiring, can beused for the HF bands, Fig. 2. Withthe dummy load in circuit the SWR

8HAM RADIO TODAY APRIL 1983

meter should show a 1:1 ratio at allfrequencies. Checking at 1.8 or3.5MHz and then on 28MHz shouldbe sufficient to prove this point.DON'T operate the coaxial switchwhen transmitting!

WiresMany amateurs seem loathe to

experiment with wire antennas,without any good reason. It couldstem from their early days studyingfor the RAE, with books andmanuals showing antennas withlovely straight elements, perfectlyhorizontal, feeders coming away atright angles and of exactly the rightlength, or the large expanse of lawnunder which hundreds of feet ofradials must be buried before onecan hope to get out on Top Band.Very nice, of course, but really onecan get out and work the DX with alot less perfection.

Having decided on a particulardesign for an antenna, preferablynot too complicated at the start,have a look at where the maximumcurrent will occur on the principalband on which it will be used,assuming it to be a multibanddesign. The object in life then is toget that part of the antenna up ashigh as possible and preferrably asfar as possible from nearbybuildings or obstructions. While thefeeder should be kept as short aspossible don't forego a good posi-tion for the antenna for the sake of ashorter feeder.

Taking Fig. 3 as an example, ifthe centre third of the wire is as highas it can be then the ends can droopdown vertically, or be part of theguying system, with the centre por-tion sloping down from a singlesuspension point such as the top of apole. Such an arrangement is oftencalled an "inverted-vee" which it isnot. If the wire is straight andreasonably horizontal then, if it is ahalf wave long, the radiation will bemainly at right angles to the line ofthe wire. If the ends do droop thenthe pattern of radiation, or polardiagram, will be modifiedsomewhat.

Construction

The cost of experimenting with wire -antennas is virtually nothingalthough it does depend to some ex-tent on whether you are transmittingor just receiving. If transmittingthen a little more attention needs to

Fig. 3 (a) the perfect textbookantenna, in space unaffected bysupports or nearby buildings etc.(b) down to realities with as muchof the antenna in the clear aspossible, with cords to adjacentsupports as convenient. In practiceit may not even be possible for the

antenna to be horizontal at thecentre. (c) Both sides of a dipolemay be taken down towards theground, again using anyanchoring point available. Theincluded angle at the top shouldnot be less than 90 deg. (d) Wirescan slope to fit the site

be paid to the adequate use of insu-lators at the ends of wires wherehigh voltages appear, and whichMUST be kept well clear and out ofanyone's reach.

The more usual egg insulator,or expensive pyrex glassequivalent, can be replaced by apiece of plastic tubing a few incheslong, with holes drilled at least linin from the ends, for anchoring thewire antenna and the supportingrope or string. A similar piece oftubing can be used at the centre ofdipoles and the like although apiece of flat plastic is more appro-priate, Fig. 4. Keep an eye open,especially in offices, for the cast-offbodies of so-called "glue pens"which are ideal for insulators. Aninsulator must always be usedbetween any point on the wire and asupport. There are those who woulduse nylon string or rope tying itdirect to, say, the end of a wireantenna, but I still prefer to be sureof the insulation, especially in wetweather, and fit an insulator.

If open wire feeders are to beused their construction is auite sim-ple, Fig. 5, using the discardedbodies of ball point pens forspacers. They are very light inweight and not unsightly. A smallhole is drilled near to each end forthe thin wire used to attach thespacer to the feeder wire. Thismethod of construction allows thefeeder to move about in the windavoiding wire fatigue and breakagewhich can occur with a more rigid

construction. Generally such openwire feeders will be part of a tunedsystem so the spacing of the feederwires is of no great importance, sobetween 4 and 6in is the usualspacing. The binding wire can bethe aluminium wire used around thegarden for supporting plants etc andthere is also a similar green plasticcoated iron wire which is quitesuitable.

Actual construction of openwire feeders is best undertaken out-side where the two wires can bestretched out straight, tying one endof each, about the correct distanceapart, to a convenient support. Thespacers are fed on at the other endof the feeder and spaced outroughly at about 2ft intervals. Cut astick of wood to about 2ft long anduse this to adjust the spacing apartfo the spacers as they are wired on tothe feeders. There is nothing moreunsightly than open wire feederswith spacers at random intervals!

Taking feeders through windowframes can sometimes be a problembut for low impedance types asuitably sized hole may be drilledthrough the frame, perhaps at apoint that can be out of sight behinda curtain. Always drill the hole sothat it is sloping downwards from theinside to th eoutside and thus pre-vent the ingress of rain etc. Someform of plastic filler will come inhandy here. For open wire feedersthe ball pen bodies can be pressedinto service once again, making

HAM RADIO TODAY APRIL 1983 9

them a press fit in two holes in thewindow frame, at the same spacingas the feeder wires. A tidy tip; tie aknot on the inside end of eachfeeder wire to tkae the strain,adjusting them so that the spacersoutside are more or less horizontal.

Choice of feeders

Apart from open wire feeders the re-maining choice will be either flattwin feeder or coaxial, the formerbeing either 70 or 300 ohms impe-dance, the latter 50 or around 70ohms. Coaxial cable can be quiteheavy and will drag down the centreof an antenna unless it can be sup-ported by a mast or other support.On the other hand flat twin feeder isquite light.

Since the input impedance ofmost receivers (and the output im-pedance of transceivers) is an un-balanced 50 ohms it seemsreasonable to continue the link tothe antenna with unbalanced coax-ial cable. Ah, ha! say the experts,this is where a balun (balanced -to -unbalanced) transformer should beused, generally at the top of the un-balanced coaxial feeder where itjoins the balanced antenna, other-wise the polar diagram of the radia-tion will be distorted. In practice,however, the chance that the halvesof a dipole are balanced to earth isvery remote when one takes intoaccount nearby buildings or otherobstructions, trees and the supportsfor the dipole, and the varying com-position of the ground below theantenna especially if it is a long one.In such a case a balun is a waste ofmoney.

Baluns tend to be justified inrotary beam antennas which are in-herently balanced systems fed byunbalanced coaxial cable, with afairly narrow forward beam whichshould be symmetrical but 'whichcan "squint" if a balun is not used..but that is another story.

The performance of coaxial,cable on a receiver can also becalled into question. With a balanc-ed feeder any local interferencepicked up tends to be cancelled outbut on unbalanced coaxial feederthis effect is less pronounced. Inparticular the radiation of timebaseinterference from TV receivers hasbeen largely cleared up on manyoccasions by the use of flat twinfeeder. In severe cases screened

Fig. 4 A piece of plastic sheet, atleast '/4 in thick, forms base forantenna feed point. The feeder ispassed through anchoring holesand over top of plate to anchorposts where the wires are solderedto the antenna wires. This methodis absolutely essential with coaxialcable to prevent the ingress of rainand moisture

twin flat feeder has proved to bevery effective, the screening beingearthed at the receiver.

The copper wire for con-structing wire antennas can be ob-tained from several sources, such asold mains transformers, the smallerdiameter wire of some secondarywindings being particularly useful.It will be necessary to remove anyfittings on the transformer,including the laminations, leavingonly the bobbin and windings. Thinplastic -covered bell wire can bebought from Woolworth stores, if

necessary, in useful lengths. Anyjoint made in the antenna wire must

Fig. 5 Method of wiring plasticspacers to open wire feeder

be sound mechanically beforesoldering and covering with insu-lating tape or compound. The so-called self-adhesive tape isexcellent as it will not come undoneas ordinary insulating tape doesafter a while. The soldering of thejoint is an absolute must withtransmitting antennas.

If one already has a long mainslead for use with gardeningappliances it is a good idea to makeup an adaptor so that the shacksoldering iron can be used outsidefor soldering joints in wire. The ironneeds to be something a bit moresubstantial in terms of wattage thanthose used with PCBs! 60W or so. isdesirable, while the soldering gun isprobably the ideal, as has beendiscovered over the years.

If fairly long lengths of multi -way multi -coloured flat cable, asused for the interconnection ofmodules, can be obtained these canbe stripped down and joinedtogether to form one long wire.Short lengths make the number ofjoints necessary rather burdensome.Other multi -way cables can betreated the same way. After a whilequite a lot of copper wire will haveaccumulated (frequently half wavesfor 20m complete with insulators!)which makes experimentation withnew antennas very easy. A versatileATU for use with the tuned feedersis essential of course, when one hasthe comfort of knowing thatwhatever antenna is up at anymoment that it is tuned "on thenose", as they say, and giving of itsbest. With coaxial cable feedersthere is always that suspicion thatthe matching may not be quite rightin spite of what the SWR indicatormay show.

Antenna supports

Few of us are able to organiseseveral tall masts at the appropriatelocations in a very large garden tosuit our antenna plans, so we have tomake do with what is available.Obvious supports are chimneys, ifyou can reach them, trees, garagesat the end of the garden to whichpoles can be fixed to increase theheight of a wire, and so on. One end -of a wire is generally fixed, as highas possible, to the house with theother end going off down to the endof the garden. It is very importantthat one end of any wire should beable to move about to take up any

10 HAM RADIO TODAY APRIL 1983

movement of the supports, especial-ly if these are trees. Otherwise theantenna will break and come downin the first strong wind.

While pulleys are highlydesirable provided that they can befitted where they are wanted, whichis not very often except at the houseend, then a rope or cord thrown upas high as possible over the branchof a tree will suffice, with a weight atthe bottom of the rope to take upmovement in the antenna wire.Getting the rope over the branch isnot too difficult provided one goesabout it systematically. Nylon cordis probably the best, making surethat it is long enough to go over thebough and back to the ground at'least. Tie a small but heavy objectsuch as a nut from a 1/2in diameterbolt to one end of the cord and thenlay the cord out behind you, free ofany knots, so that it will not getcaught up when the weight is thrownup. Wearing gloves, or you will geta neat groove cut into your fingers,hold the cord a few feet from the nutand swing it back and forth finallygiving it a sharp swing upwards andletting go of the cord. Do not swingit in a complete circle or accuracywill be sacrificed.

With a bit of luck the weight willfall through the tree back to earth. Ifnecessary, a heavier cord or ropecan not be tied to the lighter cordand drawn through. If the rightbranch was not reached pull thecord through and try again. Do notattempt to pull the weight back up orit most certainly will jam in a branchand be lost. One last point, makesure there are no windows behindyou when throwing the weight!Children and cats and dogs are alsounwelcome visitors at this timeunless a young lad can be per-suaded to climb the tree whichmakes it all so very much easier!

A bow and arrow can be veryeffective but only in the hands of anexpert, with particular emphasis onthe safety aspects, such as the lan-ding area of the arrow at the otherside of a tree or support. Make sureit is on your own property and awayfrom greenhouses and the like.Again, be careful with animalsaround. My own cat loves chasingthe ends of wires moving across thegarden and just won't let go! I'msure that one day I'm going to findher dangling at the centre of a wireat 50ft!

Z EPP

0.95 X/2

TUNED DIPOLE -

re --0.94 X/2----.

r 2

END -FED HERTZ

300-600A LINE

END -FED TYPES

0.95 X/2 -Pi

HALF -WAVESTUB- FED

SHORTED

300-600.0. L NE

FOUR -WIRELINE -FED

300.0 TWINLEAD

© LOW SIDE OPENEDIN CENTER O

0.95 x/2 -

600 A LINE

0.94 X/2 -04

TWINLEAD 2 -WIRE DOUBLET"FOLDEDDIPOLE OR `FOLDED DIPOLE

300 OHM TWINLEADANY LENGTH

0.95 X/2

STANDARDDIPOLE

2" OR 6"FEEDERSPREADERS 0

DELTA MATCHEDDIPOLE

STUB -FED

0

0.95 A/2 -8-

300-600 OHMLINE OPEN

QUARTER -WAVESTUB -FED

IP-- 0.95 X/2 --PI

150 A TWINLEAD0.193 OF FREESPACE WAVE-LENGTH OR0.77 OF X/4

0TWIN LEAD

FED

300 A TWINLEADANY LENGTH

0.95 x/2 -

300 OHM TWINLEADANY LENGTH

O

0.95 X/2 --Awl

CO -AX FED

600 OHM LINEANY LENGTH

1.4-0.95 A/2 --Pi

FED

D=14% OFTOTAL LENGTH

75 5 TWINLEAD t N 14 WIREANY LENGTH

CENTER -FED TYPES

There are a lot more ways of feeding a basic dipole structure thanby just using a balun and standard coax. The disadvantage of thestandard balun solution is that it will only cope with aerialsoperating at around their naturally resonant frequency: ie wherethe impedance approximately matches between dipole structureand the termination, and the balun unit is not called upon to dealwith any reactive components. A dipole of no particular lengthacross the top can often be tuned remotely in the shack simply byusing an open wire feeder and a balanced output type ATU. TheSWR on the feed line between ATU and dipole is unimportant.

HAM RADIO TODAY APRIL 1983 11

Operatingon

Many amatuerstend to imagine that23cm contacts are onlymade in general byone station telephoninganother, arrangingappointments on 70cmfor beam alignmentthen switching overto 23cm for a contactwhich could equallywell have been madeon a lower frequency.

This legend was indeed true eventen years ago, and the earliest in-novators, including such famouscallsigns as G 5DT, G 2RD and G3FPwere often heard attempting theirlink ups using 70cms for talkback inthe early 60's. They were pleased toget a useable range of ten or fifteenmiles using home made aerials andall valve transmitting and receivingequipment which each stalwart hadcarefully made in his own home.

In 1983 23cm as a band haschanged possibly more than any

By Angus McKenzieG3OSS

other lower band, with a populationat least ten times greater than it hadsix years ago. If we contrast a 23cmstation of yesteryear with one of to-day, comparisons are absolutelyfascinating. Typical transmittedERPs are at least 20dB higher andreceiving systems, again includingaerial gain, are at least 25dB better,if one ignores the very top stations ofsome years back. These staggeringimprovements have shed an entirelynew light on the band.

It is now not unusual to have

QSOs of 100-200 Kilometres quiteregularly on SSB which areequivalent to many 2m SSB QSOs.Unusual propagation is often ex-perienced on 23cms allowing con-tacts with many other countries, andright over obstacles such as very tallhills which would have been regard-ed as insurmountable ten years ago.23cm can now be regarded as a veryreasonable band. This article waswritten in the hope that my own en-thusiasm will influence you to have ago on this fascinating band.

12 HAM RADIO TODAY APRIL 1983

Operation

Most QSOs on 23cm are on CWor SSB. In past year if telephony wasrequired, eg for class B licencees,FM would be used by tripling upboth frequency and deviation 70cmcare being taken to avoid overdeviation.

Although a sizable proportion ofcontacts are made on the band byfirst establishing contact on 70cm,beaming up and then transfering tomicrowave, today it is more commonfor QSOs to result by answeringCQs on the band, or by calling induring, or at the end of an establish-ed contact between two otheramateurs. Many regular skeds onthe band tend to stir up activity,Sunday Mornings and Mon-day/Tuesday evenings being par-ticularly active. The 23cm en-thusiast tends to look at hisbarometer and TV weather mapsvery regularly and will make a runfor his gear if he feels that a tropoduct is becoming likely.

Microwave addicts are used toscratching around in the noise fortraces of weak signals and will beturning their beams roundround to find that elusive DX con-tact, and once a station has beendetected, no matter how weakly, theodds are that turning the beam willconsiderably help. By the time hereturns to the CQ call he may befairly easily receivable by the otherstation who will then turn his beam.For this reason, CQ calls are usuallymuch longer, but with fairly fre-quent breaks. Patience is un-doubtedly a virtue on this band, andit is surprising how frequently areasonably well sited station willreceive a reply to his CQ call on1296.200MHz. This frequency is us-ed for both CW and SSB calling.

Beacons

Of tremendous importance arethe 23cm beacons transmittingthroughout the UK and continent ofEurope between 1296.800 MHz and1297.000 MHz. Note the beacon listfrom which it can be seen that moststations in the south and Midlandsshould be able to receive at least twoof them. I normally receive at leastfive under the worst conditions,seven on average, but up to 20 whenall hell is let loose! Alas, these

beacons have a habit of goingwrong, and many an amateur hastorn his rig apart when a beacon hasblown itself up. GB3DUN has beensignificantly weaker for around 18months, than it used to be, whereasseveral others seem to go on and offseveral times a year. GB3BPO issupposed to be an extremely ac-curate frequency standard, but itsFSK deviation is both very wide,and wobbles around like a jelly.

These beacons are superb in-dicators of band conditions, andwith me, GB310W can vary from aminimum of S7 to a maximum of20dB over S9. The one beacon thatalmost goes through the roof insignal strength in very good condi-tions is GB3BPO approximating toperhaps 40dB above the level re-quired for S9! When this occurs onestarts hunting for continentalbeacons, and PA9QHN can comeup from below noise to 5 and 9within an hour, similarly ON5SHFcan also indicate an opening to thesoutheast when it becomes possibleto work through to Switzerland andeven Czechoslovakia and Austria.

In September 1982, I workedfour SM stations including one in JRsquare on an island (GotlandIsland) off the east coast of Swedenat around 1340 kilometers. On thesame unforgettable evening I work-ed three OZs, and many PA and DLstations as well as some new coun-ties in Wales. Once you are knownon the bands, you will probably findthat a friend will call you up to warnyou of an opening if you are notheard transmitting. It was G8DKKin Luton who kindly warned me onthis occasion.

Portable

There is much enthusiasm forgoing out portable on 23cm, even ifone only has 2W output and aJaybeam 15/15. Many continentalstend to belt for their highest localpimple at the slightest sign of a duct.It is quite incredible how so manyamateurs seem to appear fromnowhere when good conditionsbegin. Whilst many outstandingSSB QSOs occur, the use of CW isalmost essential if you want to doreally well on the band, and anperusal of the call signs who haveobtained the 23cm senior awardshows that all five stations are CWoperators, although nine class B sta-tions have achieved the standard

award without CW. G4KIY has veryremarkably achieved a 40 squaresaward which would be good goingfor many stations on 2m let alone70cm.

Lunatic

Many stations in an attempt towork some new county will makeregular skeds over a period of aweek or so every night with co-operative DX station, and it is amaz-ing how frequently patience isrewarded. I remember how Petra,G4KGC, in Towcester,, Northants,managed to work a South Wales Sta-tion eventually after many attemptsby bouncing off, it is assumed, lurk-ing aircraft flying high up across thepath in one of Petra's most difficultdirections. I remember my firstQSO with Northants, which tookaround two hours copying one letterat a time on CW! The real DXhounds on this band, includingmyself, are probably rated by manyothers as complete lunatics. Buteveryone has his poison!

Almost all normal operating isbetween 1296MHz and 1296.4MHz,and even in openings, almost all theactivity is within 100kHz of the call-ing channel. ATV is becoming morefrequent on the band, but ratherlower in frequency, and there is somuch bandwidth available thatmany new modes are being con-sidered away from the normally us-ed frequencies. While you may getquite a lot of pleasure if you are in amoderate location and runningrelatively low power, it must be em-phasised that really good antennasystems, very high quality cable andgood receiving systems are vital ifyou want to take to the band veryseriously. This is not to say that asurprisingly modest system cannotgive the odd amazing DX contact inan opening, although such a systemwould normally give very disap-pointing results by comparison towhat is now regarded as average onthe band.

Propagation:

To describe 23cm propagation as"line of sight" is about as innaccurateon 23cm as it would be to use thesame definition for 2m. What is par-ticularly fascinating about thehigher band is that while auroraland meteor scatter propagation isvirtually non-existant (OK, I'll pro -

HAM RADIO TODAY APRIL 1983 13

bably be wrong soon!), 23cm is farmroe susceptible to odd ducting,tropo scatter and hill fringing thanis 2m. I regularly work G 3WDG andG4KGC in Towcester despite it be-ing only an average direction for meand a very poor one for thembecause of a large hill immediatelyto their south. Signal strength canfluctuate by 20dB many times. aminute, and we believe these aredue to variable contributions fromcloud reflections, aircraft, troposcatter and possibly hill fringing.Other than with tropo ducting, it isvital to have reasonable poweravailable and a superb receivingsetup to copy very weak scatterreflections. Very frequently ductson 23cm occur over great distancesof perhaps 500km when conditionson 2m are barely above average,although the really big ducts, suchas occured in September 82 havealways coincided with major ductson the lower bands. Under suchconditions, the received 23cmsignals can actually be strongerthan their lower frequency counter-part. It has often seemed to me,since I improved my station in 1981,that most DX is either clearly there,or virtually inaudible. Relativelyfew QSOs are on the verge of noiseat considerable distances. This istotally different in my experience to2m DX where I have frequentlyscratched around in the noise to getsome rare station.

Fog, mists or rain do not seem tosignificantly affect local propaga-tion on 2m, but on 23cm some veryodd effects can occur. I have knowncases in which there is a tropo ductabove localised fog with the resultthat all signals from all directionsseem to be very strong indeed, withonly minor variations with aerialdirection. Having discussed thiswith some other microwave en-thusiasts who have experienced thesame oddity we all assume that thetop layer of fog refracts microwavesignals downwards into the top ofthe antenna, hitting the diopolefrom above. On one occassion,when the effect was particularlymarked, I actually thought myrotator had broken down.

Equipment

DX stations on 23cm can beremarkably strong, even when theyare running only 1W output on SSB,

and GU3KFT was up to 5 and 9+201B for hours at my North Lon-don station. A particular GW por-table, running only 1W into an omnidirectional Alford slot, was receivedat 5 and 9+. These contacts typifythe fact that 23cm conditions aremuch more variable than they areon 2m, it is this that makes the bandso vary fascinating.

The crudest equipment that canbe easily used on 23cm is a simplevaractor tripler from 7Ctrn to 23cmfor TX, and a converter for receive.

Triplers

Most stations have started on theband with a fairly long length ofcoax up to an antenna which wouldusually be a single JVL loop Yagi, aJaybeam 15/15 beam, or perhaps asingle 23 element Tonna. All toooften the changeover relay betweenTX and RX is in the shack fed byrather inadequate UR67, which willhave a loss of around 5 to 10dB.Transmitted ERPs will be rather low,and the received system noisefigure, with no RF pre -amp install-ed, can be effectively as high as 16to 21dB!. The average tripler on TXmight give an efficiency of 45% atbest, but many have been incorrect-ly set up. Unfortunately, it is uselesstrying to tune one up using a normalwatt meter on the output, for youmay tweak it up as a doubler rathera tripler.

If you have a spectrum analyseravailable to you, then this should beused with a suitable attenuator loadin which case you will be able to nullout unwanted harmonics as well aspeaking up the required one. I havefound that the tuning points of thevarious capacitors in an averagevaractor tripler vary considerablyfor maximum output dependentupon the amount of applied power,and a tripler set up at lOW inputmay well be very much less efficientat 5W input and, surprisingly, viceversa. If you can mount a highpower device on a good heat sink, itis possible to get 20W output from atripler with 40W input. While this isrecommendable for CW, the varac-tor may not last long with FM.

Receiver or system noise?

On the receiver side, it is no useadding an RF pre -amplifier straightin front of a ring mixer for, even ifthe pre -amp is a very good one, it

will not only have to have a veryhigh gain to overcome a normalmixer noise, but both the requiredfrequency and the image frequencywill be amplified, and the systemnoise figure will thus bedeteriorated effectively by 3dB. A20dB gain GaAsFET pre -amp havingan inherent 1dB noise figure, inter-connected with a ring mixer having10dB noise figure, may give you on-ly a 5dB noise figure in the system,ignoring coax cable losses. It isessential to use either a cavity, orinter -digital filter in between thepre -amp and the mixer to removethe amplified image frequencynoise. Since it is much easier tocope with 2 x 144MHz image offsetthan 2 x 28MHz, very few stationshave persevered with 28MHz IFs.

An enormous improvement canbe obtained if the entire receiverpre -amplifier (and even mixer sec-tions) can be put at the top of themast, driven by a changeover relayof very low loss. The entire systemnoise figure would become perhaps2dB, using the same pre -amp andinter digital filter/mixer as opposedto perhaps 12dB equivalent with thepre -amp in the shack without filter.Such a system can be further im-proved either by using a lower losscoax, eg Andrews LDF 4/50, or byhaving a higher RF pre -amp gain atthe mast head. Around 23dB gainmight be required to off -set the lossof a UR67 cable of 25 metres lengthinterconnected with a transverter/-interdigital filter having a noisefigure of 3 or 4dB. The formulashown in the figure will enable youto work out your system noise figurefrom antenna relay through one ortwo pre -amps into a transverter, andincludes allowances for cable lossesand any inter -digital filter loss. Notethat noise factor and power gain orloss as a multiple should be entered,and not dBs of noise figure or gain.

Up in the air

One useful way of gettingstarted on the band is to put thetransverter at the mast head. Veryshortly, Microwave Modules will beincreasing the output of theirtransverters to around 2.5W, with areceiver noise figure of 1.9dB. If

you have a very long cable betweenmast head and shack you might evenbe better off with this configuration,unless you are going to run morethan 15W or so in the shack. Don't

14 HAM RADIO TODAY APRIL 1983

forget to weather proof thetransverter by using car gasket seal-ing compound around all screwsand in between lids and boxes. Bevery careful to weather proof allconnectors used as even a slightamount of moisture in 7"Arm cablescan increase losses quite markedly.By having the transverter at the top,you can feed 144MHz signals up thecoax with only a fraction of the loss.You will be amazed that even 21/2Wat mast head and a decent receiverin the transverter will give you goodresults with a high gain aerial. Hav-ing played with many aerials on theband, my own experience is thatfour 23 element Tonnas on a Tonnaframe with a power divider seems tobe the best antenna, unless you canput up a large dish.

Running QRO

Although phenonenal DX hasbeen worked by many amateurs withonly a few hundred mW at the masthead, there is of course a great ad-vantage in running high power. It isnot so much that you need the highpower to have the contact itself, butit will help you to be heard if youbeam, or another station's beamheading, is well off the direct inter -station line. Almost all stations areusing 2C39 valve pa's, or theirslightly better 3CX100A 5equivalent. In a well designed cavi-ty tuned circuit, up to 13dB gain canbe achieved, although more usuallythe average gain experienced willbe around 10dB. It is unusual tohave two valves in series, one asamplifier, while the second is work-ing as a high power PA running atperhaps 50 to 100W PEP output. Youwill have to make a choice betweenrunning a very stable 60W whcihhardly drifts with time, or perhaps100W, in which case you will haveto have easy access to cavity tuning,as they will need retuning as the PAgets hot. I use an extremely power-ful fan which blasts much cold airthrough the entire linear to keepvalves cool, and with power set at60W maximum the PA only requiresretuning once or twice a year,rather than every five minutes!Some superb design for very highoutput linears on 23cm have beenpublished in magazines such asVHF Communications, one designgiving up to 200 W from two 2C39srunning in parallel, whilst anotherdesign employs a ring of six which

gives at least 400W output, as usedby G 4G LN and others.

Changeover warning

I should give a word of warningabout the use of coaxial relays on23rm. A high quality relay whichmight give 50 or 60dB isolation bet-ween TX and RX ports on 2M maygive only 25dB on 23cm. Some pre-amplifiers are quite likely to blow upif the wrong type of relay is used,and many amateurs hunt for weeksto find a really good relay with 'N'type sockets, and which shorts theRX socket when on transmit.Another useful hint concerns theswitching of GaAsFETS. For theseto last as long as possible withoutnoise figure degradation, the maingates should be biased slightlynegative. If DC power is applied toboth the relay and the GaAsFET onreceive, the GaAsFET should have atime delay built into its power supp-ly so that only a very small DCvoltage appears on it until the relaycouples the input circuit correctly.This avoids instability caused by anopen circuit as the relay is goingover and, once a device takes off, itmay continue to oscillate. You mayfind an entire mast headstallation working perfectly whenyou test it in the shack, but theslightly different capacities or in-ductances in the cabling and anten-nas may cause a problem when youput everything at mast head. Makesure you check it out completelybefore you take your ladders away.

Finally, whilst on the subject ofequipment, you should get to knowyour nearest microwave enthusiastbefore you start fitting pre -amps atthe mast head, for in some areasthere are various harmonics of UHFTV transmiters, or even specialisedradar equipment which can givegreat problems to some types of pre -amp especially if their input coupl-ing circuit is too wide in bandwidth.It is often better to sacrifice a smallamount of noise figure for the sakeof stability and a tighter bandwidth.

Conclusions

In comparing 2M with 2-3rm inlcel it is fascinating that manymicrowave QSOs are at con-siderable distances on SSB, whereasmost average 2M ones tend to bemore local. This is partly due to thefact that there are far fewer

amateurs who are active on 23cm,and therefore you have to look fur-ther a field for QSOs, and partlybecause the average 2-1rm addict ismore likely to have a aerial systemwith a typical gain of 20dBi. Don'tbe put off 72cm if you hear no activi-ty; you may have to get used to fin-ding out where it is. As there aremore beacons on 23cm than 2M, it isusually easier to ascertain bandconditions. There is very little FMactivity on 2nrm as opposed to 2M,although quite a number of mobileexperiments on SSB and FM havebeen made. You can be sure thatyou will get a tremendous welcomeon 22rm, and technical expertise iseasy to find on the band. In-terference is minimal, for bothhousehold devices and car ignitionhave hardly any microwave output,and only occasionally do I pick upignition from an incredibly badlysuppressed passing "banger". Ther-mostats should not give trouble, andbecause general interference is solow into the aerial, you will almostcertainly be able to pick up solarnoise, and many amateurs make apoint of measuring this in the earlymorning or at sunset to have a lookat the state of the sun. Moon bounce(eme) is very effective, and I haveheard some astonishing cassetterecordings made by G3WDG inwhich, using a dish, he received.signals at around 20:1B above noisebouncing off the moon. I have heardso many stories of amateurs workingastonishing DX within a week ofstarting up on the band, and so Isincerely hope that you will be en-couraged to have a go onmicrowave. Getting going isnowhere near as difficult as youmight have thought.

23cm Beacon List

GB3NWK 1296.810GB3BP0 1296.830GB3FRS 1296.850G B 3A ND 1296. 870GB3DUN 1296.890GB3CLE 1296.910GB3MLE 1296.930G B 3EDN 1296. 990PAOQHN 1296. 990ON5SHF 1296.880DBOJO 1296. 854OZ7IG Y 1296. 930SK6UHG 1296. 925DB OVC 1296. 920

AL51BAM77Ja 57JZL63BZL 08EYM 48HZN32BYP 05GYPO5GBK391DL48AG P23CFR29GF0511

HAM RADIO TODAY APRIL 1983 15

Formula and details of use for calculating system noisefigure from masthead preamp to transverter inclusive

Ft=Fi(1/G 1--2-1 +

G1

(F2-1)

G1.G2

(1/G4) -1

Gl.G2.G3

(F3-1)etc

F, = overall system noise factor from first pre -ampinput to transverter.F1 = noise factor estimated for first pre -amplifier.G1 = power gain of first pre-amp (NB not in dB).G2 = gain of cable inter connecting first and secondpre -amps (entered either as 1, or as a fraction if cablepresent).F2 = noise factor of second pre -amp.G3 = power gain of second pre -amp.G4 = gain of second interconnection coax betweensecond pre -amp and transverter input (allow also forinter -digital filter loss when placed here).F3 = transverter input noise factor.NF (noise factor) = 10 (0. 1 x noise figure) where noisefigure is in dBs.GP (power gain) = 10 (0.1 x GL) where GL is powergain in dBs. (NB cable loss is negative dBs and Grwould be a fraction below 1.0).

23cm equipment used by G3 OSS.

1. MM 1269/144 transverter with TX output driving at1.25W feeding linear amplifier.2. Linear amplifier having three 3CX100A5 amplifierfeeding a second 3XC 100A5 PA at 60W output.3. 25 metres Andrews LDF4/50 cable run, then 8metres FSJ4s for turning radius up to mast head.4. Through relay box (completely weather proof) topower divider and four 23 element Tonna yagis onsquare mounting frame at approximately 68ft aboveground.5. Mast head relay box includes Mitusbishi GaAsFETand MRF901 pre -amp.6. Around 90ft of UR67 receive down lead.7. Interdigital filter, then receive input to MMtransverter.8. Transverter is fed from another transverter withinput on 28MHz and output 144MHz with receivesection having very low gain.9. Basic transceiver is TS830 Trio which controls relayswitching box selecting TX RF and RX RF to varioustransverters for other bands.10. Independent receiver, NRD505, which can betuned on any receive converter output for cross bandworking, or FM reception.11. 28MHz TX output to transverters feed through RFcoaxial potentiometer for setting required drive level.Full power is obtained on all bands when this pot isflat out, with transverter internal gains adjustedaccordingly.

144MHz 80 WATT LINEAR AMPLIFIER designed for the FT290R or any rig having output of 2f -3iwatts. FM/SS 8 operation power requirement for full output 13.8v at 13 amps. Straight throughoperator, when switched ott. (wilt and designed by us to professional standards, colour storm grey,matt black heat sink E941.011.27-30MHz RECEIVER PRE -AMP liven up that old Ho. with one of Mese superb boards many soldto date, uses duelgate moslet for super performance gain variable to 25db, sue 40 r 60mm readybuilt and tested. ONLY E8.00.N BEM ADAPTER for the FT101 lup to "E" model) gives FM on Is and Ac on all bands, only onewYe to solder to clarifier line. no holes to drill, no boards to fit inside F7101, built in tone burst for usewrth "transverter". Still the beet available E70.00.MOTOROLA CAR CASSETTE PLAYERS model 401 and 8L512 etc. these are warranty returnsand need repair. Guaranteed to be complete, supplied with circuit E5.00.CRYSTAL FILTERS: STC LOU/445/909B 10.7MHz v 7%KHz BW @ 3bd 910 ohm imp. IK for2mtr FM ex -equip. £4.00.ITT024DE 10.7MHz z 3 iKHz BW @ 3db inn,. 810 ohm. New. Only E1.00.CATHODEON BP4133 10.7MHz SS B Lab only available new E5.00.21.4MHz o 7 i6 Hz 13W 0 3db OK FM. imp approx 2k ohm new £4.00.6.0MHz TOY OCOM ± 6KHz BW @ 3db OK FM imp 2k ohm. ex -equip. £3.00.

BOLT -IN FEEDTHROUGH CAPACITORS 2BA thread 1000p1 500vw Brand new and made for usby famous manufacturer. ONLY 40p each.SOLDER -IN TYPE 1000pf 500wv 3.2rnm hole 67p per 10.

35688 DUALGATE MOSFET ideal replacement for most 2mtr Tcvr RF amps. Only 1db now and26db gain, also OK for 70crns PRICE REDUCED £1.00 se. or two for E1.75.3SK87 same as above put /looms 3db more gain E1.00 ea.

TRIMMER CAPS airspaced 9mrn sq. 15p1 20p. 30pf 3513. solder in tubular ceramic 1-6pf 759 for10.FILM TRIMMERS 25p1 10mm do. 10p ea. 32pf 10mm dia. 120 ea 60pf lOmm de 20p ea. 7mmsq. 1-10pf 12p ea.CERAMIC COMPRESSION type 10-80pf PC mount OK 2mtr PA to 40 watts 15p ea. 10-40pf PCtype 10p ea.

LOW PROFILE RELAY OK for ae. switching @ 2mtrs will handle 75 watts RF 2pco 12v coil Ii3.00.FERRITES - bag mixed cores and beads approx 150 E1.00.10.7MHz HC18/U crystal OK for FM detector IC etc. E1.50.TBA120A FM IF amp -detector IC 40p.TDA1010 9 watt 12v audio IC 9 pin s.i.l. with data and circuit E1.85.MINIATURE TOGGLE SWITCHES spco 059, 2pco centre off 70p.

2/411013 VHF RF POWER TRANSISTOR min. 30 watt out @ 2mtr for 6 watt input suitable for FMor SSB supplied with circuit of FM 2mtr amp 6.50.

TF144H/4S MARCONI AM SIGNAL GENERATOR 10KHz to 72MHz in 8 switched bandscalibrated output 2uV to 2V into 50 ohms. Modulation adjustable to 80%, internal crystal calibrate,very good condition fully checked 1110.00 buyer to collect by arrangement.TF10111113/1 Signal generator 10 to 480MHz AM/FM P.O.A.TF8010/11 AM SIGNAL GENERATOR 10 to 480MHz P.O.A.S121 WAYNE KERR AUDIO OSCILLATOR 10Hz to 120KHz, 11 switched ranges output 0 to 3Qvolts into 600 ohm. Al. has high imp. output. mains input, valve type circuit tested and in goodcondition ONLY 00.00 buyer to collect by arrangement.SEND FOR LATEST LIST OF COMPONENTS AND TEST EQUIPMENT at

give away pricesMail order only or callers by appointment, prices include VAT. Please add 60p post and packing.

A.H. SUPPLIES122 Handsworth Rd., SHEFFIELD S9 4AE

Tel: (0742) 444278

I

L

THE WAY AHEADSLIMLINE MASTS or LATTICE TOWERSFIXED TOWERS or MOBILE TRAILERS

PORTABLE MASTS or WINDOW MOUNTINGYOU NAME IT! WE PROBABLY MAKE IT!

JUST SOME DESIGN FEATURES TELESCOPIC TILTOVER FOR EASY ACCESS. VERSATILE WALL OR POST MOUNTING. SAFETY LATCH TO RELIEVE CABLE. SIMPLE WINCH OPERATION (Single and Double). UNIQUE 15FT SECTIONS FOR EASY TRANSPORT. OPTIONAL HEAD UNITS (Extra). HOT DIP GALVANVED FOR PROTECTION (BS 729). ENGINEERED TO B.S.I. STANDARDS.

WIND LOADING BASED ON CP3 CHAP V PT. 2.

AT MANUFACTURERS PRICES! NO MIDDLE MENIA FEW MODELS FROM OUR WIDE RANGE

THE VERY POPULAR SPA30 SUMUNE MAST, Unobtrusive,;Telescopic, Mover, up to 31ft.. SM3OVAIA (Wall Mount)L230.00. SM3OPM (Post Mounting) E241.00. OptionalReducer Tube RT1 C1250. Rotor Head RH1 £30.50.Ground Socket GS1 £23.60.

LATTICE TOWERS - TELESCOPIC - TILTOVERPost Mounted (PM) Well Mounting (WM)AT 32PM 'Mini Tower' up to 32ft £350.00AT 42PM Series 2 up to 44ft £506.00AT 52PM (Heavy Duty) Series 2 up to 56ft E599.00OVER 50 TYPES! WE JUST CAN'T GET THEM AU. INN

, Send SAE (94) for full details of these and many -other Akron Products. - Callers welcome. Open

7,- Mon -Fri 9am-5pm, Sat 9am-12.45pm.WET

BESTVALUEDESIGN

-WE MAKE

NDE

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Prices include VAT & UK Carr. C.W.O.THE ONLY MANUFACTURERS OF ALTRON PRODUCTS

ALLWELD ENGINEERINGUNIT IX 232 SEUIDON ROAD,

SOUTH CROYDON, SURREY CR2 6PtTelephone:

01-680 2996 (24 hr)01-681 6734

16 HAM RADIO TODAY APRIL 1983

There are a variety of differentstructures ranging from a simplewooden pole to a multi section, 120foot tower which could be used tosupport an aerial. However practic-ality will generally rule the day andfinally dictate the type of structurewe can erect. The first thing to con-sider is whether the mast or toweryou are thinking of erecting will re-quire planning permission.

Planning consentIn general, under planning law,

any mast over about 3 metres highcould be classified as a "structure"and so require planning permission.However, the views of planningauthorities on the subject of aerialmasts can vary from one localauthority to the next so it may behelpful to ask around. Radioamateurs in the local radio club mayhave already had some experiencein trying to get planning permissionfor an aerial mast and should beable to give you some useful tips. Insome local authority areas, the plan-ning laws can be very rigidly ap-plied and yet in others a 'blind eye'is turned on some types of aerialmast that are not too obtrusive, orwhen the neighbours are not com-plaining. There are no hard and fastrules to go by and so it is probablybest to ask around.

If you feel that you will have tomake an application for planningpermission, then the following hintsmight be helpful:

a) Most local authorities produce anexplanatory booklet explainingthe various aspects of planninglaw. Try and get a copy to studycarefully.

Part 3Choosing the right

tower

By Alan Barraclough G3UDO"

b) Refer to your structure as a'Mast', the word tower may con-jure up visions of a large unsight-ly structure.

c) Explain your intentions clearlyand if possible, use scale draw-ings of your property to illustratethe proposed location of the mastand any trees, etc that are likelyto screen the mast from publicview.

d) When any structural work is

needed to be done, such as foun-dations, get professional advice.

e) Home made or DIY structures arenot always popular with planningofficers and should be avoided.Commercially manufacturedmasts are more likely to begranted planning permission.

f) Try and get the consent of yourneighbours.

The next thing to have a look atis the various types of masts and'towers' that are generally availableand could be used as amateur radioaerials. It is beyond the scope of thisarticle to deal with each and everykind of aerial mast in detail, so onlythe most commonly used sorts ofmast have been included.

In general, they fall into twocategories; fixed masts, either selfsupporting or guyed; telescopicmasts which, like the fixed variety,can be either self supporting orguyed structures. Figs. 1 to 6 showsome typical examples of somepopular types of mast that areavailable. The simplest mast ofcourse is just a tubular pole ofaluminium or steel held vertical by asystem of guys as in Fig. 1. In someinstances, when more height isneeded, a number of tubular sec-tions can be joined together andguyed to make a taller mast. Simpleguyed masts of this type are relative-ly cheap to put up to heights of 50 to60 feet but at greater heights, thedifficulties in erecting and guyingthe structure increase thus raisingthe cost. The real drawback of thiskind of mast is that it cannot be easi-ly or quickly raised or lowered andso they are more suitable for 'perma-nent' installations.

Fig. 2 shows a different type of

HAM RADIO TODAY APRIL 1983 17

fixed mast which is more commonlycalled a lattice tower. Generallyconstructed in a triangular formeither pre -fabricated as a weldedstructure, or made from steel tubewith solid rod bracing. Some makesof lattice mast are available as a kitof parts that can be DIY assembledusing bolts and nuts, made up ofpre -drilled extruded aluminium. Athirty foot self supporting tower ofthis type can be a relatively lightweight structure when assembled.Lattice masts or towers as they arecommonly called, offer a muchgreater wind resistance than atubular pole and this means that afairly good concrete base isnecessary. Manufacturers specifythe size of base required and theirinstructions should be followed.Althogh no guy ropes are needed tokeep this type of tower upright, get-ting it up and down can be a majorproblem, particularly with largeaerials fitted.

A simple mast that can be easilyraised and lowered is shown in Fig.3. This consists of a mounting postwith a hinge at the top and a lockingarrangement at the bottom. Anylength of tube, such as aluminiumscaffold tube, can be held in thehinge bracket. This allows the mastto swing down horizontal when thelocking device at the bottom of themouting post is released. The AltronSPI is a commercially available unitsuitable for tubing from 134 " to 21/4 "

ALUMINIUM TUBE-1if." TO 2" DIAMETERUP TO 6 MTR 120FTI

MASTHORIZONTAL

111

ALTRON SP1SWING POST

r

in diameter up to 6 metres long.The bottom section of the

mouting post can be bedded into asmall concrete base and, dependingon the aerial size and tube diameter,the mast can be additionally sup-ported by guys. Retailing at £49.50each, VAT and UK (mainland) car-riage, the AItron SPI can make avery simple and cheap swing downmast for lightweight aerials.

There are two basic types oftelescopic mast or tower: thepneumatic or hydraulic pressureoperated type as in Fig. 4, and thecable and winch operated types,Fig. 5 and 6. The pressure operatedmast, Fig. 4, consists of a number oftubular sections of reducing

UIDE COLLAR AND LOCK RING

EXTENDING SECTION

PISTON AND SEAL

BOTTOM SECTION

AIR

diameter, fitting one inside theother, see Fig. 4A. Although waterpressure hydraulics can be used tooperate this type of mast, compress-ed air is the most common. Fig. 4Ashows the basic construction of atypical pneumatic mast. The sec-tions are generally of aluminiumallay tube with a smooth precisionbore. Each section can be six to 12feet long depending on the overallheight when extended and numberof sections used.

In operation, air is supplied bya pump from an electricallyoperated compressor and enters thebase of the bottom, largestdiameter, section through a releasevalve. The air pressure builds upbeneath the piston at the bottom ofeach subsequent section, forcingthem out so extending the mast. Alocking device is sometimes provid-ed to lock the sections togetherwhen fully extended. Because of theprecision needed in their manufac-ture and the complexity of construc-tion, pneumatic masts are relativelyexpensive, ranging from £400 toover £1,200. Although pneumaticmasts can be self supporting withlight loads, thjey will require guyingif any decent sized aerial is to be fit-ted. Pneumatic masts can be raisedup or lowered very quickly indeedand have a fairly low closed downheight. They suffer from onedrawback when used in amateur ap-plication when they tend to lift for

18 HAM RADIO TODAY APRIL 1983

EXTENDABLESECTION

MAST TILTEDHORIZONTAL

WINCH

CONCRETEBASE

When applying to the localplanning authority, it helps torefer to your structure as a 'mast'rather than as a 'tower'

long periods. Under such condi-tions the piston seal can deteriorateand fail. Replacement of these canbe an expensive business.

Mechanically operated tele-scopic masts and towers are the mostpopular with radio amateurs. SeeFig. 5 and 6. Winch and cableoperating is fairly simple and thereis not much to go wrong with thesystem if it is left extended for longperiods.

Fig. 5A and 5B show a slimlinetelescopic mast consisting of twosections operated by a cable and

winch, mounted onto a ground postset in a concrete base so that themast, when closed down, can betilted down to the horizontal. Thisfeature has the chief advantage thatthe mast and aerial can be quicklyraised up or lowered down toground level even by one person.Telescopic masts of this type, suchas the Altron SM30 are made up oftwo 15 foot sections of galvanizedsteel tube, and all extendable up toa height of 30 feet, excluding therotator and aerial.

This type of mast has a very slimsilhouette and can be self suppor-ting with small HF or large VHFaerials, depending on local condi-tions. Fig. 5B shows the slimlinemast mounted against a wall so thatit can be lowered down away fromthe wall. In small spaces, this issometimes a more practical way tomount a telescopic mast. The AltronSM30 retails at about £240.00 in-cluding VAT and UK mainland car-riage and is unique in that it is madeup of 15 foot sections for easytransportation and low closedheight.

If heights over 30 feet (ex-cluding aerial and rotator) areneeded or large aerials are to be fit-ted then a tower is going to benecessary. Fig. 6 shows a typical

.I:--. _...e....,

m =

..--...--

.--/---- MAST TILTED

HORIZONTAL

_._

..A.....-7.-,

INCH.

4om, =

-.-1.

.1."1_11r 72

telescopic latticelattice tower mounted ona ground post so that it can be liftedhorizontal. Lattice towers are some-times referred to as Versatowerswhich is in fact the trade name ofWestern Electronics Ltd, a firm thatmakes lattice towers. They areusually fabricated from steel tubebraced with rods and extended, aswell as tilted by cable and winch.

When to guy

The 'lattice' sections are usuallyof triangular form parallel over thewhole length. These sections can be20 feet long as made by Western or15 foot long as in the Akron series oftowers by Allweld engineering.Although towers are, by their con-struction, more costly than atelescopic tubular mast price;(ranges from £363.00, the AltronAT32PM mcm tower up to over£1,000) they can carry much largeraerials to heights up to 120 feet.Generally though, at heights over56 feet, they should be guyed. Theground post needs to be set into asuitable concrete base and manu-facturers usually specify what theseshould be. Some sizes of telescopictower can be mounted against a wallwhen space is limited but loads onthe wall should be taken into ac-count on this type of installation.Like the mast, the tower can easilyand quickly raised or lowered aswell as tilted to the horizontal usingthe appropriate winch.

Like any mechanical structure,a mast or tower is designed tooperate within certain load limits;such as wind loads, and in the nextpart, we will look into these.

HAM RADIO TODAY APRIL 1983 19

The FT101 series of transceivers still represent some of the best value formoney to be had in secondhand HF gear.

ak Takinapart the

Even theearliest versions are

worth acquiring whilea few simple

modifications will bringthe sets up to present

day performancestandards. By Harry

Leeming G3LLL

"I'm just ringing up to see if youhave any second-hand FT1O1s instock."

The FT101" must be the mostsought-after piece of second-handgear on the amateur radio market,and as the line seems destined tocome to an end with the demise ofthe FT101ZD, it would seem an ap-propriate time to look back at, anddiscuss, this extremely popular unit.

Yaesu's original sales literatureseems to indicate that the FT101 wasaimed at the Yank who had twohomes, a large automobile, travell-ed around a lot, and wanted a se-cond rig which would run from DCor AC supplies, fixed or mobile.Considering its power and versitili-ty, the FT101's ssize and weight wasa revelation in its time. Old headswagged and predicted that it justwasn't possible, "the power supplyis too small". They were wrong.Hundreds of thousands of users in-cluding now many of the originaldoubters have vindicated YaeSu andthe FT101 has proved to be one of

20 HAM RADIO TODAY APRIL 1983

the most popular, reliable, and easyto maintain pieces of amateur radiogear ever made.

A Brief History of theFT101

Yaesu have graduallydeveloped the FT101 over the years,but have not always clearly in-dicated the existence of design im-provements by altering the model'ssuffix. When servicing, buying, orselling an FT101, it is as well toknow exactly what version one isdealing with, hence it is hoped thatthe following will help. Second-hand values are very approximatebut, for what it is worth, they aregiven as of late 1982 (strange butthey seem to be just about what themodels cost in the first place; whatelse in electronics can you get yourmoney back on after ten years' use?)dates apply to UK sales and are alsoapproximate.

1971 Early FT101 Mark 1 (presentvalue £200-£250). The FT101 wasnot originally factory fitted with the160 metre band but many units weremodified for this by the importer.The earliest model can be identifiedby the absence of any "160" mark-ings on the band switch and by theuse of two output transistors on theaudio unit. The main complaint withthis early version of the FT101 is thatit suffers from cross modulation andreceiver overload - it just "falls topieces" if used with a full-size aerialon 40 metres after dark. It was pro-bably intended for use mainly with amobile aerial.

1972 Late FT101 Mark 1 (present

value L250-£300). This is as aboveexcept that the audio output tran-sistors have been replaced with a21/2 " by 11/2 " Sanyo I.C. which isvery easy to spot on the audio unit ifyou open the lid.

. Marketed as Sommerkamp FT227 in mostContinental European countries

Mark numbers are unofficial and are similarto those suggested by the FT Club in theUnited States - see end of article

Late 1972 FT101 Mark 2 (presentvalue £250-£300). This model looksexternally as above except "160" ismarked on the band switch, thereare larger DC/DC inverter tran-sistors and a larger heat sink is fittedat the rear. Internally new circuitboards give more IF gain and lessRF gain and the RF protection diodeis removed and replaced with a fuselamp. The noise blanker circuitry,which was part of the IF unit in theMark 1, is re -designed as a separateboard and perches on top of theVFO unit. Together with extra filtersto clean up the transmitted signals,these modifications result in a con-siderably improved receiver andtransmitter performance.

1973 Late FT101 Mark 2 (presentvalue £260-£310). This unit is thesame as the earlier FT101 Mark 2but is fitted with an extra receiveaudio pre -amplifier. This smallprinted circuit board, the circuitryof which is given in Fig 1, ismounted behind the mode switch.

1974 Early FT101B (present value£275-£325). The rig is only slightlydifferent from late Mark 2s but isclearly marked on the front panel

"FT101B" and sports two LED's to in-dicate clarifyer and internal VFOoperation. Inside the set the noiseblanker board plugs in behind themixer/high frequency IF unit, andan eight pole SSB filter is fitted toimprove receiver selectivity.

1975 Late FT101B (present valuef300-£350). As above but largeSanyo IC is replaced with smallerunit thus allowing audio pre-amplifier to be removed frombehind the mode switch and incor-porated in the AF unit.

Late 1975 FT101E Mark 1 (presentvalue 025-£375). This unit is thesame as late FT101B but is markedon the front panel "FT101E" and isfitted with an early version ofYaesu's speech processor. This ear-ly processor is not particularly suc-cessful or convenient due to the lackof an external level control.

1976 FT101 Mark 2 (present valuef350-£400). In this model, thespeech processor is completelyredesigned and a dual gang poten-tiometer is fitted in the clarifier posi-tion on the front panel labelled"CLARI -LEVEL". The processor ismore convenient and effective thanthat fitted in the FT101E Mark 1.

1977/ 78 FT101E Mark 3 (presentvalue 075-£425). DC/DC convertertransistors reduced in size as perFT101 Mark 1. The power supplyand noise blanker circuits arealtered. This version can be iden-tified by the noise blanker boardwhich is numbered PB19F0 and in-corporates a 2.72 MHz. (No crystal,and board marked PB1292 onearlier units).

HAM RADIO TODAY APRIL 1983 21

SOLID-STATE BREAK THROUGH13 FET's, 3 Integrated Circuit*, 27 6111COn Traistors,38 Silicon Diodes Computer Type 12414.44-4n

P.T.101 FITS / Gat ,...1.1,,Iie.. Ve ,atL..a .7,5,, :, 9. etatc.aea. 03

ta LA.. AWNS DOnsDIS.04 Iasi. Itut rr. Ø, to tnEtrt 41

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.ss :vv., F .1 .r060e ',roes'/. CM, be nutoort: Ott a 1 . rt. Or. ,... s.,,,.

4.00441 Wren, Apr 11 a .r...,ormolailecms, a!lnO * rove blanks, is nArnatory---ihe

Fr -IC nibs II, Conwlel*.lt,L.

;Oil Initlihold coresol theNantell p.r,its dirt

040WU* rscl woes only clean signi copy.

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'hi,r1,

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1.61, 0 A0 .1 co. SupP4,. CNNNO, r

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natt,re rut ttottnnal CW Viet and9F0 Is SulttISITtn in ir,!..ust cost

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avat4012 OR tr. 43,,,0t34DSts am: ciannaltnal

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The first publicity blurb

1978 FTIOIZD. This is entirely newdesign which probably was number-ed "101" for marketing purposes. Itis a single superhet and is basicallyan economy version of the FT901from which it was presumablydeveloped. It is an excellent pieceof equipment. It is not the subject ofthis article.

FTIOIEE as FT1OIE but speech processoran optional extra. FTIOIEX economy ver-sion omitting speech processor 12 voltpower supply unit, microphone and fan.160M, WWV, and three 10 metre crystalsalso omitted.

SOLID-STATEFT.-101TRANSCEIVER

The Best Buy?

The basic circuitry and perfor-mance has not changed greatlysince the FT101 Mark 2, and priceand condition are the main con-sideration when purchasing a se-cond hand unit. Some Mark l's havebeen fitted with an official Yaesu up-grade kit (new noise blanker fittedon top of the VFO, new RF board,new mixer/high frequency IFmodule, plus extensive re -wiringand modification of other boards)and are more or less equivalent of aMark 2 if the work has been correct-ly done. A few models can be fittedwith an external speech processorand with a few small mods, a Mark 2or B which is in good condition canbe made to out perform an un-modified FT101E.

SPECIFICATIONS

13141Inutn Input PNort ZOO W PEP SSP i 60 Vt CPC SO W AM

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GENERAL

How The FT101 Works

The FT101 uses a classic doublesuperhet arrangement with a crystalcontrolled high frequency oscilla-tor. This type of circuitry was usedby many rigs of it's era, such as theTS510 and TS520 by Trio/Kenwoodand the FT560 and FT401 by Yaesuto name but a few of dozens. Thesimplified block diagram in Fig. 2shows the FT101 operating 15 metreband, and using this example let usfollow the signal path through thetransmitter.

Speak into the microphone anda few millivolts of audio areamplified by PB 1315 for applicationto the balanced modulator circuitryon board PB1184. The output ofPB 1184 is a set of two sidebandseither side of a suppressed carrier ata frequency just under or just over

V

22 HAM RADIO TODAY APRIL 1983

21 2 21 2 PB1181 RF 5 82MHz Power MHz board MHz

Tx amplifier Tx 2ndmixer

21 2MHz

PB1180 HF IF1st Tx mixerand bandfilter

3 18MHz

A

PB1534RF

processor

3 18MHz

PB1183 LF IFand

crystalfilter

3 18 PB1184 bal 3 18MHz mod and MHz PB1315

and carrieroscillator

audiounit

-C1Mic-

ALC27 02MHz

PB1073xtal

oscillatorboard

27 02MHz

P81181RF board

1st receivemixer

582MHz

9MHz

PB1056VFOunit

(Tunes 8 7-9 2MHz)

9MHz

PB1180 3 182nd receive MHzmixer andband pass

filter

AGC

PB1582noise

blanker

3 18MHz

ALC

PB1184carrier

oscillator

PB1183 LF IFamp ,crystalfilter anddemodulator

AF PB1315audiounit

FIG 2 How the F T101 works I PB numbers a e for FT101EMk3 but all FT101's from Mkt-E use same basic set up IUnits shown transmitting and receiving at 21.2 MHz

S meter

Loudspeaker

3.18 MHz dependent on which side -band has been selected. These twosidebands are applied to PB1183where the wanted side band isamplified, the unwanted sidebandbeing suppressed by the crystalfilter.

The 3.18MHz SSB signal thenpasses via PB1534, the RF pro-cessor, to the mixer unit PB 1180where it is mixed with the output ofthe VFO to provide a signal at somefrequency between 5.520 and6.020MHz, any mixer products out-side this range being suppressed bythe band pass filter.

This SSB signal (in theillustrated case at 9- 3.18 =5.£32MHz) is applied to the secondtransmit mixer on PB1181 and ismixed with the output of a crystaloscillator whose frequency isselected by the band switch. In this

instance 27.02MHz is selected pro-ducing the difference frequency(27.02-5.82 -= 21.2MHz) at the in-put of the radio frequency poweramplifier. This signal is then raisedto a level of approximately 150 wattsPEP by the driver and poweramplifier valves, and is appliedthrough the aerial changeover relayto the PL259 socket on the rear of therig.

The Receiver ModeThe in -coming signal at

21.2MHz is applied via the aerialchangeover relay to the RF boardPB1181. Here it is amplified andmixed with 27.02MHz coming fromPB 1073 the crystal oscillator board.The output of the RF board is the dif-ference between 21.2 and 27.02.Hence 5.82MHz is applied to the se-cond receiver mixer via the band-

pass filter. the VFO can be tunedfrom 8.7 to 9.2 MHz to convert anysignal in the range of 5.520 to6.020MHz to the second IF frequen-cy of 3.18MHz. In this case it is tun-ed to 9MHz (9- 5.82 = 3.18) to pro-duce a signal for feeding to thenoise blanker circuit.

PBFIR2 or its equivalent onearlier models is intended to reducethe effect of impulse type in-terference. Yaesu has swopped andchanged with the noise blanker cir-cuitry on the FT101 considerably,but have never really got it to workwell. If used as originally intendedin a mobile location with S9 + 20QRN from one's own engine, it doeshelp, but even the elaborate versionon late FT101E, which uses an extrastage to convert the noise to 450kHzdoes not seem to help much on thetype of noise encountered on the

HAM RADIO TODAY APRIL 1983 23

average domestic environment. Asimilar elaborate arrangement is us-ed in the FT902 which does not seemvery impressive either. Strangelythe FT101XD uses a much simplercircuit arrangement, and the noiseblanker on this works wonders!

PB1183 is the low frequency IFamplifier and this contains thecrystal filter which provides thereceiver's selectivity. Prior to thecrystal filter, most stages in thereceiver have to handle the entireradio spectrum for a few hundredkilohertz either side of the wantedstation. As well as ham stations run-ning watts this will sometimes in-clude broadcasting stations runningmega -watts so that handling theseextremes of signals without somecross modulation is an almost im-possible task for the RF mixer andnoise blanker stages. Also contain-ed on PB1183 are the AM andSSB/CW detector stages along withthe automatic gain control rectifier.

AGC is applied to the IF amplifierintegrated circuit on PB 1183 and isalso fed back to the RF stage, whiledetected audio is passed on toPB 1315 for amplification prior to be-ing fed by the loudspeaker.

The Transceiver Principle

From examination of the aboveand the block diagram, it will beseen that many transmit stages areturned round and used in the op-posite direction on receive, allow-ing a very considerable cost saving.One has only to compare thenumber of parts in Yaesu's separatetransmitter the FL 101 with the FT101transmitter/receiver to realise why itcosts almost as much to build atransmitter as it does to build a com-plete transceiver. While separatetransmitters and receivers do havesome operational advantages, costeffectiveness has resulted in thealmost complete domination of the

amateur radio market by thetransceiver.

G3LLL asks us to point out that whilehe is happy to answer brief queries on theFT101 series, correspondence must containa stamped, addressed envelope to obtain areply.

FT101 INFORMATION

G3LLL will be covering servicingand modifications in future FT 101articles. Alignment and fitting 10,18& 24MHz will be covered, togetherwith AGC modifications and otherReceiver and Transmitter im-provements. But what about you?

'Bright ideas" and servicing ex-periences should be shared aroundso let us know what you have donewith your FT 101 - please type (orprint CLEARLY) and send your con-tributions to the editor for possibleinclusion in part 4 of G3LLL's arti-cle. The best contribution willreceive 12 months' subscription toHam Radio Today.

4-.-mgle 01.11. ON .111.

24 HAM RADIO TODAY APRIL 1983

CLUES NETBy Cyril Young G8KHH

Due to production dif-ficulties, we were unableto bring you Club Net inthe March issue. Howeverwe have a bumper bundlefor you in this issue. One

or two diary items will beout of date by the time thiscolumn appears. Pleaseforgive us and we shall tryto ensure that the delaydoesn't happen again.

When submittingmaterial for use in ourClub Net column, pleaseremember that there is atleast a six week delay bet-ween receipt and publica-

tion. It helps us in no smallway to have your newsnotes as early as possible.All the best. Frank G4JST,

Editor Ham Radio Today.

Here we are almost into Spring,but it's far from Spring as I writethis month's Club Net. Then thecommon cry seemed to be digdeep it's sub's time; that was near-ly three months ago, so if youhaven't paid up yet what about itlads? Clubs cost money to runyou know!

One of the clubs reminding itsmembers to pay up is the CentralScotland FM Group. From theirmulti -page newsletter I have pick-ed just one or two items of in-terest. One in particular is theirstrong concern for the loss of theband one and band three televi-sion spectrum. It was hoped thatsome of these would be allocatedto ham radio; unfortunately itseems that it is all going to go tocommercial mobiles.

In his editorial, Cohn DalzielGM8LBC, raises the question thatthere is a strong case for 50 MHzand nobody would be averse to abit of room around LOU MHz; andhow about an exclusive amateurTV allocation! He goes on to sug-gest that Amateur TV in this coun-try needs to lobby the Govern-ment on its behalf and is sug-gested that the RSGB attempts toset up an amateur lobby in Parlia-ment. This is not so difficult asone would assume, Stirling's ownMP holds an amateur call sign. (Iwonder how many MP's this alsoapplies to?)

NORTHERN SHOWThe next interesting point is thatthe 21st Northern AmateurRadio Societies Association areto hold their exhibition, previous-ly known as "Belle Vue", to beheld on Saturday 19th and Sun-day 20th March 1983 at Pontin'sHoliday Village, Ainsdale,Southport. The Exhibition openson -Saturday at 11am to 5pm andSunday from 10am until 4pm. Ad-mission at 60p per day or £1 forthe weekend. Pontin's chalet ac-commodation is offered at pricesfrom £10 to £26 per night. Furtherdetails from Colin, or Pontinstelephone 0704 77165.

Scottish Convention 1983will be held in Glasgow on 29thAugust. The venue will be G ar-donald Technical College. Thesocial event is schedule for theBellahouston Hotel in the even-ing.

The 2 Metre repeater GB30Cis being built to cover the northcoast of Scotland and is sited onWideford Hill, neark Kirkwall onthe Orkney Mainland at 742 ftabove sea level.

The most northerly GB2RS,heard on Sundays at 0930 on S21is read by the first all XYL broad-casting staff, namely GM4KNQand GM4LNN.

The Scottish RepeaterGroup are to apply for a special'one off' for high -power licencingfor three Scottish 2M repeaters,GB3HI, GB33N and GB3SS dueto a special geographical loca-tions. Also the 2M phase 6 ap-plications GB3PA, GB40C(Orkney) and GB3LU (Shetland).

From this mine of informationI find that the City and Guilds In-stitute Radio Amateurs Exam is tobe held three times a year in thefuture i.e. December, 21st March1413 and 16th May 1963. There isa great deal more interesting in-formation in this publication. Un-fortunately space is limited! Forfurther information contact ColinDalziel GM8LBC, 12 DunureDrive, Earnock, Hamilton, ML3.

The next club we call on thismonth is Rolls Royce AmateurRadio Club at Barnoldswick. BillRoberts G4PWC has taken me totask for not knowing the location.However, I have since looked itup and find that I have beenthere! So much for mygeography!! Bill says he has justbecome the Club's PRO. Well-done Bill, let's be having lots ofnews and photo's from you. For-thcoming events are Wednesday2nd February - Lecture byAlbert Leaver G 4ECB - Compu-ting and Wednesday 2nd MarchConstruction Contest Display andJudging.

One piece of news is the addi-

tonal Club Call sign to the G3RRalready held the Club now holdsthe callsign G6RRB (Rolls RoyceBarnoldswick). This is for use byclub members within the existingrules of the Club.

Slow Morse Practice trans-missions are broadcast each Fri-day evening at 8.(X) pm on S33-145.550. Reports are welcomedat the end of the broadcasts fromlicenced Radio Amateurs or fromShort Wave Listeners by QSL.

For further information pleasecontact Bill Roberts G4PWC,who hasn't given his address, butI am sure that letters addressedRolls Royce Amateur Radio Club,Barnoldswick, Colne, Lan-cashire, will be passed on.

PROFESSIONAL RADIOIt appears that the Wakefieldand District Radio SocietyG 3W RS have settled in to theirnew palatial quarters and there isthe additional advantage of asmall room which is used as ashack which will make on the airnights much easier for them.

Forthcoming events - 8thFebruary Visit of Radio AireStudios 22nd February Debate onAmateur Radio - 8th March'Electrical Power Generation -(Films) - 22nd March On-the-Air/Natter Night. The Societymeets on alternate Tuesdays atHolmfield House, Denby DaleRoad, Wakefield. Meetings startat 8.00 pm prompt and newmembers and visitors are alwayswelcome. Further details from theSecretary Rick Sterry G4BLT onWakefield 259.515. I've no doubtyou can grab him on the air!

Back now to Glenrothes andDistrict Amateur Radio ClubGM4GRC in Fife, Scotland, whoseem to have a bit of a problem ontheir hands with Raynet. It seemsthat while everybody is expan-ding Raynet activities throughoutthe country, they are having pro-blems getting amateurs interestedenough to keep the group going.I find this a great pity as no doubt

the useful ness of Raynet in thedistrict has been shown; if not, itshould have been. I cannot whol-ly agree with the defeatist attitudethat CB'rs REACT forminguseful and voluntary network.From my personal experiencewith REACT, Raynet is a con-siderably better trained body andmore suited to the situation. If theCB'rs were to use plain English Imight be prepared to go alongwith it, but imagine trying tp passmessages in CB language. (Cyril,you think that amateurs speakplain English? - Ed) Come onlads, get together and get thatRaynet Group organised.Emergencies have no respect fortime or place. You never knowwhen YOU could be doing apowerful job.

A new award will be in-troduced to radio amateurs by theScottish Tourist Board from 25thNovember. The award is in threeclasses: Bronze - 30 districtsworked. Silver -45 and Gold all56 districts worked. Details andapplications from A.G. Ander-son, GM3BCL, West BalfourHouse, Durris, Banchory AB33BJ. Forthcoming Events -February 16th - Visit BBC MWTransmitter, Falkirk (numberslimited). Meeting on 20thFebruary - to be arranged. Forfurther information contact ClubSecretary Gavin Lucas GM4EJI,Provosts Land, Leslie, Fife,Scotland.

Junk SaleOur next Club is one of severalnew members to the net and isStratford-upon-Avon & DistrictAmateur Radio Club, who meetat the Control Tower, BearleyRadio Station, Bearley, nr. Strat-ford on 2nd and 4th Mondays ofeach month, commencing at 7.30pm. A talk in is available if re-quired, on 145.550 MHz (S22).

their programme for the yearlooks very interesting and is asfollows. February 10th - In-troduction to 10 GHz microwaveequipment and operating by

HAM RADIO TODAY APRIL 1983 25

Glen Ross, GENWR. February28th Junk Sale. 14th March -Review and discussion ofmembers' equipment. March 28thAGM & Cine film of radio in-terest. The News sheet is a littlesparse on information but furtherdetails can be obtained by con-tacting either the Secretary DavidBoocock Ge3VC on Stratford -Upon -Avon 750584 or the Pro-gramme Secretary Ian OpwoodG6CWK s2, St. Mary's Rd,Stratford -Upon -Avon, War-wickshire. Phone S -o -A 699F-13

Another new Club to join thenet is the Huntingdon AmateurRadio Society this is in fact anewly formed club which needsmore members. Well folks, here'san opportunity for anyone in theHuntingdon area to join. The clubmeets every Friday "in term time"at Huntingdon TechnicalCollegefrom 6.33 pm. Membership fee5.5.03. The Secretary is RalphMarchant (RS52609) and theChairman Barry Street (G3MSU).For further information contacteither gentleman by writing c/oP.O. Box No. 1, Huntingdon,Cambs, PE18 7TE and here'swishing the Club every successfrom all at Ham Radio Today.

Keep me informed of Clubactivities, Barry, so we can getyou some publicity around theHuntingdon area.

COMPONENTS FAIRIt seems that big things are hap-pening around the Pontefract &District Amateur Radio Society.A deluge of paperwork has comethrough this month mainlypublicising their Third Com-ponents Fair on 13th March 1983;even more effort has been put intothis year's Fair and it is to be heldat Carleton Grange CommunityCentre, Carleton, Pontefract at11.00 am to 4.30 pm (10.30 am fordisabled). There is a licensed barand refreshments and dealerswilsl be displaying and sellingcomponents, test equipment etc.,with the subtle difference thatthere will be no new Black BoxEquipment except for station ac-cessories and antennas. TheRSGB Book Stand will be thereand there is a talk -in on 2M and 70cm., with ample parking close by.Further information from P.N.Butterfield G4AAQ. Telephone0977 791071. 43, Lynwood Cres-cent, Pontefract. WF8 3QT. WestYorkshire.

Having given their Compo-nent Fair some advertising, wenow return to the club properwhich meets on Thursday even-ings at 8 pm. Morse classes areheld on Monday evening at 8 pm.on the top floor of the CarletonCommunity Centre, Pontefract. Iunderstand the latest addition tothe club shack is a 3 element tri-bander up on the roof of the cen-tre. From the chatty newsletter I

G 4CUO

NEW CLUBYet another new club, not justnew to the Net but a brand NEWclub; The Inverness AmateurRadio Club. Its good to hear ofnew clubs being formed,especially in association withBoys Clubs. Well done Bob, dokeep me informed of the futureactivities and Ham Radio Todaywishes you every success. Theclub meets twice a week on Mon-days and Thursdays at theCameron Boys Club, PlanefieldRoad, Inverness. On Mondaysthey run an RAE course, onThursdays, a general chat even-ing and construction night. Newmembers are needed and alwayswelcome. Contact R.H. BrownGM8VIZ, The Flat, 21 High St,Dingwall, Ross -shire, ScotlandIV15 9RU. For further informa-tion and if you write don't forgetto enclose the SAE for your reply.

SINCLAIR CLUBYet another new club to join theNet is SARITG - SinclairAmateur Radio Users' Group -UK. Paul Newman, G4INP, theClub Secretary, says that he form-ed the Group in September 1981as a result of contact with a similargroup in the States dedicated tosharing expertise, problems, cir-cuits and programmes, using theSinclair micros in ham radio. To

I hope that the members of theYork Amateur Radio Societyhave recovered from their AnnualDinner. Among other things,numerous cups and awards weremade to members of the club fortheir bold efforts during the year.Keith Cass G 3WVO, clubsecretary, tells me that meetingsare held each Friday at 7.33 pmand visitors are most welcome. Hesays 'If you don't enjoy yourself,he will be very surprised', and aswe are adamant that amateurradio is fun and should be en-joyed and if you are in Yorkshire,no doubt you will be enjoying itwith a pint! The club meet at theUnited Services Clubroom, 61Micklegate, York. Keith can becontacted at 4 Hepworth Village,York. Don't forget to let me have alist of forthcoming events, as soonas possible, Keith, so we can letthe visitors and non membersknow what you're up to!

Here's a warm welcome foranother new club to call in on ournet, the Biggin Hill AmateurRadio Club holds its meetings at 8pm in the Biggin Hill MemorialLibrary. Its next meeting, on 15thFebruary, has a lecture TheSecret Listeners by Pat HawkerG 3VA. "This is an excellent pro-gramme". On 22nd March is aJunk Sale.

Keep up the good work, Ianand let me have more details ofthe club so we can encourage

am able to relay the following in-formation 3rd February -A con-struction Evening (whenmembers bring along their finish-ed or unfinished projects. 10thFebruary - On the Air Night.17th February - Quiz Night. 24thFebruary Informal Evening. 3rdMarch HF Antennas. . Talk byErnest Ashby G3HCW. For fur-ther information contactSecretary, Niall WhittinghamG 4ISU, 7 Ridgedale Mount,Pontefract. WF8 1SB.

I have received an interestingand informative letter from A.J.Ryan G6LUD, Secretary ofLeicester Polytechnic AmateurRadio Society call sign G 3SDC,School of Electronic and Elec-trical Engineering. Thank you foryour information and how aboutsome more on the club and its ac-tivities. Anyone requiring furtherinformation should contact A.J.Ryan, Leicester Polytechnic,P.O. Box 143, Leicester LEI 9BHor telephone 0533 551551.

The British Amateur Televi-sion Club, Secretary TrevorBrown G8CJS, sends a letter giv-ing forthcoming goodies. This isyour club, you television addictsand it can only be to your advan-tage to be a member. ContactTrevor Brown at 25 GainsboroDrive, Adel, Leeds LS16 7PF ortelephone 0532 670115. Trevor iscurrently writing a series of ar-ticles for Ham Radio Today.ww.

Ron Ray G3NCL and Shirley Hesketh G4HES of Chiltern ARC. Ron and Shirleyproduced the Ham Radio Today morse course

Yet another and mostwelcome new club to our Net thismonth is the Lincoln Short WaveClub, their call signs being G5FZand G6COL. The club meets on2nd and 4th Wednesdays of eachmonth commencing at 8 pm at theCity Engineers Club, CentralDepot, Waterside South, Lincoln.On the alternate Wednesdayswhen no club meetings are held,RAE classes and slow morse codepractice are held instead. Thiscertainly sounds like a go-aheadclub. Club Secretary Mrs. P.G.Rose G 8VRJ tells me that the clubis over 60 years old. Forthcomingevents are February 9th - Lec-ture on RTTY by G 3VRD. March9th - Lecture on Satellites by

date, it has a wide range of ap-plications using Sinclair productswithin ham radio. CW with ZX81,using the same micro in RTTY,teaching morse, coil design,QRA contesting scoring etc. Allthis and details of the Group andits future activities can be had bysending an SAE to Paul Newman,3 Red House Lane, Leiston, Suf-folk, IP16 4JZ. Enquiries bytelephone, or those without anSAE will NOT be answered.Please keep me informed, Paul, ofthe Group's future activities. Itseems that more and more radioand computer clubs are gettingtogether and a large number ofradio clubs are sprouting Com-puter Sections.

new members. Full details can beobtained from Ian MitchellG4NSD, 37b, The Grove, BigginHill, Westerham, Kent. TN163TA.

The next club, The ConwyValley Amateur Radio Club isreally making the magazine staffblush with congratulations on ourfirst edition etc, etc. It's nice tohave all these compliments butI'm afraid it won't get you a GWedition in Welsh, chaps! But thisis the sort of flattery you might ex-pect from the oldest establishedamateur radio club in NorthWales. The club meets on the se-cond Thursday of each month atThe Green Lawns Hotel, BayView Rd, Colwyn Bay, at 7.33

26 HAM RADIO TODAY APRIL 1983

pm where all are welcome. Theclub has a varied programme, DrDavid Last of the University ofBangor is to address the Marchmeeting. For further informationon the club, contact the SecretaryJ.N. Wright GW4KGI 46, TheDale, Woodlands, Abergele LL227DS. Phone! 823674.

Chichester and DistrictAmateur Radio Club meet in theGreen Room, Fernleigh Centre,40, North St, Chichester, on thefirst Tuesday and Third Thursdayof the month at 7.30 pm. There isa club net on (S11) everyWednesday at 19(X) local time.The theme of the next meeting ofthe club on the 17th February isBuilding a QRP CW Tran-

(Let's have more of it - Ed) Forfurther information contact JeffHarris G3LWM, The Oaks,Cricketfield Lane, Bishops Stort-ford, Herts. CM23 2SR. Phone:0279 56347.

Now we come to the IpswichGroup of Radio Clubs whichjointly produce the Clubmagazine QUA whose call sign isG4IRC. The Club Secretary isJack Toothill, G4IFF, 76 FircroftRd, Ipswich, Suffolk IP1 6PX.Telephone (0473) 44047. Clubmeetings are held on the secondand last Wednesdays of eachmonth at 8 pm in the club roomsof the Rose & Crown, 77 NorwichRoad, Ipswich.

This is another one of the

Chiltern ARC month meetingsreceiver and on 1st March,General Club Meeting and 17thMarch, Wartime Radar by LesCarden G8HY. (This is a meetingI would like to attend beingmyself an ex-GCA man).

Thank you Chris for the plugin your magazine review - ob-viously a man with good taste inliterature!

Further information from theSecretary T.M. Allen G4ETU, 2Hillside, West Stoke, Chichester,Sussex. P018 9BL. Phone: WestAshling 463.

KEEP 10M ALIVEIf you are a disillusioned CBerwondering what to do with hisredundant CB equipment, takeheart. There's a club designedjust for you. Mind you it'll meantaking your RAE 'A' licence butthat's another story. The club inquestion is another one new to thenet, called 10 -UK, which isdevoted to consistent use of 10metres having nearly 203 paid upmembers and hope the member-ship will increase in the comingyear. This seems to be a cheapand simple band to get on.Antennas are not of ext remedimensions and there is a lot ofcheap CB equipment which canbe converted. On 10 metres FM,the use of home built or modifiedequipment is the 'in thing' in factits like the good old days, withpeople doing technical things!!

massive, excellent publicationsthat some clubs seem able to pro-duce. From the wealth of itemscovered in the magazine, I mustsay congratulations to Tony WardG 3WXZ and the 13 memberRaynet crew who worked for overseven hours during a largechemical fire on the IpswichDocks. The Fire Service called onthe Salvation Army EmergencyGroup to supply refreslynentsand drinks for the 150 Firemen inattendance. Raynet provided, atthe Salvation Army's request, acommunications link between theincident and the Salvation Army'skitchen at Stowmarket 12 milesaway. Raynet also provided il-lumination for the canteen areawith one of their portablegenerators.

Another item from themagazine which I found extreme-ly interesting was an up-to-datelist of coastal radio stations withtheir frequencies and operatingtimes. I for one find listening tothese stations at any time absorb-ing, especially so during badweather or when there's anemergency in operation. Anotheruseful item in the magazine is theradio amateurs' diary. To il-lustrate, here is a couple of itemsfrom this month's diary; on 5thand 6th march is the RSGB Ex-hibition at the National Exhibi-tions Centre in Birmingham, notat the Alexandra Palace. The

other item is that British summertime starts on 20th March.

SAVE A REPEATERFrom the club's list of forth-coming meetings on 9th Februaryvideo tapes of local amateurs inaction - the mind boggles! 23rdFebruary, South AngliaRepeater Group has an openmeeting for all those interested inGB3PO, and on 9th March, aconstructional contest, 30thMarch - Spring Sale ofmembers' surplus equipment.

Other clubs contributingtowards the magazine include theColchester Radio Amateurs whomeet at the Colchester Institute,Sheepen Rd, Colchester, at 7.30

pm. On 10th February they areholding a Construction ofAmateur Radio Equipment 24thFebruary - Club Motor Racing- Gerry Hinde, G4LSP. 10thMarch - Car Interference Sup-pression - D. Boley G4AZR.24th March, Maps and MapReading - Peter LabalestierG 6HIR

Visitors are always welcome.For further information contactthe club Secretary G 3FIJ, 29Kingswood Rd, Colchester. Tel(0206) 70189.

Martlesham Radio Societymeet on first Wednesday in themonth at 1930 hours in the Lec-ture Theatre. Contact G3NYK orGSENU for further information.February 2nd meeting - WhyGaAs? by John Regnault, G8F-00.

Norfolk Amateur Radio Clubmeet at the Crome CommunityCentre, Telegraph Lane East.Details from Paul GuntherG8XBT. Norwich 610247.

Felixtowe Amateur RadioClub meets at Felixtowe FerryGolf Club at 8pm. The Secretaryis J.E. Hubbin G3XIX, 61aCobbold Rd, Felixtowe. Tel:75676.

Stowmarket DistrictAmateur Radio Society meets atthe Red Cross Hall, StowmarketRailway Station on the first Mon-day of the month at 7.30 pm. TheSecretary: J.C. Lowe GESCB, 22

Bluebell Grove, NeedhamMarket. Phone: Needham Market721296. Their next meetings are- February 7th, Junk Sale andMarch 7th - AGM.

Lowestoft & DistrictAmateur Radio Club holds itsmeetings at 7.33 pm at the NorthSuffolk Teachers' CentreLovewell Rd. No informationgiven on which day the meetingsare held. Further details can beobtained from Paul GodfreyG8JBD. Tel: Lowestoft 60420.

Bury St. Edmunds AmateurRadio Society meets at 7.30 pmon the third Tuesday of eachmonth at the Guildhall, GuildhallSt, Bury St. Edmunds. Furtherinformation from John MunroG3GBB, 29 Angel Hill, Bury St.Edmunds.

Haverhill and DistrictAmateur Radio Club meet atCopse Hall Farm, Steeple, Bump -stead Rd, Haverhill. Furtherinformation from Dave HickfordG6BPS, Haverhill 61207.

Chelmsford Amateur RadioSociety meets on the first Tues-day of each month at 1930 hoursat the Marconi College, ArbourLane, Springfield, Chelmsford.Details from G4KQE, alsopresumed to be QTHR!

Braintree and DistrictAmateur Radio Society meets at7.30 pm at Braintree CommunityCentre, Victoria Road. Visitorsare welcome and a bar isavailable at club prices. (Soundsvery interesting!) Club net is onS15 8.45 pm Mondays wren thereare no club meetings. Furtherinformation from the SecretaryMick Jones G6DFZ, 26 AnsonWay, Braintree. Tel: 44168.

That takes care of all the clubsparticipating in the Ipswich RadioClub Magazine QUA.

From the attractive Decembernewsletter received from theEchelford Amateur RadioSociety the members obviouslyhad a good Christmas. Not con-tent with sprigs of hollyembellishing the newsletter'sfront page - which was packedwith a good mixture of radio items- they just had to include aChristmas menu page by AngelaG4CKO. She at least had a goodChristmas if she practiced whatshe preached!

Unfortunately the programmelisted did not run into 1983, butfull particulars are available fromthe Secretary Anton MatthewsG3VFB, 13a King St.,Twickenham, or phone01-892-2229. The club meetsevery second Monday and the lastThursday of the month at 7.3) pmat The Hall, St. Martin's Court,Kingston Crescent, Ashford,Middlesex. Club nets are on Sun-days at 1003 local on 1.93 MHz ±QRM and on 2 metre at 2000 to210X) local on 144.575 MHz FMevery Wednesday.

HAM RADIO TODAY APRIL 1983 27

FORTHCOMINGRALLYJune 12th - RNARS Mobile Rallyat HMS Mercury from 1000 to1730 hours. A family outing withentertainment for all ages, plusTrade stands and hot and coldrefreshments, also a Grand Rafflewith instant prizes - all undercover.

More details from WallyG4DIU, 103 Torrington Road,North End, Portsmouth PO2 QTN.

And yet another club deter-mined to make our staff blushagain! The Radio AmateursTechnical Engineering Club(RATEC).

Founded in June 1961, theclub shot to fame to the pointwhere attending membership hadto be limited to 100 (how manyclubs can carry a boast like that),with an overall membership ofsome 500 world wide.

It appears that the club's aimsare to turn back the clock to thegood old days of home brew. Thegroup publish an excellent bi-monthly magazine RATEC NEWSwhich only lacks one thing, theClub's name in full, acronyms arefine if you know what they mean!(I confirm that the mag is ex-cellent. How about letting mejoin, please - Ed)

Local meetings are held onMonday evenings at 8.00 pm inthe British Legion, Moor Lane,Woodford, Cheshire.

For more information contactthe Secretary Bob Marsh, GETYHor magazine Editor Dave deSouza Kirby G 3VFP at 17Laleham Green, Bramhall,Stockport, SK7 3LJ or phone 061439 2377.

A new Club Secretary toreport in is Chris Young G4CCCof the Reading & DistrictAmateur Radio Club. Chris isanxious to get more publicity forthe Club and to increase itsmembership so just keep thedetails coming Chris and I will domy best to help.

The club meets at 8.00 pm inthe club room of the White HorseEmmer Green, Reading onTuesdays. Their next meeting,march 15th "RF Hazzards and theRadio amateur". March 29th"Radio Interference Departmentof British Telecom" For furtherinformation contact Chris at 18Wincroft Rd, Caversham,Reading, 'phone: Reading471461.

For a Sunday afternoonouting what could be better than avisit to the East London Groupwho meet at Wanstead House (100yds behind WansteadUnderground Station) Ilford,Essex, at 2.45 pm. Their nextmeeting, 20th March when theydiscuss RSGB "Your Society,which direction?". I would thinkthe obvious answer to this is 'any

which way but up'! For up to theminute information contact JulianGreenberg G6DXW. Whodoesn't want to tell you hisaddress or 'phone number. "HI!"

Cunningham & DistrictAmateur Radio Club join the netfor the first time. They meetThursday nighs at 7.30 at 1

Bonnyton Row, Gridle Toll, Ir-vine, also Tuesday nights which isreserved for RAE instruction. Aswe are short of a diary of forth-coming events I suggest you givethe Club a shout; their call sign isGM3USL. For further informationcall Rodger Bryce GM3JOB, 3West Bowhouse Way, GirdleToll, Irvine, 'phone Irvine215728.

I had a most interesting letterfrom Richard Sugden G8I0H ofthe Goole Radio & ElectronicsSociety. Thank you Richard foryour few kind words (flattery willget you anything - on this pageanyway!)

Don't forget, meetings areheld every Tuesday at 7.30 pm inthe new club house in ParadiseStreet. A film night is being heldon 15th March and a talk by anRSGB Rep on 22nd March and ifthe've got the aerials up in timethey will have an 'on the airevening' on 29th. Call RichardSugden G8I0H at 8 Kings Rd,Swinefleet, Goole, NorthHumberside, for further info.

The newly appointed PublicRelations Manager is Keith PopeG6CGZ, you poor devil, who willtell you all about the Bolton &District Amateur Radio Society- G 8W Y, who meet everyWednesday at 8 pm in the Hor-wich Leisure Centre. This 70member strong club devotessome meetings to formal lectures,activity nights, morse code prac-tice, etc., and occasionally windup the HF and VHF transceivers.Further details from Keith Pope,403 Derby St, Bolton, Lancs onBolton 62443.

On the first Tuesday in everymonth at 7.00 pm you can find theTynedale Amateur Radio ClubG4IZW in 'the room at the end ofthe bar' at the Falcon Hotel,Prudhoe -on -Tyne, Co. Durham.What they do in there is anyone'sguess as they don't include a listof forthcoming events, but KenHatton, 8, Alnwick St, Newburn,Newcastle, 'phone (0632) 678828will be only too pleased to help.

Thank you Mike for intro-ducing the Atherstone AmateurRadio Club to the net, their ac-tive call signs are G4LCQ andG6ARC. Meetings are held onsecond and third Thursdays ofeach month at 7.3) in the TudorCentre Coleshill Rd, Atherstone.For information on club activitiesjoin the club net any Sunday at10.30 on S17 or Mike WoodingG6IQM, 16 Hilltop New Arley,Nr. Coventry.

Now finally settled into theirnew abode, the Fylde AmateurRadio Society, hold theirmeetings on the second andfourth Tuesday of each month at2000 hours at the Queens Hotel,Central Beach, Lytham.

Their next meeting on March8th is on 'Aircraft Instrumenta-tion' by G4AHZ and on 22nd theyare holding an 'InformalEvening'. Harold Fenton G8GGthe PrograMme Secretary will bepleased to see any new members.

The action packed Newsletterfrom the World Association ofChristian Radio Amateurs &Listeners made interestingreading, but unfortunately due tospace limitations I cannot includeall Len Colley G 3AG X packs intoit. He is already planning theAssociation's 1983 Conferencewhich he hopes will be even bet-ter than last year's. I hope yourrig is back on the air now Len;keep up the good work! Detailsand information of the Club canbe obtained from Len at Micasa,13 Ferry Rd, Wawne, Nr. Hull.

(AND BY THE WAY CHAPS,WHEN WRITING FOR INFOR-MATION TO CLUBS, DON'TFORGET THE S.A.E. IF YOUWANT A REPLY. POSTAGECOSTS MONEY!!!)

From the 'Carpet Country'comes an interesting letter fromPeter Peach G3GOS, the newSecretary of the Axe ValeAmateur Radio Club, who meeton the first Friday of every monthat 7.30 pm at the Cavalier Inn atAxminster, where all arewelcome. Peter tells me the clubmembers have done trojan workon the 70 cm repeater atStockland Hill and also run alocal RAE course. Keep the newscoming Peter and good luck withthe 'many changes'. Newmembers and visitors can contactPeter on (0297) 34259.

I am pleased to hear the Rhyl& District Amateur Radio Clubis 'alive well and flourishing', theymeet at the 1st Rhyl Scout Head-quarters, Tynewydd Rd, Rhyl, onthe second and fourth Thursdayof each month. The second Thurs-day is usually an informalmeeting. Forthcoming events in-clude an 'Activity Night' onMarch 10th and on 24th March isan RSGB Film Night'. Furtherinformation contact BryanGWEIOYT on Rhyl 37284 or PaulGW4NLD on Rhyl 31227.

Of course the winter editionof RNARS newsletter is choc-a-bloc with goodies fromthroughout the world. To mentionjust a couple 'If in doubt, short itout!' is the title of an article byG4DEP who writes of his experi-ments with a long wire antennashorted to deck at each end!!!Naturally a number of the club's

members were involved in thecontretemps in the South Atlanticlast year and a resume of the ac-tion from the communicationspoint of view is given by Com-mander Ian Anderson-MochrieG 3VCM.

There is a gentle reminderfrom the Club of the RSGHBExhibition in Birmingham on the5th -6th March, also HMS BelfastActivity Week from 2nd -9thApril. Contact CRS M PuttickG 3LIK on Waterlooville 55880 -weekends only - for furtherinformation.

SPECIAL EVENTSTATIONTo celebrate the 500th anniver-sary of the granting of the RoyalCharter to the City of Gloucester,Gloucester Amateur RadioSociety will be operating specialevent station GB2ROG (Richardof Gloucester) on the second andthird of September 1983. To fur-ther mark the Charter of Incor-poration, which was granted byRichard III, the Society isorganising an award for contactswith any "GARS" stations.

Stations claiming points forQSOs held with GARS stationsbetween 1st January 1983 and 31stDecember 14513, will be awardedpoints as follows: GB2ROG - 15points. G4AYM = 10 points. Allother GARS members = 5 points.15 points are required for theaward working all bands up to432 MHz in any mode. Eachstation may only be worked once.

GENERALCBer's in various stages of disen-chantment with 27 MHz arefinding a lot of interest in HamRadio Today. To those who havewritten regarding graduatingfrom CB to Ham Radio, I wouldsimply say if the Amateur RadioBug has bitten you, join yourlocal Amateur Radio Club. Theywill help you over the RAEhurdles. It's nowhere near as hardas it sounds!

Raynet has been featured inthe Club news several times thismonth, so one more mentionwon't hurt. I propose compiling adirectory of Raynet Groups andmake a request to all group Con-trollers - Please let me have thefollowing details of your group assoon as possible - Controller'sname, address, telephonenumber and call sign. Group'sname, number and zone.

Thank you to all contributingSecretaries. Please do keep us in-formed of your forthcomingevents and as many letters as youlike to send us. Don't forget thechallenge for photographs ofyour Club events. We want tomake the pages lively. 73's 'tilnext month from Cyril YoungG 8KHH.

28 HAM RADIO TODAY APRIL 1983

Asir."lelinearIt is a fact that most amateurs take to the air ontwo metres with a low power black box of somedescription. Take up the soldering iron and addinterest to the hobby with this simple but effec-

tive power amplifier. By Mel Evans GM6JAG

The complete module mounted in an aluminium diecast box.

The author, after some twenty yearsof Short Wave Listening and a briefflirtation with 11 metres, finallydecided to take the plunge and theRadio Amateurs Examination. As aprelude to taking the exam it was feltthat a spell of listening on 2 metresmight be to advantage, and, ratherthan buy a receiver only to sell itagain, hopefully within a short time,an ICOM 215 transceiver was pur-chased. Well, the exam results weresuccessful and the Icom started toearn it's keep. Since the writeroperates mobile to a large extent, itsoon became obvious that a fewmore watts would be useful and sothe design to follow was evolved.

In fact there is nothing par-ticularly novel or "state of the art"about the circuit, and no claims togreat orginally are made, rather it ishoped that the article might serve tointroduce some G6+ 3's to RF con-struction and at the same time offera comfortable saving over the pur-chase of a comparable commercialunit. By careful shopping aroundthis is one area of amateur equip-ment that can definitely be builtmore cheaply than bought! As anadded "bonus" the Beginner's linearis to some extent also a universallinear in that the circuit has beensuccessfully built using five dif-ferent devices, with differing out-puts of course, and this may helpfurther in reducing costs as suitabletransistors may be to hand oravailable from club sales or othersources. See Table (a) for details of

HAM RADIO TODAY APRIL 1983 29

Table (a)

List of alternative devices used and outputs

Type No. Input from Outputtxcvr

Remarks

BLY 88 2W 13W

BLY 88c 2W 16W Higherpowerversion

TP 2320 3W 18W

2N6083 3W 23W Best Buy?

CV type 3W 10W was in boxthat cost40p! at junksale

Please note above are typical outputs atnormal drive levels only, it wouldundoubtedly be possible to produce morethan this from these devices if overdriven.

the different devices used andtypical output powers.

Fig. 1 shows the circuit biasedfor linear operation. If you are con-fident that you will never use theunit on SSB, then it can be built lessthe biasing and SSB switch com-ponents, and this is discussed in thetext as necessary. For use in linearapplications there are no surprises,as already stated, and a sim-ple form of biasing is used featuringa diode in physical and thus thermalcontact with the transistor. Anyheating in the transistor alters thecharacteristics of diode which inturn alters the biasing. Heatsinkingis provided by a standard heatinkand contributed to by the use of adie-cast box which of course alsoperforms an RF shielding function.The input and output of the unit arematched to 50 ohms, and the RF'VOX" sensor detects and rectifiesthe incoming RF resulting in theBFY51 switching "on" the TX/RXrelay coils as necessary. For use onsideband a suitable "hang" is pro-vided by a 100MFD electroytic toprevent the relays chattering in andout. The unit is straight through withno power applied and, withreasonable care in construction, hasa negligible insertion loss.

A word about choice of com-ponents. Purists might quite rightlysit down and with the aid of Ohm's

Law correctly calculate that the wat-tage of RI could be reduced toaround the 21/2 to 3w mark and stillbe satisfactory. At the 3w level R1tends to run a bit warm, and this iswhy the writer prefers to use"overkill", upping the rating to amore comfortable 9w. The relays us-ed in switching were available local-ly and were originally used in the

Pye Bantam for antenna and powerchangeover. At just under £1.00each, they offer a good compromisebetween power and performance atthe power levels and frequency in-volved. A suitable alternative ifthese cannot be found is the OM'from Ambit International.

In construction generally thewriter prefers to adhere as far as ispossible to the KISS philosophy(keep it simple, stupid!), and addshis own as BIB - build in bits.Modular construction enables thehome constructor to test each sec-tion out before final assembly.Should a part of the circuit gowrong, then that particular boardcan be completely rebuilt fromscratch at minimal cost if no othermethod of fault-finding or de-gliching proves successful.

Making the PA boardThe PA board is made up using

PADS of double -sided PCB materialstuck to the base with superglue,and the dimensions and layout of theislands so formed are given in Fig 2a & b together with drilling detailsfor the PCB and the transistor moun-ting. Note that the physical size ofRI will determine the final positionof the strip carrying C5,C6,C7,D1and L3.

If the PA is to be for FM use on-ly, ie class C, then the strip with theassociated bias componentsR1,C5,C6,C7 and DI can be

Bias components

I- R1

csr c6717717,TAAA'

T"2 3

T i7`

From ao_.,:e..0°Tx cyr C2_,e L1

600RLA1

FIG

X/C1

1

Alternative L3 positionclass *C. t.m. only use.

II

L2

C11

C10

+Vcc via switch

L6

R2 C11

L5 fr/77

To0L0700 C8 ant

RLA2

otesArea within dotted lines -bias components.Miss out if p.a. to be used 2m t.m. only but note L3 still used in alternative position

Alternative poles RLA1 and RLA2 joined by a coaxial linknot shown on diagram in interests of clarity

(The 63wpo 2m pre -amp will fit in here nicely)(Between the relays and still in the die cast box(

4. 2m linear amplifier p a. circuit.

30 HAM RADIO TODAY APRIL 1983

FIG. 2a. Drilling details and sizes of p c.b

12mm x 5mm (2off A,B)

17mm x 12mm IC)

12mm x 10mml2of1 G.H)

FIG 2b. Sizes and shapes off pads

Fromtransceiver

File corners to clear pillarsin die cast box

1

30mm x 5mm1

17mm x 5mm lE) Bmm x 5mm IF I

5mm .T.shape 12 off J, Kl

FIG. 2c. Positions of pads -tit alphabetical order -from top

discarded completely and L3 con-nected directly to the foil ground.Of the other strips and pads, notethat strips A and B are in fact also'coils', being part of the inductancerequirements of the circuit andshould be as accurately cut as possi-ble. It is perhaps best to cut themoversize and then to file them to thecorrect size with them held inthevice. The transistor determines theplacing of these strips A and B, asthey should just butt onto the tran-sistor as in Fig. 3. Offer up the stripsto the transistor, which has beenplaced in position but not fo coursesoldered, mark the position in pen-cil, remove the transistor and thenand only then, commit the strips

+ ve

Toantenna

-ve

with superglue. From there it will befound best to fix the pads inalphabetical order as per Fig 2c.Those readers experienced in pro-ducing PCB by etching will have nodifficulty in adapting the abovedetails to their requirements.PLEASE OBSERVE RECOMMEN-DATIONS regarding use ofSUPERGLUE,especially if there areyoung children in the household.

The other two coils should bewound over suitable drill shanksand the leads on these and the fer-rite beaded coils kept to a maximumlength of 5mm. All other componentleads should be kept as short aspossible. The power transistorshould be fitted last. Note that any

Strip BStrip A butted to

shoulder of 0101

Air Am.

OrrATAIAFA IWOV0

Die cast box

Illustration of mounting method of 01and strips A arid B.

FIG. 3a 01 fitting

'1;=V D1

01

""N,Heatsink

Fit D1 using full length of leadsthen bend down into contact with top of 01.

FIG. 3b. Details of 01/D1 fitting.

device containing Beryllium Oxideshould be treated with care and inthe case of breakage, follow the sup-pliers or manufacturers instructionsfor returnand additionally make sureyou wash your hands thoroughly.First fit the heatsink to the die-castbox using countersunk bolts FROMTHE INSIDE so as to allow the PCBto sit flat on the base of the box overthe whole of it's area. Place thePCB in position, offer up the tran-sistor into its mounting position andtighten the nut finger tight only.Check and trim if necessary thebase and collector leads to approx-imately 6mm from the shoulder ofthe transistor. The writer likes tocontinue the manufacturers' iden-tification by cutting the collectorstrip at around 45°. Bolt the PCBthrough the heatsink and place thetransistor in its final position withthe nut finger tight again. Tightenthe nut one half turn further onlyand then solder. Note that in theevent of the PCB needing workedupon the reverse procedure shouldbe followed. A smear of thermalcompound, not too thick is advan-tageous in helping the heatsink per-form well.

One of the side benefits of theisland pad method of homebrew forthe newcomer or beginner is that thecircuit diagram and the circuit morenearly corresponds and is not in -

HAM RADIO TODAY APRIL 1983 31

Components List, RF 'vox'R 20 100RR21 47K pre-setR22,23 330R

C20 4.7pFC21 470pFC22 1000mFd 16V electrolyticC23 2nF

D20,21 1N4148D22 1N4002

Q20 BFY 51

2 off LED (colours to preference)

Misc: Fuse Sr holder, panel mount2 off spst on/off switchesDie cast box approx 200x110x6Omm

Relays are listed in PA sectionS0239 or other RF sockets nuts etc.

Heatsink Type 4M 229 approx 101x94x14(available from Ambit Int.)

Components List, PA board.R1 120R 9wR2 1OR 1/4w

C1,2,8,9 100pF Trimmers (foil compressionplastics types)C3,4 68pFC5 470uF 16V electrolyticC6 4n7C7, 11 150nC10 150pF

DI IN540I

L3,6 4 turns through an FX1115 ferrite bead.25swgL5 6 turns on 6mm dia, close wound. 22cwg

or L7 3.5 turns on 6mm dia close wound. l8swgL2,4 Inductances formed in double sidedPCB see Fig 2

RLA1,2 Pye type 7705 (available from"Brown's Wireless Store, 44 George IVBridge, Edinburgh 1) double polechangeover 12V approx 400R

L 1 2.5 turns wound on 6mm dia drill and thenstretched out to approx 8mm long. 18swg

2 off FX1115 beads.

Tr 1 2N6083 see also Table *

volved in mirror images. Thisenables checking of the circuit to bemore easily completed and this isthe next stage before test and tune.Double check your circuit againstboth Fig 2 and Fig 2 before movingon. Note that the most dangerousperiod in the life of an RF powertransistor in during tune-up. Do tryto follow the directions for test andtune and do not key the mike forlong periods until you are sure theunit is on tune and ready to go. In-itially the transistor should not berun for more than a few secondswithout a check on temperature. Trythe fingertip!

Connect the unit via co -ax andthe preferred sockets to an FM bc-cvr, power supply, power meter anddummy load. If no power meter isavailable, then one of the small in-expensive SWR meters as used onCB will suffice as we are tuning formaximum "smoke" or output. SetC 1,C2, C8, and C9 to their approx-imate mid points and switch on, butdo not key the mike. Check voltageand current at points * on Fig 1, butnote these are for the 2N6083 devicespecified. Assuming there are nomajor problems, key the mike and

adjust C8 for maximum responsefollowed by C9, Cl and C2 in thatorder. Give the transistor a rest, andthen do it all again at least twice orunitl you are sure no further im-provement can be made.

Now having got a working PAon FM, the problem is to switch it onand off when transmitting andreceiving. For this job we will use

the circuit of Fig 4., a simple RF"vox" type switch. This should bedone on a small etched single sidedPCB and the layout is shown in Fig5. Since this is a fairly un-complicated unit, it can be drawnout by hand using a Dalo or similaretch resist pen, or for a neater job,you can use the dry transfer methodavailable from various sources. The

Coils ofRLA1 RLA2

Lic. For use on t m. only- miss out S20, C22replace R21 with fixed 47k resistor

X-X Coils of RLA1 Z-Z On air LEDY-Y Coils of RLA2 W-W 'On' LED

FIG 4 R.E 'vox'switch

+Vcc

LEDpower on

32 HAM RADIO TODAY APRIL 1983

prepared board is etched and drill-ed and the components soldered inas per the overlay. For the benefit ofother, more experienced construc-tors, this unit works well at variousHF frequencies also. Test the unit byconnecting the LED's and relays topoints X -X, Y -Y, Z -Z and W -Wrespectively, observing the LEDpolarity. Feed in some RF and the"on -air" LED should come on whilstthe "power" LED should indicate assoon as power is available. A singlepole on/off switch adds in the elec-trolytic to provide the delay or hangtime on SSB and this should bechecked whilst the pre-set is ad-justed to suit. The pre-set simply ad-just the rate at which the electrolyticperforms, and has no effect whenthe unit is on FM. Connect the "vox"into the circuit by feeding RF fromthe txcvr into A and the relay con-tacts as per Fig 1. The author usessticky fixers to hold both the relaysand the "vox' board in place, andthe LED's, switches and a Fuseholder are mounted on one end ofthe die cast box.

The writer feels that far toomany homebrew projects are cram-med into enclosures that are patent-ly too small, and this -situation ismost probably the result of condi-tioning by our far eastern friends.When working on the shack benchwe do not have the factory assemblyfacilties enjoyed by the black boxbuilders, and it is for this reason thatthe diecast box specified is largerthan might be strictly required, butit does allow the weilding of a hotsoldering iron without a magnifyingglass and without the destruction ofthe insulation of nearby wiring.co -axial connections from the relaysto the board, and form and to eachother, as short and symmetrical aspossible.

On air

Finally, on -air reports for theunit on both FM and SSB are verygood, and althoUgh the unit shouldbe re -peaked for SSB use, in prac-tice using the 2N6083 device, nonoticeable difference can be ascer-tained from on -air reports. I hopefor those of you who have never con-structed anything, this article maybe the spark, I find that a lot of hob-by is construction, especially whenthe junk box can provide a lot of theparts. Perhaps I will hear you on theair soon, I certainly hope so.

-11-C22

Vcc0 x. X

Y. YLED

R23 .14.R22 D22

To.on cu,1rLED

C220-ye

020

b21

C210D20

R21R20

A0

:r.1-C20

f m. /s.s.b. switch

FIG. 5b. Component layout (from top).

X -XY -Y

FIG. 5a PC B etch pattern (from toil side)

w-w

Interior view of the linear amplifier. Although the quality of thepicture leaves something to be desired (our apologies!) the author'ssimple 'pad' construction technique can be seen. The PCB conduc-tors are cut out separately and stuck to a groundplane copper PCBusing superglue. Not only does this allow easy modification of thecircuit without scrapping the basic layout, it also offers a veryrapid building up of the circuit.

HAM RADIO TODAY APRIL 1983 33

24 BUCKLAND ROAD

LEICESTERMon.-Frl. 9-5.30

Sat. 9-12.15

461

TEL 0533 781731

TELEX 341928 HAM

TS930. Superb high performance, all solidstate HF transceiver, capable of operating in theSSB, CW, FSK and AM modes, on all amateurbands (160 to 10 metres). Incorporating a generalcoverage receiver. Built-in ATV is an optional extra.

TS430. The latest 'state of the art' HF transceiverfrom Trio-Kenwood. This new set has full amateur bandcoverage, including the three new bands and also incor-porates a general coverage receiver. SSB, CW, AM andalso FM modes are available (FM with optional board).Fitted with twin VFOs and all the usual filters you havecome to expect from Trio-Kenwood transceivers.

FT102. Represents significant strides in theadvancement of amateur transmitter signal quality,previously restricted to top of the line transmitters. Forthe amateur who wants a truly professional quality signalthe answer is the Yaesu FT 102.

FT707. A full -feature transceiver, idea ily suited as ahome station or as a travelling companion. The FT 707 isthe radio of the 80s. Now with the new bands givingcoverage of 80 to 10 metres in SSB, CW and modes.

FT77. This new full feature mobile transceiver from Yaesu has 100 watts of RF poweron all amateur bands from 3.5 to 30 MHZ (including new bands) and has optional FM. Itsunbelievable small size and lightness coupled with its low price will make this set a firmfavourite as a first-time rig or a handy second set to use anywhere.

HAMINTERNATIONAL are no strangers to the commu-nication business, having been involved on the Continent and in theUK for several years. An enviable reputation has been gained forproducing some of the finest quality communications equipmentavailable. Ham International are now proud to bring you the leadingnames in the field of amateur communications. Yaesu, Trio-Kenwood,FDK, Daiwa and Tonna to name but a few. They are all backed by ourname for service and reliability. Information is only a phone call orSAE away. All items have full warranty and our fully equippedworkshop is on hand should any problems arise. Speedy and reliabledelivery is guaranteed by Securicor.

FDK700EX. This set represents the best valuein 2 mtr transceivers. Full coverage from 144 to 146MHz with large easy -to -read, four -digit LED fre-quency display. Has auto tone burst for repeateroperation. Plus four priority channels.

£165.95

FDK 750a. Offers VHF operation on FM, SSB,CW. Excellent value for the new operator lookingfor SSB facility on VHF. Also fitted with dual VFO.The set has the facility to use the optional 'Ex-£269.95pander 430' giving full coverage on the 70cmsband.

FT 290. The everpopular portable from Yaesu.Multimode operation on 144to 148 MHz.Also available:FT 790. The same format asabove but for 430 to 440 MHz.

TR 3500. A brand newcompact 7 0 cms FMtransceiver. 10 channelmemory with scanning func-tion plus all band scan.

BARCLAKARO

VISA

TONNA (F9Fr)144 MHz9 Element fixed £15.459 Element portable £17.459 Element crossed £28.5513 Element portable £27.2516 Element fixed £34.9517 Element fixed £34.95

430 MHz19 Element £18.2519 Element crossed £31.0021 Element £26.0021 Element ATV £26.00

1441430 MHz9 + 19 Element £30.00

AVAILABLE SOON

YAESU FT 980 All new HF transceiver with option for hook-up to per-sonal computer.

YAESU FT 726R New multiband set with optional 50, 144, 430 MHzfunction on FM, SSB, CW.

Access

Securicor delivery £5.00. - All items over £250 delivered free of charge. We reserve the right to alter oramend prices and specifications without prior notice.

A SimpleAmateurTelevisionStation

MONITOR VTR TV Tx

SYNC ANDPATTERN GEN

75 OHMIHAM RADIO FEB)TERMVIDEO LOOP 0

M MB

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MIXED SYNC

X

CHARACTER GENIHAM RADIO MARCH)

Y

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0 75 OHMTERM

BNC

BNC

N.B. X and 'I are logic signalnot video or pulses and as suchshould be kept shorter than 12"and NOT terminated

64uS

LESS THAN 33uSTHEREFORE SECONDMONOSTABLE IS TRIGGERED

FIELD BLANKING 25H 12.05uS

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1 n UTFIELD BLANKING

LESS THAN 33uSTHEREFORE SECONDMONOSTABLE IS TRIGGERED

LINE PERIOD H

FIELD BLANKING 25H 12 05uS

Part 2This month an

electronic captiongenerator, capable of

displaying 16 letters ornumbers

By Trevor Brown G8CJS

In the February issue I showed youhow to generate the electronic testwaveforms necessary for adjustingan amateur television link. It alsoprovided mixed sync and mixedblanking. This month I would like toshow you how to positively ident thattest signal by electronicallysuperimposing your callsign QRAor QTH across it.

If you think electronic identifica-tion unnecessary when a TV cameraand black board would suffice, Iwould like to point out the following.

The articles in this series havedeliberately been kept simple to en-courage the beginner, who mightnot as yet own a TV camera. Thesearticles have also been designed forsimple power requirements, iepositive supply lines of not morethan 12 volts. This should enable theequipment to work in a portablelocation. Portable working oftenmeans contest work. (Yes evenAmateur TV enthusiasts have con-tests). In a contest, a 4 digit numberis exchanged in vision only and con-tests run 24 hours so night workingtakes place. Need I say that TVcameras don't work too well in thedark, at least not the standard homevideo kind.

The electronic charactergenerator requires to be fed with themixed blanking and mixed sync.This is standard practice in televi-sion in order to keep all the circuitsin synchronisation: they mustgenerate same line number at thesame time. This reduces disturbanc-

36 HAM RADIO TODAY APRIL 1983

EVEN FIELD

FLY BACK

1,0,0,0,0,

1,0,0,0,0,

1,0,0,1,1,

1,0,0,0,1,

0,1,1,1,1,

0,0,0,0,0,

0,0,0,0,0,

COLUMNS

- ROWS

ces when cutting between differentvision sources and also permitsmixes and split screen effects bet-ween two vision sources.

Sync distribution

Television sync pulses can bedistributed around several pieces ofequipment by looping as in Fig 1. Itis essential that the end of the loop isterminated in 75ohms. Televisionequipment is often fitted withswitches labelled bridge and term,ie 75ohm on or off. All equipment inthe loop is switched to bridge exceptthe last item which is switched toterm.

In our system we will not beusing switches and the last item willbe two sockets for feeding otherequipment. If BNC sockets are used,these will be fitted with blankingplugs fitted with a 75ohm resistor.

All leads over 6" long must becoax in a pulse distribution system.Video can also be distributed in thesame way, so one video feed canconnect several pieces of equip-ment, for instance a monitor, 70cmsTX and video tape recorder.

The 75ohm resistor stops reflec-tions which would happen if the endof the loop were left open. Thiswould show up as a ghost in the caseof video loop.

The 2V mixed sync pulses arefed into a window clip circuit which

slices the centre section of thepulses and converts them to TTLlevel. The positive going edges ofthe sync pulses cause one half of adual monostable to trigger for anunstable period given by its timeconstants 47K x 1nF where C x R= 0.7T, ie about 33µS. During theperiod where this monostable isunstable, it allows the second half ofthe dual monostable to be triggeredby a negative transition. This shouldonly happen on the end of a framescan. See Fig. 2. Every 3121/2 linesof a television scan is succeeded bya chain of pulses as per Fig 2 whichare decoded by a TV receiver as acommand to return the spot to thetop of screen and recommencescan. Perhaps you thought televi-sion was 625 lines per picture. Wellit still is, but two scans are requiredto make the complete picture. Thesescans are called fields and two fieldsare required per frame of TV pic-ture. The two fields are interlaced togive 625 lines. The two fields arecalled odd and even fields and areproceeded by slightly different fieldsync waveforms as in Fig 2.

Positioning the characters

At the end of the unstable periodof the second monostable we startthe character generator. The posi-tion of the characters in the framecan be varied by altering the valueof time constants associated withthat monostable. The 47K markedcan be decreased in order to movethe characters up the screen.

This monostable is brought outvia a diode to a terminal that can beconnected to terminal X of lastmonth's generator in order to sup-press the video behind thecharacters with a black horizontalwipe.

Having positioned thecharacters in the TV frame, theymust be generated. Fig 4 shows anexample character which is posi-tioned in a 5 x 9 matrix.

Circuit description

This matrix has two dimensions,5 vertical columns and 9 horizontalrows. The characters are containedwithin the 74S262AN chip in theform of a large addressable matrixof pre-programmed characters, 128in all. The required character isselected by the matrix board whichputs a code on the board edge con-nector pins B, C, D, E, F, G, H.

The top row of the character 'G'is present when B is equal to logic0, C equal to logic 0, D equal tologic 0, and E F G H is equal tologic 1. The top row of the 'G' is pre-sent on the output pins of the74S262AN in the form 0, 1, 1, 1, 0.The 74151 looks at this data in se-quence and during data 1 causes Q5to turn on and clamp the picture topeak white via the port Y on the pat-tern generator. In order for the74151 to scan each column in row 1it requires a binary code suppliedby the column counter which is ad-vanced by the line locked clockoscillator. When the top row of the

FIELD SYNCSEPARATOR

FIELDPULSES

FRAMEDELAY

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RESET

ROW ADDRESSCOUNTER

INHIBIT ROW COUNT

RESET

TO SYNC GENERATORBOARD

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AND

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CHARACTERSOUT

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AND

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74S262AN

HAM RADIO TODAY APRIL 1983 37

D

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74154

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first character has been clocked outit proceeds to the next character byadvancing the matrix address toselect the next character andrepeating the process. When

character 16 row 1 has been scann-ed the process is repeated four timesto make the top bar of the example'G' four TV lines thick.

Now we require the second row

H1

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of the 'G': 1, 0, 0, 0, 0. It requiresthe 74S262AN to present row 2 at itsoutput data lines. Row code addresson pins 4, 5, 6, 7, is incremented.The row address comes fromanother 74LS393 counter which isclocked by line rate pulses derivedfrom mixed blanking via anotherwindow clipper. The QA and QBare not used so the code advancesevery four lines. Row 2 of all 16characters is now clocked outfollowed by row 3 etc. until row 9 iscomplete. When row 9 is completePin 6 of the row clock is coupled intoQ3 emitter where it switches off theclock pulses to the row counter. Q4emitter is also pulled high which inturn switches off the 74151 so no fur-ther data is generated. Fig 5 showsthe block diagram of the charactergenerator and sequence of events.

The first thing that happens isour first monostable detects framesync and triggers our secondmonostable which gives frame delayso as to position our text somewheredown the picture. When this mono -stable has finished its unstable

38 HAM RADIO TODAY APRIL 1982

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HAM RADIO TODAY APRIL 198339

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period the row counter is resetwhich in turn enable the 74151parallel to serial converter.

The column clock has been keptrunning all the time so the columnaddresses of the first character willbe generated. When the column ad-dresses of the first character havebeen generated the diode matrix ad-dress is advanced in order to selectthe next letter and the column ad-dress is repeated until we reach theend of one line. This process isrepeated for four lines until we ad-vance the row code and repeat fourlines for each row code until the endof row 9. The 74151 data converter isswitched off and stops the rowcounter from being advanced.

Fig 6 shows the circuit of thediode matrix which is on a separatecard to enable plug-in pre-programmed matrix boards to beconstructed.

Connectors I, K, L, M carry thecharacter address code. They feed a74154 where they are decoded into16 separate outputs. When an out-put pin of the 74154 goes to logic 0it brings one location of the diodematrix on line there are seven diodepositions possible in any one of the

matrix locations. Fitting a diode willcause a logic 0 when that location isscanned; omitting a diode will causea logic 1 in that location. The possi-ble permutations of seven diodepositions is 128 each one cor-responds to a character in Fig 7.

Programming is simple. Firstlocate the character you require inFig 7. Next transpose its position tothe chart in Fig 8 which shows howto programme it. For our example

13 0.1

C TO 74154

D

we use the position on the farright of the P.C.B. first ie Pin 1 ofthe 74154 for the first letter. Thediode cathodes connect to the busbar on the component side of thePCB while the anodes go throughthe PCB and connect to the B, C, D,E, F, G, H bus which are on theunderside of the PCB.

Fig 9 shows a programmedmatrix which carries the legend'G8CJS - TV LEEDS'.

In order to keep the circuit of thecharacter generator as simple as

possible, the characters start rightat the far left of the screen. Thiscould result in the first character notbeing seen on a badly adjustedtelevision. It is good practice to pro-gramme the first space blank ieO.S.C.

- TO 74154

Construction

The PCB used for the charactergenerator is double sided but unfor-tunately cost prohibited the use ofplated through holes. The symbol *on the layout denotes where the PCBrequires connecting through fromcomponent side to track side. It isalso important to solder componentsat both sides of the board. This in-cludes 'IC's. To this end I have keptthe component side artwork to anabsolute minimum as it does makethe use of sockets for the 'IC's dif-ficult. The 74S262AN should be

40 HAM RADIO TODAY APRIL 1983

socket mounted if possible.Upon completion of the

character generator check all thetracks for solder splashes etc. Con-nect the Y port to the patterngenerator, connect up the mixedsync and mixed blanking and the+ 5 volts and ground connections,but omit any connection to thematrix board. 16 small white blocksshould be visible across the test pat-tern. Connect up X to the X port anda black wipe behind the charactersshould appear.

Now check the matrix input bygrounding B. The 16 white blocksshould change to 0. Moving theground to C should change theblocks to 'w'. Grounding D shouldbring up the sign 'E' and so on.

If all this checks out, build andinstall the matrix card. This board isdesigned to fit above the maincharacter generator PCB and con-nect with either plug and socket orwire.

Both printed circuit boards usedin this project are available fromThe British Amateur TelevisionClub, 13 Church Street,Gainsborough, Lincs. Pleaseenclose an S.A.E. for details.

Next month - how to add akeyboard.

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HAM RADIO TODAY APRIL 1983 41

This is

Norfolk Raynet operator G3PYN(inset) net controller working atemporary station located in arailway building.Exercise Fox a simulated train crashon a Norfolk railway where Raynetworked in conjunction with thecombined emergency services.

Amateur radio is always ready to lend a helpinghand.By Cyril Young G8ICHH

It is said that out of every disastercomes some good. That can mostcertainly be said of the 1953 EastCoast floods; a disaster when threehundred people died with thousandsmore made homeless and the safetyof ships at sea was put in jeopardywhen Humber radio went off the air!

One such ship was the SSLevenwood, a coaster battling withenormous seas, too close to theshore for comfort. She was in con-tact with Humber radio who was giv-ing her captain instructions not toattempt to enter port. Before furtherinformation could be passed, theHumber coastal radio station, itselfhit by the storm, went off the air!

The SS Levenwood radio opera-tor called in vain . . . Humber radiowas unable to reply. Instead the

voice of a radioham crackled in theradio officer's headphones. "SSLevenwood, this is G3AXS, anamateur radio station. How do youread me?" "G3AXS, this is SSLevenwood .". The seed of anidea was sown. Reg Collins G3AXS,risked having his licence revoked,in an attempt to help the ship indistress!

Despite vigorous attempts bythe RSGB, two years earlier, to offerthe Government a complete emer-gency network consisting ofdedicated hams, the proposal wasrefused in the House of Commons bythe Postmaster General on the ad-vice of his office, stating that theywere completely capable of handl-ing any foreseeable disaster and

42 HAM RADIO TODAY APRIL 1983

there was no room for amateurs!This short sighted jealousy by

the Post Office was to be recalledonly two years later when thedisasterous storms hid hundreds ofmiles of the coast, causing havocwith all public services and, in onlya few hours, communications wereat a standstill and were unser-viceable for several days.

So it was just one year later, theRadio Society of Great Britain laun-ched the Radio Amateurs Emergen-cy Network (RAEN), designed, intheory at least, to be a communica-tions back up service for emergencyuse only. It was very soon realisedthat without some pretty drasticchanges being made to the amateurradio licence, RAEN was going tobe a little more than a weekly netwith a controller.

Another immediate problemwas the design and construction ofmobile and portable equipment - itwas obvious that to be of any use inan emergency the Hams had to beright there at the site of the incident,not back home in their shacks.

At its inception, RAEN, as it wasthen known, was to be of littleassistance in an emergency, as thepassing of third party traffic wasvery restricted and it was still tooeasy to exceed licence regulationsin its limited capacity. the RSGBand the Home Office commenced aslow but continuing round ofnegotiations to make the emergencyservice viable. As the service hasgrown, it has repeatedly proved itsability to organise an emergencycommunication service, so theHome Office have added speciallicence dispensation to the RaynetMembers licence for use under liveor exercise conditions. The firstmove by the RSGB was to changethe name to Raynet; the lettersR.A.E.N. being a ship's call sign.

Flexible Communications

The flexibility of the Raynetsystem often makes it more versatilethan many of the user services' owncommunication systems. As an ex-ample, an ambulance has its radiolink firmly mounted in the vehicle,so if the crew have to leave the am-bulance to go a few hundred yardsinto a wood they are out of contactwith their base. Whereas, a Raynetmember would most likely have awalkie-talkie, which could simply be

unhitched from the car for use onfoot. This is just one example wherethe Ham can be more versatile thanthe professional user!

Since it's formation, Raynet hasbeen involved in many real (live)emergencies, from forming a com-munications link with the Hamp-shire police when an overwhelmingnumber of volunteers arrived tohunt for a lost baby in a forest or, forover 70 hours, relays of Raynetmembers passed 999 calls when atelephone exchange was badlydamaged by fire.

Emergencies have no respectfor time, weather or location. A cou-ple of Raynet members were enjoy-ing a quiet summer's afternoon napin their cars by a South Coastbeach, when a light aircraft plung-ed into the sea. Raising the alarmthey had the rescue service there inminutes; then continued to handlemessages for sometime until therescue services were able toestablish their own communicationslinks. The full local Raynet force wasput on Yellow Alert ready to handleany back up required.

The incidents that Raynet hasbeen involved in is endless. Ofcourse not all call outs are as ex-citing; sometimes there have beenhours of waiting with just routinesignal reports - waiting for hightide, to see if a river will break it'sbanks; or one I was involved insometime ago, when the telephoneand fire alarm lines to the exchangewere cut by contractors working inthe grounds of a large remote boar-ding school, built mainly of timber.The Science Master G8PGY calledfor assistance. The local RaynetGroup kept an all night vigil overthe 500 boys, in case of an emergen-cy.

So what does it take to be aRaynet member? If you are, or havebeen a scout or in any of the cadetsor forces; if you can accept ordersand carry them out to the best ofyour ability; if you don't get fed upwaiting for something to happen anddon't panic when it does; if you'reprepared to spend some time eachweek training and go on the occa-sional exercise - then you are thetype they are looking for!

Most groups are organised sothat every member gets the oppor-tunity to experience the conditionsof being controller - relay station- base or mobile outstation. Thereare so many jobs to be done at a live

incident or exercise. If you're notlicenced yet, you can still play animportant part, writing outmessages, keeping log, deliveringfood and drink to outstations -there's a hundred and one jobs to bedone. A great deal of help comesfrom the YLs and XYLs too!

Your Equipment

If you're licenced, the choice ofequipment will probably have beenmade so you will have to make thebest of what you have.

A good Group Controller willhave organised his team such thatthe less agile members and thosewithout motor transport will act asrelay stations, or general monitoringstations or base control station.Mobile stations should have equip-ment permanently, or easily install-ed in their cars. All stations will beexpected to have O.S. maps cover-ing their area and any neighbouringareas you may be called into to help.

Handheld transceivers havebeen a boon and a curse to Raynetmembers; their portability makesthem ideal for use away from the carand in difficult country, but theirshort battery life can be an embar-rassment. Imagine walking half amile across rough terrain in blizzardconditions to get to a strandedgroup; you press the PTT . . . yoursignals are not heard . . . FLAT BAT-TERIES! Therefore, a must is at leastone spare set of batteries and takethem with you! If you use nicads,there are circuits designed toenable you to charge your batteriesfrom the car. All batteries rapidlylose their efficiency in cold weather;keep the spare set in an inside coatpocket!

HAM RADIO TODAY APRIL 1983 43

The User ServicesThe first services to request co-

operation with Raynet were the RedCross Society and the St. John Am-bulance Brigade, both having verylimited radio communications oftheir own. Numerous exerciseshighlighted the versatility of theham possessing mobile and portableequipment with his ability to beright at the incident centre. Despitethe teething troubles the exercisesdid not go unnoticed. Today Raynethas an excellent working relation-ship with both first aid groups, thePolice, Fire brigade, the Coast-guard and the County Incident Of-ficers of most areas of the UK. Ofcourse some areas are betterorganised than others - the bestusually being districts where live in-cidents frequently occur. This istypical of the Englishman.Something has to happen on hisdoorstep before he is pushed intoaction - then completely unpre-pared - so Raynet means training.This is no more than an extention tothe transmitting licence which isissued to promote self teaching andtraining.

Most groups hold messagehandling nets one evening perweek, with a full scale exerciseevery couple of months. The HomeOffice have just granted permissionfor Raynet to exercise with the userservices once a month. This shouldput more realism in to the operationwith the opportunity to meetmembers of the user services.

The evening nets are often ar-ranged such that every membertakes his turn at being Controller;map reading ability is helped by thecontroller giving each member anNGR (National Grid Reference) inturn, after which each station is call-ed in again to give the name of hisNGR spot. Any other ability or train-ing the member may have, such as agood knowledge of First Aid, climb-ing or caving will be of immenseuse. One thing that every Raynetmember must have is an intimateknowledge of his immediate districtand a good working knowledge of alarger surrounding area. This iswhat makes you most useful to theuser service. Well organised groupswill check the radio paths across

A Sea King helicopter 202 Search and Rescue squadron from R.A.F. Coltishall arriving to lift a casuality froma Norfolk beach in exercise 'Search' in which Raynet, Rover Rescue and the local Coastguards took part.

44 HAM RADIO TODAY APRIL 1983

their own and into the neighbouringareas. Suitable relay sites will beknown to all members; these willmost probably be used for mannedtalk through stations.

It must be fully understood thatin no way can Raynet operatewithout the request of one of theuser services or County Incident Of-ficer.

If you should happen to walk in-to an incident you could temporarilybecome controller. Your first stepwould be to raise preferably, aRaynet operator, requesting him tocontact the relevant user service orthe Police to authorise Raynetoperation. Your chances of beinginvolved in a remote incident areslight, but you should be preparedfor such a situation. The Home Of-fice has just granted permission tohams to pass third party messages inthe event of a remote road traffic ac-cident.

Storm and tempest are the ma-jor incidents in which Raynet hasbeen involved. Groups covering thecoast or who have rivers constantlyliable to flooding in their areas arealways alert to weather conditions;especially during Spring tides andhigh winds. The dates of tides andtheir height can be obtained fromlocal tide tables.

When the possibility of floodconditions arise, Raynet groups onthe coasts and especially at theestuaries are put on 'Yellow Alert' acouple of hours before high tide,allowing mobile and portable sta-tions to be set up in strategic posi-tions and radio paths to controlchecked. When one of the user ser-vices request Raynet aid, the systemgoes to 'Red Alert' a couple of hoursbefore high tide, allowing mobileand portable stations to be set up instrategic positions and radio pathsto control checked. When one of theuser services request Raynet aid,the system goes to 'Red Alert' and allstations are involved.

Permanent RaynetStations

In a number of areas whereRaynet has been repeatedlyvaluable to the public services,much consideration has been givento help the local groups by theCounty councils. One such group isthe County of Cornwall RaynetGroup, (in fact there are seven

Local District Health Authority Ambulance Service andpersonnel exercise with Cornish Raynet in Truro.

groups in the area). Cornwall, withits miles of uninhabited moorland,criss crossed with narrow roadsthrough valleys and over hills,makes communication difficult,even when using the repeaters, asmany will know from their holidays.

After several years trojan workby the 150 Raynet members cover-ing the County during heavy snow,appreciation of the service given bythe groups was shown by the CountyCouncil in their joint venture withRaynet in helping to provide perma-nent emergency communication sta-tions at vital points in the County.

At Raynet Headquarters inCounty Hall Truro an emergencycommunications control room hasbeen set up with transmitters andreceivers operating on 70-144 and432MHz, also on HF bands for out ofCounty operating. Tape recordersoperate on both transmit andreceive and have been found to be

invaluable at debriefings. The sta-tion is backed up by a standbygenerator and 12 volt heavy dutybatteries. Another station has beenset up in the Incident Centre ofTruro City Hospital, where a 2 metre25 watt tranceiver feeds a colinearon the roof.

Going mobile

Apart from the regular badweather call outs, the CornishRaynet teams were active during theTorry Canyon incident and morerecently with the Penlee Lifeboatdisaster, so it's not surprising thatthey have twice been awarded theRSGB Raynet Trophy!

Most groups have their gloriesto tell and not always as a directresult of a disaster (in this countryanyway!) A number of RaynetGroups are joining forces with theLand Rover Rescue Teams that are

HAM RADIO TODAY APRIL 1983 45

springing up throughout the coun-try.

Norfolk Raynet, in conjunctionwith the local Rover Rescue Team,organised in three days (and raisedthe money to cover fuel expenses)for six vehicles (including one YL)to make the three thousand milejourney to an Italian earthquakedisaster zone; amid plague, moretremours, impossible weather con-ditions and just to make it more in-teresting Mafia activity!

And so we could go on aroundthe counties . it's obvious from theincidents quoted that the motto ofRaynet members must be 'be pre-pared' . . . and not just radiowise. It'sadvisable to have a container ofsome sort ready packed so you canpick it up and 'go' when called out;knowing you have with you somefood, in the form of chocolate/pea-nuts (or whatever you fancy) in asealed box, plus a couple of cans oflemonade or similar (not beer -apart from affecting your operatingit makes you thirsty); a change ofclothing (particularly socks).There's nothing worse than workingin cold wet feet and when the goinggets really cold an extra jumper anddry gloves will help to keep you atmaximum efficiency while you arehelping the less fortunate. Remem-ber it could be a long time beforeyou are relieved or get any food.Always wear your hard hat and anyother Raynet identification youhave. If you're at the site of an inci-dent mark your car with largeRaynet posters, better still an il-luminated sign and, while you arestationary, a flashing green lamp ispermissible.

How Do I Join Raynet?

Simple, just ask your local ClubSecretary or Raynet Controller;otherwise a note to the RSGB,enclosing a SAE will bring fulldetails and the necessary forms. Youwill require a couple of passport sizephotographs of yourself; one forRaynet records and the other yourID card.

If you're still not sure if youwould enjoy working with a RaynetGroup, and you must enjoy doingthe work (after all it's your hobby),talk to your local Raynet Controllerand join in some of their activitiesfor a few months, no one will com-plain or think any the less of you ifyou drop out after a while; if it

doesn't grab you, you probablywouldn't have become a usefulmember of the group anyway!

Keeping It All Together

It's obvious, where groups arespread over a large area, contactmust be maintained betweenmembers; meetings are usually nomore than monthly. Most Groupshold a weekly net. Nets giveeveryone the opportunity to try theirhand at being controller andteaches the art of message handling,map reading, and the opportunity toreport equipment and personalstatus etc. Recognising a familiarvoice could be of immense use andcomfort in a live civil defenceoperation, something else in whichRaynet will no doubt play a largerole. (It is under consideration bythe Home Office now).

There are several national fre-quencies allocated to Raynet, forlive, exercise and net use: -

144.260 70.355144.775 70.375144.850 433.200 (RB/SU8)145.200 (S8)There is also a controllers' net

every sunday at 08.30 hours on3. 790MHz .

The Home Office have recentlygranted permission for Raynet toparticipate as an exercise, if re-quested by user service in charitywalks, marathons etc and have alsogranted permission for third partyoperation of your equipment i.e. itcould be easier and quicker for adoctor to talk direct to a colleaguethan via a message pad, but you willremain in strict control of the radioequipment and it's at your discretionas to who uses this facility.

Organisation

Naturally it took time toorganise a nationwide network ofthis calibre and there have beenmany changes during the course ofits lifetime. The present arrange-ment is still being adjusted fromtime to time in an attempt to reachthe ultimate structure.

Governed by the RSGB Gener-al Council, the Raynet NationalCommittee, consisting jointly ofRSGB Council Members and amember from each of the twelveRaynet zones, on through zonal con-trollers, county controllers to groupcontrollers and Raynet members.

RSG BGeneral Council

Raynet NationalCommittee

12 Zonal Controllers

County CountyControllers Controllers

I I

Group GroupControllers Controllers/

Group G\ up Grou/p G\upMembers Members Members Members

The structure gives the impres-sion of being heavy in executivecontrol, however, it does work andis much appreciated by the userorganisations.

As already mentioned, emer-gencies have a habit of happeningat inconvenient times. It's a goodidea to explain to your employerwhat Raynet is all about, or showhim this article and ask if he isprepared to release you from yourplace of employment without loss ofpay to attend live emergencies. Pro-of of live incident and your atten-dance will be provided by your con-troller.

Most companies agree to this, asthey do for Territorial TrainingCamps, the excellent publicity theyreceive as a public spirited com-pany is good for their local image.

As a registered Raynet member,attending a live emergency, you areinsured against accident by theRSGB.

If you think you fit the bill,Raynet needs you. A well organisedand trained service is far superior toany untrained volunteer group.

46 HAM RADIO TODAY APRIL 1983

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The input stage of this unit is a digital frequency discriminator having twocentre frequencies of 1360Hz and 1700Hz, switch selectable. This facilityallows reception of all transmissions and standard frequency shifts. The in-clusion of a printer output socket (Centronics compatible) allows hardcopy of received signals.

The inclusion of a wide range of speeds and shifts makes the converterhighly versatile, and compatible with most amateur and commercialtransmissions. The unit is ideally suited for decoding the telemetry data at1200 baud from the UOSAT satellite.

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Please mentionHam Radio

Todaywhen replying

to adverts47Ham Radio Today, April 1983

TechnicalitiesElectronic

countermeasuresagainst Russian over -the -horizon radar -

Successful RF design: abetter CW IF strip. ByFrank Ogden G4IST

Shooting a woodspecker

The theme for this month's column is'successful RF design' but first, let'slook at a most ingenious little box tocome onto the market. No apologiesfor changing the subject just as soonas it is started but this new HFreceiver add-on is very much a caseof successful design.

Anyone who has ever listenedto the upper reaches of the HFbands will have heard the'woodpecker', a megawatt pulseover the horizon radar which theRussians use to detect incomingAmerican (one supposes . . WithPres. Reagan at the helm, anythinggoes) missiles. Unfortunately forEurope, placed as it is halfway bet-ween Russia and the USA, thesemassive pulses of frequency agileRF come to earth on the short skipobliterating everything during theirshort duration. With regular repeti-tion rates of 10's per second theyprobably do more damage toreceiver front ends than the EMPevent which they were designed tofore -stall!

As every amateur knows, thiswretched menace comes up whenthe bands are at their most inter-esting and always when you areabout to answer a CQ put out by aZL3. Some modern HF trans -receivers have incorporated specialtypes of noise blankers whichreduce the anti -social woodpeckerto manageable proportions. Peoplewith older sets will not be so lucky.The American company AEA hascome up with an add-on box con-necting between the aerial andreceiver which should shoot thewoodpecker. Just how well it workswe shall tell you later. We have a

To aerialWoodpeckerpulse train

Broadbandamplifier

Gate

Cleaned signal with holes correspondingto places where the woodpecker pulses'

(.° would be.Qc To receiver

frf Pulse train from VCO/advanced by period equalto delay time of line

Peak

detector

FIG. 1. How to shoot a woodpecker.

Phase

--->--comparatort-

Real timepulse train

Delay

lineVCO

Regenerated pulse train exactlymatching real time pulse train.

unit on loan from the UK importersICS Electronics and we shallpublish the review just as soon as wehave completed it.

It is the way that we think theAEA box works which intrigued us.The Moscow Muffler (which is whatthe company calls it) makes use ofthe fact that the radar transmissionscomprises a very accurately spacedpulse train. The box listens for thewoodpecker by amplifying theaerial signal, broadband and thendetecting it like a wideband TRF set.An internal oscillator is then phaselocked to the incoming pulse train.This accurately re -timed signal -which maintains accuracy even inthe presence of lots of other signals- triggers a gating pulse to turn offthe signal path to the receiver forthe time that the Moscow Mufler ex-pects a woodpecker pulse to be pre-sent.

The clever thing is that thegating pulse is arranged to blank offthe receiver path just a little in ad-vance of the arrival time of thewoodpecker. This would be done bydelaying the VCO signal to thephase comparator so that the VCO isforced to run just a little bit ahead oftime if it is to keep up with thewoodpecker pulse train. Fig. 1 il-lustrates this.

Successful RF design

This is a fairly wide topic to discussin the two or three thousand odd

words allocated to this monthly col-umn. RF design takes in so muchthat, to tackle the topic at all, youmust discuss it in terms of a specificsystem to reduce it to dimensionswhich can be (only just) handled.

Unfortunately my time is toolimited to produce design examplespurely to illustrate this article andothers in the same series. I thereforepropose that I shall kill two birdswith one stone by designing a pieceof gear which shall then be offeredas a constructional project in thismagazine.

We have received cor-respondence to this mag and seenlots of it in others asking - evenbegging - for a low cost, high per-formance HF transreceiver for CWonly. Now I don't particularly likeCW as an operating mode simplybecause I'm not very good at it. Onthe other hand purpose built CWgear is very straightforward, there isa demand for it, and it offers themost easily understood vehicle fordemonstration purposes. The finish-ed transceiver will cover all bands,CW only, produce about SOW of RF,and cost in the region of £100 tobuild. I shall do the basic designand my mate Tony G 3W PO will putthe project onto boards.

A CW transreceiver

Fig. 2 comprises the block diagramof the complete transreceiver. Thereis nothing unusual about the overall

48 HAM RADIO TODAY APRIL 1983

concept. It shows a single conver-sion superhet running with an IF of10.7MHz (because components forthat frequency are cheap) and thesynthesised VFO local oscillatorrunning at 10.7MHz above signalfrequency.

The whole design has beenoriented towards maximising thestrong signal performance in thereceive mode. There are relativelyfew design considerations or con-straints about the TX part . . . youeither transmit a nice pure carrierwave or you don't.

The part of the system which wewill use for this discussion is the IFboard; the full circuit diagram forthis is shown in Fig. 3. Ignoring therole of the double balanced mixerDBM1, the entire strip from IFT1 on-wards processes 10.7MHz signals,10.7MHz being the IF frequency(yes, I know that I have just writtenIntermediate Frequency frequencybut it seems appropriate somehow)of this single superhet trans -receiver.

Wideband signalsThe first thing to note is the role ofIFT1 and IFT2. Signals coming infrom DBM1 will cover a spectrum ofperhaps a MHz or so either side ofthe wanted signal now centred on10.7MHz and the same amount ofsignal again at 2f + 10.7MHz. Acase in point. You are trying tolisten to a weak signal on 7MHz afterdark; it may have a peak strength ofa few microvolts. The preselectorwill also allow through the 41mbroadcast band where I havemeasured signal strengths of nearly

100 millivolts. Exactly the samesignals will also appear in a bandcentred on about 25MHz, the in-verse image signal produced by theDBM. With two high level spectrapresent simultaneously, the poten-tial for intermodulation products isendless. Intermodulation products,it should be remembered, aresignals which are not harmonicallyrelated to anything in particular,and the receiver can 'hear' thismush in an otherwise quiet part ofthe band masking the real low levelsignals which are there. IFT1 andIFT2 cut the potential problem inhalf by rejecting the inverse imagesignal.

Ideally, an attenuator padshould have been included betweenthe double balanced mixer andIFT1. See Fig. 4. Although IFT1and IFT2 will accept the wantedsignal and its spectrum, the inverseimage spectrum, much higher infrequency, will bounce off the filtercombination and head back towardsthe DBM causing intermodulationproblems inside the mixer itself. Un-fortunately an attenuator, while itwould have cured the reflection pro-blem, would have cut the wantedsignal level. This could have beenmade up with an RF amplifier stagebut then that would have introduceda fresh set of problems. This impassehas been tackled in a different way.Instead of making the IF port of themixer resistive - the ideal solutionas in Fig. 4 - the LO buffer ampli-fier, not shown on the schematic,will have a resistive output. A DBMis a bit like a pressure vessel withthree holes in it. If you stop two up,then you must leave the third open

or it will explode. Since it is possibleto generate any amount of LOpower, we can afford to lose somethrough a resistive attenuator as inFig. 5.

RF in IF out

Lo in

IFT1

Unwanted signal productsin this network

without attenuation tomain signal path.

High level Lo drive

FIG.S. The practical solution.

IF pre -amp

IFT1 and IFT2 have cut down highlevel interference to within about200kHz of the wanted signal.However their main job was to dealwith the inverse image spectrum.Q1, the IF pre -amplifier, could stillbe faced with high level inter-ference and therefore must be verylinear in design. The purpose of Q1is to maintain a reasonably lowsignal to noise performance: itboosts the signal to a high enough

Aerial

r

Pre - Ringselector mixer

A L _ _1

Output Power VFO

filters amplifier synthesisedlow noise

'Roofingfilter

IF ..a.1 Delaypre amp line

IFCW amplifier H Notch

filter12 staged'

filter

T

Carrieroscillator

fiber

FIG 2 /G3WPO synthesised CW transceiver block diagram

t Qc

/Y77

Noise

detector

Impulsenose

blanker

CW key

AGCdelay

..)1Product

detector

Side torte path>

[unApGC

lifier

Carrierinsertionoscillator

AFlow passfilter

AFamplifier

/477

Burstnoiseblanker

HAM RADIO TODAY APRIL 1983 49

level to face subsequent attenuationby the noise blanking circuitry andcrystal filter. It will receive no fur-ther amplification until it reachesQ4. FETs in general and junctionFETs in particular show some of thebest linearity of any semiconductoramplifying device. The groundedgate mode is the most linear of allbecause negative feedback is inher-rent in its operation. The other pointabout the grounded gate mode isthat the input at source terminal isalmost purely resistive providing agood termination for any filter com-bination.

The output from IFT1 and IFT2will be in the region of 50 to 100ohms. The FET should be able tomatch this. The parameter whichcontrols this is device trans-

RFinput /output

21:1-0

R35

Noiseblanklevel

C3410n

conductance. In the days of valves itused to be quoted in mA/V, a nicecomprehensible unit. These daysmillimhos, micromhos and siemensare all the rage but they amount tothe same thing. The J310 devicequoted for Q1 has a transconduc-tance of between 10 to 18 millimhos,in English 10 to 18 mA/V. As a com-plete aside, I always think to myselfof some spotty youth, somewhere inthe development labs of SiliconValley inadvertently rechristeningsomething which had been knownand understood by the valve worldfor ages. Anyway, if the current in-creases by, say 10mA for every volt,then the equivalent sourceresistance would be 100 ohms. A 5millimho device such as a BF256would have an input resistance of

+12V

R3 100

C5 RFC2100nZ iqopH

Point A C4 1nnoise blanker - I

chainDBM1

SBL1

IFT1

VFO input

C1

15p

+12V +12V Rx +12V Tx

0551 0561 0571100n T 100nT 100n

Q1

f..13101

IFT2

RFC11000

C6 1n

Ferritebead

R4100

C54 =1nNoise blanker switch -

09

+12V Rx

C58 100n

IFT9

C38

100p

12N29071

RFC3100pH

1N914

200 ohms, too high for the intendedapplication.

For linear operation, the FETshould be biased to a fairly highoperating current. RI in the sourcecircuit should set the standing cur-rent to about 15mA although the ab-solute value will vary from device todevice. There are a few comments tomake about the gate circuit. Nor-mally with 'grounded gate' it shouldbe just that. Effectively it is, in thereceive mode. In transmit, the TXcarrier is injected onto the gate. 01then acts as a source follower andthe signal travels backwards overthe receive path to the doublebalanced mixer.

The other point about thegrounded gate mode is that the in-put at source terminal is almost

+12V Rx

R8 220

10nC7 I

.1. C8wri100n

/47 R7

T1

1W

220 R11

C9 10n

C12 22 p

R14 :.:4k7

R16 1M

1N914 1N914

470

F2

T2

1VN2222LM1

C41 R50100nT 39k

1BC2381

C39 10n C42 270p

R48 1k

Q3

CWtitter

R12Seetext

+12V

IBC2381

220

X2

10.7MHz

R51 27k

C45

10-60p

1N914

+12V Tx

Txfrequencyadjust

C16 .C" -10n

C13I 4).0

D6 R17

1k

C441-

X3 1-107MHz

It!

BFOadjust

C4f10-6

50 HAM RADIO TODAY APRIL 1983

-12V Rx

20 2220

purely resistive providing a goodtermination for any filter combina-tion.

The ferrite bead on the gate ter-minal inhibits VHF and UHF oscilla-tion, an ever present possibilitywhen using high gain FETs. Thegate circuit is also used to injectAGC control voltage but moreabout that later.

Noise blanker

This has to cope with two kinds of in-terference: the impulse type such asthe Russian woodpecker or car igni-tion noise, and the static crash typeassociated with thunderstorms, etc.Equally, the removal of this type ofnoise should not impair the circuit'sability to handle normal signals.

IFT4

R1 100

13

xt

R113

150

04

IlbII o

On a seperate( front panel PCB

+12V Rx

R25 220

C20 11 00n

I3SK511

C1510n

Most noise signals are of theshort pulse type. They are typicallyof very high level but ofmicroseconds' duration only. If youallow them to reach a narrow bandfilter such as the CW filter F2, theywill cause it to ring producing apulse at the output of much longer(and noticeable) duration than thepulse which caused it. The noiseblanker circuitry shown here turnsoff the signal path to the filter for theduration of the interference path.

The wideband signal present atthe drain of Q1 is split into twoparts. The first part - the main part- passes through ceramic filter F1,through Ti, D2 and 3, T2 to filter F2.The second path is amplified wide -

band by Q8 and Q9. This sidechainas it is called amplifies both the

IF T6

C21

X1T3

107MHz Notch frequency

C17=i10-60p

R70 15

R71

100

II

II

II

II

II

11

R24

0

IFT5

R23150

100

05 IF T7

135K511

C1410n R21

100k

O

CI18n

22

100k

C19

15p

+12V

R30 470

C26 ..47/16

R29 2k2 /477/477

C24' 47n

/477 R28

R26

C27 R32

1/25 15k

220

Q6

11$1(511

C25

signal and the interference pulses.However, the interference pulseswill be of much higher amplitudeand will be rectified by the highspeed peak detector circuit D4 andD5. The gain of Q9 and Q10 is ad-justed by varying their gate 2voltage such that the pulses or in-terference crashes producenegative peak voltages just largeenough to turn off Q2, an enhance-ment mode FET.

Q2 is normally held on by asteady voltage present at the junc-tion of R14 and R15. The rectifiedpulses turn it off for slightly longerthan the duration of the pulse. Mostof the current normally flowingthrough Q2 comes via R7, R9, RIO.D2 and D3 are PIN diodes whichconduct RF signal voltages perfectly

10n

+12V

C29 .+.100 /16

/477

1BC2381

R27C22= C23 560

1n 10/25

100k

R31

220k

Q7

R34100k

Volume

C28100n

IC1

[LM3801

C31

100/16

C3010/25

C32 10p

C33 R33 1 100

1n Side tone level

R53 R5639k 560

C47 270p

R57+12V

220

012

IBC238I

R58

27k I R5910k

C48 R55 S meter150p 1k zero

adjust

S meter R60 100k

R7210k

+12V

R6422k

C51 R65

D7 08M

1N914 1N914

R62

220k

4y7/25

R63

C49T47/16

220n 1kpoly

ManualIF gain

C2

69 220k

R66

100k R67 S1k

1

R68 220k C52TO/25

HAM RADIO TODAY APRIL 1983 51

all the time that they are forwardbiased with a vairly substantial DCcurrent. From the RF point of viewthe signal coming out of Fl connectsdirectly with the input of F2 ensur-ing the normal state signal path. IfQ2 turns off during an interferencepulse, R11 will reverse bias D2 andD3 cutting off the signal flow to thefilter. R6 establishes the reverse biasat 4V.

Although filter Fl is shown as aceramic resonator of the cheapotype associated with domestic FMtuners, its function in this circuit isas a delay line. A signal input on Fltakes roughly 11/2 microseconds toreach the output terminal. That of-fers quite enough time to turn off D2and D3 thus blocking the signal pathbefore the arrival of the interferencepulse.

You may ask where good RFdesign comes in. The answer is sim-ple. Sticking diodes in the signalpath is generally a recipe for inter -modulation distortion unless you arevery careful. As far as the signal isconcerned, the diodes operate inpush pull reducing the residualdistortion to a very low level. Thereis also another reason for using apair of diodes in this manner. Q2switches off fairly fast. With circuitsof this type, you have to be carefulthat the induced switching tran-sients aren't actually worse than thepulse interference that you are try-ing to suppress. Since both diodesswitch simultaneously - they areDC balanced by the series resistorsR9 and R10 - switching transientscancel out, in theory at least. Thetransformer construction and cir-cuitry layout require considerablecare to achieve this in practice.

FilterFilter F2 is a standard monlithiccrystal filter of whatever bandwidththe user wants. Generally 500Hzbandwidth is adequate for CWalthough there are no special tech-niques required for using filters ofother bandwidths. The importantnote about the filter is the termin-ation resistance. The input to F2would already have a resistive ele-ment reflected all the way back tothe drain circuit of Q1 via the noiseblanker switch circuitry. Howeversome trimming by R12 will almostcertainly be necessary. F2 wouldtypically have an input/output im-pedance of around 500 ohms.

On its own, the input im-pedance of Q4, the first narrowband IF amp would be in the orderof 100's of kilohms when resonatedat 10.7MHz. The reflected im-pedance through to the filter fromthe IF transformer will probablyneed adjustment. R13 provides thisand would have a value possibly inthe region of 50K ohms. This wouldof course appear as several 100ohms across the filter.

The output from Q4 goes to thenotch filter circuit via IFT4. Thisnotch circuit has an insertion loss ofless than 1dB but is capable of pro-viding a 50dB null. Interferingsignals in the passband of the CWfilter can be effectively removedwith this type of circuit. The ques-tion has been asked: "Why not use avaricap diode for the notch tuningcapacitor (C17)?" Well, you coulddo but the bandwidth and depth ofthe notch would be seriously im-paired because varicap diodes of alltypes are very lossy devices. Atseries resonance, the crystal X1represents pure resistance in theregion of 10 ohms. This is balancedby a real resistance on the oppositeend of the centre tappedtransformer. At resonance, bothcancel out the signal path verysharply, eliminating an interferingsignal almost completely. R71allows fine adjustment for maximumnotch depth.

AGC circuitry

Things are fairly straightforward upto the product detector, Q6, A smallamount of RF from the transmitoscillator circuitry (Q10, Q11) is in-jected into the product detector toprovide sidetone on transmit. Q7 isa bipolar transistor driven from thenoise blanker line. If there isenough high level interference pre-sent, the drain voltage of Q2 willspend more time up than down andcharge up C13 through Q3. Q7 willthen go into conduction and shortcircuit the audio signal to the poweramplifier. This gives protectionagainst static crashes of the typewhich otherwise take out the ear-drums.

Why am I pointing this out?Well .. .it's a case of good designwhich is what this article is suppos-ed to be about. High level in-terference signals are unable to findtheir way to the AGC amplifier IC2,(as well as the ears) allowing the

AGC to respond only to the signaland not to the interference. Anotherpoint. The circuitry as shownenables the AGC line to swingnegative of the earth rail offering acontrol range of about 80dB whenapplied to the gate 2 structures ofQ4 and Q5. Hopefully, the completetransreceiver will boast a dynamicrange of better than 100 dB whichmeans that the AGC line would fallshort by some 20dB of controlrange. The difference is made up byapplying AGC to the IF pre -amptransistor Q I. This stage operateswith delayed AGC. Signal levelsneed to be in the medium to highrange before the AGC rail will besent negative of ground. The AGCdiode DI ensures that AGC will af-fect Q1 only for high level signals.This is done to maintain strongsignal performance in the presenceof weak signals and maintain Q1 inthe state for optimum signal to noiseratios while permitting gain con-trols.

Other considerations

There are a couple of critical signalpaths which require careful layoutof the PCB if the overall board per-formance is not to be jeopardised.

The first of these concerns theBFO circuitry, Q12. The beat fre-quency oscillator provides a carrierwhich is a few 100's of Hertz awayfrom 10.7MHz to provide an audibletone when mixed with the incomingsignal in the product detector, Q6.The BFO signal, with an amplitudeof around a volt, is almost at thesame frequency as the incomingsignal, typical level in the microvoltregion. Careless layout can causethe BFO signal to find its way intothe front end of the IF strip causingblocking with subsequent degrada-tion of the system noise figure.

Like all RF circuitry, this type ofunwanted coupling can be minimis-ed by using double sided circuitboard material even though ground -plane design rules need not be ap-plied for impedance matching pur-poses.

The same comments about un-wanted coupling apply to the crystalfilter. A good quality componentmay exhibit upwards of 90dB out ofband rejection. However, unlessvery careful screening proceduresare used to separate the input/out-put circuitry, all those dB's willbe wasted. G4JST

52 HAM RADIO TODAY APRIL 1983

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Ham Radio Today, April 1983

NEWCOMER'SLicence conditions, how often should you utter yourcallsign, thieves, rotators, aerial design and decibe-- is are just a few of the topics covered this month

Letters

Kathryn Jackson, G6LHY, queriedwhether I knew my Licence. Well, Iknew I had one somewhere, andeventually found it, so I can confirmthat mine reads the same as yours! Ican see the reasoning behind yourquery, and it all hinges on the actualwording used in the Licence. It says"each period of sending", and not"each transmission", which is subtlydifferent. The latter would make itobligatory to use your callsign at thestart and finish of each individualover. The words "period of sending"are quite a lot less demanding, and Ibelieve were substituted to this formsomewhere in the 1960's to reflectthe problems raised by the growinguse of SSB and VOX. These madetelephone style conversations pos-sible, whereas previously with mostactivity being on AM, the overstended to be complete inthemselves, as they are now with alot of FM.

The "period of sending" canencompass a complete QSO, fromstart to finish, hence the require-ment for repeating the callsign if thetime exceeds 15 minutes. It allowsnatural conversation withoutcallsigns being repeated ad -nauseam every few sentences,which is the point I was trying tomake in the January issue.

In practice, very few people willgo a whole 15 minutes withoutcallsigns, and it is very much up toyou how often within the 15 minutesyou do state you call. Certainly in anet of several stations, you would beadvised to use it more often, other-wise it is difficult to know when astation has finished his (or her) over.

Also, there is no requirement inthe Licence for the callsign of thestation being worked to be repeatedat any particular interval. In fact, itdoesn't ask you to say it at all, ecept

indirectly under section 2(d), whenit requires you to establishcommunication initially with eachseparate station contacted. Ofcourse, it must be entered in the logbook. Again, a relaxation for Nets,so that a large one doesn't getbogged down with regurgitatedcallsigns every over.

Of course there are stations whodon't use their callsigns very often,or if they do, omit the prefix forsome reason best known tothemselves, witness a certainnightly net on 80m. Besides makingit very annoying to listen to, youshould hear the number of times onestation stops talking, and severalothers then all chirp in at once forinstant chaos!

dbW Power (WI

9 815 3216 4020 10022 1602c, 400

1

Table o dbW terms used in amateur licence vsactual power 1500 system I

Morse methods

Roger Stroud, G 4PSJ, writes to saythat he found the best way to learnMorse was to take it in 15 minutesperiods maximum at a time, but lotsof these, filling up your tea anddinner breaks with practice ses-sions, and adding at least an extratwo sessions in the evening. Thismethod got him the pass slip in theperiod between the RAE and theresults of same coming out. I wouldagree - don't do too much in onesitting or you will probably end upslowing down rather than speedingup.

Another of Roger's tips was theresult of having a 10 metre dipole

up, but finding that the band hadclosed the time he got home. So,armed with the right lengths of wireand some croc clips, he lengthensthe dipole the right amount for 15metres and then works the DX there!A useful idea, and one which couldbe usefully extended to the otherbands, even if space is short.Providing the main centre portion ofthe dipole is in the clear, this beingthe high current part which does themajority of the radiating, then whatyou do with the rest won't make a lotof difference to the signal. bendingit around will tend to mean the aerialneeds to be shorter than the calcula-tions will tell you, but this can bedetermined with the aid of an SWRBridge (preferably one using someform of transformer coupling, asthese tend to be more accurate thanthe cheap trough line type) forgeneral use.

Watch what you say

Very few of us stop to consider whomight be listening when we are gailychatting away on the air. Most of thetime it doesn't matter, but there areoccasions when you may later regretparticular statements. I am referingin particular to those stations whohappily inform the world on one ofthe 2m FM channels (and heavilymonitored if you think about it) that"I'm out for the day, got the XYL andkids with me, be back late thisevening".

There are those who will delightin this type of information, and laterrelieve you of much of the contentsof your house, and or shack. 2m rigsare cheap to buy and provide anideal monitor for theives. So don'tmake the sort of statement aboveover the air, no matter how temptingit is to tell your mates where you aregoing.

On the above subject, one of mylocals, Mick, G6MYB, recentlyawoke to find that he had beenvisited in the night. The shack isoutdoors, luckily the rig was

54 HAM RADIO TODAY APRIL 1983

FORUBy Tony Bailey G3WPO

indoors. However, and this is thefirst time I have heard of this hap-pening, they took down the mast(guyed), removed the top five feetcomplete with rotator and 4 elebeam, and added the control unitand an SWR Bridge to complete thehaul. So, it appears, nothing issacred anymore.

If anyone is offered aHirshmann HR250 Rotator, with thecolour codes of the connectionsscratched on the casing, locally,you know who to contact. On alighter note, I did suggest thatmaybe the neighbours were fed upwith the TVI, and had decided ondrastic action .

Mentioning Rotators...

What have you got on top of yourrotator? Yes, a beam(s). Have youconsidered whether it/they will staythere during the next gale? Manypeople don't worry too much whenthey use a fairly small rotator, oftenintended for a TV type array, tocarry a largish VHF array. As therotator seems to turn it OK, theredoesn't appear to be a problem.However, if you think about how therotator is constructed, and then con-sider where the stresses are when aheavy wind blows, you may see thatit is possible that the gearing usedwill not withstand this force. Theresult of the turning motion appliedby the aerials can be that the gear-ing strips, and allows the top half ofthe rotator to run freely. Brakingsystems are not usually fitted tosmall rotators, so this is a distinctpossibility.

It is even possible that therotator housing may part companywith the rest of the system. If eitherof these happens, you could have adistinct mess on your hands,especially if the gale keeps going.So, give some thought to using thecorrect rotator to the job, adn takethe advice of your local dealer, itcould save a lot of heartbreak andeffort in the long run.

More Licence problems

There seems to be some confusionover the recent Licence changeswith regard to the specifying of thepower levels in dBW, rather thanthe rather more straightforwardstatements of actual power in watts,so I thought it might be useful tocover the area of dB's and how youare most likely to meet hem inAmateur activities. As well as dBW,and straight dB's, you will also comeacross dBi, and dBd, not to mentiondBm!

The decibel is a RELATIVEpower unit - a statement of 12dBdoesn't mean anything unless youalso state what you are referring to.It is a logarithmic unit, and arosefrom the fact that the human ear hasa logarithmic response - if youlisten to a signal say running 5Woutput (RF or Audio) and then in-crease this to 50W, you might guessthat the apparent loudness had in-creased by a factor of two. If youconducted the same test running 1Winitially, and increased this to 10W,you would make the same estimation(or 500W to 5kW, etc). The formulafor decibels equal to a POWER ratiois:

dB (power) = 10 log 10 P2P1

So, the increases above are10dB or a ten times increase. 3dB istwice the power, 6dB four times,20dB is 100 times etc, etc. The wordPOWER was emphasized above, asvoltage or current ratios are slightly

ION

different, in that a doubling involtage is a 6dB increase:

dB (voltage) = 20 log V2VI

The important thing toremember is that the second formulacan only be used for comparingvoltage ratios if the impedanceacross which each voltage is beingmeasured is the same.

If the answer is positive, youhave gained in the system, if

negative, a loss.

Relative dBs

As we said earlier, the decibel is arelative unit, and when used in thismanner needs a reference value.The term "dBW", now used in thelicence to specify transmitter out-put, means "dB's relative to 1 watt",so that OdBW is the reference level(NOT 1dBW) of 1 watt. Then you justfactor it up depending on thenumber preceding the reference.10dBW would be 1 OW ,20dBW =100W , 22dBW =160W etc.You can use log tables to get the ac-tual factors, or much easier use acalculator.

dBm's are another one - thistime the reference is 1 milliwatt(OdBm). You will sometimes seelevels of spurious radiationspecified as not exceeding XdBm -so that I5dBm would refer to 32mWof power. Incidentally, the + ve signahead of these ratios is omitted byconvention, but a negative signwould be used if needed. A figuresuch as - 3dBW would indicate apower drop by a factor of 2 - in this

HAM RADIO TODAY APRIL 1983 55

case to 500mW ( - 3dB on 1 watt).100mW could be expressed as- 10dBW, or even (+)20dBm.

Sound levels are often quotedon the relative dB system, ideal forreasons already mentioned, with thereference as 10-16W/cm3, which isthe threshold of hearing at 600Hz.Pain starts at + 130dB on this level.Have you ever considered thedynamic range of the human ear onthis basis - it is better thananything Yaesu will ever do at1301B, or a ratio of ten trillion toone!!

Aerials and dB

The other reference terms you willmeet ar dBi, and dBd, which haverelevance to aerials. The former isgain relative to an Isotropicradiator, adn the altter, to a dipoleradiator. You will remember that theIsotropic radiator is the one thatradiates equally in all directions atonce, usually represented as beinga point source within a sphere, andequally illuminating all of its inter-nal surface.

As there is no practical versionof the isotropic radiator, ALL aerials

have gain by comparison with one!This does make dBi popular with themanufacturers, but I suspect con-fuses the average purchaser, whowould rather have dBd, as at leastthe dipole exists! A half wave dipole(in free space) has a gain of 2. ldBi,so remember to deduct this figure ifyou want to compare with a dipole.

Power or antennas

One station was heard to commentthe other day that he was running50W output, and was going to builda new linear to get 100W. Thiswould increase his signal, hethought, and maybe at a later stagehe would change his 5 elementbeam for something larger.

To my mind, he was going aboutthis the wrong way. The increase to100W, is of course a voltage in-crease of 3dB. As you probablyknow, the usual reckoning for 1

"S -point" increase in signal strengthis 6dB, so he would be better off by1/2 an S -point.

Adding a further 5 elements tohis antenna would have gained himabout the same increase, but also

have the advantage of increasingthe received signal strength by thesame amount. In fact, the increasein both directions will probably bemore, because the angle of radia-tion of the antenna will be lowered,adn this in itself will increase thestrength of the more distant stations.Adding 5 elements on HF is a bitmore difficult, but the same thingstill applies - the better the aerialthe better the signal in both direc-tions (well, almost always . . .). If youare already running high power onVHF, then the antenna changesmust be the most cost effective wayof getting out a better signal.

If you run an omni-directionalantenna on FM, think about a beam- you will find the increase insignal strength very worthwhile,even with a two or three ele, and beputting all your hard earned powerin the right direction, not wasting itwarming up the ether. For generalmonitoring, collinears and the suchare good, but they are a bit anti-social on transmit, especially inLicencees on VHF/UHF, the use ofdirectional beams does extend thenumber of stations that can use achannel at any one time. 0

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MBA -RCBy Tony Bailey G3WPO

SPEED 60

A.\\( II) I t.1C IRONIC APPLICAIIONS INC .

75 110.

' SF_ 67 100 ASCIITRANSMIT

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In the very first issue of thismagazine, we reviewed theCWR-600 morse/RTTY decoderThis somewhat larger box of tricksfrom a different stable will doexactly the same thing, with the ad-vantage of having a 32 characteralpha -numeric display built in to it,so you don't have to tie it up to amonitor or TV. It is one of a range ofunits, and is the top -of -the -line ver-sion.

However, as it costs somewherearound twice the price of theCWR-600, you might guess that it

has a few tricks up its sleeve - andyou would be right. For a start, it isalso a Transmit as well as Receiveunit, coping with RTTY, Morse andASCII transmissions. So that's whatthe extra money gets you then?

75 110.

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Review

OUTPUT60 75 110 MORSE 60 75.

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TRANSMIT

Well, not quite, the best is yet tocome. Frank said to me "Want toreview an RTTY decoder?". "Ofcourse, but I can't send RTTY withit, unless it'll hook up to myTRS-80", replies I. "Want a bet",replies Frank, "You've got a Morsekey, haven't you?".

RTTY with a morse key?

That's exactly what I said . . but itdoes just that. You will notice fromthe front panel illustration that thereare four separate slike switches,each marked with similar sets ofmode information. The left handside pair sets what happens in thereceive (INPUT) mode. Slightlyconfusing because the left switch ismarked Transmit and the next one

110 MORSE

r 100 300 I DRECEIVE

Receive. What it means is,"Receive" is the input TO the unitFROM the receiver audio output.i.e., if you are receiving MorseCode, then you set the INPUTReceive switch to "MORSE".

By Transmit it means what YOUare transmitting TO the unit. Thereason for this is that these two set-tings don't have to be the same, aswe will demonstrate in a moment.So, if you are inputting 45.5 BaudRTTY from a teletype machine intothe unit, then you set the INPUTTransmit switch to "60" (which is 60wpm RTTY = 45.5 Baud).

Moving onto the OUTPUT side,you will have guessed that this si thetransmit side, except why two swit-ches? Well, the OUTPUT Transmitswitch is what you would expect - it

HAM RADIO TODAY APRIL 1983 57

ONLIPL BE FRIRT FR1FITText shown on front panel alpha-numeric display

RI: .UR R51- HERE 1:5 glq

10 1 KILOWATT INTO R TRIBANBER

determines what the unit outputs tothe Transmitter. The OUTPURReceive switch controls what th unitoutputs to an external printer whenreceiving a signal off the air. If youwere using a Teletype then youwould set this to "60" again. If anASCII printer, then 110 or 300,depending on the printer. In the"MORSE" position it translates thereceived signal into Morse Code (nomatter what it was in the first place).

No, the manual isn't muchbetter at explaining it either, andalso admits to it being confusing,but you should have the hang of itby now!

Mixing modes

Going back to our hand key, it isperfectly feasible - and this washow the reviewer had all his RTTYQSO's - to plug an electronic orhand key into the unit, and whilesending morse code at whateverspeed you could manage into theunit, leave it to happily output RTTYto the transmitter. The station at theother end is none the wiser, ofcourse, until you tell him that youare sending with a Morse Key. As itwas around Christmas that thereview was done, a few stations mustbe forgiven for thinking theChristmas Spirit had got to at leastone G!

This mixed -mode operation isthe best feature of this really cleverunit. It is possible to mix virtually all

50 HOW BIB rou PRINT THAT BOB

I BERUEOPA'ER4FIRG ZE TU2GR TU2GR

of the combinations shown on thepanel - the unit also has its owninternal speaker and this can bequite unnerving to visitors. Theaverage visitor gets a little confusedat hearing the station receiver tunedto an RTTY signal, the same signaldecoded on the units display, alsohardcopied to a printer, and at thesame time being re -encoded andsent out of the unit in Morse Code!

Facilities

Having whetted your appetite at thesort of things possible, we will havea closer look at the multitude of con-trols available to aid operation. Ithas to be said that a period ofplaying around with the unit onreceive only HAS to be gonethrough first, otherwise you can getin an awful muddle very quickly!

Taking the front panel controlsfirst:

SLIDE SWITCHES: the basicsettings have been mentionedabove. In addition, there is a"SPEED" setting which allows theunit to display (in MORSE code onlymode) the speed of both receivedand transmitted Morse signals. This

appears on the very right of thedisplay, and appears to be accurate,as it agreed very closely with theW lAW test transmissions.

Also, the "ID" setting allowstransmission of an identificationsignal, such as "de G 3W POG3WPO K". This may be sent ineither RTTY or Morse Modes, and isprogrammable into a 40 charactermemory. The programming can bedone either using a morse key, orkeyboard (either Baudot or ASCII),and an LED illuminates when thememory is full.

Note that this is the only actualprogrammable memory available -the unit will not allow completemessages to be stored such asequipment details (unless you usethe I.D. facility for this).

FILTER: The unit has threemodes of audio filtering available.In the "CW" setting, the bandwidthis approximately 900Hz-950Hz, andfairly sharply peaked in practice. In"170" position, the unit is peaked foramateur and commercial 170HzASCII/Baudot transmissions withMARK at 2125 and SPACE at2295Hz.

In "VAR", the MARK tone stays

H EEH EE,SOWL GIVE HIMA RING FOR SURE= MNI TNX VERY PLEASANT 73ESWL CUSN IF NOTBEFORE THEN IN MARATHON IN WHICH I MAY BE OPERATING AS G W 3XTJ IN N OR T5 WALES

= GMIII ST ILL THINK IT IS MORNING BEG: GOT UP SO LATE H EE G A G A NENEOT CULF9U0 DEG3XT ET 5 EE E E AT GA ALTTE W TMTU EEI = HOPE U GETTHAT CQ TIL COPY FEEDALE HI AR SKEE EU CIED EE FUEGVB TNBTNEC T MIFB G3IFB DE F9U0 F9A0 GA N S FA TIRTMM ES TKS FOR CALL = ETR RST579 57 579 = QTEI IS BUEIES BURES N AR PARIS ES FO

KE IS 1336 3IM6 = WELL FRANK VY PEEED TO TUSO U TO HEOTE THIS BAND OB = HW? G3I

FB DE F9U0 KN E EE UETNBRBWTRCHERRENE= E VYPSEDTTM TTTTU5NEWBNDESTNBRPRT=RST5555FB=FATTTAHPEUHADBTTAS=ESWISHUESDEDEEFBNEWYEAR=FETNBK R TT N EITEXTE UO AU E E N

Typical reception of hand -keyed Morse Code on 3.5MHz band

58 HAM RADIO TODAY APRIL 1983

peaked at 212SHz, but the SPACEtone can be peaked anywherebetween 2225 and 3125Hz, thusallowing virtually any other shift onRTTY to be tuned in.

CW TUNE/ AFSK SHIFT: Thissmall window conceals a bargraphtype LED display which is used forpeaking signals. It is far easier touse on RTTY than describe, and themanual deals with this adequately.Once familiarised, you can tune inan RTTY signal in a second or so.

The knob to the right controlsthe frequency of the audio filter in"VAR" mode.

CR/ LF - AUTO: These twocontrols allow for control of printercarriage return/line feeds. The firstwill send a CR/LF when depressedonce, either when receiving ortransmitting Baudot/ASCII, and isuseful for generating missedinstructions on receive.

The second activates an internalcharacter counter which willgenerate a CR/LF character at thefirst space following 60 characters,or after 71 characters have beensent. This saves having to keep tabson what you have sent when using akey to send RTTY, and stops thechap at the other end having to in-sert CR's.

NORM/ REV: The usual switchto allow reversal of the Mark/Spaceconventions. Normal is with theSpace tone higher than the Mark.Sometimes the other station willhave his tones reversed, usually inerror, or the receiver may be set tothe wrong sideband for correct tonerecovery, and this switch allows thisto be corrected.

OFF/ ON: Controls power to theunit.

BUFFER FULL LED: Besidesindicating the I.D. Buffer is full,there is also a 1024 characterreceive buffer used for the outputdevice. This LED will light whenthere are only 25 characters left. Ifthe buffer does fill completely, thedisplay blanks, but none of the buf-fer contents are lost.

The reverse of the unit has anadditional five pushbuttons, twopresets, and 13 sockets. The twopresets allow the volume level to theinternal speaker, and the outputlevel of the AFSK tone to thetransmitter to be set.

The pushbuttons cater for con-trol of the external hard copyprinter, which may be disabled onTrnasmit or Receive or both; a

A FARM WHERE GODA CHEESE IS MADE AND BECAUSE I LIKE CHEESE

VERY MUCH I BOUGHT MANY KILOS OF CHEESE AND BROUGHT IT

BACK WITH ME TO GERMANY.... AND WE VISITED THE CHILDRENS

PARK I BELEIVE IN THE SUBURBS OF AMTERDAM CANT REMEMBER

BUT I AM SURE YOU KNOW THG PRRCQX UMBTBHEUVMTED TO THE

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AND OF COURSE ZHE HOUSE OF PARLIMENT IN THE HAUGE .... AND

Copy from external printer

"down -shift on space" (both transmitand receive to help prevent garbledcopy) facility; and the TransmitAFSK Tone shift, at either 170 or850Hz.

The next set of sockets are allphono type. Tone Output, twotransmit key outputs (one positive,one negative), the Transmit/Receiveinput (close external contacts totransmit), and two more for Markand Space outputs to a Scope fortuning purposes. The remainingphono outputs a TTL level teletypesignal, low during Mark.

Audio input to the unit is via a3.5mm jack socket. This input isquite sensitive and happily allowsdirect connection across an existingspeaker. An additional jack alsoallows audio output from the unit (itis in fact paralleled with the otherjack).

Printers & keyboards

A 26 pin connector allows interfacewith an ASCII printer and keyboardif desired. This is a parallel Cen-tronics compatible, for Centronics,Epson, and almost any of the otherpopular printers. The connectortype isn't defined, but is availablefrom RS Components if you need toget one. Also the connection detailsgiven on page 32 of the manual havegot one pin number wrong - underOUTPUT PINS, pin 1 should readpin 7, otherwise one of the data lineswill end up at Ov.

For the review, an EPSON MX80was used for hard copy, wiredexactly as per the manual (exceptpin 1!). This worked perfectly satis-factorily, although generating anextra line feed (which could havebeen removed internally by reset-ting a DIP switch internal to theprinter).

Standard current loop input andoutputs are also provided for

teletype machines, with theseisolated from the rest of the unitselectronics by opto-couplers. Themanual luckily warns you that theexternal supply MUST be limited to60mA, as this is not done internally.

The remaining socket is that forthe key, a standard 0.25" jack. Itmay be connected to a key, or apositive keyed output from a keyer,or to a keyboard unit's output.

Interfacing with a micro

If you want to go the whole hog andinterface the unit with yourmicrocomputer, then an RS -232Cinterface could be hung onto thecurrent -loop input/output terminals.However, if you have a computer,you probably won't be using thisunit anyway, as the majority of theelectronics will already be in yourpossession. For somewhat less thanthe cost of this unit, you would beable to buy a very comprehensiveRTTY/CW program, complete withmessage storage facilities etc. andthe facilities such as sending RTTYusing a morse key would have littlerelevance.

If you do use this facility, notethat the MBA -RC, although it willoutput 300 baud ASCII to a printeror the Transmitter, will NOT acceptit as input either from a keyboard orreceiver. If you're going to inputASCII, you will have to configureyour RS -232C interface for 110baud, and the other station will alsohave to send at this speed. Thiscould be a positive disadvantage, asa lot of ASCII activity in this countryis on 300 or more Baud.

Manual

A 45 page photocopied instructionmanual is supplied with the MBA -RC. Although the instructions arecomprehensive, and include nine

HAM RADIO TODAY APRIL 1983 59

illustrated examples of using theunit in various combinations ofoutput/input, it does need carefulreading to digest properly (you'renot kidding - Ed). Even themanufacturer admits that theexplanations do not come simply"due to the tremendous flexibility"of the unit. If you do intend inter-facing with a micro -computer, youwon't find much help in the manual.

A circuit diagram is provided ofboth the analogue and digital sec-tions of the circuit, together withparts lists and pcb layouts. Noexplanation of the circuit operationis given, so unless you are into thesubject, you may not be able to ser-vice the unit yourself. Twomicroprocessors are used to providethe facilities (3870's). The unitrequires 13v DC +1- 3v at 1.2amps maximum.

Only two phono plugs were sup-plied - if you need any of the otherconnectors you will have to supplythese yourself, including the coaxialDC input plug - the one supplieddidn't fit the socket. The socket has aslightly smaller coaxial centre thanthe ones easily obtainable in thiscountry. Also beware that the centrepin is the positive connection -other equipment uses the outersleeve as positive, so check beforeplugging in if you do have one thatfits already.

Construction

The decoder is housed in a substan-tial steel two-part cabinet - thecover can easily be removed by un-doing a handful of screws - andreveals a very well engineeredpiece of equipment inside. Thereare two major pcbs on the lowerchassis, one above the other, and afurther set up against the front panelfor the display and switches. If youdo need to remove the cover, takecare as the internal speaker is on aflying lead, attached to the topcover.

The circuit boards are screenprinted with component positions,which should aid any attempted ser-vicing. The review sample didmanage to fail at one point, and wasreturned promptly with a blowntransistor replaced.

The MBA -RC on theair CW

reviewed earlier, when the MBA -RCis used for decoding Morse, it isvery dependant on the quality of theinput for accuracy of decoding. Thespeed at which code is transmittedfrom the unit can be programmedinto the decoder, necessary whenusing a keyboard or teletype forinput. If you are using a straightkey, this would normally key thetransmitter directly, without theMBA unit being involved. However,it is possible to say input at 15wpmfrom a key into the decoder, and getit to retransmit at a higher speed. Ifusing the ID storage facility, thismight be useful for MS work, butyou are limited to 40 characters ofmessage. Otherwise one of the lessuseful facilities.

It was rather interestingwatching the decoded output versusthe type of sending. Best accuracyof decode was with machine sentcode, as might be expected, follow-ed hard by well sent hand or elec-tronic keyed morse.

Brain vs machine...

The one variety it didn't like was theVibroplex type of semi -automatickeyer, the error rate being veryhigh. The human brain gets used todecoding this type of sending,where the operator inevitably putsan accent on the dashes, and adjustsitself accordingly. The machine onthe other hand just cannot cope withit, as the long dashes do not conform

with any code groupings in itsmemory. It will immediately try toreadjust the speed, then find thedots don't match the dash which itjust received, so it gives up indisgust.

Even poorly sent hand keying,provided the spacing and dot/dashratio were somewhere around theright regions, was reasonably welldecoded, but the human brainwould win most times. One of theproblems is with the abbreviationsused in amateur traffic.

When a station sends "TNX FERQSO ES WILL QSL SURE VIABURO", your brain can almost tellyou what is coming before it is sent,even if the keying is less thanperfect, through familiarity. To themachine, which only tells you whatit actually received, it may appearas "G X FER MASO ES WILL Q SLSUL VV TSURO". All because thespacings were a little out. Result:Human Brain 100% copy -Machine: Dismal failure!

This problem is common to allmachine type decoders, and not justto the MBA. I doubt whether thehuman brain will ever be beaten atdecoding hand sent amateur CW (ora lot of commercial traffic) so theMBA is no worse than any other inthis respect. Given perfect machinesent code, it will return flawlesscopy.

Signal strengths needed to befairly high for reliable copy, muchbelow about S6 and errors were

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TONE - + XMIT p AL LEL. A SC I (OUT IN

00001

131

OUT KEYED KEYED RCV

SCOPE OUT KEYMARK SPACE00

DATA CURRENT LOOPOUT

IN OUT

5

In a similar manner to the CWR600 Rear panel showing connections

60 HAM RADIO TODAY APRIL 1983

increasing. The presence of QRM orQRN also pushed up the error rate.This phenomena is very much lessapparent on RTTY - there is alwaysa tone for the unit to refer to onRTTY, But on CW, no equivalent tothe Space tone, so any form of inter-ference during the key up times islikely to be decoded as part of thesignal.

RTTY

As mentioned earlier, all RTTYQSO's were conducted using anelectronic key as the input to theMBA -RC, rather than any keyboardas such. The unit will accept anASCII keyboard input, use of amicro via an RS -232C, or a standardteletype, and can use any of these tooutput CW as well as RTTY, ofcourse.

Using the key as input isobviously somewhat slower than atrue keyboard, but it does have thesame end results. Keying accuracyis essential, as the same circuitry isused as for decoding on receive.The input code can be seen on thealphanumeric display as it is being

sent, which helps a great deal -also hard copy can be kept on aprinter. Mind you, unless youalready possess such a printer, youare unlikely to want to fork out£300+ for one for this purpose only.

The CW speed input is imma-terial (the MBA will cope with up to80 wpm+ in either transmit orreceive modes), automatically ad-justing to the speed. Very few peo-ple will be able to key sufficientlyfast to keep up with RTTY output (60wpm). Judging by the averagetyping speed of amateurs, this isn't aproblem! In practice you mayactually do better.

Considering the facilitiesoffered by the unit, it is a shame thatno proper message storage facilityexists, such as would be obtainedusing a dedicated micro program,enabling you pre-program in CQ's,QTH and equipment info etc. Thereis a 1024 character FIFO buffer,used when the output device isslower than the input, for instancewhen receiving 110 Baud ASCII,but outputting to a 45.5 Baudteletype unit, or converting to CW.Conceivably this could have been

used as an optional buffer for thepurpose.

Tuning RTTY

The bargraph LED display is quiteeasy to use, once the technique oftuning is mastered. The trick is tostart tuning across the signal at alow beat note, and gradually in-crease until the bargraph totallyilluminates and does not flickerbetween mark and space. This iseasy on 170Hz shift, but on othershifts entails tuning to the Mark tonefirst, then adjusting the variablecontrol for closure of the display.

Copying RTTY

Given almost any sort of signal, theunit copes very well, even in thepresence of QRM/QRN, returningvirtually faultless copy. Signals fair-ly close to the noise can berecovered, but you do need a stablereceiver (and received trans-mission) - a shift of a few 10s of Hzwill introduce errors. The inputfiltering is via active filters, with nophase locked loops to keep hold ofthe frequency.

The display uses all sorts ofstrange characters to indicate suchthings as CR/LF, Bell and the otherBaudot control codes. The Epsonprinter responded quite happily to

HAM RADIO TODAY APRIL 198361

all these, without any signs ofspurious controls being sent to theprinter, or unwanted characters,even during corrupted decoding.The usual symptoms of this arechanged print modes, but will de-pend on your actual printer.

Trying to copy commercialRTTY transmissions led to some funand games. Besides finding thespeed and sense of the transmission,yo are often dealing with an en-crypted code (to stop people like usseeing it!), so the majority of thetime will see garbaged output.When you do find one that is com-patible, the copy is generallyfaultless, _and a good way of usingup your stock of paper on hardcopy.

Incidentally, there is no facilityprovided in the unit for driving avideo monitor, or TV, directly,presumably thought superfluous byvirtue of the built in display andother options offered.

Transmission of RTTY doesn'treally raise any problems, as theonce you have set up the switchesfor your correct input/outputmodes, adn programmed the I.D.the transceiver controls the Rx/Tx

function. Getting an I.D. at the endof the transmission entails shiftingthe OUTPUT Transmit switch toMORSE, and pressing the I.D.Button once.

Caution . . .

The manual correctly warns that youshould be careful of the power inputon your transmitter, as with RTTYyou are running 100% duty cycle,instead of the much lower cyclesdemanded by CW and SSB. Theysuggest 40% of your normal powerrating, but it would be sense tocheck the handbook, and see what isrecommended for FM or AM use.More than adequate gain isavailable from the AFSK outputsocket on the rear to drive virtuallyany rig via its microphone socket.

Conclusions

With no reason to suppose that theunit will not perform as specifiedwith keyboard inputs, the MBA -RCis an intriguing answer to copingwith the various modes of trans-mission now available. For those sta-

lions not already possessing anyform of computer, it could be a veryversatile means of getting ontoRTTY, together with CW and ASCIIfacilities, although you would reallystill want to get hold of some form ofkeyboard if you are going to use it alot. At the price you could invest ina quite reasonable micro, andmaybe even get a RTTY program forit, if it si specifically RTTY you want- and also have the benefit of themicro for other applications.

One of its few limitations is notbeing able to copy 300 Baud ASCII,which will limit compatibility withmany other stations using ASCII.

The MBA -RC does appear tohave an element of being an answerlooking for a problem to solve.While it can cope with all sorts ofmixed modes, and it is great funplaying with it, in the long run itsbenefits seem limited for serious ap-plications.

Taken for the facilities offered,it performs its decoding and otherfunctions very well, and would be auseful addition to any shack, pro-viding you can make use of all thefacilities.

FACTORY APPOINTED YAESU MUSEN MAIN DEALER

FT 102 Full RangeSP 102 External Speaker

with audio filter

FRG 7700 - This Receiverleaves thecompetition standing

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We hold probably the mostcomprehensive Yaesu Sparesstock in Europe. What we do nothave we will get in the shortesttime, if available.

The ALL NEW FT980 plusaccessories - available MarchThe Compact FT77 - Stock by theend of February.

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BEARCAT- DEALER - IRELANDAnnouncing ExStock the fabulousBC20/20FB AM -FM Scanner

YAESU P.M.R. Equipment - FullRange ExStock, includingRepeaters, Patch, Remote

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ALSO:A READY -PUNCHED SCREENED case,with all hardware inc knobs, sockets,screws etc (no speaker) + the meter foronly £18.65 inc.

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LARGE SAE brings more info anddetails of other kits.2M FM 6 CH Monitor Receiver Kit -

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IAMBIC Keyer module (built) 120.65 inc.TALKING DFM only £11.50 inc. and andother specialised equipment for theblind.

AS FEATURED IN MARCH 1983 HAMRADIO TODAY

62

20 FARNHAM AVENUE HASSOCKS WEST SUSSEX BN6 8NS

HAM RADIO TODAY APRIL 1983

SPECIAL PROJECT:

THREE 4CX250's? Set fire to the ether with our new QRO HF amplifier design

DESIGNING: An ultra low noise synthesised VFO system for the HF bandsLOADING: Towers and rotators to the limitOPERATING: How to shoot a woodpeckerWORKING: 2m SSB for just £89TESTING: hand portable multimodes and the credibility gapLEARNING. CW with the help of your ZX81

40 RAPID RESULTS MORSE COURSE offers the mosteffective route yet to your Class A amateur licence

Professionally produced for HAM RADIO TODAY by ShirleyHesketh G4HES and Ron Ray G3NCL, this advanced interactivelearning system makes use of the stereo cassette format toprovide tuition to the 12wpm test standard

With its carefully designed structure, we think that the RAPIDRESULTS MORSE COURSE is more effective than either morseclasses or electronic morse generators

Based on TWO C-60 cassettes, it offers the controlled promptingso necessary for the initial stages of morse tuition, followed bycarefully paced test material to bring the student up to speed.Full tuition notes are provided with the cassettes

To receive your RAPID RESULTS MORSE COURSE simply senda cheque or P/ 0 for £11.45 (inclusive of VAT and P&P) payableto Argus Specialist Publications Ltd, 145 Charing Cross Road,London WC2 OEE. Mark the envelope 'HRT MORSE COURSE'.

HAM RADIO TODAY APRIL 1983 63

AVON

6 GOLF CLUBLANE,

SALTFORD,BRISTOL

Tel: 02217 2402Open' Tues Sat 9am 9pm

Close Mondays

Radio CommunicationsAmateur P M R Marine

12 14 Pannywell Road. Bristol BM OTJ

YAESU

CAMBRIDGESHIRE

WISBECH AMATEURRADIO

The Chase, Chapel Road, WisbechTelephone: 0945 581099

Open: Mon -Se -19-6. ICOM; HALBARAERIALS, REVCO AERIALS, SALES + SERVICEACCESS + VISA, PART EXCHANGE WELCOME

CHESHIRE

NCP COMPONENTS6 Beeston Drive, Winsford. Tel 54294

Disguisediliplexed AE's that work - TX better than1.5:1. Hides fact that rig is in your car. TelescopicAE - can feed BC radio + TX at same time From

E9.75 -E250

LANCASHIREAERIAL BOOSTERS

Trebles incoming weak signalE111 - for VHF/FM radio; B45 - for UHF

televisionNext to the set fitting. SAE for leaflets. E7Electronic Mail Order Ltd,

62 Bridge Street, Ramsbottom, Lancs BLO9AGH

YOUR RIG IN OUR

HANDS

THE YAESU EXPERTS CONSULTG3LLLSales Dems & Repairs + Mod Kits

HOLDINGS LTD

39-41 Mincing La, BlackburnTel: (0254) 59595

CLOSED THURSDAYS

FOR YOUR BUSINESS TO BEINCLUDED, CALL

SHEILA OR JAN ON01-437 1002

LEICESTERSHIREELLIOTTELECTRONICS

RADIO 1111%.1107

25-28 BRAUNSTON GATE,LEICESTER. TEL: 553283

Open: Mon -Sat 9.00am to 5.30pm

LONDON

THE CENTRE10 MERTON PARK PARADE,

KINGSTON ROAD, SW19Tel: 01-543 5150

Open: 6 days 9am-6pm (late night Weds until 8pm)

DAVEMICK

The Enfield Emporium

G8SYGG6LHL

AMATEUR RADIOHours Mon to Sat 9-6. Late Friday 9-8. Sun morn 10-1

281 Hertford Road, Edmonton N9Tel: 01-804 0128

THE MARINE ELECTRONIC CO LTD1-4 Swan Mead, SE1 4SY. Tel 01-237 3474

Open: Mon -Fri 10am-5pmCommunications Equipment for the

Professional and EnthusiastCallers by appointment only

MIDDLESEX

14 COMMUNICATIONS130 HIGH ST, EDGWARETel 01-952 8185/7488/8860

Open Mon -Sat 9am-6.30pm. Sun10am-lpm

Same day Mail Order/24 hr delivery via SecurkorStockists of YAESU,etc

W. MIDLANDSDEWSBURY ELECTRONICS --8-

176 Lower High St, STOURBRIbGETel: (0384) 390063

Open: 9.30-5.15. Closed Thurs. & Sun.ACCESS/BARCLAYCARD

NOTTINGHAMSHIRER.A.S. (NOTTINGHAM)

P. Owen G8UUS3 FARNDON GREEN; WOUATON PARK

NOTTINGHAM: TEL: 0602 280267Open. Tues-Fn 10-5.30 Sat 9-5

YAESU: FDIC ICOM: SOIAMERKAPAP: TOONA

HALBAR: WELL ANTENNAS It OWN GM H.F.

SCOTLANDJAYCEE ELECTRONICSJOHN GM3OPW20 Woodside Way, Glenrothes, Fife KY7 5DF

Tel: 0592 756962Open: Tues-Sat 9-5.

Quality secondhand equipment in stock. Full range of TRIOgoodies. Jaybeam - Microwave Nodules - LAR.

rrawarwran

SUSSEXSOUTHOOWN 40 TERMINUS RD lopp.

EASTBOURNE RailwaySUPPLIES IN: (0323) 639351 Stn.)

Open: Mon -Set 10-6 (Closed Tues)Stockists of: Vaasa, Trio, Tonna, FDK etc +secondhand and ex -Government equipment in

stock

TYNE Er WEAR

Ag""d PLYCrT1761:IICSThieler

RangeFull

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129 Chillingham Rd, Newcastle-upon-TyneTel: 0632 761002

Open: Tues-Sat 10am-6pm

YORKSHIRE14 Cross Church St, Huddersfield Tel:

Open: 6 days 9-5.30. 0484 20774Closed Weds. Thurs 9am-8pm

G4MH Mini BeamAlways a good sekrtion of new & 2nd hand equipment in stock'

Amateur Radio Shop

Please include my business details in the next available issue of Ham Radio Today

Business Name: #°IAddress:

osoTel. No.Open Hrs: 10Contact (Office Use Only):Post to: Emporium Guide, Ham Radio Today, 145 Charing Cross Rd., London WC2H OEE

1

Immo, olmm ,.11=-11.11.00 111

64 Ham Radio Today, April 1983

LOOK NEW COMPONENTS AT GREATPRICES FROM

LETCHWORTH ELECTRONICCOMPONENTS.

SPIRELLA BUILDING, BRIDGE ROAD,LETCHWORTH, HERTS. SG6 4ET. ENGLAND.

(TRADE WELCOME, EXPORT INVITED).LISTS 65p. TEL (04626) 70354 Et 79681.

26p PACKS:100 68A WASHERS. 10 No 8 CUP WASHERS 5 x 5 WAY TAGSTRIPS. 3 x 3.5 .MM JACK SKTS. 2 x PP3 SNAPS. 10M CON- INECTING WIRE. 2 x 1000 uF/50V CANS 10 x 100 uF/40V CAPS,

x 680R 1W RES. 1 87G SKT. 1 BRA SKT. 1 89A SKIRTED. 3 x8 PIN OIL SETS. 1 x 8 uF/350V AX. 1 100K MULTI TURNPRESET.

56p ACKS:10 x IN4002. 10 x IN4005. 10 x IN4007. 10 x .01/100V POLYS10 x .01/400V. 10 x .047/400V, 10 x .1/250V SEE 280. 10 x

1 600V. 6 x 4700 pF 41cV DISCS. 1 x 10 WAY TAG BOARD. 1 x

OCTAL SKT. 8 x GLASS REEDS, 1 EEC 83. 5 x 5mm L.E.D,S.250 ITEM COMPONENTS PACK 12.51100 3W RESISTORS 11.46200 68A HARDWARE PACK 169MULTI -RADIO VALVE OUTPUT TRANSFORMER 50mA/3 ohms

0.45P+ I SW VAT adr115%

LISTENER Et QSL CARDS. Quality printingon Coloured and White Gloss Card at com-petitive prices. SAE for samples S. M.Tatham "Woodside", Orchard Way, Font -well, Arundel, West Sussex.AERIAL WIRE. Hard Drawn Copper 140ft14SWG £6.90, 50 metres 16SWG £5.90 in-cluding postage. S. M. Tatham, 1 OrchardWay, Fontwell, Arundel, West Sussex.

CALL SIGN LABEL BADGES professional-ly engraved, by return of post. £1.50 cashwith order (state name Et call sign) Alymer-Kelly - H, 2 Pickwick Road, CORSHAM,Wilts., SN13 9BJ

AERIAL PARTS14invg Hard Drawn Copper Aerial Wire 20p per m(post 21p per ml; Strong PVC covered stranded AerialWire 8p perm (post 21p per ml; 300 ohm Twin RibbonFeeder 12p per m (post 2p per ml; 75 ohm Twin Feeder18p per m (post 2p per ml; UR43 50 ohm COAX 20pper m (post 3p per m); UR70 50ohm COAX 20p per m(post 3p per ml; UR67 50 ohm LOW LOSS COAX 50p

per m (post 5p per m).

W. H. WESTLAKE, G8MWWClawton, Holsworthy, Devon

ADVERTISEMENTRATES Semi -Display (min 2 cms)1-3 insertions £5.50 per cm4-11 insertions £5.00 per cm12 + insertions £4.50 per cmLineage 30p per word (min 15 words)Box Nos. £2.50Closing date 1st Friday of the monthpreceding publication date.All advertisements in this section must be prepaid.Advertisements are accepted subject to the terms andconditions printed on the advertisement rate card (availableon request)

Send your requirements to BRIDGETTE SHERLIKER.

HAM RADIO TODAY CLASSIFIEDADVERTISING, 145, CHARING CROSS RD,LONDON WC2H OEE.

NORTH EAST AMATEUR RADIODARLINGTON

for Yaesu, Microwave Modules, Jaybeam and accessoriesPAY US A VISIT OR GIVE USA RING FOR IMMEDIATE

ATTENTION TO YOUR MAIL ORDER REQUEST

HP FACILITIESTEL: DARLINGTON (0325) 55969

78 FULTHORPE AVENUE (Mowden Shopping Centre)DARLINGTON; CO. DURHAM

HOW TO GET TO US: Take A67 from Darlington town centre, turn right approx 1,4 miles from centre alongEdinburgh Drive. We are located % mile along this road on the left

COPPER AERIAL WIRE. 14 swg harddrawn, 70' coils, £5.50, 140' £8.90 !ncpostage. T. M. P. Electronic Supplies, Unit27, Pinfold Workshops, Pinfold Lane,Buckley, Clwyd, N. Wales, CH7 3PLTelephone: Buckley (0244) 549563

AVIATION FREQUENCIESThroughout Europe

As used by BA and other major Airlines384 Pages. f3.75 Inc p+ p

Order by phone. Access and Visa welcome.Other lists available.

AOS (HRT) West London Building,White Waltham Aerodrome,

Maindenhead SL6 3NJTel: 10628 82)5362

MORSE CODE CASSETTES. Cassette A:1-12 w.p.m. for amateur radio examination.Cassette B: 12-25 w.p.m. for professionalexamination preparation. Price of each C90cassette (including booklets) £4.75. Priceincludes p&p etc. MH ELECTRONICS(Dept. HI, 12, Longshore Way, Milton,Portsmouth PO4 8LS.

G2DYM ANTI -INTERFERENCEANTI-TVI TRAP DIPOLES

TX Et S.W.L. MODELS OR KITSData Sheets Large SAE. Aerial Guide50p. Indoor and Invisible Aerials £3.50.Callers welcome Tel: 03986-215

G2DYM, Uplowman, Tiverton,Devon

YOUR NUMBER50MHz5 element'144MHz4 element9 element fixed9 element portable9 element crossed'13 element portable'NEW 17 element fixed435MHz19 element19 element crossed'21 element 432MHz21 element ATV144/436MHzOscar Special9 6 19 element'

ANTENNES TONNA (F9FT)ONE CHOICE FOR 6m, 2m, 70, 24 to 23cm ANTENNAS

1250MHz or 1296MHz1:31.741a1 23 element' 125.901b)

4 .23 element antennas - power splitter - stackingframe E140.00IalTelescopic Portable Masts4x 1m f15.964a) 3 x 2m f19.151a)4 .2m 128.75IalANDREW HELIAX LDF4-50 COAXIAL CABLEAttenuation per 100ft 144MHz - 0.8dB435MHz - 1.6dB. 1296MHz - 2.9dB£3.20 per metrelal 'W type connectors for LDF4-50male or female £10.36

MICROWAVE MODULES - ROTATORS -COAXIAL CABLES ETC.POWER SPLITTERS AVAILABLE FOR 2. OR 4

E30.05(al ANTENNAS'Denotes 5011 ONLY - all others 500 OR 750

PLEASE ADD CARRIAGE AS SHOWN (al E4.00; Ibl E1.80.Terms, Cash with order. ACCESS -VISA - telephone your card number. ALL PRICES INCLUDE VAT AT 15%

For full specification of our range send 30p for Catalogue. Callers welcome, but by telephone appointment only please.

E13.011e1E15.441aI£17.461a1128.521a1£27.211a1E35.19(a)

f111.14101:30.05laE26.00(a)E26.001al

RANDAM ELECTRONICS (H)12 CONDUIT ROAD. ABINGDON, OXON OX14 1DB Tel: 10235) 23080 124 hours)

Ham Radio Today, April 1983 65

FED UP WITH BEING MISTAKEN FOR"Rubber Ducks"? Our two colour plastic carstickers say "No, It's not CB, it's amateurradio!" 60p plus 15p P&P. 21 Denton Drive,Brighton, BN1 8LR.

10 METRE and 2 metre linears from £16.FT707 £509. Morse keys £3.95. Full range ofamateur and CB goods. GuildfordCommunications, 0483 574434.

ENGRAVED LAPEL BADGESLapel badges with electrically welded safety clip, mostcolours available. Example: Club Badge, club name,personal name, callsign, with or without RSGB logo -1 to 10 badges 85p each. 10 a above 80p each incP&P. Please use block capitals f all orders, cash withorder, orders dispatched by return first class post.

Club Secretaries please send for sample

DARFIELD ENGRAVING SERVICES39 Cliff Road, Darfield, Barnsley, S. Yorks S73 9HR

Tel: Barnsley 102261752106

Special prices on surplus equipmentEddystone Receivers 770R(VHF) 770U(UHF) £135. Model 830 £170. 730/4500KH-30MHz in 5 bands All in excellent condition. Carr £15.Murphy MOD Receivers £65 Carr £15fte Bantams High band AM untested less xtal and batt £22With xtal and batt tested £30 Avo Valve Tester £25New Z8 Range Digital Multimeters £40 25. PCR Receivers LW/MW/SWwith built-in mains PSU tested £45. Untested less PSU £25.Advanced E2 Signal Generators 100KHz-100MHz £40. P&P £3. Taylor 67ASignal Generators 100KHz-240MHz £45. P&P £312ft Whip Aerials £4, P&P £1.50. Various: Single and Double BeamOscilloscopes, Signal Generators, Valve Testers, Output Meters etc, instock.Surplus Circuits new book containing many circuits and notes cn varioussurplus receivers, transceivers, etc £6.50. Sned 50p for fully illustratedcatalogue (includes £1 voucher). Over 500 sets in stock Avos, amateur rigswanted for cash.

VVeirmead Limited, 139 St Albans Rd, Watford, Herts WD1 1RA

Telephone: Watford 49456. Access Visa cards welcome

BARCLAYCARD

VISA

TRANSMITTER;S RECEIVERS; ETC.All frequencies, well known makes, ICOM, FDK,AZDEN, LOWE, STANDARD, etc, etc. Power supplies,wavemeters, test meters, frequency counters, WelzSWR and Power meters. Microwave modules, linearamps, RTTY etc. Quality equipment for amateur, PMRand Marine use. Aerials, Co -ax cable, plugs. See ouradvert under Emporium Guide. E1000 INSTANT HPavailable and ACCESS - Booth Holdings Bath, 6 GolfClub Lane, Seaford Bristol BS18 3AA. Tel 1022121 2402.Staff includes GIN XLW. Q3X0D, G8DPH.

COMPLETE HF Station for sale, Trio TS520SE matching ATV mike HF5 vertical antenna,£250 ono. Tel: 05366 742406.

TORAIDS, limited quantity micrometalsT20, T30, T37, T44, Zero types (TAN), 40peach. 4 Haddington St, Hove, Sussex. +50p P&P.

CORNWALL Marazion, country chaletsnear beaches. Ideal touring centre. Fullyequipped throughout. G3UCQ, QTHR 107361752982.

BBC MICRO SOFTWARE: RTTYTransceive £7.50. Morse Tutor £3. Morse TXKeyboard £3. QTH Locator £3. Multifile £6.Terminal Units also available: latest lists withorder or s.a.e. Cheques payable R. C. Sterry,BLT Software (HRTI, 1 Wavell Garth, SandalMagna, Wakefield, West Yorks, WF2 6JP.

BUY - SELL - EXCHANGE - UPGRADEYOUR HAM EQUIPMENT

THROUGH ASP CLASSIFIED01-437 1002

Aft

FOR QUALITY CRYSTALS - AT COMPETITIVE PRICES.POPULAR FREQUENCIES IN STOCK

2 METRE STOCK CRYSTALS. Price £1.98 for one crystal ft .74/crystat when two or morepurchased.

HC6,U

30pF TX

HC6/U

30pF TX

HC25U30pF and40pF TX

HC25/U20pF and3013F RX

HC25/U25pF and209F TX

HC825/U

SR RX

RO 4 0277 8 0555 12 0833 14 9888 18 1250 44 9666RI 4 0284 8 0569 12 0854 14 9916 18.1281 44.9750R2 4 0291 8 0583 12.0875 14 9944 18 1312 44 9833R3 4 0298 8.0597 12.0895 14 9972 18.1343 44 9916R4 4 0305 8 0611 12.0916 15 0000 18 1375 45 0000R5 4 0312 8 0625 12.0937 15 0027 18 1406 45 0083R6 4 0319 80638 12.0958 15 0055 18 1437 45 0166R7 4.0326 8.0652 12.0979 15.0083 18 1468 45 0250S8 12.1000 14 9444 18 1500 44 8333.S9 12 1020 14.9472 18 1531 44 8416'S I 0 12.1041 14 9500 18 1562 44 8500'SI 1 4.0354 8.0708- 12.1062 14 9572 18 1593 44.8583S12 12.1083 14.9555 18 1625 44.8e66S13 12.1104 14 9583 18 1656 448750'S14 12.1125 14.9611 18 1687 448833515 12.1145 14 9638 18 1718 448916'S16 12.1167 14.9667 18 1750 449000S17 12.1187 14 9694 18 1781 449083S18 12.1208 14.9722 18 1812 449166S19 12.1229 14 9750 18 1843 44 9250'S20 404t6 8.0833 12.1250 14.9777 18.1875 44 9333S21 4 0423 8 0847 12.1270 14.9805 18 1906 99416S22 4 0430 8.0861 12.1291 14.9833 18 1937

444

523 4 0437 8 0875 121312 14.9861 18.1968 44 9583SR Series Resonance HC25 onlyAlso in stock: RO to R7 and S8 to 523 for following: Saloom F51007. FOX TM56. Multi 11Quartz 18 and Multi 7. Icom IC2F, 21, 22A and 215, Trio Kenwood 2200. 7200. Uniden 2030and Yaesu FT2F 8, FT2 Auto. FT224. FT223 and F7202.Also in stock, 4 and 8MHz TX in HC6/U for 145.8MHz. Icon, crystals TX for 145.6MHzIRRO). 44MHz RX crystals in HC6 for 145.8 and 14518801. All at above price884,886.R010.8811 RB13.R814 and R815.4 METRE CRYSTALS for 70 26MHz ,n HC6/U at C2.25. TX 8 78250MHz RX 6 7466 or29 78MHz in stock70cm CRYSTALS in stock 8.0222 and 12.0333 in HC6 £1.85. Pye Pocketfone PF 1 PF2.PF70 and Wood and Douglas E4.50 a pair or TX £2.25. RX £2.50, SUE11433 21 R80 882R84 886 RBIO R81 1 R813 and R814CONVERTER CRYSTALS in HC I8/0 at E2.85. In stock 38.666. 42 000 70.000 96 000101 000. 101 500 105 666 and 116 000MHz 26.000 HC6 02.00TONE BURST AND I.F. CRYSTALS in HC18/U at C2.25 in stock. 7 168MHz for 1750kHzand 10 245MHz for 10 7MHz IF sFREQUENCY STANDARDS in stock 12.75. HC6 200kHz. 455kHz, 1000kHz 5 000MHz and10 000MHz HC13 100kHz. HC18 1000kHz. 3 5000MHz. 7.000MHz. 10.700MHz.48 000MHz and 100 00MHz 4,000 HC18 £2.00

1

§luartSLab

MADE TO ORDER CRYSTALSSINGLE UNIT PRICINGAdjustment Price end

Price Tolerance Frequency DeliveryGroup ppm Ranges A

Fundamentals 1 200 dotall 10 to 19.999kHz £23002 200 (total/ 20 to 29.999 kHz - E16503 200Itotall 30 to 159.999 kHz E10 504 200Itotall 160 to 999.999 kHz 16.005 50 1 00 to 1 499MHz E6.006 10 150 to 1.999MHz 14 75 E4.407 10 2.00 to 2,599MHz E4 75 14.408 10 2.60 to 3.999MHz f4 55 14 109 10 400 to 20.999 MHz 14 55 £4.00

10 10 21 00 to 25 000MHz 16.00 £4.0010A 10 25 00 to 30.000MHz 18.50

3rd OVT 11 10 21.00to 59.999MHz 14.55 [4.505th OVT 12 10 80.00to 99.999 MHz C500 E5.50

13 10 100.00 to 124.999MHz 16 15 E5.205th 7th & 14 20 125.00 to 149 999 MHz £6009th OVT 15 20 150 001°225,00MHz 17.50

Unless otherwise requested fundamentals will be supplied with 30pF load capacity andovertones for series resonance operationHOLDERS - Please specify when ordering - 10 to 200kHz HC13/U. I 7OkHz to 170MHz HC6or HC33/U 4to 225MHz HC18 and HC25Where holders are not specified crystals above 4 MHz will be supplied in HC25/U.

DELIVERY Column A 3 to 4 weeks. Column B 6 to 8 weeksDISCOUNTS 5% mixed frequency discount for 5 or more crystals at 8 delivery. Price onapplication for 10 or more crystals to same frequency specification. Special rates for bulkpurchase schemes including FREE supply of crystals used in UK repeaters

The above prices apply to small Quantities of crystals for amateur use. We would be pleased toquote for larger quantities or crystals for professional use.EMERGENCY SERVICE SURCHARGES To be added to A delivery prices) 4 working days 112.6 working days 17. 8 working days 15, 13 working days E3. Surcharges apply to each crystalnot each order and are subject to VAT.CRYSTAL SOCKETS HC6/U and FIC25/U 20p. MINIMUM ORDER CHARGE £1.50.

TERMS. Cash with order cheques and postai orders payable to QSL Ltd. All prices includepostage to UK and Irish addresses Please note Southern Irish cheques and postai orders areno longer acceptable Please send bank draft in pounds Sterling

PRICES ARE EX VAT. PLEASE ADD 15%

MARKETING LTD. P.O. BOX 19, ERITH, KENT, DA8 1LHTelephone: 01-690 4889 (9-5) 24hr Ansafone: Erith (03224) 30830Telex: 8813271 GECOMS G (Attention Quartslab).

66 Ham Radio Today, April 1983

Manchester Home Computer ShowMIDLAND HOTEL

April 22/23/24Your diary dates are:Glasgow MayBirmingham JuneNottingham . . . . SeptemberNewcastle OctoberBristol December

Sponsored jointly by:Personal Computing Today

ZX ComputingComputing Today

Micro UpdatePersonal Software

At the Home Computer Shows will be a complete cross section of thehardware and software available to the home user. The emphasis is on thelower end of the price bracket with computers from £50-£400.

If you are interested in computers and what they can do for you then comealong to our COMPUTER ADVICE CENTRE: experts will be on hand togive you impartial advice on equipment available.

Try out the machines in our own demonstration area and see programsrunning covering educational, games and small business applications.

There is a COMPLIMON at every show to:WIN TWO COMPUTERS.

Win a computer for yourself as well as one for the school of your choice:free entry form with advance tickets. Also available at the show with theshow catalogue.ADMISSION £2.00 (CHILDREN UNDER 8 & O.A.P's FREE)AND IF YOU'RE A PARTY OF 20 OR MORE, THERE'S A 25%DISCOUNT

Friday 22 April '83 (10am-6pm)Saturday 23 April '83 (10am-6pm)Sunday 24 April '83 (10am-4pm)#

`1_4pc.)S

(4,

The Manchester Home Computer ShowMidland Hotel. (Opposite Town Hall).

For advance tickets send cheque/postal order to:ASP ExhibitionsArgus Specialist Publications145 Charing Cross Rd,London WC2H OEETel: 01-437-1002

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