r a d i...1995/03/04 · r a d i an introduction to amateur radio-for beginners of all ages o...

R A D IAN INTRODUCTION TO AMATEUR RADIO - FOR BEGINNERS OF ALL AGES

O

Available only by subscription from RSGB, Lambda House,Cranborne Road, Potters Bar, Herts. EN6 3JE

COVER PICTURE:In this issue we are looking at tworadio pioneers: Samuel Morse, whosecode was invented long before radiobut it plays a large part in the historyof radio communication. AndGuglielmo Marconi, who developedradio 100 years ago this year.

commentTHIS D-i-Y RADIO features twomen who have influenced the his-tory of radio. Firstly, Samuel Morsewhose famous code allows ama-teurs to communicate world-widewith very low power stations. Sec-ondly, Guglielmo Marconi, whotook the theoretical work ofHeinrich Hertz and the very short-range tests of Sir Oliver Lodge,and developed radio as the long-range service which we all nowtake for granted.

Marconi was first introduced tothe British government in 1896 byAlan Campbell -Swinton who be-came the RSGB's first President.Marconi was made an HonoraryMember of the RSGB in 1920. As'the first radio amateur', it is fittingthat amateurs will celebrate his100th birthday on 22 April. As partof International Day, RSGB Head-quarters will use the specialcallsign GB100IMD and, as 22April is also RSGB HQ Open Day,you can visit the station. Call us on01707 659015 for details.

For those of you wishing to learnMorse, the RSGB now has audiocassettes which take you in easystages up to 5WPM. The cassettesare available at £10.50 plus £1postage from the address on ourcover.

Finally, turn to page 23 whereyou can win one of several prizes,and get up to £4 off the admissionfee to one of the All Formats Com-puter Fairs.

Marcia Brimson, 2E1DAYRSGB Marketing

CONTENTS13 NEWSInternational Marconi Day.Radio and CommunicationDay at King's College Lon-don. Wanted: Young CrewMembers.

13 CONSTRUCTIONA SIMPLE CRYSTALSET

How to build the simplestradio without the need for an

expensive tuning capacitor.

6 CONSTRUCTION

A PSU VOLTAGEMONITORRobert Snary, G4OBE, de-scribes a circuit to monitorthe output of your 12V power

supply and give you an alarm

if the volts go high.

9 HAM FACTS

VARICAP ORTUNING DIODESAnother alternative to thetuning capacitor is the vari-able capacitance diode.

CONSTRUCTION CODEFOR THECOMPLETEBEGINNER

REQUIRESA LITTLEEXPERIENCE .

FOR THEMOREEXPERIENCED

10 THE WHATS, WHYS

AND WHEREFORES

NO ENTRY - ONEWAY STREET

John Case, GW4HWR,looks at how diodes work.

REVIEW

BOXING CLEVERWITH ALUMINIUMPut the finishing touch toyour latest project with these

smart metal boxes from JAB.

Ea POSTERAMATEUR RADIO &THE MORSE CODE

The Morse code was in-vented before the telephone

but is still in use today.

14 NEWS FEATURE

MY FIRST CONTEST

Olga Parker, 2E1ASV, de-scribes her first attempt at a

432MHz contest.

TECHNICAL

WHY USE MORSE?

Ian Poole, G3YWX, showswhy Morse is still used andis so popular with amateurs.

ON THE AIR

2's COMPANY/THE LOG BOOK/BAND BY BAND

Our regular columns for thelistener and the Novice. Plus

all about the 10MHz (30metre) amateur band.

16

18 TECHNICAL

ANOTHER LOOK ATTUNINGThe heart of any radio is thetuned circuit. Ken Smith,G3JIX, shows how it works.

CONSTRUCTION

A SIMPLETONEBURST

If you have a cheap VHFtransmitter, it may not havethe toneburst needed by VHF

and UHF repeaters. RobertSnary, G4OBE, describes asimple solution.

Ei LETTERS AND DIARY

Ea PUZZLE PAGE

Win the 300 -page Under-

standing Basic Electronicsin our Morse competition.

20

Special Event Station Radio Austria International

0E1141International Marconi Day, 22 April 1995

0 R F +

Managing Editor: Mike Dennison; Production Editor: Jennifer Preston; Technical Editor: Peter Dodd; Illustrator: Bob Ryan; Production Asst: Brione Meadows; News Ed: Steve Telenius-LoweD-i-Y RADIO is published six times a year by the Radio Society of Great Britain, Lambda House, Cranborne Road, Potters Bar, Herts. Filmset by JJ Typographics Ltd. Printed by Southernprint(Web Offset) Ltd. © Radio Society of Great Britain, 1995. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the RSGB. All reasonable precautions are taken by the Radio Society to ensure that the adviceand data given to our readers are reliable. We cannot however, guarantee it and we cannot accept legal responsibility for it. Prices quoted are those current as we go to press. ISSN No: 0959-843X.

2 D -I -Y RADIO January -February 1995

News

Radio AustriaInternationalCelebratesMarconi DayMARCONI ashortwave broadcasttransmitterfor Vatican Radioand 1,Nhen in February 1931it first went 1:)n the air, anexperimental transmitter inVienna re -broadcast theopening programme to thewhole of Europe. It was thefirst shortwave relaybroadcast irl the history ofradio.

To celebrate InternationalMarconi Day (IMD) on 22April, radio amateurs atRadio Austrwill operate tstation 0E1day' Radio

a Internationalie special eventA. On the sameAustria Inter-

national's broadcasts will

International MarconiDay 22 April 444144446

100 YEARSAGO this yearMarconi carriedout his first

successful transmissionsfrom his parents' villa nearBologna, Italy, over adistance of about 1 mile.

International Marconi Day(IMD) takes place each yearon the Saturday nearestMarconi's birthday and thisyear will be on 22 April. It willbe the 8th IMD and by far thebiggest yet, with over 40special event stationsaround the world expected

to be on the airduring the 24 hoursof 22 April, includingGB100IMD at theRSGB's HQ inHertfordshire.

IMD is organisedby the CornishRadio Amateur Club, whichis offering an award foranyone contacting orhearing at least 12 of thespecial event stations activeon the day. Note that loggingthe same station on adifferent band or mode willnot count; 12 different

callsigns must be contactedor heard.

To claim the award send afull extract of your log entriesto Sue Thomas, GOPGX,Cornish Radio Amateur ClubIMD Awards Manager, POBox 100, Truro, CornwallTR1 1RX. The cost is £3.50.

feature programmesdevoted to IMD, amateurradio and the special eventstation. A special QSL cardhas been printed which willbe used to confirm SWLreports on Radio AustriaInternational broadcasts on22April,aswellasfor0E1Mcontacts and reports - the

first such joint shortwavebroadcast and amateur radioQSL card. Radio AustriaInternational's broadcasts(which include programmesin English) can be heard on5.945, 6.155 and3.730MHz, among other

frequencies. The QSL cardis shown opposite.

Radio and Communication Day atKing's College London

KING'S COLLEGE LONDONis holding a 'Radio andCommunication Day' onFriday 24 March, startingat 10.00am. In addition tothe exhibition, there will bea series of presentationson the development ofradio from its beginningsand into the next century.Of course, there will bean RSGB stand, withrepresentatives availableto answer questions about

amateur radio and theNovice licence.

Following the present-ations, a plaque com-memorating the pioneeringwork of Sir EdwardAppleton will be unveiled.Appleton studied theionosphere and discoveredthat radio waves werereflected by a layer in theionosphere (which is nownamed after him) thuspaving the way for long-

distance short-wave radiocommunication.

Everybody is welcometo attend and admission isfree. The exhibition will beheld at King's CollegeStrand campus, locatednext to Somerset Houseand close to WaterlooBridge. The closest under-ground station is Temple.For further information callAnne Robinson on 0171873 2696.

Wanted: YoungCrew MembersIN DECEMBER two 72ftOcean Youth Club boats,James CookandJohn Laing,set sail on a voyage whichwill take them round theWorld, including stops in theCanary Islands, Caribbean,Tahiti, New Zealand,Australia, Africa and theAzores, returning to the UKin March 1997.

There are already twolicensed amateurs amongthe crew, who are mainlyyoung volunteers. If youwould like to take advantageof this rare opportunity towork as a trainee mate anddo some exciting 'maritimemobile' radio operation, writefor further information to:`Round the World Voyage',OYC Head Office, The BusStation, South St, GosportP012 1EP. Preference willbe given to those agedbetween 16 - 23.

irD -I- RADIO March -April 1995 3

IAN

S

Don't miss the LARGEST single day show in the U.K.

NORBRECKRadio, Electronics and Computing Exhibition

by the Northern Amateur Radio Societies Association at the

NORBRECK CASTLE HOTEL EXHIBITION CENTREQUEENS PROMENADE, NORTH SHORE, BLACKPOOL

extracar park

NorbreckHotel

Bispham

NorthShore

North Pier

Tower

Central Pier

South Pier

SouthShore

Cleveleys

0 1 2

Scale (miles)

Poulton-Le-Fylde

BLACKPOOL

A583

on Sunday, March 19th, 1995Doors open at 11 a.m.

* Over 100 trade stands* Bring & Buy stand* RSGB stand and book stall* Organised by over 50 clubs* Free car parking (plus free bus service from extra car park)* Overnight accommodation at reduced rates (contact hotel directly)

1N

SR

* Club stands* Amateur Computer stands* Construction competition* Facilities for the disabled

RADIO TALK -IN ON S22Admission £1.50 (OAP's £1, under 14's free) by exhibition plan

Exhibition Manager : Peter Denton, G6CGF, 0151-630-5790

BRITAIN'S BEST SELLING AMATEUR RADIO MAGAZINE

Regular features include: Novice Natter Reviews of the latest

equipment Transceiver and test

equipment construction Bits and Bytes - The

Computer In Your Shack Valve and Vintage Antenna Workshop Radio diary, competitions

and much more

pw publishing ltd.Arrowsmith Court, Station Approach,

Broadstone, Dorset B1118 8PWTel: 0202 859910 Fax: 0202 859950

Become a regular D-i- Y'er

Get D-i-Y Radio for the next year*PLUS

* An RSGB Map of WesternEurope (900mm wide and1200mm high)

* A plastic wallet so you cankeep your issues of D-i-YRadio Safe

* An RSGB pen and a badge

. . . all for the specialintroductory price of only £9!RSGB Members see RadCom for details of special offerOverseas Subscribers write for prices.Please let us know your age or the age of the person for whom youare buying D-i-Y Radio andwhere you saw this copy.

* D-bY Radio is published six times a year

Send cheques or postal orders, made payable to:

RSGB, Lambda House, Cranborne Road,lir Potters Bar, Herts, EN6 3JE.

D -I -Y RADIO March -April 1995

Construction Feature

of ditunin

Simple Crystal SetTHE RADIO des-cribed below gives apractical application

des (see page 10) and(see page 18).

CAPACITOR TUNINGNO MALLY TUNING (ad-just' g the resonant frequencyof th receiver tuned circuit tomatt the received transmissioniti

freq ency) is accomplished byvary' g the capacitance value.This is normally done using avaria le capacitor; unfortunatelythe ost of this component isquite high, in the region of £10for a new one.

B t tuning can also beachi ved by using a fixedcap citor and varying theinductance.

INDUCTIVE TUNINGA SIindusimpThisused

PLE WAY OF varying thetance is shown in thee crystal set, see Fig 1.ses awiper similar to that

in a wire -woundpotentiometer to vary theresison adrasoldand

ance. The receiver is madeooden 'breadboard', with

ing pins used to formred supports for the wiresomponents.

CO STRUCTIONAN I DUCTOR DOES not haveto b wound on a cylindricalformer. In this radio the coilformer is made from a sectionof 10mm x 70mm wood, 90mm

113001 In I

DI0A91

CI C2 RI-1Crystal

earphone

©RSGB DY172

Fig 1: rystal set, circuit diagram.

Wire connected tobrass drawing pin onunderside of wiper

Drawing pinto hold wirein place

To antenna

To crystalearpiece

ORSGB CW171

Enamelled wire woundon wooden former

RI

4C

DI

II I

Base board

Enamel insulationscraped off topsurf ace of coil

Wood screwand washerpivot

Wiper

Fig 2: Crystal set, component layout.

long. The coil is made using 10metres of 20SWG (0.9mm)enamelled covered wire.Unwind the wire from the rolland fix one end to a fence ortree. Fix the other end to adrawing pin on the wooden coilformer. Wind the coil by rotatingthe former, while at the sametime keeping the wire as tight aspossible.

The wiper is made from asection of 10mm x 10mm wood,100mm long. The contact to thecoil is made using a drawing -pin with a wire soldered to it.

The screw at the pivot of thewiper is tightened so that thedrawing pin at the end of thewiper is in good contact with thecoil but not too tight so that thewiper can be moved. Move thewiper from one side of the coil tothe other so that an arc shapedmark is left on the coil. With aknife or screwdriver carefullyscrape off the enamel insulationon the top face of each wire,5mm either side of the mark, sothat the wiper drawing pin willmake good contact with the coil(see Fig 2).

If the wires tend to move asthe wiper position is adjusted fixthe coil to the former withadhesive, outside the wipercontact area.

The components are con-nected up as shown in Fig 2.

USING THE SETCAPACITOR C1, shown as300pF, can be substituted forother values (anything between100 and 500pF) to obtain thetuning range for local AMbroadcast stations in your area.

Crystal setsrequire a fairlyhigh signalstrength. This canbe obtained byhaving a long wireantenna (as longand as high aspossible) and byearthing the set.The centralheating pipescan often providea good earthpoint for in-creasing thesignal strength.

An alternativeway of tuning aradio

COMPONENTSResistorsR1

CapacitorsClC2

470k

300pF (see text)1nF

SemiconductorsD1 0A91Additional Items10m of 20SWG enamel coveredwireAerial wireCrystal earpieceComponents are available from JABElectronics Components, 1180 AldridgeRoad, Great Barr, Birmingham B448PB.

RADIO March -April 1995 5


A PSU Voltage MonitorBy RobertSnary, G4OBE

Display board LEDconnections.

THISCIRCUIT ISdesigned tobe added to

any 12 volt power supplyunit and provide an LED(light emitting diode)bargraph display of thevoltage and if this exceeds14.4 volts then an audiblealarm will sound giving youan indication that there is aproblem.

A simple voltmeter couldbe used to monitor thevoltage but the cost of adedicated voltmeter wouldbe similar to the cost of thiscircuit. And the use of anLED barograph gives aninstant indication of lowvoltage (amber), correctvoltage (green) and highvoltage (red).

The circuit has been testedto make sure that radiotransmitters will not affect it.

Signals up to the full legallimit output on all bandsfrom 160m to 70cm wereused. No changes werenoticed, even with the uncasedboard.

The complete voltage monitor.

CIRCUITDESCRIPTIONTHE CIRCUIT USES three ICsand is shown in Fig 1.

101 is a 6 volt regulator whichis used to provide a stableregulated supply for the rest ofthe circuit.

IC2 is a LM3914 bargraphIC, which operates on aninput voltage of 0 to 1.2volts. The voltage isdisplayed on LEDs D1 -

D10, in 0.12V steps. The ICcan either be set to dotmode where only one LEDis on at a time or bargraphmode where all the LEDsup to the indicated level areon. The resistors R1 andR2 act as a potential(voltage) divider to ensurethat the 12 volt supply fromthe power supply is reducedto the 1.2 volts maximuminputvoltage to the IC. Whileresistor R3 controls thebrightness of the LEDs andR4 controls the step size.

IC3 is an Opto Isolatorwhich consists of a LEDand a phototransistor (a

transistor which is sensitive tolight) in the same package. Thisis used to switch the buzzer LS1on when the input voltage isgreater than 14.4V.

CONSTRUCTIONTHE CIRCUIT IS BUILT on two

0Out

'Cl

A

R2I 4 R3

1 18

2 17

3 16

15

5 14

6 13

7 12

8 11

9 10

DI D2 D3 D4 05 D6 D7 D8 D9 DIO

IC3

IC2LM3914

2

3

6

5

4

7806In

Sounder

Common

Inputo from

PSU

6

(DRSGB DY157

Fig 1: PSU monitor, circuit diagram.

13 -I -V RADIO March -April 1995


piec:circapiec25 his bu4 strirequiandmakiall tremavailbutusecutti

Theasi:LED(long'A'.theseandsize

s of Veroboard. The mainboard, see Fig 2, is a

of Veroboard 15 strips byles, while the display boardIt on a piece of Veroboards by 30 holes. Both boardse a number of track cutsare must be taken wheng the cuts to ensure thate unwanted copper isved. A special cutter isble for cutting the tracks3/8 inch drill bit can beas a hand-held track

g tool.display board is the

st to construct with all themounted with the anodest lead) connected to strip

he LEDs used are 3mm;are the smallest availableere chosen to keep thef the display board down.

The main board is morecornwirefirst,and tbesold:(IC1thendisplboaralsois pileadposi

lex and the Veropins andlinks should be insertedollowed by the IC socketse resistors. These shouldouble-checked beforering in the voltage regulator

. The inter -board wires cane connected between they board and the main

and the piezo buzzer cane connected. The buzzerlarity conscious: the redshould be soldered to theye supply and the black

Number ofBatteries

Voltage,Nicads

Voltage,Dry Cells

7 8.4 10.58 9.6 129 10.8 13.510 12 1511 13.212 14.413 15.6

Table 1: Test voltages available frombatteries in series.

lead to the negative supply rail.The two remaining ICs can thenbe put into their sockets butmake sure they are insertedround the right way. The boardcan then be double checked fordry joints and solder bridgesand the circuit is ready fortesting. The voltage regulatorshould have a small heatsinkfitted to improve heat dissipation(see photo).

TESTINGIF YOU HAVE ACCESS to avariable voltage power supply(PSU) then the testing is quitestraight forward. First set thevoltage to 10V output, connectthe power supply to the circuitand switch on, then graduallyincrease the voltage and checkthat the LEDs come on in steps.When the voltage exceedsapproximately 14.4V the firstred LED will light and the buzzerwill sound. If one of the LEDs

Note:Cut in copper track

+veat A3 not shown

supply 1 IC1 5

K

L

M

N

0P

Component side of board10 15 20 25

Ai o0 00000000000000B o o o o o o o o o o o o o 0 o o o oCo 0 Ooo 000 0 Oo 0 o 0 00000DO 000111 4-1/4-1-D1

°C1? °E o o 0 o 4 D 0 o)3F 000 0 116?°G 00 1.004 D0041,5H 004

D°DgD8'

11::13.70 `bg:

1.. .. 0 ii 0 0

R3l a

1C2

000000000000000000000000000000

0 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 00 0 0 0

0 0 0 00 0.0 0 0

11e0 0000000000 0000000000000000000

000 00000000000000000000 0

0 0 00000000000000041'00000000000000000000000000000

OV supply I l+ve supply = Pin

ORSGB D51513

L51+

Sounder

LS1

S- =Link= Cut in copper track

A3D9, E9, F9, G9, H9,19, J9, K9, L9015, E15, F15, G15, H15,115, K15, L15119, J15, K15

does not light then the usualproblems are either a LEDconnected the wrong way round,a dry joint or a break in the wirebetween the main and displayboards. If you find that the firstred LED comes on at too low avoltage then you can increasethe value of R1; if it comes on attoo high a voltage then you candecrease the value of R1.

If you do not have access to avariable voltage PSU, then thebest way to test the circuit is touse several batteries in series(connected end to end). Thevoltages available from such anarrangement are given inTable 1. Nicad batteries areeasier to use as they have a lowvoltage per battery and give amore controlled step size, buttake care because if they areshort-circuited a very largecurrent can flow.

Once the board has been builtand tested it can be fitted into acase. The circuit can bemounted in either a plastic ormetal box and connected to thepower supply output terminals.

COMPONENTS LISTResistorsAll resistors 0.6 Watt 1% toleranceR1 11k*R2 1k

R3 1.2kR4 18k* The value may need to be changed - see text for details.

SemiconductorsIC1 7806 6 volt voltage regulatorIC2 LM3914 Linear Bargraph DisplayIC3 Opto Isolator in 6 pin DIL PackLED 1,2,3 Orange 3mmLED 4,5,6,7 Green 3mmLED 8,9,10 Red 3mm

Additional ItemsLS1

6 pin DIL Socket18 pin DIL SocketVeroboard

Piezo Electric Buzzer Wire Ended(for 103)(for 102)(two pieces for Display Board andmain board - see text for sizes)

VeropinsHeatsink for 101Wire for LinksFlexible Wire for Interconnecting WireCase

Components are available from JAB Electronics Components,1180 Aldridge Road, Great Barr, Birmingham B44 8PB

Fig 2: PSU monitor, PCB layout.

D -I -V RADIO March -April 1995 7

.+01111111111

mom 1c -T211illoviGPWC61

gob wbolo ks WV

Every issue ofHam RadioToday fora wholeyear withour DirectDeliveryService.

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HITT is always up to date with your needsand interests as a novice or experiencedamateur radio user. Product reviews, construction, conversions,packet radio and club news pack NRT fromcover to coverThis Is Nam Radio - Today!U.K. and overseas subscription rates availableupon request, write to us or phone our hotline:0737 768611Argus Subscription Services,Subscription Dept., Queensway House,2 Queensway, Redhill, Surrey, Rill 1QS.

AN INTRODUCTION TO AMATEUR RADIO FOR BEGINNERS OF ALL AGES

£1.50 EachSPECIAL OFFER FOR SUBSCRIBERS

ONLY 50p per issue

RSGB, Lambda House, Cranborne Road,Potters Bar, Herts EN6 3JE.

ALUMINIUMBOXES OFFER

Use the coupon on page 23to obtain a 25% discount on the

one-off price of any aluminium boxfrom JAB (see page 11). Send to

D-i-Y Radio Offer Dept, JABElectronic Components, 1180

Aldridge Road, Great Barr,Birmingham B44 8PE

OFFER CLOSES

30 APRIL 1995

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73 from Dave G4KQH, Technical Manager.

8 RADIO March -April 1994

Ham Facts

Va!icap or Toiling DiodesTUNED CIRCUIT

iS made up of acapacitor and an

inductor, as described in 'Whatis Tuning' on page 18. If wewant a variable tuning circuitthen we usually need to use avariable capacitance. While thecost of most of the componentsto make a simple receiver isquite low the cost of the tuningcapacitor alone can be in theregion of £10.

Certain types of diode maybe used as electronic variablecapacitors. These are knownas Varicap, (Voltage VariableCapacitors)] or tuning diodes.You will also hear of themreferred to as varactor diodes.The Varicap diode uses thevoltage -variable capacitance ofthe PN junction (see page 10).

In the normal semiconductordiode efforts are made to reducethe capacitance of the PNjunction while in the Varicap

Fig 1: Tuning circuit using a single varicapdiode.

Fig 2: Tuning circuit using a double varicapdiode.

.

diode this capacitance isemphasized.

These diodes may be used inplace of mechanical tuningcapacitors in many circuits. Thisis of benefit if we wish to reducethe cost of a project and itpermits us to reduce the size ofthe equipment.

It is necessary to apply areverse voltage to the Varicapdiode in orderto make it work asa capacitor. Specifically, weapply a positive voltage td thediode cathode while the anodeis at negative volts, and oftenconnected to earth.

As the reverse voltage isvaried, normally using a

potentiometer (variable re-sistor), there is a change in thediode junction capacitance. Thegreater the applied voltage thesmaller the capacitancealthough there is very littlechange of capacitance below+2V.

Fig 1 shows how a singleVaricap diode can be used in areceiver input tuning circuit. Adouble Varicap diode, shown inFig 2, is more often used fortuning oscillator circuits.

Data sheets contain a curvewhich indicates the usefulcapacitance range of the diodeversus the applied voltage, seeFig 3. Most Varicap diodes havea fairly linear (straight)capacitance change over thetuning range. A typical voltagerange for a tuning diode is *1 to+12V DC. The tuning voltagemust be regulated, using anelectronic regulator such as a78L08, in order to preventcapacitance changes if there is

a small change in thesupply voltage.

Small signaldiodes, such as the1N914, may be usedas Varicap diodes.

Type

KV1236

BB609

Capacitance

450pF

42pF

Description

Dual AM tuning

Dual VHF tuning

Table 1: Two typical Varactor types.

Try electronictuning in yournext project.

Fig 3: Typical tuning characteristics of avaricap diode

Because the junction of thesediodes is small the capacitanceis low, but you can put severalof these diodes in parallel toincrease the capacitance.

Typical Varactors are shownin Table 1.

These components areavailable from suppliers suchas JAB Electronic Components,1180 Aldridge Road, Great Barr,Birmingham B44 8PB.

How to Passthe RAE

Clive Smith, G4FZH, and GeorgeBenbow, G3HB

Just the book to help you gain your fulllicence. Lots of information and tips onwhich areas of the syllabus toconcentrate on to guide you throughthe examination.

Price: £7.99 Plus £1 P&PRSGB Members, see latest RadCom for price

4 RSGB, Lambda House, Cranborne Road,IF Potters Bar, Herts EN6 3JE.

RADIO March -April 19959

The Whats, Whys, and Wherefores

No Entry - One Way StreetBy John,GW4HWR,

ChairmanRSGB Training& EducationCommittee

IN THE LASTCOLUMN I mentionedsemiconductors. Torecap: Pure, cryst-

alline Silicon is an insulator, thereare no current carriers (negative -electrons or positive - holes) presentto allow current to flow.

But by introducing a smallproportion of some other elementthings change.

THE ADDED EXTRAANTIMONY IS an atom very

similar to Silicon but has five outerelectrons (known as valencyelectrons) where as Silicon hasfour. The atom fits nicely into thecrystal structure and at the sametime releases one electron into thematerial. These electrons willmove if a voltage is applied - theSilicon has become an 'N' typesemi -conductor.

The same sort of thing happensif, instead of Antimony, Indiumatoms are introduced - not many,about one in every 1,000,000 Siliconatoms. Indium will also fit into thecrystal structure (lattice) but it hasonly three valency electrons. Thiscauses a hole (a place where anelectron should be but it is missing).Holes also turn Silicon into a semi-conductor (`P' type). When avoltage is applied it is the holesthat 'move'. Holes move in theopposite direction to electrons.

THE PN JUNCTIONIF PIECES OF 'N' type and `P' typeSilicon are brought together in aperfect junction, a PN junction isproduced. If a voltage is applied

as shown in Fig 1

+,

- Depletionregion

+ Holes - Electrons

®RSGB 0Y159

Fig 1: PN diode reversed biased.

the junction is saidto be reversedbiased. The 'free'electrons in the 'N'type will be repelledfrom the negative ofthe supply and atthesame time the holesin the 'P' type will berepelled from thepositive of thesupply. In the space

P

Recombinations

II©RSGB DY160

Fig 2: PN diode forward biased.

around the junction there will be nocurrent carriers -this region, knownas the depletion region, has beenturned into an insulator, and nocurrent will flow.

If the supply is connected asshown in Fig 2 the PN junction isnow said to be forward biased andthe result is quite different. Thenegative current carriers (electrons)in the 'N' type and the positivecurrent carriers (holes) in the `P'type both move towards thejunction. Now when an electronmeets a hole a 'recombination'takes place. In other words theelectron slips into the hole and botheffectively disappear, they haveagain become part of the crystallattice. It is easy to get rid of dustwhen sweeping the floor if there isa convenient hole to brush it into!The same sort of thing happens atthe junction of a PN junction whenit is forward biased. The currentcarriers move up to the junctionand disappear making it easier formore carriers to move up. Thedevice has become a conductorand its resistance rapidly gets loweras the voltage is increased. In factat a voltage of about one volt theresistance becomes so low that thecurrent rises to the point where thejunction melts.

The PN junction will allow currentto flow in one direction but not in theother - it is a rectifier, but not thesame as a point contact type whichis similar to the Gallena crystal andcat's whisker. The PN junction iscommonly used in power supplieswhere it helps in the conversionfrom AC to DC and many computer

type circuits when it acts as a switch.I said earlier that a perfect

junction between 'P' and 'N' typeswas required. If 'P' and 'N' typesare machined flat by the mostprecise machine tools, then broughttogether, the junction will not meetthis requirement. In order to producethe perfect junction required inpractice, the 'P' material is 'grown'on a piece of 'N' type by a processof diffusion. Fig 3a shows a pieceof 'N' type Silicon with a small pelletof Indium, placed on it, thetemperature is raised almost to themelting point of the Silicon andIndium and slowly the Indiumdiffuses into the Silicon. First thefree electrons are taken up by theholes in the Indium and then holesappear in the Silicon and the regionbecomes `P' type. The junction isthe boundary of the `P' type withinthe 'N' type Silicon. Fig 3b showsthe completed chip and the dottedline represents the junction. The'chip' is encased in a small glass (orsimilar) tube with leads coming fromeach end. The complete device,shown in Fig 4, measures about6mm in length and may be markedsomething like 1N4648. The nexttime you use one ofthese diodesperhaps it won't be such a mystery.

N typesilicon

(a)

Pellet ofIndium

Disc ofN type

Pes'iligt

N typesilicon

Junction Disc ofN type

(b)©RSGB 0,61

Fig 3: P and N materials before and afterdiffusion.

I 1N4648

©RSGB Dyne,

Fig 4: PN diode.

10 04-Y. RADIO March -April 1995

Equipment Review

Boxing Clever with AluminiumIN ORDER TOmake your elect-ronic constructionproject look like a

professional product, it isnecessary to put it in a box.Often the simplest type to use isplastic - a sandwich box, orsomething the Christmaschocolates came in - but a betterlook is obtained by using metal.Metal boxes also have the greatadvantage of protecting(screening) the circuit fromoutside radio interference, andfrom any accidental alterationsto its performance caused bythe capacitance of nearby handsor metal objects.

JAB Electronic Componentsmanufactures a range of metalboxes - made from 18SWG(SWG means Standard WireGauge)thick untreated plainaluminium - in a variety of sizesand shapes (see Table 1) andsupplied with fixing screws.These come in five types:

Flush Fit: A simple two partrectangular shape with slightlyrounded corners (seephotograph).

4mm Lipped End: Similar tothe flush fit, but with the lidoverhanging slightly at the backand front.

Sealed End: Similar to theflush fit but with an extra fold inthe top to give improved strengthand screening.

Sloping Front Lip: Thesetwo part boxes have a 15mm

overhang at the top of the frontpanel, with sloping sides (seephotograph). These make reallyattractive cabinets for receivers,transmitters and test equipment.

Free Plate: This box is madefrom three parts and issimilar tothe flushfit butwith aremov-ablerear panelsecured by two screws.

Each box is covered in aneasily removed plastic film toprotect it from scratches. Notethat some of the edges of thesawn metal can be a little sharpso care is needed in unwrappingthe boxes, and any roughnessneeds to be filed off straightaway to remove any hazard.Fixing screws are provided forthe lid and any detabhablepanels.

Aluminium is light and veryeasy to saw and drill, usinginexpensive tools. Care must,of course, be taken with any`metal - bashing' job and anyonetackling this work for the firsttime should seek the assistanceof someone more experienced.

JAB's aluminium boxesprovide a cheap and easy wayof tidying up your home builtequipment. There is a wideenough range to suit most needsand it may be useful to keep asmall selection on hand just in

case you need abox in a hurry.The prices rangefrom £1.20 forthe JA6 to £7.70for the AL378,with most beingbetween twoand four pounds.Discounts areavailable if youbuy ten or more

of one box. AndJAB can make boxes to yourown specification, too.

Full details of these and othertypes of box, plus a wide rangeof components, can be obtainedfrom JAB ElectronicComponents, The IndustrialEstate, Rear of QueslettMotors, 1180 Aldridge Road,Great Barr, Birmingham B448PB.

Putting theFinishingTouch to yourHome MadeRadio.

Turn to Page 8for how to get

25% OFFthese boxes

Part No

Flush Fit Tops:BOX-JA6

BOX-JA10

BOX-JA24

BOX-JA42

BOX-JA20

BOX-JA25

BOX-JA43

BOX-JA67

BOX-JA48

BOX-JA34

BOX-JA36

BOX-JA46

4mm Lipped End:BOX-AL55

BOX-AL43

BOX-AL378

Sealed End:BOX-SA92

BOX-SA57

Sloping Front Lip:BOX-JS5

BOX-JS8

BOX-JS47

BOX-JS58

BOX-JS67

Free Plate Box:BOX-JP56

Width x Depth x Height

57 x 75 x 26mm

57 x 127 x 26mm

67 x 110 x 31mm

55 x 112 x 38mm

76 x 114 x 38mm

76 x 140x 38mm

103mm x 74 x 42mm

150 x 180 x 50mm

102 x 152 x 51mm

79 x 100 x 58mm

79 x 150 x 58mm

110 x 160 x 80mm

139 x 145 x 44mm

103 x 74 x 52mm

225 x 170 x 90mm

64 x 225 x 64mm

170 x 120 x 70mm

153 x 76 x 64mm

204 x 102 x 64mm

100 x 170 x 75mm

200 x 130 x 50mm

174 x 154 x 60mm

117 x 163 x 30mm

Price

£1.20

£1.55

£1.70

£2.30

£1.80

£2.10

£2.30

£4.25

£2.55

£2.25

£2.95

£3.40

£3.45

£2.65

£7.70

POAPOA

£3.20

£3.95

£4.20

£5.95

£5.20

£4.90

Table 1: JAB's range of aluminium boxes.

D -I -Y RADIO March -April 1995 11

Amateur Rai to

SamuelMorse

An original pump key. The classic Vibroplex bug key.

1=1 0000 0 1=I= =I= 01=0 000 0 1=000 ooTWO HUNDRED YEARS ago Samuel Morse wasborn in Massachusetts, USA. He gave his name tothe dot -dash code which has been widely used inradio communications for many years. Althoughradio was not used until after his death, his codewas transmitted along wires, often providing theonly link between remote settlements.

Samuel Morse sending the .first public telegram in 1844 before an audience of VIPs.

0

0

0 MORSE KEYS HAVE been made in a number of shapes.An early design, still widely used today, is shown topleft; this is known as a 'pump' key because of the pump-ing action used when sending Morse. Because it can be

O difficult to send rapid dots, several methods have been

The Morse Code

Paddle key for an electronic keyer.

LI

Keys: Pumps, Bugs& Computers

invented to send the dots automatically. The best knownO mechanical automatic key - bug key - is the Vibroplex

which is still an excellent key despite being designed 50years ago. Nowadays, automatic Morse uses electronicsto produce perfectly timed dots and dashes. Morse canalso be read and displayed automatically by a computer-ised decoder. And if you have a computer, there are pro-grams which can send and receive Morse, as well as help

O you practice. Despite modern technology, there's still lotsO of fun to be had sending Morse 'by hand' and using your00

O ears and brain to decode it.

0

0

0

0

0=I 0000 0 oo .-u-tr-g 0=0 000 0

g THE STANDARD 'PUMP' key: it rests0 on a heavy base made of wcod,

metal or even marble. All of the mov-ing parts are metal, often brass, andthe knob and flange are made of aninsulating material such as ebonite orplastic. The contacts are made froma metal which will not tarnish easily,for instance platinum. There are al-ways two adjustments: the spring ten-sion which affects how hard it is topress the key down, and the back-stop which alters the gap betweenthe contacts.

An automatic Morse wader.

A computer can send and

receive Morse code, and

programs are availablewhich can help you to

practice the code.

Cap ) r

-TY J._

'f_DI'DMCM=JCDOCD,C3, ,.. 0 r

MORSE LETTERSA

B

CDE

FGH

K

M

di-dahdah-di-di-ditdah-di-dah-ditdah-di-ditditdi-di-dah-ditdah-dah-ditdi-di-di-ditdi-ditdi-dah-dah-dahdah-di-dahdi-dah-di-ditdah-dah

N dah-ditO dah-dah-dahP di-dah-dah-ditQ dah-dah-di-dahR di-dah-ditS di-di-ditT dahU di-di-dah

di-di-di-dahW di-dah-dahX dah-di-di-dahY dah-di-dah-dahZ dah-dah-di-dit

MORSE NUMBERS1 di-dah-dah-dah-dah2 di-di-dah-dah-dah3 di-di-di-dah-dah4 di-di-di-di-dah5 cli-dt-di-di-dit6 dah-di-di-di-dit7 dah-dah-di-di-dit8 dah-dah-dah-di-dit9 dah-dah-dah-dah-dit0 dah-dah-dah-dah-dah

ENDINGS IN MORSEPhrasesTransmissionContact

dah-di-di-di-dahdi-dah-di-dah-ditdi-di-di-dah-di-dah

0=0 000 0 =0=0 ==

LEARNING THE CODETHE RSGB PRODUCES a book whichguides you through the stages of learn-ing Morse and passing the test. It is

called Morse Code for Radio Amateursand costs L3.99 plus £1 postage fromRSGB Sales at the address shown atthe foot of this page.

Regular Morse Practice broadcasts takeplace on the 160, 80 and 2 metre bandsusing the special callsign GB2CW; check1.976, 3.55 or 145.250MHz during theevening.Computerised

Morse practice setsare available fromWaters & Stanton(tel: 01702 206835).A program for thePC, Archimedes orBBC computer canbe bought fromP Brandon (tel:01244 683563).

Kip - -1( RSGB, Lambda House, Cranborne Road, Potters Bar, Herts. EN6 3JE

Operating Feature

My First Contest

Final stages ofassembling the 2m(144MHz) antennas.

Turn to page 22 forcontests in March

and April 1995

THE 144 / 432MHZcontest on 5 / 6

March 1994 was myfirst contest - a 24 -hour stint! I

arrived early at the NorthWakefield Radio Club site, in awindswept field overlooking thePennines in Yorkshire. The70cm (432MHz) antennas werelaid out on the ground, ready forerection. What a performancethat was - heaving on guy ropesto keep the top-heavy swayingmast upright while thepneumatics pushed up eachsection. There was a problemwith the last section whichcaused the top section to dropdown a stage. The mast for the2m (144MHz) antennas was ofa different design, being a crank -up tilt -over tower mounted on atrailer, and this proved to bemuch easier to erect.

The radios were set up in twocaravans, the 70cm stationbeing in a van kindly loaned tous by a neighbouring radioclub. By 1400 we were all setand ready to start calling "CQ,CQ, CQ". I was so excited!

ALL QUIET ON THEWESTERN FRONTWHAT WAS WRONG? I hadexpected a cacophony ofvoices, but all was silent. Did wehave a fault in our system? No,

it was just that everyone elsewas much more relaxed in viewof the time scale we wereworking to. By 1430 we hadmade a couple of contacts, andso it went, very, very slowly.

OPERATINGTACTICSI WATCHED the differenttechniques of the operators.Some rotated the antenna,some spun the dials. Oneclaimed it was statistically betterto stay on one frequency. Idid wonder what wouldhappen if everyonefollowed that theory!

In the evening the callscame a little quicker,although the 2m stationwas much more lively than70cm. In the depth of thenight I got my turn andcalled for more than 30minutes before I made acontact. Then I panicked!My brain went to jelly and Iforgot what to say.Fortunately my contactwas experienced atcontests and helped methrough. I was much moreproficient for the next one.Sadly by this time everyonehad gone to sleep, so theradio was silent. I watchedthe dawn and drank tea

while the occasional call camethrough.

At 0800 the radio really camealive again - there was a six -hour contest running at the sametime as ours. The experts tookover.

TOTTING UPA FEW MINUTES before theend of the contest we developedan electrical fault and had tostop. We totted up the contacts,feeling quite pleased with thosewe had made to the continent,as they would earn us extrapoints.

Lowering the antenna wastraumatic: it was a hard-hat area,but in the end no damage wassustained. In all, I thoroughlyenjoyed the experience, and asa female, pensioner, Novice I

can't wait for my next contest![The next RSGB 432MHz

contest is on 6 / 7 May and therules were published in theMarch edition of RadioCommunication - Ed]

The antennas up in the air- left: 144MHzon trailertower, right: 432MHz on pneumatic mast.

14 D -I -Y RADIO March -April 1995

i Technical Feature

by Use Morse?MORSE CODE wasthe first way in whichmessages were

trahsmitted over radio. Beforethat the Morse Code was usedonwiofco(b

telegraph systems usinges and it was the first meanselectronic communication to;e into widespread use

re the telephone). The firstsystem was set up betweenWashington and Baltimore inthe USA in 1843.

Since these early pioneeringdys of communication,te Mnology has made someenormous advances: in 1904the first valve was invented,transistors were invented in1949, and in the early 1960sthey came into common use,only to be superseded in manyareas by integrated circuits.

WIDESPREAD USENOW COMPUTERS AREcc mmonplace and they canperform tasks which people likeSamuel Morse and many otherearly inventors would not havethought possible.

'Despite these advances theuse of Morse as a means ofc mmunication is still wide -s read and there is little sign ofit use coming to an end. Withsci much technology availabletoday it might seem a littlestrange that the first means ofel ctronic communication canst II compete with systems usingth very latest in technologya d processing power.H wever, it must have somea vantages otherwise it wouldn t be used.

IMPLICITYHAT ARE THE advantages

01# Morse? Despite what manypeople think, the Morse codestill has many advantages to

offer. The first is obvious - its

simplicity. All that is needed is ameans of turning a radiotransmission on and off. Thiscan be accomplished quitesimply on most transmitters.Radio amateurs who constructtheir own equipment find thisparticularly attractive.

If the transmitter is to be usedonly for Morse then it can bemade quite simple. There areseveral designs for Morse -onlytransmitters which use only twoor three transistors and arecapable of making contacts overdistances of hundreds orthousands of miles.

Simplicity is not the onlyadvantage of Morse. Anotherimportant reason for its use isthat it occupies very littlebandwidth or spectrum space.This is a great advantage withtoday's crowded bandconditions, because it meansthat more stations can occupy agiven band. Another advantageis that narrow receiver filterscan be used to cut out anyinterference.

NARROWBANDWIDTHIT IS ALSO FOUND thata Morse signal can beread when it is weakerthan any other form ofsignal. There are anumber of reasons forthis. One is because filterbandwidths can be madevery narrow. This meansthat less backgroundnoise is detected and thewanted signal can beheard more easily. If

other forms of trans-mission were used thenwider filter bandwidthswould be needed andthis would increase the

level of background noise whichmight mask the signal.

Apart from this the simplicityof Morse means that it is onlynecessary to detect whether thesignal is on or off and the humanbrain can do this quite easily. Aspeech waveform is far morecomplicated and under thesame levels of noise it cannotbe copied (understood) so well.

ENJOYABLEALL THESE REASONS meanthat a Morse signal can becopied perfectly well when otherforms of transmission can barelybe detected, let aloneunderstood. Finally, manypeople actually enjoy usingMorse. This is particularlyobvious where radio amateursare concerned. They find thatthey can make contacts usingMorse with a low -power stationand a poor aerial but if they hadused SSB or FM they may notbe able to do so.

Many people also find thatMorse gives more satisfactionthan other modes. What betterreason can there be for usingMorse?

By Ian Poole,G3YW)(

See D -I -Y Radio Vol

2: Nos 3 and 4 for aprogram to practice

Morse using a D(Spectrum computer

D-14' RADIO March -April 199515

CD - On The Air

2's CompanyNews and Reports from Novice Licensees

AT THE ANNUALDinner of the NorthFerriby United

Amateur Radio Society (in NorthHumberside) a special cert-ificate was awarded to MichaelHindley, 2EOAHY, for becomingthe club's first Novice licence

holder. Michael,who is nine,passed the fivewords -per -minute (WPM)Morse testwhen he wasaged only sevenand enjoysusing CW on theHF bandsencouraged byhis fatherwhosecallsign isG4VHM. Theclub meets at8pm on Fridayevenings so ifyou are in thearea why notcall the Chair -

PHOTOGRAPH: DEM

Mi hael, 2E0AHY, proudly displays hisce ificate from the North Ferriby UnitedA ateur Radio Society.

man Frank Lee, G3YCC, on01482650410 to arrange a visit.

Another club award has goneto an old friend of D-i-Y Radio,Margaret Snary, 2E1AQS, whowon the G6QM Novice Trophyat the Southgate Amateur RadioClub (North London). The trophywas for constructing an HFreceiver, described by the clubnewsletter Bandspread as"extremely neat". The SouthgateARC meets on the second andfourth Thursday of each monthand their Publicity Officer isBrian Shelton, GOMEE,telephone: 0181 360 2453.

TEENAGE PACKETBEECHLOG, THE NEWS-LETTER of the BurnhamBeeches Radio Club (Slough/Windsor area) mentions aproject being set up by JamesPreece, 2E1AVX. He would liketo form a club - the TeenagePacket Amateur Radio Club - ofyoungsters interested in packet

radio (computer to computercommunications over the air). Ifyou're on packet, address anycomments to 2E1AVX@GB7XDD, or write to him at 8Gregory Rd, Hedgerley, BerksSL2 3XL.

ON AIR NIGHTFATHER AND SON Paul,2E1D0J, and Marc, 2E1DNM,took advantage last Decemberof an offer by their Instructor(Robert Snary, G4OBE) to usehis North London shack so thatthey could make their firstcontacts. Using the local UHFrepeater, GB3LV, they workedAlex, 2E1DBP; Marie,2E1DMG; Bill, 2E1DNR andTony 2E1BRE, many of whomhad been trained by Robert.Another interesting contact wasNorman, G3GUL, who helpsRobert with the course. Marc'sinterest in amateur radio cameabout as a result of visiting theRSGB stand at LIVE 93.

THE WINTER MONTHS are always good

for contacts on the lower HF bands (1.8, 3.5

and 7MHz) and conditions during the CQWorldwide 160m CW Contest provedexcellent. 83 countries were reported tohave been worked on 1.8MHz from the UK,

including Alaska and West Malaysia. In

addition, UK stations had contacts with 43

US states and Canadian provinces.

But the higher bands have also beenlively from time to time with even 28MHzproviding the odd opening, especially to the

South.

The VHF amateur bands have been quiet,

which is not unusual for this time of year. A

THE LOG BOOKreport from Eileen Mainwaring, 2W1BPS,

speaks of the difficulty of convincing anItalian station that '2W' was a genuine prefix,

so a good (presumably 50MHz) contact

FRANCE

a7"

firdif

F SW / P21 : s ..i.t.t E.2a;,,,...

2...t. ---A 2 - PA.....4. -1,,

5YJJacques CARRIER

Avenue Jules -Joey, 35- AULNAY-SOUS-8015

REF 19051

QSLs are often comical as this French ...

was lost. The Wolverhampton two -metrerepeater, GB3BX, is now on a new channel,

R3, which has its output on 145.675MHz. If

you have 6m and you live in the South -East,

G3MEH puts out a good signal reading the

RSGB's GB2RS News Bulletin at 1200 onSundays, on 51.53MHz. He listens for calls

afterwards.

On the 10GHz band, VK5NY (nearAdelaide, South Auatral la) has workedVK5KZ/VK6 (Albany, Western Australia) over

a record -breaking distance of 1,912km. And

Danish amateurs OZ9ZI and OZ1UM have

broken the World record at the amazingfrequency of 145GHz (that's 145 thousand


# Imo - -yv On The Air

Band by BandThe Amateur Radio Spectrum: The 30 metre Band

THIRTY METRES,10.1MHz, is one ofthe so-called WARC

bands named after the 1979World Administrative RadioConference where three newamateur bands were created:10.1, 18.1 and 24.9MHz. Nocontests take place on theWARC bands so if you're one ofthose who don't like the suddenhuge increase in hectic activityproduced by a contest, theseband are for you.

Thirty is the only amateurband where telephony (speech)contacts should not take place.The reason is that the band isallocated to amateurs on aSecondary basis (ie nointerference should be causedto the commercial users of theband). The IARU, which co-ordinates amateur radioworldwide, has agreed that onlynarrow bandwidth modes suchas CW and AMTOR should beused. Novices may only useOW (Morse).

(a)

(b) R 3G0 0V173

Fig 1: Simple aerials work well at 10.1MHz.

Most transistor radios withShort Wave cover this band andCW can be received by addinga simple Beat FrequencyOscillator (BFO) such as theone described in D-i-Y RadioVol 2: No2. Or you can build areceiver from a kit supplied byone of the D-i-Y Radio

advertisers. Simple CWtransmitter kits are alsoavailable.

Wire aerials are simple tobuild and are very effectiveat this frequency. A dipole isabout 14.1 metres long, and avertical and each of its radialsshould be 7.05m long. SeeFig 1 and the poster in Vol 5:No 1.

You will find the band opento Europe during the daytimeand to the rest of the worldafter dark. For Novices, thethirty metre band provides thebest opportunity for longdistance contacts all yearround.

BAND FACTS

Allocation: (Full A Licence) 10.10 -

10.15MHz; (Novice) 10.13 -

10.14MHz. Activity: CW 10.10 -10.14; Data 10.14 - 10.15MHz.Note that unattended stationsshould not use the band.

Megahertz) over a distance of 11km. The

145GHz band is the second -highestavailable to amateurs. The highest is at

248-250GHz.

HF DX reported in December, January

and February included: 1.8MHz - A71CW

(Qatar), EX8W (Kirghizstan), JA5BJC(Japan), P491 (Aruba); 3.5MHz - J87C0

(St Vincent), 4K8F (Azerbaijan); 7MHz -

ZP6CW (Paraguay), J75A (Dominica);10MHz - ZL3SF (New Zealand); 14MHz -

Y19CW (Iraq); 18MHz -UF6AM (Georgia);

21MHz -TU4SR (Ivory Coast); and 24MHz

- UA1QV (Russia).

The coming Spring will see a return

THE LOG BOOKto good HF conditions, particularly over

North -South paths - Spring and Autumn

are best for hearing Australia / New

Zealand, for instance. The improvedweather should lead to increasing portable

... and this American one show.

activity on the VHF, UHF and Microwave

Bands.

The CO WPX SSB Contest takes placeover the 48 -hours of 25/26 March and is all

about working as many different callsign

prefixes as possible. You'll find someextraordinary callsigns in use and a useful

guide to their whereabouts is the RSGB Call

Bookif you have one. Orthere's a brand new

publication, The RSGB Prefix Guide which

gives the very latest prefixes in use by special

stations and new countries. The RSGB Call

Book costs £10 plus £1 P&P, or the RSGB

Prefix Guide costs just £4.75 post free, from

the RSGB - see address on our cover.

D -/-Y RADIO March -April 199517

Technical Feature

nother Look at TuningBy Ken Smith,G3JIX

YOU WOULDTHINK 'tuning -in'was somethingexclusively to do

with operating a radio, but theidea came much earlier thanthat.

SOUND WAVESMUSIC GAVE RISE to themeaning of tuning. Musicalinstruments need careful tuningto pitch and special forks havealways been used to set thenotes. You can see in museums,beautiful sets of tuning forkswith C, C#, D etc, written onthem.

Pitch in music equalsfrequency. Each note codedC, C# and so on, has its exactcharacteristic frequency.

Your ear has a sensitivity overthe range of pitch of audiblesounds, similar to that showngraphically in Fig 1. Thus forgreatest sensitivity in receiving,for example, CW Morse signalsyou would set the Beat Oscillatorin the receiver to give a note ataround 1 to 3kHz. Yoursubjective 'feel' for a particularnote that you find comfortable,is the usual reason for whereyou set the BFO. I've foundmost people choose a frequencyaround the optimum.

A coil connected across a capacitor as shown here, oscillates at a setfrequency, according to the size of the L and the C.

RESONANCETUNING IS closelyconnected withresonance. Forsimple purposes, youcan assume thesemean the same thing.But all I've done, isshifted your questionto: "Well, what is res-onance?"

Often, most of usfirst meet resonancethrough mechanicaleffects. As smallchildren, we see aclock pendulumswinging - or our-selves swinging in the park.Then if we carry a cup of tea formum, the tea soon starts see-sawing in sympathy with ourwalking - and slops over into thesaucer. Then we notice the carvibrating or juddering when theengine revs up to a certain pitch.We call all these thingsresonances. You could saywhen the frequency coming inreaches the natural tuning, alarge vibration occurs. We seethis in all resonant systems.

CAPACITORS ANDINDUCTORSTHESE EFFECTS all arise inelectrical devices and circuitsas well. Sir Oliver Lodge (whoalso became one of the firstRSGB Presidents), realisedresonance would take place ifcapacitors (he used LeydenJars!) were connected acrossan inductance coil. He calledthis effect syntonyand Marconiand other wireless telegraphymanufacturers had to payroyalties to use it. Later, Marconibought the patent rights.

So why does a capacitor withan inductor 'tune'?

One of the best ways you can

140

130 -

120 -110-100 -

90 -60 -70 -60 -Militon times

50 -40 -30 - moo times it

20 -100 times

10 -10 times

0

1 1 1 1 11111 1 1 1 1 11111 I

100Hz 'kHz

ORSG13 001 64

I I WU10kHz

Fig 1: The way our ears work shows that we find very lowand very high frequency sounds inaudible. the mostsensitive pitch occurs around 1 to 4kHz. Notice thestrength of a sound at the 'threshold of hearing' has tobe about a million times bigger at 30Hz than at 1kHz.

understand this and bescientifically accurate into thebargain, is to see that resonanceor tuning involves an oscillationof energy back and forth.

Aha, you say, here we go,energy might be as abstract anidea as the one we are trying toexplain. True, but for now all weneed is the idea of Kineticenergy, like that in a rotatingflywheel or in a pendulumwhizzing through the bottom ofits swing; and that of storedPotential energy, like that in astretched spring or in a

pendulum stopped for an instantat the top of its swing.

You probably already knowthat both capacitors andinductors store electricalenergy. A charged capacitorstores electrical potentialenergy. The static voltageacross its terminals is a measureof this. Inductors store electricalkinetic energy by virtue of thecurrent flowing through them.This means that when youconnect a charged capacitoracross an inductor, like thecircuit shown in the photo, it

discharges its potential energyinto the inductor where theenergy appears as kinetic. This

18 D -I -Y RADIO March -April 1995

#1:30 -1- Technical Feature

energy then goes back into thecapacitor, charging it again -but in the reverse direction, andso on. The energy oscillatesback and forth at a characteristicrate called the resonantfrequency. The coil andcapacitor together form thefamiliar tuned circuit.

I imagine readers alreadyknow that capacitors have asize unit called a Farad andinductors have one called aHenry - or do you? Well, let'ssay you know it now. But unitsaren't much use unless we canuse them. Units? Ah yes, thatmeans quantities and quantitiesmean calculations . . .

FREQUENCYCALCULATIONSNOW FOR SOME REASON,calculating things is an activitythat's not very popular, (I wonderwhy?) Yet let's have a go.

The frequency of a coil andcapacitorforming a tuned circuitdepends on the size of both thecapacitor (in Farads) and thecoil (in Henries). The formulawhich relates the resonantfrequency - which we will labelwith the symbol fr in Hz, and theinductor L (Henries) and C(Farads) is:

fr 2n LCThe fr is the number of Hertz

(which as we noted is the

1

frequency). The little r is there toremind us of resonant. Thepeculiar number it (pi, about3.142) comes from theproperties of circles. The L andC multiplied together produce anumber inside the square rootsign (0l) which is underneath thedivision bar . This meansthat as either or both L and C getsmaller, fr gets larger or as wesay, higher.

The units of Henrys andFarads are far too large fortuning circuits for radiofrequencies. It is far morecommon to use the microhenry(symbol 1.1H) and the picofarad(symbol pF) for inductors andcapacitors at radio frequencies.(A micro = millionth part and apico is million millionth part).The frequency is usually givenin Megahertz (symbol MHz). (Amega = a million).

Now while all this might seemrather complicated it leads to asimplification of the way theresonance formula is used. Theformula is slightly modified sothat it can be used with the unitsjust described:

f =1000

2n LC

L = C = pF; fr= MHz.

Using this formula, what isthe resonant frequency of a 75microhenry coil in parallel with a100 picofarad capacitor?

Putting the numbers into ourformula:

O00

00an=000000

000:CIO

i__/Receivers

°O.0 0Aerial tuners

ORSGB DYII35

OI.1

0=MI0

000ci:70

0 COO 0====0=1=1=1

0 0c,..,===,...Ei.,-ia o o

Transceivers

/-7`

Dip oscillatorsand absorption meters

fr =1000

6.283xV75 x100

Giving a resonant frequency1.84MHz, which is in theamateur Top Band frequencyallocation. This simplifiedformula allows us to make thecalculation without having tokeep track of the millionths andthe millions.

The most practical use ofmaking resonance calculationsis to ensure that the resonantfrequency of the circuit youindend to build is close to thefrequency you indend to use. Inpractice there will be a smallchange in the frequency of thetuned circuit when it isconnected into a projectbecause of the capacitancesand inductances of the circuitsexternal to the tuned circuit.

ELECTRICALOSCILLATIONSTHE ELECTRICAL oscil-lations that go back and forthat the resonant rate whensomething has started them upin the coil and capacitorconnected together, graduallydie away because of theresistance in the wire. Theremight also be a radiation awayof some of the energy, as radiowaves. The job of the transistorin, say, a transmitter oscillator ,or in a receiver local oscillator,is to maintain the level ofoscillations constant at thefrequency set by the tuning. Itdoes this by giving the circuit alittle 'kick' - rather like howsomeone gives a child on aswing a little 'push' - at the rightmoment.

So you see tuning is used inmany radio applications, seeFig 3. So next time you listen toa signal, imagine the oscillatingelectric charge going back andforth in the transmitter L and Ccircuits, radiating off the aerialand setting up sympathetic

Fig 2: Tuning forms the basis of nearly all radio equipment, commercial, home-made, oscillations in your receivingradios themselves, or test instruments. antenna.



Simple ToneburstBy RobertSnary, G4OBE

IN THE UK ANDACROSS Europethere are manyrepeaters which

are primarily intended toimprove the range of mobileoperators. On 70cm FM theyalso tend to act as centres ofactivity where Novices are quiteoften assured of a contact.These repeaters need anaccess tone to switch the

Si(see Fig 3)

0-0+12Von Tx

Fig 1: Toneburst module, circuit diagram.

transmitterfrom standbybefore use; this can be either aCTCSS tone (for more detailssee the RSGB Call Book) or asingle frequency tone burst.

The toneburst was the firstmethod used and is still fitted toall UK repeaters. The tone,which is at the start of thetransmission, is a frequency of1750Hz lasting for about 0.5seconds. Most commercial setscome with a toneburst circuitfitted but if you are using an ex-PMR set which has beenconverted for the amateurbands, then this facility is notusually available.

CIRCUITDESCRIPTIONTHE CIRCUIT IS shown inFig 1. The tone is generatedfrom a ceramic resonator(XL1) which is used to provide

the frequencycontrol element in an oscillator,the output from the oscillator isdivided by 256 to generate the1750Hz tone.

The IC (integrated circuit)which is used contains both theoscillator and the dividers. Theceramic resonator is actuallydesigned to operate at 455kHzbut in this circuit we want it tooscillate at 448kHz (1750Hz x256) so the two capacitors C1and C2 and resistor R1 are usedto pull the resonant frequencyto the value we need. In ordertoget the tone to last for the 0.5seconds thatwe need, capacitorC3 and resistor R2 are used tocontrol the reset pin. This isheld low until the capacitor ischarged sufficiently to force theIC to reset and the output isstopped. When the supplyvoltage to the toneburst isswitched off, diode D1 dis-charges the capacitor (viaresistor R3) ready for the circuit

20RADIO March -April 1995


to be used again.The output of

the IC is taken viathe variableresistor (RV1)and capacitor C4to the microphoneconnection of thetransmitter. RV1is used to controlthe level of signalfed into the trans-mitter and shouldbe adjusted sothat the outputfrom the tone -burst is notdistorted.

Component side of board1 5 10 15 20

A

B00000000C0000000D

E

F

0 0 0 0

0 o o 4o 0 o 40 0 0 1

0 0 0 0 0 0 0oo(Dp000oo

C4)000000000o0

Oak

01V

0 0 0 0

ooooo0 00 0

0 0 0 0 0

00000000

= Veropin-- =Link

= Cut in coppertrack D5 E5F5, G5, H5,15,J5,,

F9, B13K5

K8

GoooH

1

J

K

4

o o 0 40 0 0 40 0 0 4oo 4

0 00 0

0

R1

0 00 0

0

-BOO0

0

iliolj

0 0Om00000 0

0 0 0 0

CC 0 0 0 000000 0 0000o

LooMooN

0000000100000000

00000000000000000000

ooo oo0000o

©Mai DY166

Fig 2: Veroboard component layout.

ClNSTRUCTIONTHE CIRCUIT IS VERYconventional in its layout andis built on Veroboard forsimplicity (Fig 2). The first stepis to make all the track cutsas shown in the diagram andthen to solder in the IC socket,wirelinks and the three Veropins.Once this is done you cansolider in the resistors,capacitors and the diode,making sure that you solder indidde D1 and capacitor C3 thecorrect way round.

The final component to besoldered is the ceramicresonator which should besoldered in quickly to prevent

CRSGB DY168

(a)

(b)

+veon Tx0-0

SP ST

Output tomic connector

Push tomake

Outputto micconnector

9V PP3battery

Fig 3: Toneburst module: Two alternativeswitching arrangements.

any heat damage. Once this isdone then you should check theboard for any dry joints andsolder bridges or splashes and,once satisfied that all is correct,you can insert IC1 into the ICholder.

TESTINGTHE VARIABLE RESISTORshould be set to half way andthe output connected to either asensitive earpiece or anamplifier (the Novice Audio Ampis ideal for this) and powerapplied to the circuit. You shouldhear atone which lasts for about0.5 seconds. If there is no tonethen the most commonproblems will be either diode D1soldered in the wrong way roundor a dry joint; if the tone iscontinuous then there may be adry joint affecting either pin 12of IC1 or resistor R2.

Once you are satisfied thatthe tone burst is working youneed to connect the supply leadto a point which is positivewhen the set is transmitting.The toneburst is only requiredwith repeaters and switch S1(toggle switch) disables it whenit is not needed (see Fig 3a). Ifyou do not want to modifyyour set then you can connectthe supply to a 9 volt batteryand just have a Push to Makeswitch that you press whenyou require the toneburst (seeFig 3b).

The output ofthe tone burstcircuit goes to themicrophone lead(in parallel withthe microphone)and the 0 voltconnection(battery or supplynegative lead)goes to a con-venient earthconnection. Inorder to adjustthe variableresistor youshould either

monitor your transmit signal withanother receiver and adjust thevariable resistor for anundistorted tone, or asksomeone else to check foryou.You will not be popular ifyou set up the tone whiletransmitting on the frequency ofyour local repeater. The toneonly lasts 0.5 seconds, but ifyou want to make it last longerduring testing then you cantemporarily short-circuit pin 12of 1C1 to ground fora continuoustone; of course this short mustbe removed once testing is

completed.

KIT OFFERA full kit of parts isavailable from JAB

(see below) at£3.30 plus El P&P

COMPONENTSResistors - All resistors are 0.25 Watt 10% Tolerance.R1 1MR2 150kR3 12kRV1 10k Horizontal PresetCapacitors - All capacitors should be 16 volt working or

higher.C1, C2 1rIF Disk CeramicC3 4.7µF Tantalum BeadC4 47nF Disk Ceramic

SemiconductorsD1 IN4148ICI 4060

Additional ItemsXL1VeroboardSwitch

XR455 455kHz ceramic resonatorAny convenient sizePush -to -Make if you do not want to modifyyour set or Single -Pole Single -Throw if youare installing the toneburst inside your set.

3 Veropins16 -Pin IC HolderConnecting WireComponents are available from JAB ElectronicComponents, 1180 Aldridge Road, Great Barr,Birmingham B44 8PB.


Letters and Diary

Readers __-- -LettersK ep sending your letters and photographs to:

TI Editor, D-i-Y Radio, RSGB, Lambda House, Cranborne Road, Potters Bar,

11EIrls, EN6 3JE, and we will send a pen to the sender of each letter published.

KEEN TO PROGRESS

I AM TEN years old (nearly eleven).My brother Howard and I areinterested in radios and have bothmade our own crystal set radios.We often listen to our dad's radioand write down the channels thatwe listened to. Som'etimes we hearpeople speak to the coastguard.We have a yacht which has a radio.We have walkie talkies but we soonhope to talk on the proper radio.

Russell Tribe

VALUE FOR MONEY

I ENCLOSE MY renewal cheque.Once again, I think thatD-i-Y Radiomagazine is good value and reallydoes help one to understand radioetc.

R C Butcher

A PLEA FROM SPAIN

I AM CURRENTLY subscribing toD-i-Y Radio. As an absolutebeginner, I enjoy it but often have

trouble understanding articles.Living in southern Spain, 'radio -wise' I am quite isolated. Thus, I

don't understand, for instance,'radio frequency mixing' as aconcept. I have no way of findingout and most of your articlesassume some knowledge and arenot aimed at total beginners.

A feature in the January/Februaryissue has inspired me to try and putup a dipole antenna as I havesufficient space. However, I havetwo basic queries. Firstly, whatmaterial should the antenna bemade from? Should it be copper orcan I use ordinary steel wire?Secondly, with regards to the co-axial cable, are both the conductor(centre) and the braid connector tothe aerial point on the receiver orjust the centre wire? I wouldappreciate an answer. Also, is it

possible for me to buy back issuesof D-i-Y Radio?

Sam Fannin[We try to include articles for thebeginner as well for readers whoare more experienced and I amsure that you will understand'mixing' when you have learnt moreof the basics. Antenna wire shouldbe copper preferably. The centrewire of coaxial cable should go tothe aerial' connection on yourreceiver but it is also important toconnect the braid to the 'earth'terminal. Back issues are availableto subscribers at 25p each - Editor]

Amateur Radio and the RSGBRADIO AMATEURS are qualified radio operators

who are licensed to talk to other operators, often

in distant countries, from their own homes.Amateur radio is a hobby for all ages but it isdifferent from CB radio because a very widevariety of frequencies (wavelengths) can be used,

and contacts can be in different `modes'; byMorse code or teleprinter, between computers

or even television. Many amateurs build all or

part of their station equipment.

The Radio Society of Great Britain (RSGB)

is the national society for all radio amateurs(transmitters and listeners) in this country. It has

over 30,000 members, including many inoverseas countries.

The Society looks after the interests of radio

amateurs throughout the UK. Talks between the

RSGB and the Government's Radio -

communications Agency have resulted in the

popular amateur radio Novice Licence.

In particular the RSGB is keen to encourage

the experimental side of electronics and radio,

and the Society's monthly magazine. RadioCommunication is sent free to all members.We're having lots of fun with our hobby, so why

not join us?

If you would like more information on theRSGB or the Novice Licence, write for anInformation Pack to the address below (enclosing

a large stamped self-addressed envelope).

RSGB, Lambda House, Cranborne Road, Potters Bar, Herts EN6 3JE.

MAR APR

MARCH13 Novice RAE

18 All Formats Computer Fair(see opposite)


19 Norbreck Amateur Radio &Computer Exhibition, Black-pool. Details tel 0151 6305790.

24 King's College London Radioand Communication Day (SeeNews page 3).

25/26 CQWPX SSB Contest. A 48 -hour event with bonus pointsfor each new callsign prefixworked. Bands: 1.8, 3.5, 7,14, 21 and 28MHz.



APRIL1 All Formats Computer Fair

(see opposite)


4 ORS Cumulative Contest.Slow Morse on 3540 to3580KHz, 1900-2030 UTC.



9 White Rose Rally, LeedsUniversity. Details tel 01973189 276.

9 1st 1.3 / 2.3GHz Fixed andSWL Contest, 1700 - 2100UTC.

14 Closing date for entry to JuneNovice RAE



22 International Marconi DaySpecial Event Stations

22 RSGB Headquarters AnnualOpen Day. Details tel 01707659015.

23 Swansea Amateur Radio &Computer Show, SwanseaLeisure Centre. Details tel01792 404 422.

23 Low Power Fixed Contest,0700-1100UTC. 3510-3560KHz and 7010-7040KHz CW.5W max output.


28 ORS Cumulative (see above)

D -/-Y RADIO March -April 1995

4 Puzzle Page

DI-DIZAH-DAH-DMITWIN: UnderstandingBasic ElectronicsOUR TOP PRIZE this time is this 300 -page book from the American Radio Re-lay League (ARRL). Full of illustrations,Understanding Basic Electronics explainselectronics in an easy to understand waywhich will appeal to both the absolutebeginner and the more experienced.

1st Prize: A copy of Understand-ing Basic Electronics.

2nd Prizes: We have five free -sizeT -Shirts for the runnersup.

THIS EDITION FEATURES the MorseCode so our competition is a Morse mes-sage for you to decode. It is written not as

dots and dashes, but as dits and dahswhich is the way Morse sounds.

Di-dah-dit di-di-dit dah-dah-dit dah-di-di-dit di-di-di-dit di-dah di-di-dit di-di-dit di-di-dahdi-dah-dah-dit di-dah-dah-dit dah-dah-dah di-dah-dit dah dit dah-di-dit di-dah dah-dahdi-dah dah dit di-di-dah di-dah-dit di-dah-dit di-dah dah-di-dit di-dit dah-dah-dah di-di-dah-

dit dah-dah-dah di-dah-dit dah-dah-dah-di-dit di-di-dah-dah-dah dah-di-dah-dah dit di-dahdi-dah-dit di-di-dit

Send your decoded message on a postcard or the back of an envelope to: The Editor,D-i-Y Radio, Radio Society of Great Britain, Lambda House, Cranborne Road, Potters Bar,

Herts EN6 3JE. The winners will be announced in the July -August edition of D-i-Y Radio.

y RADIO

FREEENTRY FOR ONE D-i-Y RADIOSUBSCRIBER AT ANY ONE ALLFORMATS COMPUTER FAIR HELD

DURING MARCH OR APRIL.

WORTH UP TO f4CUT THIS TICKET OUT AND HAND

IT IN AT THE DOOR FOR FREEADMISSION.

PHOTOCOPIES OF TICKET NOT

ACCEPTED.

REDEMPTION VALUE 0.00001P


ALL FORMATS COMPUTER FAIRS take place throughout the UK. Theevents scheduled for March and April are listed below. Opening times are 10amto 4pm and admission costs £4 per adult (£2 after 2pm), £2 for a child andwheelchairs users get in free. But you can get in FREE by cutting out the ticket(left). On sale at these fairs are CDROMs, Pentium motherboards, public domainand shareware programs, games, second-hand computers etc. The events are:Sat 18 MarSun 19 MarSat 25 MarSun 26 MarSat 1 AprSun 2 AprSat 8 AprSun 9 AprSat 15 AprSun 16 AprSun 23 Apr

Haydock Park Racecourse, Jcn 23, M6.NAC (Royal Showground), Stoneleigh.Courage Hall, Brentwood, Jcn 28, M25.Tolworth Recreation Centre, A3 Surbiton.Northumbria Centre, Washington.Woodside Hall, St George's Cross, Glasgow.Haydock Park Racecourse, Jcn 23, M6.Royal Baths Assembly Rooms, Harrogate.Bassetlaw Leisure Centre, Eastgate, Worksop.National Motorcycle Museum, Jcn 6, M42.Tolworth Recreation Centre, A3 Surbiton.

WINNERS!

HERE ARE THE WINNERS

of our Block Diagram Com-petition (Nov -Dec 94 is-sue).

1st Prize: Duncan Goodall,2E0AFO, of Horsham, WSussex, wins the NetsetSWR meter.

2nd Prize: Simon Pedley ofKingsbridge, Devon, wins an

RSGB Call Book.

3rd Prizes: A A Rose ofMaidenhead, Berks, andMark Bean of Sudbury, Suf-folk, win RSGB Diaries.

The answer, by the way,was that the block diagramrepresented a Superhetero-

dyne (superhet for short)Receiver.

Special Offers

Every D-i-Y Radio includesa special offer. This issue'soffer appears on page 8. /To take advantage of /the offer, send this

corner token //with your 4order.

,ALINCO

?tin DonD1-482390E 70cm<

Where in the Worldwill you find Better?

DJ -480V/M SCAN CALL

STEP APO

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VHF/UHF FM TWIN BAND

?tin DonDI -180E 2.m <

199 \

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ALINCO is distributed in the UK by: Tel 0702 206835

WATERS & STANTON ELECTRONICS

r a d i...1995/03/04 · r a d i an introduction to amateur radio-for beginners of all ages o...

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