Radio and Electronics Cookbook
Radio and ElectronicsCookbook
Edited byDr George Brown, CEng, FIEE, M5ACN
OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI
NewnesAn imprint of Butterworth-HeinemannLinacre House, Jordan Hill, Oxford OX2 8DP225 Wildwood Avenue, Woburn, MA 01801-2041A division of Reed Educational and Professional Publishing Ltd
A member of the Reed Elsevier plc group
First published 2001
Radio Society of Great Britain 2001
All rights reserved. No part of this publication may be reproduced inany material form (including photocopying or storing in any medium byelectronic means and whether or not transiently or incidentally to someother use of this publication) without the written permission of thecopyright holder except in accordance with the provisions of the Copyright,Designs and Patents Act 1988 or under the terms of a licence issued by theCopyright Licensing Agency Ltd, 90 Tottenham Court Road, London,England W1P 0LP. Applications for the copyright holders writtenpermission to reproduce any part of this publication should be addressedto the publishers
British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library
ISBN 0 7506 5214 4
RSGBLambda HouseCranborne RoadPotters BarHertsEN6 3JE
Composition by Genesis Typesetting, Laser Quay, Rochester, KentPrinted and bound in Great Britain
v
Contents
Preface ix
1. A medium-wave receiver 1
2. An audio-frequency amplifier 4
3. A medium-wave receiver using a ferrite-rod aerial 9
4. A simple electronic organ 12
5. Experiments with the NE555 timer 17
6. A simple metronome 21
7. What is a resistor? 24
8. Waves Part 1 27
9. A beat-frequency oscillator 31
10. What is a capacitor? 34
11. Waves Part 2 38
12. An LED flasher 41
13. Waves Part 3 44
14. Choosing a switch 46
15. An aerial tuning unit for a receiver 49
16. A simple 2 m receiver preamplifier 52
17. Receiving aerials for amateur radio 54
18. The Colt 80 m receiver Part 1 58
19. A crystal radio receiver 62
20. The varactor (or varicap) diode 64
21. A portable radio for medium waves 65
22. The Colt 80 m receiver Part 2 70
Contents
vi
23. A simple transistor tester 73
24. An introduction to transmitters 77
25. The Colt 80 m receiver Part 3 81
26. A two-way Morse practice system 88
27. The Colt 80 m receiver Part 4 91
28. A simple crystal set 95
29. A crystal calibrator 100
30. A simple short-wave receiver Part 1 104
31. A fruit-powered medium-wave radio 106
32. A capacitance bridge 109
33. A simple short-wave receiver Part 2 113
34. A basic continuity tester 117
35. A charger for NiCad batteries 119
36. An 80 metre crystal-controlled CW transmitter 123
37. A solar-powered MW radio 129
38. A receiver for the 7 MHz amateur band 133
39. Diodes for protection 137
40. An RF signal probe 140
41. An RF changeover circuit 142
42. A low-light indicator 146
43. A J-pole aerial for 50 MHz 149
44. Measuring light intensity the photometer 153
45. A 70 cm Quad loop aerial 156
46. A UHF field strength meter 160
47. Christmas tree LEDs 162
48. An audio signal injector 166
49. Standing waves 168
50. A standing-wave indicator for HF 170
51. A moisture meter 174
52. Simple aerials 177
53. A breadboard 80 cm CW transmitter 182
Contents
vii
54. A 7-element low-pass filter for transmitters 186
55. Radio-frequency mixing explained 189
56. A voltage monitor for a 12 V power supply 192
57. A 1750 Hz toneburst for repeater access 196
58. A circuit for flashing LEDs 201
59. Digital logic circuits 205
60. A resistive SWR indicator 210
61. An audio filter for CW 213
62. An electronic die 215
63. The absorption wavemeter 222
64. An HF absorption wavemeter 224
65. A vertical aerial for 70 cm 228
66. A UHF corner reflector aerial 230
67. A switched dummy load 234
68. A simple Morse oscillator 238
69. A bipolar transistor tester 240
70. The Yearling 20 m receiver 245
71. Adding the 80 metre band to the Yearling receiver 251
72. How the Yearling works 255
73. A field strength meter 258
74. Preselector for a short-wave receiver 261
75. An audible continuity tester 265
76. An experimental 70 cm rhombic aerial 268
77. Water level alarm 272
78. A delta loop for 20 metres 275
79. A simple desk microphone 279
80. Morse oscillator 284
81. A simple 6 m beam 287
82. An integrated circuit amplifier 291
83. A novice ATU 293
84. CW QRP transmitter for 80 metres 297
Contents
viii
85. An audio booster for your hand-held 303
86. A grid dip oscillator 306
87. A CW transmitter for 160 to 20 metres 312
88. Matching the end-fed random-wire aerial 315
Preface
Although we are surrounded by sophisticated computerised gadgets thesedays, there is still a fascination in putting together a few resistors, capacitorsand the odd transistor to make a simple electronic circuit. It is reallysurprising how a handful of components can perform a useful function, andthe satisfaction of having built it yourself is incalcuable.
This book aims to provide a wide variety of radio and electronic projects,from something that will take a few minutes to a more ambitious weekendsworth. Various construction techniques are described, the simplest requiringno more than a small screwdriver, the most complex involving printedcircuit boards.
Originally published by the Radio Society of Great Britain, the projects wereall chosen to be useful and straightforward, with the emphasis onpracticality. In most cases the workings of the circuit are described, and theprojects are backed up by small tutorials on the components and conceptsemployed. In the 21st century it may seem strange that few of the publishedcircuits use integrated circuits (chips). This is intentional as it is much easierto understand how the circuit works when using discrete components.
Anyone buying the Radio and Electronics Cookbook will find that it willlead to hours of enjoyment, some very useful and entertaining gadgets, andincreased knowledge of how and why electronics circuits work, and a greatsense of satisfaction. Beware, electronic construction is addictive!
WARNING: This book contains construction details of transmitters.It is illegal to operate a transmitter without the appropriate licence.Information on how to obtain an Amateur Radio Licence can beobtained from the Radiocommunications Agency, tel. 020 72110160.
A medium-wave receiver
1
1 A medium-wave receiver
IntroductionLet us start off with something that is really quite simple and yet is capableof producing a sense of real satisfaction when complete a real medium-wave (MW) radio receiver! It proves that receivers can be simple and, at thesame time, be useful and enjoyable to make. To minimise the confusion toabsolute beginners, no circuit diagram is given, only the constructionaldetails. The circuits will come later, when you have become accustomed tothe building process. In the true amateur spirit of ingenuity andinventiveness, the circuit is built on a terminal strip, the coil is wound ona toilet roll tube (as amateur MW coils have been for 100 years!), and thereceiver is mounted on a piece of wood.
Putting it togetherStart by mounting the components on the terminal strip as shown in Figure1, carefully checking the position and value of each one. The threecapacitors are all the same, and so present no problem. They (and theresistors) may be connected either way round, unlike the two semi-conductors (see later). The resistors are coded by means of coloured bands.You can refer to Chapter 7 if you have difficulty remembering the coloursand their values.
Figure 1 Terminal strip position of components
Radio and Electronics Cookbook
2
1. Brown, Black, Yellow 100 000 ohms (R1, R5, R6)2. Green, Blue, Brown 560 ohms (R2)3. Red, Violet, Brown 270 ohms (R3)4. Brown, Black, Orange 10 000 ohms (R4)
The integrated circuit (the ZN414Z) and the transistor (the BC184) must beconnected correctly. Check Figure 1 carefully before fitting each device.
Now wind the coil. Most tubes are about 42 mm diameter and 110 mmlong. Dont worry if your tube is slightly different; it shouldnt matter. Maketwo holes, about 3 mm apart, about 40 mm from one end, as shown inFigure 2. Loop your enamelled wire into one hole and out of the other, anddraw about 100 mm through; loop this 100 mm through again, thusanchoring the wire firmly. Now wind on 80 turns, keeping the wire tightand the turns close together but not overlapping. After your 80th turn,make another two holes and anchor the wire in the same way as before.Again, leave about 100 mm free after anchoring. Using another piece ofenamelled wire (with 100 mm ends as before), loop one end through thesame two holes which contain the end anchor of the last winding, wind twoturns and anchor the end of this short winding using another pair of holes.Figure 2 shows the layout.
Figure 2 The layout of theparts on the wooden base
A medium-wave receiver
3
With some glass paper, remove the enamel from the ends of both piecesof wire which go through the same holes (i.e. the bottom of the large coiland the top of the small coil), then twist these bare ends together.Remove the enamel from the remaining ends of the coil. The co