Originally published by the Radio Society of Great Britain, the projects were all chosen to be useful and straightforward, with the emphasis on practicality. In most cases the workings of the circuit are described, and the projects are backed up by small tutorials on the components and concepts employed. In the 21st century it may seem strange that few of the published circuits use integrated circuits (chips). This is intentional as it is much easier to understand how the circuit works when using discrete components.
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
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
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
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
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