Solid State Shortwave Receivers For Beginners - The Listeners Guide

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Components List for Fig.21 R8 680 ohms. R9 220k. VR2 50k log, carbon. C9 100mfd. 10v.w. C1O 22nf plastic foil. Cli 2.2nf ceramic. C12 22nf plastic foil. C13 100mfd. 10v.w. I.C. LM380N. Wiring board, etc. 56
The gain of the I.C. is fixed at approximately 50 times (34dB.) by an integral feedback network. This is rather more than is required in this particular application, and in fact very little voltage gain is required here as the output from the basic receiver circuit has quite a high amplitude. The output stage is really only required to provide the high signal currents required to drive the speaker. R9 is used to attenuate the output from the basic receiver to some degree, and so provide a more realistic level of audio voltage gain. It is extremely important to ensure that no R.F. signal finds its way into the output stage, as this would result in violent instability. Additional R.F. filtering is provided by C11. Note that if the output stage is added, C7 of the basic receiver plays no useful part in the operation of the set, and is omitted. Apart from feeding a speaker, the output stage will also work satisfactorily into any type of headphone or earpiece. CMOS Receiver (Fig.22) CMOS devices seem to appear in circuits for the amateur with increasing frequency. These are a range of logic circuits, but they are also suitable for many linear applications, inclyding S.W. receivers. This receiver is based on two of the four gates that are contained in an RCA. CD4001AE I.C. It should perhaps be pointed out that this is not intended to be a joke, or a gimmick. This receiver is capable of a very good performance, and with the cost of the I.C. being less than that of many R.F. transistors and f.e.t.s, it provides a very novel and practical alternative to more conventional sets. The CD4001AE contains four 2 input NOR gates. By connecting the two inputs of a gate in parallel, an inverter can be formed. This can be biased to operate as a linear amplifier by connecting a resistor between the input and output. CMOS devices are based on complementary MOSFETS, and they thus have extremely high input impedances. When used in this way as a linear amplifier, the input impedance of the circuit is approximately equal to the value given to the biasing resistor. In this case a high input impedance is required so that a low level of loading is placed on the tuned circuit. As will be seen by refering to Fig.22, the tuned circuit is coupled to the input of one amplifier by way of D.C. blocking capacitor, C1. R1 biases the inverter. 57
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Solid State Short Wave Receivers Fo
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SOLID STATE SHORT WAVE RECEIVERS FO
Page 5 and 6: CONTENTS Page CHAPTER 1 Frequency S
Page 7 and 8: CHAPTER 1 There is a strange fascin
Page 9 and 10: Propagation The reasons for the ama
Page 11 and 12: 41 Metres 7.1 to 7.3 MHZ 31 Metres
Page 13 and 14: e. A length of wire is connected to
Page 15: Crystal Set CHAPTER 2 Ultra Simple
Page 18 and 19: Components List for Fig.6 T1 Denco
Page 20: To those unfamiliar with this metho
Page 23 and 24: The completed chassis and panel are
Page 25 and 26: crystal set is not very high. This
Page 27: ted it would look something like th
Page 30 and 31: eceivers it does have too low a val
Page 32: to have on. connection earthed. In
Page 35 and 36: It is very worthwhile experimenting
Page 37 and 38: layer, acts as the dielectric of th
Page 39 and 40: level that reaches the detector of
Page 41: CHAPTER 3 General Purpose Receivers
Page 44 and 45: The output of Tr1 is developed acro
Page 47 and 48: Components List for Fig. 18 Resisto
Page 50 and 51: Components List for Fig.19 Resistor
Page 55: A.F. noise from Tr2 from reaching s
Page 60: Like MOSFETS, CMOS I.C.s can be dam
Page 63: CHAPTER 4 Portable Receivers One mi
Page 66: Normally the telescopic aerial shou
Page 72 and 73: A.M. Signal It will be helpful to f
Page 74 and 75: As should be apparent by now, if th
Page 78 and 79: the mains earth (regardless of whet
Page 80 and 81: Blank page 80
Page 82 and 83: Components List for Fig.30 R1 3.3k
Page 84 and 85: Components List for Fig.32 R1 3.3k
Page 86 and 87: Apart from increasing the sensitivi
Page 89 and 90: Components List for Fig.36 R1 390 o
Page 91 and 92: prevent the oscillator from operati
Page 93: BERNARDS No 222 Solid State Short W
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Solid State Shortwave Receivers For Beginners - The Listeners Guide

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