Solid State Shortwave Receivers For Beginners - The Listeners Guide

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a much better chance of obtaining good results from his or her receiver. For example, searching the 160 Metre amateur band for distant (DX) stations using a simple receiver would be a waste of time, whereas searching the 20 Metre band for such signals would almost certainly be much more fruitful. A table giving the frequency limits of the S.W. amateur bands is shown below. l60 Metre Band 1.8 to 2.0 MHZ 80 Metre Band 3.5 to 3.8 MHZ 40 Metre Band 7.0 to 7.1 MHZ 20 Metre Band 14.0 to 14.35 MHZ 15 Metre Band 21.0 to 21.45 MHZ 10 Metre Band 28.0 to 29.7 MHZ The 160 Metre band is shared with maritime stations, and the maximum permissible transmitter input power for licensed amateur stations is only some 10 Watts in this country. Therefore most of the stations received on this band will be within a radius of about 50 miles from the receiving location. On in frequent evenings conditions are such that reception over distances of a few hundred miles or even more is possible. 80 Metres is suitable for both local and DX reception, the more distant stations being received mainly during the late evening and the small hours of the morning. This makes 80 Metres one of the most interesting of the bands. The qualities of the 40 Metre band, are similar to those of 80 Metres, but theoretically DX reception should be better on 40 Metres. This is probably rarely the case in practice as this band is only 100 kHZ wide and has the 41 Metre broadcast band lying just off its high frequency end. This tends to make reception rather difficult on this band, particularly so after dark when the situation is exacerbated by the frequency encroachment of powerful broadcast stations onto the band. This has led to the 40 Metre band being one of the least popular bands among both transmitting amateurs and S.W. listeners. 160, 80 and 40 Metres are collectively known as the ‘Low Frequency’ (L.F.) bands. Undoubtedly the best band for amateur DX reception Is 20 Metres, and this band can usually be relied upon to provide a number of interesting transmissions. The 10 and 15 Metre bands are also usually associated with DX reception, but these bands, particularly 10 Metres, are greatly affected by propagation conditions that vary considerably with changes in the upper atmosphere. 8
Propagation The reasons for the amateur bands having these differing chacteristics can best be explained by looking at how radio waves travel. The diagram shown in Fig.1 will help with this explanation. When the transmitter is close to the receiving station the radio waves can travel direct from the transmitter to the receiver. This is represented by line A - B in the diagram, and is termed the ‘ground wave’. At frequencies of more than a few MHZ the ground wave tends to be absorbed by the earth and cannot be used for reliable communications, except over very short distances. After dark the ionised E layer of the atmosphere will reflect radio waves at low and medium frequencies, except those that hit it at a very high angle. These merely pass straight through and pass on into space. This reflected signal is represented by line A - C - D, and can provide communications over a far greater distance than the ground wave. It is termed the ‘sky wave’. 9
Page 1 and 2: Solid State Short Wave Receivers Fo
Page 3 and 4: SOLID STATE SHORT WAVE RECEIVERS FO
Page 5 and 6: CONTENTS Page CHAPTER 1 Frequency S
Page 7: CHAPTER 1 There is a strange fascin
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 53 and 54: Components List for Fig.20 Resistor
Page 55 and 56: A.F. noise from Tr2 from reaching s
Page 57: The gain of the I.C. is fixed at ap
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Like MOSFETS, CMOS I.C.s can be dam
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CHAPTER 4 Portable Receivers One mi
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Normally the telescopic aerial shou
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Components List for Fig.26 Resistor
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A.M. Signal It will be helpful to f
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As should be apparent by now, if th
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Components List for Fig.29 Resistor
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the mains earth (regardless of whet
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Blank page 80
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Components List for Fig.30 R1 3.3k
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Components List for Fig.32 R1 3.3k
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Apart from increasing the sensitivi
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Components List for Fig.36 R1 390 o
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prevent the oscillator from operati
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BERNARDS No 222 Solid State Short W
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Solid State Shortwave Receivers For Beginners - The Listeners Guide

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