Solid State Shortwave Receivers For Beginners - The Listeners Guide

Do not keep the iron on any joint any longer than is absolutely
necessary. All components can be damaged by excessive heath and
semiconductor devices are especially vulnerable. Germanium devices
such as diode D1 are very easily harmed by excessive heat, and it is
adviseble to use a heatshunt on each lead as it is connected. Heatshunts
are available, but it is not real ly necessary to use a proper headshunt,
and gripping the wire with a pair of long nose pliers, between the body
of the component and the joint, should be equally effective.
Note that the earth connections to VC1 and SK3 are made via
the chassis, and for this reason only one lead connects to each. SK3
must obviously be an ordinary jack socket of the open construction
variety, and not an insulated type. Conversely, the aerial and earth
sockets should be of an insulated1type as otherwise the aerial connections
will be shorted to earth. This obviously would not matter in the case
of the earth socket which is connected to the chassis anyway, but for the
sake of a neat appearance this socket should match the aerial ones.
The Denco coils are supplied in an aluminium container which
can be used as a screening can. Screening of the coils is not necessary
in any of the simple designs described here, and these cans are discarded.
The adjustable core of each coil is always screwed right down when the
coils are received, so that they will fit into their containers. The cores
should be unscrewed slightly so that about 5 to 10 mm of screwthread
protrudes from the top of each coil. This applies to all the circuits
described in this book, and not just to the crystal set.
If a suitable signal generator is available it is possible to adjust
the cores to give the correct frequency coverage on each band. However,
as it is unlikely that the majority of readers will have access ft
such equipment, such precise setting up is not really feasible.
Fortunately it is not really necessary anyway, and even if the
adjustment of the cores is considerably out, the frequency coverage
will not be so seriously affected that any of the broadcast or amateur
bands will be lost from any receiver’s coverage. Neither will there be
any gaps in the coverage of multiband receivers as there is a considerable
overlap in the coverage of each coil range. Also, the upper and lower
limits of the coverage obtained with the coils and the specified tuning
capacitor, extend well aboye and below the limits of the S.W. frequency
spectrum. Therefore, in the circuits described here anyway, the settings
of the cores should not be considered too critical.
Using the Set
Operating the cryrtal set is really very straightforward. There is
only one control and that is a conventional tuning control the tuning
will be fairly broad and if must ho admitted that the selectivity of a
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