Solid State Shortwave Receivers For Beginners - The Listeners Guide

Components List for Fig.24
Resistors (¼ watt 10%).
R1 1.2 Meg.
R2 3.3k
Capacitors.
Cl l5nf plastic foil.
C2 5.6nf plastic foil.
C3 4.7nf ceramic.
C4 4mfd. 10v.w.
C5 100mfd. 10v.w.
VC1 50pf air spaced (type C804).
VC2 365pf air spaced (type 0).
Semiconductors.
Tr1 BC107.
Dl OA91.
Inductors.
T1 Denco D.P. coils Ranges 3,4, and 5 Green.
L1 10mH. (Repanco CH4).
Miscellaneous.
S1 S.P.S.T. toggle switch.
Chassis, panel, battery, sockets, etc.
out any R.F. that might find its way to the output, and could otherwise
cause instability.
C4 is the output D.C. blocking capacitor and C5 is a supply
decoupling capacitor. S1 is the on/off switch. R1 is the bias resistor
for Tr1. Regeneration is provided by using feedback between Tr1
collector and the third winding on T1. VC1 is the reaction control.
VC2 is, of course, the ordinary tuning capacitor.
Using the Set
The receiver is operated in much the same way as the previous
sets. One difference is that if VC1 is advanced more than fractionally
beyond the threshold of oscillation, the detector breaks into an ultrasonic
oscillation on top of the R.F. oscillation. This makes it rather
awkward to use for amateur band seception, although this is possible.
However, if the reader’s main interest is in amateur band recept on,
the f.e.t. portable described later would better suit his or her needs.
One does not obtain something for nothing with this circuit,
and the price that is paid for the tight aerial coupling is a loss of
selectivity. This is due to the loading effect of the aerial on the tuned
circuit, and this effect was demonstrated earlier in the section describing
the crystal set.
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