Solid State Shortwave Receivers For Beginners - The Listeners Guide

signal is obtained. However, for best results on A.M. and S.S.B. a
receiver fitted with a product detector is needed. in its most simple form
such a set needs few components and consists basically of just a product
detectors an oscillator, an R.F. filter, and an audio amplifier.
80 Metre Direct Conversion Receiver (Fig.29)
The direct conversion receiver described here is of a fairly basic
type, the only refinement being an untuned R.F. amplifier. The
complete circuit diagram of the set is shown in Fig.29. It is desighed
for use on only one band, and this is the 80 Metre band. This band has
been chosen as it is suitable for both amateur and DX listening, and its
relatively low frequency means that oscillator stability is not likely to
be lacking. Oscillator stability is an important factor in a direct conversion
receiver, as if the oscillator frequency should drift only very
slightly, a change in the pitch of the audio output will result.
Tr1 is used as the R.F. amplifier, and VR1 is the gate bias
resistor for Tr1. This also acts as a simple RF. gain control. R2 is the
source bias resistor for Tr1, and C2 is its bypass capacitor. R1 and C1
are a supply decoupling network.
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