This circuit was found in an American 1980s documentation. The transistorized step is the receiver's last IF and the diode is the receiver's existing detector.
This circuit is from Radio Electronics from February 1987. The frequency is given by the crystal that...
In this circuit, a light-sensitive SCR or Light Activated SCR determines the operation of an...
This 3-transistor circuit was found in a Mullard manual from 1960. The transistors are germanium of the...