Found in an American documentation from the 90s, this circuit has a configuration that has been extensively explored in other articles on this site. The FET can be the MPF102 or equivalent.
The diagram shows a tone control with the LM381 IC. The circuit is from a Radio Electronics from...
Published in Radio Electronics magazine in March 1963, this circuit uses 4 transistors of the...
In the figure we have the suggestion of coupling an audio oscillator to monitor the CW...