This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is not an easy component to obtain and the power can be supplied with a single button cell.
This circuit can be found in a 1970 Motorola documentation. The circuit can be implemented with general...
This shield circuit with an optical coupler was found in an 90s EDN. The circuit can be used with...
This circuit is from 1977 documentation, and high current equivalent transistor must be used. The...