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.
Found in a 1967 US magazine this circuit generates positive and negative voltage pulses from a...
This audio mixer was found in an old American documentation. The potentiometers are 1M and the...
In this circuit of a 1968 publication the unijunction may be 2N2646 and the transistor BC548. The...