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 uses a crystal phone and can be built with more modern transistors like the BC548. The...
The resistors in this circuit marked with * must be within 1% tolerance. The circuit is from the...
The existence of field effect transistors at the input of the integrated circuit (operational...