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.
We have here a very interesting project found in a 1982 publication. By the operation of the...
We found this circuit in an old American manual. The formulas allow the gain to be calculated as a...
This circuit is from the time when cars used contact breakers. This 80's version measures the dwell...