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.
With 3 transistors, we found this receiver in a documentation from 1966. The circuit has an output...
This sonic relay or vox was found in a Popular Electronics from the 90's. The power MOSFET can be of...
This tri-state comparator was found in a circuit manual from the 1980s, but it can be easily...