We found this circuit in a Popular Electronics of the 90s. The circuit can be easily mounted today, as the components are common. The SCR can be the TIC106.
This circuit, for its simplicity and the fact of using a super-regenerative detector only works...
This circuit, from a former publication of 1968 was originally designed for germanium transistors, but with the...
This circuit was obtained in an American publication of the time. Transistors are commonly used. The...