This circuit was found in American documentation from 1966, but it can be assembled with a modern equivalent transistor. The circuit is based on a mechanical tuning fork with a coil feedback system.
Using the name of varactor this circuit was found in the Radio Electronics magazine of July 1982....
We found this circuit in a 1960 Radioarama magazine. The instrument tests common general-purpose transistors...
This circuit uses an RCA module from the time. The circuit is from a Radio Electronics magazine from...