We found this circuit in an old American publication from the 1980s. Transistors can be general-purpose types like the BC548, and the tuning frequency is given by the L and C components.
This circuit for the 3 to 6 MHz band was found in a 90s Popular Electronics. The components of the...
Found in a 1966’s General Electric documentation, this circuit uses a triple diode from the time....
In the circuit shown in the figure, when the input voltage rises to 27 V, the TL431 triggers the...