This circuit was obtained from a Radio Electronics from the 90's. The circuit limits the strength of an audio signal preventing saturation. Equivalent operational amplifiers can be tried.
This simple field strength meter was found in a 1967 documentation. The transistor is germanium, and the...
This is yet another version of the light-controlled oscillator that can be found on this website. This...
Found in a 1969 documentation, this circuit for the 20 MHz band does not use a transformer. The circuit is...