It actually consists of a tunable field strength meter. The circuit is of an old documentation and the circuit must be tuned to the frequency to be monitored. The circuit offers the option to use a headset.
Found in Popular Electronics from the 1980s, this circuit is intended for switching filters with...
This circuit was found in a Japanese publication from the 1960s. The circuit uses a class B stage...
This circuit appears in other versions in this same section of the website and in other sections with...