This is a field strength meter found in an 80's Hands On. The circuit operates at frequencies up to 500 MHz and has a buzzer as its indicator. Can be used as a detector for spy transmitters.
This analog frequency meter for low frequencies was found in Radio Electronics magazine from July...
The integrated circuit used in this 90's circuit is not very common today. An equivalent...
This circuit for generating precise reference signals was found in the April 1973 issue of Radio...