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 circuit turns off after a time given by capacitor C1. This component can have from 1 to 1,000...
The operational amplifier is not very common today, but in its place an equivalent, even of...
This circuit was obtained from an English magazine from 1985. The N414 is a complete, not easy to...