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.
In the figure we have a simple signal tracer circuit to be coupled to the volume control of an AM...
This circuit was found in documentation from the 90s, using components from that time. The...
This circuit, obtained from old documentation, allows the recovery of sulfated batteries. The...