Some time ago I wanted to trace some wiring in the walls of my house. My cheapo metal detector kit wasn’t up to it so I thought an all band radio might work. Basically it’s a radio without the tuner. It uses an an antenna and detector to pick up any radio transmission on any band and play it out through a speaker. I based my design on this.
This is the detector circuit, based around an IN5711 small signal rectifier and a 2N3904 as buffer amp.
This is the detector hooked up to the audio amplifier (LM386 with a circuit straight off the data sheet). The box is a plastic conduit enclosure from the hardware store.
Here’s the box with the volume control/power switch on the front and the antenna poking out the back.
Here’s a view showing the 9v battery holder. The punch out sections are almost perfect for holding one of these batteries in place. It just needed a little milling with the trusty Dremel.
The wires I’m trying to trace are dead so I need to build a simple signal injector and hopefully I can trace the tone to the point where the wire is broken.