2.45GHz RF Signal Detector
designed by David Johnson, P.E.
This passive RF indicator hobby circuit is made from a few simple parts. A bent piece of wire forms a 2.5GHz antenna. A 100uA moving coil meter is used to display the relative intensity of the RF signal. Two microwave rated detector diodes form a simple voltage doubler circuit, which feeds a DC voltage to the meter movement, proportional to the RF field strength. This circuit can be used with some cell phones and many cordless telephones. It can also detect RF leaking from a microwave oven.