This project is a broadband field strength sensing probe that has a 15cm antenna. It is able to detect radio energy and read the output on a common multimeter millivolts scale. It can be used to test 4MHz, 35 MHz, 55 MHz, 100 MHz, 384 MHz, 900 MHz, cell phone, and microwave oven. The meter is powered from a single cell battery and the circuit draws 60uA of current.
Electromagnetic field strength indicator – [Link]