Step 1, Tune the radio to highest band on the AM setting. Make sure you are not tuned to a station. You should hear the static tone clearly and steadily. This will allow you to hear any differences in the tone when your device detects a metal object.[1] X Research sourceStep 2, Assemble the search head. Turn on your calculator. Next, position the two devices back-to-back, until a steady, dull tone is emitted. You may have to arrange the devices at certain angles or distances to achieve this