― Rangkaian Detektor Emas. Here the very simple and easy build gold detector circuit. The circuit capable to sense gold or metal or coins from a distance of about 20cm, depending on the size of the object to detect. ∙ The circuit oscillates at about 140kHz and a harmonic of this frequency is detected by an AM radio. You can simply tune the radio receiver until a squeal is detected. ∙ When the search coil is placed near a metal object, the frequency of the circuit will change and [...].