This is a project of a simple metal detector circuit. The circuit is easy to build using only one transistor and few other components. The circuit is a colpitts oscillator which board cast on AM band.
Take a good quality am receiver and place it near this circuit and search the signal in your radio, when the radio found the signal you will hear no sound. Now when you place this metal detector circuit near any metal object you will hear hissing sound from your AM radio. L1 is equal to 60 turns of #36 enameled copper wire wound on 1cm PVC tube.
A 6V or 9V battery should be used to power the circuit. Do not use power supply to power the circuit it will create noise.
Q1 = BC548
Resistors = 68R (ohm), 2.2K, 3.3K
Capacitors = 10pf, 100pf, 10uf 16v
S1 = on/off Switch