The circuit shown is a simple MW tuner that can be connected to the input of any audio amplifier. As the circuit consumption is low, it can be powered by a small 9 V battery. The L1 coil is formed by 30 + 70 turns of enameled wire 28 or close to it in a 0.8 to 1 cm diameter ferrite rod and 10 to 30 cm in length. The variable capacitor is of the small type used by a medium-wave radio not in use. The audio output cable must be shielded, and the diodes are made of germanium and have equivalent equivalents.
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