A double port MOSFET is used in this circuit, which drives a 100 uA moving coil meter or close to it. The meter, in some cases, must be equipped with a 1 k ohm resistor to limit the current. The coil depends on the frequency range in which the circuit will operate. For the 80 to 110 MHz band, for example, this coil can be formed by 4 turns of wire 28 in the form of 1 cm in diameter without core. The antenna is of the telescopic type with 40 to 80 cm in length. The diode must be germanium and the operating point adjustment is made in the 47k ohms trimpot. The circuit is powered by a small 9 V battery.
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