This circuit is from a 1993 Italian magazine, but it can be easily assembled today. For 110 V, just use a 560nF polyester capacitor instead of the original 330nF C1. A small antenna can be connected to the TR2 collector. The transistors can be BC548 for TR1 and BF494 for TR2. L1 has 4 turns of wire 22 to 26 in the form of 1 cm without core. The microphone is a 3-terminal electret.
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