This experimental AM microphone was found in an Argentine publication from 1973. The recommended microphone must be charcoal, but a small speaker can be used for this purpose. The transistor can be the BC558 and the coil can be made with 100 turns of wire 32 on a ferrite rod, but so that it can slide to adjust the frequency. The range is only a few meters. L1 is a shock of 2 to 47 mH.
