Greater simplicity for a radio receiver than that achieved by the author of this project found in a 1981 publication, is difficult to achieve. As we can see from the figure, this receiver simply consists of two coils, an antenna, a switch and a headset that must be made of crystal or high impedance magnetic. L1 is formed by 80 turns of 32 AWG enameled wire and L2 is formed by 5 or - 6 turns of the same wire over L1. The antenna is 10 m long or more. The coil must have a ferrite core. When the key is closed, the reception range changes. See that the tuning of this receiver is achieved by moving the ferrite core in the coil.
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