The coil consists of 100 turns of wire 28 in a wooden or PVC tube from 2 cm to 2.5 cm in diameter with a socket on the 50th turn. The diode can be 1N34 or any crystal. The antenna must be long, C1 is a radio variable AM, C2 of 10nF and C3 of 100nF. The phone must be made of crystal or ceramic and the antenna must be long. Grounding is important. R1 is 10k-ohm.
