This circuit was found in a Radio Experimenter Magazine published in 1950. The circuit uses a germanium diode as detector (crystal) and a tube. The phone is a high impedance 2 000 ohm type and the coil is formed by 80 + 80 turns of 28 or 30 AWG wire in a cardboard or PVC tube. The antenna must be long and the circuit needs two voltages to work: 1,5 V for the heaters and 45 V for the +B.
