This circuit was obtained in a 1965 American magazine translation. The coil is formed by 40 + 40 turns of wire 28 in a cardboard tube that slides over a ferrite rod for frequency adjustment. The microphone can be a small speaker and the antenna is a telescopic type. The supply can be done with voltages from 6 to 9 V. The transistor can be the BC548 and the operating frequency range is between 550 kHz and 1600 kHz. The range is a few meters.