We found this circuit in an Argentine publication from the 70s. The coil can be made with 80 turns of wire 28 in a tube inside which runs a ferrite rod for tuning. The transistor can be the BC558 and the antenna (2) consists of a piece of wire from 30 cm to 1 meter in length. The range is small in the order of a few meters. The transformer is an output type for radio transistors and the microphone (1) is a small speaker of 2.5 to 5 cm.
