The simplest radio set

I. Earphone radio

This radio consists of only four parts. Two wires, a crystal diode, and an old telephone earphone.
Construction: Set the two wires on the taps, and a diode connecting them. Therewith it is ready. You only have to put to earth, and span the antenna. It is strange by the earphone. Its metal carcase functions as a capacitor. They form an oscillator tank with the spool in the earphone. It works in the amplitude-modulated waveband. As the radio is untuneable, it broadcasts the programme, which has the largest field strength. In Hungary this is the Radio Kossuth.

II. Matchbox-radio

This appliance is just like the previous, and it contains a separate oscillator tank. Its speciality is that the spool is hand-made, and the components are placed into a matchbox. It can be easily connected to an amplifier.