This circuit uses a combination of transistors SA101 and SA103, as the modulation signal amplifier.

Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz and in North America an extended MW broadcast band goes from 535 kHz to 1705 kHz.

Wavelengths in this band are long enough that radio waves are not blocked by buildings and hills and can propagate beyond the horizon following the curvature of the Earth; this is called the groundwave. Practical groundwave reception typically extends to 200-300 miles, with longer distances over terrain with higher ground conductivity, and greatest distances over salt water. Most broadcast stations use groundwave to cover their listening area.