AM is also one of the easiest bits of infrastructure to cobble together: you need an oscillator, an audio amplification circuit, a microphone, and a length of w

AM is also one of the easiest bits of infrastructure to cobble together: you need an oscillator, an audio amplification circuit, a microphone, and a length of wire. The circuit is so simple anyone can build one DIY or with a hobby kit (though obviously the range on a low power device is tiny).