[jacquesm]

AM radios are extremely simple and utterly fool proof, they can be made with only a handful of simple parts. Even so, these systems are archaic and these days you can make much more complex radio systems using a SDR which effectively reduces the whole radio to a pre-amp an ADC, an embedded CPU and some software.

[drweevil]

AM is a good modulation choice for low signal environments. It is used in the airbands for this reason.

[jacquesm]

Precisely, it degrades very gracefully, unlike FM or digital.