Amateur Radio
N.B. This wiki needs a spring clean and the information on this page may be (considerably) out of date.
Ham Radio is what we typically think of when hearing 'Amateur Radio' - the ability to send and receive messages across a variety of frequencies allocated for hobbyist use.
Licence-free radio. Ian B's useful open-source open-hardware assemblies
Radio receivers - info on receiving (and decoding) the signals passing through the air