Radio beacons are simply transmitters that repeat some identifying signal over and over.
Most of them are for navigational purposes. There are thousands of beacons operating in the longwave radio spectrum, generally between 200 and 450 kHz, for the purpose of aeronautical and marine navigation. Most of the identifications come from Paulo Santos' most excellent AirNav page . Once again I'm starting a new list of loggings for this season. Previous seasons' logs are linked below.