Navigational Beacons Radio signals are an essential means of navigating for most ships and aeroplanes and the frequencies between the Long Wave band and the MW band have been allocated for this purpose. More surprisingly, a sizeable number of aeronautical beacons operate in the MW band interspersed amongst the broadcasters. Over 100 beacons are known, of which the majority are in the former Soviet Union. Most signals described so far are more or less permanent features in the MW landscape. However, there are several more transient types of signals which can be heard, the most prominent of which are pirates and clandestine operations.
Pirates are stations operating openly with out official licences from any country.
They range from one time hobby pirates operating from someone's bedroom to fully financed operations broadcasting from ships at sea. The heyday of the seaborne pirate seems to be gone since the likes of Radio Caroline, Voice of Peace and Radio New York International have passed into the history books. Just one radio ship is currently operational, in the Mediterranean. Clandestine stations are usually politically motivated broadcasters often supported by a covert government operation. These stations come and go, reflecting political changes in their 'host' country.