UK Offshore Radio 1964-1968
 
Medium wave usage

Under the Copenhagen Plan of 1948 the medium wave was divided into 121 channels, each 9 kHz wide. These were then allocated to the various European countries although many frequencies were taken by unauthorised stations and numerous channels were occupied by broadcasters who were not licensed to use them. The offshore stations used many frequencies - both on official channels and off - but we have only listed the ones that were used for a substantial period of time.
 
In sixties Britain it was more usual to refer to the wavelength (in metres) that a radio station used, rather than its frequency, the measure which is more commonly used today. In many cases the announced wavelength was slightly different from the one actually used. This was because the claimed wavelength was thought easier to remember or rhymed with the station's name (“Caroline on 199”, “...259” etc.). At a time when radios did not have digital displays, a precise figure was not considered important.