Radio 390 was named after the station's wavelength in metres, so listeners would know where to tune. The actual wavelength was 388 metres (773 kHz), but 390 was easier to remember and close enough for tuning.
Like its neighbour Radio City, Radio 390 took advantage of the fort's layout by erecting a 250-foot vertical mast on an inner tower, guyed to three of the outer towers. This, with the additional elevation provided by the height of the towers themselves, gave it a stable and efficient antenna, more than on ship-based stations, ensuring good coverage of southern England with only a 10 kilowatttransmitter. For the benefit of advertisers, the station claimed a power of 35 kilowatts.
The station's easy listening format was innovative but criticised by rival Britain Radio as "stone age radio - a series of segmented dirges".
An episode of Patrick McGoohan's "Danger Man" (known in the U.S. as "Secret Agent") called "The Not-So-Jolly Roger" was filmed on Red Sands Fort in early 1966 when "Radio 390" was broadcasting (shut down a year later). The episode was broadcast on 4 July of the same year.