Radio 390 (1965–1967) was a pirate radio station on Red Sands Fort, (near Whitstable), a former Maunsell Fort on the Red Sands sandbar in the River Thames estuary.
Previously the fort had been used by Radio Invicta (c June 1964 – February 1965) and K-I-N-G Radio (March – September 1965). Neither was well-financed or successful, and KING approached Ted Allbeury, who suggested a format based on women's magazines to appeal to housewives.
Radio 390 was named after the station's wavelength, so listeners would know where to tune. The actual wavelength was 388 metres (773 kHz), but 390 was easier to remember. 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.