1970. RNI responded with pro-Conservative political messages for the general election on 18 June 1970. On 13 May 1970, RNI responded to complaints about interference by changing its MW channel to 1230 kHz (244 metres). This improved reception but was adjacent to the pop music service of BBC Radio One on 1214 kHz (247 metres). Jamming followed five days later, causing interference to BBC Radio as well as RNI, especially in Kent, south-east England. Radio Caroline International On 13 June 1970, five days before election day, Radio North Sea International changed to Radio Caroline International and launched a campaign in support of the Conservative party. The name change and political campaign were supported by Radio Caroline's founder Ronan O'Rahilly. Listeners were told that their freedom to listen to the radio station of their choice was under threat and that, if the Labour party were returned to power, the station would close: their vote should therefore be Conservative, the only party that supported commercial radio. O'Rahilly headed the campaign on land, using a double-decker bus and posters depicting Harold Wilson as China's Chairman Mao. They believed the Conservatives would end jamming. Conservative policy was to establish local land-based commercial radio in the UK. At a Fight for Free Radio rally the weekend before the election, Conservative loudspeaker-vans urged 'Vote Conservative and fight for free radio'. The Conservatives won and there is evidence that the Caroline and RNI campaigns made a difference to the result. Reversion to RNI Two days after the election, the station reverted to RNI. Because jamming continued, Mebo II returned to the Dutch coast on 23 July 1970. The British government jammed Mebo II's broadcasts with tones, usually an 800 Hz heterodyne supplemented with a pulsed beep (whistle and "pip pip"). Norway's interference with RNI on 6215.0 kHz was explained thus: This is a transmission from the Norwegian coast station Rogaland Radio operating in single side band mode, upper side band, with a carrier frequency of 6215.0 kHz. The purpose of this transmission is to clear the channel of unauthorised and out of band broadcasting, to improve reception conditions for ships wishing to communicate with coast stations on this frequency or on adjacent maritime channels. Paul Harris's book Broadcasting from the High Seas, published in 1976, suggests the UK government suspected RNI's shortwave equipment was sending coded messages to unfriendly countries, in particular the German Democratic Republic (GDR).