Frequencies
The reason for choosing BBC Radio 4 for the Shipping Forecast is not because it is a mainly speech-based channel, but because it broadcasts via longwave on 198 kHz as well as FM, and the longwave signal can be received clearly at sea all around the British Isles regardless of time of day or radio conditions. For the same reason, the Shipping Forecast was broadcast in the BBC National Programme until September 1939, and then after the Second World War on the BBC Light Programme (later BBC Radio 2) until November 1978: these services all being broadcast on longwave (200 kHz). When BBC Radio 4 took over the longwave frequency from Radio 2 on 23 November 1978, the Shipping Forecast "moved" to Radio 4 – although in fact it stayed just where it always had been, on the long wave. The frequency changed slightly to 198 kHz in 1989 when the frequencies of all LF and MF broadcast stations across Europe were adjusted under the reorganisation agreed in the Geneva Frequency Plan of 1975.
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