5XX

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5XX was a British experimental longwave radio station. The station achieved near-national coverage via its broadcasts from the Daventry transmitting station, which opened on 27 July 1925.{{cite web |title=History of the BBC - Daventry Transmitter opens providing national radio coverage - 27 July 1925 |url=https://www.bbc.com/historyofthebbc/anniversaries/july/daventry-transmitter-opens |publisher=BBC Online |access-date=11 March 2025}} It was dedicated for national transmissions, established at the Marconi Company's New Street Works Factory in Chelmsford. It set the bases for the BBC National Programme, which was the station that replaced it on 9 March 1930.