Rugby VLF transmitter

The Rugby VLF transmitter is a large VLF transmission facility near the town of Rugby, Warwickshire in England. It went in service at January 1, 1926 and was originally used to transmit telegraph messages to the Commonwealth. After the 1950s this transmitter, active as callsign GBR (short for Great Britain) on 16 kHz, was used for transmitting messages to submerged submarines. Around 1930, a second transmitter was installed for transatlantic telephony on 60 kHz using the carrierless single-sideband modulation. This transmitter went out of service in 1956 and transformed to the time signal transmitter MSF. This new function (and the "MSF" callsign now commonly used) developed from the decision, in 1951, to use the station to transmit modulated standard frequencies for scientific reference purposes. In 1972 these transmissions were consolidated onto the present frequency of 60 kHz and a further reference, that of a time signal, was added. In 1977 this took the form of the rolling slow code in use today.

The GBR transmitter was shutdown on April 1, 2003 after the Royal Navy didn't renew their contract with BT in favour of a new contract with VT Communications. On 1 April 2007 BT’s contract to transmit the MSF time signal will also pass to VT Communications, who will use their Anthorn transmitter, Cumbria.

- Wikipedia