Anthorn Radio Station

Anthorn Radio Station is a naval and government radio transmitting station located near Anthorn, Cumbria, England, overlooking the Solway Firth, and is operated by Babcock International (with whom former operators VT Communications are now merged). It has three transmitters: one VLF, one LF, and an eLoran transmitter. It is on the site of the Royal Navy's Second World War military airbase, commissioned as HMS Nuthatch and which was operated by the Fleet Air Arm. RNAS Anthorn John Laing & Son began building an airfield at Anthorn for the Fleet Air Arm in late 1943, and Royal Naval Air Station, Anthorn, was commissioned as HMS Nuthatch on 7 September 1944, with three tarmacadam runways. It was the base of No. 1 Aircraft Receipt and Despatch Unit (No. 1 ARDU), which had the job of receiving aircraft fresh from manufacturers, modifying them to Service standards and despatching them to operational squadrons, with the unit specialising in the Vought F4U Corsair, Supermarine Seafire, Fairey Barracuda and Fairey Firefly types. No. 1 ARDU continued to operate from Anthorn following the end of the Second World War, while a number of Fleet Air Arm Squadrons were also based at the airfield in the immediate post war years. The airbase shut down in March 1958. The present road to Cardurnock runs partially along the airfield perimeter track. Several firing butts, for synchronising aircraft machine guns, can still be seen on the seaward side of the road. VLF transmitter The VLF transmitter is used primarily for orders to submarines, and transmits on 19.6 kHz with an output power of 550 kilowatts. Its callsign is GQD. VLF transmissions are relatively unaffected by atmospheric nuclear explosions, and Anthorn was once part of the link between Fylingdales early warning radar, North Yorkshire, and the United States' air defence system. A large part of the site is taken up by the VLF transmitter's large trideco wire umbrella antenna. This consists of a 748-foot (228 m) central mast with six vertical wire radiators suspended from its top, fed at the base of the mast, attached to six rhombic 2,148-foot (655 m) horizontal multiwire toploads radiating from the central mast at angles of 60° and supported by twelve surrounding masts; this arrangement gives the antenna the shape of a 6-pointed star when seen from above. The cables supporting the endpoints of the wire antenna carry a load of 31 tons, and are attached to computer controlled winches which automatically adjust their tension. The topload wires carry several hundred kilovolts during transmission, requiring long strings of insulators where they attach to the towers. The Anthorn station is a NATO facility, controlled from Northwood Headquarters along with three other VLF transmitters in Norway, Germany and Italy. In accordance with NATO procedure, the project was the subject of a competition among the organisation's member countries. The British Post Office, acting as technical adviser and agent of the Ministry of Defence, chose the site, negotiated the contract and supervised the work, with the assistance of the Ministry of Public Building and Works. The contract was placed on 26 October 1961 with Continental Electronics Systems Incorporated of Dallas, Texas. This firm had already built a similar but much larger station in Maine, USA. Work began in 1962 and the station was accepted on behalf of the MoD in November 1964. Originally, the station was designed to radiate a single telegraph channel at up to 45.5 baud and at powers ranging from 50 kW at 16 kHz to 100 kW at 20 kHz. The carrier frequency was to be stable to one part in 108 over a month. Subsequently, the data rate was increased to 50 baud and the carrier stability improved. LF transmitter: National Physical Laboratory time signal The National Physical Laboratory (NPL) installed three atomic clocks at Anthorn, and on 27 February 2007 Britain's national time signal transmissions, retaining their original call sign of MSF, were transferred there on a trial basis; the transfer was formalized on 1 April 2007. (The previous transmitter was at Rugby, and administered by BT.) The data transmitted includes time and date information which can be decoded using readily available software, and the signals are transmitted at an accurate frequency of 60 kHz to provide a national frequency standard. The transmitting aerial uses an auxiliary mast adjacent to the VLF array. Monitoring and logging of the clocks and control of the transmissions is by Internet link from the NPL offices at Teddington in west London, using comparison with GPS signals at both locations. Signal monitoring is by radio. To ensure accuracy, dynamic adjustment of the aerial according to local conditions (such as wind distortion) is controlled from computers on site. The effective radiated power is 17 kW. LORAN In 2007, the general lighthouse authorities for Britain and Ireland contracted VT Communications to develop an eLoran (enhanced LORAN) radio navigational aid for mariners; the transmitter is at Anthorn, and uses an auxiliary mast adjacent to the VLF array. Due to the closure of eLoran services in Germany and Norway, the eLoran service at Anthorn was discontinued on 31 December 2015. However, the eLoran timing signal is still active to allow for research and support. See also Rugby radio station References Sources Delve, Ken (2006). The Military Airfields of Britain: Northern England: Co. Durham, Cumbria, Isle of Man, Lancashire, Merseyside, Manchester, Northumberland, Tyne & Wear, Yorkshire. Ramsbury, Wiltshire, UK: The Crowood Press. ISBN 1-86126-809-2. Ritchie, Berry (1997). The Good Builder: The John Laing Story. James & James. Smith, David J. (1981). Action Stations: 3: Military airfields of Wales and the North-West. Cambridge, UK: Patrick Stephens. ISBN 0-85059-485-5. External links Russell W. Barnes' page about the wartime history Pictures of Anthorn Information on MSF relocation to Anthorn Press release about MSF relocation to Anthorn The Transmission Gallery: Anthorn