Anthorn Radio Station
|Mast height||227 metres (745 ft)|
The Military Airfields of Britain: Northern England
Anthorn Radio Station is 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.
John Laing & Son began building an airfield at Anthorn for the Fleet Air Arm in late 1943, and Royal Naval Air Station, Anthorn, commissioned as HMS Nuthatch on 7 September 1944, with three tarmac 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 Firefly, Barracuda. 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.
|No. 1 ARDU||-||7 September 1944||November 1957|
|772 Naval Air Squadron||Various||3 May 1946||26 June 1947|
|802 Naval Air Squadron||de Havilland Sea Hornet||May 1948||October 1948|
|813 Naval Air Squadron||Blackburn Firebrand||21 May 1948||23 October 1948|
|801 Naval Air Squadron||Hawker Sea Fury||6 October 1949||31 October 1949|
|812 Naval Air Squadron||Fairey Firefly||4 June 1952||3 July 1952|
|807 Naval Air Squadron||Hawker Sea Hawk||14 January 1954||5 May 1954|
|860 Squadron Netherlands Naval Aviation Service||Hawker Sea Hawk||1956|||
|824 Naval Air Squadron|
The VLF transmitter is used primarily for transmitting 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 triatic wire umbrella antenna. This consists of a 748 feet (228 m) central mast with 6 vertical wire radiators suspended from its top fed at the base of the mast, attached to 6 rhombic-shaped 2148 ft long horizontal multiwire toploads which radiate from the central mast at angles of 60°, supported by 12 surrounding masts, giving 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 the tension. The high voltage of several hundred kilovolts on the topload wires during transmission requires long strings of insulators where the wires are attached to the towers.
It is a NATO facility, controlled from Northwood Headquarters along with three other VLF transmitters in Norway, Germany and Italy. In accordance with the procedure for NATO projects, 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) has 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, moving formally on 1 April 2007. The signals originally came from the transmitter located at Rugby, administered by BT. The data transmitted includes both time and date information and can be decoded using suitable software readily available.
Monitoring and logging of the clocks and control of the transmissions is by Internet link from the NPL offices at Teddington, 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 signals, transmitted at 60 kHz, also provide a national frequency standard. The effective radiated power is 17 kW.
The antenna system consists of thirteen masts, each 227 metres (745 ft) tall, which are arranged in two rings around the central mast. The VLF antenna consists of four rhombic antennas hung on large insulators on the masts, which are all grounded.
The LF antenna is a T-antenna spun between two masts.
- Delve 2006, pp. 33–35.
- Ritchie, p. 103
- Smith 1981, p. 37.
- "High power VLF radio station for NATO". The Radio and Electronic Engineer. January 1965. Retrieved 20 August 2019. reprinted on IEEE website
- van Horn, Larry (2009). Shortwave Directory. Brasstown, NC: Monitoring Times. p. 208. ISBN 978-0-944543-00-9.
- Laurie, Peter (30 May 1974). "No room in the radio spectrum". New Scientist. 62 (900): 533.
- John Ainslie (October 2005). "The Future of the British Bomb" (PDF). Clydeside Press. Archived from the original (PDF) on 6 July 2006.
- L.L. Hall (July 1965). "Anthorn Very-Low-Frequency Radio Station". The Post Office Electrical Engineers' Journal. Institution of Post Office Electrical Engineers. 58 (2): 114–118.
- "MSF Radio Time Signal". National Physical Laboratory. 29 March 2012. Archived from the original on 11 February 2012. Retrieved 3 April 2012.
- "The GLAs award a 15-year eLoran contract to VT Communications". Trinity House. 31 May 2007. Archived from the original on 23 April 2008. Retrieved 9 January 2008.
- 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.