Chain Home Stations

Radar and Chain Home:	What it was and how the system worked
Chain Home Stations:	Bawdsey • Bromley • Canewdon • Dunkirk • HighStreet • Pevensey • Rye • Ventnor
Chain Home Low Stations:	Beachy Head • Dover • Dunwich • Fairlight • Foreness • Poling • Truleigh • Walton

Radar and Chain Home

Sometime during January 1935, the Director of Research at the Air Ministry, H.E. Wimperis, approached the Superintendent of the Radio Research Station of the National Physical Laboratory, Robert Watson Watt, to enquire whether or not it would be possible to incapacitate an enemy aircraft or its crew by means of an intense beam of radio waves.

Radar was developed in great secrecy, and from 1937 to 1939, it developed into the core of the world's first integrated Air Defence System known as Chain Home. This consisted of twenty-one 300-foot masts sited along the east coast of Britain, its coverage stretched from the Isle of Wight to the Scottish border, forming a net of radar defence, supported by Chain Low Stations, which were able to detect low flying aircraft.

Experiments were carried out that were totally unsuccessful because the radio power in the beam would have to be thousands and thousands of kilowatts, wildly in excess of anything which could be generated at that time. Quite apart from this difficulty, as Watson Watt went on to point out, if the aircraft were made of metal then the engine and the crew would be totally shielded from such a beam. One discovery from the experiment, however, was that the scope showed an anomoly - a peak. It was found that an aircraft that had flown across the beam, and this was the visual interpretation of it - and so marked the beginning of radar - the ability to detect (enemy) aircraft in advance and direct aircraft to intercept them.

How it worked:

Radio signals sent out from these masts bounced back from objects in the sky, and would be picked up by receivers at Radar Stations.

The information appeared as blips on a cathode ray tube. These blips were then interpreted to give the distance, direction, height and numbers of the approcahing objects. A system was worked out for this data to be phoned through to RAF Fighter Command Headquarters at Bentley Priory in Stanmore, just outside London. There, it would be assessed, and information of an approaching raid would be passed to Fighter Command Operations Room, where controllers would alert the nearest RAF airfields. The development of Ground Controlled Interception made it possible for fighters to be guided towards them. Chain Home allowed the RAF to win the Battle of Britain and ensured that radar would play a major role in future air defence systems.

On occasions in 1939 and again in 1941 before the Battle of Britain, stations on the CH chain had detected unusual echoes approaching the English Coast that were reported to wartime Filter Rooms and RAF Fighter Command. On several occasions fighters equipped with early versions of airborne radar were scrambled to investigate but nothing was found and the phenomena were attributed to anomalous propagation or “unusual atmospheric conditions". As Britain was fighting a war no in-depth investigation of the reports was made by the scientific staff, but the Air Ministry were becoming aware that the radars which helped to defend the British coast were prone to AP and other spurious returns nick-named ‘angels’ which could on occasion be interpreted as intruder aircraft.

The Chain Home stations were designed to operate at 20-50 MHz although typical operations were at 20-30 MHz, or about a 12 metre wavelength. The availability of multiple operating frequencies gave some protection from jamming. The detection range was typically 120 miles, but could be better.
The Chain Home Low stations operated at 200 MHz, or about a 1.5 metre wavelengh. Technically, they were not closely related to Chain Home, and they employed a rotating antenna.

At the end of the war the Chain Home was largely mothballed and with power shortages only the GCI stations remained active, mainly in daylight hours. Once or twice per month the system was switched on for a time during the evening for ‘Bullseye’ training exercises organised by Bomber Command. These involved convoys of lumbering wartime bombers flying south from their bases in Lincolnshire and Yorkshire. On reaching the coast they would cross the North Sea towards the Low Countries as the GCI’s guided fighters onto their tails to simulate ‘live’ interceptions.

Chain Home Stations

During the battle, Chain Home stations, and most notably the one at Ventnor, Isle of Wight, were attacked a number of times between 12 and 18 August, 1940. On one occasion a section of the radar chain in Kent, including the Dover CH, was put out of action by a lucky hit on the power grid. However, though the wooden huts housing the radar equipment were damaged, the towers survived owing to their open steel girder construction. Because the towers were untoppled and the signals soon restored, the Luftwaffe concluded the stations were too difficult to damage by bombing and so left them alone for the rest of the war. Had the Luftwaffe realised just how essential the radar stations were to British air defences, it is likely that they would have gone all out to destroy them

RAF BAWDSEY Top

This is the station where Robert Watson-Watt developed his ideas for using Radar as an air defence tool. There were two or three U.S. built AN/FPS-6 height finding radars at Bawdsey and the tower for a Type 54 "Chain Home Extra Low" (CHEL) radar. Bawdsey Manor, estate buildings and 168 acres of land were sold to the Air Ministry in 1936. In January 1937 the RAF's Radio Direction Finding (RDF) training school was established there and the first Chain Home radar station was developed on the site, coming on line in May 1937. The station was fully operational by 24th September 1937 providing long range early warning for the southern North Sea and the Channel approaches, as well as radar coverage for coastal convoys. As well as research for the Air Ministry, a War Department (army) Team was working on the development of gun-laying radar that would enable anti-aircraft guns to fire accurately with poor visibility.

By 1939 acceptable gun-ranging equipment was in service with an accuracy of 25 yards at a range of 10 miles.

Another important area of research was the development of an 'Identification, Friend or Foe' (IFF) system allowing friendly aircraft to be differentiated from hostile planes. As a result of this research, aircraft were fitted with aerials incorporating motor-driven tuners that caused the reflected signal received by ground radar stations to vary in amplitude. Later models employed an electronic unit that detected the presence of friendly radar and then transmitted a coded signal causing the ground radar display to indicate a friendly aircraft.

This installation was taken over by the RAF on 7th December 1942 making Bawdsey the only site in the UK with three types of radar (CH, CHL and CD) in operation.

RAF BROMLEY Top

Bromley provided long range early warning for the eastern approaches to the Thames estuary.

RAF CANEWDON Top

Canewdon was one of the first Chain Home Stations, and was one of five to track Prime Minister Neville Chamberlain’s flight to Munich in September 1938. It's situte provided long range early warning for the Thames estuary and the north eastern approaches to London.

The site was developed in secrecy during the 1930s and was split into two halves, the receivers set in earth-covered concrete bunkers a few hundred yards north of the transmitters, which were in a compound south of Gardiners Lane. The transmitters were 360 foot high - dominating the skyline above the small village (It also held a type 700 Radar which opened in 1937).
This made it, just like the airfield at Rochford, particularly vulnerable to an airborne attack. There were at least twenty-one pillboxes constructed in an area of less than one square mile, guarding both parts of the site with inter-locking fields of fire from their loopholes.

Not too much of the original radar station remains. The receiver site has been completely cleared and the site is now an open field. No one would ever know that momentous events were once tracked from here. Three hundred yards to the south, the bunkers which held the transmitters are still there.
The huge 360 ft steel towers are gone, although their base plates remain. However, one of the towers did escape the oxy-acetylene cutter. It was moved to Marconi at Great Baddow in the 1950s and now stands high above the Chelmsford skyline.

On 6th September, 1939, a technical fault at the RDF station at Canewdon, compounded by a series of mistakes within RAF Fighter Command's fighter control system, led to friendly aircraft being plotted as an incoming raid. No. 56 Squadron (Hawker Hurricanes) were scrambled to intercept this 'phantom' raid, only to be plotted as hostile in their turn. Further squadrons were now scrambled and, tragically, a section of 72 Squadron (Supermarine Spitfires) misidentified two Hurricanes of 56 Squadron as Messerschmitt Bf 109's and shot both of them down, one pilot (Pilot Officer M. L. Hulton-Harrop) being killed. 'The Battle of Barking Creek', as the events of 6th September were later to become known, led to a wholesale review of RAF Fighter Command's plotting system.

RAF DUNKIRK Top

RAF Dunkirk took part in the pre-war exercises by Fighter Command, having been handed over to it in July 1937. In 1938 RAF Dunkirk went onto the alert during the Munich crisis and was kept at readiness right up to the outbreak of war. After the war Dunkirk radar was placed on care and maintenance and in the early 1950's RAF Dunkirk was one of 15 stations selected under the ROTOR programme as a 'readiness chain home'. With introduction of Type 80 radar in 1955 RAF Dunkirk was redundant and closed. Three of the transmitter towers were demolished and sold for scrap in 1959. The wooden receiver towers were dismantled and sold for re-use elsewhere. The remaining transmitter tower remained in RAF hands and is currently used for microwave communications by the US Airforce so RAF Dunkirk is still an operational station.

As a result of bombing during the Battle of Britain the original wooden operations buildings were replaced by new protected technical blocks which were built on the surface of brick with a six foot thick shingle cap for added roof protection and surrounded by an earth traverse.
Dunkirk provided long range early warning for the Thames estuary and the south eastern approaches to London.

RAF HIGH STREET Top

RAF High Street Radar Station, situated in Darsham village off the A12 near Saxmundham, provided long range early warning for the southern North Sea and approaches to East Anglia. This station was the most powerful along the east coast owing to the distance between it and the Norwegian airfields, and the steel transmitter pylons stood 360 feet high and were of similar construction to those used at Bawdsey, and were destroyed in the 1960s. The height was primarily to counteract the curvature of the earth as it was not possible to bend signals over the horizon and there were no satellites to make use of at the time.

Attempts to obtain picture of this station through the Imperial War Museum in London, the RAF museum in Hendon and the Duxford museum were all unsuccessful. The response received was that no records exist of this station
- Ronald Ashford.

RAF PEVENSEY Top

RAF Pevensey covered a considerable area of the Pevensey Levels, now Pylon Farm. It was the worst site in the southern group as the whole area was flooded and the buildings were sited on silt subsoil and continuous pumping was needed during the construction.

The transmitters and receivers were housed in sandbagged wooden huts with 90' guyed wooden masts and a mobile generator. There were originally four transmitter towers but No.1 tower was later dismantled and re-erected in the far north. Pevensey faced south (line of shoot) for attack across France from Germany. It was in the right position for the Battle of Britain, and provided long range early warning for the south coast and Channel, looking over the raid assembly areas in northern France. As East Coast stations have only one channel, emergency mobile radars (MRU's) were positioned near each Chain Home station. That for Pevensey was at Chilley Farm to the south west.

RAF Pevensey was short lived, and the station, along with Rye, was not required for the post war Rotor Radar Programme, and were offered for sale by public auction in 1958. The transmitter block which was demolished in December 1987.

RAF RYE Top

RAF Rye provided long range early warning for the south coast and Channel, looking over the Cap Griz Nez area of northern France. As with Pevensey, it was not required post war for the Rotor Radar Programme.

RAF VENTNOR Top

RAF Ventnor was one of the 20 original Chain Home radar stations authorised in 1937 and the station first became operational in temporary hutting in late 1938.
While many Chain Home radar stations around the country closed at the end of the war, RAF Ventnor remained in use and in November 1947 it was one of only 26 operational radar stations in the UK. The entire station eventually went into care and maintenance. By 1950, the threat of the Atomic bomb had caused a serious rethink in the organisation of air defence and a plan was instituted to replace many of the existing stations with new protected underground operations rooms. RAF Ventnor was chosen to participate as part of that programme.

Ventnor provided long range early warning for the south coast, particularly for Southampton and Portsmouth.

On 16th August, 1940, Ventnor was successfully attacked by the Luftwaffe. Airfields were the primary targets of the Luftwaffe with West Maling, Tangmere, Westhampnet, Manston, Farnborough, Harwell, Brize Norton, Gosport, and Lee-on-Solent being hit.

Chain Home Low Stations

Operational experience showed that the Chain Home system had significant gaps in its low level cover and the 1938 R.A.F. exercises demonstrated that low-flying aircraft could escape detection completely.
In 1936 the War Office had established a small group at Bawdsey under Dr. E. T. Paris and Dr. A. B. Wood. This group had been working on gun-laying radar for antiaircraft guns and coastal defence radar for the direction of coastal artillery. The coastal defence equipment worked on the higher frequency of 180-210 MHz and the aerial comprised of a broadside 32 dipole array that produced a narrow beam in both azimuth and elevation. By July of 1939 the coastal defence set could detect an aircraft flying at 500 feet up to 25 miles away with very good accuracy and in August 1939, on Watson-Watt's recommendation, the Air Ministry ordered 24 coastal defence sets from Pye Radio with the intention of placing one at each CH site. These stations became known as Chain Home Low (CHL) stations and the equipment as Radar Type 2.

RAF BEACHY HEAD Top

RAF Beachy Head, the most southerly point on the chalk cliffs to the west of the town of Eastbourne, East Sussex, has a long history as a location for observation and warning, and was requisitioned for use by the RAF during the second world war, and who installed a Radar Station on the surrounding land. The radar itself was housed in a railway container on the cliff edge. Even with the Type 42 radar it was impossible to detect aircraft coming in at sea level until they were within ten miles of the station. This gave only a time lapse of three or four minutes for the radar operator to plot the intruders and pass the plots to the filter room at Stanmore for warnings to be dispatched to the local ARP authorities.

Beachy Head provided low level raid cover for the the south Channel coast between Brighton and Hastings.
(Photo of Beachy Head Guard House by Neal Harley)

RAF DOVER Top

Dover provided low level raid cover for the south Channel coast across the shortest crossing point of the Channel and for one of the busiest south coast ports.

RAF DUNWICH Top

Dunwich provided low level raid cover for the central East Anglian coast.

RAF FAIRLIGHT Top

RAF Fairlight Chain Home Low Radar Station was operational by September 1940. It was located on the north side of Fairlight Road to the west of Hastings.

A week after D Day (6th June 1944) the Doodlebug or 'Diver' campaign started and Fairlight was immediately upgraded to a reporting GCI station with the addition of Type 14, Type 24, Type 26 and an American MEW radar. A special tracking console was installed in its own building and extra accommodation was built for the new personnel which included a photographic section, 'Y' watch (technical analysis of radio signals), controllers, filterers, CME's (Civilian Mechanical Engineers), operators and clerks.

The whole site was surrounded by light and heavy anti-aircraft guns which were not conducive with quiet operational radar practices.
Fairlight provided low level raid cover for the south coast between Hastings and Rye. After the war, Fairlight was chosen to to participate in the ROTOR project as a Chain Home Extra Low, and the station was resited closer to the coast.

RAF FORENESS Top

In the summer of 1942 new radar equipment, known as Type 14, was issued to certain RDF stations in the southeast. At Foreness Point this equipment was completely mobile, being accommodated in a three-ton prime-mover caravanette with a trailer to house the transmitter and rotating parabolic aerial array. This Type 14 radar operated on the same frequency band as the German radar and had been designed so that changes in operating frequencies could be made in minutes rather than the half-hour or so required for older types of equipment. The idea behind this design was to thwart the increasing tendency the Germans had of trying to jam our radar. With Type 14 we could quickly change our frequency to that which the Germans were using themselves making it impossible for them to jam our radar without affecting their own equipment.
Foreness provided low level raid cover for the approaches to the Thames estuary and London.

RAF POLING Top

RAF Poling was one of the premier radar stations on the south coast plotting high flying enemy aircraft. The Pylons of the Royal Air Force Station (three x 360 ft. and four x 240 ft.) literally dominated the lie of the Sussex downland immediately to the rear of the Technical Site. After hostilities had ceased, Poling was one of only a few of the stations kept operational and was not shut down until long after the war.
The station provided low level raid cover for the south coast between Portsmouth and Brighton. (Photo: Valerie Martin, 2001)

RAF TRULEIGH Top

While the Poling pylons were there for all to see – including enemy pilots – few, apart from residents, were aware that another much less obvious but closely related radar station had been built at Truleigh Hill, at the back of Shoreham. Many Shoreham residents knew that RAF personnel were manning what they believed was “a minor aircraft spotting outpost” on nearby Truleigh Hill, because many of the personnel were billeted in local private homes. In the early stages of WWII, Truleigh Hill was manned by a handful of RAF personnel. At its peak there were nearly 200.

One of the few prominent surviving features of RAF Truleigh Hill is this brick-built bungalow, with veranda, that was designed to look like a normal British farmhouse. But not only was it an RAF guardroom, it also concealed the stairway entrance to a nuclear-proof bunker built 40 feet beneath the summit of the hill. At one time, six aerials of various sizes were dotted around the site.

Truleigh provided low level raid cover for the south coast in the Brighton area.

RAF WALTON Top

Walton provided low level raid cover for the northern approaches to the Thames estuary and London.