Transmitter site (excluding Tower 2), former Swingate Chain Home Radar Station, St. Margaret's at Cliffe, Kent

Summary

Transmitter site to the former Swingate Chain Home Station, 1936-8, comprising the transmitter building, and two transmitter tower bases. Also the late 1950s Tower 1 (on a 1930s base) and its associated hardened building and compound, and the remains of the Gee-H and Troposcatter buildings and fixings (also of late 1950s and 60s date).

Description

Swingate Radar Station is built on a prominent site above the cliffs about 2km to the north-east of Dover town, centred on grid reference TR 33680 43077. The site is large (approximately 21ha) and consists of a transmitter site, receiver site, and ancillary structures. The receiver site and buried reserves are separately listed, as is Tower 2 on the transmitter site.

TRANSMITTER SITE
The transmitter site is located in the south-west of the site at TR 33470 42884 and is enclosed within a rectangular fenced enclosure. As was common to all transmitter sites, the transmitter towers were constructed in a line and were of steel lattice on concrete footings. (The Swingate transmitter and receiver examples were all-self supporting and therefore are technically towers rather than masts: masts were used on west coast Chain Home sites and had to be supported by steel guy ropes.) The two northern towers remain (the southern of which - Tower 2 - is separately listed) and the bases of the two southern towers also survive. Historic photographs show all four in situ. Between Tower 2 and the site of Tower 3 is the transmitter building. Concrete footings for other former buildings and equipment bases are also visible, particularly in the southern part of the site between and to the east of the position of Towers 3 and 4.

TRANSMITTER BUILDING (TR 33486 42883)
This is a protected ‘A’ type transmitter block. It is a rectangular structure, approximately 24m long by 8m wide, and oriented west-east. The building is rendered externally but where the brickwork is visible it is in English bond. However, some internal walls are of Stretcher bond brickwork indicating later modifications to the layout, presumably of 1950s date. The building has a parapet concealing a flat roof. In common with other protected radar buildings of this era the parapet would have originally contained shingle to a depth of c1.7m as an anti-blast protection. This is presumed to survive and the roof is capped in concrete. Drainage holes through the parapet lead to cast iron rainwater goods.

The building is protected on all sides by an earth traverse. This is reveted externally by low yellow brick, English bond walls but internally by high concrete walls creating a covered way (a protected walkway) around the building. The compound is approached from the north and east where there are concrete blast wing-walls protecting the entrances. There are heavy external steel doors to the building, the main entrance being to the north with further doorways in the south and east elevations. In the northern and southern traverse, visible from the covered way, are two cooling fan outlet ducts with central concrete baffles. These are part of the original air conditioning arrangements, allowing air to circulate around the building (which would require temperature modification given the machinery operating inside) but would prevent debris coming into the system in the event of external blasts. Air conditioning extractor hoods are visible on the exterior of the building but are post-war when compared with the smaller scale and form of those to the receiver building.

Given the standardised plans of ‘A’ type transmitter blocks it is known that the Swingate building would originally have had a large transmitting room, a sub-station and workshop, ventilation plant room, gas lock to the entrance, a latrine and a private branch exchange (PBX). Internally the transmitter building now has two large rooms to the west (presumably the former transmitter room but now subdivided), the most westerly of which contains ceiling hung air conditioning ducts. Information provided by a former BBC employee as well as comparison with photographs of wartime ducting indicates that this is not original, but of 1950s date. The second room contains a covered sub-floor cable pit which would have housed the cables connecting the building to the transmitter towers. In this room are intake fan control panels made by Allen West & Co Ltd, Brighton, England. These are probably of 1950s date. In the centre of the building is an entrance lobby leading from the south door, off which are three small rooms including a kitchen (the former PBX) the former ventilation plant room and WC. The eastern part of the building (the former sub-station and workshop) has been modified by the insertion of partition walls in Stretcher bond. It has quarry tile floors and houses, in one room, a generator by Ruston and Hornsby Ltd, Lincoln, England. A parts list for this generator kept on site is dated February 1957 suggesting it is of 1950s vintage. Internal doors are of oak, as are the architraves, and some have peep-hole windows and metal handles. They are designed to allow for the compression of rubber door seals to prevent the egress of poison gas during an attack and are part of what is known as Passive Air Defence (PAD) measures. Although the building is of 1930s origin, its internal arrangements and fittings are now of 1950s and later date. The building remains in use by a commercial communications company and therefore also houses modern electronic and communications equipment.

TOWER 1 & HARDENED BUILDING (the USAF tower - TR 33453 42982)
This tower, of a steel lattice construction, is distinct from Tower 2 in its form and construction and does not conform to 1930s or Second World War Chain Home tower design (of which there were three designs nationally). It reuses the 1930s concrete bases however. The tower is believed to have been constructed in the late 1950s following the c1955 demolition of the original Group III tower although it has not been possible to confirm this. However, it is highly likely that the tower was re-built at the same time as the hardened compound described below, all part of the early Cold War modifications and use of the site in the 1950s. A modern pyramidal base mat has been added to the tower.

The tower is contained within a square compound with high reinforced concrete walls. Attached to the compound on its south side is a hardened rectangular flat-roofed building of reinforced concrete. Windows are protected by window-guards and hoods and doors are of heavy steel construction. This building was visible through the exterior security fence surrounding tower 1 but was not available for internal inspection. However, information and photographs provided by the MoD indicates that it has two rooms internally for housing electrical switch gear, one of which contains a shower cubicle. The smaller of the two rooms used to accommodate a stand-by generator, although this has been removed, as has all original plant throughout. The building appears to be of USAF era construction (recently demolished office and garages to the immediate east of the compound were painted in USAF cream and brown colours) and is integral to and contemporary with the compound wall.

TOWER BASES
The remains of the footings to Tower 3 (TR 33459 42847) and Tower 4 (TR 33462 42785) survive in the southern part of the transmitter site. In each case they comprise four reinforced sloping concrete feet which are again c3m2 by 2m tall.

ANCILLARY REMAINS
Building foundations and troposcatter fixings are located in the southern half of the transmitter site (TR 33462 42785) particularly along the eastern boundary. To the south-east of the transmitter building are the concrete footings of two broadly rectangular north-south oriented buildings. The ghosts of internal partition walls remain visible so that the layout can be understood. The northern of the two is marked on historic plans as the ‘terminal building’ this was probably the Gee-H building of 1950s and 60s date providing a radar/navigation system for Vulcan and Canberra bombers. To its north-east are the footings of its stand-by set-house and fuel catch pit. The southern building is the ‘tropo’ or troposcatter building for Ace High. There are also the foundations for the former troposcatter array. There are two groups of six small rectangular pads with metal fixings which supported the two large billboard reflectors. These were extant as recently as the mid-late 1980s but have since been demolished.

All modern plant and machinery, fixtures, fittings, communications equipment (including radio equipment cabins and electricity meter cabinets), masts, antennae (including associated brackets, supports and feeders) and the compound fences and gates are not of special interest.

History

The principles behind radar were widely recognised by the 1930s, but British technicians were the first to translate the science – that an electromagnetic pulse reflected from an object betrays that object’s position to a receiver – into a practical means of defence. Following experimental work at Orfordness and Bawdsey Research Station in Suffolk (which became the prototype site for the Chain Home Defence System and where different components are listed Grade II and II*), radar developed through the initial Home Chain, a small group of stations in the extreme south-east of the country, to Chain Home Low, which filled the gaps in low-looking cover left by the original technology. Both were designed for raid reporting, passing information to a central operations room which in turn directed fighters to intercept enemy aircraft. This system was to prove vital during the Battle of Britain. Radar was then adapted during the Blitz of 1940-1 to incorporate a system of Ground Controlled Interception by which night fighters were controlled directly by each station rather than via a central operations room. A further addition in 1941 was Coast Defence/Chain Home Low, a low-cover coastal radar designed to detect surface shipping. Many stations were converted to new and more powerful equipment in 1942, known as Chain Home Extra Low. Finally, in 1943, Fighter Direction radar was developed to aid Fighter Command in their offensive sweeps over occupied Europe. Many radar stations were reused during the Cold War period for Rotor, a Cold War re-engineering of wartime radar equipment.

Swingate Chain Home Radar Station (also sometimes referred to as Dover Radar Station) was one of the earliest of the initial Home Chain of which there were eventually 32 sites nationally. It is believed to be the second built nationally after the experimental prototype station at Bawdsey. Radar sites of this early pre-war period were essentially divided in two with one part of the site housing receiver functions and the other transmitter functions. The layout of the receiver and transmitter buildings relative to their towers was different and therefore aids identification. The receiver towers were arranged in a broadly square plan with the receiver building at the centre, whereas the towers of the transmitter site were arranged in a line. Information would be passed to Fighter Group HQ at RAF Bentley Priory where enemy aircraft locations were plotted and a response was co-ordinated. With a range of approximately 150 miles above the ‘radar horizon’, Chain Home stations were a vital part of the country’s defence.

Work began at Swingate in 1936 and although substantially complete by May 1937 was finally completed in the summer of 1938 as part of the first group of five radar stations nationally. These had been planned in 1935 and developed between 1936-8 and were known as the Estuary Chain Home group (the others being the aforementioned Bawdsey site in Suffolk and new sites at Great Bromley in Essex, Canewdon and Dunkirk in Kent.) Until the permanent site was ready, temporary equipment was installed. The site, in common with other radar stations, would also have had a building to house the stand-by generator set house protected by a traverse. At Swingate this is believed to be located at grid reference TR 33683 42878 where concrete footings or capping can just be observed through heavy undergrowth. However, the vegetation has precluded a firm identification at the present time. A guard-hut would also have been the norm: the Swingate guard hut was at the entrance to the receiver site but does not survive. The buried reserve, an addition to sites planned in late 1939 to allow them to function in the event that the main station was bombed and out of action, was operational at Swingate from July 1941. A further development was the installation of an Identification Friend or Foe system (IFF, developed in 1939) to allow the site to differentiate between friendly and enemy aircraft. This was located in a small cubicle on the receiver site. In common with other south-eastern stations Swingate came under Fighter Command’s strategically important 11 Group (a division of Fighter Command covering London and the south-east). It was identified by the War Office as Vulnerable Point No 125, a site vulnerable to enemy attack, and therefore defensive structures were added. Dobinson (2000, 160) records that the Light Anti-aircraft gun was in situ on the buried reserve site by May 1942 and that there were three others installed to protect the site. Swingate also became one of the Gee Chain navigation stations, using a development of radar equipment, working to improve the accuracy of bombing raids in the early 1940s.

Some sources erroneously suggest that the site housed equipment in early 1940 as part of the Chain Home Low system, allowing the detection of lower-flying aircraft than Chain Home could detect. In fact the nearest CHL station was at Fan Bay approximately ¾ mile to the south-east. (Confusion arises as the name 'Swingate' is sometimes used for the radar station, and sometimes to refer to the wider area.), and RAF Swingate would also have been the parent site to the CHL site. In 1944-5 the station was also provided with Cathode-ray direction-finding (CRDF) equipment to detect V2 missile launches (known as Operation Big Ben).

The Swingate towers were prominent on the coast and were investigated by the Graf Zeppelin II in 1938/9 and also inspected by Goering through binoculars while on a visit to France. Initially the Germans did not fully appreciate the significance and function of these new coastal structures. This changed on 12-13 August 1940 when the site and others along the south coast were attacked in an attempt by the Luftwaffe to disrupt transmissions and destroy them, as a part of the long-planned attack known as ‘Adlertag’ or ‘Eagle Day’. Radar stations were a key target with Swingate, Pevensey, Ventnor, Dunkirk and Rye all damaged to varying degrees. The bombing at Swingate damaged one of the towers as well as hutting on site, but operations continued albeit with some reliance on emergency equipment. Damage to radar stations allowed the Luftwaffe to successfully attack a number of key airfields in southern England such as Hawkinge, Manston, Eastchurch and Detling and they also attacked other military targets including an aircraft factory in Rochester. Swingate was attacked on numerous occasions during the war and a particularly atmospheric photograph survives showing it under shell attack on 29 April 1941.

The site was modified during the Cold War. Although sometimes recorded as being a Rotor site, the early warning system of the early 1950s, the new Rotor equipment was actually housed at St Margaret’s Bay (to the north-east of Swingate and now demolished), although Swingate’s re-engineered equipment was operational in the long-range early warning role as part of the wider Rotor plan. The radar station continued in use until 1955 when the Early Warning and Control radar at RAF Ash made the Swingate site redundant. The wooden receiver towers were demolished as were two of the transmitter site towers; Tower 4 and Tower 1, although the latter was rebuilt. The site housed a Gee-H navigation system between 1958 and 1970 largely for the English Electric Canberra equipped bomber stations and for V-force bombers in the late 1950s. In 1960, the site became part of NATO’s Ace-High international communication network, principally a means of linking NATO heads of state in a crisis. Historic photographs show the two large billboard reflectors of the tropospheric scatter communications network (part of the Ace-High system) at Swingate, located on the transmitter site. This was operational until the late 1980s when technological advances made it redundant. A Royal Observer Corps post was built here in 1962 and was operational until 1968. Its function was to identify evidence of nuclear attack and to monitor radiation. The transmitter site, particularly Tower 1 and its compound, were used by the United States Air Force (USAF) as a communications site for their English bases and European bases during the Cold War. The site has also provided communication for the Home Office, the BBC and for the Regional Seat of Government under Dover Castle, a joint civil-military headquarters bunker established in 1962 for use in a nuclear emergency.

Transmitter Tower 3 was demolished in March 2010. In 2012 parts of the transmitter site remain in use by a commercial communications company.

Reasons for Listing

The Transmitter site to the former Swingate Chain Home Station, 1936-8, comprising the transmitter building, and two transmitter tower bases; a late 1950s Tower 1 (on a late 1930s base) and its associated hardened building and compound; the remains of the Gee-H and Troposcatter buildings and fixings (of late 1950s and 60s date) are designated at Grade II for the following principal reasons:
* Architectural interest: a relatively intact example of a 1930s transmitter site with surviving principal building, three of its four mast bases (the fourth tower is separately listed), and additionally structures of the post-war era, evidence of developments in radar technologies during the Cold War;
* Early date: the second Chain Home Station to be built nationally (after the experimental station at Bawdsey in Suffolk) and thus a very early example nationally;
* Historic interest (history of radar): a physical manifestation of pre-war tensions and fears, anticipating the need for a national defence system which resulted in the construction of a chain of radar stations to protect Britain's coast. The Swingate site, given its proximity to and visibility from France, placed it firmly in the front-line of the country's defence;
* Historic interest (enemy attack): as one of the radar stations targeted by the Luftwaffe on 'Eagle Day' in August 1940;
* Group value: with the listed remains of the receiver site and buried reserve which collectively make up the Swingate Radar Station.

External Links

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