RAF Stoke Holy Cross Chain Home radar station

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Text © Copyright Evelyn Simak, December 2015
Images are under a separate Creative Commons Licence.


TF4812 : The Fenland and West Norfolk Aviation Museum by Evelyn Simak

In an experiment conducted on 26 February 1935 in a field near Daventry it was demonstrated for the first time that it was possible to detect aircraft by radio, based on the principle that sufficient energy could be reflected so as to permit detection on a ground receiver. It was found that the volume of sky under surveillance is full of pulsed radio-frequency and that the pulses or echoes from all aircraft could be received at a ground station. The experiment resulted in a programme backed by the highest priority and aimed at designing, building and installing a chain of early warning systems located along the coastline of Great Britain. On 24th September 1937, just over eighteen months after the first experiment, conducted by Robert Watson-Watt and Arnold Wilkins, RAF Bawdsey in Suffolk became the first fully operational radar station in the world. The construction of key stations in the south-east of England followed and the stations were integrated into a vast reporting network as soon as they became operational. The original plan was that each station be given the choice of operating on any of four allocated spot frequencies in the band from 20 to 55 MHz. The method was initially called Radio Direction Finding (RDF).

Chain Home was the first radar to be organised into a complete air defence system and it was the first such system used in wartime operations. It did not rely on new radio techniques but was developed from the technology then available into a highly effective air defence system. The equipment used by Chain Home stations did not look like later radar equipment: the antennae did not rotate and the transmitting array consisted of fixed wires strung between 110 metres (360ft) high steel towers. These towers emitted a so-called floodlight beam of radio energy. The receiving array consisted of wooden towers of about 73 metres (240ft) height. Two directional antennas were arranged at right angles to each other. Operators manually adjusted a comparator device when trying to determine angle and elevation to the target. Initially the system was calibrated using mostly civilian Avro Rota autogyros making circular and radial tracks at fixed heights. By Easter 1939, 15 Chain Home stations were up and running and Chain Home went into a 24-hour watch system. A number of so-called buried reserves, intended to back up the Chain should the main station be disrupted by enemy action, had also been constructed.

The locations of radar sites had to fit specific criteria: they had to be situated well back from the coast to be clear of a possible attack from German shipping; a smooth slope between the station and the sea was required to provide good height finding and range finding abilities; the sites had to be accessible to heavy engineering works and the ground suitable for carrying heavy masts. All the station equipment, including the towers, was duplicated, with a station using only three of the eight towers at any one time. In the event of jamming, provision was made to change frequency, and the appropriate aerials were available on the spare towers.

In September 1944 some of the stations also started monitoring the launch of V2 rockets using specially developed Chain Home receivers codenamed 'Oswald'. Despite there being no defence against the V2 once it had been launched, 'Oswald' was able to provide Bomber Command with the location of the launch sites, which could then be attacked. The receivers comprised a film camera attached to the consoles and recording permanently the brief transient plots of the bombs. 'Oswald' consumed film at a rate of 28 to 56 centimetres (1-2 inches) per minute and was in continuous use. A similar system, codenamed 'Willie', used a camera running at 32 centimetres (12.5ft) per minute and was switched on upon the detection of a suspicious signal. Chain Home stations equipped with 'Oswald' included RAF Stoke Holy Cross, RAF Great Baddow (Essex), RAF Dunkirk (Kent) and RAF Swingate (near Dover in Kent).

By the end of the Second World War there were approximately 50 early warning AMES (Air Ministry Experimental Station) Type 1 (Chain Home) radar stations either in 24-hour operation or on standby, all using the same basic 'floodlighting/DF' principle but configured differently depending on their operational role. The closing down of radar stations started before the end of the war from a peak of 194 stations in 1944 with only 36 remaining by 1947, 29 of which being manned at full readiness.

The radar station at Stoke Holy Cross formed part of the national Chain Home radar network. It was constructed under a plan to expand the original network in 1937/38 and was operational by 1939. The transmitter site was located to the north of Stoke Road, the road linking Poringland and Stoke Holy Cross. The original concrete track leading to the technical compound's entrance is today known as Pine Loke. The site comprised four steel transmitting towers, originally arranged in a straight line and with a distance of approximately 60 metres between each. After tower 2 was damaged by an aircraft, the replacement tower was constructed about 40 metres to the north-east of it. These four-legged steel towers were reportedly designed to withstand bomb attacks and could remain standing even if one leg was blown away (at the Isle of Wight Chain Home station RAF Ventnor this did actually happen).

The only original tower still standing on the transmitter site is tower 4, the northeastern-most tower in a line of four. This tower is still in use and the Nissen hut which once housed monitoring equipment, and a small adjoining Plant Room, have survived beneath it. A bullet hole ripped into the tower's steel structure by a German aircraft's gun bears witness to the numerous attacks launched against the radar site during WW2. Tower 3 was dismantled in the mid-1960s. Tower 2 was left standing, albeit reduced in height, until 1991. It stood just north of the original tower 2 which in 1942 was hit by a German aircraft and so badly damaged that it had to be dismantled. Until its replacement in 1969 by a modern mast of stepped steel construction, owned by British Telecom (BT), the MoD and the GPO both had an array of microwave dishes and aerials mounted on tower 1, which stood at the opposite end of the line. In 1966 and for a short time only, tower 1 also carried a test aerial mounted at a height of about 22 metres (75ft) which was placed there by the nearby Decca Navigator station for the purpose of monitoring Decca signals. The tower's concrete plinths can still be seen in the fenced-off BT compound.


TG2502 : Radar tower, Upper Stoke by Evelyn Simak TG2502 : Bullet hole in tower 4 by Evelyn Simak TG2502 : Beneath tower 4 by Evelyn Simak

TG2502 : Huts beneath tower 4 by Evelyn Simak TG2502 : Nissen hut beneath tower 4 by Evelyn Simak TG2502 : The Plant Room by Evelyn Simak TG2502 : Nissen hut beneath tower 4 by Evelyn Simak TG2502 : Huts beneath tower 4 by Evelyn Simak


On 18 July 1942, a Blenheim IV aircraft from 18 Squadron, based at RAF Wattisham in Suffolk, crashed into one of the steel towers, tower 2, causing heavy damage to the structure and killing all on board: Pilot Officer Philip Henry Lowther (20), Sergeant George Bernard Crawford (21), Sergeant Kenneth Custance Ellis (32) and a civilian met assistant, Kenneth Thomas Tagg, aged 18. In their memory, local resident Derek Bales, who is living on the receiver site, had a commemorative plaque made which was affixed to one of the concreted plinths of this tower. For detailed information concerning this accident go to: LinkExternal link

The station was frequently attacked by enemy aircraft and during the night of 8/9 May 1942 one such attack lasted for nearly two hours. Both land mines and bombs were dropped and a bomb also fell onto the farmhouse of Octagon Farm, killing Lilian Mabel Spruce, the farmer's wife. She died on 9 May at The Lodge nursing home in Bowthorpe Road, Norwich, aged 32. Octagon House was never rebuilt, and across the B1332 road only Octagon Barn, now housing an ethical shop, has survived. One of the enemy aircraft, a Dornier 217E-4, was shot down by LAA (light anti aircraft) guns defending the radar station and crashed in a crop field near Green Farm in West Poringland, killing all on board. The remains of the four crewmen (Unteroffizier Albert Otterbach, Unteroffizier Matthias Speuser, Oberfeldwebel Rudolf Bucksch and Oberleutnant Werner Böllert) were buried together in one single grave in Earlham cemetery in Norwich.


TG2502 : RAF Stoke Holy Cross - memorial by Evelyn Simak TG2502 : RAF Stoke Holy Cross - memorial by Evelyn Simak TG2008 : German war grave in Earlham cemetery by Evelyn Simak


The by far largest structures on radar sites were the transmitter and receiver blocks, both fitted with duplicate sets of equipment. Built from brick and protected by high concrete blast walls and traverses of earth reaching nearly roof height, and with flat concrete roofs topped by a thick layer of shingle, the buildings were designed to withstand enemy bombing. One of the operators who served at RAF Stoke Holy Cross as a radio technician (he is known only by his civilian wireless call sign 'G2HCG') recalled that when on 21 March 1941 the transmitter block was hit by a German bomb which landed in the middle of the roof, the building survived undamaged, with the only problem encountered being the demountable transmitter valves lifting from their mountings and disrupting work for about an hour whilst the operators were busy reseating said valves and re-establishing the vacuum. On their next trip up to the top of the transmitter towers the maintenance crew found shingle from the transmitter block roof strewn all over the platforms.

The Stoke Holy Cross transmitter block is still in place but no longer accessible. In December 2004 its entrance was bricked up and the surrounding earth traverse was lowered in height to prevent children from climbing onto the roof. When operational, the building housed two T.3026 transmitters derived from a basic design by Metropolitan-Vickers for the short-wave station at Rugby.

A rectangular arrangement comprising three blast walls with one open end has survived a short distance to the south-west and adjacent to tower 2. The walls consist of poured concrete with brick shuttering and are 90 centimetres (three feet) thick and were originally protected by a traverse of earth. The ground level within, as well as the area in front of the open end are somewhat lower than the surrounding ground, facilitating easy vehicular access. Large pieces of concrete rubble have been dumped within this structure, the purpose of which has as yet to be confirmed. It has been suggested that the thick walls may have protected a vehicle containing monitoring equipment and used by the J-Watch. Following the installation of the Chain Home network, continuous research and experimentation was taking place to improve the quality and type of radars and it became necessary to monitor and record enemy radar transmissions with a view to overcome possible jamming by the Germans and to facilitate our own jamming. This resulted in the establishment of 100 Group RAF, which was equipped with both ground radar jammers and aircraft fitted jammers. The investigation part of this service was known as the J-Watch. A J-Watch unit is documented to have been stationed at Stoke Holy Cross. A similar structure of slightly smaller dimensions has also survived on the receiver site.

A concrete building with a single narrow entrance protected by high blast walls stands near the site's eastern perimeter, not far distant from the transmitter block. A number of round openings where ventilation pipes emerge can be seen in the north and south facing walls. In the Norfolk Heritage Explorer the building is described as being an underground structure which must surely be a mistake, as it stands more than two metres high. The entrance, which faces away from the compound, is now completely filled in with earth, making access impossible. Weeds and shrubs are growing on the roof. It has been suggested that the structure was an electricity sub-station but this has as yet to be verified. Although most stations were powered from the National Grid they were also provided with generators, housed in a standby set building, to cover interruptions in the mains electricity supply. The standby set house however has not survived. Other buildings found on Chain Home radar sites include AMWD stores, petrol stores, armouries, incinerators and switch houses.

The Warden's house was situated beside the entrance into the transmitter site at the end of Pine Loke. It is still in place and has since been converted into a pair of semi-detached private dwellings, one still being called "Wardens". After the war, the house accommodated the station's commanding officer and his family. The four Air Ministry pillboxes once guarding the transmitter site's perimeter were demolished in the 1970s.


TG2502 : RAF Stoke Holy Cross - the warden's house by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the warden's house by Evelyn Simak

TG2502 : RAF Stoke Holy Cross - transmitter block by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter block by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter block by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak

TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - transmitter site by Evelyn Simak


The wooden receiver towers and associated buildings were located in a separate compound about 400 metres further to the west and hence truly bi-static. The receiver site was spread out along the west side of Chandler Road, which is named after the Reverend William Chandler, the local vicar who during the war also served as an air raid warden and after the war created a local bomb map, recording the location of every enemy bomb dropped in the vicinity. The four receiving towers carried an array of antennae, three stacks with one placed above the other, and were arranged in a rhombic formation. They were constructed from timber in order to avoid influencing the balance and symmetry of the receiver dipole stacks by the proximity of any metallic parts. Like the steel towers on the transmitter site they had servicing platforms placed at regular intervals which were accessed by a central ladder arrangement. The receiver site is now a private property. The buildings that have survived here include the receiver block, protected by the original earthen traverse; a workshop dating from 1947 which has since been converted into a private dwelling; and the IFF (Identification Friend or Foe) hut. The static water tank near the entrance, a short distance to the south-west of the guardhouse, has also been retained.

A rectangular arrangement of blast walls, presumably a vehicle shelter, stands adjacent to the southern-most tower. Its floor originally consisted of packed earth but was concreted when the structure was roofed over and converted into a shed after the war. A band of slight discolouration in the red brick about two metres up suggests the existence of a narrow ledge of unknown material, approximately eight centimetres (3.15in) in height and ten centimetres (3.95in) in depth and extending along the whole length of each of the side walls. It was supported by 10 centimetres (4in) long sections of steel set into the brick at regular intervals and which have since been removed. The empty sockets can however still clearly be seen.


TG2502 : Entrance to the former radar station by Evelyn Simak TG2502 : RAF Stoke Holy Cross - receiver site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - receiver site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - receiver site by Evelyn Simak TG2502 : RAF Stoke Holy Cross - receiver site by Evelyn Simak


During the time the station was operational, the receiver site entrance was protected by a guardhouse which is also still in place and has since been transformed into a small museum by the current owner, Derek Bales, who over many years has collected an impressive amount of information, photographs and locally found wartime artefacts, some of which are on display. The museum is open by appointment only, and upon request Derek is also happy to show interested visitors around the receiver site which is now a private property.


TG2502 : Buildings at the former radar station by Evelyn Simak TG2502 : Plaque on former guardhouse by Evelyn Simak TG2502 : RAF Stoke Holy Cross museum display by Evelyn Simak TG2502 : RAF Stoke Holy Cross museum display by Evelyn Simak TG2502 : RAF Stoke Holy Cross museum display by Evelyn Simak


The largest building on the receiver site is the brick-built receiver block, constructed to similar specification as the transmitter block although slightly shorter. It housed two receiver consoles designed and manufactured by AC Cossor Ltd to a TRE specification. The structure, nestled within its protective earthen traverse and concrete blast walls, comprises a number of rooms including a lobby, an air conditioning plant room, a private branch exchange (PBX), a transformer cubicle, a sub-station, a workshop and the main receiver or control room as well as a small wash room with adjacent toilet which was shared by male and female personnel. The rooms contain many of the original features, fixtures and fittings including switch and fuse boxes, light fittings, levers and shelves. The control room has been stripped of equipment but retains its electrical wiring racks suspended from the ceiling as well as much of its switchgear and cable hangers. In the GPO frame room the original light fittings and cable hangers can be seen and at the far end of the building the receiver power distribution equipment has survived in a small tiled room, appearing externally complete with dials and switches still in place but much of the inside has in fact been removed. The cable feeds were accommodated below floor level and emerged from the building through an opening at ground level. From here the cables were laid above ground, channelled and protected within low brick walls, and finally connected with the receiving towers.


TG2502 : RAF Stoke Holy Cross - the receiver block by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block by Evelyn Simak TG2502 : Receiver block at the former RAF Stoke Holy Cross radar station by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block by Evelyn Simak

TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak

TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak TG2502 : RAF Stoke Holy Cross - the receiver block (interior) by Evelyn Simak


The station closed down in 1956 and the wooden radar towers were dismantled. Dawson's of Hellesdon purchased the timber, of which a small collection was rescued and is now stored in the receiver block, as is one of the original wooden ladders. The concrete plinths of three of the wooden towers can also still be found on the site, which is surrounded by the original security fence, shot through in places by the guns of attacking enemy aircraft.

KML

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