Air Commodore Keith Park, Air Marshall Dowding’s Senior Air Staff Officer (SASO) was delegated the job of siting the RAF’s radar stations on the Isle of Man. He was later Air Vice-Marshall and AOC at 11 Group, responsible for Battle of Britain from the underground headquarters at RAF Uxbridge.
Discarding scientific advice from Bawdsey to site a Chain Home station on the summit of Snaefell, Park preferred the option of two Chain Home stations, one at the north end of the island and the other to the south.
The sites selected early in 1940 were Bride at the north (SC463031) and Scarlett to the south. Both sites were designated Advance Chain Home (ACH) installations being brought on line with temporary shorter timber masts to support the transmitter arrays, pending the availability of standard ‘west coast’ 325 foot guyed steel masts. Both stations were in use by September 1940.
Subsequently, Bride was found to be surplus to requirements being covered from Scotland and Ireland to the north and by 1942 it had been closed and stripped of equipment. Scarlett did not last much longer.
The three CH stations on the Isle of Man were very similar. The main differences were that Bride and Dalby each had two Type C transmitter blocks and two Type C receiver blocks, whereas Scarlett had one pair of Type C transmitter and receiver blocks and one pair of the earlier Type B transmitter and receiver blocks. This indicates that planning for Scarlett started earlier than for the other two chain home stations. The Type B blocks were designed to accommodate two sets of equipment in a larger brick building with a concrete roof surrounded by a separate concrete blast wall. Before many of these buildings had been built, it was realised that it would be more sensible to disperse the equipment and therefore later stations had the two pairs of Type C buildings, each with one set of equipment. The few stations with the Type B blocks were therefore provided with an additional Type C receiver block and a Type C transmitter block.
The Chain Home radar station at Bride was established on farmland to the southwest of the Point of Ayre Lighthouse in 1941. This station was also known as A.M.E.S. No. 62.
In 1944 Bride and the aerials, masts and towers were dismantled and removed soon after the end of the war but some concrete bases and stubs remain in the ground. The equipment was removed. Most of the technical blocks and some associated artefacts are still intact, although many of the brick buildings (e.g. accommodation blocks and cookhouse for the guards) have been demolished. Some of smaller steel and concrete components of the transmitting aerial systems have been dug up, presumably to increase the usable area of the fields, and moved to another area or placed at the field boundary. Some of these concrete blocks have been used to prevent access to technical blocks.
Nineteen sites that formed part of Bride have been identified. At present only one receiver block and one set of receiving aerial stubs are to be seen on the ground. Duplicate sets of receiver blocks and receiving aerials were planned for Bride. Aerial photographs were therefore studied to locate the missing structures. In these photographs, a receiver block and a receiving aerial tower are clearly visible in the field immediately to the north of the intact receiver block and set of receiving aerial tower stubs.
The northern receiver block was buried, probably during recent landfill operations, but the two southern corners of the concrete roof are still visible and the length of the building matches that of the intact southern receiver block. At the present time, there are no signs of the northern receiving aerial tower stubs.
The stubs and cable junction box of the northern receiving aerial tower appear to have been destroyed and/or buried at the time this field was used by the Government as a landfill site.
The remaining receiver block is in good condition, but access is difficult because the entrances had been closed by blocks of concrete, probably from another part of the station.
The receiver block housed receiving equipment which presented a display to the operator, usually WAAF, on a CRT. The distance between the start of the trace and the vertical blip indicated the distance of the target from the station. The magnitude of the blip indicated the number of aircraft (raid strength). The bearing of the target was determined by comparing the signals received by two dipole aerials (N-S and E-W) mounted horizontally at right angles in the receiving aerial mast. The comparison was made by adjusting the calibrated knob of a goniometer to minimise the height of the echo on the CRT.
The goniometer had two stator coils at right angles, each of which was fed with the signal from the corresponding dipole aerial, and a search coil was connected to the calibrated knob.
These stator coils recreated in the goniometer the radio field that prevailed at the receiving aerials. The bearing of the target was determined by rotating the search coil for a maximum signal on the CRT (in practice operators found that more precision was obtained by searching for a minimum signal and correcting by 90 degrees).
Two receiving aerial systems were used to determine the angle of elevation. One system was designed to give maximum signal at a high angle of elevation and the other was designed to give maximum signal at a low angle of elevation. By comparing the two signals and taking account of the curvature of the earth it was possible to calculate the elevation of the target aircraft [28]. In order to take account of the local terrain, height curves were plotted from aircraft making calibration flights and these were used to convert elevation to altitude.
Soon the calculation of altitude was made automatically by racks of electromechanical equipment (Figure 16) which also stored the calibration data. This equipment was designed by the Post Office Research Station at Dollis Hill. Relays and uniselectors in the calculator allowed the grid reference and the raid strength of the target to be stored.
It is not possible to identify the original locations of all these pieces of equipment because at the time of writing no drawings or photographs have been located which show the equipment in use in a Type C receiver block.
The receiving aerial towers were constructed from wood and each of the four legs was bolted to galvanised steel stubs set in massive concrete block foundations. All that now remains on the site are the receiving aerial cable junction box and the four steel stubs for the wooden legs of the tower.
The transmitter block was constructed from reinforced concrete. Two pairs of transmission lines, probably running along the hedge boundary, carried high voltage radio frequency power to the two aerials slung between each pair of transmitter masts.
The transmission lines were suspended from ceramic insulators on wooden poles. In order to carry the radio frequency power efficiently to the aerials, careful control of the geometry of the transmission lines was necessary. Adjacent to the blast wall entrance to the building was a bay with four glass-insulated feed-throughs for the transmission lines. To minimise danger to the operating staff from the transmission lines, transmitter blocks were built right or left handed depending on the direction of traffic to and from the building.
The building would probably have housed a transmitter type MB3 and ventilation plant. The second transmitter block is identical.
It is not possible to identify the precise location of pieces of equipment because at present no drawings or photographs have been found which are known to show equipment in use in a building of this type.
Each pair of steel transmitter aerial masts could support curtain wire aerials for two alternate frequencies, although it is not clear that all CH stations were equipped for dual frequency operation. A second curtain of reflector rods hung on the landward side of the main curtain. The weight of the aerial curtains was counterbalanced by a massive concrete aerial halyard balance weight and the geometry of the aerial was maintained by a series of aerial curtain balance weights. Each mast was set on a steel ball and was stabilised by steel ropes to eight massive concrete guy points.
The concrete bases of the curtain balance weights have been removed from between the two masts and are parked at the edge of the field.
The second aerial site is better preserved and is still in much the same condition as when the station was decommissioned. The concrete bases of the curtain balance weights are still in place. It may well be the best preserved CH transmitter aerial site in the British Isles.
A three-port concrete and brick electric cable junction box is clearly visible in the gorse hedge. The box now contains brick tiles which would probably have been used originally to mark the route of the cable. They are now scattered along the hedge.
The junction box has three shielded ports, to the north and south along the hedge line and to the east at right angles to the hedge line. The shield for the eastern port is now detached from the box, possibly to make space for the new wire fence.
The cables may have been used to provide power to the aerial site, for example, to control the aerial configuration.
The advanced chain home (ACH) site was probably housed in two wooden huts, one protected by a blast wall. Today there are no physical remains, but the huts are clearly visible in an aerial photograph. The shadows indicate two masts either side of the pair of huts. By comparison with the shadow of the known 325-ft CH aerial mast on the same photograph, the ACH aerial masts are approximately 87-ft high. This is consistent with the report of an inspection party in 1942.
Little information is available on ACH systems, but it is likely that one hut housed the transmitter equipment and the other hut housed the receiver equipment. The ACH transmitter aerial was probably not in the form of a curtain array, but of rigid construction and built into one of the 87-ft masts with the receiver aerial being built into the other mast.
The Mk III IFF Interrogator transmitted a coded radio signal. When this signal was recognised by suitably equipped friendly aircraft, a coded response was automatically transmitted. When the interrogator received the coded response, it caused the echo of the aircraft displayed on the operator’s radar screen to vary in amplitude. This indicated to the operator that it was a friendly aircraft.
The entrance to the cubicle has been blocked by a large piece of concrete. It was, however, just possible to see into the cubicle which appeared to be completely empty.
Three accommodation blocks have been converted into domestic houses named Brambles, Gorsebank and Seafield. These buildings may have been associated with the ACH site.
The stand-by set house is a large brick building with a concrete roof and a concrete blast wall. No public electricity supply was available in this part of the Island when the station was established and therefore electricity was generated on site. Duplicate 135 kVA diesel generator sets were installed in the stand-by set house in order to provide cover for breakdowns and routine servicing. When the Andreas airfield was constructed, an underground electric cable was provided to connect both Andreas airfield and CH Bride to the public electricity supply.
Today an underground electricity cable terminates by the substation and feeds an overhead cable which services present day buildings to the north of the radar station. The Manx Electricity Authority archives contain Air Ministry drawings of the electricity supply to Andreas airfield, but nothing relating to Bride. This might be a consequence of the security classification of chain home stations remaining in force until a later date than the airfield. There is, therefore, at present no evidence that the present cable was originally laid for Bride. The building is now covered by dense gorse, making surveying and photography difficult. Sufficient gorse was removed to gain access and to confirm identification of the building.
The substation has three chambers. It probably allowed either of the two generator sets or the public electricity supply to feed the 3.3 kV ring mains supply for the station.
Three accommodation blocks have been demolished although their bases remain as does an underground air raid shelter. The guard hut is substantially intact. It probably controlled access to the radar station, which would have been surrounded by a barbed wire fence. Two accommodation block buildings at Kerrowdhoo Beg (NX 462026) have been converted into domestic accommodation. The original purpose is unknown. The domestic site for the operational and technical staff was south of Ballacallow (NX 466023). Most of the buildings have now been destroyed.
Although Bride has lost one set of receiving aerial remains and the associated receiver block has been buried by landfill, the remaining receiver block and aerial stubs are in good condition. Similarly, although the curtain balance weights have been removed from one transmitting aerial, the remains of the second transmitting aerial appear to be intact.
Bride has a more comprehensive range of remains in good condition than are to be found at either Dalby or Scarlett. At Dalby the technical buildings are in good condition, but most of the transmitting and receiving aerial remains have been removed. At Scarlett only one receiving aerial stub survives from the two sets of four, all transmitting aerial remains have been removed and explosives have been used on many of the technical buildings to create animal shelters.
From what is known of CH stations elsewhere in the British Isles, Bride is a remarkably well-preserved site. Although elements of the remains at Bride are to be found elsewhere, Bride is now thought to be the only chain home station in the British Isles with a comprehensive set of remains on a single site. CH Bride is now of considerable national and international importance, because it preserves the inter-relationships of the various elements of a working chain home station.
If the proposed extension of sand and gravel extraction takes place further to the south, it presents a serious threat to the integrity of this unique site. Ideally the site should remain as low intensity agriculture, but if sand and gravel extraction is extended to the south, the buildings, aerials, cable routes and access roads should be preserved.
