Site Records

Site Name: 'RAF Trimmingham' ('QLE') CEW R1 ROTOR Radar Station

Trimmingham Radar Station was established in late 1941 as an army coastal defence radar station for detecting German E-Boats and low flying aircraft; it was equipped with a CD Mk.4 radar. Trimmingham was also chosen as an 'Oboe' station equipped with Type 9000 equipment for navigational purposes to assist bombers to pinpoint European targets. It was operational in this capacity by December 1942. By 1943 the station had passed to the RAF and was now a Chain Home Extra Low (CHEL)/CD with a Type 54 radar on a 200 foot tower. The 'Oboe' equipment had been removed by 1945.

In June 1950 RAF Trimmingham was selected for the ROTOR programme as a Centimetric Early Warning Station (CEW) equipped with the Type 54, two Type 13 Mk. 6 height finding radars, 1 Type 14 Mk.8 and 1 Type 14 Mk. 9 surveillance radars mounted on concrete plinths. The station was completed in November 1952 coming on line early the following year.

Operations were centred in an R1 single level underground bunker accessed from the rear of a standard guardhouse/bungalow, a single storey building with a pitched tile roof and a veranda at the front. At the rear is a square stairwell and goods entrance with a flat roof. Internally there was a guardroom, armoury, stores and rest room.

Trimmingham was later selected as the location for the first production Type 80 Mk1 search radar which was installed in 1954. The Type 80, one of five Mk 1's installed throughout the UK came on line in April 1955. Trimmingham was retained as a CEW station, the installation of the new Type 80 was delayed and an American Type AN-FPS Type 3 long range radar and an AN/TPS10 height finder were installed (the now 'redundent' Type 14's being removed). Trimmingham also continued in it's CHEL role utilising a Type 54 Mk3.

By 1965, air photographs show the station had been largely dismantled and all the radar arrays had been removed apart from the Type 54 behind Beaconhill House; but that was gone by 1972. By 1981 the station was closed and the guardhouse had been sold and converted into a private house.

Trimmingham was reactivated by the RAF in the late 1980's with the installation of a Marconi Type 91 'Martello' radar operated by 432 Signals Unit acting as a Ready Platform (along with RAF Hopton and Weybourne) for the UKADGE Series II (Upgraded Air Defence Ground Environment) Radar System controlled from the R3 underground control centre at RAF Neatishead. The guardhouse was converted into crew accommodation, offices and basic mess facilities. An upper storey was created in the roof space and the external veranda along the front of the building was removed.

Both at Trimmingham and Hopton the mounds were removed and the sites shaved to the concrete roof of the bunker. This was then built up with the ready platform on top of a new grassed mound. Ramps were then made to allow vehicle access to the top surface, on which the remote radars would be sited. In May 1987 the Type 91 there was sold to the Turkish Ministry of Defence and it was replaced by a Type 93 (Plessey type ADGE-305, NATO designation TGRI 50011) that had been moved from Hopton. Following the removal of the Type 93 Hopton closed.

Although originally a mobile installation in December 1997 the Type 93 was given a permanent mounting with a Kevlon dome composed of irregular polygons erected around it. Although the Type 93 is still operational feeding data back to Neatishead it's future is uncertain.

The guardhouse is still in MOD ownership and although the R1 bunker is still accessible visits are not allowed on health and safety grounds. At the end of the sloping entrance tunnel a wall has been built across the passage with a wooden door and combination lock. Through the door is a security post on the left and the cable entry point on the right. The tunnel then does a dog leg left and right into the main east - west spine corridor. Section of wooden flooring along the corridor have been removed making progress difficult and dangerous.

There are now three rooms on the left and five rooms on the right. The second door on the left is the main operations room, and within it, wooden stairs down to a lower area or room (original plans call this an 'udder'). This was designed for the Kelvin Hughes display equipment and you can clearly see the two sets of AC connectors which supplied filtered/cooled air and removed 'dirty' hot air. These two sets of trunking would of serviced the two KH projection units, these would of had a large swivel mirror between them allowing either to be used to project a GSM to the projection table above and allow in-line servicing. This room would of also contained a small darkroom and film store.

Dick Barret describes the KH equipment (at Bawdsey ca 1970):

"This consisted of equipment that could record the radar image on 35 mm film, develop, fix and dry the image and then project it up on to the plotting table in the control room on the floor above. The displayed image was one minute behind real time. The PPI image from a high intensity CRT was projected on to the film through a focusing lens. Each revolution of the radar antenna took 15 seconds, so it took this time to expose the film to a full revolution. At the end of the sweep the frame would be moved on to be developed, whilst the next frame was exposed. When the frame moved on at the end of the next sweep the image was fixed, it then moved on again and it was dried. Finally the frame moved on once more where it was projected, via a mirror, to the floor above. Meanwhile the next frame to be exposed had been following on through the process, so at the end of the next revolution this frame was projected, 15 seconds after its predecessor. As frame after frame was displayed on the map, the plotters in the pit would place markers on the map to indicate friendly or hostile returns. The senior officers could rapidly judge how a threat was building and see the big picture by watching the display on the map. The centre of the display usually consisted of permanent echoes, 'clutter', would be 'blanked off' here"

The operations room has been completely stripped apart from the brick supports for the now removed wooden floor and ventilation trunking on both levels and part of the air handling system. The third entrance on the left is the AC plant room which has been stripped of most of its plant, only part of the part of the air handling system and a bank of filters remain in place.

On the right the rooms have also been stripped. The original functions allocated to rooms in an R1 were: Plant, GPO Apparatus, Track Telling Room, Workshop, Radar Office, Cloak & Rest Room, Technical Officers Room and a spare room.

Beyond the plant room the corridors dog legs right and left, the emergency exit has been filled with rubble and soil.

Trimmingham is located on Beacon Hill on the North Norfolk Coast between Cromer and Mundesley. The site originally consisted of 10 acres on both sides of Mundesley Road but now only the southern part of the site is occupied by the RAF. One radar plinth survives at TG28913837. There is also a single storey brick building a little to the south of the plinth. The AMES Type 80 Mk1 modulator building still stands at TG28903835.

Sources:

• RCHME Survey report on RAF Trimmingham (1998) by Wayne Cocroft
• PRO Files AIR 29/167 & 168
• PRO Files AIR 2/10984 August 1952 listing equipment changes when Type 80 installed
• PRO Files AIR 8/2032 1 January 1954
• Bob Jenner
• Ray Watson
• Dr. James Fox

Home Page

© 1998-2002 Subterranea Britannica