This room would once have housed the main radar equipment. A top secret document (AIR 8/1630) dated 1952 describes some of the equipment installed here. It was a 10cm Chain Home Extra Low (CHEL) installation “designed to provide cover against low flying aircraft and surface vessels”. The main displays specified for similar sites would have been five Plan Position Indicators very similar to those used during the war but it is thought that only one may have been used at Truleigh. These had two cathode ray tubes , one was a range indication only but the other gave a two dimensional representation of the transmitter beam and the target similar to those seen in modern displays. In many cases, and probably here at Truleigh, the delay in producing new PPIs meant that WW2 equipment was refurbished and put back into service. Completion of the Truleigh Hill ROTOR site was expected to be by December 1952 but there were to be delays. Eventually however, in another classified document CRPC/G.391/1831 dated 1/7/53 it was reported that Phase 2 of ROTOR, which included Truleigh Hill, was completed in the last week of June 1953. Hopton was the last station to be handed over to the RAF, delayed as a result of a fire, in January of that year, in the air conditioning plant. This fire was kept secret and no report of it ever reached the public yet the UK’s early warning system was compromised for six months as a result.The Type 14 radar used at Truleigh had no height finding unit but, since it was meant to detect low-flying intruder or surface ships, this was not really necessary. The aerial was a basic parabolic aerial mounted on a cabin. The whole of this was mounted on a base unit, described later, and the combined cabin and aerial rotated. Operators or maintenance engineers could actually work within the cabin while it rotated. There were no radar screens or such inside the cabin, of course.
The Air Ministry estimated that the works programme for the 38 radar stations and 4 Sector Operations Centres (SOC) would require 350,000 tons of cement and 20,000 tons of steel amongst other things. The communications side would require some 1,000 miles of new trunk ducts, 750 teleprinters and 40 new repeater station. The majority of this had to be constructed in remote areas and at a time when everything was in very short supply. as well, the whole project was secret and the public were not even to know of its existence. Even today, everyone interviewed starts their conversation with words such “I don’t know if I’m meant to talk about this but …”.
The layout of this room shows that this was an R2 bunker. R1 and R2’s were both single level with the difference that the R1 bunkers had a 20 foot deep pit in this room where a Kelvin Hughes projector would be sited. This device was a continuous photographic process which filmed the radar screen, processed the film and projected the image onto a glass screen within a very few seconds. Originally there would have been a full height wall where the plant rooms can be seen at the far end and another full height wall some 12 feet further in from that. The room between these two walls was used by the radar service engineers for repairs and testing but there remains no real evidence of either wall. The main operations room is about 90 feet long and all the false floor has been removed and was sold off before the bunker was disposed of by the RAF. At the far end can be seen the three plant rooms with a machine bed in front.
The height of the false floor can be clearly seen in the different floor levels in the corridor and this room. As a standard CHEL station there should have been 5 PPIs installed plus all the associated control and electronics equipment to support it all. Also in this room was a large plotting table reminiscent of the scenes in so many WW2 films. Markers would be placed on the table and moved around as the operators tracked targets both in the air and on the surface above.The RAF recovered all radar equipment and the Ministry auctioned off everything else before offering the site for sale to the public in 1965. Other documentation recently made available contradicts this and different figures of 6 and 8 PPIs have also been found. Memories of those who worked here have faded, of course, so a definitive figure is still sought.
This large room was the scene of the charity balls held in the 1960’s but they were stopped because participants couldn’t be trusted not to smoke. The cladding includes a mixture of cork and pitch and once ignited, would smoulder and burn for weeks. Other sites which have suffered such fires have been rendered completely unusable. Much of the cladding is now detaching itself from the walls and ceilings and the floor is littered with debris in some places.
