The Radar Collection: The First Chain Home (CH) Stations

I am one of six volunteers working on different tasks within the Archive and Library team, (Department of Research and Information Services) DORIS, of the RAF Museum. Currently I am working on the Museums Radar Collection, the documents of which are contained in a number of file boxes in the Archives.  My responsibilities are to record details of each document, the subject of the document, its type, date and Radar Station to which it refers. The document can be in the form of operational instructions, drawings, graphs, and tabulated results.  This information is recorded on a spread sheet and will be linked to the Museum’s database. – VERNON

Each Radar Station has its own document file and the stations are listed in alphabetical order from Alnwick –Wood Vale. Each station file usually contains a geographical map of the area, and the station position, a plan of the layout of the site, details of the buildings, and various calibration reports, graphs, and Permanent Echo Diagrams (P.E.D’s), many of which are dated around 1956. Some of the files are more comprehensive than others, and contain many more documents, and some of these station files have documents and drawings dated from 1936 which was when the decision to build the ground radar chain was first decided.

Radar was discovered as a consequence of the need to defend the UK from Air attack. The Air Defence of Great Britain (ADGB) was the subject of a committee, which included Hugh Dowding, set-up in the 1920’s. One of its major considerations was to find a method of early detection of incoming Aircraft, so that standing air patrols would be unnecessary. After various suggestions and trials of different methods, the discovery of radar in 1935 solved the problem.  It was therefore incorporated, as a vital cog, in the overall Air Defence System that was set up prior to the outbreak of the War.

The story of the development of Radar is fascinating but what is often overlooked is the fact that from its development and acceptance in 1936, by 1939 – 1940 there were 20 or more Chain Home (CH) radar stations constructed, along the coast of the British Isles, this as part of the re-armament programme was a tremendous achievement.

The Directorate of Works was given the responsibility of constructing the 20, or so, R.D.F. (Radio Direction Finding) station sites as they were called at the time to be situated on the South and East coast of the British Isles at intervals from Forfarshire, in Scotland to the Isle of Wight. Many of the sites were close to the coast, and at high level and a few miles away from local communities. The sites were all selected by A.F.Wilkins, a member of the RDF development team at Bawdsey Manor. They had to be surveyed for suitability, the land purchased, site drawings prepared, and the construction of the site organised. Each site required the construction of road access, building, and structural services, also a mains electrical supply, a General Post Office (G.P.O). Telephone connection, also water, and, sanitation, services, all of these in remote areas. The site construction was sub-contracted to local building contractors. In addition to the site construction the radar transmitters and receivers, the towers etc all had to be ordered and manufactured. The transmitting towers were made from steel and were 358ft high. The receiving towers were made from wood to ensure that the signal received was not dissipated. The Wooden towers were 240ft high.

The towers were designed and erected by three firms, designed as pre-fabrications and capable of withstanding a wind of 100 M.P.H velocity. The Steel Towers weighed between 90 and 120 Tons, depending upon the actual design.   The transmitters, and, receivers were to be manufactured by commercial companies; Metropolitan Vickers were responsible for the transmitters, A.C. Cossor for the receivers, and Marconi. For the aerial array, most of the technology to be adopted was at this time “State of the Art”, and almost certainly required a learning curve. This learning curve was also experienced by the RAF personnel who were to operate and maintain the equipment. They all had to be recruited, and trained. Most of the training was done at Bawdsey Manor in Suffolk.

Typical East Coast CH Station showing Transmitting towers in foreground and wooden receiving towers in the background

In contrast to the new technology the site construction was reminiscent of 19th century navvies. The sites were in isolated places, and all of the necessary materials had to be transported to site. They would have the use of petrol driven cement mixers, and portable stand-by electrical generator sets, but the ground work would all be by hand. The sites were all of a similar type, but depending on ground conditions the actual layout of the sites differed, apart from the four 358ft transmitting towers always being erected in a straight line, with the transmitting station in the middle. It is worth noting that the tallest National Grid Electricity transmission tower is only 180ft. The four 240ft Timber receiving towers were located in the corners of a trapezium with a centrally placed receiving station. In addition, a standby generating plant with a capacity of 75 kilowatts was provided in a separate building, and accommodation built for a crew of 30 men. At a later date accommodation was added for Women. The transmitting and receiving blocks and the standby set house had brick walls and a 12ins concrete roof. Each building was surrounded by a brick or reinforced concrete traverse wall carried up to the height of the main roof slab. Within the station boundary the services, electricity, G.P.O. etc were all laid in concrete ducts. The G.P.O. connection was essential because it was a secure, and quick, method of transmitting information to the filter stations.

Great Bromley RDF Station plan. Dated 7 July 1938 it shows a typical layout with underground concrete encased cable routes

When, the site construction was completed, and the towers were assembled, and erected, the towers were rigged, the G.P.O lines, the mains electricity, and sanitation services were connected., and the transmitting, and receiving equipment installed. The site was then handed over to the RAF personnel for testing, and calibrating, the equipment.  The stations commenced to operate on a 24-hour watch on Good Friday 1939, when the Germans occupied Czecho-Slovakia.

The air defence of Great Britain was now in place, but it required fine-tuning, the concept and technology was new, and untested in hostile, stressful, conditions, and it would be under constant development, and improvement, throughout the War, and after. There were many early problems to be solved but as Hugh Dowding wrote in 1940 “R.D.F. is very capricious and unreliable but it is better than nothing, as being the best evidence, we have of what is going on over the Sea”

CH Receiver Room showing RAF and WAAF personnel with Console and Receiver equipment

Barry Golding, London Archive Volunteer