Purbeck Radar ~ Story of early radar

Story of Early=20 Radar

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In 1934 a large-scale Air Defence exercise was held = to test=20 the defences of Great Britain and mock raids were = carried out=20 on London. Even though the routes and targets were = known in=20 advance, well over half the bombers reached their = targets=20 without opposition. Prime Minister Baldwin's statement = "The=20 bomber will always get through" seemed true. To = give=20 time for their guns to engage enemy aircraft as they = came=20 over, the Army was experimenting with the sound = detection of=20 aircraft by using massive concrete acoustic mirrors = with=20 microphones at their focal points.=20

Dr H.E. Wimperis, the first Director of Scientific = Research=20 for the Air Ministry, and his assistant Mr A.P. Rowe = arranged=20 for Air Marshall Dowding to visit the Army site on the = Romney=20 Marshes to see a demonstration. On the morning of the = test the=20 experiment was completely wrecked by a milk cart = rattling by.=20 Rowe was so concerned by this failure that he gathered = up all=20 the Air Ministry files on the subject of Air Defence. = He was=20 so appalled that he wrote formally to Wimperis to say = that if=20 we were involved in a major war we would loose it = unless=20 something new could be discovered to change the = situation. He=20 suggested that the best advisors obtainable should = review the=20 whole situation to see whether any new initiatives = could be=20 found. On 12th November Wimperis put this proposal to = the=20 Secretary of State and a Committee was set up under = Henry=20 Tizard.=20

The idea of using rays to kill or disable people or = machines was very popular, so to start things off = Wimperis got=20 Professor Hill to estimate the radio energy needed to = cause=20 damage to humans. He sent this to Mr Watson-Watt,=20 Superintendent of the Radio Research Station at Slough = for his=20 views on the possibility of developing a radio "Death = Ray" to=20 melt metal or incapacitate an aircraft pilot. = Watson-Watt=20 passed the letter to A.F. Wilkins who reported that = there was=20 no possibility of achieving these destructive effects = at a=20 distance but that energy reflected from aircraft = should be=20 detectable at useful ranges. This was reported to the = first=20 meeting of the Tizard Committee on 28th January and = Rowe was=20 instructed to get quantitative estimates for = detection.=20

Wilkins made further calculations from which = Watson-Watt=20 wrote a memorandum proposing a system of = radio-location using=20 a pulse/echo technique. The Committee gave this a very = favourable reception and Wimperis asked Dowding for = =A310,000 to=20 investigate this new method of detection. Dowding, = though very=20 interested, said he must have a simple practical = demonstration=20 to show feasibility before committing scarce funds to = the=20 project.=20

For this demonstration Watson-Watt and Wilkins = decided to=20 make use of transmissions from the powerful BBC = short-wave=20 station at Daventry and measure the power reflected = from a=20 Heyford bomber flying up and down at various ranges. = Detection=20 was achieved at up to 8 miles and the =A310,000 was = granted.=20

A site at Orfordness was chosen to do the detection = experiments over the sea. Aerials mounted on three = pairs of=20 75ft wooden lattice masts were installed and detection = ranges=20 of 17 miles were obtained. These were rapidly = increased to 40=20 miles by July. Work was done to show how map position = and=20 height might be determined and Watson-Watt submitted = proposals=20 for a chain of stations to be erected round the coast = to=20 provide warning of attack and to tell fighters where = to engage=20 the attackers. He suggested that a full-scale station = should=20 be built at once, to be followed, if successful, by a = group of=20 stations to cover the Thames Estuary and then by a = final chain=20 covering the South and East coasts. Construction of 5 = stations=20 was authorised and the one at Bawdsey was in operation = by=20 August 1936. The others followed shortly after. Plots = were to=20 be telephoned to a central operations room and = combined with=20 data from the Royal Observer Corps and the radio=20 direction-finding system.=20

In February 1936 Bawdsey Manor became the centre = for the=20 expanding research team and Tizard inspired the RAF at = Biggin=20 Hill to investigate fighter control and interception=20 techniques. Their results convinced him that effective = interceptions could be obtained against mass raids by = day, but=20 not against dispersed attackers at night. He therefore = pressed=20 for equipment to go into fighters for them to find and = engage=20 targets when positioned within a few miles. Initial = tests=20 using a large television transmitter on the ground = operating=20 on a wavelength of 6 metres and a receiver in a = Heyford Bomber=20 with an aerial between its wheels gave detection = ranges of=20 over 10 miles. To get a transmitter into an aircraft = and=20 reduce the size of the aerial a much lower wavelength = was=20 required. Bowen installed a crude equipment operating = at 1=20 metre in an Anson and in the autumn of 1937 aircraft = were=20 detected and also Naval ships several miles away in = appalling=20 weather.=20

From then on Air Interception (AI) and Air to = Surface=20 Vessel (ASV) equipments were developed. Further Air = Defence=20 Trials showed that better detection of low flying = aircraft was=20 needed and Chain Low (CHL) stations were evolved from = Coastal=20 Defence (CD) equipments which had been developed for = the Army.=20 Gun laying equipments (GL) were developed and also = equipments=20 to improve navigation (GEE) and bombing (OBOE) and = (H2S).=20

This story is continued in "The Early = Days of=20 Radar" by Dr Bill Penley - one of the early radar=20 researchers.

The Early Days of Radar in the UK = by Dr=20 Bill Penley