In the February edition of The Marshwood in A History of Science in 20 Objects I mentioned that I would have included Radar. Radar was included in the Brooke Bond Picture Cards of 1975 which I also referred to, but how many now can recall the person called the Father of Radar?
Sir Robert Alexander Watson-Watt has been described as the Father of Radar by Professor Hanbury Brown. Hanbury Brown had worked under Watson-Watt in the early days of the development of radar and said that he had the ability to inspire followers with devotion and enthusiasm. The fact that ground and airborne radar were developed in time for World War II and the Battle of Britain was largely due to Watson-Watt.
Watson-Watt was born in 1892 in Brechin, Aberdeenshire, the son of a carpenter and studied Electrical Engineering at University College in Dundee. He was appointed assistant to the Professor of Physics who encouraged him to study wireless telegraphy. After the outbreak of the First World War he joined the Meteorological Office at Ditton Park (Slough) to work on radio methods of locating thunderstorms, if possible to warn aircraft. This led to the use of rotating frame aerials and later the cathode-ray direction finder. In 1927 Watson-Watt was appointed Superintendent of the Radio Research Station which also included measuring the height of the reflecting layers of the ionosphere by pulsed radio. The word “ionosphere” was coined by Watson-Watt.
In 1935 H E Wimperis, Air Ministry Director of Research, set up a Committee for the Scientific Study of Air Defence under H T Tizard to consider if recent advances in scientific knowledge could improve our defences against hostile aircraft. During the 1914-18 war we were not very successful in finding enemy zeppelins at night and by 1930 it was decided to use sensitive microphones and sound reflectors around the southeastern approaches to London. Large reflectors could detect an aircraft at between 30 and 40 km, so would give about 4 minutes warning of an approaching aircraft. We also had the Royal Observer Corps with binoculars and manual height detectors who could identify and count enemy aircraft in daylight. Wimperis asked Watson-Watt if a hostile aircraft could be damaged by radiation—could we make a “death-ray”. He replied that it would require some 30 MW at least, far more than could be produced then and if the aircraft were metal clad the crew and engine would be shielded from radiation. He said that a less unpromising problem of radio detection could be submitted when required.
Professor Hanbury Brown knew Watson-Watt well and commented that “less unpromising” was a typical remark of Watson-Watt who by using double negatives and convoluted syntax, etc., could make the simplest subject difficult.
Watson-Watt sent a memorandum to Tizard’s committee entitled “Detection of aircraft by radio methods” in February 1935. He estimated the radio signal strength reflected from an aircraft and the optimum wavelength, together with how the distance of the target could be measured and that a cathode-ray direction-finder might be developed to measure its elevation and bearing. The Committee requested a trial. A Heyford bomber flew at 2000 m height to and from a beam from the BBC transmitter in a demonstration in February 1935. They saw signals from the aircraft for about 4 minutes as it passed overhead.
The report was favourable and two weeks later a small group left the Slough Research Station for Orfordness to commence development of radar, then called Radio Direction Finding. They included A E Wilkins, E G Bowen and L H Bainbridge-Bell and they soon had a working radar. After only five weeks they saw an echo from a Scapa flying boat at a range of 27 km. By the end of the year, they could detect aircraft at ranges of 100km well beyond the range of sound locators and also its position in three dimensions. Watson-Watt visited Orford from Slough almost every weekend. By December 1935 it was agreed to build five radar stations covering the approaches to London, between Bawdsey and South Foreland. The Air Ministry bought Bawdsey Manor on the coast near Orford early in 1936 and Watson-Watt was appointed its Superintendent.
Watson-Watt proposed a new system of air defence and this began in 1937. A “filter room “ was to correlate raw data from several radar stations before it was passed on to those controlling the fighter aircraft. This was arranged with RAF Fighter Command and was ready in time for the Battle of Britain. Watson-Watt claimed to have “invented” the use of WAAFs (Women’s Auxiliary Air Force) as radar operators. A second trial in 1937 using three of the five original stations was successful and a coastal chain of stations named Home Chain of 20 more stations was agreed.
By the outbreak of war, there were 19 stations on the east coast and six on the south, giving coverage from Scotland to Portsmouth. The Home Chain stations on the east coast each used four steel towers of 110 m height supporting eight dipole aerials for transmission and the receiver used three or four wooden towers of 73 m height. The transmitter valves were water-cooled and the receiver display was on a cathode-ray tube (like a modern television display) calibrated with the distance of the incoming aircraft.
Watson-Watt realised that the German Air Force were likely to commence bombing by night, especially if our radar succeeded in stopping them by day. Our aircraft would then need to carry radar to find and identify an enemy aircraft in the dark. In early 1936 Watson-Watt asked Dr E G Bowen to develop airborne radar. It was a very difficult problem as the ground radar weighed several tons and consumed many kilowatts of power. The first radar for night flying, called AI (Air Interception) was delivered to Fighter Command in a Blenheim aircraft in August 1939 and later was used successfully against night raids in early 1941. Radar for detecting ships, called ASV (Air to Surface Vessels) was delivered to the RAF in a Hudson aircraft in January 1940.
In 1940 H A Boot and J T Randall at Birmingham University developed the cavity magnetron which could generate high transmitter power at microwaves and so use smaller antennas, more suited to aircraft. The first operational use of centimetre-wave radar for AI was made in December 1941 and for ASV in March 1943.
In 1940/41 an experimental station was set up at Worth Matravers in Dorset on a large high flat area further from possible German invasion. It eventually employed 200 who developed the rotating aerial and map displays for tracking targets. Other radar stations were set up on Purbeck. Later a station was built near Stonebarrow Hill and Golden Cap at the time of the Cold War. It is now a National Trust property.
Watson-Watt left Bawdsey Manor in July 1938 to become Director of Communications Development in the Air Ministry in London, but he kept a close watch on radar development and its use by the RAF. His replacement as Superintendent of Bawdsey was A P Rowe. In 1939 Watson-Watt was appointed Scientific Advisor on Telecommunications to the Air Ministry and later to the Ministry of Aircraft Production.
In 1942 Watson-Watt was knighted. After the war, he was Scientific Adviser to various Ministries and led delegations to international meetings. In 1947 he set up a private firm of consultants, later moving to Canada and the USA. He returned to die in Scotland in 1973.
Three UK patents were granted in his name between 1924 and 1936 all of them having a bearing on the development of radar.
Watson-Watt wrote his own book of the development of radar, Tree Steps to Victory which I remember reading years ago and found it heavy going, with many references to official reports.
However, we should certainly remember “The Father of Radar” when we hear expressions like “under the radar”. Radar is now indispensable in our time of heavy air traffic and without its development, we might not have modern TV and microwave ovens.
I have based this article on one by Hanbury Brown in the Institution of Electrical Engineers journal of February 1994 but have tried to omit as much technical jargon as possible.
Cecil Amor, Hon President of Bridport History Society.