01 sept. 2017






Sir Robert Alexander Watson-Watt (April 13, 1892–December 5, 1973), is considered by many to be the „inventor of radar”. Radar development was first started elsewhere (see History of radar), but Watson-Watt worked on some of the first workable radar systems, turning the theory into one of the most important war-winning weapons.

Early years

Born in Brechin in Angus, Scotland, he was a descendant of James Watt, the famous engineer and inventor of the practical steam engine.

After attending Brechin High School , he was accepted to University College, Dundee (which was then part of the University of St Andrews but became the University of Dundee in 1967). He graduated with a BSc in engineering in 1912, and was offered an assistantship by Professor William Peddie. It was Peddie who encouraged him to study radio, or „wireless telegraphy” as it was then known.

Middle years

In 1915 Watson-Watt wanted a job with the War Office, but nothing obvious was available in communications. Instead he joined the Meteorological Office, who were interested in his ideas on the use of radio for the detection of thunderstorms. Lightning gives off a radio signal as it ionizes the air, and he planned on detecting this signal in order to warn pilots of approaching thunderstorms.

Early experiments

His early experiments were successful in detecting the signal, and he quickly proved to be able to do so at long ranges. Two problems remained however. The first was locating the signal, and thus the direction to the storm. This was solved with the use of a directional antenna, which could be manually turned to maximize (or minimize) the signal, thus „pointing” to the storm. Once this was solved the equally difficult problem of actually seeing the fleeting signal became obvious, which he solved with the use of a cathode-ray oscilloscope with a long-lasting phosphor. Such a system represented a significant part of a complete radar system, and was in use as early as 1923. It would, however, need the addition of a pulsed transmitter and a method of measuring the time delay of the received radio echos, and that would in time come from work on ionosondes.

At first he worked at the Wireless Station of Air Ministry Meteorological Office in Aldershot, England. Then in 1924 when the War Department gave notice that they wished to re-occupy their Aldershot site, he moved to Ditton Park near Slough (to the west of London). The National Physical Laboratory (NPL) already had a research station there, and in 1927 they were amalgamated as the Radio Research Station, with Watson-Watt in charge. After a further re-organisation in 1933, Watson-Watt became Superintendent of the Radio Department of NPL in Teddington.

Air defence in the UK

In 1933 the Air Ministry had recently set up a committee to advance the state of the art of air defence in the UK. In World War I the Germans had used Zeppelins as long-range bombers over London and other cities and defences had struggled to counter the threat.

The prospect of aerial bombardment of civilian areas was causing great anxiety with modern heavy bombers able to approach from altitudes that anti-aircraft guns were unable to reach. Worse, with the enemy airfields only 20 minutes away, the bombers would have dropped their bombs and be returning to base before the intercepting fighters could get to altitude. The only solution would be to have standing patrols of fighters in the air at all times, but with the limited cruising time of a fighter this would require a gigantic standing force. Something needed to be done.

Nazi Germany

It was at about this time that Nazi Germany claimed to have a „death-ray” which used radio waves, and claimed it was capable of destroying towns, cities and people. The committee’s chair, H.E. Wimperis, visited Watson-Watt at Teddington in 1934, asking about the possibility of building their own version of such a death-ray, specifically for use against aircraft. Watson-Watt quickly returned a calculation carried out by his assistant, Arnold Wilkins, showing that such a device was basically impossible to construct, and fears of a Nazi version soon vanished. However he also mentioned in the same analysis „Meanwhile attention is being turned to the still difficult, but less unpromising, problem of radio detection and numerical considerations on the method of detection by reflected radio waves will be submitted when required.”

Aircraft detection and location

Wilkin’s sketch of the Daventry Experiment

Memorial at site of first successful RADAR experiments. LAT 52.195982°, LON -1.050121° on 26-2-1935

Closeup of memorial plaque

On February 12, 1935, Watson-Watt sent a memo of the proposed system to the Air Ministry, entitled Detection and location of aircraft by radio methods. Although not as exciting as a death-ray, the concept clearly had amazing potential and Watson-Watt was promptly asked for a demonstration by the committee, chaired by Sir Henry Tizard. This was ready by February 26, and consisted of two receiving antennas located about ten kilometers away from one of the BBC’s shortwave broadcast antennas at Daventry. Signals travelling directly from the station were filtered out, and a Heyford bomber flown around the site (passive radar). Such was the secrecy that only three people witnessed the test, Watson-Watt, his assistant Arnold Wilkins, and a single member of the committee, A.P. Rowe. The demonstration was a success: on several occasions a clear signal was seen from the bomber. Most importantly, the prime minister, Stanley Baldwin, was kept quietly informed of radar’s progress.

Only two weeks later Wilkins left the Radio Research Station with a small party, including Edward George Bowen, to start further research at Orford Ness. On April 2, 1935, Watson-Watt was granted a patent for radar. By June they were detecting aircraft at 27 kilometres, which was enough to stop all work on competing sound-based detection systems. By the end of the year the range was up to 100 kilometres, at which point plans were made in December to set up five stations covering the approaches to London.

One of these stations was to be located on the coast near Orford Ness, and Bawdsey Research Station was set up there to become the main centre for all radar research. They soon conducted „full scale” tests of a system that would soon be known as Chain Home, attempting to intercept a bomber by radar direction. The tests were a massive failure, with the fighter only seeing the bomber after it had passed its target. The problem was not the radar, but the flow of information from the trackers to the fighters, which took many steps and was very slow. Watson-Watt immediately attacked this problem, and set up the system with several layers of reporting that were eventually sent to a single large room for mapping. Observers watching the maps would then tell the fighter groups what to do via direct communications.

By 1937 the first three stations were ready, and his new reporting system put to the test. The results were clearly successful and an immediate order for an additional 20 stations was sent out. By the start of World War II 19 were ready to play a key part in the Battle of Britain, and by the end of the war over 50 had been built. The Germans were aware of the construction of Chain Home but were not sure of their purpose. They tested their theories with a flight of LZ 130, the GRAF Zeppelin II, but concluded the stations were a new long-range naval communications system.

Even as early as 1936 it was realized that the Luftwaffe would turn to night bombing if the day campaign did not go well, and Watson-Watt had put another of the staff from the Radio Research Station, Edward Bowen, in charge of developing a radar that could be carried by a fighter. Night time visual detection of a bomber was good to about 300 metres, and the existing CH systems simply didn’t have the accuracy needed to get the fighters that close. Bowen decided that an airborne radar should not exceed 200 pounds (90 kg) in weight, 8 ft³ (230 L) in volume, and require no more than 500 watts of power. To reduce the drag of the antennas the operating wavelength could not be much greater than one metre, difficult for the day’s electronics. Nevertheless such a system, known as „AI” – Airborne Interception, was perfected by 1940, and were instrumental in eventually ending „The Blitz” of 1941. Bowen also fitted airborne radar to maritime patrol aircraft (known in this application as „ASV” – Air to Surface Vessel) and this eventually reduced the threat from submarines.

Contribution to World war II

In his English History 1914-1945, eminent English Historian A.J.P. Taylor paid the highest of praise to Watson Watt, Sir Henry Tizard and their associates who developed and put in place radar, crediting them with being fundamental to victory in World war II. There would have been no success in the Battle of Britain without radar and consequently Britain would not have survived.

Later years

In July 1938 Watson-Watt left Bawdsey Manor and took up the post of Director of Communications Development (DCD-RAE). In 1939 Sir George Lee took over the job of DCD, and Watson-Watt became Scientific Advisor on Telecommunications (SAT) to the Air Ministry, travelling to the USA in 1941 in order to advise them on the severe inadequacies of their air defense efforts illustrated by the Pearl Harbor attack.

His contributions to the war effort were so overwhelming that he was knighted in 1942. In 1952 he was awarded £50,000 by the British government for his contributions in the development of radar. He spent much of the post-war era in Canada, and later the USA, where he published Three Steps to Victory in 1958.

On one occasion, late in his life, Sir Watson-Watt reportedly was pulled over in America for speeding by a radar-gun toting policeman. His remark was, „Had I known what you were going to do with it I would never have invented it!”

Death and afterwards

After the war Watson-Watt was reportedly disappointed that he did not gain more recognition for his contribution to the allies’ victory. He established a practice as a consulting engineer, but in the 1950s moved to Canada, and later to the USA. He returned to Scotland in the 1960s.

In 1966, at the age of 72, he proposed to Kathryn Jane Trefusis Forbes. Trefusis-Forbes, who at that time was 67, had also played a significant role in the Battle of Britain as the founding Air Commander of the Women’s’ Auxiliary Air Force, which supplied the radar-room operatives.

From that time, they lived together in London in the winter, and at The Observatory – Trefusis-Forbes summer home, in Pitlochry, Perthshire, during the warmer months. The marriage was not considered a universal success – certainly by members of Kathryn Jane’s family. Nevertheless, the couple stayed together until they died – Dame Kathryn in 1971, Watson-Watt in 1973. Both are buried in the church yard at Pitlochry.

He died in Inverness.

External links

* Davis, Chris, „Sir Robert Alexander Watson-Watt, FRS (1892-1973)”
* Hollmann, Martin, „Radar Development In England”. Radar World.
* Lem, Elizabeth, „The Ditton Park Archive”. Ditton Park Archive, rl.ac.uk. January 2004.
* „Radar Personalities : Sir Robert Watson-Watt”. RadarPages.
* „The Royal Air Force Air Defence Radar Museum” at RRH Neatishead, Norfolk.
* „The Watson-Watt Society of Brechin”. aims to encourage the public to have a better understanding of the pioneering work of Sir Robert Watson-Watt. The Society intends to create a permanent memorial in Brechin- artists and craftsmen will be invited to submit designs and tender for the work. It is hoped that science and aviation enthusiasts will visit this ancient and interesting city to view the memorial, which will be raised by public subscription and is planned to be unveiled in 2009. It is also intended to produce an interactive digital exhibit for use in the Town House Museum, and to provided an annual science prize for Brechin High School senior pupils.

Notes and references

1. ^ Sir Robert Watson-Watt. Dick Barrett. Retrieved on 2008-02-26.
2. ^ Robert Watson-Watt. The Radar Pages. Retrieved on 2007-12-14