Editing Robert Watson-Watt (section)

==RADAR==

===The air defence problem===
During the [[First World War]], the Germans had used [[Zeppelin]]s as long-range bombers over Britain and defences had struggled to counter the threat. Since that time, aircraft capabilities had improved considerably and the prospect of widespread aerial bombardment of civilian areas was causing the government anxiety. Heavy bombers were now able to approach at altitudes that anti-aircraft guns of the day were unable to reach.<ref>{{cite web|last=Evans|first=R.J.|title=Hitler and the origins of the war, 1919–1939|url=http://www.gresham.ac.uk/event.asp?PageId=108&EventId=775|date=18 September 2008|work=Lecture transcript|publisher=Gresham College|access-date=16 August 2009|url-status=dead|archive-url=https://web.archive.org/web/20101117194902/http://gresham.ac.uk/event.asp?PageId=108&EventId=775|archive-date=17 November 2010}}</ref> With enemy airfields across the English Channel potentially only 20 minutes' flying-time away, bombers would have dropped their bombs and be returning to base before any intercepting fighters could get to altitude. The only answer seemed to be to have standing patrols of fighters in the air, but with the limited cruising time of a fighter, this would require a huge air force. An alternative solution was urgently needed and, in 1934, the Air Ministry set up a committee, the CSSAD ([[Committee for the Scientific Survey of Air Defence]]), chaired by Sir [[Henry Tizard]] to find ways to improve air defence in the UK.{{citation needed|date=February 2021}}

Rumours that [[Nazi Germany]] had developed a "[[death ray]]" that was capable of destroying towns, cities and people using radio waves, were given attention in January 1935 by [[Harry Wimperis]], Director of Scientific Research at the Air Ministry. He asked Watson-Watt about the possibility of building their version of a death-ray, specifically to be used against aircraft.<ref name="Patent"/> Watson-Watt quickly returned a calculation carried out by his young colleague, [[Arnold Frederic Wilkins|Arnold Wilkins]], showing that such a device was impossible to construct, and fears of a Nazi version soon vanished. He also mentioned in the same report a suggestion that was originally made to him by Wilkins, who had recently heard of aircraft disturbing [[Communications receiver|shortwave communications]], that radio waves might be capable of detecting aircraft, "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". Wilkins's idea, checked by Watt, was promptly presented by Tizard to the CSSAD on 28 January 1935.<ref>{{cite book|last1=Buderi|first1=Robert|title=The Invention That Changed the World: How a Small Group of Radar Pioneers Won the Second World War and Launched a Technical Revolution|date=1996|publisher=Simon & Schuster|isbn=978-0-684-83529-7|page=[https://archive.org/details/isbn_9780684835297/page/55 55]|edition=1998|url=https://archive.org/details/isbn_9780684835297/page/55}}</ref>

===Aircraft detection and location===
[[File:Watson watt 01 fr.jpg|thumb|Memorial at the [[Daventry]] site of the first successful RADAR experiments. {{Coord|52.195982|N|1.050121|W|}}]]
[[File:Watson watt 02 fr.jpg|thumb|Closeup of memorial plaque]]
[[File:Watson Radar.jpg|thumb|The first workable radar unit constructed by Robert Watson Watt and his team]]
On 12 February 1935, Watson-Watt sent the secret memo of the proposed system to the [[Air Ministry]], ''Detection and location of aircraft by radio methods''. Although not as exciting as a death-ray, the concept clearly had potential, but the Air Ministry, before giving funding, asked for a demonstration proving that radio waves could be reflected by an aircraft.<ref>{{cite web|publisher=The Radar Pages|url=http://www.radarpages.co.uk/people/watson-watt/watson-watt.htm|title=Robert Watson-Watt|access-date=14 December 2007|url-status=live|archive-url=https://web.archive.org/web/20071217032228/http://www.radarpages.co.uk/people/watson-watt/watson-watt.htm|archive-date=17 December 2007}}</ref> This was ready by 26 February and consisted of two receiving antennae located about {{convert|6|mile|km|0}} away from one of the [[BBC]]'s shortwave broadcast stations at [[Daventry transmitting station|Daventry]]. The two antennae were phased such that signals travelling directly from the station cancelled themselves out, but signals arriving from other angles were admitted, thereby deflecting the trace on a [[Cathode-ray tube|CRT]] indicator ([[passive radar]]).<ref>{{cite web|publisher=IET|url=http://tv.theiet.org/technology/communications/219.cfm|title=Passive Covert Radar – Watson-Watt's Daventry Experiment Revisited|access-date=13 December 2008|url-status=live|archive-url=https://web.archive.org/web/20110513210855/http://tv.theiet.org/technology/communications/219.cfm|archive-date=13 May 2011}}</ref> Such was the secrecy of this test that only three people witnessed it: Watson-Watt, his colleague Arnold Wilkins, and a single member of the committee, [[A. P. Rowe]]. The demonstration was a success: on several occasions, the receiver showed a clear return signal from a [[Handley Page Heyford]] bomber flown around the site. Prime Minister [[Stanley Baldwin]] was kept quietly informed of radar progress. On 2 April 1935, Watson-Watt received a patent on a radio device for detecting and locating an aircraft.<ref name="Patent"/>

In mid-May 1935, Wilkins left the Radio Research Station with a small party, including [[Edward George Bowen]], to start further research at [[Orford Ness]], an isolated peninsula on the Suffolk coast of the North Sea. By June, they were detecting aircraft at a distance of {{cvt|16|mi|km}}, which was enough for scientists and engineers to stop all work on competing [[Acoustic location|sound-based detection systems]]. By the end of the year, the range was up to {{cvt|60|mi|km}}, at which point, plans were made in December to set up five stations covering the approaches to London.{{citation needed|date=February 2021}}

One of these stations was to be located on the coast near [[Orford Ness]], and [[Bawdsey Manor]] was selected to become the main centre for all radar research. To put a radar defence in place as quickly as possible, Watson-Watt and his team created devices using existing components, rather than creating new components for the project, and the team did not take additional time to refine and improve the devices. So long as the prototype radars were in workable condition, they were put into production.<ref name="minefield">{{cite web |last1=Corrigan |first1=R. |title=Airborne minefields and Fighter Command's information system |url=http://www.law.ed.ac.uk/ahrc/gikii/docs3/corrigan.pdf |website=The University of Edinburgh, School of Law |access-date=16 August 2009 |archive-url=https://web.archive.org/web/20110903051653/http://www.law.ed.ac.uk/ahrc/gikii/docs3/corrigan.pdf |archive-date=3 September 2011 |date=25 September 2008 |url-status=dead}}</ref> They conducted "full scale" tests of a fixed radar [[radio masts and towers|radio tower]] system, attempting to detect an incoming bomber by radio signals for interception by a fighter.<ref name=minefield /><ref name=statue>{{cite web|title=Tribute plan for radar inventor|url=http://news.bbc.co.uk/2/hi/uk_news/scotland/tayside_and_central/6104186.stm|date=1 November 2006|publisher=BBC|access-date=16 August 2009|url-status=live|archive-url=https://web.archive.org/web/20080408141350/http://news.bbc.co.uk/2/hi/uk_news/scotland/tayside_and_central/6104186.stm|archive-date=8 April 2008}}</ref> The tests were a complete 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 trackers from the [[Observer Corps]] to the fighters, which took many steps and was very slow. [[Henry Tizard]], [[Patrick Blackett]], and [[Hugh Dowding]] immediately set to work on this problem, designing a 'command and control air defence reporting 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 fighters what to do via direct communications.<ref name=minefield />

[[File:Chain home coverage.jpg|thumb|left|Radar coverage along the UK coast, 1939–1940]]
By 1937, the first three stations were ready, and the associated system was put to the test. The results were encouraging, and the government immediately commissioned construction of 17 additional stations. This became [[Chain Home]], the array of fixed radar towers on the east and south coasts of England.<ref name=minefield /><ref name=statue /> By the start of World War II, 19 were ready for 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 its purpose. They tested their theories with a flight of the Zeppelin [[LZ 130 Graf Zeppelin|LZ 130]] but concluded the stations were a new long-range naval communications system.{{citation needed|date=February 2021}}

As early as 1936, it was realized that the ''[[Luftwaffe]]'' would turn to night bombing if the day campaign did not go well. 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&nbsp;m and the existing Chain Home systems simply did not have the accuracy needed to get the fighters that close. Bowen decided that an airborne radar should not exceed 90 [[kilogram|kg]] (200 [[pound (mass)|lb]]) in weight or 8&nbsp;ft³ (230 [[litre|L]]) in volume and should require no more than 500 watts of power. To reduce the drag of the antennae, the operating wavelength could not be much greater than one metre, difficult for the day's electronics. However, [[aircraft interception radar|aircraft interception (AI) radar]] was perfected by 1940 and was instrumental in eventually ending [[The Blitz]] of 1941. Watson-Watt justified his choice of a non-optimal frequency for his radar, with his oft-quoted [[Perfect is the enemy of good|"cult of the imperfect"]], which he stated as "Give them the third-best to go on with; the second-best comes too late; the best never comes".<ref>{{cite book |last1=Fine |first1=Norman |title=Blind Bombing: How Microwave Radar Brought the Allies to D-Day and Victory in World War II |date=2019 |publisher=Potomac Books |isbn=9781640122208 |page=21}}</ref>{{sfn|Brown|1999|p=63}}