Editing Radar (section)

===Before World War II===
[[File:Early radar antenna - US Naval Research Laboratory Anacostia.jpg|thumb|upright=0.8|Experimental radar antenna, US [[Naval Research Laboratory]], Anacostia, D. C., from the late 1930s (photo taken in 1945)]]
Before the [[Second World War]], researchers in the United Kingdom, [[French Third Republic|France]], [[Nazi Germany|Germany]], [[Kingdom of Italy|Italy]], [[Japanese Empire|Japan]], the [[Netherlands]],<ref>{{cite web|url=https://www.museumwaalsdorp.nl/en/museum-waalsdorp-2/airacous/air-acoustics-electric-listening-device/ |title=The "Electric listening device" (1936 – 1941) |website=museumwaalsdorp.nl |access-date=2024-11-10}}</ref> the [[Soviet Union]], and the United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, [[Regency of Hungary|Hungary]] and Sweden generated its radar technology during the war.{{citation needed|date=September 2024}}

In France in 1934, following systematic studies on the [[Cavity Magnetron#Split-anode magnetron|split-anode magnetron]], the research branch of the [[Compagnie générale de la télégraphie sans fil]] (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on the ocean liner [[SS Normandie|''Normandie'']] in 1935.<ref>{{cite magazine|title= Radio Waves Warn Liner of Obstacles in Path|magazine= Popular Mechanics|url= https://books.google.com/books?id=x98DAAAAMBAJ&pg=PA844|date= December 1935|publisher= Hearst Magazines|page= 844|access-date= 11 February 2021|archive-date= 7 October 2024|archive-url= https://web.archive.org/web/20241007062109/https://books.google.com/books?id=x98DAAAAMBAJ&pg=PA844#v=onepage&q&f=false|url-status= live}}</ref><ref>Frederick Seitz, Norman G. Einspruch, Electronic Genie: The Tangled History of Silicon  – 1998 – page 104</ref>

During the same period, Soviet military engineer [[Pavel K. Oshchepkov|P.K. Oshchepkov]], in collaboration with the [[Saint Petersburg State Electrotechnical University|Leningrad Electrotechnical Institute]], produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3&nbsp;km of a receiver.<ref>John Erickson. Radio-Location and the Air Defence Problem: The Design and Development of Soviet Radar. ''Science Studies'', vol. 2, no. 3 (Jul. 1972), pp. 241–263</ref> The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following the arrest of Oshchepkov and his subsequent [[gulag]] sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, [[Gneiss-2]], entered into service in June 1943 on [[Petlyakov Pe-2|Pe-2]] dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944.<ref>{{cite web | url=http://kret.com/en/news/3657/ | title=The history of radar, from aircraft radio detectors to airborne radar | work=kret.com | date=17 February 2015 | access-date=28 April 2015 | url-status=dead | archive-url=https://web.archive.org/web/20150620161506/http://kret.com/en/news/3657/ | archive-date=20 June 2015 }}</ref> The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems.

Full radar evolved as a pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American [[Robert Morris Page|Robert M. Page]], working at the [[Naval Research Laboratory]].<ref>Page, Robert Morris, ''The Origin of Radar'', Doubleday Anchor, New York, 1962, p. 66</ref> The following year, the [[United States Army]] successfully tested a primitive surface-to-surface radar to aim [[Coastal artillery|coastal battery]] [[searchlight]]s at night.<ref>{{cite magazine|title= Mystery Ray Locates 'Enemy'|magazine= Popular Science|url= https://books.google.com/books?id=bygDAAAAMBAJ&pg=PA29|date= October 1935|publisher= Bonnier Corporation|page= 29|access-date= 11 February 2021|archive-date= 7 October 2024|archive-url= https://web.archive.org/web/20241007062141/https://books.google.com/books?id=bygDAAAAMBAJ&pg=PA29#v=onepage&q&f=false|url-status= live}}</ref> This design was followed by a pulsed system demonstrated in May 1935 by [[Rudolf Kühnhold]] and the firm {{ill|Gesellschaft für elektroakustische und mechanische Apparate|lt=GEMA|de|GEMA (Radar)}} in Germany and then another in June 1935 by an [[Air Ministry]] team led by [[Robert Watson-Watt]] in Great Britain.

[[File:Watson Radar.jpg|thumb|left|The first workable unit built by [[Robert Watson-Watt]] and his team]]
In 1935, Watson-Watt was asked to judge recent reports of a German radio-based [[death ray]] and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such a system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the [[Daventry Experiment]] of 26 February 1935, using a powerful [[BBC]] shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, [[Hugh Dowding]], the [[Air Member for Supply and Research]], was very impressed with their system's potential and funds were immediately provided for further operational development.<ref name="Alan Dower Blumlein-2002">{{cite web|url=http://www.doramusic.com/Radar.htm |title=The story of RADAR Development |author=Alan Dower Blumlein |year=2002 |access-date=6 May 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110710144447/http://www.doramusic.com/Radar.htm |archive-date=10 July 2011 }}</ref> Watson-Watt's team patented the device in patent GB593017.<ref name="BREVET D'INVENTION-1934">{{cite web|language=fr|url=http://www.radar-france.fr/brevet%20radar1934.htm|title=Nouveau système de repérage d'obstacles et ses applications|trans-title=New obstacle detection system and its applications|url-status=dead|archive-url=https://web.archive.org/web/20090116093441/http://www.radar-france.fr/brevet%20radar1934.htm|archive-date=16 January 2009|work=BREVET D'INVENTION|date=20 July 1934|via=radar-france.fr}}</ref><ref>{{cite press release|url=http://www.patent.gov.uk/media/pressrelease/2001/1009.htm|title=British man first to patent radar|date=10 September 2001|website=Media Centre|publisher=The Patent Office|url-status=dead|archive-url=https://web.archive.org/web/20060719224405/http://www.patent.gov.uk/media/pressrelease/2001/1009.htm|archive-date=19 July 2006}}</ref><ref>{{patent|GB|593017|''Improvements in or relating to wireless systems''}}</ref>

[[File:Chain home.jpg|thumb|upright=0.65|A [[Chain Home]] tower in Great Baddow, Essex, United Kingdom]]
[[File:Watson watt 02 fr.jpg|thumb|left|Memorial plaque commemorating Robert Watson-Watt and [[Arnold Wilkins]]]]
Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British [[Air Ministry]], Bawdsey Research Station located in [[Bawdsey Manor]], near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called "[[Chain Home]]" along the East and South coasts of England in time for the outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the [[Battle of Britain]]; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the "[[Dowding system]]" for collecting reports of enemy aircraft and coordinating the response.

Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting the entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies.