{{Short description|British naval early-warning radar developed during World War II}} {{Use British English|date=August 2011}} {{Use dmy dates|date=September 2020}} {{Infobox radar |name = Type 281 |image = |caption = |country = United Kingdom |introdate = 1940 |number = 59 |type = Early-warning radar |frequency =86–94 MHz |PRF = 50 per second |beamwidth = 35° (horizontal) |pulsewidth= 2–3 μs or 15 μs |RPM = |range = {{convert|115|nmi|abbr=on|lk=in}} |altitude = {{convert|30000|ft|m}} |diameter = <!--{{m to ft|X|addr=yes}}--> |azimuth = <!--X-Yº--> |elevation = <!--X-Yº--> |precision = <!--±{{m to ft|X|addr=yes}}--> |power = 350 kW–1 MW |other names= }} thumb|281 B Aerial on board {{HMS|Swiftsure|08|6}} at Scapa Flow.
The '''Type 281 radar''' was a British naval early-warning radar developed during World War II. It replaced the Type 79 as the Royal Navy's main early-warning radar during the war.
The prototype system was mounted on the light cruiser {{HMS|Dido|37|6}} in October 1940.<ref>Swords, p. 88</ref> This radar used a frequency of 90 MHz, a beamwidth of 35°, and a wavelength of {{convert|3.5|m|yd|abbr=on}}. It required separate transmitting and receiving antennas that were rotated by hand. For long-range warning the radar used a 15 microsecond pulse at a power level of 350 kW that gave a detection range up to {{convert|110|nmi|lk=in}} for aircraft. For tracking surface targets it used a 2–3 microsecond pulse at 1 MW that gave a range up to {{convert|12|nmi}}. A second set was installed in January 1941 aboard the battleship {{HMS|Prince of Wales|53|6}} and production began of another 57 sets, with the first ones delivered the following month.<ref>Mitchell, pp. 8–10</ref><ref>Swords, p. 88</ref> This set also had a secondary aerial and surface gunnery capability, and used a Precision Ranging Panel. The Type 281 ranging system allowed the user to select either a {{convert|2000|yd|-1}} to {{convert|14000|yd|-1}} or a {{convert|2000|yd|-1}} to {{convert|25000|yd|-1}} range display with range accuracies of {{convert|50|yd|-1}} or {{convert|75|yd|-1}} RMS, respectively. Aerial target ranges were passed directly to the HACS table (fire control computer).<ref>Pout, pp. 13–16.</ref>
Type 281B consolidated the transmission and receiving antennas, and the Type 281BP radar had the short-pulse feature removed. It was fitted with improved receivers that increased the maximum detection range for an aircraft at {{convert|20000|ft|-1}} to {{convert|120|nmi}}. At lower altitudes, ranges declined to {{convert|90|nmi}} at {{convert|10000|ft|-1}} and {{convert|65|nmi}} at {{convert|5000|ft|-1}}. The Type 281BQ was a Type 281BP fitted with power rotation, at 2 or 4 rpm, and equipped with a plan position indicator. After the end of the war the Type 281 was replaced by the Type 960 radar.<ref>Friedman, p. 194</ref>
==Notes== {{Reflist|30em}}
==Bibliography== *{{cite book|last=Brown|first=Louis|title=A Radar History of World War II: Technological and Military Imperatives|publisher=Institute of Physics Publishing|location=Bristol and Philadelphia|year=1999|isbn=0-7503-0659-9}} *{{cite book|last=Friedman|first=Norman|title=Naval Radar|year=1981|publisher=Conway Maritime Press|location=London|isbn=0-85177-238-2}} *{{cite book|editor=Kingsley, F.A.|title=The Application of Radar and other Electronic Systems in the Royal Navy in World War 2|chapter=Weapon Direction in the Royal Navy|author=Pout, H.W.|year=1995|publisher=Macmillan|location=London|isbn=0-333-62748-2}} *{{cite book|editor=Roberts, John|title=Warship IV|chapter=The Development of Radar in the Royal Navy (1935–45), Part I|author=Mitchell, Alastair|year=1980|publisher=Conway Maritime Press|location=London|isbn=0-85177-205-6}} *{{cite book|last=Swords|first=Sean S.|title=Technical History of the Beginnings of Radar|publisher=IEE/Peter Peregrinus|location=London|year=1986|isbn=0-86341-043-X}} *{{cite book|last=Watson|first=Raymond C. Jr.|title=Radar Origins Worldwide: History of Its Evolution in 13 Nations Through World War II|publisher=Trafford|year=2009|isbn=978-1-4269-2111-7}}
==External links== * [https://web.archive.org/web/20090406203547/http://www.rnmuseumradarandcommunications2006.org.uk/index.html The RN Radar and Communications Museum ]
Type 279 radar Category:Naval radars Category:World War II radars Category:Royal Navy Radar