{{short description|Radar of the United States Navy}} {{Infobox radar|name=SK (radar)|image=File:SK-1 radar on USS Kasaan Bay (CVE-69) 1944.jpg|caption=SK-1 aboard {{USS|Long Island|CVE-1|6}}|country=United States|type=Air-search radar|introdate=1944|power=250 kW<ref name="nw"/>|frequency=VHF band|range=160.9 km (86.9 nmi)|manufacturer=General Electric|beamwidth=10°|pulsewidth=5 μs|PRF=|precision=± {{cvt|100|yd|m|lk=in}}|azimuth=± 3 °}}
'''SK''' was an American-made air-search radar used during World War II by the United States Navy. Models included '''SK-1''', '''SK-2''' and '''SK-3'''.<ref>{{Cite book|last=Robert|first=Buderi|title=The Invention That Changed the World: How a Small Group of Radar Pioneers Won the Second World War and Launched a Technical Revolution|publisher=Touchstone|year=1998|isbn=0684835290}}</ref>
== Overview == SK was a very high frequency search set for large ships. It furnished range and bearing of surface vessels and aircraft, and it could be used for control of interception. It was essentially an SC-2 radar set operating at 200MHz with a larger antenna using 6×6 dipoles.<ref>{{cite web|url=https://www.radartutorial.eu/19.kartei/11.ancient2/karte043.en.html |title=SK (Radartutorial.eu)}}</ref> The set had both "A" and PPI scopes, provisions for operating with remote PPIs and for IFF connections, and built-in BL and BI antennas.<ref name=":0">{{Cite web|title=US Radar: Operational Characteristics of Radar Classified by Tactical Application|url=https://www.history.navy.mil/content/history/nhhc/research/library/online-reading-room/title-list-alphabetically/u/operational-characteristics-of-radar-classified-by-tactical-application.html|access-date=2022-02-18|website=NHHC|language=en-US}}</ref>
With the antenna at {{cvt|100|ft|m}}, SK could detect medium bombers at {{cvt|1,000|ft|m}} altitude at {{convert|100|mi|km}}. Range accuracy was ± {{convert|100|yd|m}} and azimuth accuracy ± 3°. There was no elevation control, but elevation could be estimated roughly from positions of maximum and minimum signal strength.<ref name=":0" />
Shipment for SK included spares, with tubes for 400 hours, and a separate generator if the ship's power is DC. SK was not air transportable.
SK had 10 components weighing approximately {{cvt|5000|lb|kg}}. The heaviest unit, at {{cvt|2400|lb|kg}}, was the antenna assembly. The antenna measured {{cvt|15|ft|m}} x {{cvt|16|ft|9|in|m}}. It was mounted {{cvt|100|ft|m}} or more above water. The minimum operators required were one per shift. Primary power required was 3500 watts, 115 volts, 60 Hz. The source of power is ship's power of 115 volts, 60 Hz.<ref name=":0" />
During the later stages of World War II, a parabolic antenna called SK-2 replaced the SK-1.<ref name="nw">{{Cite web|title=Radar Equipment of World War II|url=http://www.navweaps.com/Weapons/WNUS_Radar_WWII.php|website=NavWeaps}}</ref>
== On board ships ==
=== {{Flagicon|United States|variant=naval}} United States === * thumb|SK-2 aboard {{USS|Coral Sea|CV-43|6}}{{sclass|Midway|aircraft carrier}} * {{sclass|Essex|aircraft carrier}} * {{sclass|Independence|aircraft carrier}} * USS ''Enterprise'' (CV-6) * USS ''Saratoga'' (CV-3) * {{sclass|Casablanca|escort carrier}} * {{sclass|Bogue|escort carrier}} * thumb|SK-1 aboard {{USS|Honolulu|CL-48|6}}{{sclass|Iowa|battleship}} * ''South Dakota''-class battleship * {{sclass|North Carolina|battleship}} * {{sclass|Colorado|battleship}} * {{sclass|Tennessee|battleship}} * USS ''Pennsylvania'' (BB-38) * thumb|SK-1 aboard {{USS|Augusta|CA-31|6}}{{sclass|Nevada|battleship}} * {{sclass|New York|battleship}} * USS ''Arkansas'' (BB-33) * {{sclass|Alaska|cruiser}} * {{sclass|Des Moines|cruiser}} * {{sclass|Oregon City|cruiser}} * {{sclass|Baltimore|cruiser}} * USS ''Wichita'' (CA-45) * {{sclass|Fargo|cruiser}} * {{sclass|Cleveland|cruiser}} * {{sclass|New Orleans|cruiser}} * {{sclass|Brooklyn|cruiser}} * {{sclass|Portland|cruiser}} * {{sclass|Northampton|cruiser}} * {{sclass|Pensacola|cruiser}} * {{sclass|Omaha|cruiser}} * {{sclass|Currituck|seaplane tender}} * {{sclass|Appalachian|command ship}} * {{sclass|Mount McKinley|command ship}} * ''Commencement Bay''-class escort carrier
=== {{Flagicon|United Kingdom|variant=naval}} United Kingdom === * {{sclass|Ruler|escort carrier}} * HMS ''Boxer'' (F121)
== Gallery == <gallery mode="packed"> File:Grumman Avenger landing on HMS Trumpeter WWII IWM A 24282.jpg|SK-1 aboard {{HMS|Trumpeter|D09|6}} File:Battleship Texas - exterior - DSCN0165.JPG|SK-1 aboard {{USS|Texas|BB-35|6}} File:USS Wichita (CA-45) underway in the Central Pacific on 2 May 1944.jpg|SK-1 aboard {{USS|Wichita|CA-45|6}} File:USS Alabama - Mobile, AL - Flickr - hyku (195).jpg|SK-2 aboard {{USS|Alabama|BB-60|6}} File:USS Macon (CA-132) underway off the Philadelphia Navy Yard on 29 October 1946.jpg|SK-2 aboard {{USS|Macon|CA-132|6}} File:Radars of USS Princeton (CV-37) in 1952.jpg|SK-3 aboard {{USS|Princeton|CV-37|6}} </gallery>
== See also ==
* List of radars * Radar configurations and types * Air-search radar
== Citations == <references />
== References ==
* Norman Friedman (2006). ''[https://books.google.com/books/about/The_Naval_Institute_Guide_to_World_Naval.html?hl=ja&id=4S3h8j_NEmkC The Naval Institute Guide to World Naval Weapon Systems]''. Naval Institute Press. {{ISBN|978-1-55750-262-9}} * Buderi, Robert (1998). ''The Invention That Changed the World: How a Small Group of Radar Pioneers Won the Second World War and Launched a Technical Revolution.'' Touchstone. {{ISBN| 0-684-83529-0}} * Hezlet, Arthur (1975). ''Electronics and Sea Power. New York: Stein and Day''. {{ISBN|0-8128-1811-3}}
Category:Naval radars Category:World War II radars Category:Military equipment introduced from 1940 to 1944 Category:Military radars of the United States