View source for SJ radar

{{Short description|WW2 American radar set for submarines}}
{{Use American English|date=October 2024}}
{{Use dmy dates|date=October 2024}}
{{Infobox radar
| name        = SJ radar
| image       =[[File:Radar and Electronic Warfare 1939-1945 FL4028.jpg|290px]] 
| caption     = SJ radar on British submarine {{HMS|Tiptoe|P332|6}}
| country     = USA<ref name="JourdanMoulin2015">{{cite book|author1=John Jourdan|author2=Jean Moulin|title=French Destroyers: Torpilleurs d'Escadre and Contre-Torpilleurs,1922Ð1956|url=https://books.google.com/books?id=v2hhCgAAQBAJ&pg=PA291|date=22 June 2015|publisher=Seaforth Publishing|isbn=978-1-84832-198-4|pages=291–}}</ref>
| introdate   = June 1942<ref name=naval-radar/>
| number      =
| type        = Surface Search, limited air search capabilities.
| frequency   = S-band (10cm wavelength)<ref name=naval-radar/>
| PRF         = 1350-1650 <ref name=naval-radar>{{cite book |title=Naval Radar |last=Friedman |first=Norman |page=149 |publisher=Conway Maritime Press|year=1981}}</ref>
| beamwidth   = 7.5° × 13°<ref name=naval-radar/>
| pulsewidth  = 1 μs
| RPM         = <!--revolutions per minute-->
| range       = 
| altitude    = <!--{{convert|X|m|ft|abbr=on}}-->
| diameter    = <!--{{convert|X|m|ft|abbr=on}}-->
| azimuth     = <!--X-Yº-->
| elevation   = <!--X-Yº-->
| precision   = 
| power       = 
| other names =
}}

'''SJ radar''' was a type of [[S band]] (10-cm) [[radar]] set used on [[United States|American]] [[submarine]]s<ref name="Nebeker2009">{{cite book|author=Frederik Nebeker|title=Dawn of the Electronic Age: Electrical Technologies in the Shaping of the Modern World, 1914 to 1945|url=https://books.google.com/books?id=3u-bCgAAQBAJ&pg=PA430|date=30 March 2009|publisher=John Wiley & Sons|isbn=978-0-470-26065-4|pages=430–}}</ref> during the [[Second World War]].<ref name="RADAR">{{cite journal |author=Macintyre |first=Donald |date=September 1967 |title=Shipborne Radar |url=https://www.usni.org/magazines/proceedings/1967/september/shipborne-radar |journal=Proceedings |publisher=United States Naval Institute |volume=93 |issue=9}}</ref>  The widespread use of the SJ radar, combined with the very low use of radar in the [[Imperial Japanese Navy]], gave great operational flexibility to the [[United States Navy]]'s submarine campaign in the [[Pacific Ocean]].<ref>[http://www.valoratsea.com/subwar.htm Battle Beneath the Waves: WWII U.S. Submarines at War in the Pacific]</ref>

The first prototype SJ was deployed in December 1941,<ref name="Microwave Radar at War">{{usurped|1=[https://web.archive.org/web/20020404143035/http://www.vectorsite.net/ttwiz4.html Microwave Radar at War]}}</ref> but it was mid-1942 before they became common equipment.  SJ radar was on all submarines by early 1943.<ref name="RADAR"/>  The SJ was the second type of radar deployed on submarines during the war, representing a substantial improvement over the previous [[SD radar]]. The SJ was a variant of the [[SG radar|SG]] surface search radar used on surface warships, contained in sets capable of fitting through submarine hatches for installation and designed to lie close to the curved hulls.

The SJ provided directional and distance information about surface contacts as well as low-flying [[aircraft]].<ref>[http://www.maritime.org/doc/radar/part4.htm United States Navy Radar Operator's Manual - April 1945]</ref>

The SJ radar was even used as a communications device.  When used with a telegraph key, the SJ radar could send signals on a point-to-point basis between two submarines operating in a [[Wolfpack (naval tactic)|wolf pack]].<ref name="Microwave Radar at War"/>  The directionality of the antenna and the short range provided relatively high security for this transmission.

The museum submarines {{USS|Cobia|SS-245}} and  {{USS|Cod|SS-224}} have an operating example of the radar.<ref>{{cite web|url=http://www.wisconsinmaritime.org/the-submarine-experience/uss-cobia/cobia-restoration/ |title=WWII Submarine - USS ''Cobia''|accessdate=18 October 2010}}</ref>

==Variants==
* '''SJ:''' First version.<ref name=naval-radar/>
* '''SJa:''' Field modification, additional power (50kW) compared to initial version.<ref name=naval-radar/>
* '''SJ-1:''' 300 built.<ref name=naval-radar/> New, perforated parabolic antenna design. Surface search range increased to over thirty miles.<ref>{{cite book |title=World War II in the Pacific: An Encyclopedia |editor-last=Sandler |editor-first=Stanley |publisher=Garland Publishing, Inc. |year=2001 |ISBN=0-203-80165-2 |page=983 |url=https://books.google.com/books?id=5iT6orBAT0gC}}</ref>

==References==
{{reflist}}

[[Category:Military radars of the United States]]
[[Category:World War II American electronics]]
[[Category:World War II radars]]
[[Category:Naval radars]]
[[Category:Military equipment introduced from 1940 to 1944]]

{{US-Navy-stub}}