SJ radar was a type of

S band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the convention ...

(10-cm) radar set used on

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s during the Second World War. 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. The first prototype SJ was deployed in December 1941,Microwave Radar at War
/ref> but it was mid-1942 before they became common equipment. SJ radar was on all submarines by early 1943. 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 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 information, provided highly accurate distance information, and provided information about surface contacts as well as low-flying aircraft. 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

wolf pack A pack is a social group of conspecific canines. Packs aren't formed by all canines, especially small sized canines like the Red fox. The number of members in a pack and their social behavior varies from species to species. Social structure is v ...

. The directionality of the antenna and the short range provided relatively high security for this transmission. The museum sub has an operating example of the radar.

References

Military radars of the United States World War II American electronics World War II radars Naval radars Military equipment introduced from 1940 to 1944 {{US-Navy-stub