The CXAM radar system was the first production

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

system deployed on

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

ships, operating in the mid-high

VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...

frequency band of 200 MHz. It followed several earlier prototype systems, such as the

NRL The National Rugby League (NRL) is an Australasian rugby league club competition which contains clubs from New South Wales, Queensland, Victoria, the Australian Capital Territory and New Zealand. The NRL formed in 1998 as a joint partnership ...

radar installed in April 1937 on the destroyer ; its successor, the XAF, installed in December 1938 on the battleship ; and the first

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

-designed system, the CXZ, installed in December 1938 or January 1939 on the battleship . Based on testing in January 1939, where the XAF was more reliable, the US Navy ordered RCA to build six XAF-based units for deployment and then shortly thereafter ordered 14 more. The first six units RCA produced (delivered in 1940) were denoted "CXAM" and were a fusion of XAF and CXZ technologies. These were installed on the battleship , the aircraft carrier (in September 1940), and the heavy cruisers , , , and . The next 14 units RCA produced (also delivered in 1940) were denoted "CXAM-1" and were slight improvements over the CXAM design. These were installed on the battleships ''Texas'' (in October 1941), , , , and ; on the aircraft carriers , , , , and ; on the heavy cruiser ; on two light cruisers; and on the seaplane tender . Radar detection range of aircraft depends on altitude, size, and number of the target aircraft, as well as the radar's characteristics, such as transmitter power and receiver sensitivity. Surface ships are more difficult to detect due to a number of factors such as signal return from waves (called in general

ground clutter Clutter is a term used for unwanted echoes in electronic systems, particularly in reference to radars. Such echoes are typically returned from ground, sea, rain, animals/insects, chaff and atmospheric turbulences, and can cause serious performan ...

), distance to the horizon (due to the curvature of the earth), elevation of the radar antenna, height of the target above the sea surface, and water vapor in the air. These factors serve to reduce the range at which a surface target can be detected when compared to aircraft. The CXAM is listed (in U.S. Radar, Operational Characteristics of Radar Classified by Tactical Application) as being able to detect single aircraft at and to detect large ships at . Other sources list CXAM detection range on aircraft out to . ''Lexington'''s CXAM-1 detected the incoming Japanese carrier aircraft strike at a range of during the

battle of the Coral Sea The Battle of the Coral Sea, from 4 to 8 May 1942, was a major naval battle between the Imperial Japanese Navy (IJN) and naval and air forces of the United States and Australia. Taking place in the Pacific Theatre of World War II, the batt ...

. The US Army's first non-prototype radar system, the

SCR-270 The SCR-270 (Set Complete Radio model 270) was one of the first operational early-warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world. It is also known as the Pearl Harbor ...

, was developed in parallel with the CXAM.

Notes

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References

U.S. Radar, Operational Characteristics of Radar Classified by Tactical Application, FTP 217
Naval radars World War II American electronics World War II radars Military radars of the United States Military equipment introduced from 1940 to 1944