CXAM radar. The CXAM radar system was the first production radar system deployed on United States Navy ships, operating in the mid-high VHF frequency band of 200 MHz. It followed several earlier prototype systems, such as the NRL radar installed in April 1937 on the destroyer ; its successor, the XAF, installed in December 1938 on the battleship ; and the first RCA-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), 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 US Army's first non-prototype radar system, the SCR-270, was developed in parallel with the CXAM.

Variants
 CXAM First version, six produced and installed July and August 1940.
 CXAM-1 Second version. Non-elevating antennas, servo improvements, and improved accuracy. Delivered starting late 1941 with fourteen units produced.

Platforms

CXAM
 -Installed between July and August 1940, removed after sinking at Pearl Harbor. Unit subsequently installed as Army search set on Oahu and later transferred to  in the summer of 1942.
 -Installed between July and August 1940 with initial delivery of CXAM
 -Installed between July and August 1940 with initial delivery of CXAM
 -Installed between July and August 1940 with initial delivery of CXAM
 -Installed between July and August 1940 with initial delivery of CXAM
 -Installed between July and August 1940 with initial delivery of CXAM
 -Received unit from   Summer of 1942.

CXAM-1
 s
 s

References

External links
U.S. Radar, Operational Characteristics of Radar Classified by Tactical Application, FTP 217
History of US radar development.
History of US radar development, with more detail on CXAM.
Initial installations of CXAM.
Date of Yorktown installation.
Date of Yorktown testing with CXAM.
 Radar and the Fighter Directors, Chapter 6: The CXAM Goes to War
Naval radars
World War II American electronics
World War II radars
Military radars of the United States
Military equipment introduced from 1940 to 1944