The CXAM radar system was the first production radar system deployed on United States Navy ships, operating in the mid-high VHFfrequency 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 were denoted "CXAM" and were a fusion of XAF and CXZ technologies. These were installed on the battleship, the aircraft carrier , and the heavy cruisers,,, and. The next 14 units RCA produced were denoted "CXAM-1" and were slight improvements over the CXAM design. These were installed on the battleships Texas,,,, 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, distance to the horizon, 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 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.
