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NEWS | Dec. 13, 2013

The Fleet's First Radar Turns 75

By Donna McKinney

Note: This article was written by Claire Peachey, technical writer/editor in NRL's Technical Information Services.

December 2013 marks the 75th anniversary of one of the Naval Research Laboratory's most important contributions to technology development and national defense: the Fleet's first shipboard radar.

NRL's XAF radar, fondly known as the flying bedspring, was the prototype that showed the Navy what this new radio detecting and ranging system - not yet called radar - was capable of doing. In December 1938, the XAF radar was installed aboard USS New York (BB 34) in preparation for Fleet exercises in the Caribbean in early 1939. During the at-sea exercises, the 200 MHz XAF system successfully spotted aircraft at distances up to 48 miles and ships at 10 miles, and could even follow 14-inch shells in flight. It also detected and pinpointed destroyers making nighttime simulated torpedo attacks. NRL physicist Robert M. Page, one of the developers of the XAF system and inventor of many other radar technologies, was aboard New York and later described the reaction after the mock attacks:

These performances were at night, with no possibility of seeing the destroyers. Their lights were out. That really impressed the officers. From then on they were sold on the stuff and they would give us anything we wanted.
Admiral A.W. Johnson, Commander, Atlantic Squadron, reported after witnessing the demonstrations:

The equipment is one of the most important military developments since the advent of radio itself. Its value as a defensive instrument of war and as an instrument for avoidance of collisions at sea justifies the Navy's unlimited development of the equipment.
XAF's capabilities resulted in the recommendation for immediate procurement of 10 to 20 of the devices in their present form for installation on Fleet vessels.

The NRL system went rapidly to production by RCA as the CXAM and CXAM-1 models, and by the time the United States entered World War II, these radar units were installed on 20 Navy vessels, mainly heavy cruisers, carriers, and battleships. Radar surged in importance, and NRL, which had a wide-ranging program of radio research, developed prototypes of air and submarine radars that were also used during the war. Today, NRL continues to be a leading center for research and development of radar systems.

The XAF radar is still around for its 75th: the deteriorating equipment recently underwent conservation treatment and is on display at the National Electronics Museum in Linthicum, Maryland.

Sources and further reading:
  • D.K. Allison, New Eye for the Navy: The Origin of Radar at the Naval Research Laboratory, NRL Report 8466, Sept. 29, 1981. See especially Ch. 7, From Model to Operational Equipment (1936-1940), pp. 99-112 and references therein.
  • M.A. Simons, The Flying Bedspring: Restoring the US Navy's XAF Radar, 2011 IEEE MTT-S International Microwave Symposium, 5-10 June 2011, Baltimore, MD.
  • U.S. Navy Shipboard Radars - XAF, Naval History and Heritage Command web site:
  • Bedspring Antenna 'Retires' to Museum, NRL Labstracts No. 32, Aug. 7, 1964.
  • 'Flying Mattress' Comes to Rest, The Washington Post, Aug. 21, 1964, p. A16.

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