Early U.S. Navy Experimental Radars
Department of the Navy - Naval Historical Center
Online Library of Selected Images:
What Is Radar?
Among the many early observations that relatively distant objects could interfere with radio reception, was a 1922 report by Dr. A. Hoyt Taylor and Leo Young, of the Naval Aircraft Radio Laboratory, noting that that a Potomac River steamer had distorted radio reception as it passed their facility. The report continued: "destroyers located on a line a number of miles apart could be immediately aware of the passage of an enemy vessel between any two destroyers of the line, irrespective of fog, darkness, or smoke screen.". No action was taken on this report, but those involved remembered what they had seen.
In 1930 the Naval Research Laboratory ("NRL", into which the earlier Naval Aircraft Radio Laboratory had been absorbed in 1923) discovered that aircraft flying in the vicinity of a radio antenna array disturbed reception enough to provide warning of their presence. By that time the Navy had become very aware of the deadly threat posed by previously unseen airplanes, and the Bureau of Engineering (which controlled NRL) authorized further investigation of radio technology as a means of detection. By 1932, enough experience had been gained to make clear that a land-based system, using an perimeter ring of transmitters with receivers located some distance away, could reliably detect aircraft approaching a city or other fixed position. However, the required equipment separation meant that this arrangement would only be useful on land. It was therefore of slight Naval value, though the U.S. Army was definitely interested.
Over the next several years, considerable advances in pulse radio technology made it possible for transmitters and receivers to employ a single antenna. In 1936 the same 28 megacycle radio array that had been used for earlier NRL experiments was successfully adapted for pulse transmission and reception, detecting and locating aircraft 25 miles away. Also during the 1920s and early 1930s improvements in vacuum tubes provided sufficient power to allow use of higher radio frequencies, thus permitting smaller antennas. A shipboard radar** was now definitely possible. NRL soon developed a 200 megacycle (1.5 meter wave length) set that was, in April 1937, tested at sea on board the destroyer Leary (DD-158). Another year-and-a-half of challenging technical work, among it the development of 200 MC equipment with a rotating antenna, led to construction of a set that was suitable for serious operational testing. This was the XAF Radar, which is the subject of a separate presentation.
** The term "RADAR", derived from "RAdio Detection And Ranging", was not actually coined for several more years.
Source note: The information in this text is taken from the following sources: Captain L.S. Howeth, USN: History of Communications-Electronics in the United States Navy, Chapter XXXVIII (Washington, D.C., 1963); and Norman Friedman: Naval Radar (Greenwich, England, 1981).
This page provides images concerning U.S. Navy experimental radars developed during the early and middle 1930s.
For additional information on World War II era radar, see the Navy Department Library's "Online Reading Room" presentation:
" U.S.Radar - Operational Characteristics of Radar, Classified by Tactical Application" -- publication FTP 217, 1 August 1943.
See the original version of Early U.S. Navy Experimental Radar .