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Early U.S. Navy Experimental Radars

Department of the Navy - Naval Historical Center
805 Kidder Breese SE
Washington, D.C.  20374-5060

Online Library of Selected Images:
Weapons and Sensors -- RADAR

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.
While performing searches for various engineering topics, it is often difficult to locate the desired material. That is because many documents are either buried deep within the results, or they are never indexed by the search engines in the first place. Government websites are good sources of information, but it typically takes doing multiple hit-and-miss searches within the website's database to find information. As time permits, I have been re-publishing documents that I find so that the search engines will index them.

Unless otherwise marked, U.S. government documents may be freely copied so long as the content is not altered from the original. Warning: Some of these documents have been processed with optical character recognition (OCR) software and might contain errors.

Building 821: Radar Test Building

Development of a Radar/SAR Assimilation System for
    Internal Wave Prediction
Early U.S. Navy Experimental Radars

Improved Doppler Radar/Satellite Data Assimilation

• Learning Morse Code Characters: A Replication of
   the Keller Method

Meteorological Studies with the Phased Array Weather
    Radar and Data Assimilation Using the Ensemble
    Kalman Filter

Pearl Harbor Revisited: U.S. Navy Communications
    Intelligence, 1924-1941

Radar Cross-Section Observations of the Echo I
    Communications Satellite

Radio and Radar World War I & World War II,
    U.S. Army Signal Corps

What Is Radar?

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.

Photo #: NH 41639

28 Megacycle Radar Antenna

Used by the U.S. Naval Research Laboratory (NRL) for detection of aircraft by beat method in 1930, and for radar (pulse technique) in 1936.

Official U.S. Navy Photograph, from the collections of the Naval Historical Center.

Online Image: 89KB; 900 x 675 pixels
28 Megacycle Radar Antenna
Photo #: NH 105853

Experimental Pulse Radar Transmitter

Photographed at the U.S. Naval Research Laboratory, Washington, D.C., 1936.

Official U.S. Navy Photograph, from the collections of the Naval Historical Center.

Online Image: 102KB; 660 x 925 pixels
Experimental Pulse Radar Transmitter
Photo #: NH 51280

First Test of Radar on Board Ship

U.S. Naval Research Laboratory's 200 megacycle radar equipment on USS Leary (DD-158) in April 1937.
The radar antenna was mounted on the barrel of one of the ship's 4"/50 guns (visible at right), allowing it to be trained in azimuth and elevation.

Official U.S. Navy Photograph, from the collections of the Naval Historical Center.

Online Image: 122KB; 900 x 665 pixels
First Test of Radar on Board Ship
Photo #: NH 41640

First Rotating Beam Radar

(200 megacycle radar used for transmitting and receiving)

Developed by the U.S. Naval Research Laboratory (NRL) in 1937.

Official U.S. Navy Photograph, from the collections of the Naval Historical Center.

Online Image: 166KB; 795 x 925 pixels
First Rotating Beam Radar
Photo #: NH 41638

First Rotating Beam Radar Antenna

(for 200 megacycle radar used for transmitting and receiving)

Developed by the Naval Research Laboratory (NRL) in 1937.
This view shows the antenna installed "topside" on a NRL building in Anacostia, District of Columbia, at about that time.
"This was a so-called 'dirigible' antenna, meaning it is so mounted that it can be turned to allow for around-the-compass search." (quoted from the original picture caption, released on 14 August 1945.)

Official U.S. Navy Photograph, from the collections of the Naval Historical Center.

Online Image: 120KB; 725 x 925 pixels
First Rotating Beam Radar Antenna

See the original version of Early U.S. Navy Experimental Radar .

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