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Searchlight, Radar, and AAA Defense
Image Gallery III

A battery-powered mobile searchlight invented by Thomas Edison.

A WW I French searchlight crew with their truck-mounted light.
(click on the photo to view an enlargement in a new window).

These WW I French troops demonstrate a portable searchlight.

Not to be outdone by French ingenuity, these WW I German soldiers
demonstrate a searchlight that can be raised and lowered.

A British searchlight truck (date unknown).

An early sound locator fitted with conical "ears."
Note the operator with headphones on.

This 1927-model sound locator was equipped with a corrector designed
to compensate for the time lag resulting from the slow speed of sound
arriving at the detector from the plane. All such correctors predict the course
of the plane on the basis of its measured speed and angular velocities,
but cannot correct for evasive action by the pilot.

Forties pinup girl Susan Hayward poses with a 1930s Hollywood searchlight
(click on the photo to view an enlargement in a new window).

Searchlight trucks of the 14th Infantry set up and ready for action at Fort Davis next to the Gatun Locks, Panama Canal Zone, during the mid-1930s. You can see the black mechanical "ears" of four sound locators in this shot. The town of Gatun is in the background. (Photo courtesy The Early Days of Fort William Davis.)

Close-up of searchlight trucks at Fort Davis, Panama Canal Zone, during the 1930s. Searchlights were used in conjunction with mechanical sound locators (note a folded-up sound locator at extreme left) for aircraft detection and illumination to direct the fire of antiaircraft guns. (Photo courtesy The Early Days of Fort William Davis.)

A 60-inch searchlight and power unit. Electrical power was provided by a 15-kW generator mounted on a Cadillac truck chassis. This rig belonged to the 240th Coast Artillery Regiment (Harbor Defense), which defended the approaches to Portland, Maine from Fort Williams during WW II. This photo dates from the early- to mid-1930s.

A 1935 model sound locator. Development of heat or radio detection equipment was made urgent by the breakdown of sound location at maneuvers of Army antiaircraft and Air Corps units in 1933 and 1936. This photograph shows a sound locator in use during the First Army Maneuvers, Pine Camp, New York, August 1935. (U.S. Signal Corps photo, via InfoAge.)

2 x 6 azimuth array for 100 megacycles. Lacking vertical directivity, it served for azimuth readings only. Here we have the humble beginnings of the SCR-268 "bedspring" antenna that would become so familiar to the 225th. (U.S. Signal Corps photo, via InfoAge.)

A radio pulse transmitter shown during testing in 1937. This directional array was comprised of ten horizontal dipoles with an equal number of reflectors. (U.S. Signal Corps photo, via InfoAge.)

A 1937 photo of an elevation receiving antenna. This radar antenna was especially designed by the laboratories for vertical directivity, permitting reading of angular elevation of the target. In conjunction with slant range measurement, this made it possible to determine the height of the detected airplane. (U.S. Signal Corps photo, via InfoAge.)

240-megacycle radio detector, built in 1937 to utilize the more compact antenna structures suitable at higher frequencies. Both transmitter and receiver were mounted on a single sound-locator chassis. The equipment was tested against both aircraft and meteorological balloons. (U.S. Signal Corps photo, via InfoAge.)

An 8 x 4 dipole antenna array feeding received radio echoes into the azimuth receiving set and slant range finder. This receiving equipment was built by the Signal Corps Laboratories in the spring of 1937 on a sound locator chassis. (U.S. Signal Corps photo, via InfoAge.)

This photograph shows the ultimate combination of the Corps of Engineers and Signal Corps heat detectors, as used in conjunction with radio detection in 1937. Thermopiles and control equipment designed by the Signal Corps Laboratories were mounted in a mechanical structure previously built by the General Electric Company. As operated in 1937, the heat detector received directional data from the radio equipment (part of one antenna may be seen at right) and in turn controlled the pointing of a searchlight. (U.S. Signal Corps photo, via InfoAge.)

The first use of electromagnetic energy to locate aircraft was the searchlight. This spectacular night photograph shows how the light beams diverge and diminish in intensity with increasing distance. If our eyes were tuned to the radio portion of the spectrum, the sharply focussed beams of microwave radar might look something like these. Searchlights are of limited range and are impeded by clouds. In addition, they give away their position while searching for the target. The first U.S. Army radio detectors were developed to control the pointing of searchlights so as to put them instantaneously on the target. (U.S. Signal Corps photo, via InfoAge.)


A coastal searchlight mounting near the British Home Fleet naval base
at Scapa Flow (click on the photo to view an enlargement in a new window).

A British searchlight crew probes the sky for the Luftwaffe
somewhere on the southern English coast, 1940.

Another view of a British light crew.

An awesome display of AAA lights over London during the Blitz.

A British sound locator in action (this, and the photo directly
above, courtesy London at War).

Pre-war training with a GE searchlight at Ft. Sheridan, Illinois.

Late 1930's searchlight and sound locator — the backbone of AAA detection
technology at the time.

Closeup of the controls of an SCR-268 radar set.

Diagram showing an SCR-270 radar set being deployed.

SCR-270 radar set on the coast of New Guinea.

From the European Theater of operations comes this photograph of an SCR-268
radar set manned by elevation, azimuth and range operators (seated). The pulse
transmitter is in the center, with identification antenna above, azimuth receiving
antenna at left, transmitting antenna at right, and elevation receiving antenna at extreme right (the unit and location are unknown).

American SCR-268 and searchlight dug in, North Africa, 1942.

SCR-270-DA radio (radar) set as depicted in the unit's technical operations manual. This was the same type of radar that detected the Japanese air armada approaching Pearl Harbor on the morning of December 7, 1941.

SCR-270 preserved at the Historical Electronics Museum.

WW II German searchlight on display in a German museum.
(click on the photo to view an enlargement in a new window).

German searchlight crew in action; a sound locator can be seen in the background.

A German light hunts for British bombers.

An American GI inspects a German searchlight, which seems to have been fixed
with a "shroud" (note camouflaged appliance attached to light at left),
perhaps jerry-rigged by the crew to control the spread of the beam.

Australian coastal defense searchlight at Ft. Lytton, Brisbane.
The light has been mounted on a sort of narrow-guage rail
system so it can be moved easily from its protective structure
(click on the photo to view an enlargement in a new window).

An American 60-inch searchlight in action in Korea.

Another post-war view of a 60-inch light.


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