Signal Corps Laboratories

Signal Corps Laboratories (SCL) was formed on June 30, 1930, as part of the U.S. Army Signal Corps at Fort Monmouth, New Jersey. Through the years, the SCL had a number of changes in name, but remained the operation providing research and development services for the Signal Corps.

Background

At the beginning of World War I in 1917, the U.S. Army Signal Corps opened a training facility named Camp Vail in east-central New Jersey. This facility was named after Alfred Vail, an inventor associated with Samuel F. B. Morse. Later that year, the Army established the Signal Corps Radio Laboratories at Camp Vail, devoted to research in radio and electronics. The overall installation was upgraded and became Fort Vail.

Under the direction of Col. (Dr.) George Owen Squier, the Radio Laboratories centered on the standardization of vacuum tubes and the testing of equipment manufactured for the Army by commercial firms. Experimentation was also being done on radio communications with aircraft, detection of aircraft using sound and electromagnetic waves, and meteorology. Squier had earlier made a major contribution to communications by developing multiplexing, for which he was elected to the National Academy of Sciences in 1919.

After the end of World War I, aviation communication was transferred to the Signal Corps Aircraft Radio Laboratory at Wilbur Wright Field in Dayton, Ohio. The Radio Laboratories at Camp Vail continued at a low level, centering on design and testing of radio sets, field telephone and telegraph equipment, and meteorology. The facility survived as an Army installation by the Signal Corps moving all of its schools to Camp Vail, with the consolidation named the Signal School.

In 1925, Fort Vail was renamed Fort Monmouth. Although overshadowed by the Signal School and at a reduced scale due to budget restrictions, the Radio Laboratory remained an important activity at Fort Monmouth. Developments included a variety of radios for voice and Morse code communications. Coupling capabilities in electronics and meteorology, in 1929 the Laboratory developed and launched the first radio-equipped weather balloon.

Formation

By 1929, decline in economic conditions forced the consolidation of the Signal Corps' widespread laboratories. In the interest of “economy and efficiency,” the National Bureau of Standards moved the Signal Corps Electrical Laboratory, the Signal Corps Meteorological Laboratory, and the Signal Corps Laboratory at the Bureau of Standards to Fort Monmouth. Upon arriving at their destination, the research facilities were combined with the Radio Laboratory already at Fort Monmouth to form what became known as the Signal Corps Laboratories. In 1930, the Signal Corps transferred the Subaqueous Sound Ranging Laboratory from Fort H. G. Wright, New York to Fort Monmouth as well. On June 30, 1930, the SCL had a personnel strength of 5 officers, 12 enlisted men, and 53 civilians. Major (Dr.) William R. Blair was named Director.

The SCL was responsible for the Army's ground radio and wire communication development and for improvement of the meteorological service. The next year, this Laboratory was also made responsible for research in the detection of aircraft by acoustics and electromagnetic radiation. While the number of personnel was inadequate for major work in these many and diverse areas, Blair, the Director, was personally knowledgeable in all of them.

During the 1920s, the Army Ordnance Corps at Frankford Arsenal had made tests in detecting infrared emitted from airplane engines or reflected by their surfaces. When the SCL was formed, this work was transferred to that Laboratory. Carrying this forward, in 1931, Blair initiated Project 88, "Position Finding by Means of Light." Here "light" was used in the general sense of electromagnetic radiation, including infrared and very short-length (microwave) radio waves.

Initially, emphasis was placed on special devices with high-gain amplification for detecting reflected infrared from an illuminating searchlight. In August 1932, this equipment was used to track a blimp at a distance of over a mile. Further pursuit of active detection techniques was then abandoned because of the limit of infrared energy available from searchlight sources.

Although research continued at the SCL in the passive detection of infrared emitted from heated aircraft engines, Blair became convinced that practical detection systems would involve reflected radio signals. He was certainly influenced in this by his earlier doctoral research in this field, and he was aware of the work on radio detection at the United States Naval Research Laboratory (NRL) in Washington, D.C. In December 1930, representatives of the SCL had been briefed at the NRL on the beat-interference phenomena that they were investigating, and in 1932, an NRL report on radio interference for target-detection was passed on to the Army. It does not appear, however, that any of this information was used by Blair.

Radio-based target detection

The SCL's first definitive efforts in radio-based target detection started in 1934 when the Chief of the Army Signal Corps, after seeing a microwave demonstration by RCA, suggested that radio-echo techniques be investigated. Emphasis was placed on assessing capabilities of the existing microwave tubes, including a German-built Hollmann tube with an output at 50 cm (600 MHz), and a 9-cm (3-GHz) magnetron on loan from RCA. Neither of these devices produced sufficient power for use in detection systems.

At the time, nine wooden buildings built in 1918 housed the activities of the SCL, but the need for more space led Blair to arrange the construction of a permanent laboratory building in 1934. When construction finished in 1935, the facility was initially called the Fort Monmouth Signal Laboratory until the War Department designated the building as the Squier Signal Laboratory in 1945 in honor of Major General George Owen Squier, founder of the SCL and Chief Signal Officer during World War I. The facility would later be redesignated as Squier Hall in 1955.

During 1934 and 1935, tests of microwave RPF equipment resulted in Doppler-shifted signals being obtained, initially at only a few hundred feet distance and later over several miles. These tests involved a bi-static arrangement, with the transmitter at one end of the line of transmission and the receiver at the other, and the reflecting target passing through or near the path. The development state of this Doppler-beat detector was summarized by Blair in 1935:
*To date the distances at which reflected signals can be detected with radio-optical equipment are not great enough to be of value. However, with improvements in the radiated power of the transmitter and sensitivity of the receiver, this method of position finding may well reach a state of usefulness.
In an internal report, Blair noted that the SCL might investigate another technique:
*Consideration is now being given to the scheme of projecting an interrupted sequence of trains of oscillations against the target and attempting to detect the echoes during the interstices between the projections.

Radio position finding

In 1936, a small project in pulsed microwave transmission was started by W. Delmar Hershberger. The SCL called this technique radio position-finding (RPF). Lacking success with microwaves, Hershberger visited the NRL (where he had earlier worked) and saw their 200-MHz pulsed set. Back at the SCL, he and Robert H. Noyes built an experimental set with a 110-MHz (2.73-m) pulsed transmitter and a receiver patterned on the one at the NRL. A request for project funding was turned down by the War Department, but, with the backing of the Chief Signal Officer, Maj. Gen. James B. Allison, $75,000 for support was diverted from a previous appropriation for a communication project.

In October 1936, Paul E. Watson (later Lt. Colonel) became the SCL Chief Engineer and led the project. A field setup near the coast was made with the transmitter and receiver separated by a mile. On December 14, the experimental set detected at up to range aircraft flying in and out of New York City.

Development of a prototype system followed, with Captain Rex Corput as the Project Officer. Ralph I. Cole headed receiver work and William S. Marks led transmitter improvements. Separate antennas and receivers were used for azimuth and elevation measurements. These receiving antennas, plus the transmitting antenna, were made of large arrays of dipole wires on wooden frames. The system output was used to aim a searchlight.

The first demonstration of the full set was made on the night of May 26, 1937. An unlighted bomber was detected and then illuminated by the searchlight. The observers included the Secretary of War, Henry A. Woodring; he was so impressed that the next day orders were given for the full development of the system.

With strong support from General Allison, a special Congressional appropriation of $250,000 was obtained. The frequency was increased to 200 MHz (1.5 m). The transmitter used 16 tubes in a ring oscillator circuit (developed at the NRL), producing about 75-kW peak power. Colton wanted lobe switching for the receiving antennas, and Major James C. Moore was assigned to head the resulting complex electrical and mechanical design. Engineers from Western Electric and Westinghouse were brought in to assist in the overall development.

First fielded Army systems

For better security and more space, the RPF activities were moved to Fort Hancock, New Jersey. This was an isolated location on Sandy Hook, a sandbar peninsula reaching into the New York Harbor. During 1938, Blair's health failed, and the position of SCL Director was taken over by Roger Colton, who was then promoted to Colonel. (After succeeding Blair as the Director of the SCL, Colton remained until September 1944, when he transferred to the Army Air Forces. He was awarded the Legion of Merit and the Distinguished Service Medal for his work at the SCL.)

Colton arranged for the demonstration of a prototype system in late November 1938. The system was designated SCR-268, with SCR meaning either Set Complete Radio or Signal Corps Radio used interchangeably in documents. The SCR-268 was primarily intended for aiming searchlights associated with anti-aircraft guns; the system allowed coarse pointing of a thermal infrared detector, and this then aimed the searchlight. The night demonstration was for the Coast Artillery Board and was conducted at Fort Monroe, just off the coast near Hampton, Virginia.

This was almost a failure because the target, a Martin B-10 bomber at altitude, was blown off course and flew miles out over the Atlantic. After a long return flight, it came above an opening in the clouds and, to the delight of the observers, was immediately illuminated by the radar-directed searchlight.

Production of SCR-268 sets was started by Western Electric in 1939, and it entered service in early 1941; about 3,100 sets were eventually built. Later, the plan position indicator (PPI) was added and the system was designated SCR-516, a low-altitude early-warning radar.

Another observer at the May 1937 test was Brig. Gen. Henry H. Arnold, then Assistant Chief of Staff of the Army Air Corps. This led to a request from the Air Corps for a simpler, longer-range, early-warning system. In parallel with the completion of the SCR-268, a new project led by Major, later Lieutenant Colonel, (Dr.) Harold A. Zahl got underway. Good funding and a high priority were received; thus, development was quickly completed.

This new system operated at 106 MHz (2.83 m) and had simplifications of the antenna, elimination of lobe-switching, and the addition of a duplexer developed by Zahl. Overall, there was a sacrifice in accuracy, but thus was balanced by ease in maintenance and greater range (up to 240 miles).

There were two configurations – the SCR-270 (mobile) and the SCR-271 (fixed-site). Westinghouse received the production contract, and started deliveries near the end of 1940. An SCR-270 was in service near the island of Oahu on the morning of December 7, 1941. At 7:20, the operators reported detecting a flight of planes due north, but the Duty Officer dismissed it as "nothing unusual" and the alarm went unheeded. At 7:59, the Japanese hit Pearl Harbor.

Taking over an earlier project of the NRL, the Laboratory developed the SCR-518 radar altimeter for the Army Air Forces. Operating at 518 MHz (0.579 m), this system was produced by RCA starting in 1940. The final system weighed less than 30 pounds and was accurate to about above ground. The Laboratory was also involved in an early version of a portable, radar-based instrument landing system, eventually designated the SCS-51.

Creation of field laboratories

During 1940 and 1941, the Signal Corps established three field laboratories near Fort Monmouth to supplement the expanding research efforts of the SCL.

Field Laboratory Number One, which became known as Camp Coles in 1942, was situated west of Red Bank, New Jersey and was tasked with the development of radio equipment. The 46-acre site was named in honor of Colonel Ray Howard Coles, assistant to the Chief Signal Officer during World War I. Camp Coles was redesignated as Coles Signal Laboratory in 1945 and then as Coles Area in 1956. Field Laboratory Number Two, later designated as the Eatontown Signal Laboratory due to its proximity to Eatontown

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases