Signal Corps Laboratories
Encyclopedia
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.
. 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 tube
s 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 WWI, aviation communication was transferred to the Signal Corps Aircraft Radio Laboratory at 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
.
started in 1930, decline in economic conditions forced the consolidation of the Signal Corps’ widespread laboratories. The Electrical and Meteorological Laboratories and the Signal Corps Laboratory at the National Bureau of Standards, both previously in Washington, D.C., were moved to Fort Monmouth. The Subaqueous (Sediment) Sound Ranging Laboratory was transferred there from Fort H. G. Wright, New York. The Aircraft Radio Laboratory, however, remained at Wright Field.
On June 30, 1930, the consolidated operations at Fort Monmouth became the Signal Corps Laboratories (SCL). The initial 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 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.
. Neither of these devices produced sufficient power for use in detection systems..
To house the activities of the SCl, Squier Hall was constructed in 1935. The facility was named to honor Dr. George O. Squier, founder of the SCL and Chief Signal Officer during WWI. Lt. Colonel Roger B. Colton was assigned as the SCL Executive Officer.
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::
In an internal report, Blair noted that the SCL might investigate another technique:
, 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 7 miles (11.3 km) 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.
. 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 20000 feet (6,096 m) 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 42000 feet (12,801.6 m) above ground. The Laboratory was also involved in an early version of a portable, radar-based instrument landing system
, eventually designated the SCS-51.
, a site a few miles south of Fort Monmouth. Here it was called the Camp Evans Signal Laboratory, with Lt. Col. Paul E. Watson the Director. This site included the original facility of the Marconi Belmont Station, and a central building commonly called the Marconi Hotel became the headquarters. Outdoor testing of hardware was often done at Twin Lights, a lighthouse station between Camp Evans and Fort Hancock
, New Jersey.
In mid-1940, the British and American governments made the decision to exchange information on their defense technologies and enter into shared developments. The Tizard Mission
initiated this exchange, bringing to America their most secret items. Among these was the cavity magnetron
. This high-power generator of microwave signals was immediately seen as the solution to further developments in radar. Before the end of the year, the Radiation Laboratory
(commonly called the Rad Lab) was established in facilities at MIT with the primary purpose of consolidating development of microwave radar.
The name radar came from the acronym RADAR, coined by the U.S. Navy in 1940 as a cover for their secret activities in Radio Detection And Ranging. The name was soon adopted by the U.S. Army, replacing Radio Position Finding (RPF), and by the British, replacing Radio Detection and Finding (RDF).
One of the first projects at the Rad Lab was the development of a mobile microwave gun- laying (aiming) radar for use with anti-aircraft (AA) guns. In May 1941, the preliminary system was completed and a demonstration was given to now Brig. General Roger B. Colton, Chief of Research and Engineering at the SCL. He promised Army support for the final development and recommended procuring a set for every AA battery.
In close cooperation with the SCL, representing the eventual user of the system, the Rad Lab developed an engineering model of the GL system. Designated XT-1, this was carried in four trucks, including a large power generator. To provide automatic target tracking, the Bell Telephone Laboratories (BTL) developed an electronic analog computer containing 160 vacuum tubes. Called the M-9 Predictor-Corrector Unit, this computer the system could automatically track targets to 18 miles (29 km) and direct four anti-aircraft guns.
Preliminary testing of the full GL system, now designated the SCR-584, was conducted by the SCL at Fort Monmouth in December 1941. It was eventually placed into production by General Electric
and Westinghouse
as prime contractors. About 1,500 of these systems were used in both the European and Pacific war theaters. The SCR-584 is largely credited with enabling anti-aircraft guns to destroy most of German V-1 flying bomb
s attacking London following the Normandy invasion.
Following the surprise bombing of Pearl Harbor, there was a crash program to obtain radars to protect the Panama Canal Zone
from a similar attack. To detect low-flying aircraft at a range allowing sufficient warning, a high-frequency system for radar picket
ships 100 miles (160.9 km) offshore was needed. Captain John W. Marchetti
led a 20-person team in using the VT-158 to adapt SCR-268s for this application. The special project was completed in a few weeks.
Marchetti’s team then went on to convert this into the AN/TPS-3, a light-weight, transportable system and the last major radar fully developed by the SCL. The set could be assembled and placed into operation by a small crew in 30 minutes. During the war, the AN/TPS-3 was used for early warning at beachheads, isolated areas, and captured air bases. A version, AN/TQS-3, was developed for locating motars. Zenith manufactured about 900 total of both versions. After the war, Marchetti became the first director of the Air Force Cambridge Research Center in Massachusetts.
In March 1942, the U.S. Army was reorganized into three components: Ground Forces, Air Forces, and Service Forces. The Signal Corps was in the Service Forces. At this time, the SCL officially became the Signal Corps General Services. The operations remained at Camp Evans, and, for most purposes, continued to be referred to as the SCL or the Camp Evans Signals Laboratory. During the war years, the overall operations of the Signal Corps at Fort Monmouth about 14,000 personnel.
Most of the radar projects at the SCL were in association with the Rad Lab, primarily in transferring prototypes from the research state to rugged hardware for field use. Essentially all manufacturing was performed by commercial firms. A few of the many such systems will be noted.
The SCR-582 was an early 10-cm radar developed for the SCL by the Rad Lab. Primarily intended as a harbor-defense system, it had a 48-inch parabolic dish and was usually mounted atop a 100 feet (30.5 m) tower. With a PPI display, it was ideally suited for guiding ships entering harbors and could also detect low-flying aircraft at 25 miles (40.2 km). The SCR-682 was a transportable version.
The SCL was responsible for a number of other 10-cm radars used by the Army. Some of their air-transportable radars included the AN/CPS-1, an early-warning set built by General Electric with a range up to 200 miles (321.9 km). The AN/CPS-4, nicknamed “Beaver Tail” from the shape of its beam, was a height finder
set from the Rad Lab; it was used with the SCR-270 and SCR-271. The BTL developed the AN/CPS-5, a ground-controlled interception
radar that could track targets at more than 200 miles (321.9 km) distance.
Representative SCL mobile-ground radars included the AN/GPN-2, a search set with a 60 miles (96.6 km) range produced by Bendix Corporation
, and the AN/GPN-6, a similar search set from the Laboratory for Electronics Inc. The AN/CPN-18, also made by Bendix, was the secondary surveillance radar
portion of an air-traffic control system used by the Army Air Forces.
In February 1945, the Army Air Forces took over a portion of the operations; this was designated the Watson Laboratories, named in honor of Lt. Colonel Paul E. Watson
. This was later transferred to Griffiss AFB and became the Rome Air Development Center.
The United States conducted Project Paperclip, under which a number of German scientists and engineers were brought to America to work in defense research. Twenty-four of these specialists were hired by the ESL where they made significant contributions to future radars and other electronics developments.
In late 1945, Project Diana
was started at the ESL. Using a modified SCR-271 radar with a special antenna, attempts were made receive a signal bounced off of the Moon. On January 10, 1946, this was successful, with the reflected signal received 2.5 seconds after it was transmitted. This demonstrated the potential of radio communications beyond the Earth for space probes and human explorers.
In 1946, the ESL developed the MPQ-10, an automatic counter-battery radar
. Two years later, this was followed by the Army’s first weather radar
. A large laboratory complex, informally called the Hexagon, was built in 1954 for the ESL operations. This was later named the Myer Center, a memorial to Albert James Meyr, founder of the Army Signal Corps.
As of August 1, 1962, Fort Monmouth was no longer a Signal Corps installation. Under the Army Materiel Command
, this became the home of the U.S. Army Electronics Command (ECOM), later the U.S. Army Electronics and Communications Command (ECCOM). After 80 years as the center of the Army's communications and electronics development, the 2005 DoD Base Realignment and Closure (BRAC) directed that these activities be transferred elsewhere and Fort Monmouth be closed by 2011.
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 JerseyNew Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
. This facility was named after Alfred Vail, an inventor associated with Samuel F. B. Morse
Samuel F. B. Morse
Samuel Finley Breese Morse was an American contributor to the invention of a single-wire telegraph system based on European telegraphs, co-inventor of the Morse code, and an accomplished painter.-Birth and education:...
. 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 tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s 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
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
. Squier had earlier made a major contribution to communications by developing multiplexing
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
, for which he was elected to the National Academy of Sciences
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...
in 1919.
After the end of WWI, aviation communication was transferred to the Signal Corps Aircraft Radio Laboratory at Wright Field
Wright Field
Wright Field was an airfield of the United States Army Air Corps and Air Forces near Riverside, Ohio. From 1927 to 1947 it was the research and development center for the Air Corps, and during World War II a flight test center....
in Dayton, Ohio
Dayton, Ohio
Dayton is the 6th largest city in the U.S. state of Ohio and the county seat of Montgomery County, the fifth most populous county in the state. The population was 141,527 at the 2010 census. The Dayton Metropolitan Statistical Area had a population of 841,502 in the 2010 census...
. 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
Fort Monmouth
Fort Monmouth was an installation of the Department of the Army in Monmouth County, New Jersey. The post is surrounded by the communities of Eatontown, Tinton Falls and Oceanport, New Jersey, and is located about 5 miles from the Atlantic Ocean. The post covers nearly of land, from the Shrewsbury...
. 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
Weather balloon
A weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde...
.
Formation of the SCL
As the Great DepressionGreat Depression
The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...
started in 1930, decline in economic conditions forced the consolidation of the Signal Corps’ widespread laboratories. The Electrical and Meteorological Laboratories and the Signal Corps Laboratory at the National Bureau of Standards, both previously in Washington, D.C., were moved to Fort Monmouth. The Subaqueous (Sediment) Sound Ranging Laboratory was transferred there from Fort H. G. Wright, New York. The Aircraft Radio Laboratory, however, remained at Wright Field.
On June 30, 1930, the consolidated operations at Fort Monmouth became the Signal Corps Laboratories (SCL). The initial SCL had a personnel strength of 5 officers, 12 enlisted men, and 53 civilians. Major (Dr.) William R. Blair
William R. Blair
William Richards Blair was an American scientist and Army Officer who led the U.S. Signal Corps Laboratories during its formative years. He is often called the "Father of Army Radar."-Career and achievements:...
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
Frankford Arsenal
The Frankford Arsenal was a United States Army ammunition plant located adjacent to the Bridesburg neighborhood of Northeast Philadelphia, Pennsylvania, north of the original course of Frankford Creek.-History:...
had made tests in detecting infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
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
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
) 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
Blimp
A blimp, or non-rigid airship, is a floating airship without an internal supporting framework or keel. A non-rigid airship differs from a semi-rigid airship and a rigid airship in that it does not have any rigid structure, neither a complete framework nor a partial keel, to help the airbag...
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 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 RCARCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
. Neither of these devices produced sufficient power for use in detection systems..
To house the activities of the SCl, Squier Hall was constructed in 1935. The facility was named to honor Dr. George O. Squier, founder of the SCL and Chief Signal Officer during WWI. Lt. Colonel Roger B. Colton was assigned as the SCL Executive Officer.
During 1934 and 1935, tests of microwave RPF equipment resulted in Doppler
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
-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 DepartmentUnited States Department of War
The United States Department of War, also called the War Department , was the United States Cabinet department originally responsible for the operation and maintenance of the United States Army...
, 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
Paul E. Watson
Paul E. Watson was a pioneer researcher in the development of radar. Born in Bangor, Maine, Watson was a civilian engineer employed by the U.S. Army Signal Corps from the late 1920s. In 1936, he was named Chief Engineer of a Signal Corps research group at Camp Evans in Fort Monmouth, New Jersey...
(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 7 miles (11.3 km) 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
Elevation
The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....
measurements. These receiving antennas, plus the transmitting antenna, were made of large arrays of dipole
Dipole
In physics, there are several kinds of dipoles:*An electric dipole is a separation of positive and negative charges. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some distance. A permanent electric dipole is called an electret.*A...
wires on wooden frames. The system output was used to aim a searchlight
Searchlight
A searchlight is an apparatus that combines a bright light source with some form of curved reflector or other optics to project a powerful beam of light of approximately parallel rays in a particular direction, usually constructed so that it can be swiveled about.-Military use:The Royal Navy used...
.
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
Ring oscillator
A ring oscillator is a device composed of an odd number of NOT gates whose output oscillates between two voltage levels, representing true and false...
circuit (developed at the NRL), producing about 75-kW peak power. Colton wanted lobe switching
Lobe switching
Lobe switching is a method used on early radar sets to improve tracking accuracy. It used two slightly separated antenna elements to send the beam slightly to either side of the midline of the antenna, switching between the two to find which one gave the stronger return, thereby indicating which...
for the receiving antennas, and Major James C. Moore was assigned to head the resulting complex electrical and mechanical design. Engineers from Western Electric
Western Electric
Western Electric Company was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. It was the scene of a number of technological innovations and also some seminal developments in industrial management...
and Westinghouse
Westinghouse Electric (1886)
Westinghouse Electric was an American manufacturing company. It was founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The company purchased CBS in 1995 and became CBS Corporation in 1997...
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 JerseyFort Hancock, New Jersey
Fort Hancock is a former United States Army fort at Sandy Hook, located in Middletown Township in Monmouth County, along the Atlantic coast of eastern New Jersey in the United States. This coastal artillery base played an important part in the defense of New York Harbor and played a role in the...
. This was an isolated location on Sandy Hook
Sandy Hook
Sandy Hook is a barrier spit along the Atlantic coast of New JerseySandy Hook may also refer to:-Places:United States* Sandy Hook , a village in the town of Newtown, Connecticut* Sandy Hook, Kentucky, a city in Elliott County...
, a sandbar peninsula reaching into the New York Harbor
New York Harbor
New York Harbor refers to the waterways of the estuary near the mouth of the Hudson River that empty into New York Bay. It is one of the largest natural harbors in the world. Although the U.S. Board of Geographic Names does not use the term, New York Harbor has important historical, governmental,...
. 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
Legion of Merit
The Legion of Merit is a military decoration of the United States armed forces that is awarded for exceptionally meritorious conduct in the performance of outstanding services and achievements...
and the Distinguished Service Medal
Distinguished Service Medal (United States)
The Distinguished Service Medal is the highest non-valorous military and civilian decoration of the United States military which is issued for exceptionally meritorious service to the government of the United States in either a senior government service position or as a senior officer of the United...
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
SCR
SCR may refer to:In business:* Solvency Capital Requirement Solvency II.In associations, companies, institutions:* Smyrna Cassaba Railway an Ottoman railway* Senior Common Room of a higher education institution* South Central Railway in India...
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
Infrared detector
An infrared detector is a photodetector that reacts to infrared radiation. The two main types of detectors are thermal and photonic.The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena....
, and this then aimed the searchlight. The night demonstration was for the Coast Artillery Board and was conducted at Fort Monroe
Fort Monroe
Fort Monroe was a military installation in Hampton, Virginia—at Old Point Comfort, the southern tip of the Virginia Peninsula...
, just off the coast near Hampton, Virginia
Hampton, Virginia
Hampton is an independent city that is not part of any county in Southeast Virginia. Its population is 137,436. As one of the seven major cities that compose the Hampton Roads metropolitan area, it is on the southeastern end of the Virginia Peninsula. Located on the Hampton Roads Beltway, it hosts...
.
This was almost a failure because the target, a Martin B-10
Martin B-10
The Martin B-10 was the first all-metal monoplane bomber to go into regular use by the United States Army Air Corps, entering service in June 1934...
bomber at 20000 feet (6,096 m) 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
Western Electric
Western Electric Company was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. It was the scene of a number of technological innovations and also some seminal developments in industrial management...
in 1939, and it entered service in early 1941; about 3,100 sets were eventually built. Later, the plan position indicator
Plan position indicator
The plan position indicator , is the most common type of radar display. The radar antenna is usually represented in the center of the display, so the distance from it and height above ground can be drawn as concentric circles...
(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
Henry H. Arnold
Henry Harley "Hap" Arnold was an American general officer holding the grades of General of the Army and later General of the Air Force. Arnold was an aviation pioneer, Chief of the Air Corps , Commanding General of the U.S...
, then Assistant Chief of Staff of the Army Air Corps
United States Army Air Corps
The United States Army Air Corps was a forerunner of the United States Air Force. Renamed from the Air Service on 2 July 1926, it was part of the United States Army and the predecessor of the United States Army Air Forces , established in 1941...
. 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
Harold A. Zahl
Harold A. Zahl was an American physicist who had a 35-year career with the U.S. Army Signal Corps Laboratories, making major contributions to radar development.-Career and accomplishments:...
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
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
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
Pearl Harbor
Pearl Harbor, known to Hawaiians as Puuloa, is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. Much of the harbor and surrounding lands is a United States Navy deep-water naval base. It is also the headquarters of the U.S. Pacific Fleet...
.
Taking over an earlier project of the NRL, the Laboratory developed the SCR-518 radar altimeter
Radar altimeter
A radar altimeter, radio altimeter, low range radio altimeter or simply RA measures altitude above the terrain presently beneath an aircraft or spacecraft...
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 42000 feet (12,801.6 m) above ground. The Laboratory was also involved in an early version of a portable, radar-based instrument landing system
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...
, eventually designated the SCS-51.
Evans Signal Laboratory
During 1941, the SCL again relocated, this time to Camp EvansCamp Evans
Camp Evans, New Jersey is a former military base associated with Fort Monmouth. It is located in Wall Township, although it is often said to be located in Belmar . The property overlooks the Shark River.Camp Evans is named after Lt. Col...
, a site a few miles south of Fort Monmouth. Here it was called the Camp Evans Signal Laboratory, with Lt. Col. Paul E. Watson the Director. This site included the original facility of the Marconi Belmont Station, and a central building commonly called the Marconi Hotel became the headquarters. Outdoor testing of hardware was often done at Twin Lights, a lighthouse station between Camp Evans and Fort Hancock
Fort Hancock
Fort Hancock may refer to:* Fort Hancock, Texas, a census-designated place in Hudspeth County, Texas* Fort Hancock, New Jersey, a fort on the Sandy Hook beach of New Jersey* Fort Hancock, U.S. Life Saving Station, located in Highlands, New Jersey...
, New Jersey.
In mid-1940, the British and American governments made the decision to exchange information on their defense technologies and enter into shared developments. The Tizard Mission
Tizard Mission
The Tizard Mission officially the British Technical and Scientific Mission was a British delegation that visited the United States during the Second World War in order to obtain the industrial resources to exploit the military potential of the research and development work completed by the UK up...
initiated this exchange, bringing to America their most secret items. Among these was the cavity magnetron
Cavity magnetron
The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field. The 'resonant' cavity magnetron variant of the earlier magnetron tube was invented by John Randall and Harry Boot in 1940 at the University of...
. This high-power generator of microwave signals was immediately seen as the solution to further developments in radar. Before the end of the year, the Radiation Laboratory
Radiation Laboratory
The Radiation Laboratory, commonly called the Rad Lab, was located at the Massachusetts Institute of Technology in Cambridge, Massachusetts and functioned from October 1940 until December 31, 1945...
(commonly called the Rad Lab) was established in facilities at MIT with the primary purpose of consolidating development of microwave radar.
The name radar came from the acronym RADAR, coined by the U.S. Navy in 1940 as a cover for their secret activities in Radio Detection And Ranging. The name was soon adopted by the U.S. Army, replacing Radio Position Finding (RPF), and by the British, replacing Radio Detection and Finding (RDF).
One of the first projects at the Rad Lab was the development of a mobile microwave gun- laying (aiming) radar for use with anti-aircraft (AA) guns. In May 1941, the preliminary system was completed and a demonstration was given to now Brig. General Roger B. Colton, Chief of Research and Engineering at the SCL. He promised Army support for the final development and recommended procuring a set for every AA battery.
In close cooperation with the SCL, representing the eventual user of the system, the Rad Lab developed an engineering model of the GL system. Designated XT-1, this was carried in four trucks, including a large power generator. To provide automatic target tracking, the Bell Telephone Laboratories (BTL) developed an electronic analog computer containing 160 vacuum tubes. Called the M-9 Predictor-Corrector Unit, this computer the system could automatically track targets to 18 miles (29 km) and direct four anti-aircraft guns.
Preliminary testing of the full GL system, now designated the SCR-584, was conducted by the SCL at Fort Monmouth in December 1941. It was eventually placed into production by General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
and Westinghouse
Westinghouse Electric (1886)
Westinghouse Electric was an American manufacturing company. It was founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The company purchased CBS in 1995 and became CBS Corporation in 1997...
as prime contractors. About 1,500 of these systems were used in both the European and Pacific war theaters. The SCR-584 is largely credited with enabling anti-aircraft guns to destroy most of German V-1 flying bomb
V-1 flying bomb
The V-1 flying bomb, also known as the Buzz Bomb or Doodlebug, was an early pulse-jet-powered predecessor of the cruise missile....
s attacking London following the Normandy invasion.
Wartime Radars
Although the SCL initiated its radar research using microwaves, it never returned to developing sets in this wavelength region. The Evans Signal Laboratory did, however, push the frequencies higher, primarily through Harold Zahl's development in 1939 of the VT-158, a tube generating 240-kW pulse-power at up to 600 MHz (0.5 m). This was actually four triodes and their associated circuit tightly packaged in one glass envelope.Following the surprise bombing of Pearl Harbor, there was a crash program to obtain radars to protect the Panama Canal Zone
Panama Canal Zone
The Panama Canal Zone was a unorganized U.S. territory located within the Republic of Panama, consisting of the Panama Canal and an area generally extending 5 miles on each side of the centerline, but excluding Panama City and Colón, which otherwise would have been partly within the limits of...
from a similar attack. To detect low-flying aircraft at a range allowing sufficient warning, a high-frequency system for radar picket
Radar picket
A radar picket is a radar-equipped ship, submarine, aircraft, or vehicle used to increase the radar detection range around a force to protect it from surprise attack. Often several detached radar units encircle a force to provide increased cover in all directions.-World War II:Radar picket ships...
ships 100 miles (160.9 km) offshore was needed. Captain John W. Marchetti
John W. Marchetti
John William Marchetti was a radar pioneer who had an outstanding career combining government and industrial activities. He was born of immigrant parents in Boston, Massachusetts, and entered Columbia College and Columbia School of Engineering and Applied Science in 1925...
led a 20-person team in using the VT-158 to adapt SCR-268s for this application. The special project was completed in a few weeks.
Marchetti’s team then went on to convert this into the AN/TPS-3, a light-weight, transportable system and the last major radar fully developed by the SCL. The set could be assembled and placed into operation by a small crew in 30 minutes. During the war, the AN/TPS-3 was used for early warning at beachheads, isolated areas, and captured air bases. A version, AN/TQS-3, was developed for locating motars. Zenith manufactured about 900 total of both versions. After the war, Marchetti became the first director of the Air Force Cambridge Research Center in Massachusetts.
In March 1942, the U.S. Army was reorganized into three components: Ground Forces, Air Forces, and Service Forces. The Signal Corps was in the Service Forces. At this time, the SCL officially became the Signal Corps General Services. The operations remained at Camp Evans, and, for most purposes, continued to be referred to as the SCL or the Camp Evans Signals Laboratory. During the war years, the overall operations of the Signal Corps at Fort Monmouth about 14,000 personnel.
Most of the radar projects at the SCL were in association with the Rad Lab, primarily in transferring prototypes from the research state to rugged hardware for field use. Essentially all manufacturing was performed by commercial firms. A few of the many such systems will be noted.
The SCR-582 was an early 10-cm radar developed for the SCL by the Rad Lab. Primarily intended as a harbor-defense system, it had a 48-inch parabolic dish and was usually mounted atop a 100 feet (30.5 m) tower. With a PPI display, it was ideally suited for guiding ships entering harbors and could also detect low-flying aircraft at 25 miles (40.2 km). The SCR-682 was a transportable version.
The SCL was responsible for a number of other 10-cm radars used by the Army. Some of their air-transportable radars included the AN/CPS-1, an early-warning set built by General Electric with a range up to 200 miles (321.9 km). The AN/CPS-4, nicknamed “Beaver Tail” from the shape of its beam, was a height finder
Height finder
A height finder is a ground based aircraft altitude measuring device.Early height finder implementations were optical devices and later migrated to radar devices. Devices combining both optics and radar were deployed by the U.S...
set from the Rad Lab; it was used with the SCR-270 and SCR-271. The BTL developed the AN/CPS-5, a ground-controlled interception
Ground-controlled interception
Ground-controlled interception an air defense tactic whereby one or more radar stations are linked to a command communications centre which guides interceptor aircraft to an airborne target. This tactic was pioneered during World War II by the Royal Air Force with the Luftwaffe to follow closely...
radar that could track targets at more than 200 miles (321.9 km) distance.
Representative SCL mobile-ground radars included the AN/GPN-2, a search set with a 60 miles (96.6 km) range produced by Bendix Corporation
Bendix Corporation
The Bendix Corporation was an American manufacturing and engineering company which during various times in its 60 year existence made brake systems, aeronautical hydraulics, avionics, aircraft and automobile fuel control systems, radios, televisions and computers, and which licensed its name for...
, and the AN/GPN-6, a similar search set from the Laboratory for Electronics Inc. The AN/CPN-18, also made by Bendix, was the secondary surveillance radar
Secondary surveillance radar
Secondary surveillance radar is a radar system used in air traffic control , that not only detects and measures the position of aircraft i.e. range and bearing, but also requests additional information from the aircraft itself such as its identity and altitude...
portion of an air-traffic control system used by the Army Air Forces.
In February 1945, the Army Air Forces took over a portion of the operations; this was designated the Watson Laboratories, named in honor of Lt. Colonel Paul E. Watson
Paul E. Watson
Paul E. Watson was a pioneer researcher in the development of radar. Born in Bangor, Maine, Watson was a civilian engineer employed by the U.S. Army Signal Corps from the late 1920s. In 1936, he was named Chief Engineer of a Signal Corps research group at Camp Evans in Fort Monmouth, New Jersey...
. This was later transferred to Griffiss AFB and became the Rome Air Development Center.
Closure
At the end of the war in 1945, the laboratories were again reorganized, officially forming the Signal Corps Engineering Laboratory (SCEL). While for most purposes this continued to be called the Evans Signal Laboratory (ESL), there was little or no further reference to the Signal Corps Laboratories. Some of the subsequent activities will be noted.The United States conducted Project Paperclip, under which a number of German scientists and engineers were brought to America to work in defense research. Twenty-four of these specialists were hired by the ESL where they made significant contributions to future radars and other electronics developments.
In late 1945, Project Diana
Project Diana
Project Diana, named for the Roman moon goddess Diana — goddess of the hunt, wild animals and the moon — was a project of the US Army Signal Corps to bounce radio signals off the moon and receive the reflected signals...
was started at the ESL. Using a modified SCR-271 radar with a special antenna, attempts were made receive a signal bounced off of the Moon. On January 10, 1946, this was successful, with the reflected signal received 2.5 seconds after it was transmitted. This demonstrated the potential of radio communications beyond the Earth for space probes and human explorers.
In 1946, the ESL developed the MPQ-10, an automatic counter-battery radar
Counter-battery radar
A counter-battery radar detects artillery projectiles fired by one or more guns, howitzers, mortars and rocket launchers and from their trajectories locates the position on the ground of the gun, etc., that fired it. Alternatively, or in addition, it may determine where the projectile will land...
. Two years later, this was followed by the Army’s first weather radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
. A large laboratory complex, informally called the Hexagon, was built in 1954 for the ESL operations. This was later named the Myer Center, a memorial to Albert James Meyr, founder of the Army Signal Corps.
As of August 1, 1962, Fort Monmouth was no longer a Signal Corps installation. Under the Army Materiel Command
Army Materiel Command
Army Materiel Command can refer to:*United States Army Materiel Command*Army Materiel Command...
, this became the home of the U.S. Army Electronics Command (ECOM), later the U.S. Army Electronics and Communications Command (ECCOM). After 80 years as the center of the Army's communications and electronics development, the 2005 DoD Base Realignment and Closure (BRAC) directed that these activities be transferred elsewhere and Fort Monmouth be closed by 2011.
General references
- Brown, Louis; A Radar History of World War II - Technical and Military Imperatives, Inst. of Physics Pub., 1999
- Skolnik, Merrill I.; “Fifty Years of Radar,” Proc IEEE, Special Issue on Radar, Vol. 73, p. 182, 1985
- Terrett, Dulany; The Signal Corps: The Emergency (to December 1941), 4th ed., Government Printing Office, 2002
- Vieweger A. L.; “Radar in the Signal Corps,” IRE Trans Mil. Elect., MIL-4, p. 555, Oct. 1960
- Watson, Raymond C., Jr.; Radar Origins Worldwide, Trafford Publications, 2009
- Zale, Harold; Electronics Away, 1969, and Radar Spelled Backwards, 1972, Vantage Press
External links
- Staff of the CECOM LCMC Historical Office; "A Concise History of Fort Monmouth, New Jersey, and the U. S. Army CECOM Life Cycle Management Command," 2009; http://cecom.army.mil/historian/pubupdates/FM%20History%20Book%2009_4Web.pdf
- Goebel, Gregory V.; “The Wizard War: WW2 & The Origins of Radar,” a book-length document; http://www.vectorsite.net/ttwiz.html
- “Radar: A Report on Science at War,” Office of Scientific Research and Development, distributed by Office of War Information, 15 Aug. 1945; http://www.ibiblio.org/hyperwar/USN/ref/Radar-OSRD/index.html