SCR-270 radar - AbsoluteAstronomy.com

The SCR-270 was one of the first operational early warning radar

Early warning radar

An early warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate...

s. It was the U.S. Army's primary long-distance radar throughout World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

and was deployed around the world. It is also known as the Pearl Harbor Radar, since it was a SCR-270 set that detected the incoming raid about half an hour before the attack commenced.

Two versions were produced, the mobile SCR-270, and the fixed SCR-271 which used the same electronics but used an antenna with somewhat greater resolution. An upgraded version, the SCR-289, was also produced, but saw little use. All of the -270 versions were later replaced by newer 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...

units after 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...

was introduced to the US during 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...

. The only early warning system of the sort to see action was the AN/CPS-1, which was available in late 1944.

Building of the radar

The Signal Corps had been experimenting with some radar concepts as early at the late 1920s, under the direction of Colonel William R. Blair, director of the Signal Corps Laboratories at 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...

, New Jersey

New 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...

. Although the Army focused primarily on infra-red detection systems (a popular idea at the time), in 1935 work turned to radar again when one of Blair's recent arrivals, Roger B. Colton, convinced him to send another engineer to investigate the US Navy's CXAM radar

CXAM radar

The CXAM radar system was the first production radar system deployed on United States Navy ships. It followed several earlier prototype systems, such as the NRL radar installed in April 1937 on the destroyer ; its successor, the XAF, installed in December 1938 on the battleship ; and the first...

project. William D. Hershberger went to see what they had, and returned a positive report. Gaining the support of James B. Allison, the Chief Signal Officer, they managed to gather a small amount of funding and diverted some from other projects. A research team was organized under the direction of civilian engineer 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...

.

By December 1936 Watson's group had a working prototype, which they continued to improve. By May 1937 they were able to demonstrate the set, detecting a bomber at night. This demonstration turned out to be particularly convincing by mistake; the 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 had originally been instructed to fly to a known point for the radar to find it, but could not be located at the agreed upon time. The radar operators then searched for the bomber and located it about ten miles (16 km) from its intended position. It was later learned that winds had blown the bomber off course, so what was to be a simple demonstration turned into an example of real-world radar location and tracking. Development of this system continued as the SCR-268

SCR-268 radar

The SCR-268 was the US Army's first radar system. It was developed to provide accurate aiming information and used in gun laying systems and directing searchlights against aircraft....

, which eventually evolved into an excellent short-to-medium range gun laying

Gun laying

Gun laying is the process of aiming an artillery piece, such as a gun, howitzer or mortar on land or at sea against surface or air targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights...

system.

In April of 1937 a LtC. Davis, an officer in an 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...

Pursuit Squadron in 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...

(CZ), sent a request for a "Means of Radio Detection of Aircraft" to the US Army's Chief Signal Officer (CSig.), bypassing normal channels of command. The SCR-268 was not really suited to this need, and after its demonstration in May they again received a request for a long-range unit, this time from "Hap" 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...

who wrote to them June 3, 1937.

Shortly thereafter the Signal Corps became alarmed that their radar work was being observed by German spies, and moved development to Sandy Hook at 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...

, the coast artillery defense site for Lower New York Bay

Lower New York Bay

Lower New York Bay is that section of New York Bay south of the Narrows, the relatively narrow strait between the shores of Staten Island and Brooklyn. The southern end of the bay opens directly to the Atlantic Ocean between two spits of land, Sandy Hook, New Jersey, and Rockaway, Queens, on Long...

. After the move, work immediately started on the Air Corps request for what was to become known (in 1940) as the "Radio Set SCR-270". Parts of the SCR-268 were diverted to this new project, delaying the completion of the -268.

Key to the -270's operation was the primary water-cooled 8 kW continuous/100 kW pulsed transmitting tube. Early examples were hand-built, but a contract was let to Westinghouse in October 1938 to provide production versions under the Westinghouse designation "WL-530" and the Signal Corps type number "VT-122". A pair of these arrived in January 1939, and were incorporated into the first SCR-270 in time to be used in the Army's maneuvers that summer. Several improved components followed as the Army offered additional contracts for eventual production.

The original -270 consisted of a four-vehicle package including a K-30 operations van for the radio equipment and oscilloscope, a K-31 gasoline-fueled power-generating truck, a K-22B flatbed trailer, and a K-32 prime mover. The antenna folding mount was derived from a well-drilling derrick, and was mounted on the trailer for movement. When opened it was 55 feet (16.8 m) tall, mounted on an 8 feet (2.4 m) wide base containing motors for rotating the antenna. The antenna itself consisted of a series of 36 half wave 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...

s backed with reflectors, arranged in three bays, each bay with twelve dipoles arranged in a three-high four-wide stack. (Later production versions of the SCR-270 used 32 dipoles and reflectors, either eight wide by four high (fixed) or four wide by eight high (mobile)).

In use, the antenna was swung by command from the operations van, the angle being read by reading numbers painted on the antenna mount. The radar operated at 106 MHz, using a pulse width from 10 to 25 microseconds, and a pulse repetition frequency of 621 Hz. With a wavelength of about nine feet, the SRC-270 was comparable to the contemporary Chain Home

Chain Home

Chain Home was the codename for the ring of coastal Early Warning radar stations built by the British before and during the Second World War. The system otherwise known as AMES Type 1 consisted of radar fixed on top of a radio tower mast, called a 'station' to provide long-range detection of...

system being developed in England, but not to the more advanced microwave

Microwave

systems in Germany. This frequency did turn out to be useful, as it is roughly the size of an airplane's propeller, and provided strong returns from them depending on the angle. Generally it had an operational range of about 150 miles (241.4 km), and consistently picked up aircraft at that range. A nine-man field operating crew consisted of a shift chief, two oscilloscope operators, two plotters, two technicians, and two electricians.

The declassified US military document "U.S. Radar -- Operational Characteristics of Available Equipment Classified by Tactical Application" gives performance statistics for the SCR-270-D, namely "maximum range on a single bomber flying at indicated heights, when set is on a flat sea level site":

Maximum range at indicated height of aircraft
Altitude	1000 ft (304.8 m)	5000 ft (1,524 m)	20000 ft (6,096 m)	25000 ft (7,620 m)
Range	20 mi (32.2 km)	50 mi (80.5 km)	100 mi (160.9 km)	110 mi (177 km)

Deployment and Incomprehension

The non portable version, the SCR-271-A, s/n 1 was delivered to the Canal Zone and began operation in October of 1940 at Fort Sherman

Fort Sherman

Fort Sherman is a former United States Army base located on Toro Point at the Atlantic end of the Panama Canal, on the western bank of the Canal directly opposite Colón . It was the primary defensive base for the Atlantic sector of the Canal, and was also the center for US jungle warfare training...

on the Atlantic end of the Panama Canal

Panama Canal

The Panama Canal is a ship canal in Panama that joins the Atlantic Ocean and the Pacific Ocean and is a key conduit for international maritime trade. Built from 1904 to 1914, the canal has seen annual traffic rise from about 1,000 ships early on to 14,702 vessels measuring a total of 309.6...

. It picked up airliners at 117 miles (188.3 km) in its initial test run. The second set was set up on Fort Grant's Tobaga Island on the Pacific end of the Canal by December 1940, thus giving radar coverage to the vitally important but vulnerable Panama Canal. Westinghouse quickly ramped up production, and produced 100 by the end of 1941.

Operators of sets that were sent to the Panama canal, the Philippines, Hawaii and other strategic locations were all gathered for an air defense school at Mitchel Field, New York in April 1941. The school was the culmination of efforts began in 1940, when the War Department created the Air Defense Command headed by Brig. Gen. James E. Chaney. http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-5.html Chaney was tasked by Hap Arnold to collect all information on the British air defense system and transfer the knowledge as quickly as possible to the US military. Air Marshal Dowding

Hugh Dowding, 1st Baron Dowding

Air Chief Marshal Hugh Caswall Tremenheere Dowding, 1st Baron Dowding GCB, GCVO, CMG was a British officer in the Royal Air Force...

, one of the designers of the 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...

(GCI) air defense system used during the Battle of Britain

Battle of Britain

The Battle of Britain is the name given to the World War II air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940...

, was at the school and discussed with the American generals the design and urgency of establishing the Hawaiian system, in particular emphasizing the need for thorough radar site coverage along the coasts.https://www.airforcehistory.hq.af.mil/EARS/Hallionpapers/battleofbritainsep98.htm

Despite the high level attention and the excellence of the school in training on the use of the SCR-270 and its integration and coordination with fighter intercepts, the army did not follow through on supporting the junior officers who were trained at this session. Army Major Kenneth Bergquist returned to Hawaii after attending the school intending to set up a coordinated system, but when he arrived he found the local Army leadership was uninterested in the system, and he was reassigned to his former fighter unit. Only when incomprehensible equipment began appearing did the army return Bergquist from his fighter unit and was told his job was to assemble the equipment when it arrived. Assigned the defense of Hawaii, General Walter Short

Walter Short

Walter Campbell Short was a Major General in the United States Army and the U.S. military Commander responsible for the defense of U.S. military installations in Hawaii at the time of the Japanese attack on Pearl Harbor on December 7, 1941.-Early life:He was born in 1880 in Fillmore, Illinois...

had faint grasp of the weapons and tactics that Army technologists (led by Hap Arnold) were aggressively pushing them to adopt. Except in rare cases, there was little interest in assisting or even cooperating with the goal of setting up the air defense system. On his own initiative, Bergquist along with some other motivated junior officers built a makeshift control center without authorization and only by scrounging.

The first SR-270's became functional in July, 1941 and by November Bergquist only had a small team established and a set of four SCR-270-B's stationed around Oahu with one unit in reserve. They were placed on the central north shore (Haleiwa), Opana Point

Opana Radar Site

The Opana Radar Site is a National Historic Landmark and IEEE Milestone that commemorates the first operational use of radar by the United States in wartime, during the attack on Pearl Harbor. It is located off the Kamehameha Highway just inland from the north shore of Oahu, Hawaii, south of...

(northern tip), in the northwest at the highest point- Mount Kaala, and one in the southeast corner at Koko Head. However there was no real communications system or reporting chain set up. At one point the operators of one of the sets were instructed to phone in reports from a gas station some distance away. By explicit order by General Short, the radar stations were to only be operated for four hours per day and to shut down by 7AM each day.

Although communications were eventually improved, the chain of command was not. Air defense required direct control of assets spread out over disparate units; anti aircraft guns, radars, and interceptor aircraft were not under a unified command. This had been one of the primary problems identified by Robert Watson-Watt

Robert Watson-Watt

Sir Robert Alexander Watson-Watt, KCB, FRS, FRAeS is considered by many to be the "inventor of radar". Development of radar, initially nameless, was first started elsewhere but greatly expanded on 1 September 1936 when Watson-Watt became...

prior to the war, when a demonstration of an early radar system had gone comically wrong even though the radar system itself had worked perfectly. Dowding was well aware of the importance of a unified command, but this knowledge did not result in changes within the Army structure.

Use of SCR-270 radar at Pearl Harbor

Unit s/n 012 was at Opana Point

Opana Radar Site

, Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

on the morning of the seventh of December, 1941 manned by two privates, Elliot and Joseph Lockard. That morning the set was supposed to be shut down, but the soldiers decided to get in additional training time in since the truck scheduled to take them to breakfast was late. At 7:02 they detected the Japanese aircraft approaching 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...

at a distance of 130 miles (209.2 km) and Lockard telephoned the information center at Fort Shafter

Fort Shafter

Fort Shafter is in Honolulu CDP, City and County of Honolulu, Hawai‘i, extending up the interfluve between Kalihi and Moanalua valleys, as well as onto the coastal plain at Māpunapuna. Fort Shafter is the headquarters of the United States Army Pacific Command, the MACOM of U.S. Army forces in...

and reported "Large number of planes coming in from the north, three points east". The operator taking his report passed on the information repeating that the operator emphasized he had never seen anything like it, and it was an "an awful big flight."

The report was passed on to an inexperienced and incompletely trained officer who had arrived only a week earlier. He thought they had detected a flight of B-17s arriving that morning from the US. There were only six B-17s in the group, so this did not account for the large size of the plot.The officer had little grasp of the technology, the radar operators were unaware of the B-17 flight (nor its size), and the B-17's had no IFF (Identification friend or foe

Identification friend or foe

In telecommunications, identification, friend or foe is an identification system designed for command and control. It is a system that enables military and national interrogation systems to identify aircraft, vehicles, or forces as friendly and to determine their bearing and range from the...

) system, nor any alternative procedure for identifying distant friendlies as the British had developed during the Battle of Britain

Battle of Britain

The Battle of Britain is the name given to the World War II air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940...

. The raid on Pearl Harbor started 55 minutes later, and signaled the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

' formal entry into World War II

World War II

a day later.

The radar operators also failed to communicate the northerly bearing of the inbound flight. The US fleet instead was fruitlessly searching to the southwest of Hawaii, believing the attack to have been launched from that direction. In retrospect this may have been fortuitous, since they would have met the same fate as the ships in Pearl Harbor had they attempted to engage the vastly superior Japanese carrier fleet, with enormous casualties.

After the Japanese attack, the RAF agreed to send Watson-Watt to the United States to advise the military on air defense technology. In particular Watson-Watt directed attention to the general lack of understanding at all levels of command of the capabilities of radar- with it often being regarded as a freak gadget "producing snap observations on targets which may or may not be aircraft." General Gordon P. Saville

Gordon P. Saville

Gordon Philip Saville was a United States Air Force major general who was an outspoken proponent of tactical aviation amidst a brotherhood of airmen who promoted strategic bombing. With Benjamin S. Kelsey, Saville co-wrote the technical specifications which led to the P-38 Lightning and the P-39...

, director of Air Defense at the Army Air Force headquarters referred to the Watson-Watt report as "a damning indictment of our whole warning service".

Use of SCR-270 radar elsewhere in World War II

In the Philippines, the Far East Air Force did not fare much better than the defending air force at Pearl Harbor. Though FEAF had five SR-270Bs, only two were functioning on 8 December 1941, one by a detachment of the 4th Marine Regiment to protect Cavite Naval Base. Even with correct detection of enemy flights from the AAF's operational radar at Iba, command disorganization resulted in many of the defending fighters in the Philippines were also caught on the ground and destroyed, as was the largest concentration of B-17's (19) outside of the continental US.http://www.h-net.org/reviews/showpdf.cgi?path=320171145561048#search=%22%22december%208%22%20radar%20iba%22 The Iba set was destroyed in the initial attack on Iba on 8 December. After the first day, the effective striking power of the Far East Air Force had been destroyed, and the fighter strength seriously reduced. The Marine unit was withdrawn to Bataan

Bataan

Bataan is a province of the Philippines occupying the whole of the Bataan Peninsula on Luzon. The province is part of the Central Luzon region. The capital of Bataan is Balanga City and it is bordered by the provinces of Zambales and Pampanga to the north...

in January 1942, where it was successfully employed in conjunction with an SCR-268 antiaircraft gun-laying radar

SCR-268 radar

The SCR-268 was the US Army's first radar system. It was developed to provide accurate aiming information and used in gun laying systems and directing searchlights against aircraft....

to provide air warning to a small detachment of P-40s operating from primitive fields.

Key commanders responsible for the defense of installations vulnerable to air attack did not appreciate the need for and capabilities of the air defense assets they had, and how vital radar was to those defenses. The vulnerability was well demonstrated in war games- in particular those of United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

Fleet Problem IX that annihilated the locks on the Panama canal, and Fleet Problem XIII, when the Pearl Harbor fleet was destroyed in a mock attack by 150 planes in 1932.http://txspace.tamu.edu/bitstream/1969.1/2658/1/etd-tamu-2005B-HIST-Wadle.pdf

At Midway Island

Midway Atoll

Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...

in June 1942, an SCR-270 antenna and shack http://books.google.com/books?id=wpFMWeLmp4cC&pg=PA243&vq=scr-270s&dq=%22SG+radar%22+midway&source=gbs_search_s were located at the western end of Sand Island http://books.google.com/books?id=q1k_5R-6rUUC&pg=RA1-PA131&vq=radar+sand+island&dq=pearl+harbor+second+attack&source=gbs_search_s. During the Battle of Midway

Battle of Midway

The Battle of Midway is widely regarded as the most important naval battle of the Pacific Campaign of World War II. Between 4 and 7 June 1942, approximately one month after the Battle of the Coral Sea and six months after Japan's attack on Pearl Harbor, the United States Navy decisively defeated...

, this radar was used to warn the island of incoming Japanese air attacks http://books.google.com/books?id=wpFMWeLmp4cC&pg=PA243&vq=scr-270s&dq=%22SG+radar%22+midway&source=gbs_search_s#PPA244,M1 and to successfully direct the fighter interception that followed, but the island's radar did not play any significant part in the main carrier-action portion of the battle that followed.

SCR-270s Today

After its use by the military, the Pearl Harbor unit (s/n 012) was loaned to the University of Saskatchewan

University of Saskatchewan

The University of Saskatchewan is a Canadian public research university, founded in 1907, and located on the east side of the South Saskatchewan River in Saskatoon, Saskatchewan, Canada. An "Act to establish and incorporate a University for the Province of Saskatchewan" was passed by the...

in Saskatoon (along with a second unit to the National Research Council

National Research Council of Canada

The National Research Council is an agency of the Government of Canada which conducts scientific research and development.- History :...

in Ottawa

Ottawa

Ottawa is the capital of Canada, the second largest city in the Province of Ontario, and the fourth largest city in the country. The city is located on the south bank of the Ottawa River in the eastern portion of Southern Ontario...

), who, unaware of its history, used it to image aurora

Aurora (astronomy)

An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...

for the first time in 1949. The technique was published in 1950 in Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

, and was a field of active research for some time. In 1990, having sat derelict for years, they received a phone call informing them of the historical nature of the radar, and requesting it be sent back to the US for preservation. It is now located at the Historical Electronics Museum

Historical Electronics Museum

The National Electronics Museum located in Linthicum, Maryland, displays the history of the United States defense electronics.- About :The National Electronics Museum houses assortments of telegraphs, radios, radars and satellites exhibits. Admission is $3 for adults, $1 for seniors and students,...

near Baltimore

Baltimore

Baltimore is the largest independent city in the United States and the largest city and cultural center of the US state of Maryland. The city is located in central Maryland along the tidal portion of the Patapsco River, an arm of the Chesapeake Bay. Baltimore is sometimes referred to as Baltimore...

External links

1942 view of an SCR-271 at the [Radar Installation and Maintenance School at Camp Evans]http://www.infoage.org/cs-12-08-2005p34.html, Wall, NJ

http://www.ibiblio.org/hyperwar/USA/ref/FM/index.html FM 11-25
http://www.monmouth.army.mil/historian/photolist.php?fname=Radar%2FSCR-270 pics of SCR-270
film of scr 270 at fort bliss/white sands http://www.criticalpast.com/video/65675047474_radar-equipment_radar-station_equipment-operating_White-Sands-Proving-Ground

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.