Radar in World War II
Encyclopedia
Both the Allies
and Axis powers
used radar
in World War II
, and many important aspects of this conflict were greatly influenced by this revolutionarily new technology.
The basic technology of radio-based detection and tracking evolved independently and with great secrecy in a number of nations during the second half of the 1930s. At the start of the war in Europe in September 1939, both Great Britain
and Germany
had begun the deployment of these systems. In Great Britain this technology was called RDF, standing for Range and Direction Finding
, while in Germany the name Funkmessgerät (radio measuring device) was often used.
By the time of the Battle of Britain
in mid-1940, the Royal Air Force
(RAF) had incorporated RDF stations as vital elements in Britain's air-defence capabilities. The German Funkmessgerät, could not assist in Germany's offensive capability and was thus not supported by Adolf Hitler
. Also, the Luftwaffe
(German Air Force) did not sufficiently appreciate the importance of RDF stations in air defence, contributing to Germany's lack of success in this early stage of the war.
Although the technology was first demonstrated in the United States
during December 1934, it was only when war clouds loomed that the U.S. military authorities recognized the great potential of radio-based detection and tracking, and began the development of ship- and land-based systems. The first of these were fielded by the U.S. Navy in early 1940, and a year later by the U.S. Army. The acronym RADAR (for RAdio Detection And Ranging) was coined by the U.S. Navy in 1940, and the subsequent name "radar" was soon widely used.
While the great benefits of operating in the microwave
portion of the radio spectrum
were known, transmitters for generating microwave signals of sufficient power were not available; thus, all early radar systems operated at much lower frequencies. In February 1940, researchers in Great Britain developed the resonant-cavity magnetron
, capable of producing microwave power in the kilowatt range, opening the path to second-generation radar systems.
As the conflict in Europe got underway, it was realised in Great Britain that the development and manufacturing capabilities of the United States were vital to success in the war; thus, although America was not yet a direct participant in the war, Prime Minister Winston Churchill
directed that the technology secrets of Great Britain be shared with this nation in exchange for the needed capabilities. In the summer of 1940, the Tizard Mission
brought these secrets to the United States. The cavity magnetron was included, and almost immediately the Radiation Laboratory
was established to develop microwave radars using the magnetron.
In addition to Great Britain, Germany, and the United States, wartime radars were also developed and used by the Soviet Union
and Japan
, as well as the technically advanced Commonwealth Nations
Australia
, Canada
, New Zealand
, and South Africa
. These developments and the resulting systems are also described herein. The Wikipedia article History of Radar
provides a summary of pre-war developments in all of these countries as well as early activities in the Netherlands
, France
, Italy
, and Hungary
.
's Aeronautical Research Committee
in early 1935, responding to the urgent need to protect Great Britain from German bomber attacks. Robert A. Watson-Watt
at the Radio Research Station, Slough, was asked to comment on the feasibility of a radio-based "death ray". In response, Watson-Watt and his scientific assistant, Arnold F. Wilkins
, replied that a more fruitful activity would be in using radio to detect and track enemy aircraft. On February 26, 1935, a preliminary test, commonly called the Daventry Experiment, showed that radio signals reflected from an aircraft could be detected. Research funds were quickly allocated, and a development project was started in great secrecy on the Orford Ness
Peninsula in Suffolk
on the coast of the North Sea. E. G. Bowen was responsible for developing the pulsed transmitter. On June 17, 1935, the research apparatus successfully detected an aircraft at a distance of 17 miles. In August, A. P. Rowe
, representing the Tizard Committee, suggested the technology be code-named RDF, meaning Range and Direction Finding
.
in Suffolk
. While this operation was under the Air Ministry, both the Army and Navy became involved and soon initiated their own programs.
At Bawdsey, outstanding engineers and scientists evolved the RDF technology, but much of the credit belongs to Watson-Watt, the head of the team, who turned from the technical side to building up a usable network of machines and the people to run them. After watching a demonstration in which his equipment operators were attempting to locate an "attacking" bomber, he noticed that the primary problem was not technological, but worker overload. Following Watson-Watt's advice, by early 1940 the RAF had built up a layered control organization that efficiently passed information along the chain of command, and was able to track large numbers of aircraft and direct defences to them.
Immediately after the war began in September 1939, the Air Ministry RDF development at Bawdsey was temporarily relocated to University College, Dundee
in Scotland
. A year later, the operation moved to near Worth Matravers
in Dorset
on the southern coast of England, and was named the Telecommunications Research Establishment
(TRE). In a final wartime move, the TRE relocated to Malvern College
in Great Malvern
, near Birmingham
.
Some of the major RDF/radar equipment used by the Air Ministry is briefly described. All of the systems were given the official designation Air Ministry Experimental Station
(AMES) plus a Type number; most of these are listed in this link.
(or CH) were constructed along the South and East coasts of Britain, based on the successful model at Bawdsey. As one might expect from the first equipment to be deployed, CH was a simple system. The broadcast side was formed from two 300-ft (90-m) tall steel towers strung with a series of antennas between them. A second set of 240-ft (73-m) tall wooden towers were used for reception, with a series of crossed antennas at various heights up to 215 ft (65 m). Most stations had more than one set of each antenna, tuned to operate at different frequencies.
Typical CH operating conditions were:
The CH output was read with an oscilloscope
. When a pulse was sent out into the broadcast towers, the scope was triggered to start its beam moving horizontally across the screen very rapidly. The output from the receiver was amplified
and fed into the vertical axis of the scope, so a return from an aircraft would deflect the beam upward. This formed a spike on the display, and the distance from the left side – measured with a small scale on the bottom of the screen – would give the distance to the target. By rotating the receiver goniometer
connected to the antennas to make the display disappear, the operator could determine the direction to the target (this was the reason for the cross shaped antennas), while the size of the vertical displacement indicated something of the number of aircraft involved. By comparing the strengths returned from the various antennas up the tower, the altitude could be determined to some degree of accuracy.
CH proved highly effective during the Battle of Britain
, and is often credited with enabling the RAF to defeat the much larger Luftwaffe forces. Whereas the Luftwaffe had to hunt all over to find the RAF fighters, the RAF knew exactly where the German bombers were, and could converge all of their fighters on them. In modern terminology, CH was a force multiplier, allowing the RAF fighters to operate more effectively as if they were a much larger force operating at the same effectiveness as the Germans. In addition, the CH system allowed pilots to rest on the ground instead of flying continuous "standing patrols", and only needing to "scramble" (take off) when the air threat was imminent. This not only reduced pilots' workloads, but also reduced wear on engines, as well as reducing unnecessary petrol
consumption.
Very early in the battle the Luftwaffe made a series of small raids on a few of the stations, including the Bawdsey research and training station, but they were returned to operation in a few days. In the meantime the operators took to broadcasting radar-like signals from other systems in order to fool the Germans into believing that the systems were still operating. Eventually the Germans gave up trying to bomb them. The German High Command
apparently never understood the importance of radar to the RAF's efforts, or they would have assigned these stations a much higher priority – even a concerted effort would not have had much effect on the transmitters as their structure made them very resistant to blast, which passed through the spaces in the metal lattice.
To avoid the CH system, the Luftwaffe adopted other tactics. One was to approach Britain at very low levels, below the sight line of the CH stations. This was countered to some degree with a series of shorter range stations built right on the coast, known as Chain Home Low
(CHL). These systems had originally been intended to use for naval gun-laying and known as Coastal Defence (CD), but their narrow beams also meant they could sweep an area much closer to the ground without seeing the reflection of the ground (or water) – known as clutter
. Unlike the larger CH systems, CHL had to have the broadcast antenna itself turned, as opposed to just the receiver. This was done manually on a pedal-crank system run by Women's Auxiliary Air Force
until more reliable motorized movements were installed in 1941.
to produce the Ground-Controlled Intercept
(GCI) stations in January 1941. In these systems the antenna was rotated mechanically, followed by the display on the operator's console. That is, instead of a single line across the bottom of the display from left to right, the line was rotated around the screen at the same speed as the antenna was turning.
The result was a 2-D display of the air space around the station with the operator in the middle, with all the aircraft appearing as dots in the proper location in space. Called plan position indicator
s (PPI), these dramatically simplified the amount of work needed to track a target on the operator's part. Such a system with a rotating, or sweeping, line is what most people continue to associate with a radar display. Philo Taylor Farnsworth, the American inventor of all-electronic television in 1927, contributed to this in an important way. Farnsworth refined a version of his picture tube (cathode ray tube
, or CRT) and called it an "Iatron". It could store an image for milliseconds to minutes (even hours). One version that kept an image alive about a second before fading, proved to be a useful addition to the evolution of radar. This slow-to-fade display tube was used by air traffic controllers from the very beginning of radar.
This eventuality had already been foreseen, and a successful programme by Edward George Bowen
starting in 1936 (likely at the urging of Tizard) developed a miniaturized RDF system suitable for aircraft, the Air Interception (AI) set. (Watson-Watt called the CH sets the RDF-1 and the AI the RDF-2A.) At the same time Bowen developed AI sets for aircraft to detect submarines, the Air to Surface Vessel (ASV) set was also developed, making a significant contribution to the defeat of the German U-boats.
Initial AI sets were available in 1939 and fitted to Bristol Blenheim
aircraft, replaced quickly with the better-performing Bristol Beaufighter
. These quickly put an end to German night- and bad-weather bombing over Britain. Mosquito
night intruders were fitted with AI Mk VIII and later derivatives, which, along with a device called "Serrate
" to allow them to track down German night fighters from their Lichtenstein
signal emissions, as well as a device named "Perfectos" that tracked German IFF
, allowed the Mosquito to find and destroy German night fighters. As a countermeasure the German night fighters employed Naxos ZR
signal detectors.
of Birmingham University in early 1940. This was a small device that generated microwave
frequencies much more efficiently than previous devices, allowing the development of practical centimetric
radar, operating in the radio frequency band from 3 to 30 GHz. Centimetric radar allowed for the detection of much smaller objects and the use of much smaller antennas
than the earlier lower frequency sets.
The cavity magnetron was perhaps the single most important invention in the history of radar and played a major part in the Allies' victory. In the Tizard Mission
during September 1940, it was given free to the U.S., together with several other inventions such as jet technology, so that the British could use American R&D and production facilities. The British need to produce the magnetron in large quantities was great. Consequently, Edward George Bowen
was sent as the RDF expert in the Tizard Mission to the U.S. This led to the creation of the Radiation Laboratory
(Rad Lab) at MIT
to further develop the device and its applications. Half of the radar deployed during World War II were designed at the Rad Lab, including over 100 different systems costing $1.5 billion.
When the cavity magnetron was first developed, its use in microwave RDF sets was held up because the duplexers for VHF were destroyed by the new higher-powered transmitter. This critical problem was solved in early 1941 by the T-R switch developed at the Clarendon Laboratory
of Oxford University, allowing a pulse transmitter and receiver to share the same antenna without destabilizing the sensitive receiver.
The combination of the magnetron, the T-R switch, small antennas and high resolution allowed small high quality radars to be installed in aircraft. They could be used by maritime patrol
aircraft to detect objects as small as a submarine periscope
, which allowed aircraft to attack and destroy submerged submarines, which had previously been undetectable from the air. Centimetric contour mapping
radars like H2S
improved the accuracy of Allied bombers used in the strategic bombing campaign
. Centimetric gun laying radars were much more accurate than the older technology. They made the big gunned Allied battleships more deadly and along with the newly developed proximity fuze
made anti-aircraft guns much more dangerous to attacking aircraft. The two coupled together and used by anti-aircraft batteries, placed along on the German V-1 flying bomb
flight paths to London
, are credited with destroying many of the flying bombs before they reached their target.
When the war started and the Air Ministry activities were relocated to Dundee in Scotland, the Army Cell became a part of a new developmental center at Christchurch
in Dorset
on the south coast. John D. Cockcroft
a physicist from Cambridge University and later a Nobel Prize Laureate, became the Director. With enlarged activities, the facility became the Air Defence Research and Development Establishment (ADRDE) in mid-1941. A year later, the ADRDE relocated to Great Malvern
, in Worcestershire
near Birmingham
. In 1944, this was reorganized as the Radar Research and Development Establishment (RRDE).
As the war started, GL Mk I sets were used overseas by the British Army in Malta
and Egypt
in 1939–40. Seventeen sets were sent to France with the British Expeditionary Force
; most of these were destroyed at the Dunkirk evacuation in late May 1940, but a few were captured and gave the Germans their first full information on British RDF hardware. An improved version, GL Mk II, was used throughout the war; some 1,700 sets were put into service, including over 200 supplied to the Soviet Union. Operational research found that anti-aircraft batteries using the GL averaged 4,100 rounds fired per hit, compared with about 20,000 rounds for unassisted guns.
began the development of a Coastal Defense (CD) system that involved some of the most significant advancements in the early history of radar. The 200-MHz transmitter and receiver already being developed for the AI and ASV sets of the Air Defense were used as starters, but, since the CD would not be airborne, more power and a much larger antenna were possible. The transmitter power was increased to 150 kW. A huge dipole
array, 10-ft high and 24-ft wide, was developed, giving much narrower beams and higher gain. This "broadside" array
was rotated 1.5 revolutions per minute, sweeping a field covering 360 degrees. Lobe switching
was incorporated in the transmitting array, giving higher directional accuracy. For analysis of the system, Butement formulated the first – at least in Great Britain – mathematical relationship that would later become the well-known "radar range equation".
Early tests showed that the CD set had much better capabilities for detecting aircraft at low altitudes than the existing CH. Consequently, the CD was also adopted by the Air Defense to augment the CH stations; in this role it was designated the Chain Home Low
(CHL).
in Hampshire
, the Experimental Department had an excellent capability for developing wireless valves (vacuum tubes), and, in fact, had provided the tubes used by Bowden in the initial transmitter at Orford Ness. With excellent research facilities of its own, the Admiralty decided to have its RDF development at the HMSS. This remained in Portsmouth after the start of the war, but in 1942, it was moved inland to safer locations at Witley
and Haslemere
, both in a county in the South East of England named Surrey
. These two operations became the Admiralty Signal Establishment (ASE).
A few representative radars are described. Note that the type numbers are not sequential by date.
(Royal Italian Navy) off the coast of Greece. Type 281B was a modification to use a common transmitting and receiving antenna. The Type 281, including the B-version, was likely the most used metric system of the Royal Navy throughout the war.
The initial Type 271 primarily found service on smaller vessels. At ASE Witley, this set was modified to become Type 272 and Type 273 for larger vessels. With larger reflectors, the Type 273 also served well as air-warning against low-flying aircraft, with a range up to 30 miles. A close relative was the Type 277, a "nodding" 10-cm height-finding system. The "cheese-style" antenna was mounted vertically to generate a horizontally flattened beam. This was the first Royal Navy radar with a plan-position indicator. In addition to the microwave warning systems, Coales developed the Type 275 and Type 276 microwave fire-control sets. Further development in magnetrons resulted in 3.2-cm (9.4-GHz) devices generating 25-kW peak power. These were used in the Type 262 fire-control radar and Type 268 target-indication and navigation radar.
and Leo C. Young
, then with the U.S. Navy Aircraft Radio Laboratory, noticed that a ship crossing the transmission path of a radio link produced a slow fading in and out of the signal. They reported this as a Doppler effect|Doppler-beat interference that might be used in detecting the passing of an enemy vessel, but no further research was done at that time. In 1930, Lawrence A. Hyland
. working for Taylor at the Naval Research Laboratory (NRL) observed the Doppler-beat interference from a passing airplane. This was reported by Taylor to higher authorities; Hyland, Taylor, and Young were granted a patent (U.S. No. 1981884, 1934) for a "System for detecting objects by radio". It was recognized that detection systems would also need to give range measurements, and funding was provided to a project using a pulsed transmitter. This project was assigned to a team led by Robert M. Page
, and in late December 1934, a breadboard apparatus successfully detected an aircraft at a range of one mile.
The Navy, however, did not follow this initial effort with a vigorous pursuit, and it was not until January 1939, that their first prototype system, the 200-MHz (1.5-m) XAF, was tested at sea. The Navy coined the acronym RAdio Detection And Ranging (RADAR) for this technology, and in late 1940, ordered this to be exclusively used in documents.
Taylor's 1930 report had been passed on to the U.S. Army's Signal Corps Laboratories
(SCL). Here, William R. Blair
had projects underway in detecting aircraft from thermal radiation
and engine ignition noise, and soon started a project in Doppler-beat detection. Following the success by Page with pulse-transmission, the SCL soon had their own project in this area. In 1936, Paul E. Watson
led in the development of a pulsed system that on December 14 detected aircraft flying in and out of New York City
at ranges up to seven miles. By 1938, this had evolved into the Army's first Radio Position Finding (RPF) set, designated SCR-268 (SCR meaning Signal Corps Radio
, a cover for this secret technology). It operated at 200 MHz 1.5 m, with 7-kW peak power. The received signal was used to direct a searchlight
.
In Europe, the continued war with Germany had drained the United Kingdom of resources, and the decision was made by Prime Minister Winston Churchill
to give UK's existing technology secrets to the United States in exchange for access to related American secrets and manufacturing capabilities. In September 1940, the Tizard Mission
coordinated this exchange, including the cavity magnetron
, Great Britain's greatest secret.
When the exchange began, the British were surprised to learn they were not unique in their possession of pulse-radar technology. The U.S. Navy's pulse radar system, the CXAM
, was found to be very similar in capability to their Chain Home
technology. Although the U.S. had developed pulsed radar independent of the British, there were serious weaknesses in America's efforts, the greatest of which was the lack of integration of radar into a unified air defense system. Here the British were without peer.
The result of the Tizard Mission was a major step forward for utilization of radar technology, both in the transfer of the organizational knowledge that Watson-Watt had worked out as well as the British microwave technology. Although both the NRL and SCL had experimented with 10–cm transmitters, they were stymied by the problem of insufficient transmitter power. The cavity magnetron was the answer the U.S. was looking for, and it led to the creation of the Radiation Laboratory
(Rad Lab). Before the end of 1940, the Rad Lab was started at MIT, and thereafter essentially all radar development in the U.S. was in centimeter-wavelength systems. This major center for research employed almost 4,000 people at its peak during World War II.
Two special radar-related organizations should be noted. As the Rad Lab began operations at MIT, a companion group called the Radio Research Laboratory
(RRL) was established at nearby Harvard University
. Headed by Frederick Terman
, this was devoted to research and development in electronic countermeasures
to radar. Another organization was the Combined Research Group (CRG) housed in highest secrecy at the NRL. This involved American, British, and Canadian personnel charged with developing standardized Identification Friend of Foe
(IFF) systems used with radars, vital in preventing fratricide
.
; these 200-MHz (1.5-m), 15-kW sets went into limited production with first deliveries in May 1940. The CXAM was refined into the SK early-warning radar, with production deliveries starting in late 1941. This 200-MHz (1.5-m) system used a "flying bedspring" antenna and had a plan position indicator
(PPI). With 200-kW peak-power output, it could detect aircraft at ranges up to up 100 miles, and ships to about 30 miles. The SK remained the standard early-warning radar for large U.S. vessels throughout World War II. Derivatives for smaller vessels included the SA and SC. About 500 of these early-warning sets of all versions were built. The related SD was a 114-MHz (2.63-m) set designed by the NRL for use on submarines; with a periscope-like antenna mount, it gave early warning but not the direction of approaching aircraft. The BTL developed a 500-MHz (0.6-m) fire-control radar designated FA (later designated Mark 1). A few went into service in mid-1940, but with only 2-kW power, they were soon replaced.
As previously described, the SCL's first radio-based detection and tracking system, designated SCR-268, was demonstrated in late 1938. Even before this went into service, Harold Zahl
led a team at the SCL in developing a better system; the SCR-270 was the mobile version, and the SCR-271 a fixed-position version. Operating at 106 MHz (2.83 m) with 100 kW pulsed power, these had a range up to 240 miles and began entry into service in late 1940. On December 7, 1941, an SCR-270 at Oahu
in Hawaii
detected the attacking Japanese aircraft at a range of 132 miles (212 km), but this information was not used effectively at the command level.
Only one other metric radar of significance was developed by the SCL. After Pearl Harbor, there was concern that a similar attack might be used to destroy locks at the vital Panama Canal
. A transmitter tube that delivered 240-kW pulsed power at 600 MHz (0.5 M) had been developed by Zahl. A team led by John W. Marchetti
used this tube in adapting an SCR-268 suitable for picket ships
operating up to 100 miles offshore. The same basic set was modified to become the AN/TPS-3, a light-weight, portable, early-warning radar used at beachheads and captured airfields in the South Pacific. About 900 of these radars were produced.
A British ASV Mk II, was brought to America by the Tizard Mission. With the ASE for use on large patrol aircraft such as the PBY Catalina
. This was America's first airborne radar in operational service; about 7,000 ASEs were built. The NRL was already working on a 515-MHz (58.3-cm) air-to-surface radar for the TBF Avenger
, a new fighter-bomber. Portions of the ASE were adopted for this radar, and it went into production as the ASB when the U.S. entered the war. This set was also adopted by the newly formed Army Air Forces as the SCR-521. The last of the non-magnetron radars, over 26,000 ASB/SCR-521 sets were built.
The history of World War II radar could not be complete without noting the Variable Time (VT)
Fuze. Although not a radar per se, it was closely associated with this technology and involved one of the largest financial outlays of World War II. In the summer of 1940, the National Defense Research Committee
(NDRC), predecessor of the OSRD (noted later) asked Merle Tuve
of the Carnegie Institution of Washington to take the lead in developing a device that could increase the probability of kill
for gun projectiles. From this, the variable-time fuze emerged as an improvement for the fixed-time fuze commonly used to detonate the projectile. The resulting device sensed when the projectile neared the target – thus, the name variable-time was applied. Alan Butement
had actually conceived the idea for a proximity fuse while he was developing the Coastal Defense system in Great Britain during 1939, and his basic concept had been brought to the U.S. by the Tizard Mission.
A VT fuze, screwed onto the head of a projectile, radiated a CW signal in the 180–220 MHz range. As the projectile neared its target, this was reflected at a Doppler shifted
frequency by the target and beat with the original signal, the amplitude of which triggered the detonation. The device used electronics much smaller than anything previously built, and 112 industries and research institutions were eventually involved. In 1942, the project was transferred to the Applied Physics Laboratory
, formed by Johns Hopkins University
for this purpose. During the war, some 22 million VT fuses for several sizes of projectiles were manufactured.
In the period 1941–1945, many different radars operating in the microwave region were developed in America. These mainly originated in the Rad Lab where some 100 different types were initiated. Although many industries manufactured sets (primarily for the Navy and Army Air Forces), only Bell Telephone Laboratories (NTL) had major involvement in development. The two primary military research operations, NRL and SCL, had major efforts in component development, system engineering, testing, and other support to the Rad Lab, but did not take on wartime responsibilities for developing new centimeter radar systems.
Operating under the Office of Scientific Research and Development
, an agency reporting directly to President Franklin Roosevelt
, the Rad Lab was directed by Lee Alvin DuBridge
with the eminent scientist Isidor Isaac Rabi
serving as his deputy. E. G. "Taffy" Bowen
, one of the original developers of RDF and a member of the Tizard Mission, remained in the U.S. as an adviser to the Rad Lab.
As it was formed, the Rad Lab was assigned three initial projects: a 10 cm airborne intercept radar, a 10 cm gun-laying system for anti-aircraft use, and a long-range aircraft navigation system. The cavity magnetron brought to America by the Tizard Mission was exactly duplicated by the Bell Telephone Laboratories
(BTL) and placed into production for use by the Rad Lab in the first two projects. The third project, which did not involve radar, ultimately became LORAN
, the first worldwide radio navigation system. LORAN was conceived by Alfred Lee Loomis
, a financial tycoon and private scientist who was instrumental in starting the Rad Lab.
To get underway, the Rad Lab built an experimental breadboard set with a 10 cm transmitter and receiver using separate antennas (the T-R switch was not yet available). This was successfully tested from atop the laboratory at MIT in February 1941, detecting an aircraft at a range of 4 miles.
The Rad Lab and BTL also initiated improvements in the magnetron, extending the device and associated systems to higher wavelengths. As more frequencies were used, it became common to refer to centimeter radar operations in the following bands:
The K-band was divided because of absorption by atmospheric water vapor. These ranges are those given by the IEEE Standards. Slightly divergent values are shown in other standards, such as those of the RSGB
.
having azimuth and elevation
scanning capabilities. Cathode-ray tube indicators and appropriate controls were also added. This was very much a team effort, but Edwin McMillan
was responsible for building and testing the engineering set. This was first flight tested near the end of March 1941, giving target returns at up to five-miles distance and without ground clutter
, a primary advantage of microwave radar. Designated SCR-520, this was America's first microwave radar. (The Air Forces was then a part of the U.S. Army and used the SCR designation for radio-based systems.) Although this saw limited service on some larger patrol aircraft, it was too heavy for fighter aircraft. Later upgraded to the much lighter SCR-720, thousands of these sets were manufactured and used extensively by both the U.S. and Great Britain (as the AI Mk X) throughout the war.
as the leader, started with the same 10-cm breadboard used in the AI project. Development of the GL system was, however, far more complex. A highly complex servomechanism was needed to direct a large parabolic reflector, and an automatic tracker was also needed. Upon the detection of a target, the receiver output would be used to put the servo control into a track-lock mode. The mount and reflector were developed in cooperation with the Central Engineering Office of Chrysler
. The BTL developed the electronic analog computer, called the M-9 Predictor-Corrector
unit, containing 160 vacuum tubes. All of this finally came together for testing by the customer (the Army Signal Corps) in May 1942. Designated the SCR-584
Anti-Aircraft Gun-Laying System, about 1,500 of these were used in the European and Pacific war theaters starting in early 1944.
, the 50 kW SG shipboard set was given sea trials in May 1941, followed shortly by the ASG version for large patrol aircraft and Navy blimp
s. With a gyro-stabilized mount, the SG could detect large ships at 15 miles and a submarine periscope at 5 miles. About 1,000 of these sets were built. The ASG was designated AN/APS-2 and commonly called "George"; some 5,000 of these were built and used very effectively in finding enemy submarines.
A compact version of the SG for PT boat
s was designated the SO. These were introduced in 1942. Other direct descendants included the SF, a search-set for lighter warships, the SH for large merchant vessels, and the SE and SL, similar to the SO, for other smaller ships. The Navy also adopted versions of the Army's SCR-584 (without the M-9 unit but with gyro-stabilizers) for shipboard search radars, the SM for heavy carriers and the SP for smaller carriers. None of these were produced in large quantities, but were of great service in the war effort.
The BTL developed the SJ, an S-Band supplement for the SD meter-wave radar on submarines. The antenna for the SJ could be sweep the horizon to about 6 miles with good accuracy. Late in the war, the SV became available, increasing the detection range to 30 miles.
as the leader, about 20 percent of the staff would ultimately be involved. Designated AN/APS-20, this 20 cm (1.5 GHz), 1 MW radar weighing 2,300 pounds including a 8-foot radome
enclosing a spinning parabolic antenna. Carried by a TBF Avenger
carrier-based aircraft, it could detect large aircraft at ranges up to 100 miles. The airborne system included a television camera to pick up the PPI display, and a VHF link transmitted the image back to a Combat Information Center
on the home carrier. The system was first flown in August 1944 and went into service the following March. This was the foundation from which the post-war Airborne Warning and Control System (AWACS) concept evolved.
antenna having excellent radiation characteristics. When the 3 cm magnetron was developed, the Alvarez antenna was used in a number of X-Band radars. The Eagle, later designated AN/APQ-7, provided a map-like image of the ground some 170 miles along the forward path of a bomber. About 1,600 Eagle sets were built and used by the Army Air Forces primarily over Japan. The same technology was used in developing the ASD (AN/APS-2 commonly known as "Dog"), a search and homing radar used by the Navy on smaller bombers; this was followed by several lighter versions, including the AIA-1 known as the "radar gunsight".
The Alvarez antenna was also used in developing the Ground Control Approach (GCA), a combined S-Band and X-Band blind-landing system for military airports; this system was particularly used in assisting planes returning from bombing runs.
The BTL also developed X-Band radars. The Mark 8 (FH) fire-control radar, was based on a new type of antenna developed by George Mueller
. This was an end-fired array of 42 pipe-like waveguide
s that allowed electronic steering of the beam. The Mark 22 was a "nodding" system used for target height-finding with fire-control radars. With an antenna shaped like an orange slice, it gave a very narrow, horizontal beam to search the sky. The Army also adopted this as the AN/TPS-10, a land-version that was commonly called "Li'l Abner".
Although not implemented into a full system until after the war, the monopulse technique
was first demonstrated at the NRL in 1943 on an existing X-Band set. The concept is attributed to Robert Page, and was developed to improve the tracking accuracy of radars. Following the war, essentially all new radar systems used this technology, and was the basis of the AN/FPS-16
, the most widely used tracking radar in history.
with the invasion by Germany on June 22, 1941. Although the USSR had outstanding scientists and engineers, began research on what would later become radar (radiolokatsiy) as soon as anyone else, and made good progress with early magnetron development, they entered the war without a fielded, fully capable radar system.
In only a few years after the close of World War I, Germany's Luftwaffe had aircraft capable of penetrating deep into Soviet territory. Visual observation was use for detecting approaching aircraft. For nighttime detection, the Glavnoe artilkeriisko upravlenie (GAU, Main Artillery Administration), of the Red Army, had developed an acoustical unit that was used to aim a searchlight at the aircraft. These techniques had a problem with aircraft that were above the clouds or at a considerable distance; to overcome this, research was also initiated on detection by electromagnetic means. General-leitenant (Lieutenant-General) M. M. Lobanov was responsible for these efforts in the GAU, and later thoroughly documented this activity.
, initially at the Leningradskii Elektrofizicheskii Institut, (Leningrad Electro-Physics Institute, LEPI). Here, Abram F. Ioffe
, generally considered the leading physicist at that time in the Soviet Union, was the Scientific Director. The LEPI concentrated on radiating continuous wave
(CW) signals, detecting the existence and direction of their reflections for use in early warning systems.
While the GAU was mainly interested in detection, the Voiska Protivo-vozdushnoi aborony (PVO, Air Defense Forces) was interested in also determining the distance to the aircraft (the range). Pavel K. Oshchepkov
on the PVO technical staff in Moscow, strongly believed that the radiolokatory (radio-location) equipment should be pulsed, thus potentially allowing the range to be determined directly. He was transferred to Leningrad to be in charge of a Special Construction Bureau (SCB) for radio-location equipment.
To examine the various types of detection, a meeting was called by the Russian Academy of Sciences
; this was held at Leningrad on January 16, 1934, and chaired by Ioffe. Radio-location emerged as the most promising technique, but the type (CW or pulsed) as well as the wavelength region (high frequency
or microwave
) were left to be resolved
At the SCB, Oshchepkov's team developed an experimental pulsed radio-location system operating at 4 m (75 MHz.). This had a peak power of about 1 kW and a 10-μs pulse duration; separated transmitting and receiving antennas were used. In April 1937, test showed a detection range of near 17 km at a height of 1.5 km. Although this was a good beginning for pulsed radio-location, the system was not capable of directly measuring range (the technique of using the pulses for determining range was known from studies of the ionosphere
but was not initially incorporated ). Although he never had the opportunity to add ranging to his system, Oshchepkov is nevertheless often called the father of radar in the Soviet Union.
While Oshchepkov was working on pulsed systems, work continued on CW research at the LEPI. In 1935, the LEPI became a part of the Nauchno-issledovatel institut-9 (NII-9, Scientific Research Institute #9), one of several technical organizations under the GAU. With M. A. Bonch-Bruevich
as the Scientific Director, research continued in CW techniques. Several experimental systems were developed, including a VHF set designated Bistro (Rapid) and Burya (Storm) operating in the microwave region. The best elements of these were incorporated into a mobile system called Ulavlivatel Samoletov (RUS, Radio Catcher of Aircraft), soon designated as RUS-1. This CW, bi-static
system had a truck-mounted transmitter operating at 4.7 m (64 MHz) and two truck-mounted receivers.
In June 1937, all of the work in Leningrad on radio-location suddenly stopped. The infamous Great Purge
of Joseph Stalin
swept over the military high commands and the supporting scientific community, resulting in near two million executions. The SCB was closed; Oshchepkov was charged with "high crimes" and sentenced to 10 years at a Gulag
penal labor camp. The NII-9 was also intended to be closed, but was saved through the influence of Bonch-Bruyevich, who had been a favorite of Vladimir Lenin
in the prior decade, NII-9 as an organization was saved, and Bonch-Bruyevich was named the new director. Overall, this resulted in a loss of more than a year in development activities.
The RUS-1 system was tested and put into production in 1939, then entered limited service in 1940, becoming the first deployed radio-location system in the Red Army. Bonch-Bruyevich died in March, 1941, and there was no strong leader to further push the CW radio-location developments.
The Nauchnoissledovatel skii ispytalel nyi institut suyazi RKKA (NIIIS-KA, Scientific Research Institute of Signals of the Red Army), an organization that had originally highly opposed radio-location technology, was now placed in overall control of this development in all of the Soviet Union. They took over Oshchepkov's pulsed system, and by July 1938, had a fixed-position, bistatic experimental system that detected an aircraft at 30-km range at heights of 500 m, and at 95-km range for high-flying targets at 7.5 km altitude.
The project was then taken up by Ioffe's LPTI, resulting in the development of a system designated Redut (Redoubt) with 50-kW peak-power and a 10-μs pulse-duration. The Redut was first field tested in October 1939, at a site near Sevastopol
, a strategic port in Ukraine on the coast of the Black Sea
.
During 1940, the LEPI took over Redut and developed the very important capability of range measurements. A cathode-ray display, made from an oscilloscope, was used to show the range information. In July 1940, the resulting system was designated RUS-2. A transmit-receive device (a duplexer) to allow operating with a common antenna was developed in February 1941. All of this testing was done at an experimental station at Toksovo
(near Leningrad), and an order was placed with the Svetlana Factory for 15 systems.
The final RUS-2 had pulse-power of near 40 kW at 4 m (75 MHz). The equipment was in a cabin on a motor-driven platform, and with a seven-element Yagi-Uda antenna mounted about five meters above the roof. The cabin, and thus the antenna, could be rotated over a large sector to aim the transmit-receive pattern. The detection range was 10 to 30 km for targets as low as 500 m and 25 to 100 km for higher-altitude targets. The variance was about 1.5 km for range and 7 degrees for azimuth.
(UIPT) operated in close cooperation with Kharkiv University
(KU). The UIPT became known outside the USSR, and attracted visits from world-recognized physicists such as Niels Bohr
and Paul Dirac
. Future Nobel Laureate Lev Landau
headed the Theoretical Department. The department-level Laboratory of Electromagnetic Oscillations (LEMO) was led by Abram A. Slutskin
.
At the LEMO, magnetrons were a major item of research. By 1934, a team led by Aleksandr Y. Usikov had developed a number of segmented-anode magnetrons covering 80 to 20 cm (0.37 to 1.5 GHz), with output power between 30 and 100 W. Semion Y. Braude developed a glass-cased magnetron producing up to 17 kW with 55 percent efficiency at 80 cm (370 kHz), tunable over a wavelength change of 30 percent. These were described in detail in German-language journal papers – a practice adopted by the UIPT to gain widespread readership of their work.
In 1937, the NIIIS-KA contracted with the LEMO for developing a pulsed radio-location system for anti-aircraft applications. The project was code-named Zenit (a popular football team at the time) and was under the guidance of Slutskin. The transmitter development was led by Usikov. The unit used a 60-cm (500-MHz) magnetron pulsed at 7–10-μs duration and providing 3-kW pulsed power, later increased to near 10 kW.
Braude led the development of the receiver. This was a superheterodyne unit initially using a tunable magnetron as the local oscillator, but this lacked stability and was replaced with a circuit using an RCA type 955 acorn triode. The returned pulses were displayed on a cathode-ray oscilloscope
, giving range measurement.
Zenit was first tested in October 1938. In this, a medium-sized bomber was detected at a range of 3 km, and needs for improvements were determined. After the changes had been made, a demonstration was given to all of the interested customers in September 1940. It was shown that the three coordinates (range, altitude, and azimuth) of an aircraft flying at heights between 4,000 and 7,000 meters could be determined at up to 25-km distance, but not with suitable accuracy. Also, with the antennas aimed at a low angle there was a dead zone of some distance; this was caused by interference from ground-level reflections.
While this performance was not satisfactory for immediate gun-laying applications, it did show the way for future systems. Another characteristic, however, rendered Zenit completely unsuitable for use with fire-controllers on anti-aircraft guns. A null-reading method was used for analyzing the signals; this made it necessary to determine azimuth and elevation coordinates independently, requiring a sequence of antenna movements that took 38 seconds for the three coordinates.
Work at the LEMO continued on Zenit, particularly in converting it into a single-antenna system designated Rubin. This effort, however, was disrupted by the invasion of the USSR by Germany in June 1941. In a short while, all of the critical industries and other operations in Kharkov were ordered to be evacuated far into the East.
swept into the Soviet Union in June 1941, three massive, tank-led Army groups moved in on a 900-mile front with Leningrad, Moscow, and the Ukraine region as objectives. There followed what became known to the Soviets as the Great Patriotic War.
The Komitet Oborony (Defense Committee – the small group of leaders surrounding Stalin) gave first priority to the defense of Moscow. The critical laboratories and factories in Leningrad were to be evacuated to the East. The same would be done for Kharkiv, the technical center of Ukraine.
A number of different radar systems were produced by the Soviet Union in the relocated facilities during the war. However, some 2,600 radar sets of various types were provided by Great Britain and America under the Lend-Lease Program.
When air attacks on Leningrad began, the RUS-2 test unit that had been set up at the Toksovo experimental site was pressed into tactical operation, providing early-warning of Luftwaffe (German Air Force) raids that were often in formations of as many as 100 bombers. With a range up to 100 km, this unit gave a good warning to the city, as well as to notifying the defending fighter aircraft. This gained the attention of military leaders who previously had shown little interest in radio-location equipment.
In mid-July, the radio-location activities of the LEPI and NII-9 were sent to Moscow where they were combined with existing units of the NIIIS-KA. A RUS-2 system was set up near Moscow and manned by recently moved LPTI personnel; it was first used on July 22, when it detected at night an incoming flight of about 200 German bombers while they were 100 km away. This was the first air attack on Moscow, and it immediately led to three rings of anti-aircraft batteries being built around the city, all connected to a central command post.
Several transmitters and receivers built for RUS-2 systems were quickly adapted by the NIII-KA for fixed radio-location stations around Moscow. Designated as RUS-2S and also P2 Pegmatit, these had their Yagi antenna mounted on 20-meter steel towers and could scan a sector of 270 degrees. For building additional equipment, in January 1942, Factory 339 in Moscow became the first manufacturing facility in the Soviet Union devoted to radio-location sets (soon officially called radar). During 1942, this facility built and installed 53 RUS-2S sets around Moscow and other critical locations in the USSR.
Factory 339 had an outstanding research and engineering staff; this had earlier been administratively separated and designated as the Scientific Institute of Radio Industry No. 20 (NII-20). Victor V. Tikhomirov
, a pioneer in domestic aircraft radio engineering, was the Technical Director. (Later, the Tikhomirov Scientific Research Institute of Instrument Design
was named in his honor.) Factory 339 and the associated NII-20 dominated radar equipment development and fabrication in the USSR throughout the war.
Many sets of a number of different versions of the RUS-2 were built at Factory 339 during the war. While providing early warning, these sets suffered from the deficiency of not providing target height (elevation angle). Thus, they were mainly used in conjunction with visual-observation posts, with humans using optical devices for estimating altitude and identifying the type of aircraft.
From the time of the first efforts in radio-location, the question had been raised as to how the aircraft identification could be made – was it friendly or an enemy? With the introduction of RUS-2, this problem required an immediate solution. The NII-20 developed a unit to be carried on an aircraft that would automatically respond as "friendly" to a radio illumination from a Soviet radar. A transponder
, designated as SCH-3 and later called an Identification Friend or Foe
(IFF) unit, was placed into production at Factory 339 in 1943. This unit initially responded only to the signal of RUS-2, and only a relatively small number of these and successor units were built in the USSR.
The RUS-2 was sponsored by the PVO and intended for early warning. The GAU still wanted a gun-laying system capable of supporting the anti-aircraft batteries. Upon arriving in Moscow, the radio-location group of the NII-9 continued working for the PVO on this problem, returning to Burya, the experimental microwave set built earlier. Within a few weeks, a team led by Mikhail L. Sliozberg and with the cooperation of NII-20, developed a bi-static CW set designated Son (Sleep) using a 15-cm (2.0-GHz) magnetron.
In early October, the experimental Son set was tested in combat by an anti-aircraft battalion near Moscow. The performance of the radio-based Son was poor as compared with that of the existing optics-based Puazo-3, a stereoscopic range-finder that Oshchepkov had earlier improved. The project was discontinued, and no further attempts were made to use magnetrons in radio-location sets. After this failure, NII-9 was sent elsewhere and was no longer involved in radio-location activities. A portion of the radio-location group, including Sliozberg, remained in Moscow working for NII-20.
Shortly after Germany invaded the USSR, a delegation of Soviet military officers visited Great Britain seeking assistance in defense hardware. From their intelligence sources, the Soviets were aware of Britain's gun-laying RDF (Range and Direction Finding
) system, the GL Mk II, and asked for this equipment to be tested in the defense of Moscow. In early January 1942, Winston Churchill
agreed to send one of these systems to Russia, but with the provision that it would be totally secured under British officers and operated by British technicians.
When the ship carrying the equipment arrived at Murmansk
, a seaport off the Bering Sea
above the Arctic Circle
, there was a winter storm and unloading had to wait overnight. The next morning, it was found that the entire GL Mk II system – mounted on three trucks – had disappeared. The British Embassy made an immediate protest, and after several days the officers were informed that the equipment had been taken to Moscow for security.
It indeed had gone to Moscow – directly to NII-20 and Factory 339, where intelligence experts gave it a total examination and Sliozberg led a team in quickly reverse-engineering the hardware. In mid-February, the NII-20 announced that it had developed a new radio-location system designated Son-2a. It was essentially a direct copy of the GL Mk II.
Operating at 5 m (60 MHz), Son-2a used separate trucks for the transmitting and receiving equipment, and a third truck carried a power generator. In use, a dipole-array transmitting antenna giving a broad pattern was fixed in position atop a grounded pole. Separated from the transmitter by about 100 meters, the receiving station was on a rotatable cabin with wing-like antennas mounted on each side. A mast above the cabin held a pair of antennas that were used with a goniometer
for height-finding.
Like its GL Mk II "parent" in Great Britain, the Son-2a was not of great assistance in directing searchlights and anti-aircraft guns. Nevertheless, it was put into production and released to the Red Army in December 1942. Over the next three years, about 125 of these sets were built. In addition, over 200 GL Mk IIIC systems (improvements over the Mk II and built in Canada) were provided under the Lend-Lease
program, making the combination the most-used radar equipment in the Soviet Union during the war.
Ukraine had been the third objective of the invading German Army. By late July 1941, the mechanized forces were approaching this region, and, following orders from the Defense Committee, the UIPT in Kharkov made evacuation preparations. For this, the LEMO was split from the UIPT, and the two organizations would be sent to different cities: Alma-Ata for the main operation and, separated by 1,500 km, Bukhara for the LEMO.
While the preparations for moving were going on, the LEMO was directed to bring the experimental Zeni equipment to Moscow for testing by the NIIIS-KA. In mid-August, Usikov, Braude, and several other LEMO staff members went to Moscow, where they were attached to the NIIIS-KA. The Zenit system was installed in the Moscow outskirts, giving the opportunity for testing in combat. It was found that, while the accuracy of the system was not sufficient for precise aiming, it was satisfactory for barrage firing. It could also be used as a supplement to the RUS-2 surveillance system in guiding fighter aircraft.
In September, the team made field modifications to the Zenit and more tests were run. It was found that the detection range had been doubled, but the dead zone increased by a like amount. The NIIIS-KA believed that the prospects were good for this to be developed into a suitable system, but laboratory conditions were necessary. Thus, the Zenit and all of the NIIIS-KA staff were sent 3,200 km away to Bukhara, joining the remainder of the LEMO as it also moved.
Because of the null-reading method of analyzing the signals, the Zenit system suffered from slowness in measurements (38 seconds for determining the three coordinates) as well as accuracy. It also had a large dead zone caused by ground returns. While still at Kharkov, work had started on Rubin, a system intended to correct Zenit deficiencies. With Slutskin as LEMO Director, this project continued at Bukhara under Usikov's leadership.
A new magnetron was developed; this operated at 54 cm (470 MHz) with a pulse-power increased to 15 kW. A gas-discharge transmit-receive device (a diplexer) was developed for isolating the receiver from the direct transmitter pulse, thus allowing the use of a common transmitting-receiving structure. (A similar development had been made for the RUS-2 common antenna, but this would not have been suitable for the microwave Rubin.)
Several techniques for replacing the null-reading methods were considered, with the final selection making use of a fixture to provide a stationary dipole against which the directional position of the antenna could be continuously determined. Range, azimuth, and elevation were shown on a cathode-ray tube display. There was no provision, however, for feeding this information into an automatic unit for aiming searchlights and guns.
Separate transmitting and receiving dipoles were at the focus of a 3-meter paraboloid
reflector. The antenna assembly, with remote controls, could rotate 0–90 degrees vertically and 0–400 degrees horizontally. The width of the main beam was 16 degrees equatorial and 24 degrees meridian.
The system was carried on two trucks, the electronics and control console in one and the power generator in the other. Both the transmitter magnetron and front-end portions of the receiver were in sealed containers attached to the rear of the reflector. The antenna assembly was on rails and could be rolled out to near the truck.
By August 1943, the prototype Rubin system was completed, with all of the work performed by the small LEMO and NIIIS-KA staffs. The system was transported to Moscow where Usikov, Truten, and others conducted further tests and gave non-combat demonstrations. By this time, the British GL Mk II and its Soviet replication, Sun-2a, were also available and were possibly used in direct comparison with the Rubin; if so, the Rubin would not have faired well.
Rather than releasing the prototype for production, the Army made arrangements for the Rubin to be tried by the Red Fleet Command. At the beginning of 1944, the system was transported to Murmansk, the only non-freezing port in the Soviet Arctic. Here, despite the cold, Usikov continued with tests and demonstrations under better conditions than in the still chaotic Moscow.
Test aboard a ship showed aircraft detection at 60 km and reliable measurement starting at 40 km. The mean errors were no more than 120-m in range and 0.8-degree in azimuth and elevation angles. The time for determining the angular coordinates never exceeded 7 seconds, and the dead zone was down to 500 m. Similar accuracies were found for detecting all types of surface vessels, but with the Rubin antenna at deck level, the detection range was understandably much less than that for aircraft.
During the last year of the war, Rubin was used by the Red Fleet for air and surface surveillance in the polar sector. If the GL Mk II and its clone, SUN-2a, had not become available, the Rubin would likely have been completed much earlier and gone into production. Although never put into regular service, this system provided a good foundation for future magnetron-based radars in the Soviet Union.
led a Soviet Air Forces (VVS) design bureau, responsible for developing a twin-engine attack-dive bomber that was eventually designated Pe-2. Having gotten behind in the schedule, Petlyakov was charged with sabotage and thrown into a technical Gulag; he actually did a large part of his design while interned.
In late 1940, the VVS developed the requirement for an on-board enemy aircraft detection system. The radio-location group at NII-9 in Leningrad was directed to design such a set for the Pe-2. Most of radio-location equipment at that time was large and heavy, and for this aircraft, a small, lightweight set was needed. Also, limitations on antenna size drove the design to frequencies as high as possible. The reflex klystron (as it was later called) had just been developed by Nikolay Devyatkov
. Using this, design was started on a set designated Gneis (Origin) and operating at 16 cm (1.8 GHz).
When the NII-9 was evacuated to Moscow in July 1941, this greatly affected the schedule. Also, the reflex klystron had not been put into production and its availability in the future was doubtful; therefore, the project was terminated. The need, however, for an airborne radio-location set was now even more important; the Pe-3, a heavy fighter aircraft and successor to the Pe-2, was in production. Some of these aircraft were being configured as night-fighters, and the radar (as it was now called) was urgently needed. The NII-20 and Factory 339 took up the design, led by the Technical Director, Victor Tikhomirov.
The new set, designated Gneis-2, operated at 1.5 m (200 MHz). The Pe-3 fighter was a two-place aircraft, with the pilot and the rear gunner/radio operator seated back to back. The radar was designed as another piece of equipment for the radio operator.
The antennas were mounted above the top surface of the wings, a broad-pattern transmitting array on one wing and two Yagi receiving antennas on the other. One Yagi was directed forward and the other, a few feet away, aimed outward 45 degrees. The fuselage of the aircraft provided a shield between the transmitting and receiving antennas. The system had a range of about 4 km and could give the target's azimuth relative to the fighter's flight path.
The Gneis-2, the first aircraft radar in the Soviet Union, was proven in combat at Stalingrad during December 1942. About 230 of these sets were built during the war. A few were installed on Yak-9 and (out of number sequence) Yak-3 aircraft, the advanced fighters that eventually gave the VVS parity with the Luftwaffe. Other sets with Gneis designations were developed at Plant 339 for experimental purposes, particularly with Lavochkin La-5 fighters and Ilyushin Il-2 ground-assault aircraft, but none of these sets were placed into production.
Director of the NIIIS-KF, Red Fleet Signals Research) and later given the rank of Engineer-Admiral. He was also a Professor at Leningrad's universities and closely followed the early radio-location progress at the LPTI and NII-9. He started a research program in this technology at the NIIIS-KF, but was interrupted by being arrested in 1937 during the Great Purge and spent three years in prison.
Berg was released in early 1940 and reinstated in his positions. After reviewing the tests of Redut conducted at Sevastopol, he obtained a RUS-2 cabin and had it adapted for shipboard testing. Designated Redut-K, it was placed on the light cruiser Molotov in April 1941, making this the first warship in the RKKF with a radio-location capability. After the start of the war, only a few of these sets were built.
In mid-1943, radar (radiolokatsiya) was finally recognized as a vital Soviet activity. A Council for Radar, attached to the State Defense Committee, was established; Berg was made Deputy Minister, responsible for all radar in the USSR. While involved with all future developments in this activity, he took special interest in Navy systems. Berg was later mainly responsible for introducing cybernetics
in the Soviet Union.
Other indigenous Soviet Navy radars developed (but not put into production) during the war included Gyuis-1, operating at 1.4 m with 80- kW pulse power. This was a successor to Redut-K for early warning; the prototype was installed on the destroyer Gromkii in 1944. Two fire-control radars were simultaneously developed: Mars-1 for cruisers and Mars-2 for destroyers. Both were tested just at the close of the war, and later placed into production as Redan-1 and Redan-2, respectively.
In 1933, physicist Rudolf Kühnhold
, Scientific Director at the Kriegsmarine (German Navy) Nachrichtenmittel-Versuchsanstalt (NVA—Experimental Institute of Communication Systems) in Kiel
, initiated experiments in the microwave
region to measure the distance to a target. For the transmitter, he obtained assistance from two radio amateur operators, Paul-Gunther Erbslöh and Hans-Karl Freiherr von Willisen In January 1934, they formed a company, Gesellschaft für Elektroakustische und Mechanische Apparate (GEMA), for this work.
Development of a Funkmessgerät für Untersuchung (radio measuring device for reconnaissance) soon began in earnest at GEMA. Hans Hollmann
and Theodor Schultes, both affiliated with the prestigious Heinrich Hertz Institute in Berlin
, were added as consultants. The first development was a continuous-wave apparatus using Doppler-beat interference for detection. Kühnhold then shifted the GEMA work to a pulse-modulated system.
Using a 50 cm (600 MHz) magnetron from Philips
, their first transmitter was modulated with 2-μs pulses at a pulse repetition frequency
(PRF) of 2000 Hz. The transmitting antenna was an array of 10 pairs of dipoles with a reflecting mesh, and the receiving antenna had three pairs of dipoles and incorporated lobe switching
. The wide-band regenerative receiver used an RCA 955 acorn triode. A blocking device (a duplexer), shut the receiver input when the transmitter pulsed. A Braum tube
was used for displaying the range. It was first tested at a NVA site at the Lübecker Bay near Pelzerhaken during May 1935, detecting returns from woods across the bay at a range of 15 km (9.3 mi). In Germany, Kühnhold is often called the "Father of radar".
This first Funkmessgerät from GEMA incorporated more advanced technologies than early sets in Great Britain and the United States, but it appears radar received a much lower priority until later in World War II; by the start of the war, few had been fielded. To a large part, this was due to the lack of appreciation of this technology by the military hierarchy, especially at the top where dictator Adolf Hitler
looked on radar as a defensive weapon, and his interest was in offensive hardware. This problem was compounded by the lackadaisical approach to command staffing. It was some time before the Luftwaffe had a command and control system nearly as effective as the one set up by the Royal Air Force
in Great Britain before the war.
Wolfgang Martini
, a career Luftwaffe officer, was the primary promoter of radar to the German High Command. Although not university educated, his grasp of this technology was instinctive and his involvement was perhaps the greatest impetus to the ultimate development of wartime radar in Germany. In 1941, he was elevated to General der Luftnachrichtentruppe (General of the Air Signal Corps) and remained in this position until the end of the war in May 1945.
There were three users of radar in Germany during the war: the Luftwaffe (Air Force), the Kriegsmarine (Navy), and the Heer (Army). Although a number of development laboratories were operated by these users, the vast majority of radars were supplied by four commercial firms: GEMA, Telefunken, Lorenz, and Siemens & Halske. Near the end of the war in 1945, GEMA led the German radar work, growing to over 6,000 employees.
The official designation of radar systems was FuMG, with most also with a letter (e.g., G, T, L, or S) indicating the manufacturer, as well as a number showning the year of release and possibly a latter or number giving the nodel. There was, however, a lack of uniformity in designations.
The second type developed by GEMA was the 2.5 m (120 MHz) Seetakt. Throughout the war, GEMA provided a wide variety of Seetakt sets, manly for ships but also for several types for U-boats. Most had an excellent range-measuring module called Messkette (measuring chain) that provided range accuracy within a few meters regardless of the total range. The shipboard Seetakt used a "mattress" antenna similar to the "bedspring" on the American CXAM.
Although the Kregsmarine attempted to keep the GEMA from working with the other services, the Luftwaffe became aware of the Seetakt and ordered their own version in late 1938. Called the Freya
, this was a ground-based radar operating around 2.4 m (125 MHz) with 15-kW peak power giving a range of some 130 km. The basic Freya radar was continuously improved, with over 1,000 systems eventually built.
In 1940, Josef Kammhuber
used Freyas in a new air-defense network extending through Holland, Belgium
, and France
. Called the Kammhuber Line
by the Allies, it was composed of a series of cells code-named Himmelbett (four-poster bed), each covering an area some 45 km wide and 30 km deep, and containing a radar, several searchlights, and a primary and backup night-fighter aircraft. This was relatively effective except when the sky was overcast. A new gun-directing radar was needed to cover this deficiency and the Luftwaffe then contracted with Telefunken for such a system.
Under the leadership of Wilhelm Runge
, the new radar was built by Telefunken around a new triode capable of delivering 10-kW pulse power at 60 cm (500 MHz). Code-named Würzburg
, this had a 3-m (10-ft) parabolic reflector supplied by the Zeppelin Company and was effective at a range of about 40 km for aircraft. Two of these radars were normally added to each Himmelbett, one to pick up the target from a Freya and a second to track the fighter aircraft. Requiring only one operator, the Würzburg came to be the primary mobile, gun-laying system used by the Luftwaffe and Heer during the war. About 4,000 of the various versions of the basic system were eventually produced.
The Air Defense System was continually upgraded. To improve the range and accuracy, Telefunken developed the Würzburg-Riese and GEMA enlarged the Freya dipoles to make the Mammut and the Wassermann, The Würzburg-Riese (Giant Würzburg) had a 7.5-m (25-foot) dish (another product from Zeppelin) that was mounted on a railway carriage. The system also had an increased transmitter power; combined with the enlarged reflector, this resulted in a range of up to 70 km, as well as greatly increased accuracy. About 1,500 of this radar system were built.
The Mammut (Mammoth) used 16 Freyas linked into a giant 30- by 10-meter (100- by 33-foot) antenna with phased-array beam-directing, a technique that would eventually become standard in radars. It had a range up to 300 km and covered some 100 degrees in width with an accuracy of near 0.5 degree. About 30 sets were built, some with back-to-back faces for bi-directional coverage. The Wassermann (Waterman), had eight Freyas also with phased-array antennas, stacked on a steerable, 56-meter (190-foot) tower and giving a range up to 240 km. A variant, Wassermann-S, had the radars mounted on a tall cylinder. About 150 of all types were built starting in 1942.
A system with great range was needed to track the British and American bomber formations as they crossed Germany. For this function, consultants Theodor Schultes and Hans Hollmann
designed an experimental 2.4-m (125-MHz), 30-kW radar called Panorama. Built by Siemens & Halske in 1941, it was placed atop a concrete tower at Tremmen, a few kilometers south of Berlin. The antenna had 18 dipoles on a long, horizontal support and produced a narrow vertical beam; this rotated at 6 rpm to sweep out 360-degrees of coverage to about 110 km.
Based on the operation of Panorama, Siemens & Halske improved this system, and renamed it Jagdschloss (Hunting Lodge). They added a second switchable operation to 150 kW at 1.2 m (250 MHz), increasing the range to near 200 km. The information from the receivers was sent via co-axial cable or a 50-cm link from the tower to a central command center, where it was used to direct fighter aircraft. Hollmann's polar-coordinate (PPI) CRT was used in the display, the first German system with this device; it was also added to the Panorama. The Jagdschloss entered service in late 1943, and about 80 systems were eventually built. The Jagdwagen was a mobile, single-frequency version; operating at 54 cm (560 MHz), it had a correspondingly smaller antenna system.
Under an internally funded project, the firm Lorenz AG developed a pulse-modulated set. The Heer contracted for a few sets for Flak (anti-aircraft) support, but then this mission was transferred to the Luftwaffe. Over several years, Lorenz was unsuccessful in selling new versions called Kurfürst and Kurmark (both Holy Roman Imperial
terms). As the war continued, a need was seen by the Luftwaffe for additional radars. Lorenz again modified their sets to become the Tiefentwiel, a transportable system built to complement the Freya against low-flying aircraft, and the Jagdwagen, a mobile unit used for air surveillance. These 54-cm (560-MHz) units with plan-position indicators, had two antennas backed by parabolic, mesh reflectors on rotatable, forked frames that lifted above the equipment cabin. Starting in 1944, both of these systems were produced by Lorenz for the Luftwaffe in relatively small numbers.
Although German researchers had developed magnetrons since the early 1930s (Hans Hollmann received a U.S. patent on his device in July 1938), none had been suitable for military radars. In February 1943, a British bomber containing a H2S
radar was shot down over Holland, and the 10-cm magnetron was found intact. In short order, the secret of successful magnetrons was discovered, and microwave radar development started.
Telefunken was commissioned to build a gun-laying set for Flak applications, and at the beginning of 1944, a 10-cm set code-named Marback emerged. Using a 3-m Mannheim reflector, this set had a detection range of about 30 km. Its most important characteristic was a relative immunity to Window – the chaff used by the British as a countermeasure
against the 50-cm Würzburg. The Marback was produced in limited quantities for Flak batteries around a number of large industrial cities.
Several other 10-cm sets were developed, but none made it into mass production. One was Jagdschloss Z, a Panorama-type experimental set with 100-kW pulse-power built by Siemens & Halske. Klumbach was a similar set but with only 15-kW pulse-power and using a cylindrical parabolic reflector to produce a very narrow beam; when used with Marbach, the combined fire-control system was called Egerland.
Near the end of 1943, the Germans also salvaged radars containing 3-cm magnetrons, but sets operating at this wavelength were never produced. They did, however, play an important role in the German development of countermeasures, particularly radar warning receiver
s.
to discern the operation and its function. Tests indicated the merits of such a radar, and Wolfgang Martini also saw the value and tasked Lorenz to develop a similar system.
With backgrounds in aircraft navigation equipment and experience in developing their internally funded ground-radar systems, Lorenz had excellent capabilities for this project.
Before the end of the year, they had built a set based on their Kurfürst/Kurmark design, but greatly reduced in size and weight, and with improved electronics. Called Hohentwiel, it produced 50-kW pulse-power at 55 cm (545 MHz) and had a very low PRF of 50 Hz. The set used two separate antenna arrangements, providing searching either forward or side-looking.
The Hohentwiel was demonstrated in detecting a large ship at 80 km, surfaced submarine at 40 km, submarine periscope at 6 km, aircraft at 10 to 20 km, and land features at 120 to 150 km. A bearing accuracy of about 1 degree was obtained by rapidly switching between two receiver antennas aimed 30 degrees on each side of the transmitter antenna direction. Put into production in 1942, the Hohentwiel was highly successful. It was first used on large reconnaissance aircraft. In 1943, the Hohentwiel-U, an adaptation for use on submarines, provided a range of 7 km for surface vessels and 20 km for aircraft. Altogether, some 150 sets per month were delivered.
The use of the accurate Freya and Würzburg radars in their air-defense systems allowed the Germans to have a somewhat less vigorous approach to the development of airborne radar. Unlike the British, whose inaccurate CH systems demanded some sort of system in the aircraft, the Würzburg was accurate enough to allow them to leave the radar on the ground. This came back to haunt them when the British figured out their Himmelbett operation, and the development of an airborne system became much more important.
In early 1941, Air Defense recognized the need for radar on their night-fighter aircraft. The requirements were given to Runge at Telefunken, and by the summer a prototype system was tested. Code-named Lichtenstein, this was a 62-cm (485-MHz), 1.5-kW system, generally based on the technology now well established by Telefunken for the Würzburg. The design problems were reduction in weight, provision of a good minimum range (very important for air-to-air combat), and an appropriate antenna design. An excellent minimum range of 200 m was achieved by carefully shaping the pulse. The antenna array had four dipoles with reflectors, giving a wide searching field and a typical 4-km maximum range (limited by ground clutter and dependent on altitude). A rotating phase-shifter was inserted in the transmission lines to produce a twirling beam. The elevation and azimuth of a target relative to the fighter were shown by corresponding positions on a CRT display.
The first production sets (Lichtenstein B/C) became available in February 1942, but were not accepted into combat until September. In general, pilots found a disadvantage to having this radar: it required large antennas that aerodynamically slowed the planes as much as 50 km/h. In May 1943, a B/C-equipped fighter aircraft landed in Scotland; it had flown the wrong way against a directional beacon. The British immediately recognized that they already had an excellent countermeasure in Window (the chaff used against the Würzburg); in a short time the B/C was greatly reduced in usefulness.
When the chaff problem was realized, it was decided to make the wavelength variable, allowing the operator to tune away from chaff returns. In mid-1943, the greatly improved Lichtenstein SN-2 was released, operating with a wavelength changeable between 3.7 to 4.1 m (81 to 73 MHz). The British took longer to find jamming for the SN-2, but this was eventually accomplished.
Although Telefunken had not been previously involved with radars of any type for fighter aircraft, in 1944 they started the conversion of a Marbach 10-cm set for this application. Downed American and British planes were scavenged for radar components; of special interest were the swiveling mechanisms used to scan the beam over the search area. An airborne set code-named Berlin was completed in January 1945, and about 40 sets were built and placed on night-fighter aircraft. A few sets, code named Berlin-S, were also built for shipboard surveillance.
In the years prior to World War II, Japan had knowledgeable researchers in the technologies necessary for radar they were especially advanced in magnetron development. Because, however, of a lack of appreciation of radar's potential and rivalry between army, navy and civilian research groups, Japan's development was slow. It was not until November 1941, just days before they entered the war with the United States
, that Japan placed into service its first full radar system. In August 1942, U.S. marines captured one of these first systems, and, although crude even by the standards of early U.S. radars, the fact the Japanese had any radar capability came as a surprise. Japanese radar technology was 3 to 5 years behind that of America, Great Britain, and Germany throughout the war.
A major leader in early technology development was Hidetsugu Yagi
, a professor and researcher of international status. His papers in the late 1920s on antennas and magnetron design were closely studied by scientists and engineers worldwide. He was allowed no part, however, in developing Japan's wartime radars. His earlier work was given so little attention by the Japanese military that, when they received a captured British radar set, at first they were unaware that the "Yagi
" mentioned in accompanying notes referred to a Japanese invention.
Although Japan had joined Nazi Germany
and Fascist Italy
in a Tripartite Pact
in 1936, there had been essentially no exchange of technical information. This changed in December 1940 when a group of Japanese representing Army technology was allowed to visit Germany, followed in January by a similar group from the Navy. In the visit, the Japanese were shown some German radars and a British MRU (their earliest searchlight-control radar), left behind during the Dunkirk evacuation. In addition, German-educated Yoji Ito
, leader of the Navy delegation, was able to obtain information from the host on the MRU's pulsed operation. Ito immediately sent this information home by diplomatic courier, and work was started by the Navy on Japan's first true radar.
After war was started with the United States in December 1941, the Germans shipped a Würzburg radar to Japan. The submarine carrying this equipment was sunk on the way, and a second set met the same fate; however, some key hardware and documentation, sent on a separate vessel, made it safely.
When Singapore
was taken in February 1942, the remains of what turned out to be a British GL Mk-2 radar and a Searchlight Control (SLC) radar were found. Along with the hardware, there was a set of hand-written notes, giving details of the theory and operation of the SLC. At Corregidor
the following May, the captors found two U.S. Army radars, an SCR-268 in operating condition and a heavily damaged SCR-270. In a rare cooperative effort, the Army and Navy jointly conducted reverse engineering
on these sets.
About 7,250 radar sets of 30 different types were developed for the Army and Navy. See List of Japanese World War II radar.
) and Nippon Electric Company (NEC
).
The TTRI established a system for designating the Army radar equipment, based on its use. The prefixes were Ta-Chi (written herein as Tachi) for land-based systems, Ta-Se for shipborne systems, and Ta-Ki for airborne systems. The "Ta" denoted Tama, the "Chi" was from tsuchi (earth), the "Se" means mizu (water) rapids, and "Ki" was from kuki (air).
In June 1942, both NEC and Toshiba started projects based on the SCR-268. The American system operated at 1.5 m (200 MHz). It had a very complex set of three antennas on a horizontal, rotatable boom and used lobe- switching. The NEC project was for a target-tracking system designated Tachi-1, essentially a copy of the SCR-268. The duplication of this system was found to be too difficult, and Tachi-1 was soon abandoned. At Toshiba, the project was also for a target-tracking system designated Tachi-2. This was to incorporate many simplifications to the SCR-268. Preliminary tests showed that it would be too fragile for field operation; this project was also abandoned.
The British GL Mk 2 was much less complicated than the SCR-268 and was easily reverse engineered; in addition, the notes on the SLC were available. From this came the Tachi-3, a ground-based tracking radar. This included many significant changes to the original British system; foremost were a change to a fixed-location configuration and a totally different antenna system.
The Tachi-3 transmitter operated at 3.75 m (80 MHz), and produced about 50-kW peak power, with 1- to 2-ms pulse width and 1- or 2-kHz PRF. The transmitter was designed for enclosure in an underground shelter. It used a Yagi antenna that was rigidly mounted above the shelter and the entire unit could be rotated in azimuth. By phasing the antenna elements, some elevation change could be attained.
The receiver for Tachi-3 was located in another underground shelter about 30-m distance from the transmitter. Four dipole antennas were mounted on orthogonal arms, and the shelter and antennas rotated to scan in azimuth. The maximum range was about 40 km. NEC built some 150 of these sets, and they finally entered service in early 1944.
The follow-on project at Toshiba was designated Tachi-4. This was for a ground-based tracking radar, again using the SCR-268 as a pattern. Still with the original 1.5 m (200 MHz) operation, this set performed reasonably well, and about 70 sets were produced. These began service in mid-1944; however, by then the Tachi-3 was available and was superior in performance.
Engineers at Toshiba had already begun work on a pulse-modulated system. With the arrival of the damaged SCR-270, portions were incorporated into the ongoing development of a fixed-site, early-warning system designated Tachi-6. The transmitter operated in the 3- to 4-m (100- to 75-MHz) band with a peak power of 50 kW. It used a dipole-array antenna atop a tall pole. Multiple receiver stations were spaced about 100 m around the transmitter. Each of these had a hand-rotated pole with Yagi antennas at two levels, allowing azimuth and elevation measurements. One receiver station could track an aircraft while the others were searching. Ranges up to 300 km were attained and shown on a CRT display. This went into service in early 1943; about 350 Tachi-6 systems were eventually built.
A transportable version of this early-warning system was added. Designated Tachi-7, the primary difference was that the transmitter with a folding antenna was on a pallet. About 60 of these were built. This was followed in 1944 with the Tachi-18, a much lighter, further simplified version that could be carried with troops. Several hundred of these "portable" sets were built, and a number were found as the Japanese vacated distant occupied territory. All of these continued to operate in the 3- to 4-m band.
Other land-based radars developed by the Imperial Army included two height-finder sets, Tachi-20 and Tachi-35, but they were too late to be put into service. There was also Tachi-28, a radar-based aircraft guidance set. The TTRI also developed the Tachi-24, their slightly modified version of the German Würzburg radar, but this was never put into production.
The Imperial Army had its own ships, ranging in size from attack motorboats to large landing crafts. For these, they developed Tase-1 and Tase-2, both anti-surface radars. The Imperial Army also had its own Air Divisions with fighters, bombers, transports, and reconnaissance aircraft. Only two systems were developed for these aircraft: Taki-1, an airborne surveillance radar in three models, and Taki-11, an airborne electronic countermeasures (ECM) set.
(Nippon Electric Company) and the Research Laboratory of NHK
(Japan Broadcasting Corporation), a prototype set was developed on a crash basis. Kenjiro Takayanagi
, Chief Engineer of NHK, developed the pulse-forming and timing circuits as well as the receiver display. The prototype was tested in early September.
The system, Japan's first full radar, was designated Mark 1 Model 1. (This type of designation is shortened herein to the numbers only; e.g., Type 11.) The system operated at 3.0 m (100 MHz) with a peak-power of 40 kW. Dipole arrays with mat-type reflectors were used in separate antennas for transmitting and receiving. In November 1941, the first manufactured Type 11 was placed into service as a land-based early-warning radar on the Pacific coast. A large system, it weighed close to 8,700 kg. Some 30 sets were built and used throughout the war. The detection range was about 130 km for single aircraft and 250 km for groups.
Type 12, another land-based early-warning system, followed during 1942. It was similar to its predecessor but lighter in weight (about 6,000 kg) and on a movable platform. Three versions were made; they operated at either 2.0 m (150 MHz) or 1.5 m (200 MHz), each with a peak-power of only 5 kW. The lower power significantly reduced the range. About 50 sets of all versions of these systems were built.
Another similar system was the Type 21. Fundamentally, it was the 200-MHz version of the Type 12 redesigned for shipboard use and weighing only about 840 kg. The first sets were installed on the battleships Ise and Hyuga in April 1942. About 40 sets were eventually built.
In this same time period, the more use-flexible Type 13 was also being designed. Operating at 2.0 m (150 MHz) and with a peak power of 10 kW, this set included a major advancement. A unit duplexer had been developed to allow the use of a common antenna. With a weight of 1,000 kg (a small fraction of that of the Type 11), this system could be readily used on shipboard as well as at land stations. Its detection range was about the same as the Type 12. It was placed into service in late 1942, and by 1944 it had also been adapted for use on surfaced submarines. With some 1,000 sets eventually being built, the Type 13 was by far the most used air- and surface-search radar of the Imperial Navy.
The Type 14 was a shipboard system designed for long-range, air-search applications. With a peak power of 100 kW and operating at 6 m (50 MHz), this weighed a huge 30,000 kg. Only two of these systems were placed in service in May 1945, just at the end of the war.
The Imperial Navy built two radars based on the captured SCR-268. The Type 41 was electronically like the original, but with two large dipole array antennas and configured for shipboard, fire-control applications. About 50 of these were built, and it went into service in August 1943. The Type 42 had more revisions, including a change to using four Yagi antennas. Some 60 were built and put into service in October 1944. Both systems had a range of about 40 km.
The NTRI made minimal changes to the 60-cm (500-MHz) Würzburg, mainly converting the oscillator from vacuum tubes to a magnetron. The result was the Type 23 anti-ship, fire-control radar intended for cruisers and larger ships. With the change to a magnetron, the output was approximately halved to a peak-power of about 5 kW; this gave a range of only 13 km for detecting most surface ships. Although the prototype was completed in March 1944, only a few sets were built, and it was never put into serial production.
Japan Radio Company
(JRC) had long worked with the NTRI in developing magnetrons. In early 1941, JRC was given a contract by NTRI to design and build a microwave surface-detection system for warships. Designated Type 22, this used a pulse-modulated, 10-cm (3.0-GHz) magnetron with water-cooling and producing 2-kW peak-power. The receiver was a super-heterodyne type with a low-power magnetron serving as the local oscillator. Separate horn antennas were used for transmitting and receiving. These were mounted on a common platform that could be rotated in the horizontal plane. Since it was Japan's first full set using a magnetron, Yoji Ito was made responsible and gave it special attention.
The prototype for the Type 22 was completed in October 1941; tests showed that it detected single aircraft at 17 km, groups of aircraft at 35 km, and surface ships at over 30 km (depending on the height of the antenna above the sea). The first Japanese warships with microwave radar received these in March 1942, and by late 1944, microwave radar was widely in use on surface vessels and submarines; about 300 Type 22 sets were built.
With the poor range of the Type 23 (the Würzburg copy), development was started on three microwave systems for fire-control applications. The Type 31 operated at 10 cm (3 GHz) and, like the Würzburg, used a common parabolic reflector. While the prototype could detect larger ships at up to 35 km, it was not completed until March 1945 and was never placed into production.
The Type 32 was another 10-cm system, this one having separate square-horn antennas. Detection range for large ships was about 30 km. It became operational in September 1944, and some 60 sets were produced. Type 33 was still another 10-cm set; this one used separate round-horn antennas. The prototype was completed in August 1944, but like the Type 23, detection range was only 13 km and it was not put into production.
The Imperial Navy had a large number of aircraft. It was almost a year after the start of the war, however, before the first airborne set was developed at the Oppama Naval Air Technical Depot (ONATD). Initially designated Type H-6 with a number of experimental sets built, this was eventually produced as the Type 64 and began service in August 1942. The greatest developmental problem was in bringing the weight down to that allowable for an aircraft; 110 kg was eventually achieved.
Intended for both air- and surface-search, the Type 64 operated at 2 m (150 MHz) with a peak power of 3 to 5 kW and a pulse width of 10 ms. It used a single Yagi antenna in the nose of the aircraft and dipoles on each side of the fuselage, and could detect large surface vessels or flights of planes at up to 100 km. This set was initially used on H8K-class 4-engine flying boats, then later on a variety of mid-sized attack planes and torpedo bombers. It was by far the most used airborne radar, with about 2,000 sets produced.
Development continued on lighter-weight systems at the ONATD. The Type N-6 weighing 60 kg was available in October 1944, but only 20 sets were built. This was a 1.2-m (250-MHz), 2-kW experimental set intended for a single-engine, 3-place (pilot, gunner, and radar operator) fighter aircraft. Another was the Type FM-3; operating at 2 m (150 MHz) with 2-kW peak-power, this weighed 60 kg and had a detection range up to 70 km. Specifically designed for the Kyūshū Q1W
Tokai, a new 2-engine 3-place anti-submarine aircraft, about 100 sets were built, going into service in January 1945.
With assistance from the NTRI and Yoji Ito, the ONATD also developed Japan's only airborne microwave radar. Designated FD-2 (sometimes FD-3), this was a magnetron-based, 25-cm (1.2-GHz), 2-kW set weighing about 70 kg. It could detect aircraft at a range between 0.6 and 3 km, satisfactory for close-range night-fighter aircraft such as the Nakajima J1N1-S
Gekko. It used four Yagi antennas mounted in the nose area; separate elements for transmit and receive were skewed for searching. Unlike in the air warfare in Europe, there were few night-fighter aircraft used by Japan; consequently, it was mid-1944 before the Type FD-2 was put into use. Some 100 sets were manufactured.
When magnetrons were being developed in Japan, the initial primary application was intended to be power transmission, not radar. As these devices increased in output energy, their application for a weapon became apparent. For research in special weapons, a large facility was built in Shimada. In 1943, a project in developing a Ku-go (Death Ray) using magnetrons began. By the end of the war, magnetrons developing 100 kW continuous power at 75 cm (400 MHz) had been built, and the intent was apparently to couple 10 of these to produce a beam of 1,000 kW. Essentially all of the equipment and documents at Shimada were destroyed before the Americans reached the facility.
s of Australia, Canada, New Zealand, and South Africa – and asked that they develop their own capabilities for indigenous systems. After Germany invaded Poland in September 1939, Great Britain and the Commonwealth Nations declared war with Germany. Within a short time, all four of the Commonwealth Nations had locally designed radar systems in operation, and most continued with developments throughout the war.
to consuct radar research. Led by John H. Piddington, their first project produced a shore-defense system, designated ShD, for the Australian Army
. This was followed by the AW Mark 1, an air-warning system for the Australian Air Force. These both operated at 200 MHz (1.5 m).
War on Japan began in December 1941, and Japanese planes attacked Darwin, Northern Territory
the following February. The New South Wales Railways Engineering Group was asked by the RPL to design a lightweight antenna for the air warning radar. From this, the LW/AW Mark II resulted; about 130 of these air-transportable sets were built and used by the United States and Australian military forces in the early island landings in the South Pacific, as well as by the British in Burma.
American troops arriving in Australia in 1942–43, brought many SCR-268 radar
systems with them. Most of these were turned over to the Australians, who rebuilt them to become Modified Air Warning Devices (MAWDs). These 200-MHz systems were deployed at 60 sites around Australia. During 1943–44, the RPL involved a staff of 300 persons working on 48 radar projects, many associated with improvements on the LW/AW. Height-finding was added (LW/AWH), and complex displays converted it into a ground-control intercept system (LW/GCI). There was also a unit for low-flying aircraft (LW/LFC). Near the end of the war in 1945, the RPL was working on a microwave height-finding system (LW/AWH Mark II).
(NRCC), specifically its Radio Branch headed by John Tasker Henderson
. Their first effort was in developing a surface-warning system for the Royal Canadian Navy
(RCN) to protect the Halifax Harbour
entrance. Called Night Watchman (NW), this 200-MHz (1.5-m), 1-kW set was completed in July 1940.
In September 1940, on their trip to the United States for cooperative exchanges, the Tizard Mission
visited Canada and recommended that Great Britain use Canadian personnel and facilities to supplement the British programs. Research Enterprises, Ltd. (REL), was then established to manufacture radar and optical equipment.
The next system was a ship-borne set designated Surface Warning 1st Canadian (SW1C) for corvettes and merchant ships The basic electronics were similar to the NW, but it initially used a Yagi antenna that was turned using an automobile steering wheel. It was first tested at sea in mid-May 1941. The project engineer from the NRCC was H. Ross Smith, who remained in charge of projects for the RCN throughout the war.
In early 1942, the frequency of the SW1C was changed to 215 MHz (1.4 m) and an electric drive was added to rotate the antenna. It was known as the SW2C and produced by the REL for corvettes and mine sweepers. A lighter version, designated SW3C, followed for small vessels such as motor torpedo boats. A plan-position indicator (PPI) display was added in 1943. Several hundred SW sets were eventually produced by the REL.
For coastal defense by the Canadian Army, a 200-MHz set with a transmitter similar to the NW was developed. Designated CD, it used a large, rotating antenna atop a 70-foot wooden tower. Since the firing battalion would be some distance away, a "displace corrector" automatically compensated for this separation. The CD was put into operation in January 1942
Following the Tizard Mission meetings in Washington, it was decided that Canada would build a microwave gun-laying system for the Canadian Army. This 10-cm (3-GHz) system was designated GL IIIC, the "C" to distinguish it from similar systems being developed in America ("A") and Great Britain "B"). (Eventually the U.S. system was the SCR-584.) A local source of magnetrons was vital, and the National Electric Company (NEC) in Montreal began manufacturing these devices.
The GL IIIC was housed in two trailers, one with a rotating cabin and one fixed. The rotating one was called the Accurate Position Finder and held the primary equipment and separate antennas with parabolic reflectors for transmitting and receiving. The other trailer carried the Zone Position Indicator, a 150-MHz (2-m) radar that found the position of all aircraft within the system's coverage.
In mid-1941, the REL received orders for 660 GL IIIC systems. In July, a very satisfactory demonstration of the prototype system was held, and by December, the first six systems had been built. During 1942 and into the next year, there were many technical and administrative problems Then in September 1943, a decision was made to use the British and American systems in liberating Europe; thus, the large REL order was never filled.
Success at the Radio Branch with the 10-cm experimental set for the Army led the RCN to request a ship-borne, early-warning microwave set. A separate Microwave Section was formed and development of a 10-cm (3-GHz) set designated RX/C was initiated in September 1941. Due to many changes in requirements from the RCN, the first sets were not available until July 1943. The RX/C incorporated many of the characteristics of the SW sets, but had a PPI display and a parabolic-reflector antenna. Further sets were produced by the REL and used throughout the war.
The Admiralty in Great Britain asked about Canada's interest and capability in manufacturing 3-cm magnetrons. This led to the development of a 3-cm device by the NEC and a full 3-cm (10-GHz) radar for small crafts. In May 1942, the British Admiralty gave a formal purchase order for these developments. The set was designated Type 268 (not to be confused with the SCR-268 from the U.S. Signal Corps), and was particularly designed to detect a submarine snorkel
. With extensive testing and subsequent changes, full-scale production did not start until December 1944. About 1,600 Type 268 sets were manufactured before the end of the war.
While the Canadian Army was basically satisfied with the 200-MHz CD systems, they did ask for an improvement to 10-cm operation. Since the Microwave Section was then well experienced in these systems, they easily provided a design. Before even a prototype was built, the Army gave an order to the REL for a number of sets designated CDX. Production started in February 1943, but only 19 sets were actually delivered with 5 of these going to the USSR,.
In the spring of 1943, German submarines started operating just outside the Saint Lawrence Seaway
– the primary ship route from Canada to Great Britain. To counter this, the Royal Canadian Air Force
(RCAF) asked that 12 sets of a long-range microwave system be built. A magnetron producing 300 kW at 10.7 cm (2.8 GHz) was developed by the firm NEC. For radiating a narrow horizontal beam to sweep the sea surface, a slotted antenna 32 by 8 feet in size was designed by William H. Watson at McGill University
. The system was designated MEW/AS (Microwave Early Warning Anti Submarine).
The transmitting and receiving equipment was located behind the antenna, and the assembly could be rotated at up to 6 RPM. The controls and PPI display was in a nearby fixed building. This could detect targets at up to 120-miles (196-km) range. A second version, designed for detecting high-flying aircraft, was designated MEW/HF (Height Finding). In this, the power could be switched to a smaller, rotating antenna that gave a narrow vertical beam. The RCAF put both versions of the MEW into operation at several sites in Newfoundland, Quebec, and Ontario.
In addition to the radar sets previously described, many others were designed at the NRCC's Radio Branch during the war years – a total of 30 of all types. Of these, 12 types were turned over to the REL where they were built in quantities varying from a few to hundreds; altogether, some 3,000 were produced before the REL was closed in September 1946.
, and the other, under the responsibility of Frederick White, was at Canterbury University College
in Christchurch
.
The objective of the Wellington group was to develop land-based and airborne RDF sets for detecting incoming vessels and a set to assist in gun-directing at coastal batteries. Within a few months, they had converted a 180-MHz (1.6-m), 1-kW transmitter from the Post Office to be pulse-modulated and used it in a system called CW (Coastal Watching). The CW was followed by a similar, improved system called CD (Coast Defense); it used a CRT for display and had lobe-switching on the receiving antenna. This was placed into service at the Devonport Naval Base
at Auckland
. In this same period, a partially completed ASV 200-MHz set from Great Britain was made into an airborne set for the Royal New Zealand Air Force
(RNZAF). About 20 sets were built and put into service. All three of these radars were placed into service before the end of 1940.
The group at Christchurch was to develop a set for shipboard detection of aircraft and other vessels, and a companion set for directing naval gunfire. This was a smaller staff and the work went much slower, but by July 1940, they had developed an experimental VHF fire-control set and tested it on the Armed Merchant Cruiser Monowai. This was then improved to become the 430 MHz (70 cm) SWG (Ship Warning, Gunnery), and in August 1941 went into service on the Archilles and Leander, Cruisers transferred to the newly formed Royal New Zealand Navy
(RNZN).
The same basic equipment was used by the Christchurch group in developing a ship-based air- and surface-warning system. The primary difference was that the SW antennas could be directed in elevation for aircraft detection. Designated SW (Ship Warning), it was usually installed together with the SWG. Eight of each type were eventually accepted by the RNZN. A number of SWGs were also built for the British fleet stationed in Singapore
; some of these with their manuals were captured by the Japanese in early 1942.
After sending engineers to the Rad Lab
in the United States to study their products, a project to develop mobile 10-cm (3-GHz) systems for coast-watching and surface-fire-control that might be used throughout the Pacific. With a great demand for such systems, an experimental unit was developed and tested before the end of 1942.
Designated ME, the electronics was mounted in the cabin of a 10-wheel truck and a second truck carried the power generator and workshop. Equipment was built in both Christchurch and Wellington. The radar had a single parabolic antenna was on the roof, and a plan-position indicator CRT was used, the first such in New Zealand. The first of these went into service in early 1943 in support of a U.S. torpedo-boat base in the Solomon Islands
. Some of the MD radars were used to replace 200-MHz CW sets, and several systems were built for operation on RNZN minesweepers.
As the Allies progressed upward in the Pacific, a need arose for a long-range warning set that could be quickly set up following an invasion. The RDL took this as a project in late 1942, and in few months six Long-Range Air Warning (LWAW) systems were available. These operated at 100 MHz (3 m) and, like the microwave sets, were mounted in trucks. A single Yagi antenna was normally used, but there was also a broadside array that could be used when a more permanent operation was established. The range using the Yagi was near 150 km; this increased to over 200 km with the broadside.
From the start in late 1939, 117 radar sets of all types were built in New Zealand, all by small groups; no types were ever put into serial production. After 1943, little such equipment was produced in the country, and RNZN warships were then provided with British outfits to replace the earlier New Zealand sets.
in Johannesburg
. When Prime Minister Jan Smuts
was told of this new technology, he requested that the resources of BPI be devoted to this effort for the duration of the war. Basil Schonland
, a world-recognized authority on lightning detection and analysis, was appointed to head the effort.
With nothing more than copies of some "vague documents" and notes provided by New Zealand’s representative at the briefings in England, Schonland and a small team started the development in late September 1939. Before the end of November the various elements of the system were completed, all by using locally available components. These were assembled in separate vehicles for the transmitter and receiver.
The transmitter operated at 90 MHz (3.3 m) and had a power of about 500 W. The pulse was 20-μs in width and the PRF was 50 Hz, synchronized with the power-line. The receiver was super-regenerative, using type 955 and 956 Acorn tubes in the front end and a 9-MHz IF amplifier. Separate, rotatable antennas with stacked pairs of full-wave dipoles were used for transmitting and receiving. The beams were about 30 degrees wide, but the azimuth of the reflected signal was determined more precisely by using a goniometer
. Pulses were displayed on the CRT of a commercial oscilloscope.
Before the end of the year, a full system had been assembled and detected a water tank at a distance of about 8 km. Improvements were made on the receiver, and the transmitter pulse-power was increased to 5 kW. Designated JB-1 (for Johannesburg), the prototype system was taken to near Durban
on the coast for operational testing. There it detected ships on the Indian Ocean
, as well as aircraft at ranges to 80 km.
In early March 1940, the first JB-1 system was deployed to Mambrui
on the coast of Kenya
, assisting an anti-aircraft Brigade in intercepting attacking Italian bombers, tracking them up to 120 kilometres (74.6 mi). During early 1941, six systems were deployed to East Africa
and Egypt
; JB systems were also placed at the four main South African ports.
An improved system, designated JB-3, was built at the BPI; the most important changes were the use of a transmit-receive device (a duplexer) allowing a common antenna, and an increase in frequency to 120 MHz (2.5 m). The range increased to 150 km for aircraft and 30 km for small ships, with a bearing accuracy of 1–2 degrees. Twelve sets of JB-3 radars began deployment around the South African coast in June 1941.
By mid-1942, British radars were available to need all new South African needs. Thus, no further developments were made at the BPI. Most of the staff joined the military. Basil Schonland, as a Lt. Colonel in the South African Army
, went to Great Britain to serve as Superintendent of the Army Operational Research Group and later the scientific advisor to Field Marshal Bernard Montgomery.
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...
and Axis powers
Axis Powers
The Axis powers , also known as the Axis alliance, Axis nations, Axis countries, or just the Axis, was an alignment of great powers during the mid-20th century that fought World War II against the Allies. It began in 1936 with treaties of friendship between Germany and Italy and between Germany and...
used radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
in 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 many important aspects of this conflict were greatly influenced by this revolutionarily new technology.
The basic technology of radio-based detection and tracking evolved independently and with great secrecy in a number of nations during the second half of the 1930s. At the start of the war in Europe in September 1939, both Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
had begun the deployment of these systems. In Great Britain this technology was called RDF, standing for Range and Direction Finding
Range and Direction Finding
Range and Direction Finding was the initial technique and hardware in Great Britain that eventually came to be called 'radar.'Since the earliest days of radio , the signals had been used in direction finding on land, sea, and in the air...
, while in Germany the name Funkmessgerät (radio measuring device) was often used.
By the time of 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...
in mid-1940, the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
(RAF) had incorporated RDF stations as vital elements in Britain's air-defence capabilities. The German Funkmessgerät, could not assist in Germany's offensive capability and was thus not supported by Adolf Hitler
Adolf Hitler
Adolf Hitler was an Austrian-born German politician and the leader of the National Socialist German Workers Party , commonly referred to as the Nazi Party). He was Chancellor of Germany from 1933 to 1945, and head of state from 1934 to 1945...
. Also, the Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
(German Air Force) did not sufficiently appreciate the importance of RDF stations in air defence, contributing to Germany's lack of success in this early stage of the war.
Although the technology was first demonstrated in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
during December 1934, it was only when war clouds loomed that the U.S. military authorities recognized the great potential of radio-based detection and tracking, and began the development of ship- and land-based systems. The first of these were fielded by the U.S. Navy in early 1940, and a year later by the U.S. Army. The acronym RADAR (for RAdio Detection And Ranging) was coined by the U.S. Navy in 1940, and the subsequent name "radar" was soon widely used.
While the great benefits of operating in the 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...
portion of the radio spectrum
Radio spectrum
Radio spectrum refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz ....
were known, transmitters for generating microwave signals of sufficient power were not available; thus, all early radar systems operated at much lower frequencies. In February 1940, researchers in Great Britain developed the resonant-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...
, capable of producing microwave power in the kilowatt range, opening the path to second-generation radar systems.
As the conflict in Europe got underway, it was realised in Great Britain that the development and manufacturing capabilities of the United States were vital to success in the war; thus, although America was not yet a direct participant in the war, Prime Minister Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
directed that the technology secrets of Great Britain be shared with this nation in exchange for the needed capabilities. In the summer of 1940, 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...
brought these secrets to the United States. The cavity magnetron was included, and almost immediately 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...
was established to develop microwave radars using the magnetron.
In addition to Great Britain, Germany, and the United States, wartime radars were also developed and used by the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, as well as the technically advanced Commonwealth Nations
Commonwealth of Nations
The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...
Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, and South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. These developments and the resulting systems are also described herein. The Wikipedia article History of Radar
History of radar
The history of radar starts with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects. This possibility was suggested in James Clerk Maxwell's seminal work on electromagnetism...
provides a summary of pre-war developments in all of these countries as well as early activities in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, and Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
.
United Kingdom
Research leading to the RDF technology in the United Kingdom had been initiated by Sir Henry TizardHenry Tizard
Sir Henry Thomas Tizard FRS was an English chemist and inventor and past Rector of Imperial College....
's Aeronautical Research Committee
Aeronautical Research Committee
The Aeronautical Research Committee was a UK government committee established in 1919 in order to coordinate aeronautical research and education following World War I...
in early 1935, responding to the urgent need to protect Great Britain from German bomber attacks. Robert A. 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...
at the Radio Research Station, Slough, was asked to comment on the feasibility of a radio-based "death ray". In response, Watson-Watt and his scientific assistant, Arnold F. Wilkins
Arnold Frederic Wilkins
Arnold Frederic Wilkins O.B.E., was a pioneer in developing the use of radar.-Early life:...
, replied that a more fruitful activity would be in using radio to detect and track enemy aircraft. On February 26, 1935, a preliminary test, commonly called the Daventry Experiment, showed that radio signals reflected from an aircraft could be detected. Research funds were quickly allocated, and a development project was started in great secrecy on the Orford Ness
Orford Ness
Orford Ness is a cuspate foreland shingle spit on the Suffolk coast in Great Britain, linked to the mainland at Aldeburgh and stretching along the coast to Orford and down to North Wier Point, opposite Shingle Street. It is divided from the mainland by the River Alde, and was formed by longshore...
Peninsula in Suffolk
Suffolk
Suffolk is a non-metropolitan county of historic origin in East Anglia, England. It has borders with Norfolk to the north, Cambridgeshire to the west and Essex to the south. The North Sea lies to the east...
on the coast of the North Sea. E. G. Bowen was responsible for developing the pulsed transmitter. On June 17, 1935, the research apparatus successfully detected an aircraft at a distance of 17 miles. In August, A. P. Rowe
Albert Percival Rowe
Albert Percival Rowe was a British physicist and senior research administrator who had a major role in the development of Radar before and during World War II....
, representing the Tizard Committee, suggested the technology be code-named RDF, meaning Range and Direction Finding
Range and Direction Finding
Range and Direction Finding was the initial technique and hardware in Great Britain that eventually came to be called 'radar.'Since the earliest days of radio , the signals had been used in direction finding on land, sea, and in the air...
.
Air Ministry
In March 1936, the RDF research and development effort was moved to the Bawdsey Research Station located at Bawdsey ManorBawdsey Manor
Bawdsey Manor stands at a prominent position at the mouth of the River Deben close to the village of Bawdsey in Suffolk, England, about 118 km northeast of London....
in Suffolk
Suffolk
Suffolk is a non-metropolitan county of historic origin in East Anglia, England. It has borders with Norfolk to the north, Cambridgeshire to the west and Essex to the south. The North Sea lies to the east...
. While this operation was under the Air Ministry, both the Army and Navy became involved and soon initiated their own programs.
At Bawdsey, outstanding engineers and scientists evolved the RDF technology, but much of the credit belongs to Watson-Watt, the head of the team, who turned from the technical side to building up a usable network of machines and the people to run them. After watching a demonstration in which his equipment operators were attempting to locate an "attacking" bomber, he noticed that the primary problem was not technological, but worker overload. Following Watson-Watt's advice, by early 1940 the RAF had built up a layered control organization that efficiently passed information along the chain of command, and was able to track large numbers of aircraft and direct defences to them.
Immediately after the war began in September 1939, the Air Ministry RDF development at Bawdsey was temporarily relocated to University College, Dundee
University of Dundee
The University of Dundee is a university based in the city and Royal burgh of Dundee on eastern coast of the central Lowlands of Scotland and with a small number of institutions elsewhere....
in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. A year later, the operation moved to near Worth Matravers
Worth Matravers
Worth Matravers is a village and civil parish in the English county of Dorset. The village is situated on the cliffs west of Swanage. It comprises limestone cottages and farm houses and is built around a pond, which is a regular feature on postcards of the Isle of Purbeck.The civil parish stretches...
in Dorset
Dorset
Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...
on the southern coast of England, and was named the Telecommunications Research Establishment
Telecommunications Research Establishment
The Telecommunications Research Establishment was the main United Kingdom research and development organization for radio navigation, radar, infra-red detection for heat seeking missiles, and related work for the Royal Air Force during World War II and the years that followed. The name was...
(TRE). In a final wartime move, the TRE relocated to Malvern College
Malvern College
Malvern College is a coeducational independent school located on a 250 acre campus near the town centre of Malvern, Worcestershire in England. Founded on 25 January 1865, until 1992, the College was a secondary school for boys aged 13 to 18...
in Great Malvern
Great Malvern
Great Malvern is an area of Malvern, Worcestershire, England. It is the historical centre of the town, and the location of the headquarters buildings of the of Malvern Town Council, the governing body of the Malvern civil parish, and Malvern Hills District council of the county of...
, near Birmingham
Birmingham
Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...
.
Some of the major RDF/radar equipment used by the Air Ministry is briefly described. All of the systems were given the official designation Air Ministry Experimental Station
Air Ministry Experimental Station
AMES or Air Ministry Experimental Station was the way of identifying RAF radar types during and after World War II*AMES Type 1, Chain Home - Early Warning*AMES Type 2, Chain Home Low - Early Warning, LOW altitude...
(AMES) plus a Type number; most of these are listed in this link.
Chain Home
Shortly before the outbreak of World War II, several RDF (radar) stations known as Chain HomeChain 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...
(or CH) were constructed along the South and East coasts of Britain, based on the successful model at Bawdsey. As one might expect from the first equipment to be deployed, CH was a simple system. The broadcast side was formed from two 300-ft (90-m) tall steel towers strung with a series of antennas between them. A second set of 240-ft (73-m) tall wooden towers were used for reception, with a series of crossed antennas at various heights up to 215 ft (65 m). Most stations had more than one set of each antenna, tuned to operate at different frequencies.
Typical CH operating conditions were:
- Frequency: 20 to 30 megahertz (MHz) (15 to 10 metres)
- Peak power: 350 kilowatt (kW) (later 750 kW)
- Pulse repetition frequencyPulse repetition frequencyPulse repetition frequency or Pulse repetition rate is the number of pulses per time unit . It is a measure or specification mostly used within various technical disciplines Pulse repetition frequency (PRF) or Pulse repetition rate (PRR) is the number of pulses per time unit (e.g. Seconds). It...
: 25 and 12.5 pps - Pulse length: 20 microseconds (μs)
The CH output was read with an oscilloscope
Oscilloscope
An oscilloscope is a type of electronic test instrument that allows observation of constantly varying signal voltages, usually as a two-dimensional graph of one or more electrical potential differences using the vertical or 'Y' axis, plotted as a function of time,...
. When a pulse was sent out into the broadcast towers, the scope was triggered to start its beam moving horizontally across the screen very rapidly. The output from the receiver was amplified
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
and fed into the vertical axis of the scope, so a return from an aircraft would deflect the beam upward. This formed a spike on the display, and the distance from the left side – measured with a small scale on the bottom of the screen – would give the distance to the target. By rotating the receiver goniometer
Goniometer
A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry is derived from two Greek words, gōnia, meaning angle, and metron, meaning measure....
connected to the antennas to make the display disappear, the operator could determine the direction to the target (this was the reason for the cross shaped antennas), while the size of the vertical displacement indicated something of the number of aircraft involved. By comparing the strengths returned from the various antennas up the tower, the altitude could be determined to some degree of accuracy.
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...
, and is often credited with enabling the RAF to defeat the much larger Luftwaffe forces. Whereas the Luftwaffe had to hunt all over to find the RAF fighters, the RAF knew exactly where the German bombers were, and could converge all of their fighters on them. In modern terminology, CH was a force multiplier, allowing the RAF fighters to operate more effectively as if they were a much larger force operating at the same effectiveness as the Germans. In addition, the CH system allowed pilots to rest on the ground instead of flying continuous "standing patrols", and only needing to "scramble" (take off) when the air threat was imminent. This not only reduced pilots' workloads, but also reduced wear on engines, as well as reducing unnecessary petrol
Avgas
Avgas is an aviation fuel used to power piston-engine aircraft. Avgas is distinguished from mogas , which is the everyday gasoline used in cars and some non-commercial light aircraft...
consumption.
Very early in the battle the Luftwaffe made a series of small raids on a few of the stations, including the Bawdsey research and training station, but they were returned to operation in a few days. In the meantime the operators took to broadcasting radar-like signals from other systems in order to fool the Germans into believing that the systems were still operating. Eventually the Germans gave up trying to bomb them. The German High Command
Oberkommando der Wehrmacht
The Oberkommando der Wehrmacht was part of the command structure of the armed forces of Nazi Germany during World War II.- Genesis :...
apparently never understood the importance of radar to the RAF's efforts, or they would have assigned these stations a much higher priority – even a concerted effort would not have had much effect on the transmitters as their structure made them very resistant to blast, which passed through the spaces in the metal lattice.
Chain Home Low
Chain Home Low was the name of a British radar early warning system, detecting enemy aircraft movement at lower altitudes than and summarily used with the fixed Chain Home system which was operated by the RAF during World War II...
(CHL). These systems had originally been intended to use for naval gun-laying and known as Coastal Defence (CD), but their narrow beams also meant they could sweep an area much closer to the ground without seeing the reflection of the ground (or water) – known as clutter
Clutter (radar)
Clutter is a term used for unwanted echoes in electronic systems, particularly in reference to radars. Such echoes are typically returned from ground, sea, rain, animals/insects, chaff and atmospheric turbulences, and can cause serious performance issues with radar systems.- Backscatter coefficient...
. Unlike the larger CH systems, CHL had to have the broadcast antenna itself turned, as opposed to just the receiver. This was done manually on a pedal-crank system run by Women's Auxiliary Air Force
Women's Auxiliary Air Force
The Women's Auxiliary Air Force , whose members were invariably referred to as Waafs , was the female auxiliary of the Royal Air Force during World War II, established in 1939. At its peak strength, in 1943, WAAF numbers exceeded 180,000, with over 2,000 women enlisting per week.A Women's Royal Air...
until more reliable motorized movements were installed in 1941.
Ground-Controlled Intercept
Systems similar to CH were later adapted with a new displayCathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
to produce the Ground-Controlled Intercept
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) stations in January 1941. In these systems the antenna was rotated mechanically, followed by the display on the operator's console. That is, instead of a single line across the bottom of the display from left to right, the line was rotated around the screen at the same speed as the antenna was turning.
The result was a 2-D display of the air space around the station with the operator in the middle, with all the aircraft appearing as dots in the proper location in space. Called 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...
s (PPI), these dramatically simplified the amount of work needed to track a target on the operator's part. Such a system with a rotating, or sweeping, line is what most people continue to associate with a radar display. Philo Taylor Farnsworth, the American inventor of all-electronic television in 1927, contributed to this in an important way. Farnsworth refined a version of his picture tube (cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
, or CRT) and called it an "Iatron". It could store an image for milliseconds to minutes (even hours). One version that kept an image alive about a second before fading, proved to be a useful addition to the evolution of radar. This slow-to-fade display tube was used by air traffic controllers from the very beginning of radar.
Airborne Intercept
Rather than avoid the radars, the Luftwaffe took to avoiding the fighters by flying at night and in bad weather. Although the RAF control stations were aware of the location of the bombers, there was little they could do about them unless the fighter pilots could see the opposing planes.This eventuality had already been foreseen, and a successful programme by Edward George Bowen
Edward George Bowen
Edward George 'Taffy' Bowen, CBE, FRS was a British physicist who made a major contribution to the development of radar, and so helped win both the Battle of Britain and the Battle of the Atlantic...
starting in 1936 (likely at the urging of Tizard) developed a miniaturized RDF system suitable for aircraft, the Air Interception (AI) set. (Watson-Watt called the CH sets the RDF-1 and the AI the RDF-2A.) At the same time Bowen developed AI sets for aircraft to detect submarines, the Air to Surface Vessel (ASV) set was also developed, making a significant contribution to the defeat of the German U-boats.
Initial AI sets were available in 1939 and fitted to Bristol Blenheim
Bristol Blenheim
The Bristol Blenheim was a British light bomber aircraft designed and built by the Bristol Aeroplane Company that was used extensively in the early days of the Second World War. It was adapted as an interim long-range and night fighter, pending the availability of the Beaufighter...
aircraft, replaced quickly with the better-performing Bristol Beaufighter
Bristol Beaufighter
The Bristol Type 156 Beaufighter, often referred to as simply the Beau, was a British long-range heavy fighter modification of the Bristol Aeroplane Company's earlier Beaufort torpedo bomber design...
. These quickly put an end to German night- and bad-weather bombing over Britain. Mosquito
De Havilland Mosquito
The de Havilland DH.98 Mosquito was a British multi-role combat aircraft that served during the Second World War and the postwar era. It was known affectionately as the "Mossie" to its crews and was also nicknamed "The Wooden Wonder"...
night intruders were fitted with AI Mk VIII and later derivatives, which, along with a device called "Serrate
Serrate radar detector
Serrate was an Allied radar detection and homing device, used in Allied nightfighters to track German night fighters equipped with the earlier UHF-band BC and C-1 versions of the Lichtenstein radar during World War II....
" to allow them to track down German night fighters from their Lichtenstein
Lichtenstein radar
Lichtenstein radar was a German airborne radar in use during World War II. It was available in at least four major revisions, the FuG 202 Lichtenstein B/C, FuG 212 Lichtenstein C-1, FuG 220 Lichtenstein SN-2 and FuG 228 Lichtenstein SN-3.- FuG 202 Lichtenstein B/C :Early FuG 202 Lichtenstein B/C...
signal emissions, as well as a device named "Perfectos" that tracked German IFF
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...
, allowed the Mosquito to find and destroy German night fighters. As a countermeasure the German night fighters employed Naxos ZR
Naxos radar detector
The FuG 350 Naxos radar warning receiver was a World War II German countermeasure to SHF band centimetric wavelength radar produced by a cavity magnetron...
signal detectors.
Centimetric
The next major development in the history of radar was the invention of the cavity magnetron by John Randall and Harry BootHarry Boot
Henry Albert Howard "Harry" Boot was an English physicist who with Sir John Randall and James Sayers developed the cavity magnetron, which was one of the keys to the Allied victory in the Second World War.-Biography:...
of Birmingham University in early 1940. This was a small device that generated 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...
frequencies much more efficiently than previous devices, allowing the development of practical centimetric
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
radar, operating in the radio frequency band from 3 to 30 GHz. Centimetric radar allowed for the detection of much smaller objects and the use of much smaller antennas
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
than the earlier lower frequency sets.
The cavity magnetron was perhaps the single most important invention in the history of radar and played a major part in the Allies' victory. In 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...
during September 1940, it was given free to the U.S., together with several other inventions such as jet technology, so that the British could use American R&D and production facilities. The British need to produce the magnetron in large quantities was great. Consequently, Edward George Bowen
Edward George Bowen
Edward George 'Taffy' Bowen, CBE, FRS was a British physicist who made a major contribution to the development of radar, and so helped win both the Battle of Britain and the Battle of the Atlantic...
was sent as the RDF expert in the Tizard Mission to the U.S. This led to the creation of 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...
(Rad Lab) at MIT
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
to further develop the device and its applications. Half of the radar deployed during World War II were designed at the Rad Lab, including over 100 different systems costing $1.5 billion.
When the cavity magnetron was first developed, its use in microwave RDF sets was held up because the duplexers for VHF were destroyed by the new higher-powered transmitter. This critical problem was solved in early 1941 by the T-R switch developed at the Clarendon Laboratory
Clarendon Laboratory
The Clarendon Laboratory, located on Parks Road with the Science Area in Oxford, England , is part of the Physics Department at Oxford University...
of Oxford University, allowing a pulse transmitter and receiver to share the same antenna without destabilizing the sensitive receiver.
The combination of the magnetron, the T-R switch, small antennas and high resolution allowed small high quality radars to be installed in aircraft. They could be used by maritime patrol
Maritime patrol
Maritime patrol is the task of monitoring areas of water. Generally conducted by military and law enforcement agencies, maritime patrol is usually aimed at identifying human activities....
aircraft to detect objects as small as a submarine periscope
Periscope
A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....
, which allowed aircraft to attack and destroy submerged submarines, which had previously been undetectable from the air. Centimetric contour mapping
Topographic map
A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features...
radars like H2S
H2S radar
H2S was the first airborne, ground scanning radar system. It was developed in Britain in World War II for the Royal Air Force and was used in various RAF bomber aircraft from 1943 to the 1990s. It was designed to identify targets on the ground for night and all-weather bombing...
improved the accuracy of Allied bombers used in the strategic bombing campaign
Strategic bombing during World War II
Strategic bombing during World War II is a term which refers to all aerial bombardment of a strategic nature between 1939 and 1945 involving any nations engaged in World War II...
. Centimetric gun laying radars were much more accurate than the older technology. They made the big gunned Allied battleships more deadly and along with the newly developed proximity fuze
Proximity fuze
A proximity fuze is a fuze that is designed to detonate an explosive device automatically when the distance to target becomes smaller than a predetermined value or when the target passes through a given plane...
made anti-aircraft guns much more dangerous to attacking aircraft. The two coupled together and used by anti-aircraft batteries, placed along on the 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....
flight paths to London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, are credited with destroying many of the flying bombs before they reached their target.
British Army
At the time that the Air Ministry had its RDF development center in Bawdsey, an Army Cell was attached to initiate its own programs. These programs were for a Gun Laying (GL) system to in assist aiming antiaircraft guns and searchlights and a Coastal Defense (CD) system for directing coastal artillery. It is noted that the Army Cell staff included W. A. S. Butement and P. E. Pollard who, in 1930, demonstrated a radio-based detection apparatus that for unknown reasons was not further pursued by the Army.When the war started and the Air Ministry activities were relocated to Dundee in Scotland, the Army Cell became a part of a new developmental center at Christchurch
Christchurch
Christchurch is the largest city in the South Island of New Zealand, and the country's second-largest urban area after Auckland. It lies one third of the way down the South Island's east coast, just north of Banks Peninsula which itself, since 2006, lies within the formal limits of...
in Dorset
Dorset
Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...
on the south coast. John D. Cockcroft
John Cockcroft
Sir John Douglas Cockcroft OM KCB CBE FRS was a British physicist. He shared the Nobel Prize in Physics for splitting the atomic nucleus with Ernest Walton, and was instrumental in the development of nuclear power....
a physicist from Cambridge University and later a Nobel Prize Laureate, became the Director. With enlarged activities, the facility became the Air Defence Research and Development Establishment (ADRDE) in mid-1941. A year later, the ADRDE relocated to Great Malvern
Great Malvern
Great Malvern is an area of Malvern, Worcestershire, England. It is the historical centre of the town, and the location of the headquarters buildings of the of Malvern Town Council, the governing body of the Malvern civil parish, and Malvern Hills District council of the county of...
, in Worcestershire
Worcestershire
Worcestershire is a non-metropolitan county, established in antiquity, located in the West Midlands region of England. For Eurostat purposes it is a NUTS 3 region and is one of three counties that comprise the "Herefordshire, Worcestershire and Warwickshire" NUTS 2 region...
near Birmingham
Birmingham
Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...
. In 1944, this was reorganized as the Radar Research and Development Establishment (RRDE).
Transportable Radio Unit
While at Bawdsey, the Army Cell developed a GL system code-named Transportable Radio Unit (TRU). Pollard was the project leader. Operating at 60 MHz (6-m) with 50-kW power, the TRU had two vans for the electronic equipment plus a power van; it used a 105-ft erectable tower to support a transmitting antenna and two receiving antennas. A prototype was successfully tested in October 1937, detecting aircraft at 60-miles range; production of 400 sets designated GL Mk I started the following June. The Air Ministry adopted some of these sets as gap-fillers and emergency substitutes in the CH network.As the war started, GL Mk I sets were used overseas by the British Army in Malta
Malta
Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...
and Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
in 1939–40. Seventeen sets were sent to France with the British Expeditionary Force
British Expeditionary Force (World War II)
The British Expeditionary Force was the British force in Europe from 1939–1940 during the Second World War. Commanded by General Lord Gort, the BEF constituted one-tenth of the defending Allied force....
; most of these were destroyed at the Dunkirk evacuation in late May 1940, but a few were captured and gave the Germans their first full information on British RDF hardware. An improved version, GL Mk II, was used throughout the war; some 1,700 sets were put into service, including over 200 supplied to the Soviet Union. Operational research found that anti-aircraft batteries using the GL averaged 4,100 rounds fired per hit, compared with about 20,000 rounds for unassisted guns.
Coastal Defense
In early 1938, Alan ButementW. A. S. Butement
William Alan Stewart Butement , was a defence scientist and public servant. A native of New Zealand, he made extensive contributions to radar development in Great Britain during World War II, served as the first chief scientist for the Australian Defence Scientific Service, then ended his...
began the development of a Coastal Defense (CD) system that involved some of the most significant advancements in the early history of radar. The 200-MHz transmitter and receiver already being developed for the AI and ASV sets of the Air Defense were used as starters, but, since the CD would not be airborne, more power and a much larger antenna were possible. The transmitter power was increased to 150 kW. A huge dipole
Dipole antenna
A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other , with a small space between them. The radio frequency voltage is applied to the antenna at...
array, 10-ft high and 24-ft wide, was developed, giving much narrower beams and higher gain. This "broadside" array
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
was rotated 1.5 revolutions per minute, sweeping a field covering 360 degrees. 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...
was incorporated in the transmitting array, giving higher directional accuracy. For analysis of the system, Butement formulated the first – at least in Great Britain – mathematical relationship that would later become the well-known "radar range equation".
Early tests showed that the CD set had much better capabilities for detecting aircraft at low altitudes than the existing CH. Consequently, the CD was also adopted by the Air Defense to augment the CH stations; in this role it was designated the Chain Home Low
Chain Home Low
Chain Home Low was the name of a British radar early warning system, detecting enemy aircraft movement at lower altitudes than and summarily used with the fixed Chain Home system which was operated by the RAF during World War II...
(CHL).
Centimetric Gun-Laying
When the cavity magnetron came into being, the ADEE asked for and received assistance from the TRE in using this device in an experimental 20-cm GL set. This was first tested and found to be unsatisfactory for the harsh environment of Army field equipment. When the ADEE became the ADRDE in early 1941, this organization started the development of the GL3B. All of the equipment, including the power generator, was contained in a ruggedized trailer, topped with two 6-ft dish transmitting and receiving antennas on a rotating base (the T-R switch allowing a common antenna had not yet been developed.) Similar microwave GL systems were being developed in Canada (the GL3C) and in America (eventually designated SCR-584). Although about 400 of the GL3B sets were manufactured, it was the American version that dominated in the defense of London during the V-1 and V-2 attacks.Royal Navy
Representatives of the Experimental Department of His Majesty's Signal School (HMSS) had been invited to demonstrations of the equipment being developed by the Air Ministry at Orfordness and Bawdsey Manor. Located at PortsmouthPortsmouth
Portsmouth is the second largest city in the ceremonial county of Hampshire on the south coast of England. Portsmouth is notable for being the United Kingdom's only island city; it is located mainly on Portsea Island...
in Hampshire
Hampshire
Hampshire is a county on the southern coast of England in the United Kingdom. The county town of Hampshire is Winchester, a historic cathedral city that was once the capital of England. Hampshire is notable for housing the original birthplaces of the Royal Navy, British Army, and Royal Air Force...
, the Experimental Department had an excellent capability for developing wireless valves (vacuum tubes), and, in fact, had provided the tubes used by Bowden in the initial transmitter at Orford Ness. With excellent research facilities of its own, the Admiralty decided to have its RDF development at the HMSS. This remained in Portsmouth after the start of the war, but in 1942, it was moved inland to safer locations at Witley
Witley
Witley, in Surrey, England is a village south west of Godalming. The village lies just east of the A3 that runs from Guildford to Petersfield. Witley together with the neighbouring area of Hambledon have a population of about 4,000. Neighbouring villages include Milford, Chiddingfold and...
and Haslemere
Haslemere
Haslemere is a town in Surrey, England, close to the border with both Hampshire and West Sussex. The major road between London and Portsmouth, the A3, lies to the west, and a branch of the River Wey to the south. Haslemere is approximately south-west of Guildford.Haslemere is surrounded by hills,...
, both in a county in the South East of England named Surrey
Surrey
Surrey is a county in the South East of England and is one of the Home Counties. The county borders Greater London, Kent, East Sussex, West Sussex, Hampshire and Berkshire. The historic county town is Guildford. Surrey County Council sits at Kingston upon Thames, although this has been part of...
. These two operations became the Admiralty Signal Establishment (ASE).
A few representative radars are described. Note that the type numbers are not sequential by date.
Surface Warning/Gun Control
The Royal Navy's first successful RDF was the Type 79Y Surface Warning, tested at sea in early 1938. John D. S. Rawlinson was the project director. This 43-MHz (7-m), 70-kW set used fixed transmitting and receiving antennas and had a range of 30 to 50 miles, depending on the antenna heights. By 1940, this became the Type 281, increased in frequency to 85 MHz (3.5 m) and power to between 350 and 1,000 kW, depending on the pulse width. With steerable antennas, it was also used for Gun Control. This was first used in combat on 17 March 1941, allowing the British Royal Navy to essentially annihilate the Regia MarinaRegia Marina
The Regia Marina dates from the proclamation of the Kingdom of Italy in 1861 after Italian unification...
(Royal Italian Navy) off the coast of Greece. Type 281B was a modification to use a common transmitting and receiving antenna. The Type 281, including the B-version, was likely the most used metric system of the Royal Navy throughout the war.
Air Search/Gunnery Director
In early 1938, John F. Coales initiated the development of 600-MHz (50-cm) equipment. The higher frequency allowed narrower beams (needed for air search) and antennas more suitable for shipboard use. The first 50-cm set was Type 282. With 25-kW output and a pair of Yagi arrays incorporating lobe-switching, this was first given sea trials in June 1939. This set detected low-flying aircraft at 2.5 miles and ships at twice this range. In early 1940, 200 sets were put into production. To use the Type 282 as a rangefinder for the main armament, an antenna with a large cylindrical parabolic reflector and 12 dipoles was used. This set was designated Type 285 and could follow a vessel to about 15 miles. Types 282 and Type 285 were particularly used with Bofors 40 mm guns. Type 283 and Type 284 were other 50-cm gunnery director systems.Microwave Warning/Fire Control
The detection of submarines, an urgent problem of the Royal Navy, required RDF systems operating at higher frequencies than the existing sets. When the first cavity magnetron was delivered to the TRE, a demonstration breadboard was built and demonstrated to the Admiralty. In early November 1940, a team from Portsmouth under S. E. A. Landale was set up at the TRE to develop a 10-cm surface-warning set for shipboard use. Before the end of the year, an experimental apparatus was tested against a submarine and tracked it at 13 miles. Returning to Portsmouth, the team continued the development of a full system, incorporating antennas behind cylindrical parabolas (called "cheese" antennas) to generate a narrow, fan-shaped beam that maintained target illumination as the shipped rolled. Designated Type 271, the set was tested at sea in March 1941, detecting the extended periscope of a submerged submarine at almost a mile. The set became operational in August 1941, just 12 months after the first apparatus was demonstrated. On November 16, the first German submarine was sunk after being detected by a Type 271 system.The initial Type 271 primarily found service on smaller vessels. At ASE Witley, this set was modified to become Type 272 and Type 273 for larger vessels. With larger reflectors, the Type 273 also served well as air-warning against low-flying aircraft, with a range up to 30 miles. A close relative was the Type 277, a "nodding" 10-cm height-finding system. The "cheese-style" antenna was mounted vertically to generate a horizontally flattened beam. This was the first Royal Navy radar with a plan-position indicator. In addition to the microwave warning systems, Coales developed the Type 275 and Type 276 microwave fire-control sets. Further development in magnetrons resulted in 3.2-cm (9.4-GHz) devices generating 25-kW peak power. These were used in the Type 262 fire-control radar and Type 268 target-indication and navigation radar.
United States
In 1922, A. Hoyt TaylorAlbert H. Taylor
Albert Hoyt Taylor was an American electrical engineer who made important early contributions to the development of radar.-Biography:...
and Leo C. Young
Leo C. Young
Leo C. Young was an American radio engineer who had many accomplishments during a long career at the U.S. Naval Research Laboratory...
, then with the U.S. Navy Aircraft Radio Laboratory, noticed that a ship crossing the transmission path of a radio link produced a slow fading in and out of the signal. They reported this as a Doppler effect|Doppler-beat interference that might be used in detecting the passing of an enemy vessel, but no further research was done at that time. In 1930, Lawrence A. Hyland
Lawrence A. Hyland
Lawrence A. "Pat" Hyland was an American electrical engineer. He is one of several people credited with major contributions to the invention of radar, but is probably best known as the man who transformed Hughes Aircraft from Howard Hughes' aviation "hobby shop" into one of the world's leading...
. working for Taylor at the Naval Research Laboratory (NRL) observed the Doppler-beat interference from a passing airplane. This was reported by Taylor to higher authorities; Hyland, Taylor, and Young were granted a patent (U.S. No. 1981884, 1934) for a "System for detecting objects by radio". It was recognized that detection systems would also need to give range measurements, and funding was provided to a project using a pulsed transmitter. This project was assigned to a team led by Robert M. Page
Robert Morris Page
Robert Morris Page was an American physicist who was a leading figure in the development of radar technology. Later, Page served as the Director of Research for the U.S. Naval Research Laboratory.-Life and career:...
, and in late December 1934, a breadboard apparatus successfully detected an aircraft at a range of one mile.
The Navy, however, did not follow this initial effort with a vigorous pursuit, and it was not until January 1939, that their first prototype system, the 200-MHz (1.5-m) XAF, was tested at sea. The Navy coined the acronym RAdio Detection And Ranging (RADAR) for this technology, and in late 1940, ordered this to be exclusively used in documents.
Taylor's 1930 report had been passed on to the U.S. Army's Signal Corps Laboratories
Signal Corps Laboratories
Signal Corps Laboratories 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...
(SCL). Here, 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:...
had projects underway in detecting aircraft from thermal radiation
Thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....
and engine ignition noise, and soon started a project in Doppler-beat detection. Following the success by Page with pulse-transmission, the SCL soon had their own project in this area. In 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...
led in the development of a pulsed system that on December 14 detected aircraft flying in and out of New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
at ranges up to seven miles. By 1938, this had evolved into the Army's first Radio Position Finding (RPF) set, designated SCR-268 (SCR meaning Signal Corps Radio
Signal Corps Radio
Signal Corps Radios were U.S. Army military communications components that comprised "sets". Under the Army Nomenclature System, SCR initially designated "Set, Complete Radio," and later "Signal Corps Radio," though interpretations have varied over time....
, a cover for this secret technology). It operated at 200 MHz 1.5 m, with 7-kW peak power. The received signal was used to direct 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...
.
In Europe, the continued war with Germany had drained the United Kingdom of resources, and the decision was made by Prime Minister Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
to give UK's existing technology secrets to the United States in exchange for access to related American secrets and manufacturing capabilities. In September 1940, 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...
coordinated this exchange, including 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...
, Great Britain's greatest secret.
When the exchange began, the British were surprised to learn they were not unique in their possession of pulse-radar technology. The U.S. Navy's pulse radar system, the CXAM
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...
, was found to be very similar in capability to their 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...
technology. Although the U.S. had developed pulsed radar independent of the British, there were serious weaknesses in America's efforts, the greatest of which was the lack of integration of radar into a unified air defense system. Here the British were without peer.
The result of the Tizard Mission was a major step forward for utilization of radar technology, both in the transfer of the organizational knowledge that Watson-Watt had worked out as well as the British microwave technology. Although both the NRL and SCL had experimented with 10–cm transmitters, they were stymied by the problem of insufficient transmitter power. The cavity magnetron was the answer the U.S. was looking for, and it led to the creation of 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...
(Rad Lab). Before the end of 1940, the Rad Lab was started at MIT, and thereafter essentially all radar development in the U.S. was in centimeter-wavelength systems. This major center for research employed almost 4,000 people at its peak during World War II.
Two special radar-related organizations should be noted. As the Rad Lab began operations at MIT, a companion group called the Radio Research Laboratory
Radio Research Laboratory
The Radio Research Laboratory , located on the campus of Harvard University was an 800-person secret research laboratory during World War II. Under the U.S...
(RRL) was established at nearby Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
. Headed by Frederick Terman
Frederick Terman
Frederick Emmons Terman was an American academic. He is widely credited with being the father of Silicon Valley.-Education:...
, this was devoted to research and development in electronic countermeasures
Electronic countermeasures
An electronic countermeasure is an electrical or electronic device designed to trick or deceive radar, sonar or other detection systems, like infrared or lasers. It may be used both offensively and defensively to deny targeting information to an enemy...
to radar. Another organization was the Combined Research Group (CRG) housed in highest secrecy at the NRL. This involved American, British, and Canadian personnel charged with developing standardized Identification Friend of 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...
(IFF) systems used with radars, vital in preventing fratricide
Fratricide
Fratricide is the act of a person killing his or her brother....
.
Metric-Wavelength
After sea trials, the original XAF was improved by the NRL and designated CXAMCXAM 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...
; these 200-MHz (1.5-m), 15-kW sets went into limited production with first deliveries in May 1940. The CXAM was refined into the SK early-warning radar, with production deliveries starting in late 1941. This 200-MHz (1.5-m) system used a "flying bedspring" antenna and had a 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). With 200-kW peak-power output, it could detect aircraft at ranges up to up 100 miles, and ships to about 30 miles. The SK remained the standard early-warning radar for large U.S. vessels throughout World War II. Derivatives for smaller vessels included the SA and SC. About 500 of these early-warning sets of all versions were built. The related SD was a 114-MHz (2.63-m) set designed by the NRL for use on submarines; with a periscope-like antenna mount, it gave early warning but not the direction of approaching aircraft. The BTL developed a 500-MHz (0.6-m) fire-control radar designated FA (later designated Mark 1). A few went into service in mid-1940, but with only 2-kW power, they were soon replaced.
As previously described, the SCL's first radio-based detection and tracking system, designated SCR-268, was demonstrated in late 1938. Even before this went into service, Harold 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:...
led a team at the SCL in developing a better system; the SCR-270 was the mobile version, and the SCR-271 a fixed-position version. Operating at 106 MHz (2.83 m) with 100 kW pulsed power, these had a range up to 240 miles and began entry into service in late 1940. On December 7, 1941, an SCR-270 at 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...
in 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...
detected the attacking Japanese aircraft at a range of 132 miles (212 km), but this information was not used effectively at the command level.
Only one other metric radar of significance was developed by the SCL. After Pearl Harbor, there was concern that a similar attack might be used to destroy locks at the vital 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...
. A transmitter tube that delivered 240-kW pulsed power at 600 MHz (0.5 M) had been developed by Zahl. A team led by 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...
used this tube in adapting an SCR-268 suitable for picket ships
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...
operating up to 100 miles offshore. The same basic set was modified to become the AN/TPS-3, a light-weight, portable, early-warning radar used at beachheads and captured airfields in the South Pacific. About 900 of these radars were produced.
A British ASV Mk II, was brought to America by the Tizard Mission. With the ASE for use on large patrol aircraft such as the PBY Catalina
PBY Catalina
The Consolidated PBY Catalina was an American flying boat of the 1930s and 1940s produced by Consolidated Aircraft. It was one of the most widely used multi-role aircraft of World War II. PBYs served with every branch of the United States Armed Forces and in the air forces and navies of many other...
. This was America's first airborne radar in operational service; about 7,000 ASEs were built. The NRL was already working on a 515-MHz (58.3-cm) air-to-surface radar for the TBF Avenger
TBF Avenger
The Grumman TBF Avenger was a torpedo bomber developed initially for the United States Navy and Marine Corps, and eventually used by several air or naval arms around the world....
, a new fighter-bomber. Portions of the ASE were adopted for this radar, and it went into production as the ASB when the U.S. entered the war. This set was also adopted by the newly formed Army Air Forces as the SCR-521. The last of the non-magnetron radars, over 26,000 ASB/SCR-521 sets were built.
The history of World War II radar could not be complete without noting the Variable Time (VT)
Proximity fuze
A proximity fuze is a fuze that is designed to detonate an explosive device automatically when the distance to target becomes smaller than a predetermined value or when the target passes through a given plane...
Fuze. Although not a radar per se, it was closely associated with this technology and involved one of the largest financial outlays of World War II. In the summer of 1940, the National Defense Research Committee
National Defense Research Committee
The National Defense Research Committee was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the United States from June 27, 1940 until June 28, 1941...
(NDRC), predecessor of the OSRD (noted later) asked Merle Tuve
Merle Tuve
Merle Anthony Tuve, PhD was an American scientist and geophysicist who was the founding director of the Johns Hopkins University Applied Physics Laboratory. He was a pioneer in the use of pulsed radio waves whose discoveries opened the way to the development of radar and nuclear...
of the Carnegie Institution of Washington to take the lead in developing a device that could increase the probability of kill
Probability of kill
Computer games, simulations, models, and operations research programs often require a mechanism to determine statistically whether the engagement between a weapon and a target resulted in a kill, or the probability of kill...
for gun projectiles. From this, the variable-time fuze emerged as an improvement for the fixed-time fuze commonly used to detonate the projectile. The resulting device sensed when the projectile neared the target – thus, the name variable-time was applied. Alan Butement
W. A. S. Butement
William Alan Stewart Butement , was a defence scientist and public servant. A native of New Zealand, he made extensive contributions to radar development in Great Britain during World War II, served as the first chief scientist for the Australian Defence Scientific Service, then ended his...
had actually conceived the idea for a proximity fuse while he was developing the Coastal Defense system in Great Britain during 1939, and his basic concept had been brought to the U.S. by the Tizard Mission.
A VT fuze, screwed onto the head of a projectile, radiated a CW signal in the 180–220 MHz range. As the projectile neared its target, this was reflected at a Doppler shifted
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...
frequency by the target and beat with the original signal, the amplitude of which triggered the detonation. The device used electronics much smaller than anything previously built, and 112 industries and research institutions were eventually involved. In 1942, the project was transferred to the Applied Physics Laboratory
Applied Physics Laboratory
The Johns Hopkins University Applied Physics Laboratory , located in Howard County, Maryland near Laurel and Columbia, is a not-for-profit, university-affiliated research center employing 4,500 people. APL is primarily a defense contractor. It serves as a technical resource for the Department of...
, formed by Johns Hopkins University
Johns Hopkins University
The Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university based in Baltimore, Maryland, United States...
for this purpose. During the war, some 22 million VT fuses for several sizes of projectiles were manufactured.
Centimeter
Operating under the Office of Scientific Research and Development
Office of Scientific Research and Development
The Office of Scientific Research and Development was an agency of the United States federal government created to coordinate scientific research for military purposes during World War II. Arrangements were made for its creation during May 1941, and it was created formally by on June 28, 1941...
, an agency reporting directly to President Franklin Roosevelt
Franklin D. Roosevelt
Franklin Delano Roosevelt , also known by his initials, FDR, was the 32nd President of the United States and a central figure in world events during the mid-20th century, leading the United States during a time of worldwide economic crisis and world war...
, the Rad Lab was directed by Lee Alvin DuBridge
Lee Alvin DuBridge
Lee Alvin DuBridge was an American educator and physicist.DuBridge was born in Terre Haute, Indiana, and graduated from Cornell College in 1922, and then began a teaching assignment at the University of Wisconsin–Madison, from which he received an M.A. degree in 1924 and a Ph.D. in 1926...
with the eminent scientist Isidor Isaac Rabi
Isidor Isaac Rabi
Isidor Isaac Rabi was a Galician-born American physicist and Nobel laureate recognized in 1944 for his discovery of nuclear magnetic resonance.-Early years:...
serving as his deputy. E. G. "Taffy" Bowen
Edward George Bowen
Edward George 'Taffy' Bowen, CBE, FRS was a British physicist who made a major contribution to the development of radar, and so helped win both the Battle of Britain and the Battle of the Atlantic...
, one of the original developers of RDF and a member of the Tizard Mission, remained in the U.S. as an adviser to the Rad Lab.
As it was formed, the Rad Lab was assigned three initial projects: a 10 cm airborne intercept radar, a 10 cm gun-laying system for anti-aircraft use, and a long-range aircraft navigation system. The cavity magnetron brought to America by the Tizard Mission was exactly duplicated by the Bell Telephone Laboratories
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
(BTL) and placed into production for use by the Rad Lab in the first two projects. The third project, which did not involve radar, ultimately became LORAN
LORAN
LORAN is a terrestrial radio navigation system using low frequency radio transmitters in multiple deployment to determine the location and speed of the receiver....
, the first worldwide radio navigation system. LORAN was conceived by Alfred Lee Loomis
Alfred Lee Loomis
Alfred Lee Loomis was an American attorney, investment banker, philanthropist, scientist/physicist, pioneer in military radar usages, inventor of the LORAN or Long Range Navigation System, and lifelong patron of scientific research...
, a financial tycoon and private scientist who was instrumental in starting the Rad Lab.
To get underway, the Rad Lab built an experimental breadboard set with a 10 cm transmitter and receiver using separate antennas (the T-R switch was not yet available). This was successfully tested from atop the laboratory at MIT in February 1941, detecting an aircraft at a range of 4 miles.
The Rad Lab and BTL also initiated improvements in the magnetron, extending the device and associated systems to higher wavelengths. As more frequencies were used, it became common to refer to centimeter radar operations in the following bands:
-
- P-Band – 30-100 cm (1-0.3 GHz)
- L-Band – 15-30 cm (2-1 GHz)
- S-Band – 8-15 cm (4-2 GHz)
- C-Band – 4-8 cm (8-4 GHz)
- X-Band – 2.5-4 cm (12-8 GHz)
- K-Band – Ku: 1.7-2.5 cm (18-12 GHz); Ka: 0.75-1.2 cm (40-27 GHz).
The K-band was divided because of absorption by atmospheric water vapor. These ranges are those given by the IEEE Standards. Slightly divergent values are shown in other standards, such as those of the RSGB
RSGB
-Organizations:* Radio Society of Great Britain, a radio operators organization established in 1913* Russian Soviet Government Bureau, informal diplomatic organization in the USA from 1919 to 1921-Videogames:...
.
P-Band fire-control
After the BTL developed the FA, the first fire-control radar for the U.S. Navy, it improved this with the FC (for use against surface targets) and FD (for directing anti-aircraft weapons). A few of these 60 cm (750 MHz) sets began service in the fall of 1941. They were later designated Mark 3 and Mark 4, respectively. Ultimately, about 125 Mark 3 and 375 Mark 4 radars were produced.S-Band airborne
For the Airborne Intercept radar, the Rad Lab 10 cm breadboard set was fitted with a parabolic antennaParabolic antenna
A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish...
having 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 ....
scanning capabilities. Cathode-ray tube indicators and appropriate controls were also added. This was very much a team effort, but Edwin McMillan
Edwin McMillan
Edwin Mattison McMillan was an American physicist and Nobel laureate credited with being the first ever to produce a transuranium element. He shared the Nobel Prize in Chemistry with Glenn Seaborg in 1951....
was responsible for building and testing the engineering set. This was first flight tested near the end of March 1941, giving target returns at up to five-miles distance and without ground clutter
Radar signal characteristics
A radar system uses a radio frequency electromagnetic signal reflected from a target to determine information about that target. In any radar system, the signal transmitted and received will exhibit many of the characteristics described below....
, a primary advantage of microwave radar. Designated SCR-520, this was America's first microwave radar. (The Air Forces was then a part of the U.S. Army and used the SCR designation for radio-based systems.) Although this saw limited service on some larger patrol aircraft, it was too heavy for fighter aircraft. Later upgraded to the much lighter SCR-720, thousands of these sets were manufactured and used extensively by both the U.S. and Great Britain (as the AI Mk X) throughout the war.
S-Band Army Gun-Laying
Incorporation of microwave technology into gun-laying systems had already started in Great Britain, but it was included with high priority at the Rad Lab because of its urgent need. The project, with Ivan GettingIvan A. Getting
Ivan Alexander Getting was an American physicist and electrical engineer, credited with the development of the Global Positioning System...
as the leader, started with the same 10-cm breadboard used in the AI project. Development of the GL system was, however, far more complex. A highly complex servomechanism was needed to direct a large parabolic reflector, and an automatic tracker was also needed. Upon the detection of a target, the receiver output would be used to put the servo control into a track-lock mode. The mount and reflector were developed in cooperation with the Central Engineering Office of Chrysler
Chrysler
Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....
. The BTL developed the electronic analog computer, called the M-9 Predictor-Corrector
Predictor-corrector method
In mathematics, particularly numerical analysis, a predictor–corrector method is an algorithm that proceeds in two steps. First, the prediction step calculates a rough approximation of the desired quantity...
unit, containing 160 vacuum tubes. All of this finally came together for testing by the customer (the Army Signal Corps) in May 1942. Designated the SCR-584
SCR-584 radar
The SCR-584 was a microwave radar developed by the MIT Radiation Laboratory during World War II. It replaced the earlier and much more complex SCR-268 as the US Army's primary anti-aircraft gun laying system as quickly as they could be produced...
Anti-Aircraft Gun-Laying System, about 1,500 of these were used in the European and Pacific war theaters starting in early 1944.
S-Band Navy Search
Shortly after the 10 cm experimental breadboard was demonstrated, the Navy requested that the Rad Lab develop an S-band search radar for shipboard and airborne applications. Under the leadership of Ernest PollardErnest C. Pollard
Ernest Charles "Ernie" Pollard was a professor of physics and biophysics and an author, who worked on the development of radar systems in World War II, worked on the physics of living cells, and who wrote textbooks and approximately 200 papers on nuclear physics and radiation biophysics.-...
, the 50 kW SG shipboard set was given sea trials in May 1941, followed shortly by the ASG version for large patrol aircraft and Navy 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...
s. With a gyro-stabilized mount, the SG could detect large ships at 15 miles and a submarine periscope at 5 miles. About 1,000 of these sets were built. The ASG was designated AN/APS-2 and commonly called "George"; some 5,000 of these were built and used very effectively in finding enemy submarines.
A compact version of the SG for PT boat
PT boat
PT Boats were a variety of motor torpedo boat , a small, fast vessel used by the United States Navy in World War II to attack larger surface ships. The PT boat squadrons were nicknamed "the mosquito fleet". The Japanese called them "Devil Boats".The original pre–World War I torpedo boats were...
s was designated the SO. These were introduced in 1942. Other direct descendants included the SF, a search-set for lighter warships, the SH for large merchant vessels, and the SE and SL, similar to the SO, for other smaller ships. The Navy also adopted versions of the Army's SCR-584 (without the M-9 unit but with gyro-stabilizers) for shipboard search radars, the SM for heavy carriers and the SP for smaller carriers. None of these were produced in large quantities, but were of great service in the war effort.
The BTL developed the SJ, an S-Band supplement for the SD meter-wave radar on submarines. The antenna for the SJ could be sweep the horizon to about 6 miles with good accuracy. Late in the war, the SV became available, increasing the detection range to 30 miles.
L-Band Airborne Early-Warning
The most ambitious, long-term effort of the Rad Lab was Project Cadillac, developing the first airborne early-warning radar system. With Jerome WiesnerJerome Wiesner
Jerome Bert Wiesner was an educator, a Science Advisor to U.S. Presidents Eisenhower and Kennedy and Johnson, an advocate for arms control, and a critic of anti-ballistic-missile defense systems...
as the leader, about 20 percent of the staff would ultimately be involved. Designated AN/APS-20, this 20 cm (1.5 GHz), 1 MW radar weighing 2,300 pounds including a 8-foot radome
Radome
A radome is a structural, weatherproof enclosure that protects a microwave or radar antenna. The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna. In other words, the radome is transparent to radar or radio waves...
enclosing a spinning parabolic antenna. Carried by a TBF Avenger
TBF Avenger
The Grumman TBF Avenger was a torpedo bomber developed initially for the United States Navy and Marine Corps, and eventually used by several air or naval arms around the world....
carrier-based aircraft, it could detect large aircraft at ranges up to 100 miles. The airborne system included a television camera to pick up the PPI display, and a VHF link transmitted the image back to a Combat Information Center
Combat Information Center
The Operations Room is the tactical center of a warship or AWAC aircraft providing processed information for command and control of the near battle space or 'area of operations'...
on the home carrier. The system was first flown in August 1944 and went into service the following March. This was the foundation from which the post-war Airborne Warning and Control System (AWACS) concept evolved.
X-Band
At the Rad Lab in 1941, Luis Alvarez invented a new type of phased arrayPhased array
In wave theory, a phased array is an array of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.An antenna array...
antenna having excellent radiation characteristics. When the 3 cm magnetron was developed, the Alvarez antenna was used in a number of X-Band radars. The Eagle, later designated AN/APQ-7, provided a map-like image of the ground some 170 miles along the forward path of a bomber. About 1,600 Eagle sets were built and used by the Army Air Forces primarily over Japan. The same technology was used in developing the ASD (AN/APS-2 commonly known as "Dog"), a search and homing radar used by the Navy on smaller bombers; this was followed by several lighter versions, including the AIA-1 known as the "radar gunsight".
The Alvarez antenna was also used in developing the Ground Control Approach (GCA), a combined S-Band and X-Band blind-landing system for military airports; this system was particularly used in assisting planes returning from bombing runs.
The BTL also developed X-Band radars. The Mark 8 (FH) fire-control radar, was based on a new type of antenna developed by George Mueller
George Mueller (NASA)
George Mueller was Associate Administrator of the NASA Office of Manned Space Flight from September 1963 until December 1969...
. This was an end-fired array of 42 pipe-like waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
s that allowed electronic steering of the beam. The Mark 22 was a "nodding" system used for target height-finding with fire-control radars. With an antenna shaped like an orange slice, it gave a very narrow, horizontal beam to search the sky. The Army also adopted this as the AN/TPS-10, a land-version that was commonly called "Li'l Abner".
Although not implemented into a full system until after the war, the monopulse technique
Monopulse radar
Monopulse radar is an adaptation of conical scanning radar which sends additional information in the radar signal in order to avoid problems caused by rapid changes in signal strength. The system also makes jamming more difficult...
was first demonstrated at the NRL in 1943 on an existing X-Band set. The concept is attributed to Robert Page, and was developed to improve the tracking accuracy of radars. Following the war, essentially all new radar systems used this technology, and was the basis of the AN/FPS-16
AN/FPS-16
The AN/FPS-16 is a highly accurate ground-based monopulse single object tracking radar , used extensively by the NASA manned space program and the U.S. Air Force...
, the most widely used tracking radar in history.
Soviet Union
World War II came to the Soviet UnionSoviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
with the invasion by Germany on June 22, 1941. Although the USSR had outstanding scientists and engineers, began research on what would later become radar (radiolokatsiy) as soon as anyone else, and made good progress with early magnetron development, they entered the war without a fielded, fully capable radar system.
Pre-War Radio-Location Research
The USSR military forces were the Raboche-Krest'yanskaya Krasnaya Armiya (RKKA, the Workers' and Peasants' Red Army), the Raboche-Krest'yansky Krasny Flot (RKKF, the Workers' and Peasants' Red Fleet), and the Voenno-Vozdushnye Sily(VVS, Soviet Air Forces).In only a few years after the close of World War I, Germany's Luftwaffe had aircraft capable of penetrating deep into Soviet territory. Visual observation was use for detecting approaching aircraft. For nighttime detection, the Glavnoe artilkeriisko upravlenie (GAU, Main Artillery Administration), of the Red Army, had developed an acoustical unit that was used to aim a searchlight at the aircraft. These techniques had a problem with aircraft that were above the clouds or at a considerable distance; to overcome this, research was also initiated on detection by electromagnetic means. General-leitenant (Lieutenant-General) M. M. Lobanov was responsible for these efforts in the GAU, and later thoroughly documented this activity.
Leningrad
Most of the early work in radioobnaruzehenie (radio-detection) took place in LeningradLeningrad
Leningrad is the former name of Saint Petersburg, Russia.Leningrad may also refer to:- Places :* Leningrad Oblast, a federal subject of Russia, around Saint Petersburg* Leningrad, Tajikistan, capital of Muminobod district in Khatlon Province...
, initially at the Leningradskii Elektrofizicheskii Institut, (Leningrad Electro-Physics Institute, LEPI). Here, Abram F. Ioffe
Abram Ioffe
Abram Fedorovich Ioffe was a prominent Russian/Soviet physicist. He received the Stalin Prize , the Lenin Prize , and the Hero of Socialist Labor . Ioffe was an expert in electromagnetism, radiology, crystals, high-impact physics, thermoelectricity and photoelectricity...
, generally considered the leading physicist at that time in the Soviet Union, was the Scientific Director. The LEPI concentrated on radiating continuous wave
Continuous wave
A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...
(CW) signals, detecting the existence and direction of their reflections for use in early warning systems.
While the GAU was mainly interested in detection, the Voiska Protivo-vozdushnoi aborony (PVO, Air Defense Forces) was interested in also determining the distance to the aircraft (the range). Pavel K. Oshchepkov
Pavel K. Oshchepkov
Pavel Kondratyevich Oshchepkov was a Russian physicist who had a leading role in the development of radio-location in the USSR. During the Great Purge he was sent to a Gulag labor camp for 10 years...
on the PVO technical staff in Moscow, strongly believed that the radiolokatory (radio-location) equipment should be pulsed, thus potentially allowing the range to be determined directly. He was transferred to Leningrad to be in charge of a Special Construction Bureau (SCB) for radio-location equipment.
To examine the various types of detection, a meeting was called by the Russian Academy of Sciences
Russian Academy of Sciences
The Russian Academy of Sciences consists of the national academy of Russia and a network of scientific research institutes from across the Russian Federation as well as auxiliary scientific and social units like libraries, publishers and hospitals....
; this was held at Leningrad on January 16, 1934, and chaired by Ioffe. Radio-location emerged as the most promising technique, but the type (CW or pulsed) as well as the wavelength region (high frequency
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
or 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...
) were left to be resolved
At the SCB, Oshchepkov's team developed an experimental pulsed radio-location system operating at 4 m (75 MHz.). This had a peak power of about 1 kW and a 10-μs pulse duration; separated transmitting and receiving antennas were used. In April 1937, test showed a detection range of near 17 km at a height of 1.5 km. Although this was a good beginning for pulsed radio-location, the system was not capable of directly measuring range (the technique of using the pulses for determining range was known from studies of the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
but was not initially incorporated ). Although he never had the opportunity to add ranging to his system, Oshchepkov is nevertheless often called the father of radar in the Soviet Union.
While Oshchepkov was working on pulsed systems, work continued on CW research at the LEPI. In 1935, the LEPI became a part of the Nauchno-issledovatel institut-9 (NII-9, Scientific Research Institute #9), one of several technical organizations under the GAU. With M. A. Bonch-Bruevich
Mikhail Aleksandrovich Bonch-Bruevich
Mikhail Aleksandrovich Bonch-Bruevich , sometimes spelled Bonch-Bruyevich, was a Russian engineer, scientist, and professor. Generally considered the leading authority on radio in Russia in the first decades of the 20th century, he greatly influenced the pre-radar development of radio-location in...
as the Scientific Director, research continued in CW techniques. Several experimental systems were developed, including a VHF set designated Bistro (Rapid) and Burya (Storm) operating in the microwave region. The best elements of these were incorporated into a mobile system called Ulavlivatel Samoletov (RUS, Radio Catcher of Aircraft), soon designated as RUS-1. This CW, bi-static
Bistatic radar
Bistatic radar is the name given to a radar system which comprises a transmitter and receiver which are separated by a distance that is comparable to the expected target distance. Conversely, a radar in which the transmitter and receiver are collocated is called a monostatic radar...
system had a truck-mounted transmitter operating at 4.7 m (64 MHz) and two truck-mounted receivers.
In June 1937, all of the work in Leningrad on radio-location suddenly stopped. The infamous Great Purge
Great Purge
The Great Purge was a series of campaigns of political repression and persecution in the Soviet Union orchestrated by Joseph Stalin from 1936 to 1938...
of Joseph Stalin
Joseph Stalin
Joseph Vissarionovich Stalin was the Premier of the Soviet Union from 6 May 1941 to 5 March 1953. He was among the Bolshevik revolutionaries who brought about the October Revolution and had held the position of first General Secretary of the Communist Party of the Soviet Union's Central Committee...
swept over the military high commands and the supporting scientific community, resulting in near two million executions. The SCB was closed; Oshchepkov was charged with "high crimes" and sentenced to 10 years at a Gulag
Gulag
The Gulag was the government agency that administered the main Soviet forced labor camp systems. While the camps housed a wide range of convicts, from petty criminals to political prisoners, large numbers were convicted by simplified procedures, such as NKVD troikas and other instruments of...
penal labor camp. The NII-9 was also intended to be closed, but was saved through the influence of Bonch-Bruyevich, who had been a favorite of Vladimir Lenin
Vladimir Lenin
Vladimir Ilyich Lenin was a Russian Marxist revolutionary and communist politician who led the October Revolution of 1917. As leader of the Bolsheviks, he headed the Soviet state during its initial years , as it fought to establish control of Russia in the Russian Civil War and worked to create a...
in the prior decade, NII-9 as an organization was saved, and Bonch-Bruyevich was named the new director. Overall, this resulted in a loss of more than a year in development activities.
The RUS-1 system was tested and put into production in 1939, then entered limited service in 1940, becoming the first deployed radio-location system in the Red Army. Bonch-Bruyevich died in March, 1941, and there was no strong leader to further push the CW radio-location developments.
The Nauchnoissledovatel skii ispytalel nyi institut suyazi RKKA (NIIIS-KA, Scientific Research Institute of Signals of the Red Army), an organization that had originally highly opposed radio-location technology, was now placed in overall control of this development in all of the Soviet Union. They took over Oshchepkov's pulsed system, and by July 1938, had a fixed-position, bistatic experimental system that detected an aircraft at 30-km range at heights of 500 m, and at 95-km range for high-flying targets at 7.5 km altitude.
The project was then taken up by Ioffe's LPTI, resulting in the development of a system designated Redut (Redoubt) with 50-kW peak-power and a 10-μs pulse-duration. The Redut was first field tested in October 1939, at a site near Sevastopol
Sevastopol
Sevastopol is a city on rights of administrative division of Ukraine, located on the Black Sea coast of the Crimea peninsula. It has a population of 342,451 . Sevastopol is the second largest port in Ukraine, after the Port of Odessa....
, a strategic port in Ukraine on the coast of the Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
.
During 1940, the LEPI took over Redut and developed the very important capability of range measurements. A cathode-ray display, made from an oscilloscope, was used to show the range information. In July 1940, the resulting system was designated RUS-2. A transmit-receive device (a duplexer) to allow operating with a common antenna was developed in February 1941. All of this testing was done at an experimental station at Toksovo
Toksovo
Toksovo is an urban locality in Vsevolozhsky District of Leningrad Oblast, Russia, located to the north of St. Petersburg on the Karelian Isthmus. It is served by two neighboring stations of the Saint Petersburg-Kuznechnoye railroad: Toksovo and Kavgolovo...
(near Leningrad), and an order was placed with the Svetlana Factory for 15 systems.
The final RUS-2 had pulse-power of near 40 kW at 4 m (75 MHz). The equipment was in a cabin on a motor-driven platform, and with a seven-element Yagi-Uda antenna mounted about five meters above the roof. The cabin, and thus the antenna, could be rotated over a large sector to aim the transmit-receive pattern. The detection range was 10 to 30 km for targets as low as 500 m and 25 to 100 km for higher-altitude targets. The variance was about 1.5 km for range and 7 degrees for azimuth.
Kharkiv
A second-pre-war center for radio-location research was in Kharkiv, Ukraine, some 400 miles (640 km) southeast of Leningrad. Here the Ukrainian Institute of Physics and TechnologyKharkov Institute of Physics and Technology
The Kharkiv Institute of Physics and Technology is the oldest and largest physical science research centre in the Ukraine.This was where the UPTI Affair occurred in 1938.-External links:*...
(UIPT) operated in close cooperation with Kharkiv University
Kharkiv University
The University of Kharkiv or officially the Vasyl Karazin Kharkiv National University is one of the major universities in Ukraine, and earlier in the Russian Empire and Soviet Union...
(KU). The UIPT became known outside the USSR, and attracted visits from world-recognized physicists such as Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
and Paul Dirac
Paul Dirac
Paul Adrien Maurice Dirac, OM, FRS was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...
. Future Nobel Laureate Lev Landau
Lev Landau
Lev Davidovich Landau was a prominent Soviet physicist who made fundamental contributions to many areas of theoretical physics...
headed the Theoretical Department. The department-level Laboratory of Electromagnetic Oscillations (LEMO) was led by Abram A. Slutskin
Abram A. Slutskin
Abram A. Slutskin was a Russian scientist and professor who had a major role in shaping radio science in the Soviet Union. He was a pioneer in cavity magnetron development and the application of these devices in radio-location systems....
.
At the LEMO, magnetrons were a major item of research. By 1934, a team led by Aleksandr Y. Usikov had developed a number of segmented-anode magnetrons covering 80 to 20 cm (0.37 to 1.5 GHz), with output power between 30 and 100 W. Semion Y. Braude developed a glass-cased magnetron producing up to 17 kW with 55 percent efficiency at 80 cm (370 kHz), tunable over a wavelength change of 30 percent. These were described in detail in German-language journal papers – a practice adopted by the UIPT to gain widespread readership of their work.
In 1937, the NIIIS-KA contracted with the LEMO for developing a pulsed radio-location system for anti-aircraft applications. The project was code-named Zenit (a popular football team at the time) and was under the guidance of Slutskin. The transmitter development was led by Usikov. The unit used a 60-cm (500-MHz) magnetron pulsed at 7–10-μs duration and providing 3-kW pulsed power, later increased to near 10 kW.
Braude led the development of the receiver. This was a superheterodyne unit initially using a tunable magnetron as the local oscillator, but this lacked stability and was replaced with a circuit using an RCA type 955 acorn triode. The returned pulses were displayed on a cathode-ray oscilloscope
Oscilloscope
An oscilloscope is a type of electronic test instrument that allows observation of constantly varying signal voltages, usually as a two-dimensional graph of one or more electrical potential differences using the vertical or 'Y' axis, plotted as a function of time,...
, giving range measurement.
Zenit was first tested in October 1938. In this, a medium-sized bomber was detected at a range of 3 km, and needs for improvements were determined. After the changes had been made, a demonstration was given to all of the interested customers in September 1940. It was shown that the three coordinates (range, altitude, and azimuth) of an aircraft flying at heights between 4,000 and 7,000 meters could be determined at up to 25-km distance, but not with suitable accuracy. Also, with the antennas aimed at a low angle there was a dead zone of some distance; this was caused by interference from ground-level reflections.
While this performance was not satisfactory for immediate gun-laying applications, it did show the way for future systems. Another characteristic, however, rendered Zenit completely unsuitable for use with fire-controllers on anti-aircraft guns. A null-reading method was used for analyzing the signals; this made it necessary to determine azimuth and elevation coordinates independently, requiring a sequence of antenna movements that took 38 seconds for the three coordinates.
Work at the LEMO continued on Zenit, particularly in converting it into a single-antenna system designated Rubin. This effort, however, was disrupted by the invasion of the USSR by Germany in June 1941. In a short while, all of the critical industries and other operations in Kharkov were ordered to be evacuated far into the East.
Wartime
When the German blitzkriegBlitzkrieg
For other uses of the word, see: Blitzkrieg Blitzkrieg is an anglicized word describing all-motorised force concentration of tanks, infantry, artillery, combat engineers and air power, concentrating overwhelming force at high speed to break through enemy lines, and, once the lines are broken,...
swept into the Soviet Union in June 1941, three massive, tank-led Army groups moved in on a 900-mile front with Leningrad, Moscow, and the Ukraine region as objectives. There followed what became known to the Soviets as the Great Patriotic War.
Great Patriotic War (term)
The term Great Patriotic War , Velíkaya Otéchestvennaya voyná,) is used in Russia and some other states of the former Soviet Union to describe the portion of World War II from 22 June 1941 to 9 May 1945, against Nazi Germany and its allies in the many fronts of Soviet-German war.-History:The term...
The Komitet Oborony (Defense Committee – the small group of leaders surrounding Stalin) gave first priority to the defense of Moscow. The critical laboratories and factories in Leningrad were to be evacuated to the East. The same would be done for Kharkiv, the technical center of Ukraine.
A number of different radar systems were produced by the Soviet Union in the relocated facilities during the war. However, some 2,600 radar sets of various types were provided by Great Britain and America under the Lend-Lease Program.
Ground-Based
The Sveltana Factory in Leningrad had built a total of about 45 RUS-1 systems. These were deployed along the western USSR borders and in the Far East. Without direct ranging capability, however, the military found the RUS-1 to be of little value.When air attacks on Leningrad began, the RUS-2 test unit that had been set up at the Toksovo experimental site was pressed into tactical operation, providing early-warning of Luftwaffe (German Air Force) raids that were often in formations of as many as 100 bombers. With a range up to 100 km, this unit gave a good warning to the city, as well as to notifying the defending fighter aircraft. This gained the attention of military leaders who previously had shown little interest in radio-location equipment.
In mid-July, the radio-location activities of the LEPI and NII-9 were sent to Moscow where they were combined with existing units of the NIIIS-KA. A RUS-2 system was set up near Moscow and manned by recently moved LPTI personnel; it was first used on July 22, when it detected at night an incoming flight of about 200 German bombers while they were 100 km away. This was the first air attack on Moscow, and it immediately led to three rings of anti-aircraft batteries being built around the city, all connected to a central command post.
Several transmitters and receivers built for RUS-2 systems were quickly adapted by the NIII-KA for fixed radio-location stations around Moscow. Designated as RUS-2S and also P2 Pegmatit, these had their Yagi antenna mounted on 20-meter steel towers and could scan a sector of 270 degrees. For building additional equipment, in January 1942, Factory 339 in Moscow became the first manufacturing facility in the Soviet Union devoted to radio-location sets (soon officially called radar). During 1942, this facility built and installed 53 RUS-2S sets around Moscow and other critical locations in the USSR.
Factory 339 had an outstanding research and engineering staff; this had earlier been administratively separated and designated as the Scientific Institute of Radio Industry No. 20 (NII-20). Victor V. Tikhomirov
Victor V. Tikhomirov
Victor Vasilievitch Tikhomirov was an outstanding Soviet engineer and scientist in the fields of radio electronics and automation. He was a corresponding member of the Soviet Academy of Sciences, three times a laureate of the Stalin Prize, and was awarded two Orders of Lenin and other orders and...
, a pioneer in domestic aircraft radio engineering, was the Technical Director. (Later, the Tikhomirov Scientific Research Institute of Instrument Design
Tikhomirov Scientific Research Institute of Instrument Design
JSC V.V. Tikhomirov Scientific Research Institute of Instrument Design is a joint stock company, one of the major Russian enterprises in the development of weaponry control systems for fighter planes and mobile medium range anti-aircraft SAM defense vehicles.The institute was created on March 1,...
was named in his honor.) Factory 339 and the associated NII-20 dominated radar equipment development and fabrication in the USSR throughout the war.
Many sets of a number of different versions of the RUS-2 were built at Factory 339 during the war. While providing early warning, these sets suffered from the deficiency of not providing target height (elevation angle). Thus, they were mainly used in conjunction with visual-observation posts, with humans using optical devices for estimating altitude and identifying the type of aircraft.
From the time of the first efforts in radio-location, the question had been raised as to how the aircraft identification could be made – was it friendly or an enemy? With the introduction of RUS-2, this problem required an immediate solution. The NII-20 developed a unit to be carried on an aircraft that would automatically respond as "friendly" to a radio illumination from a Soviet radar. A transponder
Transponder (aviation)
A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation...
, designated as SCH-3 and later called an 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...
(IFF) unit, was placed into production at Factory 339 in 1943. This unit initially responded only to the signal of RUS-2, and only a relatively small number of these and successor units were built in the USSR.
The RUS-2 was sponsored by the PVO and intended for early warning. The GAU still wanted a gun-laying system capable of supporting the anti-aircraft batteries. Upon arriving in Moscow, the radio-location group of the NII-9 continued working for the PVO on this problem, returning to Burya, the experimental microwave set built earlier. Within a few weeks, a team led by Mikhail L. Sliozberg and with the cooperation of NII-20, developed a bi-static CW set designated Son (Sleep) using a 15-cm (2.0-GHz) magnetron.
In early October, the experimental Son set was tested in combat by an anti-aircraft battalion near Moscow. The performance of the radio-based Son was poor as compared with that of the existing optics-based Puazo-3, a stereoscopic range-finder that Oshchepkov had earlier improved. The project was discontinued, and no further attempts were made to use magnetrons in radio-location sets. After this failure, NII-9 was sent elsewhere and was no longer involved in radio-location activities. A portion of the radio-location group, including Sliozberg, remained in Moscow working for NII-20.
Shortly after Germany invaded the USSR, a delegation of Soviet military officers visited Great Britain seeking assistance in defense hardware. From their intelligence sources, the Soviets were aware of Britain's gun-laying RDF (Range and Direction Finding
Range and Direction Finding
Range and Direction Finding was the initial technique and hardware in Great Britain that eventually came to be called 'radar.'Since the earliest days of radio , the signals had been used in direction finding on land, sea, and in the air...
) system, the GL Mk II, and asked for this equipment to be tested in the defense of Moscow. In early January 1942, Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
agreed to send one of these systems to Russia, but with the provision that it would be totally secured under British officers and operated by British technicians.
When the ship carrying the equipment arrived at Murmansk
Murmansk
Murmansk is a city and the administrative center of Murmansk Oblast, Russia. It serves as a seaport and is located in the extreme northwest part of Russia, on the Kola Bay, from the Barents Sea on the northern shore of the Kola Peninsula, not far from Russia's borders with Norway and Finland...
, a seaport off the Bering Sea
Bering Sea
The Bering Sea is a marginal sea of the Pacific Ocean. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves....
above the Arctic Circle
Arctic Circle
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. For Epoch 2011, it is the parallel of latitude that runs north of the Equator....
, there was a winter storm and unloading had to wait overnight. The next morning, it was found that the entire GL Mk II system – mounted on three trucks – had disappeared. The British Embassy made an immediate protest, and after several days the officers were informed that the equipment had been taken to Moscow for security.
It indeed had gone to Moscow – directly to NII-20 and Factory 339, where intelligence experts gave it a total examination and Sliozberg led a team in quickly reverse-engineering the hardware. In mid-February, the NII-20 announced that it had developed a new radio-location system designated Son-2a. It was essentially a direct copy of the GL Mk II.
Operating at 5 m (60 MHz), Son-2a used separate trucks for the transmitting and receiving equipment, and a third truck carried a power generator. In use, a dipole-array transmitting antenna giving a broad pattern was fixed in position atop a grounded pole. Separated from the transmitter by about 100 meters, the receiving station was on a rotatable cabin with wing-like antennas mounted on each side. A mast above the cabin held a pair of antennas that were used with a goniometer
Goniometer
A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry is derived from two Greek words, gōnia, meaning angle, and metron, meaning measure....
for height-finding.
Like its GL Mk II "parent" in Great Britain, the Son-2a was not of great assistance in directing searchlights and anti-aircraft guns. Nevertheless, it was put into production and released to the Red Army in December 1942. Over the next three years, about 125 of these sets were built. In addition, over 200 GL Mk IIIC systems (improvements over the Mk II and built in Canada) were provided under the Lend-Lease
Lend-Lease
Lend-Lease was the program under which the United States of America supplied the United Kingdom, the Soviet Union, China, Free France, and other Allied nations with materiel between 1941 and 1945. It was signed into law on March 11, 1941, a year and a half after the outbreak of war in Europe in...
program, making the combination the most-used radar equipment in the Soviet Union during the war.
Ukraine had been the third objective of the invading German Army. By late July 1941, the mechanized forces were approaching this region, and, following orders from the Defense Committee, the UIPT in Kharkov made evacuation preparations. For this, the LEMO was split from the UIPT, and the two organizations would be sent to different cities: Alma-Ata for the main operation and, separated by 1,500 km, Bukhara for the LEMO.
While the preparations for moving were going on, the LEMO was directed to bring the experimental Zeni equipment to Moscow for testing by the NIIIS-KA. In mid-August, Usikov, Braude, and several other LEMO staff members went to Moscow, where they were attached to the NIIIS-KA. The Zenit system was installed in the Moscow outskirts, giving the opportunity for testing in combat. It was found that, while the accuracy of the system was not sufficient for precise aiming, it was satisfactory for barrage firing. It could also be used as a supplement to the RUS-2 surveillance system in guiding fighter aircraft.
In September, the team made field modifications to the Zenit and more tests were run. It was found that the detection range had been doubled, but the dead zone increased by a like amount. The NIIIS-KA believed that the prospects were good for this to be developed into a suitable system, but laboratory conditions were necessary. Thus, the Zenit and all of the NIIIS-KA staff were sent 3,200 km away to Bukhara, joining the remainder of the LEMO as it also moved.
Because of the null-reading method of analyzing the signals, the Zenit system suffered from slowness in measurements (38 seconds for determining the three coordinates) as well as accuracy. It also had a large dead zone caused by ground returns. While still at Kharkov, work had started on Rubin, a system intended to correct Zenit deficiencies. With Slutskin as LEMO Director, this project continued at Bukhara under Usikov's leadership.
A new magnetron was developed; this operated at 54 cm (470 MHz) with a pulse-power increased to 15 kW. A gas-discharge transmit-receive device (a diplexer) was developed for isolating the receiver from the direct transmitter pulse, thus allowing the use of a common transmitting-receiving structure. (A similar development had been made for the RUS-2 common antenna, but this would not have been suitable for the microwave Rubin.)
Several techniques for replacing the null-reading methods were considered, with the final selection making use of a fixture to provide a stationary dipole against which the directional position of the antenna could be continuously determined. Range, azimuth, and elevation were shown on a cathode-ray tube display. There was no provision, however, for feeding this information into an automatic unit for aiming searchlights and guns.
Separate transmitting and receiving dipoles were at the focus of a 3-meter paraboloid
Paraboloid
In mathematics, a paraboloid is a quadric surface of special kind. There are two kinds of paraboloids: elliptic and hyperbolic. The elliptic paraboloid is shaped like an oval cup and can have a maximum or minimum point....
reflector. The antenna assembly, with remote controls, could rotate 0–90 degrees vertically and 0–400 degrees horizontally. The width of the main beam was 16 degrees equatorial and 24 degrees meridian.
The system was carried on two trucks, the electronics and control console in one and the power generator in the other. Both the transmitter magnetron and front-end portions of the receiver were in sealed containers attached to the rear of the reflector. The antenna assembly was on rails and could be rolled out to near the truck.
By August 1943, the prototype Rubin system was completed, with all of the work performed by the small LEMO and NIIIS-KA staffs. The system was transported to Moscow where Usikov, Truten, and others conducted further tests and gave non-combat demonstrations. By this time, the British GL Mk II and its Soviet replication, Sun-2a, were also available and were possibly used in direct comparison with the Rubin; if so, the Rubin would not have faired well.
Rather than releasing the prototype for production, the Army made arrangements for the Rubin to be tried by the Red Fleet Command. At the beginning of 1944, the system was transported to Murmansk, the only non-freezing port in the Soviet Arctic. Here, despite the cold, Usikov continued with tests and demonstrations under better conditions than in the still chaotic Moscow.
Test aboard a ship showed aircraft detection at 60 km and reliable measurement starting at 40 km. The mean errors were no more than 120-m in range and 0.8-degree in azimuth and elevation angles. The time for determining the angular coordinates never exceeded 7 seconds, and the dead zone was down to 500 m. Similar accuracies were found for detecting all types of surface vessels, but with the Rubin antenna at deck level, the detection range was understandably much less than that for aircraft.
During the last year of the war, Rubin was used by the Red Fleet for air and surface surveillance in the polar sector. If the GL Mk II and its clone, SUN-2a, had not become available, the Rubin would likely have been completed much earlier and gone into production. Although never put into regular service, this system provided a good foundation for future magnetron-based radars in the Soviet Union.
Airborne
A number of new fighter and bomber aircraft were being designed in the years before the war. Vladimir PetlyakovVladimir Petlyakov
Vladimir Mikhailovich Petlyakov was a Soviet aeronautical engineer.Petlyakov was born in Sambek in 1891 , where his father was a local official...
led a Soviet Air Forces (VVS) design bureau, responsible for developing a twin-engine attack-dive bomber that was eventually designated Pe-2. Having gotten behind in the schedule, Petlyakov was charged with sabotage and thrown into a technical Gulag; he actually did a large part of his design while interned.
In late 1940, the VVS developed the requirement for an on-board enemy aircraft detection system. The radio-location group at NII-9 in Leningrad was directed to design such a set for the Pe-2. Most of radio-location equipment at that time was large and heavy, and for this aircraft, a small, lightweight set was needed. Also, limitations on antenna size drove the design to frequencies as high as possible. The reflex klystron (as it was later called) had just been developed by Nikolay Devyatkov
Nikolay Devyatkov
Nikolay Devyatkov — was a Soviet/Russian scientist and inventor of microwave vacuum tubes and medical equipment. Full Member of the USSR/Russian Academy of Sciences . Professor of the Moscow Institute of Physics and Technology.Most Devyatkov's scientific papers apply to a microwave vacuum tubes...
. Using this, design was started on a set designated Gneis (Origin) and operating at 16 cm (1.8 GHz).
When the NII-9 was evacuated to Moscow in July 1941, this greatly affected the schedule. Also, the reflex klystron had not been put into production and its availability in the future was doubtful; therefore, the project was terminated. The need, however, for an airborne radio-location set was now even more important; the Pe-3, a heavy fighter aircraft and successor to the Pe-2, was in production. Some of these aircraft were being configured as night-fighters, and the radar (as it was now called) was urgently needed. The NII-20 and Factory 339 took up the design, led by the Technical Director, Victor Tikhomirov.
The new set, designated Gneis-2, operated at 1.5 m (200 MHz). The Pe-3 fighter was a two-place aircraft, with the pilot and the rear gunner/radio operator seated back to back. The radar was designed as another piece of equipment for the radio operator.
The antennas were mounted above the top surface of the wings, a broad-pattern transmitting array on one wing and two Yagi receiving antennas on the other. One Yagi was directed forward and the other, a few feet away, aimed outward 45 degrees. The fuselage of the aircraft provided a shield between the transmitting and receiving antennas. The system had a range of about 4 km and could give the target's azimuth relative to the fighter's flight path.
The Gneis-2, the first aircraft radar in the Soviet Union, was proven in combat at Stalingrad during December 1942. About 230 of these sets were built during the war. A few were installed on Yak-9 and (out of number sequence) Yak-3 aircraft, the advanced fighters that eventually gave the VVS parity with the Luftwaffe. Other sets with Gneis designations were developed at Plant 339 for experimental purposes, particularly with Lavochkin La-5 fighters and Ilyushin Il-2 ground-assault aircraft, but none of these sets were placed into production.
Naval
During the 1930s, the RKKF (Red Fleet) had major programs in developing radio communications. Starting in 1932, this activity was headed by Aksel Ivanovich BergAksel Berg
Aksel Ivanovich Berg was a Soviet scientist and Navy Admiral .Berg's father was General Johan Berg, of Finland-Swedish origin, and his mother was Italian. Aksel was 11 when his father died, and Aksel was matriculated to Saint Petersburg navy school...
Director of the NIIIS-KF, Red Fleet Signals Research) and later given the rank of Engineer-Admiral. He was also a Professor at Leningrad's universities and closely followed the early radio-location progress at the LPTI and NII-9. He started a research program in this technology at the NIIIS-KF, but was interrupted by being arrested in 1937 during the Great Purge and spent three years in prison.
Berg was released in early 1940 and reinstated in his positions. After reviewing the tests of Redut conducted at Sevastopol, he obtained a RUS-2 cabin and had it adapted for shipboard testing. Designated Redut-K, it was placed on the light cruiser Molotov in April 1941, making this the first warship in the RKKF with a radio-location capability. After the start of the war, only a few of these sets were built.
In mid-1943, radar (radiolokatsiya) was finally recognized as a vital Soviet activity. A Council for Radar, attached to the State Defense Committee, was established; Berg was made Deputy Minister, responsible for all radar in the USSR. While involved with all future developments in this activity, he took special interest in Navy systems. Berg was later mainly responsible for introducing cybernetics
Cybernetics
Cybernetics is the interdisciplinary study of the structure of regulatory systems. Cybernetics is closely related to information theory, control theory and systems theory, at least in its first-order form...
in the Soviet Union.
Other indigenous Soviet Navy radars developed (but not put into production) during the war included Gyuis-1, operating at 1.4 m with 80- kW pulse power. This was a successor to Redut-K for early warning; the prototype was installed on the destroyer Gromkii in 1944. Two fire-control radars were simultaneously developed: Mars-1 for cruisers and Mars-2 for destroyers. Both were tested just at the close of the war, and later placed into production as Redan-1 and Redan-2, respectively.
Germany
Germany has a long heritage of using electromagnetic waves for detecting objects. In 1888, Heinrich Hertz, who first demonstrated the existence of these waves, also noted that they, like light, were reflected by metal surfaces. In 1904, Christian Hülsmeyer obtaioned German and foreign patents for an apparatus, the Telemobilskop, uaing a spark gap transmitter that could detect ships and prevent collisions; this is often cited as the first radar, but, without directly providing range, it does not qualify for this classification. With the advent of the radio tube and electronics, other detection-only systems were developed, but all used continuous waves and could not measure distance.In 1933, physicist Rudolf Kühnhold
Rudolf Kühnhold
Rudolf Kühnhold was an experimental physicist who is often given credit for initiating research that led to the Funkmessgerät in Germany.-Early life:...
, Scientific Director at the Kriegsmarine (German Navy) Nachrichtenmittel-Versuchsanstalt (NVA—Experimental Institute of Communication Systems) in Kiel
Kiel
Kiel is the capital and most populous city in the northern German state of Schleswig-Holstein, with a population of 238,049 .Kiel is approximately north of Hamburg. Due to its geographic location in the north of Germany, the southeast of the Jutland peninsula, and the southwestern shore of the...
, initiated experiments in the 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...
region to measure the distance to a target. For the transmitter, he obtained assistance from two radio amateur operators, Paul-Gunther Erbslöh and Hans-Karl Freiherr von Willisen In January 1934, they formed a company, Gesellschaft für Elektroakustische und Mechanische Apparate (GEMA), for this work.
Development of a Funkmessgerät für Untersuchung (radio measuring device for reconnaissance) soon began in earnest at GEMA. Hans Hollmann
Hans Hollmann
Hans Erich Hollmann was a German electronic specialist who made several breakthroughs in the development of radar....
and Theodor Schultes, both affiliated with the prestigious Heinrich Hertz Institute in Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
, were added as consultants. The first development was a continuous-wave apparatus using Doppler-beat interference for detection. Kühnhold then shifted the GEMA work to a pulse-modulated system.
Using a 50 cm (600 MHz) magnetron from Philips
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
, their first transmitter was modulated with 2-μs pulses at a pulse repetition frequency
Pulse repetition frequency
Pulse repetition frequency or Pulse repetition rate is the number of pulses per time unit . It is a measure or specification mostly used within various technical disciplines Pulse repetition frequency (PRF) or Pulse repetition rate (PRR) is the number of pulses per time unit (e.g. Seconds). It...
(PRF) of 2000 Hz. The transmitting antenna was an array of 10 pairs of dipoles with a reflecting mesh, and the receiving antenna had three pairs of dipoles and incorporated 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...
. The wide-band regenerative receiver used an RCA 955 acorn triode. A blocking device (a duplexer), shut the receiver input when the transmitter pulsed. A Braum tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
was used for displaying the range. It was first tested at a NVA site at the Lübecker Bay near Pelzerhaken during May 1935, detecting returns from woods across the bay at a range of 15 km (9.3 mi). In Germany, Kühnhold is often called the "Father of radar".
This first Funkmessgerät from GEMA incorporated more advanced technologies than early sets in Great Britain and the United States, but it appears radar received a much lower priority until later in World War II; by the start of the war, few had been fielded. To a large part, this was due to the lack of appreciation of this technology by the military hierarchy, especially at the top where dictator Adolf Hitler
Adolf Hitler
Adolf Hitler was an Austrian-born German politician and the leader of the National Socialist German Workers Party , commonly referred to as the Nazi Party). He was Chancellor of Germany from 1933 to 1945, and head of state from 1934 to 1945...
looked on radar as a defensive weapon, and his interest was in offensive hardware. This problem was compounded by the lackadaisical approach to command staffing. It was some time before the Luftwaffe had a command and control system nearly as effective as the one set up by the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
in Great Britain before the war.
Wolfgang Martini
Wolfgang Martini
Wolfgang Martini was a Career Officer in the German Air Force, and largely responsible for promoting early radar development and utilization in that country.-Early career:...
, a career Luftwaffe officer, was the primary promoter of radar to the German High Command. Although not university educated, his grasp of this technology was instinctive and his involvement was perhaps the greatest impetus to the ultimate development of wartime radar in Germany. In 1941, he was elevated to General der Luftnachrichtentruppe (General of the Air Signal Corps) and remained in this position until the end of the war in May 1945.
There were three users of radar in Germany during the war: the Luftwaffe (Air Force), the Kriegsmarine (Navy), and the Heer (Army). Although a number of development laboratories were operated by these users, the vast majority of radars were supplied by four commercial firms: GEMA, Telefunken, Lorenz, and Siemens & Halske. Near the end of the war in 1945, GEMA led the German radar work, growing to over 6,000 employees.
The official designation of radar systems was FuMG, with most also with a letter (e.g., G, T, L, or S) indicating the manufacturer, as well as a number showning the year of release and possibly a latter or number giving the nodel. There was, however, a lack of uniformity in designations.
Ground and ship-based
In early 1938, the Kriegsmarine funded GEMA for the development of two systems, one a gun-laying set and the other an air-warning set. In production, the first type became the 80-cm (380-MHz) Flakleit, capable of directing fire on surface or air targets within a 80-km range. It had an antenna configuration very similar to the U.S. SCR-268. The fixed-position version, the Flakleit-G, included a height-finder.The second type developed by GEMA was the 2.5 m (120 MHz) Seetakt. Throughout the war, GEMA provided a wide variety of Seetakt sets, manly for ships but also for several types for U-boats. Most had an excellent range-measuring module called Messkette (measuring chain) that provided range accuracy within a few meters regardless of the total range. The shipboard Seetakt used a "mattress" antenna similar to the "bedspring" on the American CXAM.
Although the Kregsmarine attempted to keep the GEMA from working with the other services, the Luftwaffe became aware of the Seetakt and ordered their own version in late 1938. Called the Freya
Freya
In Norse mythology, Freyja is a goddess associated with love, beauty, fertility, gold, seiðr, war, and death. Freyja is the owner of the necklace Brísingamen, rides a chariot driven by two cats, owns the boar Hildisvíni, possesses a cloak of falcon feathers, and, by her husband Óðr, is the mother...
, this was a ground-based radar operating around 2.4 m (125 MHz) with 15-kW peak power giving a range of some 130 km. The basic Freya radar was continuously improved, with over 1,000 systems eventually built.
In 1940, Josef Kammhuber
Josef Kammhuber
Josef Kammhuber was a Career Officer in the German Air Force, and is best known as the first General of the Night Fighters in the Luftwaffe during World War II...
used Freyas in a new air-defense network extending through Holland, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. Called the Kammhuber Line
Kammhuber Line
The Kammhuber Line was the name given to the German night air defense system established in July 1940 by Colonel Josef Kammhuber.- Description :...
by the Allies, it was composed of a series of cells code-named Himmelbett (four-poster bed), each covering an area some 45 km wide and 30 km deep, and containing a radar, several searchlights, and a primary and backup night-fighter aircraft. This was relatively effective except when the sky was overcast. A new gun-directing radar was needed to cover this deficiency and the Luftwaffe then contracted with Telefunken for such a system.
Under the leadership of Wilhelm Runge
Wilhelm Runge
Wilhelm Tolmé Runge was an electrical engineer and physicist who had a major involvement in developing radar systems in Germany.-Early life:...
, the new radar was built by Telefunken around a new triode capable of delivering 10-kW pulse power at 60 cm (500 MHz). Code-named Würzburg
Würzburg radar
The Würzburg radar was the primary ground-based gun laying radar for both the Luftwaffe and the German Army during World War II. Initial development took place before the war, entering service in 1940. Eventually over 4,000 Würzburgs of various models were produced...
, this had a 3-m (10-ft) parabolic reflector supplied by the Zeppelin Company and was effective at a range of about 40 km for aircraft. Two of these radars were normally added to each Himmelbett, one to pick up the target from a Freya and a second to track the fighter aircraft. Requiring only one operator, the Würzburg came to be the primary mobile, gun-laying system used by the Luftwaffe and Heer during the war. About 4,000 of the various versions of the basic system were eventually produced.
The Air Defense System was continually upgraded. To improve the range and accuracy, Telefunken developed the Würzburg-Riese and GEMA enlarged the Freya dipoles to make the Mammut and the Wassermann, The Würzburg-Riese (Giant Würzburg) had a 7.5-m (25-foot) dish (another product from Zeppelin) that was mounted on a railway carriage. The system also had an increased transmitter power; combined with the enlarged reflector, this resulted in a range of up to 70 km, as well as greatly increased accuracy. About 1,500 of this radar system were built.
The Mammut (Mammoth) used 16 Freyas linked into a giant 30- by 10-meter (100- by 33-foot) antenna with phased-array beam-directing, a technique that would eventually become standard in radars. It had a range up to 300 km and covered some 100 degrees in width with an accuracy of near 0.5 degree. About 30 sets were built, some with back-to-back faces for bi-directional coverage. The Wassermann (Waterman), had eight Freyas also with phased-array antennas, stacked on a steerable, 56-meter (190-foot) tower and giving a range up to 240 km. A variant, Wassermann-S, had the radars mounted on a tall cylinder. About 150 of all types were built starting in 1942.
A system with great range was needed to track the British and American bomber formations as they crossed Germany. For this function, consultants Theodor Schultes and Hans Hollmann
Hans Hollmann
Hans Erich Hollmann was a German electronic specialist who made several breakthroughs in the development of radar....
designed an experimental 2.4-m (125-MHz), 30-kW radar called Panorama. Built by Siemens & Halske in 1941, it was placed atop a concrete tower at Tremmen, a few kilometers south of Berlin. The antenna had 18 dipoles on a long, horizontal support and produced a narrow vertical beam; this rotated at 6 rpm to sweep out 360-degrees of coverage to about 110 km.
Based on the operation of Panorama, Siemens & Halske improved this system, and renamed it Jagdschloss (Hunting Lodge). They added a second switchable operation to 150 kW at 1.2 m (250 MHz), increasing the range to near 200 km. The information from the receivers was sent via co-axial cable or a 50-cm link from the tower to a central command center, where it was used to direct fighter aircraft. Hollmann's polar-coordinate (PPI) CRT was used in the display, the first German system with this device; it was also added to the Panorama. The Jagdschloss entered service in late 1943, and about 80 systems were eventually built. The Jagdwagen was a mobile, single-frequency version; operating at 54 cm (560 MHz), it had a correspondingly smaller antenna system.
Under an internally funded project, the firm Lorenz AG developed a pulse-modulated set. The Heer contracted for a few sets for Flak (anti-aircraft) support, but then this mission was transferred to the Luftwaffe. Over several years, Lorenz was unsuccessful in selling new versions called Kurfürst and Kurmark (both Holy Roman Imperial
Holy Roman Empire
The Holy Roman Empire was a realm that existed from 962 to 1806 in Central Europe.It was ruled by the Holy Roman Emperor. Its character changed during the Middle Ages and the Early Modern period, when the power of the emperor gradually weakened in favour of the princes...
terms). As the war continued, a need was seen by the Luftwaffe for additional radars. Lorenz again modified their sets to become the Tiefentwiel, a transportable system built to complement the Freya against low-flying aircraft, and the Jagdwagen, a mobile unit used for air surveillance. These 54-cm (560-MHz) units with plan-position indicators, had two antennas backed by parabolic, mesh reflectors on rotatable, forked frames that lifted above the equipment cabin. Starting in 1944, both of these systems were produced by Lorenz for the Luftwaffe in relatively small numbers.
Although German researchers had developed magnetrons since the early 1930s (Hans Hollmann received a U.S. patent on his device in July 1938), none had been suitable for military radars. In February 1943, a British bomber containing a H2S
H2S radar
H2S was the first airborne, ground scanning radar system. It was developed in Britain in World War II for the Royal Air Force and was used in various RAF bomber aircraft from 1943 to the 1990s. It was designed to identify targets on the ground for night and all-weather bombing...
radar was shot down over Holland, and the 10-cm magnetron was found intact. In short order, the secret of successful magnetrons was discovered, and microwave radar development started.
Telefunken was commissioned to build a gun-laying set for Flak applications, and at the beginning of 1944, a 10-cm set code-named Marback emerged. Using a 3-m Mannheim reflector, this set had a detection range of about 30 km. Its most important characteristic was a relative immunity to Window – the chaff used by the British as a countermeasure
Countermeasure
A countermeasure is a measure or action taken to counter or offset another one. As a general concept it implies precision, and is any technological or tactical solution or system designed to prevent an undesirable outcome in the process...
against the 50-cm Würzburg. The Marback was produced in limited quantities for Flak batteries around a number of large industrial cities.
Several other 10-cm sets were developed, but none made it into mass production. One was Jagdschloss Z, a Panorama-type experimental set with 100-kW pulse-power built by Siemens & Halske. Klumbach was a similar set but with only 15-kW pulse-power and using a cylindrical parabolic reflector to produce a very narrow beam; when used with Marbach, the combined fire-control system was called Egerland.
Near the end of 1943, the Germans also salvaged radars containing 3-cm magnetrons, but sets operating at this wavelength were never produced. They did, however, play an important role in the German development of countermeasures, particularly radar warning receiver
Radar warning receiver
Radar warning receiver systems detect the radio emissions of radar systems. Their primary purpose is to issue a warning when a radar signal that might be a threat is detected. The warning can then be used, manually or automatically, to evade the detected threat...
s.
Airborne
In June 1941, an RAF bomber, equipped with an ASV (Air-to-Surface Vessel) Mk II radar, made an emergency landing in France. Although the crew had attempted to destroy the set, the remains were sufficient for the German Laboratory for AviationGerman Aerospace Center
The German Aerospace Center is the national centre for aerospace, energy and transportation research of the Federal Republic of Germany. It has multiple locations throughout Germany. Its headquarters are located in Cologne. It is engaged in a wide range of research and development projects in...
to discern the operation and its function. Tests indicated the merits of such a radar, and Wolfgang Martini also saw the value and tasked Lorenz to develop a similar system.
With backgrounds in aircraft navigation equipment and experience in developing their internally funded ground-radar systems, Lorenz had excellent capabilities for this project.
Before the end of the year, they had built a set based on their Kurfürst/Kurmark design, but greatly reduced in size and weight, and with improved electronics. Called Hohentwiel, it produced 50-kW pulse-power at 55 cm (545 MHz) and had a very low PRF of 50 Hz. The set used two separate antenna arrangements, providing searching either forward or side-looking.
The Hohentwiel was demonstrated in detecting a large ship at 80 km, surfaced submarine at 40 km, submarine periscope at 6 km, aircraft at 10 to 20 km, and land features at 120 to 150 km. A bearing accuracy of about 1 degree was obtained by rapidly switching between two receiver antennas aimed 30 degrees on each side of the transmitter antenna direction. Put into production in 1942, the Hohentwiel was highly successful. It was first used on large reconnaissance aircraft. In 1943, the Hohentwiel-U, an adaptation for use on submarines, provided a range of 7 km for surface vessels and 20 km for aircraft. Altogether, some 150 sets per month were delivered.
The use of the accurate Freya and Würzburg radars in their air-defense systems allowed the Germans to have a somewhat less vigorous approach to the development of airborne radar. Unlike the British, whose inaccurate CH systems demanded some sort of system in the aircraft, the Würzburg was accurate enough to allow them to leave the radar on the ground. This came back to haunt them when the British figured out their Himmelbett operation, and the development of an airborne system became much more important.
In early 1941, Air Defense recognized the need for radar on their night-fighter aircraft. The requirements were given to Runge at Telefunken, and by the summer a prototype system was tested. Code-named Lichtenstein, this was a 62-cm (485-MHz), 1.5-kW system, generally based on the technology now well established by Telefunken for the Würzburg. The design problems were reduction in weight, provision of a good minimum range (very important for air-to-air combat), and an appropriate antenna design. An excellent minimum range of 200 m was achieved by carefully shaping the pulse. The antenna array had four dipoles with reflectors, giving a wide searching field and a typical 4-km maximum range (limited by ground clutter and dependent on altitude). A rotating phase-shifter was inserted in the transmission lines to produce a twirling beam. The elevation and azimuth of a target relative to the fighter were shown by corresponding positions on a CRT display.
The first production sets (Lichtenstein B/C) became available in February 1942, but were not accepted into combat until September. In general, pilots found a disadvantage to having this radar: it required large antennas that aerodynamically slowed the planes as much as 50 km/h. In May 1943, a B/C-equipped fighter aircraft landed in Scotland; it had flown the wrong way against a directional beacon. The British immediately recognized that they already had an excellent countermeasure in Window (the chaff used against the Würzburg); in a short time the B/C was greatly reduced in usefulness.
Although Telefunken had not been previously involved with radars of any type for fighter aircraft, in 1944 they started the conversion of a Marbach 10-cm set for this application. Downed American and British planes were scavenged for radar components; of special interest were the swiveling mechanisms used to scan the beam over the search area. An airborne set code-named Berlin was completed in January 1945, and about 40 sets were built and placed on night-fighter aircraft. A few sets, code named Berlin-S, were also built for shipboard surveillance.
Japan
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
, that Japan placed into service its first full radar system. In August 1942, U.S. marines captured one of these first systems, and, although crude even by the standards of early U.S. radars, the fact the Japanese had any radar capability came as a surprise. Japanese radar technology was 3 to 5 years behind that of America, Great Britain, and Germany throughout the war.
A major leader in early technology development was Hidetsugu Yagi
Hidetsugu Yagi
Hidetsugu Yagi was a Japanese electrical engineer. When working at Tohoku University, he wrote several important articles that introduced a new antenna design by his colleague Shintaro Uda to the English-speaking world.The Yagi antenna, patented in 1926, allows directional communication using...
, a professor and researcher of international status. His papers in the late 1920s on antennas and magnetron design were closely studied by scientists and engineers worldwide. He was allowed no part, however, in developing Japan's wartime radars. His earlier work was given so little attention by the Japanese military that, when they received a captured British radar set, at first they were unaware that the "Yagi
Yagi antenna
A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antenna consisting of a driven element and additional parasitic elements...
" mentioned in accompanying notes referred to a Japanese invention.
Although Japan had joined Nazi Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...
and Fascist Italy
Kingdom of Italy (1861–1946)
The Kingdom of Italy was a state forged in 1861 by the unification of Italy under the influence of the Kingdom of Sardinia, which was its legal predecessor state...
in a Tripartite Pact
Tripartite Pact
The Tripartite Pact, also the Three-Power Pact, Axis Pact, Three-way Pact or Tripartite Treaty was a pact signed in Berlin, Germany on September 27, 1940, which established the Axis Powers of World War II...
in 1936, there had been essentially no exchange of technical information. This changed in December 1940 when a group of Japanese representing Army technology was allowed to visit Germany, followed in January by a similar group from the Navy. In the visit, the Japanese were shown some German radars and a British MRU (their earliest searchlight-control radar), left behind during the Dunkirk evacuation. In addition, German-educated Yoji Ito
Yoji Ito
was an engineer and scientist that had a major role in the Japanese development of magnetrons and the Radio Range Finder .-Early years:...
, leader of the Navy delegation, was able to obtain information from the host on the MRU's pulsed operation. Ito immediately sent this information home by diplomatic courier, and work was started by the Navy on Japan's first true radar.
After war was started with the United States in December 1941, the Germans shipped a Würzburg radar to Japan. The submarine carrying this equipment was sunk on the way, and a second set met the same fate; however, some key hardware and documentation, sent on a separate vessel, made it safely.
When Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
was taken in February 1942, the remains of what turned out to be a British GL Mk-2 radar and a Searchlight Control (SLC) radar were found. Along with the hardware, there was a set of hand-written notes, giving details of the theory and operation of the SLC. At Corregidor
Corregidor
Corregidor Island, locally called Isla ng Corregidor, is a lofty island located at the entrance of Manila Bay in southwestern part of Luzon Island in the Philippines. Due to this location, Corregidor was fortified with several coastal artillery and ammunition magazines to defend the entrance of...
the following May, the captors found two U.S. Army radars, an SCR-268 in operating condition and a heavily damaged SCR-270. In a rare cooperative effort, the Army and Navy jointly conducted reverse engineering
Reverse engineering
Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation...
on these sets.
About 7,250 radar sets of 30 different types were developed for the Army and Navy. See List of Japanese World War II radar.
Imperial Army
The Tama Technology Research Institute (TTRI) was formed by the Army to lead in what was called Radio Range-Finder (RRF) development. TTRI was staffed with competent personnel, but most of their developmental work was done by contractors at the research laboratories of Toshiba Shibaura Denik (ToshibaToshiba
is a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...
) and Nippon Electric Company (NEC
NEC
, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
).
The TTRI established a system for designating the Army radar equipment, based on its use. The prefixes were Ta-Chi (written herein as Tachi) for land-based systems, Ta-Se for shipborne systems, and Ta-Ki for airborne systems. The "Ta" denoted Tama, the "Chi" was from tsuchi (earth), the "Se" means mizu (water) rapids, and "Ki" was from kuki (air).
In June 1942, both NEC and Toshiba started projects based on the SCR-268. The American system operated at 1.5 m (200 MHz). It had a very complex set of three antennas on a horizontal, rotatable boom and used lobe- switching. The NEC project was for a target-tracking system designated Tachi-1, essentially a copy of the SCR-268. The duplication of this system was found to be too difficult, and Tachi-1 was soon abandoned. At Toshiba, the project was also for a target-tracking system designated Tachi-2. This was to incorporate many simplifications to the SCR-268. Preliminary tests showed that it would be too fragile for field operation; this project was also abandoned.
The British GL Mk 2 was much less complicated than the SCR-268 and was easily reverse engineered; in addition, the notes on the SLC were available. From this came the Tachi-3, a ground-based tracking radar. This included many significant changes to the original British system; foremost were a change to a fixed-location configuration and a totally different antenna system.
The Tachi-3 transmitter operated at 3.75 m (80 MHz), and produced about 50-kW peak power, with 1- to 2-ms pulse width and 1- or 2-kHz PRF. The transmitter was designed for enclosure in an underground shelter. It used a Yagi antenna that was rigidly mounted above the shelter and the entire unit could be rotated in azimuth. By phasing the antenna elements, some elevation change could be attained.
The receiver for Tachi-3 was located in another underground shelter about 30-m distance from the transmitter. Four dipole antennas were mounted on orthogonal arms, and the shelter and antennas rotated to scan in azimuth. The maximum range was about 40 km. NEC built some 150 of these sets, and they finally entered service in early 1944.
The follow-on project at Toshiba was designated Tachi-4. This was for a ground-based tracking radar, again using the SCR-268 as a pattern. Still with the original 1.5 m (200 MHz) operation, this set performed reasonably well, and about 70 sets were produced. These began service in mid-1944; however, by then the Tachi-3 was available and was superior in performance.
Engineers at Toshiba had already begun work on a pulse-modulated system. With the arrival of the damaged SCR-270, portions were incorporated into the ongoing development of a fixed-site, early-warning system designated Tachi-6. The transmitter operated in the 3- to 4-m (100- to 75-MHz) band with a peak power of 50 kW. It used a dipole-array antenna atop a tall pole. Multiple receiver stations were spaced about 100 m around the transmitter. Each of these had a hand-rotated pole with Yagi antennas at two levels, allowing azimuth and elevation measurements. One receiver station could track an aircraft while the others were searching. Ranges up to 300 km were attained and shown on a CRT display. This went into service in early 1943; about 350 Tachi-6 systems were eventually built.
A transportable version of this early-warning system was added. Designated Tachi-7, the primary difference was that the transmitter with a folding antenna was on a pallet. About 60 of these were built. This was followed in 1944 with the Tachi-18, a much lighter, further simplified version that could be carried with troops. Several hundred of these "portable" sets were built, and a number were found as the Japanese vacated distant occupied territory. All of these continued to operate in the 3- to 4-m band.
Other land-based radars developed by the Imperial Army included two height-finder sets, Tachi-20 and Tachi-35, but they were too late to be put into service. There was also Tachi-28, a radar-based aircraft guidance set. The TTRI also developed the Tachi-24, their slightly modified version of the German Würzburg radar, but this was never put into production.
The Imperial Army had its own ships, ranging in size from attack motorboats to large landing crafts. For these, they developed Tase-1 and Tase-2, both anti-surface radars. The Imperial Army also had its own Air Divisions with fighters, bombers, transports, and reconnaissance aircraft. Only two systems were developed for these aircraft: Taki-1, an airborne surveillance radar in three models, and Taki-11, an airborne electronic countermeasures (ECM) set.
Imperial Navy
The Naval Technical Research Institute (NTRI) began work on a pulse-modulated system in August 1941, even before Yoji Ito returned from Germany. With assistance from NECNEC
, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
(Nippon Electric Company) and the Research Laboratory of NHK
NHK
NHK is Japan's national public broadcasting organization. NHK, which has always identified itself to its audiences by the English pronunciation of its initials, is a publicly owned corporation funded by viewers' payments of a television license fee....
(Japan Broadcasting Corporation), a prototype set was developed on a crash basis. Kenjiro Takayanagi
Kenjiro Takayanagi
was a Japanese pioneer in the development of television. Although he failed to gain much recognition in the West, he built the world's first all-electronic television receiver, and is referred to as "the father of Japanese television".-Career:...
, Chief Engineer of NHK, developed the pulse-forming and timing circuits as well as the receiver display. The prototype was tested in early September.
The system, Japan's first full radar, was designated Mark 1 Model 1. (This type of designation is shortened herein to the numbers only; e.g., Type 11.) The system operated at 3.0 m (100 MHz) with a peak-power of 40 kW. Dipole arrays with mat-type reflectors were used in separate antennas for transmitting and receiving. In November 1941, the first manufactured Type 11 was placed into service as a land-based early-warning radar on the Pacific coast. A large system, it weighed close to 8,700 kg. Some 30 sets were built and used throughout the war. The detection range was about 130 km for single aircraft and 250 km for groups.
Type 12, another land-based early-warning system, followed during 1942. It was similar to its predecessor but lighter in weight (about 6,000 kg) and on a movable platform. Three versions were made; they operated at either 2.0 m (150 MHz) or 1.5 m (200 MHz), each with a peak-power of only 5 kW. The lower power significantly reduced the range. About 50 sets of all versions of these systems were built.
Another similar system was the Type 21. Fundamentally, it was the 200-MHz version of the Type 12 redesigned for shipboard use and weighing only about 840 kg. The first sets were installed on the battleships Ise and Hyuga in April 1942. About 40 sets were eventually built.
In this same time period, the more use-flexible Type 13 was also being designed. Operating at 2.0 m (150 MHz) and with a peak power of 10 kW, this set included a major advancement. A unit duplexer had been developed to allow the use of a common antenna. With a weight of 1,000 kg (a small fraction of that of the Type 11), this system could be readily used on shipboard as well as at land stations. Its detection range was about the same as the Type 12. It was placed into service in late 1942, and by 1944 it had also been adapted for use on surfaced submarines. With some 1,000 sets eventually being built, the Type 13 was by far the most used air- and surface-search radar of the Imperial Navy.
The Type 14 was a shipboard system designed for long-range, air-search applications. With a peak power of 100 kW and operating at 6 m (50 MHz), this weighed a huge 30,000 kg. Only two of these systems were placed in service in May 1945, just at the end of the war.
The Imperial Navy built two radars based on the captured SCR-268. The Type 41 was electronically like the original, but with two large dipole array antennas and configured for shipboard, fire-control applications. About 50 of these were built, and it went into service in August 1943. The Type 42 had more revisions, including a change to using four Yagi antennas. Some 60 were built and put into service in October 1944. Both systems had a range of about 40 km.
The NTRI made minimal changes to the 60-cm (500-MHz) Würzburg, mainly converting the oscillator from vacuum tubes to a magnetron. The result was the Type 23 anti-ship, fire-control radar intended for cruisers and larger ships. With the change to a magnetron, the output was approximately halved to a peak-power of about 5 kW; this gave a range of only 13 km for detecting most surface ships. Although the prototype was completed in March 1944, only a few sets were built, and it was never put into serial production.
Japan Radio Company
Japan Radio Company
is a Japanese company specialising in the field of wireless electronics for the communications industry.- History :Established in 1915, the company has produced a wide variety of products including marine electronics, measuring equipment for telecommunications, broadcast radio equipment, and...
(JRC) had long worked with the NTRI in developing magnetrons. In early 1941, JRC was given a contract by NTRI to design and build a microwave surface-detection system for warships. Designated Type 22, this used a pulse-modulated, 10-cm (3.0-GHz) magnetron with water-cooling and producing 2-kW peak-power. The receiver was a super-heterodyne type with a low-power magnetron serving as the local oscillator. Separate horn antennas were used for transmitting and receiving. These were mounted on a common platform that could be rotated in the horizontal plane. Since it was Japan's first full set using a magnetron, Yoji Ito was made responsible and gave it special attention.
The prototype for the Type 22 was completed in October 1941; tests showed that it detected single aircraft at 17 km, groups of aircraft at 35 km, and surface ships at over 30 km (depending on the height of the antenna above the sea). The first Japanese warships with microwave radar received these in March 1942, and by late 1944, microwave radar was widely in use on surface vessels and submarines; about 300 Type 22 sets were built.
With the poor range of the Type 23 (the Würzburg copy), development was started on three microwave systems for fire-control applications. The Type 31 operated at 10 cm (3 GHz) and, like the Würzburg, used a common parabolic reflector. While the prototype could detect larger ships at up to 35 km, it was not completed until March 1945 and was never placed into production.
The Type 32 was another 10-cm system, this one having separate square-horn antennas. Detection range for large ships was about 30 km. It became operational in September 1944, and some 60 sets were produced. Type 33 was still another 10-cm set; this one used separate round-horn antennas. The prototype was completed in August 1944, but like the Type 23, detection range was only 13 km and it was not put into production.
The Imperial Navy had a large number of aircraft. It was almost a year after the start of the war, however, before the first airborne set was developed at the Oppama Naval Air Technical Depot (ONATD). Initially designated Type H-6 with a number of experimental sets built, this was eventually produced as the Type 64 and began service in August 1942. The greatest developmental problem was in bringing the weight down to that allowable for an aircraft; 110 kg was eventually achieved.
Intended for both air- and surface-search, the Type 64 operated at 2 m (150 MHz) with a peak power of 3 to 5 kW and a pulse width of 10 ms. It used a single Yagi antenna in the nose of the aircraft and dipoles on each side of the fuselage, and could detect large surface vessels or flights of planes at up to 100 km. This set was initially used on H8K-class 4-engine flying boats, then later on a variety of mid-sized attack planes and torpedo bombers. It was by far the most used airborne radar, with about 2,000 sets produced.
Development continued on lighter-weight systems at the ONATD. The Type N-6 weighing 60 kg was available in October 1944, but only 20 sets were built. This was a 1.2-m (250-MHz), 2-kW experimental set intended for a single-engine, 3-place (pilot, gunner, and radar operator) fighter aircraft. Another was the Type FM-3; operating at 2 m (150 MHz) with 2-kW peak-power, this weighed 60 kg and had a detection range up to 70 km. Specifically designed for the Kyūshū Q1W
Kyushu Q1W
-References:NotesBibliography* Francillon, Ph.D., René J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1979. ISBN 0-370-30251-6.-External links:*...
Tokai, a new 2-engine 3-place anti-submarine aircraft, about 100 sets were built, going into service in January 1945.
With assistance from the NTRI and Yoji Ito, the ONATD also developed Japan's only airborne microwave radar. Designated FD-2 (sometimes FD-3), this was a magnetron-based, 25-cm (1.2-GHz), 2-kW set weighing about 70 kg. It could detect aircraft at a range between 0.6 and 3 km, satisfactory for close-range night-fighter aircraft such as the Nakajima J1N1-S
Nakajima J1N
-See also:-Bibliography:* Francillon, Réne J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1970 . ISBN 0-370-30251-6....
Gekko. It used four Yagi antennas mounted in the nose area; separate elements for transmit and receive were skewed for searching. Unlike in the air warfare in Europe, there were few night-fighter aircraft used by Japan; consequently, it was mid-1944 before the Type FD-2 was put into use. Some 100 sets were manufactured.
When magnetrons were being developed in Japan, the initial primary application was intended to be power transmission, not radar. As these devices increased in output energy, their application for a weapon became apparent. For research in special weapons, a large facility was built in Shimada. In 1943, a project in developing a Ku-go (Death Ray) using magnetrons began. By the end of the war, magnetrons developing 100 kW continuous power at 75 cm (400 MHz) had been built, and the intent was apparently to couple 10 of these to produce a beam of 1,000 kW. Essentially all of the equipment and documents at Shimada were destroyed before the Americans reached the facility.
Commonwealth Nations
When war with Germany was believed to be inevitable, Great Britain shared its secrets of RDF (radar) with the Commonwealth Nations – the dominionDominion
A dominion, often Dominion, refers to one of a group of autonomous polities that were nominally under British sovereignty, constituting the British Empire and British Commonwealth, beginning in the latter part of the 19th century. They have included Canada, Australia, New Zealand, Newfoundland,...
s of Australia, Canada, New Zealand, and South Africa – and asked that they develop their own capabilities for indigenous systems. After Germany invaded Poland in September 1939, Great Britain and the Commonwealth Nations declared war with Germany. Within a short time, all four of the Commonwealth Nations had locally designed radar systems in operation, and most continued with developments throughout the war.
Australia
After Australia declared war on Germany in September 1939, the Council for Scientific and Industrial Research established the Radiophysics Laboratory (RPL) at the University of SydneyUniversity of Sydney
The University of Sydney is a public university located in Sydney, New South Wales. The main campus spreads across the suburbs of Camperdown and Darlington on the southwestern outskirts of the Sydney CBD. Founded in 1850, it is the oldest university in Australia and Oceania...
to consuct radar research. Led by John H. Piddington, their first project produced a shore-defense system, designated ShD, for the Australian Army
Australian Army
The Australian Army is Australia's military land force. It is part of the Australian Defence Force along with the Royal Australian Navy and the Royal Australian Air Force. While the Chief of Defence commands the Australian Defence Force , the Army is commanded by the Chief of Army...
. This was followed by the AW Mark 1, an air-warning system for the Australian Air Force. These both operated at 200 MHz (1.5 m).
War on Japan began in December 1941, and Japanese planes attacked Darwin, Northern Territory
Darwin, Northern Territory
Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 127,500, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities...
the following February. The New South Wales Railways Engineering Group was asked by the RPL to design a lightweight antenna for the air warning radar. From this, the LW/AW Mark II resulted; about 130 of these air-transportable sets were built and used by the United States and Australian military forces in the early island landings in the South Pacific, as well as by the British in Burma.
American troops arriving in Australia in 1942–43, brought many SCR-268 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....
systems with them. Most of these were turned over to the Australians, who rebuilt them to become Modified Air Warning Devices (MAWDs). These 200-MHz systems were deployed at 60 sites around Australia. During 1943–44, the RPL involved a staff of 300 persons working on 48 radar projects, many associated with improvements on the LW/AW. Height-finding was added (LW/AWH), and complex displays converted it into a ground-control intercept system (LW/GCI). There was also a unit for low-flying aircraft (LW/LFC). Near the end of the war in 1945, the RPL was working on a microwave height-finding system (LW/AWH Mark II).
Canada
Of the four Commonwealth Nations, Canada had by far the most extensive wartime involvement in radar. The major responsibility was with the National Research Council of CanadaNational Research Council of Canada
The National Research Council is an agency of the Government of Canada which conducts scientific research and development.- History :...
(NRCC), specifically its Radio Branch headed by John Tasker Henderson
John Tasker Henderson
John Tasker Henderson was a Canadian Physicist whose career was with the National Research Council . He is particularly recognized for his leadership role in radar technology during World War II....
. Their first effort was in developing a surface-warning system for the Royal Canadian Navy
Royal Canadian Navy
The history of the Royal Canadian Navy goes back to 1910, when the naval force was created as the Naval Service of Canada and renamed a year later by King George V. The Royal Canadian Navy is one of the three environmental commands of the Canadian Forces...
(RCN) to protect the Halifax Harbour
Halifax Harbour
Halifax Harbour is a large natural harbour on the Atlantic coast of Nova Scotia, Canada, located in the Halifax Regional Municipality.-Harbour description:The harbour is called Jipugtug by the Mi'kmaq first nation, anglisized as Chebucto...
entrance. Called Night Watchman (NW), this 200-MHz (1.5-m), 1-kW set was completed in July 1940.
In September 1940, on their trip to the United States for cooperative exchanges, 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...
visited Canada and recommended that Great Britain use Canadian personnel and facilities to supplement the British programs. Research Enterprises, Ltd. (REL), was then established to manufacture radar and optical equipment.
The next system was a ship-borne set designated Surface Warning 1st Canadian (SW1C) for corvettes and merchant ships The basic electronics were similar to the NW, but it initially used a Yagi antenna that was turned using an automobile steering wheel. It was first tested at sea in mid-May 1941. The project engineer from the NRCC was H. Ross Smith, who remained in charge of projects for the RCN throughout the war.
In early 1942, the frequency of the SW1C was changed to 215 MHz (1.4 m) and an electric drive was added to rotate the antenna. It was known as the SW2C and produced by the REL for corvettes and mine sweepers. A lighter version, designated SW3C, followed for small vessels such as motor torpedo boats. A plan-position indicator (PPI) display was added in 1943. Several hundred SW sets were eventually produced by the REL.
For coastal defense by the Canadian Army, a 200-MHz set with a transmitter similar to the NW was developed. Designated CD, it used a large, rotating antenna atop a 70-foot wooden tower. Since the firing battalion would be some distance away, a "displace corrector" automatically compensated for this separation. The CD was put into operation in January 1942
Following the Tizard Mission meetings in Washington, it was decided that Canada would build a microwave gun-laying system for the Canadian Army. This 10-cm (3-GHz) system was designated GL IIIC, the "C" to distinguish it from similar systems being developed in America ("A") and Great Britain "B"). (Eventually the U.S. system was the SCR-584.) A local source of magnetrons was vital, and the National Electric Company (NEC) in Montreal began manufacturing these devices.
The GL IIIC was housed in two trailers, one with a rotating cabin and one fixed. The rotating one was called the Accurate Position Finder and held the primary equipment and separate antennas with parabolic reflectors for transmitting and receiving. The other trailer carried the Zone Position Indicator, a 150-MHz (2-m) radar that found the position of all aircraft within the system's coverage.
In mid-1941, the REL received orders for 660 GL IIIC systems. In July, a very satisfactory demonstration of the prototype system was held, and by December, the first six systems had been built. During 1942 and into the next year, there were many technical and administrative problems Then in September 1943, a decision was made to use the British and American systems in liberating Europe; thus, the large REL order was never filled.
Success at the Radio Branch with the 10-cm experimental set for the Army led the RCN to request a ship-borne, early-warning microwave set. A separate Microwave Section was formed and development of a 10-cm (3-GHz) set designated RX/C was initiated in September 1941. Due to many changes in requirements from the RCN, the first sets were not available until July 1943. The RX/C incorporated many of the characteristics of the SW sets, but had a PPI display and a parabolic-reflector antenna. Further sets were produced by the REL and used throughout the war.
The Admiralty in Great Britain asked about Canada's interest and capability in manufacturing 3-cm magnetrons. This led to the development of a 3-cm device by the NEC and a full 3-cm (10-GHz) radar for small crafts. In May 1942, the British Admiralty gave a formal purchase order for these developments. The set was designated Type 268 (not to be confused with the SCR-268 from the U.S. Signal Corps), and was particularly designed to detect a submarine snorkel
Submarine snorkel
A submarine snorkel is a device which allows a submarine to operate submerged while still taking in air from above the surface. Navy personnel often refer to it as the snort.-History:...
. With extensive testing and subsequent changes, full-scale production did not start until December 1944. About 1,600 Type 268 sets were manufactured before the end of the war.
While the Canadian Army was basically satisfied with the 200-MHz CD systems, they did ask for an improvement to 10-cm operation. Since the Microwave Section was then well experienced in these systems, they easily provided a design. Before even a prototype was built, the Army gave an order to the REL for a number of sets designated CDX. Production started in February 1943, but only 19 sets were actually delivered with 5 of these going to the USSR,.
In the spring of 1943, German submarines started operating just outside the Saint Lawrence Seaway
Saint Lawrence Seaway
The Saint Lawrence Seaway , , is the common name for a system of locks, canals and channels that permits ocean-going vessels to travel from the Atlantic Ocean to the North American Great Lakes, as far as Lake Superior. Legally it extends from Montreal to Lake Erie, including the Welland Canal...
– the primary ship route from Canada to Great Britain. To counter this, the Royal Canadian Air Force
Royal Canadian Air Force
The history of the Royal Canadian Air Force begins in 1920, when the air force was created as the Canadian Air Force . In 1924 the CAF was renamed the Royal Canadian Air Force and granted royal sanction by King George V. The RCAF existed as an independent service until 1968...
(RCAF) asked that 12 sets of a long-range microwave system be built. A magnetron producing 300 kW at 10.7 cm (2.8 GHz) was developed by the firm NEC. For radiating a narrow horizontal beam to sweep the sea surface, a slotted antenna 32 by 8 feet in size was designed by William H. Watson at McGill University
McGill University
Mohammed Fathy is a public research university located in Montreal, Quebec, Canada. The university bears the name of James McGill, a prominent Montreal merchant from Glasgow, Scotland, whose bequest formed the beginning of the university...
. The system was designated MEW/AS (Microwave Early Warning Anti Submarine).
The transmitting and receiving equipment was located behind the antenna, and the assembly could be rotated at up to 6 RPM. The controls and PPI display was in a nearby fixed building. This could detect targets at up to 120-miles (196-km) range. A second version, designed for detecting high-flying aircraft, was designated MEW/HF (Height Finding). In this, the power could be switched to a smaller, rotating antenna that gave a narrow vertical beam. The RCAF put both versions of the MEW into operation at several sites in Newfoundland, Quebec, and Ontario.
In addition to the radar sets previously described, many others were designed at the NRCC's Radio Branch during the war years – a total of 30 of all types. Of these, 12 types were turned over to the REL where they were built in quantities varying from a few to hundreds; altogether, some 3,000 were produced before the REL was closed in September 1946.
New Zealand
In late 1939, the New Zealand Department of Scientific and Industrial Research (DSIR) established two facilities for RDF development – one, led by Charles Watson-Munro was at the Radio Section of the Central NZ Post Office in WellingtonWellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...
, and the other, under the responsibility of Frederick White, was at Canterbury University College
University of Canterbury
The University of Canterbury , New Zealand's second-oldest university, operates its main campus in the suburb of Ilam in the city of Christchurch, New Zealand...
in Christchurch
Christchurch
Christchurch is the largest city in the South Island of New Zealand, and the country's second-largest urban area after Auckland. It lies one third of the way down the South Island's east coast, just north of Banks Peninsula which itself, since 2006, lies within the formal limits of...
.
The objective of the Wellington group was to develop land-based and airborne RDF sets for detecting incoming vessels and a set to assist in gun-directing at coastal batteries. Within a few months, they had converted a 180-MHz (1.6-m), 1-kW transmitter from the Post Office to be pulse-modulated and used it in a system called CW (Coastal Watching). The CW was followed by a similar, improved system called CD (Coast Defense); it used a CRT for display and had lobe-switching on the receiving antenna. This was placed into service at the Devonport Naval Base
Devonport Naval Base
Devonport Naval Base is the home of the Royal New Zealand Navy, located at Devonport, New Zealand on Auckland's North Shore. It is currently the only base of the navy that operates ships, and was a navy base from as far back as 1841...
at Auckland
Auckland
The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...
. In this same period, a partially completed ASV 200-MHz set from Great Britain was made into an airborne set for the Royal New Zealand Air Force
Royal New Zealand Air Force
The Royal New Zealand Air Force is the air arm of the New Zealand Defence Force...
(RNZAF). About 20 sets were built and put into service. All three of these radars were placed into service before the end of 1940.
The group at Christchurch was to develop a set for shipboard detection of aircraft and other vessels, and a companion set for directing naval gunfire. This was a smaller staff and the work went much slower, but by July 1940, they had developed an experimental VHF fire-control set and tested it on the Armed Merchant Cruiser Monowai. This was then improved to become the 430 MHz (70 cm) SWG (Ship Warning, Gunnery), and in August 1941 went into service on the Archilles and Leander, Cruisers transferred to the newly formed Royal New Zealand Navy
Royal New Zealand Navy
The Royal New Zealand Navy is the maritime arm of the New Zealand Defence Force...
(RNZN).
The same basic equipment was used by the Christchurch group in developing a ship-based air- and surface-warning system. The primary difference was that the SW antennas could be directed in elevation for aircraft detection. Designated SW (Ship Warning), it was usually installed together with the SWG. Eight of each type were eventually accepted by the RNZN. A number of SWGs were also built for the British fleet stationed in Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
; some of these with their manuals were captured by the Japanese in early 1942.
After sending engineers to the Rad Lab
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...
in the United States to study their products, a project to develop mobile 10-cm (3-GHz) systems for coast-watching and surface-fire-control that might be used throughout the Pacific. With a great demand for such systems, an experimental unit was developed and tested before the end of 1942.
Designated ME, the electronics was mounted in the cabin of a 10-wheel truck and a second truck carried the power generator and workshop. Equipment was built in both Christchurch and Wellington. The radar had a single parabolic antenna was on the roof, and a plan-position indicator CRT was used, the first such in New Zealand. The first of these went into service in early 1943 in support of a U.S. torpedo-boat base in the Solomon Islands
Solomon Islands
Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...
. Some of the MD radars were used to replace 200-MHz CW sets, and several systems were built for operation on RNZN minesweepers.
As the Allies progressed upward in the Pacific, a need arose for a long-range warning set that could be quickly set up following an invasion. The RDL took this as a project in late 1942, and in few months six Long-Range Air Warning (LWAW) systems were available. These operated at 100 MHz (3 m) and, like the microwave sets, were mounted in trucks. A single Yagi antenna was normally used, but there was also a broadside array that could be used when a more permanent operation was established. The range using the Yagi was near 150 km; this increased to over 200 km with the broadside.
From the start in late 1939, 117 radar sets of all types were built in New Zealand, all by small groups; no types were ever put into serial production. After 1943, little such equipment was produced in the country, and RNZN warships were then provided with British outfits to replace the earlier New Zealand sets.
South Africa
Like in Great Britain, RDF (radar) development in South Africa emerged from a research organization centering on lightning instrumentation: the Bernard Price Institute (BPI) for Geophysical Research, a unit of the University of the WitwatersrandUniversity of the Witwatersrand
The University of the Witwatersrand, Johannesburg is a South African university situated in the northern areas of central Johannesburg. It is more commonly known as Wits University...
in Johannesburg
Johannesburg
Johannesburg also known as Jozi, Jo'burg or Egoli, is the largest city in South Africa, by population. Johannesburg is the provincial capital of Gauteng, the wealthiest province in South Africa, having the largest economy of any metropolitan region in Sub-Saharan Africa...
. When Prime Minister Jan Smuts
Jan Smuts
Jan Christiaan Smuts, OM, CH, ED, KC, FRS, PC was a prominent South African and British Commonwealth statesman, military leader and philosopher. In addition to holding various cabinet posts, he served as Prime Minister of the Union of South Africa from 1919 until 1924 and from 1939 until 1948...
was told of this new technology, he requested that the resources of BPI be devoted to this effort for the duration of the war. Basil Schonland
Basil Schonland
Sir Basil Ferdinand Jamieson Schonland CBE FRS was the first president of the South African Council for Scientific and Industrial Research.-Birth and Parentage:...
, a world-recognized authority on lightning detection and analysis, was appointed to head the effort.
With nothing more than copies of some "vague documents" and notes provided by New Zealand’s representative at the briefings in England, Schonland and a small team started the development in late September 1939. Before the end of November the various elements of the system were completed, all by using locally available components. These were assembled in separate vehicles for the transmitter and receiver.
The transmitter operated at 90 MHz (3.3 m) and had a power of about 500 W. The pulse was 20-μs in width and the PRF was 50 Hz, synchronized with the power-line. The receiver was super-regenerative, using type 955 and 956 Acorn tubes in the front end and a 9-MHz IF amplifier. Separate, rotatable antennas with stacked pairs of full-wave dipoles were used for transmitting and receiving. The beams were about 30 degrees wide, but the azimuth of the reflected signal was determined more precisely by using a goniometer
Goniometer
A goniometer is an instrument that either measures an angle or allows an object to be rotated to a precise angular position. The term goniometry is derived from two Greek words, gōnia, meaning angle, and metron, meaning measure....
. Pulses were displayed on the CRT of a commercial oscilloscope.
Before the end of the year, a full system had been assembled and detected a water tank at a distance of about 8 km. Improvements were made on the receiver, and the transmitter pulse-power was increased to 5 kW. Designated JB-1 (for Johannesburg), the prototype system was taken to near Durban
Durban
Durban is the largest city in the South African province of KwaZulu-Natal and the third largest city in South Africa. It forms part of the eThekwini metropolitan municipality. Durban is famous for being the busiest port in South Africa. It is also seen as one of the major centres of tourism...
on the coast for operational testing. There it detected ships on the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, as well as aircraft at ranges to 80 km.
In early March 1940, the first JB-1 system was deployed to Mambrui
Mambrui
Mambrui is a settlement in Kenya's Coast Province, located east of Marikebuni along the Malindi-Garissa Road, south of Gongoni and north of Malindi....
on the coast of Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
, assisting an anti-aircraft Brigade in intercepting attacking Italian bombers, tracking them up to 120 kilometres (74.6 mi). During early 1941, six systems were deployed to East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
and Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
; JB systems were also placed at the four main South African ports.
An improved system, designated JB-3, was built at the BPI; the most important changes were the use of a transmit-receive device (a duplexer) allowing a common antenna, and an increase in frequency to 120 MHz (2.5 m). The range increased to 150 km for aircraft and 30 km for small ships, with a bearing accuracy of 1–2 degrees. Twelve sets of JB-3 radars began deployment around the South African coast in June 1941.
By mid-1942, British radars were available to need all new South African needs. Thus, no further developments were made at the BPI. Most of the staff joined the military. Basil Schonland, as a Lt. Colonel in the South African Army
South African Army
The South African Army is the army of South Africa, first formed after the Union of South Africa was created in 1910.The South African military evolved within the tradition of frontier warfare fought by commando forces, reinforced by the Afrikaners' historical distrust of large standing armies...
, went to Great Britain to serve as Superintendent of the Army Operational Research Group and later the scientific advisor to Field Marshal Bernard Montgomery.