Radar in WW II
compiled by Larry Belmont
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A Brief History of Radar Through 1941
A pioneer in radar, Colonel William Blair, director of the Signal Corps laboratories at Fort Monmouth, New Jersey, patented the first Army radar, which was demonstrated in May 1937. Even before the United States entered World War II, mass production of two radar sets, the SCR-268 (shown at left, with Afro-American GIs training in its use in the early 1940s) and the SCR-270, had begun. Along with the Signal Corps' tactical FM radio, also developed in the 1930s, radar was the most important communications development of World War II.
Radar Development through December 1941
A Brief History of British Radar During the Battle of Britain
The painting (by Chris French and reproduced here by permission) shows three steel towers with their transmitter antennas slung between. On the lower left, the "girl on the tube" interprets the "blips" of enemy aircraft on the screen. The information was then sent via the telephone (lower right) to filter and operations rooms where the table-map could be updated by a "plotter" (top right). The markers represented hostile and friendly aircraft and were used to plan and monitor air battles. 234 Squadron’s Spitfires (top left) peel of to intercept enemy bombers. The succession of functions became commonly known as "Read", "Report", "Filter", "Identify", "Tell" and "Plot."
Radar has been described as the weapon that won the war, and the atomic bomb the weapon that merely ended it. This is a pretty accurate statement, radar having played a crucial role in the outcome of the Second World War. It was one of the most important factors in the winning of the Battle of Britain and the Battle of the Atlantic and was of great importance to air support for ground operations in N.W. Europe, North Africa, S.E. Asia and the Pacific island-hopping campaigns.
It is not generally appreciated how widely used radar was during the war. Britain, Germany, U.S.A., Canada, Australia, New Zealand, South Africa, U.S.S.R., Italy, France and Japan all developed and deployed their own radar equipment before and during the Second World War. Despite such widespread use, however, not all nations realised its potential as part of an integrated air defence system, such as that which played a crucial part on the victory of the Royal Air Force in the Battle of Britain. Failure to adopt such a system for aircraft warning radar could result in disaster, as shown when the radar warning of Japanese aircraft approaching Pearl Harbor on 7 December 1941 was not acted upon. Although radar performed many different roles (including ground stations for tracking shipping, ballistic missiles, mortar bombs, etc., as well as airborne equipment for the detection of aircraft or ships), it is the use of ground radar for the detection of aircraft that is best known and its finest moment came with the Battle of Britain. The following will give a brief description of the British ground radars in use during the battle and how they were of such importance.
The mainstay of British early warning radar in 1940, and indeed through the war, was the Chain Home system. The photo below shows the only Chain Home radar transmitter tower remaining in its original form. In 1956, this tower, constructed in 1937 and standing 110 meters high, was moved from its original coastal site to Marconi Research Laboratories at Great Baddow where it stands today. This operated on the relatively long wavelength of around 11 metres. This long wavelength, which required aerials around 5.5 metres long, meant that the aerials could not be rotated but were fixed in a single direction, known as the line of shoot, flooding with radio waves an arc of about 150 degrees centred on the line of shoot. By installing a line of such stations with overlapping coverage, it was intended to provide a radar 'fence' through which no aircraft could penetrate without being detected. Whereas a rotating radar might be facing the opposite direction at the crucial moment, continuous coverage from the Chain Home stations would, in theory, never fail in this respect.
Chain Home had three separate stages of development: Advance, Intermediate and Final. Advance Chain Home (A.C.H.) stations consisted of equipment housed in huts or lorries and with aerials mounted on 90 foot masts. Intermediate (I.C.H.) used the same hutted accomodation but with two 240 foot wooden towers, one for the transmitting aerials and the other for the receivers. The Final C.H. stations consisted of protected brick buildings housing transmitters and receivers, with 350 foot steel towers for the transmitting arrays and 240 foot wooden towers (as used by I.C.H. stations) for the receiving aerials. At the time of the Battle of Britain, most stations were Intermediate C.H.s, with a few Advance C.H. stations being set up to provide emergency coverage in areas not already equipped with radar. The amount of warning given varied on a great many factors, such as the equipment in use at the station, the quality of the chosen site, the skill and experience of the staff, the availability of equipment spares, etc. Most important of all was the height of the aircraft, low-flying aircraft being particularly difficult to detect except at very short distances from the station. As a rough guide, the following are the performance figures for a C.H. station from July 1940:
Despite the figures given above, Chain Home was
generally poor on aircraft flying below 3,000 feet and thus aircraft at such
heights were able to approach quite close to the British coast before being
detected, greatly reducing the amount of warning time for fighter aircraft to
take off and intercept. The scientific team working on radar development for
the Air Ministry were, however, aware of this problem. A solution was
discovered in the adaptation of an equipment being developed by an Army team
attached to them. This set, known as C.D. for Coast Defence, was intended to
track shipping to assist coastal batteries in their task. However, the Air
Ministry team were able to adapt it for the detection of low-flying aircraft.
In view of the urgent need for low-level coverage, the supplies of this set
were given to the R.A.F. and became Chain Home Low. These stations were
installed in several 'crash' programmes in late 1939 and early 1940. The speed
with which this construction prgramme was carried out can be seen from the
fact that from the first station going on the air in November 1939, 30
stations were operating by the beginning of the Battle of
This demonstrates what is rarely appreciated, that C.H.L. could supplement
the C.H. coverage at medium heights, as well as filling the low-level
The above text was prepared by Ian Brown who can be reached at firstname.lastname@example.orgAt the outbreak of war, the Air Ministry's radar research establishment at Bawdsey Manor on the East Coast was evacuated to Dundee. Early in 1940 the team moved to a purpose built site at Worth Matravers in Dorset (picture at left). Here, a greatly expanded staff of scientists and engineers from the universities and industry researched and developed a whole range of systems that helped win the war. The introduction of centimeter wavelength technology, made possible by the invention of the Cavity Magnetron by Randall and Boot, was followed by a number of significant centimeter radar developments at Worth Matravers.
The wartime developments originated while the Telecommunications Research Establishment (TRE) was based in Dorset and which played a vital part in the D-Day operation including:-
GCI (Ground Controlled Interception) for guiding night fighters to within range of an enemy bomber for interception by Air Interception (AI).
Gee An accurate radar navigation system to guide bombers to their targets
Oboe A blind bombing system
Rebecca To guide paratroops to a selected landing zone
Babs A homing beacon for airfields
Development work on other earlier systems, such as Air Interception (AI), and Air Surface Vessel, continued and more effective versions of these devices were brought into use.
In late 1941, Sir Bernard Lovell set up a team to develop a centimetric navigation and bombing equipment. The intensive program of development, necessary to provide the RAF with a minimum range of 15 miles, was severely set back, just after TRE moved to Malvern in 1942. The Halifax bomber that was being used to test the equipment, crashed killing five of the small team, including Alan Blumlein from EMI, and wrecking the equipment. However, by the end of that year a device called H2S, that enabled effective bombing attacks to be made through 10/10ths cloud and in the dark, was installedand operating in the heavy bombers of Bomber Command. [More information is available from the Center for History of Defence Electronics (CHiDE)].
The Army's Aircraft Warning Service (AWS) was in operative condition, for all practical purposes, on Sunday morning, December 7, 1941. It was comprised of an information center and five mobile stations (one of which is pictured at left, using an SCR-270-B unit). The radar systems in use that day were SCR-270-B radio sets. They were mobile units housed in two trucks. The unit's heart was the oscilloscope that gave a picture similar to a heart monitor in hospitals today. The operator would move the antenna through a given arc until the line across the bottom showed a small spike or pip. By adjusting the antenna and the controls, the pip was enhanced until the operator could tell the approximate distance to the target. Next, the operator looked out the window to a plate mounted on the antenna base, with an arrow on it that would give the direction of the contact. Unlike today's radar scopes, the antenna did not oscillate and there was no constant repainting of the picture on the scope. This system did not tell an incoming target's altitude, its size or number, nor did it differentiate friend from foe.
In July 1941, these radio sets had begun arriving on Oahu. Signal Company personnel began assembling them at Schofield Barracks and then began learning how to operate them. Once assembled, personnel moved them to prepared sites throughout the island. The Signal Corps planned for six sets. On the morning of the attack, five were operational, with the sixth still at Schofield. The five operational sets were at Kaaawa, Opana, Kawailoa, Fort Shafter, and Koko Head. The sets began operating at 0400 on 7 December except at Opana, which came on the air at around 0415 due to a delay for early morning maintenance on the generator. The operators had been on duty since noon Saturday. They divided their tour between standing guard, maintenance, and operating the sets. The schedule called for each site to have a crew of three: one operator, one plotter, and one person to maintain the power generators. Because several units worked from commercial power and used the generators as standby power, some crews cut back to two people per shift on the weekend. Opana had two crew members that Sunday morning. During the first two hours, no radar contacts were made. At 0613, Koko Head and Fort Shafter began picking up sightings south of the island. Then at 0645, Kaaawa, Opana, and Kawailoa picked up a target approximately 135 miles north of Oahu heading south. All three stations called the Information Center with the targets, which were then plotted on the master plot board. Personnel at the center included five plotters (one for each radar site), a historical information plotter; PFC Joseph P. McDonald, the switchboard operator; and Lt Kermit Tyler, a pursuit pilot. The radar sites phoned the plots to the five plotters, and no one present found anything unusual with the information. McDonald had worked the switchboard for several months and knew the radar operators, while Tyler had been to the Information Center only once before. On 3 December he had worked from 1200 to 1600 with just the switchboard operator. On that occasion nothing happened, because the sites were not operating. Therefore, this was the first time he had actually seen personnel plot targets. When the reports began coming in, Tyler went to the historical plotter's position and talked with him about how he recorded the information. These first plots were probably the scout planes sent ahead of the main attacking force.
At 0700, all the radar sites began shutting down. At the Information Center, the five plotters and the historical information plotter shut down and left the area, leaving McDonald and Tyler behind. At Opana, Privates George E. Elliott and Joseph L. Lockard were to work until noon, but the next shift came back early from a pass to town so they relieved them at 0800. This meant that when the truck arrived to take them to breakfast, they would be through for the day; however, the same call that informed them about the early release also let them know the truck would be late. Lockard was a trained radar operator and had been with the 270s since they arrived on the island, while Elliott had just transferred into the Signal Corps from the Hawaiian Air Force and only knew how to operate the plotting board. Because the breakfast truck was late and they were going to be off for the remainder of the day, the two decided to use the time to work on Elliott's training. A few minutes after seven, Elliott saw a large spike on the screen. Thinking he had done something wrong, he immediately began to check the settings. Lockard then took over the operation and also rechecked the controls. This was the biggest sighting he had ever seen since learning how to operate the system. Elliott then tried to call the Information Center, using the phones connected directly to the plotters. No one was there to take the call. He then called on the administration line and got McDonald. The switchboard operator knew both of the radar operators and tried to explain to them that there was nobody on duty in the Center after 0800. McDonald then spotted Lt Tyler and called him over to talk to Elliott. Meanwhile, Lockard got on the phone and tried to explain the large target that might be significant. McDonald interjected that if the targets were so large, maybe they should call back the plotters so they could practice handling a big aircraft movement. Tyler thought about this for a moment and then told Lockard and McDonald not to worry and closed the conversation. Since the breakfast truck had not arrived, Elliott and Lockard continued tracking the incoming target until about 20 miles from the coast of Oahu. At that point ground interference blocked the signal, and the target was lost. This was approximately 0745. Just then the breakfast truck pulled up and the two young radar operators shut their unit off and headed down the mountain to breakfast, devoid of the knowledge that they had discovered the first wave of the Japanese attack. Why had Lt Tyler told the operators not to worry, and why had he not followed McDonald's advice to call back the plotters? Tyler saw no reason to change the normal operations that morning. First, there was no alert or warning of an impending attack. Second, the U.S. Fleet's carriers were at sea and the sightings could well have been the carrier's aircraft returning to port. Third, a bomber pilot friend had explained just a few days before that one could always tell when aircraft were arriving from the US because the local radio stations would play Hawaiian music all night. The incoming aircraft would use the music to tune their directional finders and locate the islands. (This was exactly what the Japanese did.) On the way to the Center, Tyler heard the Hawaiian music, so he assumed a flight was coming in. Finally, although Lockard had said this was the biggest flight he had ever seen, he did not say how many aircraft he thought it might contain. Later, Lockard would claim he knew the flight had to number over 50 aircrah to make that large of a pip on the screen, but at the time he did not give that information to anyone. Had Tyler known the sighting was over 50 aircraft, he might have reacted differently; but with what little information he had, second lieutenants did not wake up commanding officers at seven o'clock Sunday mornings with wild speculations. Lockard and Elliott heard about the attack when they returned to their camp. After a quick breakfast, they returned to Opana and helped keep the site operating 24 hours a day for the next several months. The first Lt. Tyler heard about the attack was a telephone call from someone at Wheeler Field shortly aflter 0800. The plotters were immediately called back, and soon a full complement arrived. Tyler stayed in the Center except for short rest breaks for the next 36 hours. During the morning's activities, two plots began to form 30 to 50 miles southwest of Oahu. Not knowing what these were and thinking they could be the retiring Japanese circling before landing on their carriers, the senior controller passed this information to bomber command as the possible location for the Japanese attack force. No one remembered to check the early reports coming in before 0700 or the Opana sighting after 0700. It wasn't until several days later that people assembled this information and realized the radar stations had located the direction from which the attack was launched . In summary, the AWS was sufficiently operative to successfully pick up the approaching Japanese force 132 miles from Oahu. This was done by Privates Lockard and Elliott, respectively, a radar operator and plotter, and reported by these privates on their own initiative to the information center, where the Sergeant in charge of the switchboard received the information and relay it to Lieutenant Tyler, who was a pursuit officer of the Air Corps on temporary duty for training. The stations had been used from 0400 to 0700 hours each morning for the training personnel, and the personnel was reasonably trained by that time, with the exception of certain liaison officers who were still getting their training, like Lieutenant Tyler. If the radar system and information center had been fully manned, as it could have been and as it was immediately upon the disaster at Pearl Harbor and thereafter without further physical additions, it could have been successfully operated on December 7 and perhaps enabled the Air Corps to respond in time to avoid much of the disaster that befell the U.S. forces that day.
The Primary Allied "Airborne Radars
The Primary German "Airborne Radars
The following material is reprinted from Pauke, Pauke! The German WW II Night Fighters Resource Page (see
German Radars especially.) (In the photo above, a Ju88 night fighter sports nose-mounted airborne radar.)
Drawing upon experience ranging from the Western Desert and Tunisia through the Sicilian and Italian campaigns, Allied tactical air control in Normandy and during the subsequent European campaign was generally excellent. Fundamental to this success was the wartime evolution of radar. The Allied air forces had radar available to them from the very first day of Normandy operations, and it was soon incorporated into tactical air control as well as for early warning and air defense purposes. Radar had first been used for tactical air support control during the Sicilian and Italian campaigns, and now, in Normandy and the subsequent breakout, it reached new levels of refinement. Each TAC had a radar control group built around a Tactical Control Center (also called a Fighter Control Center), a microwave early warning radar (dubbed a MEW), three Forward Director Posts, three or four SCR-584 Close Control Units (the SCR-584 being a particularly fine precision radar used for positioning data and antiaircraft gun laying; see picture above), and, finally four Direction Finding stations, dubbed Fixer stations. The MEW, considered the heart of the system, would be located within ten to thirty miles of the front.
Originally developed for air defense purposes, this radar network now took on added importance for the control of tactical air strikes. For example, when an Air-Ground Coordination Party sent in a request for immediate air support, that request went directly to a Combined Operations Center functioning between the TAC and the Army. There, the Army S2 and G-3 and the TAC A-2 and A-3 evaluated the request. Assuming it was considered legitimate, the Army G-3 and Air A-3 would each approve it, and the Air A-3 would relay it to the Tactical Control Center with a recommended course of action. Typically, the TCC would relay the request to airborne fighter-bombers, and a geographically appropriate Forward Director Post would furnish precise radar guidance and navigation information from the MEW and SCR-584 radars to the strike flight, vectoring them to the target area. Once in the target area, of course, the strike flight leader would communicate with the Air-Ground Coordination Party that had sent in the request for final details. For its part, the Air-Ground Coordination Party would arrange for artillery to mark the target with colored smoke and also, if possible, to undertake suppressive artillery fire against known enemy antiaircraft defenses. Radar was also used for so-called blind bombing in conditions of reduced visibility. SCR-584 control eventually enabled blind bombing strikes with accuracies on the order of 400-yards from the predetermined aiming point, notably during the Battle of the Bulge in winter 1944-45.
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