The
history of radar began in the early 1900s when German engineer Christian Hülsmeyer invented a simple omni-directional detecting device (Reichspatent Nr. 165546). However, it implied the prior knowledge of
electromagnetismElectromagnetism is the physics of the electromagnetic field, a field that exerts a force on particles with the property of electric charge and is reciprocally affected by the presence and motion of such particles....
given by the 19 century's discoveries of
MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
and Hertz. The technique developed through the 1920s and 1930s, leading to the introduction of the first
early warning radarAn early warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in-which to operate...
networks just before the opening of
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
.
Progress during the war was rapid and was of the greatest importance, probably one of the decisive factors for the victory of the
AlliesThe Allies of World War II were the countries that opposed the Axis powers during the Second World War . The involvement of the Allies in World War II was either natural and inevitable they were invaded or under the direct threat of invasion by the Axis or compelled by concerns that the Axis powers...
. By the end, the United States and other countries widely deployed ground-based radars that fit in a single
semi-trailerIn American English a semi-trailer is a trailer without a front axle. A large proportion of its weight is supported either by a road tractor or by a detachable front axle assembly known as a dolly or by the tail of another trailer...
, and airborne radars were in initial production. After the war, radar use was widened to numerous fields including:
civil aviationCivil aviation is one of two major categories of flying, representing all non-military aviation, both private and commercial. Most of the countries in the world are members of the International Civil Aviation Organization and work together to establish common standards and recommended practices...
, marine
navigationNavigation is the process of reading, and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. The word navigate is derived from the Latin "navigare", meaning "to sail"...
,
radar gunA radar gun or speed gun is a small Doppler radar unit used to detect the speed of objects, especially trucks and automobiles for the purpose of regulating traffic, as well as pitched baseballs, runners or other moving objects in sports. A radar gun does not return information regarding the...
s for police,
meteorologyMeteorology is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting . Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the eighteenth century...
and even
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
.
Significance
The place of radar in the larger story of science and technology is argued differently by different authors. Radar, far more than the atomic bomb, contributed to Allied victory in World War II. Robert Buderi states that it was also the precursor of much modern technology. From a review of his book:
... radar has been the root of a wide range of achievements since the war, producing a veritable family tree of modern technologies. Because of radar, astronomers can map the contours of far-off planets, physicians can see images of internal organs, meteorologists can measure rain falling in distant places, air travel is hundreds of times safer than travel by road, long-distance telephone calls are cheaper than postage, computers have become ubiquitous and ordinary people can cook their daily dinners in the time between sitcoms, with what used to be called a radar range.
But others think that radar is not so important, since the principles were not new:
- Le principe fondamental du radar appartient au patrimoine commun des physiciens : ce qui demeure en fin de compte au crédit réel des techniciens se mesure à la réalisation effective de matériels opérationnels., or roughly
- The fundamental principle of the radar belongs to the common patrimony of the physicists : after all, what is left to the real credit of the technicians is measured by the effective realisation of operational materials". — Maurice Ponte L'histoire du "radar ", les faits, or The history of the "radar", the facts
Before the twentieth century
In 1887 the German
physicistA physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
Heinrich Hertz began experimenting with
radio wavesRadio waves are that part of the electromagnetic spectrum with wavelengths longer than infrared light. Naturally-occuring radio waves are produced by lightning, or by astronomical objects. Artificially-generated radio waves are used for broadcasting, mobile and fixed communications, navigation,...
in his laboratory. He found that radio waves could be transmitted through different types of materials, and were reflected by others, such as conductors and
dielectricA dielectric is a nonconducting substance, i.e. an insulator. The term was coined by William Whewell in response to a request from Michael Faraday...
s. The existence of electromagnetic waves was predicted earlier by the Scottish physicist
James Clerk MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
, but it was Hertz who first succeeded in generating and detecting radio waves. Marconi followed up this research and in a paper read before the Institution of Electrical Engineers in London on March 3, 1899, he described radar-type experiments he had conducted in Salisbury Plain. Concerning this lecture he later wrote,
In his 1922 article Marconi also included circuit diagrams showing the apparatus he allegedly used to make these experiments.
Christian Huelsmeyer
In 1904 Christian Huelsmeyer gave public demonstrations in
GermanyGermany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium,...
and the
NetherlandsThe Netherlands is a country in Northwestern Europe, constituting the major portion of the Kingdom of the Netherlands. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east...
of the use of radio
echoesIn audio signal processing and acoustics, an echo is a reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room. A true echo is a single reflection of the sound...
to detect
shipA ship is a large vessel that floats on water. Ships are generally distinguished from boats based on size and passenger capacity. Ships may be found on lakes, seas, and rivers and they allow for a variety of activities, such as the transport of people or goods, fishing, entertainment, public...
s so that collisions could be avoided. His device consisted of a simple
spark gapA spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air. When a suitable voltage is supplied, a spark forms, ionizing the gas and drastically reducing its electrical resistance...
aimed using a
multipoleA dipole antenna, created by Heinrich Rudolph Hertz around 1886, is an antenna that can be made by a simple wire, with a center-fed driven element for transmitting or receiving radio frequency energy...
antennaAn antenna is a transducer designed to transmit or receive electromagnetic waves. In other words, antennas convert electromagnetic waves into electrical currents and vice versa. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless...
. When a
reflectionReflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
was picked up by the two straight antennas attached to the separate
receiverThis article is about a radio receiver, for other uses see Radio .A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for...
, a bell sounded. During bad weather or fog, the device would be periodically "spun" to check for nearby ships. The system detected presence of ships up to 3
kmKM, Km, or km may stand for:*Kilometre *KM - the Michaelis constant in Michaelis-Menten kinetics*Kernel methods*Kettle Moraine High School*Khmer language...
, and he planned to extend its capability to 10 km. It did not provide
range-In mathematics:* Range - Interval, the range between minimum and maximum* Range , the set of all output values produced by a function**Column space, the range space of a matrix...
information, only warning of a nearby object. He patented the device, called the
telemobiloscope, but due to lack of interest by the naval authorities the invention was not put into production.
Also in 1904, Huelsmeyer received a patent of amendment for ranging that is indirectly related to his device. Using a vertical scan of the horizon with the
telemobiloscope mounted on a tower, the operator would find the angle at which the return was the most intense and deduce, by simple triangulation, the approximate distance. This is in contrast to the later development of pulsed radar, which determines distance directly.
Guglielmo Marconi
Guglielmo MarconiMarchese Guglielmo Marconi was an Italian inventor, best known for his development of a radiotelegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide...
in his 1922 I.R.E. paper writes that he did not work on radar since his 1899 experiment in Salisbury plain until 1916 when advances in short-wave radio and circumstances of the world being at war led him to resume research. He wrote,
- "The investigation of the subject was again taken up by me in Italy early in 1916 with the idea of utilizing very short waves combined with reflectors for certain war purposes...."
He describes these experiments, which were primarily investigations of direction finding, in the paper and notes that:
- "It seems to me that it should be possible to design [an] apparatus by means of which a ship could radiate or project a divergent beam of these rays in any desired direction, which rays, if coming across a metallic object, such as another steamer or ship, would be reflected back to a receiver screened from the local transmitter on the sending ship, and thereby immediately reveal the presence and bearing of the other ship in fog or thick weather."
This paper and a speech presenting the paper to a joint meeting of the Institute of Radio Engineers and the American Institute of Electrical Engineers in New York City on June 20, 1922, is often cited as the seminal event which began widespread interest in the development of radar.
Nikola Tesla
Nikola TeslaNikola Tesla was an inventor and a mechanical and electrical engineer. He is frequently cited as one of the most important contributors to the birth of commercial electricity and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th...
, in August 1917, proposed principles regarding frequency and power levels for primitive radar units. In the 1917
The Electrical Experimenter, Tesla stated the principles in detail:
- "For instance, by their [standing electromagnetic waves] use we may produce at will, from a sending station, an electrical effect in any particular region of the globe; [with which] we may determine the relative position or course of a moving object, such as a vessel at sea, the distance traversed by the same, or its speed."
Tesla also proposed the use of these
standing electromagnetic wavesA standing wave, also known as a stationary wave, is a wave that remains in a constant position. This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite...
along with pulsed reflected
surface waveIn physics, a surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient...
s to determine the relative position, speed, and course of a moving object and other modern concepts of radar.
Tesla had first proposed that radio location might help find
submarineA submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has only limited underwater capability...
s (for which it is not well-suited) with a fluorescent screen indicator.
Naval Research Laboratory
In the autumn of 1922,
Albert H. TaylorDr. Albert Hoyt Taylor was an American electrical engineer who made important early contributions to the development of radar....
and Leo C. Young of the U.S. Naval Research Laboratory (NRL) were conducting communication experiments when they noticed that a wooden ship in the
Potomac RiverThe Potomac River flows into the Chesapeake Bay, located along the mid-Atlantic coast of the United States. The river is approximately 383 statute miles long, with a drainage area of about 14,700 square miles . In terms of area, this makes the Potomac River the fourth largest river along the...
was interfering with their signals; in effect, they had demonstrated the first
continuous waveA 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. Information...
(CW) interference radar with separated transmitting and receiving antennas. In June, 1930,
Lawrence A. HylandLawrence 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...
of the NRL in the U.S. detected an
airplaneA fixed-wing aircraft, usually called an airplane, aeroplane or plane, is an aircraft capable of flight using forward motion that causes air to pass over its wings to generate lift. Planes include jet engine and propeller driven vehicles propelled forward by thrust, as well as unpowered aircraft...
with this type of radar operating on 33 MHz.
Simple wave-interference radar can detect the presence of an object, but it cannot determine its
locationIn geography, Location is a position or point in physical space that something occupies on the Earth's surface, the Solar System, or mankinds physically reachable universe...
or
velocityIn physics, velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI system, it is measured in meters per second: or ms-1. The scalar absolute value of velocity is speed...
. That had to await the invention of
pulse radarPulse-Doppler is a radar system capable of not only detecting target location , but also measuring its radial velocity...
, and later, additional encoding techniques to extract this information from a CW signal. The British and the US research groups were independently aware of the advantages of such an approach, but the problem was to develop the timing equipment to make it feasible. In the early 1930s, Taylor assigned one of his engineers,
Robert M. PageRobert Morris Page was an American physicist who was a leading figure in the development of radar technology.-Life and career:...
, to implement a demonstration system of the pulsed radar idea that he and Young had theorized. Page produced and operated such a pulse system in December 1934 using pulses of 25 MHz and 5 μs width. An important development by Young and Page was the Radar Duplexer. This allowed the transmitter and receiver to use the same antenna without over-whelming or destroying the sensitive receiver circuitry. This also solved the problems associated with synchronization of separate transmitter and receiver antennas which is critical to accurate long range target position determination.
The Robert Page experiments with pulse radar were conducted at the NRL in 1934 and 1935. On April 28, 1936, their first pulse radar was demonstrated successfully at a range of 2.5
mileA mile is a unit of length in a number of different systems. In contemporary English, mile most commonly refers to the statute mile of 1,609.344 meters or the nautical mile of 1,852 meters...
s on a small airplane flying up and down the Potomac, but by June of that year, the range was extended to . Their radar was based on
low frequencyLow frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...
signals, at least by today's standards, and thus required large
antennasAn antenna is a transducer designed to transmit or receive electromagnetic waves. In other words, antennas convert electromagnetic waves into electrical currents and vice versa. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless...
, making it impractical for ship or aircraft mounting.
Compagnie Générale de Télégraphie Sans Fil (CSF)
In 1927, French engineers Camille Gutton and Pierret experimented with wavelengths going down to 16 cm. Other engineers, Mesny and David, noticed repeatedly since 1931 that an aircraft flying between a transmitter and a receiver would disturb a radio communication. This was the basis of a device put into operational use in 1935 by the
Compagnie Générale de Télégraphie Sans FilThomson-CSF was a major electronics and defense contractor. In December 2000 it was renamed Thales Group.-History:In 1879 Elihu Thomson and Edwin Houston formed the Thomson-Houston Electric Company in the United States....
(CSF) to detect airplanes flying over a given zone.
In 1934, Henri Gutton (the son of the former, and engineer of the CSF) resumed his father's experiments after initial reports made by the U.S. Naval Research Laboratory in 1930 (see above) and brought improvements to the magnetron.
Emile GirardeauÉmile Girardeau was a French engineer, famous for being the first person to patent the original system of frequencies that is used today and known as the radar...
http://www.radar-france.fr/Emile%20Girardeau.htm, the head of the CSF, recalled in testimony that they were at the time intending to build radar systems "
conceived according to the principles stated by Tesla". The CSF submitted the
French patent (no. 788.795, "
New system of location of obstacles and its applications") on July 20 1934, for a device detecting obstacles (icebergs, ships, planes) using pulses of ultra-short wavelengths produced by a magnetron. This is the first patent of an operational radar using centimetric wavelengths. The radar was tested from November to December 1934 aboard the cargo ship
Oregon, with two transmitters working at 80 cm and 16 cm wavelengths. Coastlines were detected from a range of 10-12 nautical miles. The shortest wavelength was chosen for the final design, which equipped the liner
NormandieSS Normandie was a French ocean liner built in Saint-Nazaire, France, for the French Line Compagnie Générale Transatlantique. When she entered service in 1935 she was the largest and fastest ship in the world, and she maintains the distinction of being the most powerful steam turbo-electric...
as early as mid-1935 for operational use.
Robert Watson-Watt
In 1915
Robert Watson-WattSir Robert Alexander Watson-Watt, Order of the Bath, LLD, DSc, FRS, FRAeS is considered by many to be the "inventor of radar"...
joined the
Meteorological OfficeThe Met Office , is the United Kingdom's national weather service, and a trading fund of the Ministry of Defence. Part of the Met Office headquarters at Exeter in Devon is the Met Office College, which handles the training for internal personnel and many forecasters from around the world...
as a meteorologist. Working at an outstation at
AldershotAldershot is a town in the English county of Hampshire, located on heathland about 60 km southwest of London. The town is administered by Rushmoor Borough Council...
, in
HampshireHampshire , sometimes historically Southamptonshire, Hamptonshire, , or the County of Southampton, is a county on the south coast of England. The county borders , Dorset, Wiltshire, Berkshire, Surrey and West Sussex...
,
BritainThe United Kingdom of Great Britain and Ireland was the formal name and the state form of the United Kingdom from 1 January 1801 until 12 April 1927...
, he developed the use of radio signals generated by
lightningLightning is an atmospheric discharge of electricity accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
strikes to map out the position of
thunderstormA thunderstorm, also known as an electrical storm, a lightning storm, a hailstorm, or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically-assigned cloud type associated with the...
s. The difficulty in pinpointing the direction of these fleeting signals led to the use of rotating directional antennas, and in 1923 the use of
oscilloscopeAn oscilloscope is a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences plotted as a function of time or of some other voltage...
s in order to display them. An operator would periodically rotate the antenna and look for "spikes" on the oscilloscope to find the direction of a storm. At this point the only missing part of a functioning radar was the
transmitterA transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications.-Transmitter types:...
.
By 1934 Watson-Watt was well established in the area of radio as head of the
Radio Research StationThe Radio Research Station 1924 - August 31, 1979 at Ditton Park, Buckinghamshire, England was the UK government research laboratory which pioneered the regular observation of the ionosphere by ionosondes in continuous operation since September 20, 1932, and applied the ionosonde technology for the...
at
Ditton ParkDitton Park was part of the Manor of Ditton which was in what was formerly the south east corner of the English county of Buckinghamshire, before the county boundary reorganisations of the 1974 & 1998 which moved it to the Slough Unitary Authority, which is in the ceremonial county of...
near
SloughSlough , situated west of Charing Cross, is a borough and unitary authority within the ceremonial county of Berkshire, England. At the time of the 2001 census, the population of Slough was 119,070 Slough , situated west of Charing Cross, is a borough and unitary authority...
. He was approached by H.E. Wimperis from the
Air MinistryThe Air Ministry was formerly a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, existing from 1918 to 1964...
, who asked about the use of radio to produce a '
death rayThe death ray or death beam was a theoretical particle beam or electromagnetic weapon of the 1920s through the 1930s that was claimed to have been invented independently by Nikola Tesla, Edwin R. Scott, Harry Grindell Matthews, and Graichen, as well as others. By 1957 the National Inventors Council...
', after hearing Germans claims to have built such a device. Watt quickly wrote back that this was unlikely, and he pointed out that in the absence of progress,
meanwhile attention is being turned to the still difficult, but less unpromising, problem of radio detection and numerical considerations on the method of detection by reflected radio waves will be submitted when required. Watson-Watt and his assistant
Arnold WilkinsArnold Frederic Wilkins O.B.E., was a pioneer in developing the use of radar.He was the son of John Knowles Wilkins of Chester and was educated at The King's School, Chester and St...
published a report on the topic on February 12, 1935, titled
The Detection of Aircraft by Radio Methods.
On February 26 1935 Watson-Watt and Wilkins demonstrated a basic radar system to an observer from the Air Ministry Committee the Detection of Aircraft. The previous day Wilkins had set up receiving equipment in a field near Upper Stowe,
NorthamptonshireNorthamptonshire is a landlocked county in the English East Midlands, with a population of 629,676 as at the 2001 census...
, and this was used to detect the presence of a
Handley Page HeyfordThe Handley Page Heyford was a twin-engine British biplane bomber of the 1930s. Although it had a short service life, it equipped several squadrons of the RAF as one of the most important British bombers of the mid-1930s, and was the last biplane heavy bomber to serve with the RAF.-Design and...
bomber at ranges up to by means of the radio waves which it reflected from the nearby
DaventryDaventry is a market town in Northamptonshire, England, with a population of 22,367 . The town is also the administrative centre of the larger Daventry district, which has a population of 71,838. The town is 124 km north-northwest of London, 22.4 km west of Northampton and 16.4 km...
shortwaveShortwave radio operates in the frequency range of 3,000 kHz to 30,000 kHz . Short wavelength corresponds to high frequency given the inverse relationship between frequency and wavelength, thus, “shortwave radio” is denominated so because its wavelengths are shorter than the long wave-lengths...
radio transmitter of the
BBCThe British Broadcasting Corporation, usually referred to by its abbreviation as the "BBC", is the longest established and largest broadcaster in the world...
, which operated at a wavelength of 49
mThe metre or meter is the basic unit of length in the International System of Units . Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent one ten-millionth of the distance from the Equator...
(6 MHz). This convincing demonstration, known as the
Daventry Experiment, led immediately to development of radar in the UK.
Allen B. DuMont
In 1932,
Allen B. DuMontAllen Balcom DuMont was an American scientist and inventor best known for improvements to the cathode ray tube in 1931 for use in television receivers. Seven years later he manufactured and sold the first commercially practical television set to the public...
proposed a "ship finder" device to the
United States Army Signal CorpsThe United States Army Signal Corps develops, tests, provides, and manages communications and information systems support for the command and control of combined arms forces. It was founded in 1860 by United States Army Major Albert J. Myer, a physician by training, and has had an important role...
at Fort Monmouth, New Jersey, that used radio wave distortions to locate objects on a cathode ray tube screen. The military asked him, however, not to take out a patent for developing what they wanted to maintain as a secret, and so he is not often mentioned among those responsible for radar. He did, however, go on to develop long-range precision radar to aid the Allies during WWII. As a consequence the French Government knighted him in 1952.
Soviet Early Radar
On January 3, 1934 Soviet scientists successfully tested experimental radar, developed by joint project between Central artillery Board of Soviet Army (
GAU) and Central radio Laboratory (
TsRL). A plane, flying at an altitude of about 150 meters, was able to be detected at a distance of around 600/ 700 meters of a radar facility.
Later in the same 1934 year radar devices for AA (anti-aircraft artillery) were created under contract between Central artillery Board of Soviet Army (
GAU) and
LEFI (Electrical and Physical Institute of Leningrad).
On July, 1934 an experimental radar station called "Rapid" was tested near by Leningrad by engineers of
LEFI (Electrical and Physical Institute of Leningrad) under contract with AD (air defence) Board of Soviet Army.
Dutch early radar
Several years before Watson-Watt, Dutch scientists Weiler and Gratema were inspired by queries about "death rays" from their military, to start developing radar. They were well advanced by May 1940, and had built four working prototypes of centrimetric gunlaying radar operating at a wavelength of 50 cm and a practical range of 20 km. Technically far more sophisticated than British early warning radar of the time, it was not operationally integrated into the armed forces. As the Luftwaffe destroyed the Dutch air force on its airfields, landed thousands of airborne troops on the seat of government, and laid waste to the city of Rotterdam, radar operators could only track their planes. Says Max Staal: "frustratingly, we had nothing to shoot at them with". Some scientists escaped to Britain before the Dutch capitulation on May 14, 1940, taking with them prototypes that aided the development of the British-American centrimetric radar.
Hans Hollmann
Meanwhile in Germany,
Hans HollmannHans Erich Hollmann was a German electronic specialist who made several breakthroughs in the development of radar....
had been working for some time in the field of microwaves, which were to later become the basis of almost all radar systems. In 1935 he published
Physics and Technique of Ultrashort Waves, which was picked up by researchers around the world. At the time he had been most interested in their use for communications, but he and his partner Hans-Karl von Willisen had also worked on radar-like systems.
In the autumn of 1934 their company, GEMA, built the first commercial radar system for detecting ships. Operating in the 50 cm range it could detect ships up to 10 km away. This device was similar in purpose to Huelsmeyer's earlier system, and like it, did not provide range information.
In the summer of 1935 a pulse radar was developed with which they could spot a light cruiser, the Königsberg, 8 km away, with an accuracy of up to 50 m, enough for gun-laying. The same system could also detect an aircraft at 500 m
altitudeAltitude is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object...
at a distance of 28 km. The
militaryA military is an organization authorized by its nation to use force, usually including use of weapons, in defending its country by combating actual or perceived threats. As an adjective the term "military" is also used to refer to any property or aspect of a military...
implications were not lost this time around, and construction of land and sea-based versions took place as
FreyaFreya was an early warning radar deployed by Germany during World War II, named after the Norse Goddess Freyja. During the war over a thousand stations were built. A naval version operating on a slightly different wavelength was also developed as Seetakt...
and
SeetaktThe shipborne Seetakt radar was developed in the 1930s and was used by the German Navy during World War II.In Germany during the late 1920s, Hans Hollmann began working in the field of microwaves, which were to later become the basis of almost all radar systems. In 1935 he published Physics and...
.
World War II
At the start of
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
both the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
and
GermanyGermany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium,...
knew of each other's ongoing efforts in their "
battle of the beamsThe Battle of the Beams refers to a period early in the Second World War when bombers of the German Air Force started using radio navigation for night bombing...
". Both nations were intensely interested in the other's developments in the field, and engaged in an active campaign of
espionageEspionage or spying involves an individual obtaining information that is considered secret or confidential without the permission of the holder of the information. Espionage is inherently clandestine, as the legitimate holder of the information may change plans or take other countermeasures once it...
and false leaks about their respective equipment. By the time of the
Battle of BritainThe Battle of Britain is the name given to the air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940. The objective of the campaign was to gain air superiority over the Royal Air Force , especially Fighter Command...
, both sides were deploying radar units and control stations as part of integrated air defense capability. However, German radars could not assist in offensive role and the Luftwaffe did not sufficiently appreciate the importance of British radar stations as part of
RAFThe Royal Air Force is the United Kingdom's air force, the oldest independent air force in the world. Formed on 1 April 1918, the RAF has taken a significant role in British military history ever since, playing a large part in World War II and in more recent conflicts.The RAF operates almost 1,109...
's air defense capability, contributing to their failure.
Research had been initiated by Sir
Henry TizardSir Henry Thomas Tizard was an English chemist and inventor and past Rector of Imperial College....
's
Aeronautical Research CommitteeThe Aeronautical Research Committee was a UK government committee established in 1919 in order to coordinate aeronautical research and education following World War I...
in 1935 and, from 1940, was based at the
Telecommunications Research EstablishmentThe Telecommunications Research Establishment was established in Worth Matravers, which is four miles to the west of Swanage, UK, in May 1940, as the central research group for RAF applications of radar...
(TRE). But much of the credit belongs to Watson-Watt, head of the team working at Bawdsey Manor in Suffolk, who turned from the technical side of radar to building up a usable network of machines and the people to run them. After watching a demonstration in which his radar operators were attempting to locate an "attacking" bomber, he noticed that the primary problem was not technological, but worker overload. By 1940 Watt had built up a layered organization that efficiently passed information along the chain of command, and was able to track large numbers of aircraft and direct defenses to them.
Chain Home
Shortly before the outbreak of World War II several radar stations known as
Chain HomeChain Home was the codename for the ring of coastal radar stations built by the British before and during World War II. The system otherwise known as AMES Type 1 comprised of radar fixed on top of a radio tower mast, called a 'station' to provide long-range detection of aircraft...
(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 radar to be deployed, CH was a simple system. The broadcast side was formed from two 300 ft (100 ;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 operating conditions were:
- FREQUENCY: 20 to 30 MHz (15 to 10 metres).
- PEAK POWER: 350 kW (later 750 kW).
- PULSE REPETITION FREQUENCY: 25 and 12.5 pps.
- PULSE LENGTH: 20 μs.
The CH radar 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
amplifiedGenerally, an amplifier or simply amp, is any device that changes, usually increases, the amplitude of a signal. The relationship of the input to the output of an amplifier—usually expressed as a function of the input frequency—is called the transfer function of the amplifier, and the magnitude of...
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 is 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 BritainThe Battle of Britain is the name given to the air campaign waged by the German Air Force against the United Kingdom during the summer and autumn of 1940. The objective of the campaign was to gain air superiority over the Royal Air Force , especially Fighter Command...
, and is often credited with allowing the
RAFThe Royal Air Force is the United Kingdom's air force, the oldest independent air force in the world. Formed on 1 April 1918, the RAF has taken a significant role in British military history ever since, playing a large part in World War II and in more recent conflicts.The RAF operates almost 1,109...
to defeat the much larger
LuftwaffeLuftwaffe 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 1933 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956.Schweizer Luftwaffe is also the name of the Swiss Air...
forces. Whereas the Luftwaffe had to hunt all over to find the RAF fighters, the RAF knew exactly where the Luftwaffe 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 pilot's workloads, but also reduced wear on engines, as well as reducing unnecessary
petrolAvgas is a high-octane aviation fuel used to power many aircraft and racing cars. Avgas is a portmanteau for aviation gasoline, as distinguished from mogas , which is the everyday gasoline used in cars. Some light aircraft also use automobile fuel instead of avgas.Avgas is used in aircraft that...
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 Luftwaffe apparently never understood the importance of radar to the RAF's efforts, or they would have assigned them 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.
In order 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 radar 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 radars 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
clutterClutter may refer to any of the following:*Excessive physical disorder:** Clutter : A confusing or disorderly state or collection; or the creation thereof...
. 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 ForceThe 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
Similar systems were later adapted with a new
displayThe cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen...
to produce the
Ground Controlled InterceptGround-controlled interception an air defense tactic whereby one or more radar stations are linked to a command communications center guides interceptor aircraft to an airborne target. This tactic was pioneered by the Royal Air Force during the World War II, although the Luftwaffe eventually built...
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 around the station with the operator in the middle, with all the aircraft appearing as dots in the proper location in space. These so-called
Plan Position IndicatorThe 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) 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.
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 was 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 BowenEdward 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.-Early years:...
in 1936 (likely at the urging of Tizard) developed a miniaturized radar system suitable for aircraft, the so-called Airborne Interception (
AI) set. At the same time Bowen developed radar sets for aircraft to detect submarines, the Air to Surface Vessel (
ASV) set, making a significant contribution to the
defeatThe Battle of the Atlantic was the longest continuous military campaignof World War II,...
of the German U-boats.
Initial AI sets were available in 1939 and fitted to
Bristol BlenheimThe 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 later adapted into a successful long-range and night fighter...
aircraft, replaced quickly with the better performing
Bristol BeaufighterThe 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.
MosquitoThe de Havilland Mosquito was a British combat aircraft that excelled in versatility during the Second World War. Originally conceived as an unarmed fast bomber, the Mosquito adapted to many other roles in during the air war in both the Pacific theatre of Operations and the European theatre,...
night intruders were fitted with
AI Mk VIII and later derivatives which, along with a device called "
SerrateSerrate was an Allied radar detection and homing device, used in Allied nightfighters to track German night fighters equipped with Lichtenstein during World War II....
" to allow them to track down German night fighters from their
LichtensteinLichtenstein 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...
B/C and SN2 radar emissions, as well as a device named "Perfectos" that tracked German
IFFIn telecommunications, identification, friend or foe is a cryptographic identification system designed for command and control. It is a system that enables military, and national interrogation systems to distinguish friendly aircraft, vehicles, or forces, and to determine their bearing and range...
, allowed the Mosquito to find and destroy German night fighters. As a countermeasure the German night fighters employed
Naxos ZRThe FuG 350 Naxos radar detector was a World War II German counter measure to SHF band centimetric wavelength radar produced by a cavity magnetron....
radar detectors.
Centimetric radar
The next major development in the history of radar was the invention of the cavity magnetron by John Randall and
Harry BootHenry 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 which generated
microwaveMicrowaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300MHz and 300 GHz. This is an extremely broad definition including both UHF and EHF , and various sources use different boundaries...
frequencies much more efficiently than previous devices, allowing the development of practical
centimetricA centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of...
radar, which operates 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
antennasAn antenna is a transducer designed to transmit or receive electromagnetic waves. In other words, antennas convert electromagnetic waves into electrical currents and vice versa. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless...
than the earlier lower frequency radars, and the cavity magnetron is the single most important invention in the history of radar and played a major part in the Allies' victory. It was given
free as a giftThe Tizard Mission officially the British Technical and Scientific Mission was a British delegation that visited the United States during the Second World War to get American resources to develop important military technology developed in the UK. It got its popular name from the instigator Henry...
to the US in 1940 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 that
Edward George BowenEdward 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.-Early years:...
was sent as the radar expert in the
Tizard MissionThe Tizard Mission officially the British Technical and Scientific Mission was a British delegation that visited the United States during the Second World War to get American resources to develop important military technology developed in the UK. It got its popular name from the instigator Henry...
to the USA in 1940, which resulted in the creation of the
MITThe 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 research...
Radiation LabThe 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. It was formed by, and initially operated under, the National Defense Research Committee , a...
to develop the device further. Half of the radar deployed during World War II were designed at the RadLab, including over 100 different radar systems costing $1.5 billion.
At about the same time
Robert M. PageRobert Morris Page was an American physicist who was a leading figure in the development of radar technology.-Life and career:...
invented the duplexer switch at the U.S. Naval Research Laboratory, allowing a pulse transmitter and receiver to share the same antenna without destabilizing the sensitive receiver.
The combination of the magnetron, the duplexer switch, small antennas and high resolution allowed small high quality radars to be installed in aircraft. They could be used by
maritime patrolMaritime 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
periscopeA periscope is an instrument for observation from a concealed position. In its simplest form, it is a tube in each end of which are mirrors set parallel to each other at 45 degree angle....
, which allowed aircraft to attack and destroy submerged submarines which had previously been undetectable from the air. Centimetric
contour mappingA 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...
radars like
H2SH2S was a radar system used in various British 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 campaignStrategic bombing during World War II is a term which refers to all aerial bombardment of a strategic nature, which took place 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 fuzeA 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 bombThe Fieseler Fi 103, better known as V-1 , colloquially know in Britain as the 'Doodlebug', was an early cruise missile used during World War II. The V-1 was developed at Peenemünde by the German Luftwaffe during the Second World War. Between 13 June 1944 and 29 March 1945, it was fired at...
flight paths to
London[]London is the capital of England and the United Kingdom. It has been a major settlement for two millennia, and the history of London goes back to its founding by the Romans, when it was named Londinium. London's core, the ancient City of London, the 'square mile', retains its medieval boundaries...
, are credited with destroying many of the flying bombs before they reached their target.
Germany
German developments mirrored those in the United Kingdom, but it appears radar received a much lower priority until later in the war. The
Freya radarFreya was an early warning radar deployed by Germany during World War II, named after the Norse Goddess Freyja. During the war over a thousand stations were built. A naval version operating on a slightly different wavelength was also developed as Seetakt...
was much more sophisticated than its CH counterpart, and by operating in the 1.2–m wavelength (as opposed to ten times that for the CH) around 250 MHz the Freya was able to be much smaller and yet offer better resolution. Yet by the start of the war only eight of these units were in operation, offering much less coverage.
Compared to the British PPI systems, the German system was far more labour intensive. 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 sophisticated as the one set up by Watson-Watt before the war.
This state of affairs did not last long. By 1940 the RAF's night raids were becoming a nuisance, and action was finally taken to address the problem.
Josef KammhuberGeneral Josef Kammhuber was the first General of the Night Fighters in the Luftwaffe during World War II...
was promoted to become the General of the Night Fighters and set about creating a network of Freya radar stations in a chain of "cells" through Holland, Belgium and France. Known as the
Kammhuber LineThe Kammhuber Line was the name given to the German night air defense system established in July 1940 by Colonel Josef Kammhuber.The first version of the Line consisted of a series of radar stations with overlapping coverage, layered three deep from Denmark to the middle of France, each covering a...
, each cell of the network contained a radar and a number of searchlights, as well as one primary and one backup night fighter. When a bomber was detected flying into the cell the searchlights were directed by the radar to pick it up, at which point the night fighter could see the now-lit bomber.
While somewhat effective, the system was useless during bad weather or other times where the light would be blocked. In order to address this problem, the
Würzburg radarThe 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...
was developed. Würzburg was a short-range radar mounted on a highly directional
parabolic antennaA parabolic antenna is a high-gain reflector antenna used for radio, television and data communications, and also for radiolocation , on the UHF and SHF parts of the electromagnetic spectrum...
that was sensitive in only one direction. This made it useless for finding the targets, but once guided to one by an associated Freya it could track it with extreme accuracy: later models were accurate to 0.2 degrees or less.
Two Würzburgs were assigned to each cell, one to track the target bomber, and another the night fighter. By plotting the location of both aircraft on a common plotting table, radio operators could direct the fighter manually to the target. The downfall of the Kammhuber Line was that it could only track a single target per Würzburg. When the British learned of this, they directed operations such that all their bombers concentrated on crossing the line
en masse over as few cells as possible. This
bomber streamThe bomber stream was a tactic developed by the Royal Air Force Bomber Command to overwhelm the German aerial defences of the Kammhuber Line during World War II....
introduced in mid 1942 meant that as a raid developed, only a few night fighters could be directed into the raid at any one time, and bomber losses dropped to a handful per raid.
Airborne radars
The use of the accurate Freya and Würzburg allowed the Germans to have a somewhat more lackadaisical approach to the development of an 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 system, and the development of an airborne system became much more important.
Early
Lichtenstein BCLichtenstein 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...
units were not deployed until 1942, and as they operated on the 2–m wavelength (150–MHz) they required large antennas. By this point in the war the British had become experts on
jammingJamming may mean:* Interfering with communications or surveillance:** Radio jamming** Radar jamming and deception** Mobile phone jammer** E-mail jamming* Jamming , cheered show-offs during social dancing...
German radars, and when a BC-equipped Ju 88 night fighter landed in Britain one foggy night, it was only a few weeks before the system was rendered completely useless. By late 1943 the Luftwaffe was starting to deploy the greatly improved
SN-2, but this required huge antennas that slowed the planes as much as 50–km/h. Jamming the SN-2 took longer, but was accomplished. A 9–cm wavelength system known as
Berlin was eventually developed, but only in the very last months of the war.
US
thumb
After early U.S. work on radar conducted in the twenties at the Naval Research Laboratories, the success of Robert Page's pulsed radar experiment in 1934 redirected the attention of the Signal Corps, who had been focusing more on use of sound and heat to detect aircraft. Expertise in radio equipment design by the signal corps led to rapid development of an early type of VHF radar at
Fort MonmouthFort Monmouth is an installation of the Department of the Army in Monmouth County, New Jersey. The post is surrounded by the communities of Eatontown, Tinton Falls and Oceanport, New Jersey, and is located about one mile from the Atlantic Ocean. The post covers nearly of land, from the Shrewsbury...
and
Camp EvansCamp Evans, New Jersey is a former military base associated with Fort Monmouth. It is located in Wall Township, although it is often said to be located in Belmar. The property overlooks the Shark River.Camp Evans is named after the late Lt. Col...
in
New JerseyNew Jersey is a state in the Mid-Atlantic region of the United States. It is bordered on the north by New York, and to the east by the Hudson River, Upper New York Bay, the Kill Van Kull, Newark Bay, the Arthur Kill, Raritan Bay, Sandy Hook Bay, Westchester County, New York City, Long Island, and...
for use with
coastal artilleryCoastal artillery is the branch of armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications....
.
By 1940 when the British and US began technology exchanges, the British were surprised to learn they were not unique in their possession of practical pulse radar technology. The U.S. Navy's pulse radar system, the
CXAM radarThe 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 technology. The British were much further ahead on microwave research necessary for the second generation of military radars. Although the US Navy had produced by 1940 an experimental 10–cm radar, they were stymied by the problem of insufficient transmitter power. On entry to World War II, the army and navy had working first generation radar units in front line units, and this technology was relied on throughout the war. The army's type
SCR-270 radarThe SCR-270 was one of the first operational early warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world...
detected the Japanese planes attacking Pearl Harbor at a range of , although this information was not used effectively at the command level. After the war this unit was employed in the first application of radar in astronomy by bouncing radio waves off the Moon in 1946.
Although the US had developed pulsed radar systems independent of the British as had the Germans, there were serious weaknesses in their efforts - the greatest of which was the lack of integration of radar into unified air defense system. Here the British were without peer. The result of the Tizard Mission in 1940 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. In particular, the cavity magnetron was the answer the US was looking for, and it led to the creation of the
MIT Radiation LabThe 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. It was formed by, and initially operated under, the National Defense Research Committee , a...
, a major center for research employing almost 4,000 people at its peak during the Second World War.
It was in 1942 that the
neologismA neologism ; from Greek νές is a newly coined word that may be in the process of entering common use, but has not yet been accepted into mainstream language. Neologisms are often directly attributable to a specific person, publication, period, or event...
and acronym
RADARRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
was coined by the U.S. Navy. The acronym RADAR is still in use by the US Navy, and as a mnemonic device to describe its components, they have come up with a new acronym, ARMPIT (Antenna, Receiver, Modulator, PowerSupply, Indicator, Transmitter).
Japan
Well prior to World War II, Japan had knowledgeable researchers in the technologies necessary for radar but due to lack of appreciation of radar's potential, and rivalry between army, navy and civilian research groups, Japanese technology was 3 to 5 years behind that of the US during the war. The Japanese captured a British type
gun layingGun laying is the process of aiming an artillery piece. The term is also applied to describe the process of aiming smaller calibre weapons by radar or computer control...
radar in Singapore as well as an American
SCR-268The 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....
and
SCR-270The SCR-270 was one of the first operational early warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world...
when they overran the Philippines. In August 1942, US marines captured a Japanese Navy Type 1 model 1 radar, and though judged to be crude even by the standards of early US radars, the fact the Japanese had any radar capability came as a surprise.
One leader in radar technology was
Hidetsugu YagiHidetsugu 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...
, a researcher of international stature who was working on applications of power transmission via microwave in the early 1930s. Though his project was overly ambitious, the work he did was directly applicable to advanced microwave radars. The papers he delivered in the late 20s in the US on antennas and magnetron design were closely studied by US researchers. His work was given so little attention by Japanese military researchers that when the Japanese captured the British radar unit in Singapore, at first they were unaware that the "Yagi" antenna mentioned in captured manuals referred to a Japanese invention. Although progress was rapid after the value of radar was better appreciated, research continued to be impeded by inter-service rivalry and new units, though capable, were too late to influence the outcome of the war. Radar was used by the army for
gun layingGun laying is the process of aiming an artillery piece. The term is also applied to describe the process of aiming smaller calibre weapons by radar or computer control...
and aircraft detection, by the navy for detection of air and sea threats on all major capital ships, including use of centimetric units in 1944. Towards the end of the war, units were sufficiently miniaturized for airborne intercept (FD-2) radar on
J1N1-S GekkoThe Nakajima J1N1 Gekko was a twin-engine aircraft used by the Japanese Imperial Navy during World War II and was used for reconnaissance, night fighter, and kamikaze missions. The first flight took place in May 1941...
night fighters and airborne ship detection radar in
G4M2 "Betty" bombersThe Mitsubishi G4M or 一式陸攻 Ichishiki rikujō kōgeki ki, Isshikirikkō was the main twin-engine, land-based bomber used by the Imperial Japanese Navy Air Service in World War II...
and
Kawanishi H8KThe Kawanishi H8K was an Imperial Japanese Navy flying boat used during World War II for maritime patrol duties...
patrol planes.
Canada
Little radar research was done in Canada prior to the start of WW2. However, in 1939 the National Research Council of Canada was tasked with developing a Canadian designed radar system. After the fall of France in June 1940, radar research was given the highest possible priority, leading to the development and deployment of a series of radar systems, including the CSC type and SW1C naval radars, which were operationally deployed on RCN ships in 1941, placing Canada into the forefront of naval radar deployment.
Cold War
After World War II the primary "axis" of combat shifted to lie between the United States and the
Soviet UnionThe Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the , tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, abbreviated СССР, SSSR. The common short name is Soviet Union, from , Sovetskiy Soyuz...
. In order to provide early warning of an attack, both sides deployed huge radar networks of increasing sophistication at ever-more remote locations. The first such system was the
Pinetree LineThe Pinetree Line was a series of radar stations located across the northern United States and southern Canada at about the 50th parallel, along with a number of other stations located on the Atlantic and Pacific coasts. Run by NORAD , over half were manned by United States Air Force personnel with...
deployed across
CanadaCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
in the 1950s, backed up with radars on ships and oil platforms off the east and west coasts. The Pinetree Line was a simple system and was vulnerable to jamming, so the more sophisticated
Mid-Canada LineThe Mid-Canada Line, also known as the McGill Fence, was a line of radar stations across the "middle" of Canada to provide early warning of a Soviet bomber attack on North America. It was built to supplement the less-advanced Pinetree Line, which was located further south...
(MCL) was set up to supplant it. However, the MCL was not considered to be militarily very useful, and the DEW Line started construction soon after, in the high Arctic. Construction of the DEW line is still considered one of the great logistics and civil engineering projects of the 20th century. In the late 1950s, the
Ballistic Missile Early Warning SystemThe United States Air Force Ballistic Missile Early Warning System was the first operational ballistic missile detection radar. The original system was built in 1959 and could provide long-range warning of a ballistic missile attack over the polar region of the northern hemisphere. They also...
was added to warn of ICBM launches.
See also
- synthetic aperture radar
Synthetic-aperture radar is a form of radar in which multiple radar images are processed to yield higher resolution images than would be possible by conventional means...
- List of World War II electronic warfare equipment
- Alan Blumlein
Alan Dower Blumlein was an English electronics engineer, notable for his many inventions in telecommunications, sound recording, stereo, television and radar...
- Secrets of Radar Museum
The Secrets of Radar Museum is a small military museum located near Parkwood Hospital in London, Ontario, Canada. Founded in 2003, the museum exists to tell the story of the 6000+ Canadian World War II veterans who were recruited into a top-secret project during World War II involving radar...
- German inventors and discoverers
This is a list of German Inventions and Discoveries of German people or inventors/discoverers of German heritage in alphabetical order of the surname. The main section includes existing articles, indicated by blue links and possibly non-existing, indicated by red links...
Further reading
- ES310 "Introduction to Naval Weapons Engineering.". (Radar fundamentals section)
- Yves Blanchard, "Le radar. 1904-2004 : Histoire d'un siècle d'innovations techniques et opérationnelles", éditions Ellipses, 432 pages (in French)
- Barrett, Dick, "All you ever wanted to know about British air defence radar". The Radar Pages. (History and details of various British radar systems)
- Bowen, E.G.
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.-Early years:...
, Radar Days, Institute of Physics Publishing, Bristol, 1987., ISBN 0-7503-0586-X
- Bragg, Michael., RDF1 The Location of Aircraft by Radio Methods 1935-1945, Hawkhead Publishing, Paisley 1988 ISBN 0-9531544-0-8 The history of ground radar in the UK during WWII
- Louis Brown, A Radar History of World War 2 - Technical and Military Imperatives, 1999, Institute of Physics Publishing, Bristol & Philadelphia ISBN 0-7503-0659-9
- Robert Buderi: The invention that changed the world: the story of radar from war to peace, Simon & Schuster, 1996. ISBN 0-349-11068-9
- Clark, Maj. Gregory C., Deflating British Radar Myths of World War II, 1997, http://www.radarpages.co.uk/download/AUACSC0609F97-3.pdf
- Ronald Clark, Tizard (London, 1965). An authorized biography of radar's champion in the 1930s.
- G W A Dummer
Geoffrey William Arnold Dummer, MBE , C.Eng., IEE Premium Award, FIEEE, MIEE, USA Medal of Freedom with Bronze Palm was a British electronics author and consultant who is credited as being the first person to...
, Electronic Inventions and Discoveries
- Sir Charles Frank, Operation Epsilon: The Farm Hall Transcripts
- Robert Hanbury Brown
Robert Hanbury Brown, AC was a British astronomer and physicist born in Aruvankadu, India. He studied electrical engineering at the University of London, from where he received a Master's degree in telecommunication in 1935. From 1936 to 1942 he worked for the Air Ministry, where he helped to...
, BoffinIn the slang of the United Kingdom, Australia, New Zealand and South Africa, boffins are scientists, engineers, and other people engaged in technical or scientific research. The word 'boffin' can also be used to refer to any particularly clever person...
: A Personal Story of the early Days of Radar and Radio Astronomy and Quantum Optics
- Howse, Derek, Radar At Sea The Royal Navy in World War 2, Naval Institute Press, Annapolis, Maryland, USA, 1993, ISBN 1-55750-704-X
- R.V. Jones, Most Secret War. R.V. Jones's account of his part in British Scientific Intelligence between 1939 and 1945, working to anticipate the German's radar, radio navigation and V1/V2 developments.
- Harry von Kroge, GEMA: Birthplace of German Radar and Sonar
- Latham, Colin & Stobbs, Anne., Radar A Wartime Miracle, Sutton Publishing Ltd, Stroud 1996 ISBN 0-7509-1643-5 A history of radar in the UK during WWII told by the men and women who worked on it.
- Colin Latham and Anne Stobbs, The Birth of British Radar: The Memoirs of Arnold 'Skip' Wilkins
Arnold Frederic Wilkins O.B.E., was a pioneer in developing the use of radar.He was the son of John Knowles Wilkins of Chester and was educated at The King's School, Chester and St...
, Speedwell for the Defence Electronics History Society 2006, ISBN 0953716627
- Sir Bernard Lovell
Sir Alfred Charles Bernard Lovell, OBE, FRS is an English physicist and radio astronomer. He was the first Director of Jodrell Bank Observatory, from 1945 to 1980.- Career :...
, Echoes of War - The History of H2S
- Pritchard, David., The Radar War Germany's Pioneering Achievement 1904-1945 Patrick Stephens Ltd, Wellingborough 1989., ISBN 1852602465
- C. F. Rawnsley & Robert Wright, Night Fighter
- Swords, Seán S. "Technical History of the Beginnings of Radar". London: P. Peregrinus on behalf of the Institution of Electrical Engineers, IEE History of Technology Series, 1986
- Zimmerman, David., Britain's Shield Radar and the Defeat of the Luftwaffe, Sutton Publishing Ltd, Stroud, 2001., ISBN 0-7509-1799-7
- Brown, Jim, Radar - how it all began, ISBN 1-85756-212-7
External links