Serrate was a

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

Allied An alliance is a relationship among people, groups, or states that have joined together for mutual benefit or to achieve some common purpose, whether or not explicit agreement has been worked out among them. Members of an alliance are called ...

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

detection and homing device used by

night fighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War) is a fighter aircraft adapted for use at night or in other times of bad visibility. Night fighters began to be used i ...

s to track

Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...

night fighters equipped with the earlier UHF-band ''BC'' and ''C-1'' versions of the

Lichtenstein radar The Lichtenstein radar was among the earliest airborne radars available to the Luftwaffe in World War II and the first one used exclusively for air interception. Developed by Telefunken, it was available in at least four major revisions, cal ...

. It allowed

RAF The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...

night fighters to attack their German counterparts, disrupting their attempts to attack the RAF's

bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped ...

force. The first Serrate systems were developed from the

AI Mk. IV radar Radar, Airborne Interception, Mark IV (AI Mk. IV), produced by USA as SCR-540, was the world's first operational air-to-air radar system. Early Mk. III units appeared in July 1940 on converted Bristol Blenheim light bombers, while the definit ...

, which just happened to have antennas almost perfectly suited to receiving the Lichtenstein signals. Serrate simply disconnected the display from the radar's own transmitter and receiver and connected it to one tuned to the Lichtenstein. This produced a display indicating the direction to the German aircraft, but not the range. By carefully watching the movement of the target on the display the operator could estimate the range in general terms, near or far. When it appeared the target was close enough, the display was reconnected to the Mk. IV's own electronics to provide both ranging and directional information during the last moments of the attack. Serrate operations began by No. 141 Squadron RAF on the night of 7 September 1943. 179 operational sorties yielded 14 claimed fighters shot down, for 3 losses. After that point, the Luftwaffe realized what was happening and quickly introduced new versions of their radars working on different frequencies. Unlike the earlier sets, which just happened to operate on frequencies very close to the British radars, the new sets required entirely new detectors, which took some time to develop. New versions of Serrate were introduced, and moved from the

Bristol Beaufighter The Bristol Type 156 Beaufighter (often called the Beau) is a British multi-role aircraft developed during the Second World War by the Bristol Aeroplane Company. It was originally conceived as a heavy fighter variant of the Bristol Beaufort ...

to the faster

de Havilland Mosquito The de Havilland DH.98 Mosquito is a British twin-engined, shoulder-winged, multirole combat aircraft, introduced during the Second World War. Unusual in that its frame was constructed mostly of wood, it was nicknamed the "Wooden Wonder", or ...

, but later operations were never as successful as the original ones. Later intruder operations were often directed by the

Perfectos Perfectos was a radio device used by Royal Air Force's night fighters during the Second World War to detect German aircraft. It worked by triggering '' Luftwaffe's'' FuG 25a Erstling identification friend or foe (IFF) system and then using the res ...

device instead of Serrate. This worked by triggering the German

IFF In logic and related fields such as mathematics and philosophy, "if and only if" (shortened as "iff") is a biconditional logical connective between statements, where either both statements are true or both are false. The connective is bicon ...

transceivers and receiving the reply on the same antennas as Serrate. As the timing of the request pulse was known, Perfectos revealed both the angle and range to the target, removing the need to switch to radar at the end of the approach.

Basic concept

The

was the first operational airborne interception radar, first used experimentally in April 1940 before entering widespread service in early 1941. These systems used a set of four receiver antennas that were arranged so they were most sensitive in different directions; two were sensitive above or below the aircraft, and the other two to the left and right. The output from these antennas was rapidly switched back and forth on the display, producing two ''blips'' for any given target, with the length of the blip indicating the strength of the signal in that direction. By comparing the length of the blips from, say, the upper and lower antennas, the operator could determine if the target was above or below their fighter. For purely practical reasons, the antennas were shorter than ideal. A

half-wave dipole In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole wi ...

for the system's 1.5 m wavelength signals should be about 75 cm, but antennas of this size produced considerable drag on the aircraft. As

gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...

was not a limiting issue due to other limitations of the system, smaller antennas were adopted, about 30 cm long. By chance, the Germans selected a 50 cm wavelength for their own AI radars, which made the Mark IV antennas almost perfectly suited for receiving their signals. The suggestion was made early on that the system could be modified to display the signals from the German radars simply by connecting the antennas and display to a receiver tuned to the German frequencies. By late 1941 a new generation of radars was appearing that were based on the new

cavity magnetron The cavity magnetron is a high-power vacuum tube used in early radar systems and currently in microwave ovens and linear particle accelerators. It generates microwaves using the interaction of a stream of electrons with a magnetic field while ...

instead of the traditional tube-based electronics of the Mk. IV. These operated at much shorter wavelengths, about 9 cm, thus requiring much smaller antennas while also providing much higher angular resolution. The production

AI Mk. VIII radar Radar, Airborne Interception, Mark VIII, or AI Mk. VIII for short, was the first operational microwave-frequency Airborne Interception radar, air-to-air radar. It was used by Royal Air Force night fighters from late 1941 until the end of World War ...

version became widespread by late 1942 and were installed primarily on the

, leaving the problem of what to do with the older

s mounting Mk. IV. This difficulty arose at the time that the use of the

H2S radar H2S was the first airborne, ground scanning radar system. It was developed for the Royal Air Force's Bomber Command during World War II to identify targets on the ground for night and all-weather bombing. This allowed attacks outside the range ...

was being debated within

Bomber Command Bomber Command is an organisational military unit, generally subordinate to the air force of a country. The best known were in Britain and the United States. A Bomber Command is generally used for strategic bombing (although at times, e.g. during t ...

, with the concern being expressed that an aircraft lost over Europe would reveal the secret of the magnetron to the Germans. At this point the idea of using the Mk. IV equipped Beaufighters as intruder aircraft was once again raised. Lacking a magnetron, these presented no security risk, and offered a reasonable way to use these now obsolete night fighters. This was aided by the landing of a fully intact Junkers Ju 88R-1 night fighter in May 1943 in Scotland, by its defecting crew, revealing the latest operational frequencies of the German radars. The technique described here is for the Monica

tail warning radar A tail warning radar, sometimes TW for short, was a short-lived class of aircraft-mounted radar systems used to provide warning of another aircraft approaching from the rear. They were mostly used on World War II bombers, starting with the Moni ...

: The technique developed was for the

nightfighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War) is a fighter aircraft adapted for use at night or in other times of bad visibility. Night fighters began to be used i ...

s to fly slowly off the

bomber stream The bomber stream was a saturation attack tactic developed by the Royal Air Force (RAF) Bomber Command to overwhelm the nighttime German aerial defences of the Kammhuber Line during World War II. The Kammhuber Line consisted of three layers of ...

, mimicking the characteristics of a

heavy bomber Heavy bombers are bomber aircraft capable of delivering the largest payload of air-to-ground weaponry (usually bombs) and longest range (takeoff to landing) of their era. Archetypal heavy bombers have therefore usually been among the larges ...

, until the rearward-facing ''Serrate'' (Monica) detector picked up the emissions from a ''

'' night fighter approaching. The Radar Operator would then pass directions to the pilot until the fighter was 6,000 feet behind, at which point the Beaufighter would execute a swift turn onto the tail of the German night fighter, pick up the enemy aircraft on his forward radar and attempt to down it. Serrate was also subsequently fitted to

nightfighters. No. 141 Squadron transferred to No. 100 Group

in late 1943 and during the

Battle of Berlin The Battle of Berlin, designated as the Berlin Strategic Offensive Operation by the Soviet Union, and also known as the Fall of Berlin, was one of the last major offensives of the European theatre of World War II. After the Vistula– ...

on the night of 16/17 December, a Mosquito crewed by Squadron Leader F. F. Lambert and Flying Officer K. Dear made Bomber Command's first successful Serrate-guided operational sortie when they damaged a

Bf 110 The Messerschmitt Bf 110, often known unofficially as the Me 110,Because it was built before ''Bayerische Flugzeugwerke'' became Messerschmitt AG in July 1938, the Bf 110 was never officially given the designation Me 110. is a twin-engine (Des ...

with cannon fire.Staff
Campaign Diary December 1943
, Royal Air Force Bomber Command 60th Anniversary web site. Retrieved 11 August 2008 The Serrate night fighter offensive preceded far greater and wide-ranging support operations by the specialist 100 Group during 1944-45.

References

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External links

Air interception radar in World War II night fighter aircraft
World War II British electronics Radar warning receivers Military equipment introduced from 1940 to 1944

Basic concept

See also

References

External links