Freya radar

Freya

A 1941 RAF PRU photograph of the two Freyas at Auderville
Country of origin	Germany
Introduced	1939
No.built	1,000+
Type	Early warning radar
PRF	500 per second
Pulsewidth	2–3μs
Range	200 kilometres (120 mi)
Azimuth	360°
Power	20 kW
Other Names	Funkmessgerät 80 (FuMG 80)

Freyawas anearly warning radardeployed by Germany during World War II;it was named after the Norse goddessFreyja.During the war, over a thousand stations were built. A naval version operating on a slightly different wavelength was also developed as theSeetakt.

Development

First tests of what would become the "Freya"were conducted in early 1937, with initial delivery of an operational radar to theKriegsmarinein 1938 by the GEMA company. Freya supported an early version ofIdentification friend or foe(IFF). Aircraft equipped with theFuG 25a "Erstling"IFF system could be successfully queried across ranges of over 100 km.

The "AN" version gained a switchable phasing line for the antenna. Switching in the phasing line led to a phase displacement of the antenna's radiation pattern and with that, asquintingto the left or right. This enabled the system in effect to switch from the rather broad "scanning for maxima" to narrowlobe switching.In that mode, a skilled operator could achieve an angular resolution of 0.1°.

TheFreyaradar was more advanced than its British counterpart,Chain Home.Freyaoperated on a 1.2 m (3.9 ft) wavelength (250 MHz) while Chain Home used 12 m. This allowedFreyato use a much smaller antenna system, one that was easier to rotate, move and position. It also offered higher resolution, allowing it to detect smaller targets. Because of its complex design, only eightFreyastations were operational when the war started, resulting in large gaps between the covered areas. The British Chain Home radar, although less advanced and more prone to errors, was simpler, which meant that the complete Chain Home network was in place in time for theBattle of Britain.

Variants

• FuMG 450FreyaAN, initially called FuMG 41G (range increased to 120 km)
• FuMGFreyaLZ (could be disassembled for airlift)
• FuMG 480
• FuMG 44 "Drehfreya"(German:" rotatingFreya"), transitional model to FuMG 44/404 (navy: FuMO371),"Jagdschloss"PPI radar
• FuMG 451 "Freiburg", 162–200 MHz
• FuMG 321-328 (German naval designation)

Deployment and operation

Freyawas often used in concert with the primary Germangun laying radar,Würzburg Riese( "Würzburg Giant" ); theFreyafinding targets at long distances and then "handing them over" to the shorter-ranged Würzburgs for tracking.

Later in the war,Freyaoperated in the band from 2.5 to 2.3 m (8.2 to 7.5 ft) (120 to 130MHz), with a pulse width of threemicroseconds,a peak power output of 15 to 20kW,and apulse repetition frequencyof 500 Hz. It had a maximum range of only 160 kilometers (99 mi), making it inferior to Chain Home. Furthermore, it could not accurately determine altitude, but it was a fully steerable and semi-mobile system.

Freya(right) andWürzburg-Riese,Romania, 1944

Freya was first successfullyused on December 18, 1939when two stations detected an approaching daytime raid onWilhelmshavenby 22RAFVickers Wellingtonbombers at a range of 113 km and guided fighter planes toward them via radio.Only half of the Wellingtons returned to Britain undamaged, but the German fighters only reached the bomber after they had made their bombing run on ships in harbour. The performance of Freya left theLuftwaffeso impressed that, by the Spring of 1940, elevenFreyastations were installed to guard Germany's western border.After the invasion of France in 1940, additionalFreyastations were built along the Atlantic coast. When Britain started its bombing raids,Hermann Göringordered Colonel (later General)Josef Kammhuberto install an efficient air defence. This led to the so-calledKammhuber Lineinto which moreFreyastations were incorporated. In the later course of the war,Freyadevices turned out to be vulnerable tochaff,along with other countermeasures, which meant they could still be used for early warning, but no longer for guiding fighter planes. British bombing raids could also be organized such that the Kammhuber Line could be overwhelmed in massed raids.

British intelligence

One of the first to give British intelligence any details about theFreyaRadar was a young Danish Flight Lieutenant,Thomas Sneum,who, at great risk to his life, photographed radar installations on the Danish island ofFanøin 1941. He brought the negatives to Britain in a dramatic flight which is fictionalized inKen Follett's novelHornet Flight.Sneum's deed is also mentioned inR. V. Jones'sMost Secret Waras a 'most gallant exploit' and is one of the featured stories in Courage & Defiance by Deborah Hopkinson.

Further development

FuMG 401 "Freya-Fahrstuhl"(German:Freyaelevator)

• FuMG 401: For experiments with beam reflection on the ground, leading to a change in elevation angle, aFreyaantenna array was installed on a wooden support so it could slide up and down. This enabledFreyato detect the target's altitude without the aid of other devices (such as Würzburg radars).
• FuMG 41: In an attempt to increase the range without changing the transmitter, severalFreyaantenna arrays were switched together. These installations, called"Wassermann"(German: Aquarius), not only had greater range but were also more accurate.

Countermeasures

To counterFreya,the British used equipment called 'Moonshine'. Carried byBoulton Paul Defiantaircraft of the Special Duties Flight (laterNo. 515 Squadron RAF), a single set retransmitted a portion of theFreyasignal amplifying the apparent return. Eight planes with 'Moonshine' could mimic a force of 100 bombers.A second countermeasures system,"Mandrel"was a noise jammer carried by aircraft ofNo. 100 Group RAFwhich overwhelmed the signals fromFreya.Individual aircraft were sent to orbit fixed positions 50 miles (80 km) off the enemy coast. By using nine aeroplanes, a 200-mile (320 km) gap could be knocked into the German's radar coverage, while further jammers were carried in the bomber stream to counter the inlandFreyanetwork.

• 
  A PoleFreyaradar
• 
  A LimberFreyaradar

Post-war use

One FuMG 80 Freya radar, after modification, was installed in 1957/8 at theOndřejov ObservatoryinCzechoslovakiaand served as meteorite tracking radar until 2006. Before then it was used at thePardubice Airport,under name RZ III.

Bibliography

• Brew, Alex.The Defiant File.Tunbridge Wells, Kent, UK: Air-Britain (Historians), 1996.ISBN0-85130-226-2.
• Price, Alfred.Instruments of Darkness: The History of Electronic Warfare.St Albans, UK: Granada, 1979.ISBN0-586-04834-0.
• Swords, Sean S.Technical History of the Beginnings of Radar,London: IEE/Peter Peregrinus, 1986.ISBN0-86341-043-X.
• Fritz Trenkle:Die deutschen Funkführungsverfahren bis 1945,Dr. Alfred Hüthig Verlag, Heidelberg 1987,ISBN3-7785-1647-7
• Harry von Kroge:GEMA-Berlin – Geburtsstätte der deutschen aktiven Wasserschall- und Funkortungstechnik,1998,ISBN3-00-002865-X
• Helmut Bukowski:Radarkrieg und Nachtluftverteidigung,VDM Verlag, Zweibrücken 2007,ISBN978-3-86619-012-2

See also

• Würzburg radar
• List of World War II electronic warfare equipment
• Operation Taxable
• Operation Glimmer
• Battle of the Beams

External links

• Deflating British Radar Myths of World War IIArchived2010-08-20 at theWayback MachineA comparison of contemporary British and German radar technologies and their use
• Das Jahrhundert des Radars von Dr. Wolfgang Holpp, EADS(PDF-Datei; 3,6 MB)
• Ehemalige Standorte von Radaranlagen