Freya (radar)

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Freya LZ

The Freya radio measuring device was an early development of radar technology in the German Reich . The code name Freya comes from the Nordic goddess Freya , who is said to have the ability to see at night. Over a thousand devices were installed during the Second World War .

development

First tests of the early warning radar developed by the two engineers and managing directors of the Berlin company GEMA ( Society for electroacoustic and mechanical apparatus mbH ) Paul-Günther Erbslöh (1905–2002) and Hans-Karl von Willisen (1906–1966), later known as Freya , found Held in early 1937. The first station was delivered to the Navy in 1938. The Freya radar was technically more advanced than its British counterpart Chain Home . It was operated with a wavelength of 1.2 m, the Chain Home, on the other hand, with 12 m (smaller wavelength => higher resolution: smaller objects were also recognizable).

When the war began, only eight Freya devices were in use; they could only cover the areas to be monitored very incompletely. The British chain home radar was designed more simply and more error-prone than Freya; but it could be quickly installed as Freya and was the beginning of the Battle of Britain ( "Battle of Britain") fully operational (See Chain Home ).

Technical specifications

FuMG 80 "Freya"
Send frequency 250 MHz
wavelength 1.2 m
Pulse power 20 kW
Pulse repetition rate 500 Hz
Pulse duration 3 μs
Swivel range 360 ° mechanical
Opening angle 0.5 °
Range 160 km

technology

Freya antenna system
  • The height of approaching aircraft could not be precisely determined. In it it was inferior to the Chain Home, but it was completely swiveling (panoramic radar) and could also be used mobile.
  • The FuG 25a "Erstling" device was installed as an additional device in own aircraft . This secondary radar device (or IFF device ) responded to the Freya pulses and responded on 156 MHz. This enabled an identification range of well over 100 km to be achieved.
  • With the "AN" version, the antenna was given a detour and an antenna switch. The connection of the detour line causes a phase shift of the antenna diagram and thus a squint to the left or right. It was thus possible to switch from the wide maximum bearing to the narrow minimum bearing . A trained observer could achieve a bearing sharpness of 1/10 °.

variants

  • FuMG 450 Freya AN, initially called FuMG 41G (increased range of 120 km)
  • FuMG Freya LZ (can be dismantled for air transport)
  • FuMG 480
  • FuMG 44 "Drehfreya" transition to FuMG 44/404 (Marine FuMO371), "Jagdschloss" surveillance radar
  • FuMG 451 “Freiburg”, 162-200 MHz
  • FuMG 321-328 (Kriegsmarine designation)

commitment

Freya device (right) and Würzburg giant , place and date unknown

The first successful operation was recorded on December 18, 1939, when 24  Vickers Wellington bombers of the Royal Air Force were located at a distance of 113 km by two Freya devices and then Luftwaffe fighters were guided to the bombers by radio . After the aerial battle over the German Bight , only half of the Wellingtons returned to Great Britain undamaged. This achievement made such an impression on the Luftwaffe command that eleven Freya devices had already been installed in the spring of 1940 to secure the German western border. After the conquest of France in 1940, Freya devices were also installed along the Atlantic coast. With the advent of British air raids, Hermann Göring commissioned Colonel (later General) Josef Kammhuber to build a more effective air defense system. This led to the creation of the so-called Kammhuber line , into which further Freya devices were then integrated. In the course of the war, the Freya devices proved to be susceptible to interference against chaff , so that they could still be used for early warning, but less for the hunter management.

discovery

One of the first to report to the British intelligence service about the Freya radar system was the young Danish pilot lieutenant Thomas Sneum (1917-2007). Sneum photographed a Freya installation on the Danish island of Fanø in 1941 at high personal risk and took the photo negatives on a dramatic flight to England in June 1941. His deeds were recognized by British physicist and intelligence officer RV Jones in his book Most Secret War . The dramatic flight was also described in Ken Follett's book Midnight Hawks (originally: Hornet Flight ).

Interference suppression measures

In order to reduce the influence of hostile disruptive measures (chaff), various additional devices were developed.

  • louse
  • Test louse
  • Flash of light

Further development

FuMG 401 "Freya elevator"
  • FuMG 401: For experiments on beam reflection on the floor and thus a change in the elevation angle, a Freya antenna field was mounted on a wooden frame so that it can be moved. As a result, an altitude bearing of the flight destination could be achieved without the aid of other radar devices (e.g. Würzburg ).
  • FuMG 41: To improve the range without changing the transmitter, several antenna fields were interconnected by Freya. These systems, known as “Wassermann” , were able to increase both range and bearing accuracy.

Picture gallery

  • Two Freya radars in Auderville (1941)

  • Freya on the Channel coast near Calais

  • Freya Köthen version for long-distance detection with additional 95 MHz antenna and 15 kW transmission power

  • Bunkered Freya LZ position in Denmark

See also

swell

  1. ^ Harry von Kroge: GEMA-Berlin. Birthplace of German active waterborne sound and radio location technology. Hamburg 1998
  2. ↑ The Radar War by Gerhard Hepcke, translated into English by Hannah Liebermann (PDF; 137 kB)
  3. ↑ Description of the first German radar devices
  4. ↑ a b Entry in Dansk Biografisk Leksikon (3rd edition 1979–1984)
  5. ^ RV Jones: Most Secret War , 1st ed. 1978 (2011: ISBN 978-0-14-104282-4 ).
  6. ↑ http://www.cdvandt.org/Radar%20news%20No%2019%20modi.pdf

literature

  • Fritz Trenkle : The German radio control procedures until 1945. Dr. Alfred Hüthig, Heidelberg 1987, ISBN 3-7785-1647-7 .
  • Harry von Kroge: GEMA - Berlin. Birthplace of German active waterborne sound and radio location technology. H. von Kroge, Hamburg 1998, ISBN 978-3-00-002865-6 .
  • Helmut Bukowski: Radar warfare and night air defense over Berlin 1939 to 1945. (Procedure and technology for night protection of Berlin against air raids). VDM Nickel, Zweibrücken 2007, ISBN 978-3-86619-012-2 .

Web links

Commons : Freya (Radar)  - collection of images, videos and audio files