Naxos (radar detector)

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The "Naxos" radar detector ( Luftwaffe version: FuG 350 / Kriegsmarine type: FuMB 7 ) was a tracking device from the Telefunken company and was used by the German Air Force on board night fighters from autumn 1943 to detect allied bombers based on the emissions of their H2S - centimeter waves - Detect radars . The Fu nk m ess b eobachtungsgerät ( FuMB ) 7 used the Navy on submarines as a warning receiver against attacking submarine hunting aircraft.

background

During the Second World War, Great Britain practiced the strategy of bombing large German cities in order to break the perseverance of the population and to bring about a political overthrow ( moral bombing ). Since the Royal Air Force had no long-range escorts for daytime operations, the only option was to fly night attacks in order to keep aircraft losses within tolerable limits. However, the initial hit rates of these night attacks were extremely poor, and sometimes the right target was not even found. Given the low success rate, Britain developed newer and more accurate navigation techniques during the war. For this purpose, in addition to direction finding methods with stationary transmitters in Great Britain ( "Oboe" and "GEE" navigation), on-board radar devices installed directly in the bombers ( H2S device ) were also used.

On the German side, great efforts were made to eliminate the attacking bombers because of the heavy casualties among the civilian population and the enormous damage to property caused by the English night attacks. In addition to the constant reinforcement of the home flak , night hunting units were also set up and sometimes even day hunters were deployed in the so-called Wilde-Sau method . The apparently most successful defense method was seen in the form of their own night fighters (e.g. Bf 110 , He 219 ). Analogous to the English night bombers, the German night fighters were faced with the problem that they could hardly find their targets (in this case the enemy bombers) at night. This is why radar-based location methods were developed. Some of these location methods were based on emitting radar impulses themselves and using the reflected impulses to find the enemy aircraft, not the Naxos device.

functionality

Omnidirectional antenna "BALI" for radar detector Naxos on board U-505

The functionality of the “Naxos” was not based on the classic radar principle, which is based on the transmission of its own radar signals and the reception of the reflected pulses. Instead, the Naxos intercepted the radar pulses from the British H2S devices and thus supported the interceptors' approach to the target. The signals were received at 2500 - 3750 MHz = 12 - 8 cm wavelength. The frequency of the latest Allied radar device, developed without the knowledge of the Germans, which worked with a wavelength of 3 cm = 10 GHz, was no longer recorded.

The range was about 50 km. The device was designed as a stick antenna and installed on the back of the aircraft. Only the side angle could be measured; it was not possible to determine the distance or height. A total of 25 versions were developed. A variant used in relatively large numbers was the Naxos ZR, which also included a rearward warning device with an antenna built into the rear of the fuselage, but was only used on the Ju 88. A total of 700 pieces of the basic version Z and the ZR were used. The location accuracy was relatively low in all versions.

Development of the submarine weapon

After the BdU (commander of the submarines) only became aware of the downing of the Rotterdam machine with the decimeter radar on February 2, 1943, in June 1943 , hectic countermeasures began. The Naxos receiver suitable for this wavelength range was adopted by the Air Force as Naxos U and tested together with the already existing pressure-resistant Bali antenna - but without any success, as it was almost completely insensitive in the decimeter range. This led to further speculation about Allied location procedures and thus to further delays.

It was not until September 1943 that the Naxos was used again as the Naxos I , this time with a new auxiliary antenna FuMBAnt11 Finger . This, too, proved to be almost unsuitable with a range of 5 km to 8 km, which is why a new receiving antenna had to be developed again. This was finally available from February 1944 in the form of an oblique dipole antenna with parabolic mirror, called FuMBAnt24 Cuba I Fliege , and in combination with the Naxos receiver proved to be a very effective antidote to the Allied decimeter radar H2S with a range of 10 km to 20 km. This combination was called Naxos Ia .

Countermeasures

The simplest tactical countermeasure was to switch off your own H2S devices after a location. As a technical countermeasure on the British side, the use of new radar devices with even shorter wavelengths in the centimeter range was required.

As with the H2S decimeter radar, the Bomber Command was preferred for the new H2X centimeter radar (~ 3 cm wavelength). But with the ASV MkVI a more modern device was delivered to the Coastal Command, which u. a. had a control for the transmission strength in order to deceive the opponent.

According to the sources, it is unclear whether the successor device , the British 3 cm radar ASV MKVII, was actually still in use. The Americans, on the other hand, definitely use their AN / APS15 or its successor APS 20 . Of these devices, German names (according to their respective places of discovery): Meddo or Wiesbaden was known to the German side early on and also had an effective antidote from the start with the Mücke horn in combination with the Naxos receiver.

Further development

Since the Naxos was only able to roughly indicate the location of the enemy radar device, attempts were made to develop a more precise variant. A device called “Corfu” already existed as a ground receiver and had the required accuracy. A variant of this was tried out under the name FuG 351 "Korfu-Z". But it was probably not used.

The Navy foresaw the reduction of the wavelength of the Allied radars and therefore the Mücke horn antenna (FuMBAnt25 Cuba II) for the wavelength range 2 cm to 4 cm was developed at the same time as the fly antenna . This antenna could also be used with the Naxos receiver. The combination of the fly and mosquito antennae, each with a Naxos receiver, was finally called FuMB26 Tunis .

See also

literature

  • Jochen Brennecke: The turning point in the submarine war . Koehler's publishing company, 1994.

Web links

Individual evidence

  1. ↑ Minutes of the meeting from September 2, 1943: First Naxos-Z installed in Ju 88. (PDF; 234 kB)
  2. ^ Clay Blair : U-Boot Krieg 1942-1945 , 2004, ISBN 3-8289-0512-9 , p. 619
  3. ^ Gebhard Aders : History of the German Night Hunting 1917–1945 , 1st edition 1977, p. 271