Metox

Metox ( named after the Parisian manufacturer) was the name of the radio measurement observation device FuMB one of the Navy. This radar detector was used from 1940 on surface units and from August 1942, German U- boats, to thereby locate the light emitted by ships, aircraft or land stations, radar waves can. The origin of the signal ( friend / enemy ) could not be determined.

Service history and technical data

Receiver

The Metox device R203 was designed for use for the Air Force and worked in the wavelength range from 1.88 m to 5 m.

The Metox receiver R600 worked in the meter wave band (0.62 m to 2.65 m wavelength, 113 MHz to 484 MHz frequency, current Very High Frequency ) as a superheterodyne receiver. It was from an audible warning which was received by the listener through headphones or connected to the speaker system.

The improved Metox R600A, which was used from February 1943 decreed among other things, an additional cathode ray tube as a visual display, which was called magic eye.

In use, the entire wavelength range was always searched on the scale by means of a rotary knob. If a signal has construed the scale value could be translated into the associated wavelength or frequency reference to a table. Was the frequency is known, the sender could be identified.

Biscay Cross

The first provisional dipole antenna consisted of a simple wooden cross on which two dipoles ( horizontally and vertically polarized) were installed. The official designation was FuMBAnt 2 Honduras. Colloquially it was called the Southern Cross or Biscay Cross.

This antenna was attached to the front periscope block with a bracket and had to be rotated by 90 ° from one of the Seewachen at short intervals by hand. About the rotation of a rough direction of / was - 45 ° to determine what was considered sufficient since the Metox only held the position as a warning device. The antenna cable to Metox receiver had to be led through the open turret hatch. The antenna had to be dismantled and brought into the boat interior, before the submarine could dive. The wavelength range was 1.2 m to 4 m (80 MHz to 250 MHz ).

In the combination Metox and Biscay Cross thus a wavelength range from 1.2 m to 2.65 m could be covered. This allowed the British radar systems ASV MkI (1.5 m ) and ASV MkII ( 1.7 m), which found use on the aircraft of the British Coastal Command, are recorded. As safe ranges at sea 6-7 nautical miles were reported (11 km to 13 km). The Maximum range is located about 10 nautical miles have ( 18 km). The range depended mainly on the strength of the transmitter. A stationary air force station at Bordeaux was located at a distance of 80 km, a strong station at Cap Ivi (Mediterranean) to up to 60 Sm ( 110km! ).

Bali antenna

After a number of experiments with different antennas was finally installed in February 1943 as a replacement for the Biscay Cross a new pressure-resistant and permanently installed antenna: FuMBAnt3 Bali I. The sailors called this the antenna as colloquially as a bunny.

This Runddipol antenna consisted of two round rods were arranged among each other and covered with wire mesh and two vertical opposing rods that were placed on top. Your wavelength range was from 75 cm to 300 cm (100 MHz to 400 MHz). A direction determination was not possible with this antenna; However, the range of the overall system Metox Bali to have been significantly higher than with the Biscay Cross.

By March 1943, the device has been used with good success, but then failed more frequently, since va the tracking devices of the Allied aircraft were converted to the new ASV Mk III radar, which worked on the decimeter.

On the German side that led to the mistaken conclusion that the other side could the self stemming from the device pulses ( characteristic radiation ) field, since one with a Luftwaffe machine could locate the radiation of the Metox up to 70 km on the basis of a self- test. The B.d.U. therefore forbade the use of the devices on 31 July 1943.

Developments

As a result, more devices have been developed ( 8 FuMB Cyprus I Cyprus FuMB 9 II, FuMB 10 Borkum), which were always better shielded and shone therefore less and less, but at the cost of range. These devices all spoke not to the now commonly used by the Allies radar equipment in the decimeter ( 10 cm).

Only the FuMB 7 Naxos device that up to 12 cm covered the decimeter to 8 cm and was introduced in October 1943, the position of the U- boats improved again.