E351 Korfu / FuG351

E351 Korfu
HISTORY

During an attach on Cologne on 2/3 February 1943, a German night fighter shout down a Sterling of No. 7 British squadron near Rotterdam in Holland. The German technicians began their routine investigation of the wreckage the next day they found a completely equipment new to them. Oberst Schwenke (Technical Office, Armament) reported the discovery to a high-level conference in Berlin nine days later. An initial examination of the equipment had reveled that British had built a radar operating on a frequency far higher than German scientific community had believed possible: “ I have report that a new device near Rotterdam. It is a centrimetic radar device mounted beneath the rear of the fuselage. We have not yet established its exact purpose, but the device is exceedingly expensive This is the first appearance of a decametric (i.e. 10 centimeter) apparatus for hitherto the British given no hint of mach progress in this field…Two units are missing from the equipment, our of total of six to eight”Generalfeldmarschall Milch asked whether that meant that the units had been lost, and Schwenke replied: “We salvaged the equipment for 80% wrecked aircraft. Two missing units, one of which was the display unit with the radar screen..”

E351 Korfu
British Radar H2S

This equipment was the first airborne, ground-mapping radar code named H2S. Centimetric radar, made possible by the cavity magnetron, allowed for the detection of much smaller objects and the use of much smaller antennas. The combination of small-cavity magnetrons, small antennas, and high resolution allowed small, high quality radars to be installed in aircraft.
The H2S Equipment code named Rotterdam by the Luftwaffe went to the Telefunken Company in Berlin for the examination. On 22 February 1943 Generalleurtnant Martini se up a special Rotterdam commission (Arbeitsgeinschaft Rotterdam) to devise the countermeasures. One of these was to release a special receiver in order to pick up the H2S Signals: the Korfu Receiver.
This radar search receiver was developed by Blaupunkt (Dr G
üllner and Dr. Lämmchen).
Production begins on June 1943 and was employed on Luftwaffe and Kriegsmarine.
The Equipment was produced in two versions. Both the receivers have the same type-number.

FUMG 351
E351 Korfu Early Version
E351 Korfu
E351 Korfu Late Version (Arthur Bauer Collection)

In function of the frequency band covered was provided the following versions:
E351C (Korfu 1218) for wavelength form 12 to 18cm (form 2500 to 1660 MHz)
E3S1 E (Korfu 812) for wavelength form 8 to 12cm (from 3750 to 2500MHz)
E 351 A (Korfu 68) for wavelength form 6 to 8 cm (form 5000 to 3750 MHz)
E 351 B (Korfu 46) for wavelength form 4 to 6 cm (form7500 to 5000 MHz)
E 351 D (Korfu 274) for wavelength 2,7 to 4 cm (form 11100 to 7500 MHz)
In late version Frequency ranges can be changed by exchanging the front-end plug-in, shown in the centre of the front-panel

E351 Korfu
E351 Korfu Antenna
E351 Korfu
E351 Korfu Statiion

TECHNOLOGY
Radio Receiver E351 Korfu is a double conversion super-heterodyne: first IF is 60 MHz, the second IF 40 MHz.

E351 Korfu

The reception is possible with AM or FM demodulation with outputs for headphones or oscilloscope. The receiver is equipped with 21 tubes: 13 EF 14; 2 EZ 12; 1 RD 2; 1 StV 280/40; 1 Detector XS 35. The used first local-oscillator magnetron, for all versions, is: RD2Md or RD2Md2.

E351 Korfu
This magnetron consist of four anodes grouped together connected onto an internal Lecher line. Outside is a second Lecher line arrangement, which is capacitive coupled to it. The tuning capacitor (left of the word magnetron) is part of a cavity resonator. Recent findings indicate, that this originate from Telefunken patents DE753483 and DE760436 (both are so-called ‘ap’ files). E351 Korfu

The modality of mixing with the incident frequency depending on the Korfu model. The units E 351 C and E uses uses the fundamental waves of the oscillator (Fig. 9). In the receiver E 351 A and B the second Harmonic. In the receiver model E351 D the third harmonic of the Oscillator

E351 Korfu

In the receiver E351 D the input incident frequency fs, pass through a high pass filter F and then arrives at the mixed M1. The frequency fs is than mixed with the oscillator O1 frequency fo1. The mix between fs and 3fo1, the third harmonic of the ocillator o1, will be the intermediate frequency f1. All the trasmitted frequency f about three times higher than the oscillator fundamental frequency fs1, can be screened out by the input filter F.
For the antenna connection is than necessary to use a waveguide as a high pass filter with the exception of very strong signals.. An high pass filter is enough if the wavelength ratio signal to interference if from about 1: 20 to I: 500 . Different wavelength ratios require a special filter design,
The receiver is not equipped with low pass filter therefore interference reception of smaller wavelengths is possible if function of the respective shortest wave of a receiver calibration curve for example, half or a third for the receiver E 351 E of the tuned Wavelength.
Is possible to diagnose eventual problems on the receiver by monitoring the anode voltage of the receiver oscillator O1 and grid current of all the other tubes.

In the following original WWII video is possible to see the Korfu in operation !



MY E351 Korfu
E351 Korfu

E351 Korfu


E351 Korfu

E351 Korfu

i am looking for pictures, documentation and spare parts for restore this incomplete receiver

Bibliography

  • Alfred Price “Instruments of Darkness” Greeenhill Books
  • Technical Manual “Funk-Horchempfa╠łnger E351” Werkschrift g. 4419, September 1944
  • Arthur Bauer Web Site “Foundation for German Communication and related Technologies “