Description of the radar set, tactical-technical characteristics
Figure 1: „Jagdschloß” Silhouette
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The Jagdschloß radar (FuMG 404) was a German long-range surveillance and battle surveillance radar designed just before the beginning of the Second World War by Siemens & Halske for the German Wehrmacht. Although only a small number of the Jagdschloß, about 80, were produced, it is historically important because it is the first radar to offer a panoramic view at a constant elevation angle or PPI (Plan Position Indicator). In Germany, this type of display is called a “panorama display”.
The secondary antenna of the radar was 8.8 meters wide by 2 meters and consisted of a line of 8 vertical dipoles. It was mounted on top of the primary antenna, which was 24 m wide by 3 m high and consisted of four lines of 16 horizontally-lying dipoles. The latter had two versions using a different frequency range.
The Jagdschloß radar had a blind spot of about 20 km in diameter due to the arrangement of its antennas at the top of an 8 m high tower. For example, an airplane flying at 20,000 feet (6,000 m) altitude at a distance of 60 to 80 km will be invisible because the direct reflection echo from the airplane will interfere with the echo reflected from the ground. This problem is solved, in a first step, by placing a large net of conductive wires (Reflektor-Netz) under the tower.
The radar data were displayed on a 40 cm diameter PPI cathode ray tube and an A-scope for a more accurate distance measurement. Transmission of the radar image via a broadband cable passing through was possible to a remote command post. The azimuth data from the Jagdschloß radar was also transferred as independent information.
The Jagdschloß B synchronized the rotation of the antenna with the pulse repetition frequency. The north position appeared as a point on the screen so that the image could be oriented correctly. A background could be added to the PPI screen, at a scale of 1:700,000, to show the geography surrounding the radar.
The Jagdschloß Michael, manufactured by Telefunken, increased the useful range to between 150 and 300 km thanks to a new 50 m long antenna that replaced the old 24 m antenna. It was so imposing that the structure supporting it had to be redesigned by supporting it with two carriages moving on rails at a certain distance from the central tree.
Another experimental radar, called Jagdschloß Z, operated at 9 cm wavelength, which was very short for this time. The antenna was made from the central parts of the Würzburg radar dishes, stacked vertically to form a single antenna with a real aperture of 72 wavelengths.