Abstract: In a waveguide twist having a torsion element with at least three individual parts situated adjacent to each other and rotatable around an axis of the torsion element, in which each of the individual parts has a central passage hole with a cross-section corresponding to the open cross-section of the waveguides, and in which the passage holes of the individual parts in a non-rotated condition of the torsion element are aligned with each other, a recess is formed in one face of each of the individual parts, the extent of the recess in circumferential direction corresponding to a specified angle of rotation; from the other face of the individual parts a pin extends in an axial direction; and in a mounted position of the torsion element a pin projecting from one individual part engages in the recess located in the face of the adjacent individual part.

Abstract: A polarizer for two different frequency bands is described for exciting an antenna with a parabolic reflector. The polarizer has a waveguide section capable of carrying in each frequency band two mutually perpendicularly linearly polarized waves. For each frequency band, two waveguides having a rectangular cross-section are connected to the waveguide section separate from each other and mutually offset in the axial direction of the waveguide section. A respective waveguide is connected directly to the waveguide section for each polarization direction of the lower frequency band, whereas for the upper frequency band—from a connecting point (11, 12) on—each of the two waveguides is subdivided into two branches (18, 19, 20, 21) with each having identical rectangular cross-section. The respective branches terminate on the waveguide section at mutually opposing locations which are circumferentially offset relative to each other by 90° for the two polarization directions.

Abstract: A polarizer for two different frequency bands for exciting an antenna with a parabolic reflector has a waveguide section capable of carrying in each frequency band two mutually perpendicularly linearly polarized waves. For each frequency band, there are connected to the waveguide section, separate from each other and mutually offset in the axial direction of the waveguide section, two waveguides having a rectangular cross-section. For the lower frequency band, for each polarization direction, a respective waveguide is connected directly to the waveguide section. For the higher frequency band, starting at a connecting point, each of the two waveguides is subdivided into two waveguide branches with identical rectangular cross-sections, with the branches terminating at two opposing locations of the waveguide section. The locations, where the branches for the two different polarization directions terminate on the waveguide section, are circumferentially offset relative to each other by 90.degree..

Abstract: A polarizer for exciting the parabolic reflector of a directional antenna includes a profile section (7) which is formed as a waveguide and is adapted to simultaneously transmit two linearly polarized orthogonal electromagnetic waves. Two rectangular waveguides which separately guide the two electromagnetic waves are connected to the profile section (7). The end face of one of the rectangular waveguides is connected to the side wall of the profile section (7) in a radial direction, whereas the other rectangular waveguide is connected to an end face of the profile section (7). Both rectangular waveguides have an electromagnetic connection to the profile section (7) via openings, wherein a short-circuiting element (10) is disposed in the profile section (7) between the openings.

Abstract: A device is indicated for covering the aperture of an antenna having a parabolic reflector and an exciter. The cover is made of a rigid material. The cover includes a shield ring connected to the reflector and a plastic cover shaped like a flat or obtuse cone having a conical portion which closes the open end of the reflector. The wall of the conical portion of the cover forms an angle between 4.degree. and 6.degree. with a plane that is at a right angle to the axis of the shield ring.