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offset antenna

Offset antennas are parabolic antennas

whose reflector dish has the shape of a paraboloid. The reflector surface of offset antennas is elliptical and symmetrical. The name offset comes from the fact that the focal point of the antenna mirror is not centered, but has a downward offset. In contrast to the feed horn of a prime focus antenna

(PFA), the feed horn with theLNB converter

islocated below the centre of the dish. This means that the radiation pattern is not affected by the radiator or the feedhorn and furthermore the offset antenna can be aligned almost vertically. This in turn has the advantage that in winter no snow can accumulate in the reflector dish, which would lead to a change in the reflection behaviour and to a reduction of the antenna gain

.

Offset antenna, photo and schematic diagram

Offset antenna, photo and schematic diagram

The radio beams hit the reflector dish at an oblique angle and are reflected from there to the LNB converter. The offset angle is normally 21°.

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Englisch: offset antenna
Updated at: 24.09.2011
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