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Polar mount
A polar mount is a movable mount for satellite dishes that allows the dish to be pointed at many geostationary satellites by slewing around one axis.〔(Explanation of satellite antenna polar mount )〕 It works by having its slewing axis parallel, or almost parallel, to the Earth's polar axis so that the attached dish can follow, approximately, the geostationary orbit, which lies in the plane of the Earth's equator.
==Description==
Polar mounts are popular with home television receive-only (TVRO) satellite systems where they can be used to access the TV signals from many different geostationary satellites.〔Angels in the sky: the satellite revolution in India, Rajni Kant Tewari, Kusumakar Sukul - page 132〕 They are also used in other types of installations such as TV, cable, and telecommunication Earth stations although those applications usually use more sophisticated altazimuth or fix angle dedicated mounts.〔The Ku-band satellite handbook, Mark Long, page 101〕 Polar mounts can use a simplified one axis design because geostationary satellite are fixed in the sky relative to the observing dish and their equatorial orbits puts them all in a common line that can be accessed by swinging the satellite dish along a single arc approximately 90 degrees from the mount's polar axis. This also allows them to use a single positioner to move the antenna in the form of a "jackscrew" or horizon-to-horizon gear drive. Polar mounts work in a similar way to astronomical equatorial mounts in that they point at objects at fixed hour angles that follow the astronomical right ascension axis. Like equatorial mounts, polar mounts require polar alignment. They differ from equatorial mounts in that the objects (satellites) they point at are fixed in position and usually require no tracking, just accurate fixed aiming.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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