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Fixed-satellite service〔ITU, RR, article 1.21〕 (short: FSS) is – in line to ITU Radio Regulations – a radio-communication service between earth stations at given positions, when one or more satellites are used; the given position may be a specified fixed point or any fixed point within specified areas; in some cases this service includes satellite-to-satellite links, which may also be operated in the inter-satellite service; the fixed-satellite service may also include feeder links for other space radiocommunication services. The ITU Radio Regulations define this radiocommunication service as follows: *Fixed service: * *Fixed-satellite service FSS – is as well the official classification (used chiefly in North America) for geostationary communications satellites that provide broadcast feeds to television stations, radio stations and broadcast networks. FSSs also transmit information for telephony, telecommunications, and data communications. FSSs have been used for Direct-To-Home (DTH) satellite television channels in North America since the late 1970s. This role has been largely supplanted by direct broadcast satellite (DBS) television systems, which began in 1994 with the launch of Primstar, the first DBS television system. FSSs in North America are used to relay channels of cable TV networks from their originating studios to local cable headends and to the operations centers of DBS services (such as DirecTV and Dish Network), to be re-broadcast over their DBS systems. ==In North America== FSSs were the first geosynchronous communications satellites (such as Intelsat 1 (Early Bird), Syncom 3, Anik 1, Westar 1, Satcom 1 and Ekran); new satellites continue to be launched to this day. FSSs operate in either the C band (from 3.7 to 4.2 GHz) or the FSS Ku bands (from 11.45 to 11.7 and 12.5 to 12.75 GHz in Europe, and 11.7 to 12.2 GHz in North America). The higher-frequency bands tend to have more spectrum and orbital slots available, but more expensive technology and higher rain margin. FSSs operate at lower power than DBSs, requiring a much larger receiving dish than a DBS system, usually for Ku band, and or larger for C band, compared to for DBS dishes. Unlike DBSs, which use circular polarization on their transponders, FSS transponders use linear polarization. Systems that receive television channels and other feeds from FSSs are usually referred to as TVRO (Television Receive Only) systems, or pejoratively "big ugly dish" (BUD) systems (due to the much larger dish size compared to systems for DBS reception). The Canadian Shaw Direct satellite TV service relies on FSS technology in the Ku band. Primestar in the USA used Ku transponders on an FSS for its delivery to subscribing households until Primestar was acquired by DirecTV in 1999. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fixed-satellite service」の詳細全文を読む スポンサード リンク
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