Satellite Communication

A communication satellite (sometimes abbreviated to SATCOM) is an artificial satellite stationed in space for the purpose of telecommunications. For fixed (point-to-point) services, communications provide a microwave radio relay technology complementary to that of submarine communications cables. They are also used for mobile applications such as communications to transfer the information to the ships, vehicles, planes, and for TV and radio broadcasting, for which application of other technologies, such as cable.



Telephony

The first and historically most important application for communication satellites was in intercontinental long distance telephony in other word it is also known as telephone. The fixed Public Switched Telephone Network relays telephone calls from land line telephones to an earth station, where they are then transmitted to a geostationary satelitte. Improvements in submarines communications cables, through the use of fiber-optics, caused soem declined in the use of stellites for fixed telephony in the late 20th century. There are also regions of some continents and countries where landline telecommunications are rare to nonexistent, for example large regions of South America, Africa,China, Russia and Australia. Satellite communications also provided connection to the edges of Antartica and Greenland.

Satellite Television

Television became the main market and one of the most important media in our life, its demand for simultaneous delivery of relatively few signals of large bandwidth to many receivers being a more precise match for the capabilities of geosynchonous comsats.Two satelite types are used for North American television and radio: Direct Broadcast satellite (DBS), and Fixed Service Satellite (FSS).




Direct Broadcast Satellite

A direct broadcast satellite is a communication satellite that transmits to small DBS satelliet dishes (usually 18 to 24 inshes or 45 to 60 cm in diameter). Direct broadcast satellites generally operate in the upper portion of the microwave Ku band. DBS is used for DTH-oriented ( Direct-To-Home) satelliet TV services, such as DirectTV and DISHNetwork in the United States, Bell TV and Shaw Direct. FSS satelitte technology was also originally used for DTH satellite TV from the late 1970s to the early 1990s in the United States in the form of TVRO ( Television Receive Only) receivers and dishes. It was also used in its Ku band form for the now- defunct Primestar satellite TV services.