Satellite television

See also: Satellite television (homonymy), Satellite (astronomy)

The satellite television consists in emitting since a satellite in Geostationary orbit (with 35 850 km, which moves at the same speed as rotation of the ground, therefore which appears “motionless” since the ground) of the programs of radio and of Télévision, Analogique S and Numérique S, paying (Crypté S) or free (in light).

Deposit rate and service road

The natural coverage area (concept of surface and not of rate population connected to the satellite) since a machine of remote transmission, reached nearly 100%, only some abrupt faces of the mountainous solid masses or deep valleys cannot be " éclairées" by a geostationary satellite. These spaces (not having a release compatible with an average rise in 34° in Metropolitan France, corresponding to the driving position with the top of the equator necessary for a Geostationary orbit) famous are populated little even uninhabited. In urban area of the turns can obstruct the reception, but all these cases are marginal compared to the extent of a national territory, < 0.5%, and compared to the importance of its population.

The satellite is famous for its excellent output as regards covered zone (TNT covers 75 to 80% of surface what corresponds toa rate of 85% of the population which can be reached) and is the means of the cheapest diffusion, in particular compared to the TNT and especially the cable television by cable.

Techniques of diffusion

Analogical

Each channel is used to transmit a program of Télévision (more possibly some programs Radiophonique S and services " associés" like the Teletext, the multilingual or multichannel sound (Vo/VF), interactive applications like a " guide programmes" , of the plays, the remote loading of software…).

The signal Vidéo is diffused:

in composite: STAKE (very seldom in Secam) in Europe and several other countries including the Australia and the South Africa and the standard NTSC in North America like in Japan.
in component separate: D2-MAC or C-MAC from now on become obsolete with the profit of the numerical one.

The analogical diffusion by satellite is in rapid sees disappearance since 2000; there remain in particular only the French historical chains diffused by the satellite Atlantic Bird 3 under cover complementary to the terrestrial hertzian diffusion, until the final extinction of the Secam in 2011 and some allemande on Astra 19,2° Is, the Italian public service - SPOKE via Hot-Bird having ceased in April 2005. Lastly, certain international chains like CNN and of the chains intended for the countries of the South (Africa, South America, Southeast Asia…) for economic reasons; analogical receivers being always the least expensive.

Numerical

Each channel or " Repeater " is used to transmit a multiplexing from six to ten programs of Télévision, according to the compression ratio used (and several programs Radiophonique S), according to the standard DVB-S ( Digital Video Broadcasting applied to the satellite diffusion). Audio and video coding is carried out:

in MPEG-2
in MPEG-4 AVC for the video, mainly for the diffusion in High-definition and professional transmissions " Vsat".

The French and European diffusers retained mainly the satellites Hot Bird of Eutelsat and Astra 1 of the ITS to diffuse above Europe their chains in clear mode, i.e. for all, or then into encrypted for the only beneficiaries (subscription).

The French public service retained to him the satellite Atlantic Bird 3 of the operator Eutelsat to cover the zones not served in TNT.

The French-speaking chain CCTV-F is diffused on the satellite PAS-10, bound for Europe and of Africa.

In America, satellites the most used for the free numerical TV (" free-to-air") are:

Galaxie 10R (networks of terrestrial local TV américian) has 123° western
Intelsat America 5 (Globecast, ethnic channels) with 97° western
AMC3 (educational channels PBS) with 87°W
AMC4 (American channels résaux, some ethnic channels) with 101° western

and, for the paying TV:

Nimiq 1,2 (ExpressVu) with western 91° and 82° western
Echostar 6,7,8 (Dish Network) with western 119° and 110° western
DirecTV 1,2,4s with western 101° and 119° western
Anik (StarChoice) with 107° and 111° western

Note that this list can change constantly; find the complete listing of the signals of satellite of the whole world: http://www.lyngsat.com

Equipment of reception

The elements of reception include/understand:

a parabolic Aerial equipped with a universal Head (mono or Bi-satellite);
a coaxial cable;
a Demodulator (in Analogical diffusion ), or a Final DVB-S (in Numerical diffusion );
a cable (Péritel so in France, but with catches RCA so in America) connecting the demodulator to the Television set.

The satellite parabola is installed on the ground, (garden, court etc). the balcony, on the roof or against a wall.

Evolutions of the equipment

In the near future, the parabola will allow a connection " retour" towards the satellite which it collects, on the principle of the average professionals of the " type; Vsat". Thus, the access to the video with request (VOD), video-telephony, the total interactivity and the combination with access Internet will make it possible to meet new needs for the " satellisés". Currently, certain international operators experienced already a compatibility with the ground networks of telecommunication like the Wimax for this " retour" sees;.

Miniaturization of the satellite antenna: as of the end of the year 1990, several industrialists took as a starting point the military technology to put on the market general public, of the parabolas " compactes" , of the antenna in the shape of tube on the principle of MMDS and the ducted antennas punts. Most widespread in France east that which is marketed by the operator Canalsat. The most recent research makes it possible from now on to return " almost completely; invisibles" reception antennas satellite: plates equipped with omnidirectional receivers can be installed on the roofs of the dwellings or in mural walls. Lastly, certain coatings of roofs (tiles) completely " perméables" with the satellite waves make from now on possible the installation of parabolas under a roof. These various devices are specifically adapted to the numerical reception.

See too

Internal bonds

External bonds

bibliographical Source “Which do I Know? ”
“SatMag”.
“Tele Satellite”.

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