to home television (DTH)
Direct to home (DTH) television is a wireless system for delivering television
programs directly to the viewer's house. In DTH television, the broadcast signals
are transmitted from satellites orbiting the Earth to the viewer's house. Each
satellite is located approximately 35,700 km above the Earth in geosynchronous
orbit. These satellites receive the signals from the broadcast stations located
on Earth and rebroadcast them to the Earth.
viewer's dish picks up the signal from the satellite and passes it on to the receiver
located inside the viewer's house. The receiver processes the signal and passes
it on to the television.The DTH provides more than 200 television channels with
excellent quality of reception along with teleshopping, fax and internet facilities.
DTH television is used in millions of homes across United States, Europe and South
East Asia. Direct to home television is a wireless system for delivering television
programming directly to a viewer's house. Usually broadcasting stations use a
powerful antenna to transmit radio waves to the surrounding area. Viewer's can
pickup the signal with a much smaller antenna. The main limitation of broadcast
television is range. The radio signal used to broadcast television shoot out from
the broadcast antenna in a straight line. Inorder to receive these signals, you
have to be in the direct "line of sight" of the antenna. Small obstacles
like trees or small buildings aren't a problem; but a big obstacle, such as Earth,
will reflect these waves. If the Earth were perfectly flat, you could pickup broadcast
television thousands of miles from the source. But because the planet is curved,
it eventually breaks the signal's line of sight. The other problem with broadcast
television is that the signal is often distorted even in the viewing area. To
get a perfectly clear signal like you find on the cable one has to be pretty close
to the broadcast antenna without too many obstacles in the wave.
Television solves both these problems by transmitting broadcast signals from satellites
orbiting the Earth. Since satellites are high in the sky there are a lot more
customers in the line of sight. Satellites television systems transmit and receive
radio signals using specialized antennas called satellite dishes.
satellites are all in geosynchronous orbit approximately 35,700 km above the Earth.
In this way you have to direct the dish at the satellite only once, and from then
on it picks up the signal without adjustment.
More than 200 channels with
excellent audio and video are made available. The dish required is quite small
(30 to 95 cm in diameter).
satellite TV viewers were explorers of sorts. They used their expensive dishes
to discover unique programming that wasn't necessarily intended for mass audiences.
The dish and receiving equipment gave viewers the tools to pick up foreign stations,
live feeds between different broadcast stations, NASA activities and a lot of
other stuff transmitted using satellites. Some satellite owners still seek out
this sort of programming on their own, but today, most Direct to home TV customers
get their programming through a direct broadcast satellite (DBS) provider, such
as DirecTV or the Dish Network. The provider selects programs and broadcasts them
to subscribers as a set package. Basically, the provider's goal is to bring dozens
or even hundreds of channels to your television in a form that approximates the
competition, cable TV.
Unlike earlier programming, the provider's broadcast is
completely digital, which means it has much better picture and sound quality.
Early satellite television was broadcast in C-band radio -- radio in the 3.4-gigahertz
(GHz) to 7-GHz frequency range. Digital broadcast satellite transmits programming
in the Ku frequency range (12 GHz to 14 GHz ).
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