Satellite TV

The following section contains excerpts from "How Satellite TV Works" by Karim Nice and Tom Harris.
Full article is available at:   
 http://entertainment.howstuffworks.com/satellite-tv.htm

Introduction
When satellite television first hit the market, home dishes were expensive metal units that took up a huge
chunk of yard space. In these early years, only the most die-hard TV fans would go through all the hassle
and expense of putting in their own dish. Satellite TV was a lot more difficult than broadcast and cable TV.

Today, you see compact satellite dishes perched on rooftops all over the United States. Drive through rural
areas beyond the reach of the cable companies and you'll find dishes on just about every house. The
major satellite television companies are bringing in more customers every day with the lure of movies,
sporting events and news from around the world.

What is Satellite TV?
Conceptually, satellite television is a lot like broadcast television. It's a wireless system for delivering
television programming directly to a viewer's house. Both broadcast television and satellite stations
transmit programming via a radio signal.

Broadcast stations use a powerful antenna to transmit radio waves to the surrounding area. Viewers can
pick up the signal with a much smaller antenna. The main limitation of broadcast television is range. The
radio signals used to broadcast television shoot out from the broadcast antenna in a straight line. In order
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 the Earth, will reflect these radio
waves.

Most satellite 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 .

There are five major components involved in a
direct to home (DTH) satellite system: the programming
source, the broadcast center, the satellite, the satellite dish and the receiver.

Programming sources are simply the channels that provide programming for broadcast. The provider
doesn't create original programming itself; it pays other companies (HBO, for example, or ESPN) for the
right to broadcast their content via satellite. In this way, the provider is kind of like a broker between you and
the actual programming sources. (Cable television companies work on the same principle.)

The broadcast center is the central hub of the system. At the broadcast center, the television provider
receives signals from various programming sources and beams a broadcast signal to satellites in
geostationary orbit.

The
satellites receive the signals from the broadcast station and rebroadcast them to the ground.

The viewer's
dish picks up the signal from the satellite (or multiple satellites in the same part of the sky)
and passes it on to the receiver in the viewer's house.

The
receiver processes the signal and passes it on to a standard television.

The Programming
Satellite TV providers get programming from two major sources: national turnaround channels (such as
HBO, ESPN and CNN) and various
local channels (the NBC, CBS, ABC, PBS and Fox affiliates in a
particular area). Most of the turnaround channels also provide programming for cable television, and the
local channels typically broadcast their programming over the airwaves.

Turnaround channels usually have a distribution center that beams their programming to a geostationary
satellite. The broadcast center uses large satellite dishes to pick up these analog and digital signals from
several sources.

Most local stations don't transmit their programming to satellites, so the provider has to get it another way.
If the provider includes local programming in a particular area, it will have a small local facility consisting of
a few racks of communications equipment. The equipment receives local signals directly from the
broadcaster through fiber-optic cable or an antenna and then transmits them to the central broadcast
center.

The broadcast center converts all of this programming into a high-quality, uncompressed digital stream. At
this point, the stream contains a vast quantity of data -- about 270 megabits per second (Mbps) for each
channel. In order to transmit the signal from there, the broadcast center has to compress it. Otherwise, it
would be too big for the satellite to handle. In the next section, we'll find out how the signal is compressed.

The two major providers in the United States use the MPEG-2 compressed video format -- the same format
used to store movies on DVDs. With MPEG-2 compression, the provider can reduce the 270-Mbps stream
to about 5 or 10 Mbps (depending on the type of programming). This is the crucial step that has made DBS
service a success. With digital compression, a typical satellite can transmit about 200 channels. Without
digital compression, it can transmit about 30 channels.

The Dish
A satellite dish is just a special kind of antenna designed to focus on a specific broadcast source. The
standard dish consists of a parabolic (bowl-shaped) surface and a central feed horn. To transmit a signal,
a controller sends it through the horn, and the dish focuses the signal into a relatively narrow beam.

The dish on the receiving end can't transmit information; it can only receive it. The receiving dish works in
the exact opposite way of the transmitter. When a beam hits the curved dish, the parabola shape reflects
the radio signal inward onto a particular point, just like a concave mirror focuses light onto a particular point.

The Receiver
The end component in the entire satellite TV system is the receiver. The receiver has four essential jobs:

It de-scrambles the encrypted signal. In order to unlock the signal, the receiver needs the proper decoder
chip for that programming package. The provider can communicate with the chip, via the satellite signal, to
make necessary adjustments to its decoding programs. The provider may occasionally send signals that
disrupt illegal de-scramblers, as an electronic counter measure (ECM) against illegal users.

It takes the digital MPEG-2 signal and converts it into an analog format that a standard television can
recognize. In the United States, receivers convert the digital signal to the analog NTSC format. Some dish
and receiver setups can also output an HDTV signal.

It extracts the individual channels from the larger satellite signal. When you change the channel on the
receiver, it sends just the signal for that channel to your TV. Since the receiver spits out only one channel at
a time, you can't tape one program and watch another. You also can't watch two different programs on two
TVs hooked up to the same receiver. In order to do these things, which are standard on conventional cable,
you need to buy an additional receiver.

It keeps track of pay-per-view programs and periodically phones a computer at the provider's headquarters
to communicate billing information.

Receivers have a number of other features as well. They pick up a programming schedule signal from the
provider and present this information in an onscreen programming guide. Many receivers have parental
lock-out options, and some have built-in digital video recorders (DVRs), which let you pause live television
or record it on a hard drive.

While digital broadcast satellite service is still lacking some of the basic features of conventional cable (the
ability to easily split signals between different TVs and VCRs, for example), its high-quality picture, varied
programming selection and extended service areas make it a good alternative for some. With the rise of
digital cable, which also has improved picture quality and extended channel selection, the TV war is really
heating up. Just about anything could happen in the next 10 years as all of these television providers battle
it out.
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Satellite Video Source

The most important element of the full Home Theater experience, is the video signal source. It must be a
digital signal. DVDs are both digital and HDTV. Satellite dish services are digital and some programming is
HDTV. If your local TV cable service does not provide digital video services, or you have no access to a TV
cable, there is no choice but  to subscribe to a satellite dish service. There are only two major services
available: Dish Networks / Echostar Communications and Direct TV.
Now you can get your movies below.
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