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Here we will attempt
to give you an overview of how a satellite dish works
and what you can expect if you decide to get one for
your home.
How a Satellite Dish
Works
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.
If the Earth were perfectly flat, you
could pick up broadcast television thousands of miles
from the source. But because the planet is curved, it
eventually breaks the signal's line of site. 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 cable, you
have to be pretty close to the broadcast antenna without
too many obstacles in the way.
Satellite television solves the problems
of range and distortion 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 site. Satellite television systems transmit
and receive radio signals using specialized antennas
called satellite dishes.
The television satellites are all in geosynchronous
orbit, meaning that they stay in one place in the sky
relative to the Earth. Each satellite is launched into
space at about 7,000 mph (11,000 kph), reaching approximately
22,200 miles (35,700 km) above the Earth. At this speed
and altitude, the satellite will revolve around the
planet once every 24 hours -- the same period of time
it takes the Earth to make one full rotation. In other
words, the satellite keeps pace with our moving planet
exactly. This way, you only have to direct the dish
at the satellite once, and from then on it picks up
the signal without adjustment, at least when everything
works right. (See How Satellites Work for more information
on satellite orbits.)
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. On the next page, we'll look
at each component in more detail.
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.
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.
At the broadcast center, the high-quality
digital stream of video goes through an MPEG-2 encoder,
which converts the programming to MPEG-2 video of the
correct size and format for the satellite receiver in
your house.
Once the signal is compressed and encrypted,
the broadcast center beams it directly to one of its
satellites. The satellite picks up the signal with an
onboard dish, amplifies the signal and uses a another
dish to beam the signal back to Earth, where viewers
can pick it up.
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.
In some systems, the dish needs to pick
up signals from two or more satellites at the same time.
The satellites may be close enough together that a regular
dish with a single horn can pick up signals from both.
This compromises quality somewhat, because the dish
isn't aimed directly at one or more of the satellites.
A new dish design uses two or more horns to pick up
different satellite signals. As the beams from different
satellites hit the curved dish, they reflect at different
angles so that one beam hits one of the horns and another
beam hits a different horn.
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.
The Satellite-Dish-Systems.info
website offers you the following articles of information
about satellite tv and dish systems. These articles
have been written for informational and entertainment
purposes only.
1) General
Satellite Tv Dish Information - Includes general
information about the dish and satellite systems as
a whole. This article focuses on the basics.
2) Satellite
Dish Installation - Everything that you wanted to
know about satellite dish installation but were afraid
to ask. The best bit of information here is that you
can get satellite dish installation for free from Dish
Network and Directv®.
3) Dish
Repair for Satellite Systems - Information about
dish repair. Of course, if you opt for a satellite system
from Directv® or Dish Network, you won't ever have
to worry about satellite dish repair.
4) Satellite
Dish Pointing - There are certain devices and techniques
when it comes to dish pointing. This article contains
some basic information on this subject.
5) Digital
Satellite Systems - It is a digital world that we
live in. How does digital techknowledgy fit in with
a satellite dish?
6) Internet
Satellite Dish - Yes, it is now possible to get
broadband internet through a satellite dish. Here's
the scoop.
7) Satellite
Dish Receivers - There are many choices when it
comes to satellite dish receivers. In this article you
will find an overview of the choices that are available
to you.
8) Satellite
Systems - From big dish systems to mini dish systems,
you have a few choices when it comes to the type of
satellite system that you get.
9) Satellite
Dish Covers - This article is fairly straight-forward.
It's about satellite dish covers.
10) Satellite
Dish Antenna - What do you mean by 'satellite dish
antenna'? An antenna is a separate issue. Anyway, here
is what you need to know about satellite antennas.
11) Dish
Network Satellite TV Systems - The number one choice
for satellite tv in the United States, Dish Network
has much to offer to it's subscribers. Looking for low
base price packages? Look right here.
12) Direct
TV Satellite Systems - Direct TV is well known for
their sports programming packages.
13) Free
Satellite TV Systems - What is the scoop on these
free satellite tv systems that we are always hearing
about?
14) Satellite
Dish Equipment - Well, let's see, there's a dish,
a receiver, a remote control... what else could you
need?
15) Music
Channels for Satellite Dish Systems - This article
gives some information about the all-digital music channels
that you can get when you sign up for Dish Network or
Direct TV.
16) Sports
Programming for Satellite Systems - One of the best
things about getting a satellite dish is the incredible
amount of sports programming that you can get.
17) Satellite
Dish Channels - Here you will find an overview of
the types of channels and programming that you can get
when you sign up to get a free satellite dish system
from one of the top providers.
18) Local
Channels for Dish Systems - This article kind of
brings us back to the 'satellite dish antenna' issue.
Do you need an extra antenna in order to get your local
television stations?
19) HDTV
Satellite Systems - High definition is one of those
things that you can probably live without... unless
you've already experienced it.
20) DVR
for Satellite Dish Systems - Digital video recording
allows you to skip through the commercials. You can
record one show while watching another. You can pause
live tv and perform some other nifty tricks.
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