A satellite TV system is a very technical, highly complex system of equipment including
a satellite uplink station, the satellite out in space orbiting in a geosyncronous
orbit 22,300 miles above the earth’s equator, the small mini-dish receiving unit
located on a house or business and last the receiver (black box) that connects to
your television and allows you to view the satellite programming. Commercial
satellite TV programming has been around since the 1990′s and today it is making
huge gains on the cable TV market as more and more Americans are taking advantage
of better picture and audio quality, lower monthly prices than cable and free
equipment and installation that both major U.S. satellite providers, DISH Network and
DIRECTV provide. But just how does satellite TV work? In this article we’ll take
a detailed look at the various steps involved along the way to producing such a
crystal clear and reliable picture on your television set.
Satellite TV – The Basics
Satellite TV uses a wireless system of transmitting radio signals to deliver its
television programming to the viewer’s home or business. A radio signal can only
travel in a straight line however. Enter the satellite. By placing an
orbiting satellite at 37,000 km (22,300 miles) above the earth and having it match the earth’s rotational speed (7,000 miles per hour) the satellite stays over the same spot above the earth.
This is referred to as being in geosyncronous orbit. These orbits are sometimes
also referred to as Clarke orbits in honor of Arthur C. Clarke who first came up
with the idea in an article he wrote back in 1945 entitled “Extraterrestrial Relays”
published in Wireless World Magazine. The orbiting satellite then retransmits the
radio broadcast signal back down to earth to the receiving satellite dish (mini-dish)
located on your home or business. The signal then travels through coaxial cables
from the dish into the receiver that is connected to your TV, where the signal is
then descrambled into viewable programming for your family to enjoy.
Satellite TV programming that you watch at home begins with a transmitting satellite
dish or antenna located at what is known as an uplink station. The satellite dish
located on your house is only 18″ in diameter and is tiny compared to the huge satellite
dishes used at uplink stations. These satellite dishes can be as large as 9 to 12
meters (30 to 40 feet) in diameter. The great size of these satellite dish transmitters
allows for a much stronger radio signal and for better aiming of the signal at the
orbiting satellite. The uplink dish is pointed toward a specific satellite and the uplinked
signals are transmitted within a specific radio frequency range, so as to be received by
one of the transponders tuned to that frequency range aboard that satellite. The
transponder ‘retransmits’ the signals back to Earth but at a different frequency
band (to avoid interference with the uplink signal), typically in the C-band (4-8 GHz)
or Ku-band (12-18 GHz) or both. The leg of the satellite signal path that transmits
the signal down to the Earth station is known as the ‘downlink’. Satellites can
have up to 32 transponders for Ku-band and up to 24 for C-band only satellites.
Typical transponders each have a bandwidth between 27 MHz and 50 MHz. Geostationary
Kc-band satellites need to be spaced at least 1 degree apart to avoid signal interference.
For C-band satellites the spacing needs to be at least 2 degrees.
Satellite Signal Technology
Original satellite broadcasts are converted into a high-quality, uncompressed digital
stream containing a lot of data, and sends it at a speed of 270 megabits per second (Mbps)
for each channel. All of this data must be compressed however or the satellite
would not be able to receive the information. The system of compression used in the U.S. is the MPEG-2 compressed video format. This is similar to the system used to make DVDs. The provider could now reduce the 270-Mbps stream to about 5 or 10 Mbps, enabling them to transmit about 200 channels, instead of the 30 they could transmit before compression. These signals are scrambled so that only paid subscribers can receive them.
Unlike their predesessors, today’s satellite dishes are small, only 18″ in diameter
and are referred to as a ‘mini-dish’.
A typical satellite dish consists of two parts: the reflector and the feedhorn. The reflector
is the concave dish-shaped part of the antenna. This is the part of the antenna that
captures and focuses the satellite signal onto the feed horn. The feed horn is the part
of the antenna that is mounted on an arm that sticks out from the relector dish. It takes the
signal and feeds it through a cable to your satellite receiver (black box).
Newer satellite dish designs feature multiple feed horns. This is
so the dish can pick up signals from several satellites and clearly focus the captured
signal on one of the several feed horns.
Something called a feed horn has a feature known as a low noise
block down converter (LNB). This provides for clear signal. The LNB does two things:
It amplifies the signal received from the satellite provider, and filters out ‘signal noise,’
radio signals that do not carry the satellite provider’s television programming.
The satellite receiver is simply the black box that is connected to your television
set. It receives the signal from your mini-dish and then de-scrambles the signal into
viewable pictures for your family to watch. The receiver does three main things:
It receives and de-scrambles the signal which contains the programming.
It separates the programming into the individual channels you request by way
of the channel selector button on either your TV or your remote control.
It tracks your Pay Per View usage, and sends your billing information for this
programming to your provider.
Today, there are several different kinds
of receivers: standard receivers, DVR receivers and HD receivers for receiving
high definition (HDTV) television programming. DVR (Digital Video Receiver) players
allow the viewer to actually Pause and Replay live TV and to record up to 70
hours on the DISH Network DVR 311 or 322 players. The DISH Network DVR receiver
is an advanced dual tuner, two TV output satellite receiver and integrated digital
video recorder (DVR). The DISH Network DVR’s were designed so that you never have
to miss another favorite TV show again. No matter what your schedule; with the Dish
Network DVR you can simply record your favorite shows with just the click of a button.
DISH Network offers over 500 programming channels to choose from and all
DISH Network satellite programming comes in 100% all-digital video and audio.
So how does satellite TV work? In a word – perfectly.