Satellite Broadcasting Technology For Tv And Radio
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 geosynchronous 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.
Uplink Station
Satellite TV programming that you watches 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 up linked 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.
Mini-Dish Technology
Unlike their predecessors, 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 feed horn. 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 reflector 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.
Satellite Receiver
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