Saturday, April 24, 2010

Direct TV

Direct TV is digital quality television that is broadcast by an earth station to a satellite that orbits the earth in a geo-synchronous orbit. The satellite then rebroadcasts the program where it is picked up by the users dish and is sent to their TV set. The Direct TV service started in 1994. It was an immediate hit with consumers and became one of the fastest selling new electronic innovation in history beating out color TVs and CD players.

Direct TV requires that the broadcaster have an earth station that can transmit the TV programs to the satellite. The satellite is in a geo-synchronous orbit above the earth. That means it is 22,000 above the equator and traveling at the same speed as the earth rotates which keeps it in the same location relative to the ground. Being is the same location is imperative to maintaining continuous broadcast capability. The FCC has granted licenses for three orbital locations.

Direct TV uses six satellites to rebroadcast TV programs to its subscribers. One of the satellites is a special type of satellite called a spot beam broadcasting satellite. The spot beam can individually target specific areas of the US to deliver local programming. It uses five antennas and multiple data feeds. The spot beam also require a special physical shape to do it job properly. These satellites were built by Hughes Electronic and LORA Corporation.

Direct TV works with a small 18-inch dish containing an integrated receiver, decoder and remote control that receives the satellite signals and separates the channels, then decompresses, translates and performs the digital to analog conversion needed so that a standard television set can understand the signal.

Direct TV has state of the art earth stations in Castle Rock, Colorado and Los Angeles, California. When all of the local and network programs are received by the earth stations, they are immediately digitized, encrypted, compressed and then up linked (transmitted) to the satellite. The satellite then rebroadcasts the signal to the millions of roof top dishes belonging to its subscribers.

Direct TV uses MPEG2 to encode its video signal. MPEG is a standardized algorithm that encodes and decodes video signals. MPEG2 is the most recent version and only used by those on the cutting edge of the technology. Direct TV has over 255 channels and a variety of packages for subscriber to choose from.

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