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How Dish satellite TV gathers channels and programming

Dish satellite companies use two main sources for programming. You

have the national channels, you know ESPN, MTV, CNN, and the like, which should be familiar to you since they're the very same ones cable uses. Then there is the national affiliates, or local channels, NBC, CBS, ABC, and such.

The national channels all came about as a result of cable. Dish satellite TV just surfaced as an addition venue for national channels to find their way into more homes. For them, jumping on board satellite TV was a no brainer.

Also since national channels use their own geosynchronus satellites to broadcast their programming, it's no problem for dish satellite broadcast centers to use special satellites to pick-up the signal and transmit to their customers.

Local channels are a different animal. National affiliates are broadcast "over-the-air" via antenna, which poses a problem for dish broadcast centers. How to include the local affiliates in programming along with the national channels has plagued satellite TV since the onset.

At first many people would use dish satellite for the national and premium pay channels (HBO, Cinamax, Showtime, etc) and then pick up a very basic cable package to cover their locals. The reason this was acceptable is because the overall bill was still cheaper than comparable cable-only packages.

Things have since gotten better with dish satellite tv

In order to compete with cable on equal footing dish providers needed to add local channels to their programming. The reason for the delay is because the dish satellite provider has to setup a skeleton facility to receive the signal from the local broadcaster. The skeleton facility then transmits to the central broadcast center.

The Dish satellite broadcast center is the "brains" of TV satellite systems

The dish satellite broadcast center takes all the different feeds and converts everything into a high quality digital stream, uncompressed, at about 270 megabits per second for every channel. Well 270 MB is way too much for the satellite to handle so the broadcast station must not merely collect, convert, and redirect the data, it must also compress it to a workable size for the orbiting satellite. Here we will look a little closer at the compression process.

Today's DBS providers compress data using the MPEG-2 compressed video format (same technology used in DVD's). In MPEG-2 form the broadcast center can reduce a 270 MB stream down to  5-10 MB. Without this technology modern dish satellite TV would not exist. With the ability to compress data satellite providers can transmit over 200 channels, without compression, only about 30.

The digital video stream goes through a MPEG-2 encoder which compresses the data, the MPEG-2 encoder also analyzes each frame of the video and decides how to encode it into a format usable by the dish satellite receiver at your home (hence the name encoder).

Encoding cleans up and reduces the size of the data by removing anything irrelevant or unnecessary from the data stream and extrapolating, or estimating, from frame to frame.

There are three ways to extrapolating aspect of encoding is done:

1.) predicated extrapolating - A predicted frame only contains data that has changed since the previous frame.

2.) bi-directional extrapolation - In bi-directional extrapolation the receiver uses surrounding intraframe or predicted frames to interpolate, or insert, the color and position of each pixel.

3.) intraframe extrapolation - Intraframe extrapolating uses the complete data from each frame. With intraframe encoding compression is less.

Compression varies with the type of programming. If the scene doesn't change much from frame to frame then more predicted frames can be used, like a news program.

If the scene varies greatly from frame to frame then more intraframes are created by the encoder, like sports programs.

After all the once data is compressed, the dish satellite broadcast center has to encrypt it to keep people from intercepting the signal and stealing service. The encryption process scrambles the signal and it is decrypted by the receiver.

The broadcast center now beams the compressed, encrypted signal to the orbiting satellite which picks it up, amplifies it, and sends the signal to dish satellite subscribers. Now let's see what needs to happen for you to pick this signal up at your home.

The satellite dish itself is basically a specialized antenna that focuses on a specific broadcast source. Your standard dish satellite consist of the curved dish and the "feed horn" (don't ask me why they call it this). The transmitting satellite sends the signal through the feed horn onto the actual dish which concentrates the signal into a focused beam.

In the receiving process, the roles are reversed and the dish collects the data from the transmitting satellite and focuses it into the feed horn. The dish satellite feed horn also has a low noise blocksdown converter (LNB) which amplifies and filters out "noise", random signals not related to the broadcast. Once done, the LBN sends the amplified, cleaned up signal to the waiting receiver.

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