Satellite television providers have become one of the prevalent sources of service, the system function explained.
The satellite TV system begins with the programming providers themselves - national turnaround channels, and local channels (such as the affiliates of national broadcasters like CBS and NBC). The national turnaround channels (such as MTV and ESPN) send out their content from a satellite dish, which is picked up by a satellite orbiting the Earth, and rebroadcast to the satellite broadcast center. Meanwhile, the local channels send their data to the broadcast center through more traditional fiber-optic cables.
Obviously, the key to the entire system is the use of satellites. Because they orbit the Earth at such a high altitude, sending signals to satellites cuts out the interference that comes along with the traditional method of broadcasting from local channels straight to one's antenna, and greatly expands the coverage area that is possible. The satellites that are used by the satellite TV companies are in what is known as "geosynchronous orbit" with the Earth - which means after they are launched into space, they maintain a speed that allows them to make a complete orbit of the Earth exactly every 24 hours, and as such they are in the same position relative to the Earth at all times, barring any unforeseen problems. Therefore, satellite dishes only have to be aimed at the satellites they use one time, making the whole system possible.
Back at the satellite broadcasting center, once the information from the local channels and the national channels is received, it is converted into a stream of high-quality, uncompressed digital data. However, this is too large to be sent via radio waves and still have a large number of channels, so it is compressed using the same format that is used to compress movies to be stored onto DVDs. This greatly reduces the amount of data that needs to be transferred, and therefore allows for upwards of 200 channels to be broadcast. Before sending out the data, the broadcasting center also makes sure to encrypt or scramble the information so that only the intended recipients are able to make use of it. Those who do not have the correct decryption keys and algorithms are unable to view the programming.
The encrypted, compressed data is then sent to another geosynchronous satellite, which rebroadcasts the information straight to home satellite dishes. These home dish units are usually comprised of a concave bowl and what is known as a "feed horn". The shape of the dish reflects and focuses the beam from the satellite directly into the feed horn, where it is transferred to a receiver inside the house. This receiver is connected to the television set, and has the task of both de-scrambling and decompressing the data so it can be understood by traditional television sets. It also divides the information into the individual channels which make up the television spectrum, and sends the signal for whichever channel is currently selected to the TV. The receivers for most satellite providers also receive a list of what is coming on in the next several hours for each channel, and allows the user to view this information in the form of a programming guide.
The end result of all this is a wide array of television channels broadcast right into the homes of consumers with fairly good picture and sound quality. Not to mention the relative ease of getting it installed, when compared to the early days of satellite TV.
