Communication: How Satellite Tv Works

Satellite television providers use satellites on the ground and in orbit to direct the signal to their viewers.

Satellite television, however, is essentially wireless--meaning those in remote areas that otherwise wouldn't be able to receive programming, can. Satellite television is similar to cable television only in that it provides similar programming. The actual method of transmission is relatively simple, involving multiple components that interact with one another to transfer the signal from its initial source to the viewer.

First, the satellite provider must first have a signal to broadcast. As such, they need to have sources for the actual programming they are providing. Networks and channels send their programming to the satellite broadcasting center for a fee.

The satellite provider then charges a fee to send the signal out to its customers. The provider broadcasts to a satellite or satellites that are in orbit. And then once this satellite has received the signal, it rebroadcasts it back to Earth.

At the receiving end, a dish then receives the signal broadcast from the satellite in orbit, and is then converted by a receiver so that the signal is viewable on a television.

So how does this actually work?

The programming signal is first sent from the actual station/network to the broadcast center. Larger networks often use smaller satellites to broadcast their signals, while smaller local networks may use antenna and fiber optics to send their programming. Once at the broadcast center, all of the channels from the different sources are converted into a high quality digital signal.

Once the signals are all converted, they must next be encoded to compress them. If left uncompressed, the data stream would be overly large and difficult for the satellite to handle. By encoding the signal, the size of the stream is greatly reduced. And by reducing the size of the stream, the provider can broadcast more channels with a single satellite. The compression that is used for encoding is similar to the compression used for DVD movies. Despite the much smaller data size, the picture produced is generally quite clear, although sometimes artifacts (where to the viewer the picture looks blocky and jumbled for a moment) occur.

Next, once the data is compressed, the broadcast signal is first encrypted and then finally sent from the broadcasting center to a satellite in orbit. This satellite is special in that it is in what is called geosynchronous orbit. Objects in this orbit are traveling with the Earth as it spins. So, assuming the object could be seen, someone or something on the Earth's surface would see the object as stationary.

By having a satellite in geosynchronous orbit, the satellites broadcasting and receiving signals to and from the satellite do not have to change the direction they are pointing in. That means the two satellites on Earth can always point at the satellite. It also means they only need to be pointed at the satellite once. Once it's set up, there should be few problems.

This orbiting satellite amplifies the signal and sends it back down toward Earth, where the viewer's satellite receives the signal.

The broadcast signal then travels from this dish to a receiver. The receiver decrypts the stream and also converts the digital signal into analog, so it will be recognized by the television.

The receiver determines what channels this receiver can process for viewing. The satellite provider can interact with the receiver to change this if, say, the viewer wishes to add some channels. When watching a channel, the other channels in the stream are filtered out. This means that only one channel can be watched at a time. Some receivers have other features such as digital video recorders on them.

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