Conceptually, satellite TV is a lot like broadcast TV. It's a wireless system for delivering television programming directly to a viewer's house. Both broadcast television and satellite stations transmit programming via a radio signal (see How Radio Works for information about radio broadcasting).
Broadcast stations use a powerful antenna to transmit radio waves to the surrounding area. Viewers can pick up the signal with a much smaller antenna. The main limitation of broadcast TV is range. The radio signals used to broadcast television shoot out from the broadcast antenna in a straight line. In order to receive these signals, you have to be in the direct line of sight of the antenna. Small obstacles like trees or small buildings aren't a problem; but a big obstacle, such as the Earth, will reflect these radio waves.
If the Earth were perfectly flat, you could pick up broadcast TV thousands of miles from the source. But because the planet is curved, it eventually breaks the signal's line of sight. The other problem with broadcast TV is that the signal is often distorted, even in the viewing area. To get a perfectly clear signal like you find on cable, you have to be pretty close to the broadcast antenna without too many obstacles in the way.
The Satellite TV Solution .
Satellite TV solves the problems of range and distortion by transmitting broadcast signals from satellites orbiting the Earth. Since satellites are high in the sky, there are a lot more customers in the line of sight. Satellite TV systems transmit and receive radio signals using specialized antennas called satellite dishes.
Satellites are higher in the sky than TV antennas, so they have a much larger line of sight range.
The TV satellites are all in geosynchronous orbit, meaning that they stay in one place in the sky relative to the Earth. Each satellite is launched into space at about 7,000 mph (11,000 kph), reaching approximately 22,200 miles (35,700 km) above the Earth. At this speed and altitude, the satellite will revolve around the planet once every 24 hours -- the same period of time it takes the Earth to make one full rotation. In other words, the satellite keeps pace with our moving planet exactly. This way, you only have to direct the dish at the satellite once, and from then on it picks up the signal without adjustment, at least when everything works right. (See How Satellites Work for more information on satellite orbits.)
At the core, this is all there is to satellite TV. But as we'll see in the next section, there are several important steps between the original programming source and your TV set.
