How Does High Definition Satellite Work?

How Does High-Definition Satellite TV Work?

High-definition satellite TV works by sending video and audio signals from geostationary satellites to satellite dishes on Earth.

A satellite orbits with the Earth in a fixed position, flying within the Clarke Belt, which is an area of space about 22,300 miles over the equator.

Earlier satellite signals for television depended on a motorized satellite dish to track the moving satellites across the sky. Today, satellites are launched into a geosynchronous orbit. They are always at the same point above the surface of the Earth, so all satellite dishes can be aimed in the same location.

Sending the Signal to Earth

The broadcast signal comes from an uplink center, which collects television programming from national and local networks and cable TV companies such as HBO. Before the signal is uplinked to the orbiting satellite, it is encrypted with a digital code, so only subscribers can receive the programming.

Several transponders in each satellite deliver signals of different frequencies back to Earth. The frequencies determine the bandwidth used to separate and broadcast different signals, similar to the principle of different frequencies on FM and AM radio.

A satellite dish, typically installed on the side or roof of a building, is positioned to collect the satellite signal at any time of day.

Receiving the Program Signal on Television

The satellite dish gathers the signal and sends it to the feedhorn, the conical device at the center of the dish.

The feedhorn then transmits the signal to a low-noise block (LNB) converter.

The LNB, which works the same as an antenna for airwave signals, is used to amplify the signal and convert it to a frequency for cable transmission.

Satellite television operates with microwave signals that cannot move easily through walls, so the LNB is required to capture the signal and move it over coaxial cable that can be routed inside the building where the television is located. This cable is called the interfacility link (IFL).

The LNB transmits the signal over the IFL cable to a receiver inside the building on which the satellite dish is mounted. The receiver delivers the audio and video signals to a television set.

Satellite TV signals are typically encoded digitally, which allows satellite broadcasting companies to offer more channels using less bandwidth.