COMMUNICATIONS LINK
Antennas on the ground and on satellites send and receive radio waves that carry telephone calls, television signals, or data. A telephone call from the Europe to the USA, for example, might pass through the public telephone network to a nearby Earth station, which transmits the radio waves to a satellite in GEO. The satellite would then amplify and retransmit the radio waves to an antenna in the USA, where the signal is routed over the telephone network to its destination.
TRANSPONDERS
Devices called the transponders are at the heart of communications satellites. They contain a chain of electronic components. These components clean up radio signals, which can be distorted after traveling through the atmosphere, and convert them to the frequency necessary for transmission back to earth. They also amplify the signals before retransmitting them.
EARTH STATIONS
The antennas and other equipments needed on the ground to transmit and receive signals to and from satellites are known as the Earth station. Earth stations can be housed in large buildings. Their antennas act as gateway through which, for example, thousands of telephone calls are transmitted to and from the satellite. Earth stations can also be small units, designed to fit on ships or planes.
SATELLITE FOOT PRINT
Just as the beams of spotlights have different shapes and sizes, so radio waves transmitted by a satellite fall on Earth with a particular pattern. This pattern is known as satellite foot print. Antennas within the foot print can transmit and receive signals to and from the satellite.
GEOSTATIONARY SATELLITES
Satellites in GEO above the Equator always seem to stay over the same spot on Earth. They appear stationary because a satellite 36,000 km above Earth takes the same time to complete one orbit as Earth takes to spin on its axis. They remain in sight of the same Earth station.
FREQUENCY
Radio waves are part of the electromagnetic spectrum. Communications satellites transmit radio waves at frequencies that passes through the atmosphere without being absorbed by water vapour.
Antennas on the ground and on satellites send and receive radio waves that carry telephone calls, television signals, or data. A telephone call from the Europe to the USA, for example, might pass through the public telephone network to a nearby Earth station, which transmits the radio waves to a satellite in GEO. The satellite would then amplify and retransmit the radio waves to an antenna in the USA, where the signal is routed over the telephone network to its destination.
TRANSPONDERS
Devices called the transponders are at the heart of communications satellites. They contain a chain of electronic components. These components clean up radio signals, which can be distorted after traveling through the atmosphere, and convert them to the frequency necessary for transmission back to earth. They also amplify the signals before retransmitting them.
EARTH STATIONS
The antennas and other equipments needed on the ground to transmit and receive signals to and from satellites are known as the Earth station. Earth stations can be housed in large buildings. Their antennas act as gateway through which, for example, thousands of telephone calls are transmitted to and from the satellite. Earth stations can also be small units, designed to fit on ships or planes.
SATELLITE FOOT PRINT
Just as the beams of spotlights have different shapes and sizes, so radio waves transmitted by a satellite fall on Earth with a particular pattern. This pattern is known as satellite foot print. Antennas within the foot print can transmit and receive signals to and from the satellite.
GEOSTATIONARY SATELLITES
Satellites in GEO above the Equator always seem to stay over the same spot on Earth. They appear stationary because a satellite 36,000 km above Earth takes the same time to complete one orbit as Earth takes to spin on its axis. They remain in sight of the same Earth station.
FREQUENCY
Radio waves are part of the electromagnetic spectrum. Communications satellites transmit radio waves at frequencies that passes through the atmosphere without being absorbed by water vapour.
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