earth station


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earth station

[′ərth ‚stā·shən]
(communications)
A facility with a land-based antenna used to transmit and receive information to and from a communications satellite.

earth station

A ground-based receiving or transmitting/receiving station in a satellite communications system. The counterpart to the earth station is the satellite in orbit, which is the "space station." Earth stations use dish-shaped antennas, the diameters of which can be under two feet for satellite TV to as large as fifty feet for satellite operators. Antennas for space exploration have diameters reaching a hundred feet.

Multiplex, Modulate and Upconvert
An earth station is generally made up of a multiplexor, a modem, up and downconverters, a high power amplifier (HPA) and a low noise amplifier (LNA). Almost all transmission to satellites is digital, and the digital data streams are combined in a multiplexor and fed to a modem that modulates a carrier frequency in the 50 to 180 MHz range. An upconverter bumps the carrier into the gigahertz range, which goes to the HPA and dish.

Downconvert, Demodulate and Demultiplex
For receiving, the LNA boosts the signals to the downconverter, which lowers the frequency and sends it to the modem. The modem demodulates the carrier, and the digital output goes to the demultiplexing device and then to its destinations. See earth station on board vessel and base station.


Earth Station
Earth stations use dish-shaped antennas to transmit and receive microwave signals to and from satellites.







On Board a Ship
Earth stations on board vessels (ESVs) are used to receive TV, make phone calls and access the Internet while traveling near the coast or on the high seas. Encased in a waterproof container, the ESV must be able to track the satellite with great precision. If the ESV deviates by a half a degree, it must shut down transmission immediately in order to not interfere with other satellites. (Image courtesy of Sea Tel Inc., www.seatel.com)
References in periodicals archive ?
We are proud to be selected by Hellas Sat to provide a turnkey solution for its new earth station.
Earth station equipment is priced from $15,000 and up.
Earth stations mounted on aircraft or ships will need to be licensed by Ofcom, as these vehicles are capable of crossing into other countries jurisdictions.
The company that intends to use the earth station can specify a site location to an engineering consultant and see if that site "clears" during a preliminary computer analysis (discussed below).
In choosing a location for a satellite earth station it needs to be cost-effective and have reliable connectivity to the rest of the world.
In 1967 the US international service carriers established the Earth Station Ownership Committee (ESOC) through an agreement that set up separate ownership consortiums for the contiguous US, Hawaii and Guam, and fixed the percentage ownership shares for Comsat, AT&T, Hawaiian Telephone, ITT, RCA and WUI.
The critical areas and design considerations involved in the installation of a transmit/receive earth station must be determined and solutions identified prior to the actual installation.