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to the Earth but possibly as far as 36,000km. Firing its on- board thrusters, the satellite then propels itself into its final circular geostationary orbit at 36,000km. Satellites then orbit the earth because of the force of gravity which tends to pull the satellite toward the Earth. But by moving fast enough, it falls in a curved path and circles the Earth.
It is the same balance of gravity and speed that keeps the moon in orbit. There are many different satellite orbits that can be used. The
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ones that receive the most attention are the geostationary orbit used as they are stationary above a particular point on the Earth. Freesat broadcasts using geo-stationary satellites orbiting around 23,000 miles above using the Astra and Eurobird satellites Situated at 28.2 and 28.8 degrees. The Freesat electronic programme guide is broadcast from
the Eurobird 1 satellite. All the channels broadcasting to date are broadcasting using DVB-S. Standard definition channels are broadcast using MPEG-2, while high definition channels are broadcast using MPEG-4.
Everything you needed to know about satellites
Azimuth Alignment The azimuth is East/West alignment of the dish. The Elevation is the vertical angle of the dish from the horizon. The dish must have a clear, unobstructed view of the satellites and the coordinates vary depending on your location. A satellite dish needs clear line of sight to the satellites. The dish needs to be pointing at a compass heading somewhere between 139 and 147 degrees at an elevation of between 18 and 26 degrees.
Beam
A satellite transmission pattern. It may be wide, narrow or spot. This affects the satellites footprint.
Bandwidth
The band or range of frequencies - often expressed in Hertz (Hz) for analogue devices and bits per second (bps) for digital ones - which can be transmitted through a communication system such as a satellite network. Bandwidth is one measure of a system's information-carrying capacity: the wider the bandwidth, the more information that can be carried.
It means that Freesat doesn’t suffer from capacity
restrictions like DTT, allowing for many more channels and services.
Compression In order to make more efficient use of transmission capacity, digital broadcast signals are reduced in size by digital compression. This has a minimum effect on the received signal quality but allows several compressed TV channels to be transmitted in the space required for one analogue channel.
Coverage area The geographical area covered by a satellite transponder the area within which good quality reception can be guaranteed
commonly known as the "footprint” A satellite may have transponders with different coverage areas and even have steerable "antenna beams" which can be aimed at different areas (this may vary during the life of the satellite). Outside the coverage area the signal declines rapidly and reception is normally not acceptable. Regardless of where your customers live the satellites footprint allows complete coverage of the UK.
GSO
Geostationary Satellite Orbit, the path above the equator is 36,000 km in height, and where a satellite travels at the same angular speed as the rotating earth.
Orbital position
The Position of geostationary satellites measured in degrees east or west from the Greenwich meridian.
Receivers There are currently four different types of freesat receivers. So ensure your customers are aware of all of the options and benefits that each has to offer. freesat SD, freesat HD, freesat+ and integrated TV’s with freesat built in.
Satellite dish The antenna that reflects and concentrates a satellite signal to the focal point of the dish, to be collected and processed by an LNB. The LNB (Low Noise Block) is the small converter mounted at the focal point of a satellite dish. It converts and amplifies high-frequency satellite signals (usually in GHz) into low frequency ones (usually in MHz).
Transponder
A satellite transmitter/ receiver that receives uplinked signals from a satellite earth station changes their form, and then rebroadcasts the altered signal back to earth.
To learn more about freesat or book a training session with our national training team you can contact our dedicated retail support line on 0845 313 0059
August 2010 The Independent Electrical Retailer 23
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