Satellite TV involves both the process of beaming the signals from their sources to the satellites orbiting the earth, and also back down to the individual satellite dishes for decoding and viewing. Different frequency bands are used for these purposes, which can be known as high- and low-band frequencies.
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Low Band
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The low band of satellite TV is known as the C band, with a frequency between 5.9 to 6.4 GHz for uplinks (sending the signal from the broadcasting source to the satellites) and 3.7 to 4.2 Ghz for downlinks (satellites to receiving dishes). C band requires larger satellite dishes for reception, between 3 and 9 feet in diameter, with the most common being 6-foot dishes.
High Band
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The high band is most commonly known as the Ku (Kurtz-under) band, though it can also refer to the Ka (Kurtz-above) band. Ku band frequency is between 14 to 14.5 GHz for uplinks and 11.7 to 12.2 GHz for downlinks. Dishes required to receive this band are much smaller than with C band, as low as 18 inches in diameter.
Usage
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Ku band has become much more widely-used over time compared to C band. NBC was the first to use it to send signals to its affiliates in 1983, according to the Top Bits website, with other networks following suit. The major direct broadcast satellite providers, including DirecTV and Dish Network, employ Ku band as well.
Differences
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The higher-frequency Ku band, which is reserved for satellite communications, avoids interference from other systems such as microwave radio. It produces a more powerful and focused signal, and the equipment involved, especially the smaller dishes, costs much less. C band, however, is much less susceptible to adverse weather conditions than Ku band satellite transmissions
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Read more: Definition of High Band & Low Band Satellite TV | eHow.com http://www.ehow.com/facts_6851492_definition-low-band-satellite-tv.html#ixzz1UWX9gac3
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