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Transmission band
There are various bands on which televisions operate depending upon the country.
The VHF and UHF signals in bands III to V are generally used. Lower frequencies
do not have enough bandwidth available for television. Although the BBC
initially used Band I VHF at 45 MHz, this frequency is (in the UK) no longer in
use for this purpose. Band II is used for FM radio transmissions. Higher
frequencies behave more like light and do not penetrate buildings or travel
around obstructions well enough to be used in a conventional broadcast TV
system, so they are generally only used for satellite broadcasting, which uses
frequencies around 10 GHz. TV systems in most countries relay the video as an AM
(amplitude-modulation) signal and the sound as a FM (frequency-modulation)
signal. An exception is France, where the sound is AM.
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