Why does Analogue TV use so much spectrum?
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I still don't understand how the current analogue system requires so much spectrum for four ; five channels???
Perhaps I can cast some light on this matter. Have a look at this here document, for example:
http://www.satcomsa.co.za/SENTECH Frequency List.pdf
Check out TV in Gauteng. You'll see that there are 6 stations carried in total. Also, for SABC1, 12 transmitters use 11 channels (each of 8 MHz) (Channel 57 is re-used by Mulbarton and Menlo Park, both low power "gap filler" transmitters)
In addition to the large number of channels used to transmit these 6 TV stations, all adjacent channels are unavailable, because analogue technology isn't clever enough to filter out anything less than four channels away. So, at Bez Valley, they can only use channels 24, 28, 56, 60, 64 and 68 - four channels apart within each band. That means that 53, 54, 55; 57, 58, 59; 61, 62, 63; 65, 66, 67; etc., can't be used in the same location.
This is a world of difference compared to DTT.