I'm impressed on the amount of channels of a television satellite. In Europe, for example, Hotbird 13 supply 1000+ television channel, Astra 19.2 and Astra 28 others 2000 or 3000 channels, some in HD.

How is possible ? Why Satellite has so much bandwidth compared to a dvb-t transmission antenna ?

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Not sure if this one goes in network engineering, but I'll take a shot. I was Navy comms for 7 years.

SATCOM, along with utilizing different spectrums for different purposes (UHF, SHF, EHF) also have different transmission and band usage.

For the most direct answer, SATCOM uses either TDMA (Time Division Multiple Access) or FDMA (Frequency Division Multiple Access). This allows individual "channels" that you would receive at a cable box to fit into their own particular piece of the SATCOM link pie.

TDMA allows for more versatility because more individual channels can be added within the aggregate and are timed in their transmission unlike FDMA where each has their own dedicated piece of the aggregate link.

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