|reply to bernardc |
Re: Good info
An administrative decision in 1948 set the low end of the TV spectrum at 54 MHz. When 2-way cable systems were developed, that left only the frequencies below 54 MHz for the upstream and a guard band.
On the downstream side, the bandwidth is allocated between cable TV channels and Internet
On the upstream side the frequencies are allocated to cable modem upstreams (set-top box control data, FM radio, and cable telephone don't take up much bandwidth).
So the limitation is the amount of bandwidth available. The amount allocated for both up and downstream is decided by the cable companies.
Since the cable plant is strictly an analog system, changing the frequency break becomes very difficult.