HDSDI signals (HD digital video) are limited in most copper cables to about 70m before they become unusable. Any further, and they will need to be reshaped in a small distribution amplifier.
HD signals will travel much longer distances in fibres, so they are now common in TV stations and studios to avoid the problem of signal loss.
At present we cannot easily produce 1080p pictures... although much of the system can handle it, the 3Gb bandwidth is still not really practical for mass distribution.
‘HD Ready’ TV sets will accept HD video signals, but may not have an HD display. If you want to see true HD pictures, you need to buy a 1080p set.
720p HD uses the same 1.5Gb bandwidth as 1080i HD.... and when there is a lot of movement in the picture, it can actually look sharper than it’s higher resolution cousin.
the 1080i TV standard was first used in Japan in the late 1980’s. This was before before digital video, so a single signal was recorded using four old 1” C format reel to reel VTR’s.