Jerry Stuckle wrote:
On 3/18/2014 5:11 AM, Rob wrote:
Jerry Stuckle wrote:
That was the major impetus over here to switch to digital - to free
up major bandspace in the VHF and UHF spectrums.

The 'freeing-up' is because each QAM multiplexed transport stream
carries typically up to 6 TV channels and 6 high-quality stereo radio
channels.


Ah, so the channel is effectively only 1Mhz wide then.

That is only an "average" that you get when you divide the total bandwidth
by the number of TV programmes transmitted.
As multiple TV programmes are transmitted on a single channel,
that occupies the width of a classical analog channel that could
transmit only a single programme, more programmes can be put in
the same bandwidth.

However, to receive one of them you really need to receive the
entire channel (several MHz wide), so all link budget calculations
should be based on the full bandwidth. Later, the receiver throws
away most of the bits it has received and decodes only the information
for one of the TV programmes.


You need to check on how the signals are transmitted. You seem claim to
know a lot about how U.S. TV works, even though you're thousands of
miles away. But then you know a lot more about my job, the people I
work with, and the tools I use than I do.

Come on over and do my job for about ten years. Then maybe, just maybe,
you'll be qualified to comment on it.

Otherwise, I just consider you a troll.

I know that the system used in the USA is different from what it is
here, but this mostly concerns the modulation method used for terrestrial
transmissions. Both methods (8VSB and COFDM) have their merit, and this
was discussed a lot in the past.
The same-frequency network we have in operation here would not be possible
with 8VSB, but in long reach operation 8VSB is claimed to be better.

However, the general principle of using a full classical analog channel
(8 MHz here, 6 MHz for you) in its entirety to transmit a multiplexed
transport stream conveying several TV programmes is the same.

SCPC systems (where a transport rate is chosen to just fit the bitrate
required for a single programme, and the resulting channel bandwith
is correspondingly reduced) is used on some satellites, mainly for
satellite newsgathering and other ad-hoc links, and sometimes for DTH
transmission from really small stations. It is not popular because it
wastes bandwidth and transponder output power headroom.