In article ,
Jerry Stuckle wrote:

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.

Jerry, I'm intrigued by what you say here.

I just skimmed through the first few parts of the ATSC standard
document (ATSC A/53 parts 1-3). What I see there, indicates that
there's a single MPEG-2 transport stream, carrying several interleaved
elementary streams (audio and video). This transport stream is
trellis-encoded, and then used to modulate a single RF carrier
(VSB), with a 6 MHz channel width.

With that modulation, it seems to me that receiving the OTA
transmission does require demodulating the entire 6 MHz signal
bandwidth to recover the transport stream. The individual program
streams may of course use much less than the full effective bandwidth,
after de-interleaving, but I can't see how it would be practical to
demodulate and decode the VSB signal and "pull out" one individual
elementary stream using only a smaller "slice" of the RF signal.

What am I missing here? Is it actually possible to "receive-slice"
the 8VSB signal with a narrower RF passband, and pull out a specific
elementary stream successfully? Are some broadcasters actually
transmitting multiple modulated carriers within their 6 MHz ATSC
spectrum slice?

Now, I realize that cable TV transmissions may not (and often do not)
use VSB. With an OFDM modulation it would be possible in principle to
"slice" the 6 MHz spectrum segment into smaller, independent sets of
subcarriers carrying different programs... I don't know if any cable
systems do this in practice but it does seem possible.