Craig Birkmaier wrote:
Currently, the DTV system design in the U.S. is very poor in terms
of spectral efficiency.
In practice, bad as it might be, it is identical to European systems. We
have been over this many times. In practice, low-powered TV countries
such as Italy and France do preceisely what we do here, only on a
smaller scale. Their frequency reuse is therefore no better overall.
Yes, the frequencies can be reused more often, but the point is, they
HAVE to be reused more often, in order to obtain continuous coverage.
The use of high powered big sticks means that half or more of the
spectrum in each market cannot be uses to protect adjacent markets.
The use of low powered big sticks means that multiple frequencies need
to be used in translators to cover what in the US might be considered a
single market.
Examples are in Rome, Monte Mario and Monte Cavo repeater sites, and in
Paris, the transmitters of the Eiffel Tower, and the dense Paris SFN,
having to be supplemented by translators less than 30 miles away.
I think the biggest improvement in spectral efficiency in the USA, and
by far the simplest one to implement, would be to allow national
networks to operate as national networks, with regional differences
limited to areas much larger than just one city. Which is as it's done
in Europe. That way, transmitter tower locations can be determined to
optimize continuous coverage, instead of being located to provide
coverage for odd-shaped local "markets."
The idea that SFNs can play a major role in changing this efficiency
picture this is mostly theoretical, as in "bad theory." The SFNs that
are practical, i.e. that don't end up destroying coverage more than they
help, are those with very few big sticks located close together, and/or
the umbrella configuration, which still creates a dense SFN with big
stick. See Berlin and Paris. Look at the coverage, e.g. the mabb report,
and you'll see no practical difference compared with coverage contours
here. Although you will very likely get easier reception close in. As we
could also do, with low-powered OCRs.
And this ties directly into the third point, which is that the
whole notion of networks and channels is losing steam. Program
adjacency is virtually meaningless today.
Has been so for decades. I think program adjacency is only a sort of
"traditional concept" which is quite possibly still used by broadcasters
(I don't know, not being a broadcaster). But from my experience as a TV
customer, it has been obsoleted in practice by remote controls and VCRs,
starting in the late 1970s and early 1980s.
Bert
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