Doug Smith W9WI wrote:
On Sun, 29 Jun 2008 03:24:59 -0400, Rick T wrote:
However, the analog turn-off will vacate most of TV Ch 2-6,
and most of 7-13. This is the truly valuable channel space,
and will be fought over tenaciously. (174-216 MHz)

There will be 40 full-power digital TV stations remaining in channels 2-6
,
not to mention low-power and Class A stations. There has been some talk
of expanding FM radio broadcasting into this band but I don't think it's
very likely.

This band isn't very appealing to other services, because of the large
antennas necessary for effective operation and the prevalence of noise an
d
interference.

Channels 7-13 are solidly TV territory and will not be going to other
services. There will be 452 full-power digital TV stations on these
channels post-transition, and again some number of low-power and Class A
stations. Most TV stations that had the option of running their permanen
t
digital operation in channels 7-13 chose to do so, even if it meant
obsoleting a perfectly good UHF transmitter/antenna. Coverage is better
for a given amount of power than on UHF, and transmitters are more
efficient. (i.e., lower utility bills)

is also a proposal to allow devices to selectively "seek"
out vacant channels in any given locality to use for low
power applications, without interfering with television.
This works OK with digital TV channels which may be
adjacent, but the problem is that analog LPTV and translator
stations are being allowed to stay on the air indefinitely,
which means that adjacent channels with strange digital
signals filling the bandwidth could spill over causing
interference to an analog TV signal.

"...works OK with digital TV channels which may be adjacent..." is under
dispute, with some engineers arguing otherwise. Especially given the
potentially high U/D (undesirable-to-desirable) signal strength ratios.
In an FCC test earlier this year, they also found the devices did a
*really poor* job of detecting which channels were vacant!
(understandable as these devices are likely to have far poorer antennas
than are commonly used on TV sets, especially in the more rural areas
where the TV signals are weaker and larger antennas are more likely to be
in use)

Analog low-power stations do not have a current deadline for digital
conversion. However, the FCC has announced that there *will be* a
deadline. I doubt it will be more than two years into the future. (and
even if it they do get a lot more time, I think many are going to find
themselves forced to convert as fewer viewers are willing to deal with
analog signals)

The odds of the FCC "giving" any of this spectrum to hams, or other
so-called "citizens" uses are slim since the FCC is mandated by Congres
s
to auction off all non-public-safety spectrum recovered from other
services.

Very true.


Hi Doug.....thanks for your comments.

Well, I count about 60 stations licensed for high-power
digital TV operations nationwide on 7-13.....not a huge
number by any means. Here in Arizona, there are very few
remaining after the transition. The public safety folks,
having failed to take any of the 138-174 spectrum from the
military here (Mainly because of the Army base at Ft.
Huachuca) are now looking at the possibility of getting some
of that 174-216. I doubt that it will happen though.

Yes, there is no deadline yet, and the Commission hasn't
indicated if they will eventually set a firm deadline for
LPTV and Translators. There are a huge number of
translators in northwest Arizona.....at a cost of over
$3,000 each to convert the translators times about 50, plus
the LPTV stuff in the Phoenix and Tucson metro areas. I
think the FCC will allow at least 5 years, if not more,
unless they're in the 60's spectrum. However, they're
mostly already chased out of that area.

Because of the reasons you mentioned, I don't support
allowing other services to access the "white space" between
channels....just too many things that can go wrong and mess
up a signal.....particularly a weak rural signal, and
especially an analog translator channel.

I think the best we hams can hope for is some additional HF
spectrum as shortwave broadcasting slowly dies. Sure would
like to see 30M expanded, as well as a full band at 5 MHz,
and an expanded 20 and 17 M bands. Of course, we still need
to clear 7200-7300 worldwide. Good Luck :)


73,
Rick T. - W7RT