[B-R-I] Some DTV Observations
Kaimbridge M. GoldChild
Kaimbridge@gmail.com
Sat Jul 4 14:54:51 EDT 2009
A few musings regarding DTV and THE TRANSITION.
--- Reception: I got an Insignia converter box for my bedroom TV
back in October, and all I use for an antenna is an old Rat Shack
FM dipole:
http://www.radioshack.com/product/index.jsp?productId=2062691
Up here in Beverly, I decode all of the full power Boston stations,
including WMFP:62-18, with WSBK:38-39 and WLVI:56-41 occasionally
to frequently being at border decode (though a tweek of the
"dip"(-ole) usually clears it up), while WHDN-LD-38 (ex-26) shows
up once in a while on the signal meter (though has never decoded);
both WYDN:48-47 and WUTF:66-27 (ex-23) are usually sub-decode
present, as is RI's WNAC:64-12 and WPRI:12-13, all four breaking
through decode with some tropospheric enhancement a few times, as
has WDPX:58-40 and even WLWC:28-22 once or twice (while WUNI:27-29,
WLNE:6-47 and WJAR:10-51 rarely even show on the signal meter, and
WSBE:36-21 has yet to).
From the north, both WMUR:9(-49) and WENH:-11 regularly
register(ed) on the signal meter (though neither yet decoding and
reverted WMUR:-9 seemed less frequent and weaker...though, after
the first few days they seem as strong as they were on ch.49
[maybe even slightly stronger]——increased power?), while
WPXG:21-33 and WNEU:-34 (ex-60) have only registered on the meter
once or twice, well below decode; WCSH:6-44 is the only DT signal
from ME that has even cracked the signal meter a few times. As
for WHDH:-7/-42, DT-42 has been pretty steady while DT-7——though
decodeable——is definitively weaker: But since I am using an FM
dipole (designed for 88-108 MHz) and RF-7 is relatively just a
little above FM (174-180 MHz) while RF-42 is way up in UHF
(638-644 MHz), shouldn't RF-7 come in better than RF-42,
presuming similar ERP contours?
Would there be much improvement with one of those $19.99-39.99
indoor, flat, square/rectangle antennas (either amplified or
non-amplified) you hang on the wall...or does my $6.99 dipole
provide pretty much the same result as the (at least unamplified)
hanging flat antenna?
--- Channel labeling: At least with the Insignia, a way to
associate an undecoded/unmapped virtual channel with its true RF
channel is to manually add the RF channel, with the virtual
channel as the subchannel——e.g., WJAR:10-51 would be added as
"51-10", WUTF:66-27 as "27-66" and WCSH:6-44 as "44-6" (even
though subchannels 1-4 are mapped to WGBX:44-43's, any subchannel
of a mapped virtual channel outside of the decoded/mapped range
of the virtual channel gets assigned to the subchannel of the
actual RF channel). The only downside to this trick——which has
only been tried with the Insignia——is that when it does decode,
the channel position assumes the newly found virtual channel,
thus "44-6" would metamorphosize to "6-1" and the tuner position
would shift to ch.6 with 7/5 being the up/down adjacent channels,
not 45/43, meaning you lose your browsing/"stepping" position
(though pressing the "PREVious CH" button should revert you to
the previous stop, as usual).
--- Ch.55 - "FLO TV": The first time I did an analog scan The
Day After, I definitively noted "digital snow" on ch.55. I then
checked on the Insignia, which showed absolutely NO signal.
Given that and the fact that there was nothing listed for ch.55,
locally, in the FCC data base, I figured that it may have been
some sort of imaging/intermod/harmonic of a DTV signal.
Then, a couple of days later, someone on WTFDA's TV-FM list noted
that Qualcomm (a wireless company) has been buying up spectrum
licenses for ch.55, to create a mobile TV service, "MediaFLO" or
"FLO TV" (so much for just "texting while driving"! P=/ ):
http://en.wikipedia.org/wiki/MediaFLO?printable=yes
which is being locally franchised to Verizon Wireless as "V-Cast".
--- TV set cable tuner: As the analog TV in the den kicked the
bucket a few weeks ago, we got a new, digital LCD set (Vizio
VO32OE HDTV) and plugged it in the day before THE TRANSITION.
The notable thing here is the channel assignment by ComCast.
For the lower channels (2-22), there is not only a secondary SD
channel presence (definitely digital, as it is subject to
pixelation if the connection is loosened), but in most cases also
a terciary one, especially for the HD feeds, where the primary
channel is analog NTSC, while the secondary and terciary are "256 QAM":
http://en.wikipedia.org/wiki/256-QAM?printable=yes
The first twelve stations are listed below, giving both the
channel (with -sub, if known) and lower whole frequency, as well
as the apparent decode/chain (i.e., delay) order ("(#)"):
Primary NTSC Secondary QAM Terciary QAM
Station Ch/MHz Ch/MHz [HD Ch] Ch/MHz
======= ============ ============= ===================
WGBH:2 2/55 (2) 82-1/571 (3) [2-2] 84-1/583 (1)
HSN 3/61 (1) 79-9/553 (2) *******
WBZ:4 4/67 (1) 82-2/571 (3) [4-1] 87-2/601 (2)
WCVB:5 5/77 (1) 82-3/571 (3) [5-1] 86-1/595 (2)
NECN 6/83 (2) 77-6/541 (1) *******
WHDH:7 7/175 (1) 82-4/571 (2) [7-1] 86-2/595 (1)
******* ******* [7-2] 86-3/595
WWDP:46 8/181 (1) 74-74/523 (2) 83-12/577 (3)
WMUR:9 9/187 (1) 74-1/523 (2) [9-1] 75-89/529 (2)
Bev-TV 10/193 (1) 74-2/523 (2) *******
WENH:11 11/199 (1) 74-65/523 (2) 82-6/571 (3)
WLVI:56 12/205 (2) 82-12/571 (3) [56-1] 84-2/583 (1)
WFXT:25 13/211 (1) 82-7/571 (3) [25-1] 87-1/601 (2)
The complete (basic tier) channel layout for ComCast-Beverly can
be found here (one can change the zip code in the URL for their
own particular system):
http://www.silicondust.com/hdhomerun/lineup_web/US:01915#sidebyside
The first thing that strikes me is that the primary NTSC analog
signal is not *necessarily* the first signal in the delay order:
I would think that it should either be first——since there is no
digital decode time——or, if just a retransmission of the secondary
QAM's SD signal, equal with the SD, and the more data packed HD
signal taking the longest. But it seems to vary by station (or
is this discrepancy ComCast's doing?). At least with WHDH:-7,
there appears to be distinct SD and HD feeds (not just a screen
field cropping of the widescreen HD for the SD feed) as the news
crawl at the bottom of the screen during the Today Show are
different!
Even weirder is that the cable analog signal would be ahead of
even the non-cable OTA analog signal (which I suspect was because
they got the signals from the stations "closed circuit" via fiber
optic, rather than from the studio to STA to xmtr—?)!
The other thing is that the HD subchannels are scattered and
intermixed between QAM's subchannels (e.g., [2-2] = 84-1,
[56-1] = 84-2, [4-1] = 87-2, [5-1] = 86-1, [7-1] = 86-2), rather
than some order to clustering (e.g., [2-1] = 84-1, [4-1] = 84-2,
[5-1] = 84-3, ..., [2-2] = 85-1, [7-2] = 85-2, [44-2] = 85-3, ...;
or, as the QAM subchannels can grow beyond "__-50"——e.g., 74-65 or
74-87——assign them all to subchannels of one whole channel——e.g.,
74-__).
In any case, as one can see, if you get a new HDTV, you DON'T need
the cable company's own converter box or special coax line to view
the analog channels OR the OTA HD channels they carry——though the
cable HD stations (e.g., TNT-HD, Lifetime-HD, National Geographic,
etc.) are scrambled, thus requiring their converter box.
Finally, a couple of quickie channel questions for someone with
ComCast's digital box.
TBN/RAI used to coexist on analog ch.98: On the digital tier,
they are listed as TBN-229 and RAI-679, but through the Vizio
tuner, TBN = 113-7/727 and TBN/RAI = 74-6/523. So,
ch.229 = 113-7/727, but is 74-6/523 ch.679 or a secondary QAM
(74-6/523) for primary NTSC (analog) 98/109, or something else?
Also, "Leased Access", 74-3/523, is listed as ComCast ch.283 (in
the above channel layout link, ch.283 is listed as both History,
74-3/523, and Local, 83-12/577, which is actually the secondary
QAM for WWDP:46), but what is the ComCast channel for the "E!
Presents" preview channel (with the diagonal split screen),
85-6/589, and the "Events iN-DEMAND" channel (which is 64 QAM, not
256), 122-3/781?
One other peculiarity is 74-87/523, which has a dead carrier and
is listed in the above channel layout link as ch.3000 (!?!),
"EAS Digital"!
Since EAS interupts ALL cable channels, what is the purpose of
it's own channel...or is that the originating "override" channel,
meaning if someone hacked into the system and put something on
ch.3000 (political rant, poro clip, etc.), it would broadcast on
all of the channels?
~Kaimbridge~
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