Discussion:
HD-TV converter box rip-off ....
(too old to reply)
Tim May
2008-02-24 19:35:17 UTC
Permalink
From what I've read, digital is much more tolerant of many forms of
loss and distortion up to a point. Above that point, digital wins.
Below that point you lose everything in one shot. No such thing as a
kinda viewable but mostly snowy picture. All or nothing.
My experience is with two types of HDTV: OTA and via my DirecTV
satellite system. I'll discuss my OTA experience.

I live in the area near the Monterey Bay. I can "see" (literally) the
mountains south of me where I know the main local transmitters are
located. (Fremont Peak) However, it's about 30 miles away. None of the
Bay Area transmitters, even the ones near San Jose, are within a
feasible capture range for me.

Anyone trying to figure out there particular situation with respect to
HDTV should figure out where they are with respect to transmitters,
using a site like www.antennaweb.org, etc.

When local broadcasters first starting "turning on" their HDTV
services, I first tried some old rabbit ears (circa mid-90s, so some
circuitry inside the antenna, not just two extendable elements) to see
what local OTA stations I could get. One station came in to my
HDTV-ready t.v. (a Sharp 27-inch LCD in my bedroom...I didn't try
anything with my 60-inch Sony SXRD LCD until later). The "reception"
was definitely NOT "all or nothing."

Rather, the reception was extremely "blocky," with chunks of the screen
perfectly rendered (as near as I could tell) and chunks that were
missing or scrambled or otherwise obviously not perfectly rendered. As
the antenna was moved around, this amount of blockiness varied.

(I already knew this was not a viable antenna solution, but I wanted to
see what my HDTV-set in my upstairs bedroom would do with the new HD
broadcasts just starting up then.)

Anyone with an existing antenna mast, a familiar Yagi-type array from
the old days, may find that it picks up the HDTV quite well, with no
special Terk-type antenna needed. (However, many of these have fallen
into disrepair, gotten damaged or disconnected. Those going to OTA
after years of cable or satellite may need new rooftop antennas.)

FWIW, friends of mine in a much denser suburban area--the Santa Clara
Valley, California--get dozens of HDTV broadcasts with just plain old
rabbit ears sitting near their sets. A couple of them have added
rooftop antennas to ensure more consistent reception, even during rain.

(My hunch is that a lot of folks will just do this, then will complain
that _some_ of the broadcasts are "bad." The solution will of course
not be that those broadcasters raise their power levels. I expect a
year from now there will be lots of articles in the popular press about
the "problems" people are having and "demands" that the problem be
fixed.)

Back to my situation. I picked a reasonable-sized Terk antenna, for
about $110 at Circuit City. (www.antennaweb.org had recommended sizes
for my area)

This gave better reception (less blockiness) when in my bedroom. Things
got better when I moved it to a room with a better "view" of the
transmitters (fewer internal house materials, a glass window).

Again, not "all or nothing." Rather, _parts_ of each digital frame were
"all" and parts were "nothing." When the error rate was too high,
sometimes the frame just "froze." (This is obviously part of the how my
particular receiver, the t.v. set, was designed to handle very noisy
signals...other designs may do things differently.)

I mounted the Terk on my roof, at the highest point, and directly
facing the mountain I know most of the local transmitters were on (or
on very nearby sites). I'm about 30 miles from these transmitters.

The reception on my 60-inch t.v. and on my upstairs 27-inch t.v. was
excellent, except for occasionally "block noise." This happens during
heavy rainstorms, sometimes at random times.

I get HDTV signals for CBS, Fox, PBS, and NBC. No ABC transmitters in
my area (the Monterey/Santa Cruz/Salinas market). Some of these
transmitters have additional channels associated with them, so I get
the CW and one or two others I haven't bothered remembering.

I also get some HD through my satellite, and will be able to get many
more channels if I call up DirecTV and have them swap out my current
dish for a 5-LNB dish. (I understand they do this for free...I just
haven't bothered to call them.)

What's really interesting is that my digital video recorder (DirecTV,
with a 200 GB disk, good for about 35 hours of HD-quality recording or
about 200 hours of standard-quallity recording) accepts inputs from an
OTA antenna and RECOGNIZES them in the onscreen program guide and can
STORE them just as if they were from the satellite!

So when the Superbowl was broadcast in HD on my Fox station, I was able
to do all the usual pause, back up, freeze, save, etc. things I can
normally do.

This integration of DVRs with OTA broadcasts will make a huge
difference for a lot of people. I expect people to buy DVRs just for
OTA broadcasts, even if they don't have cable or satellite.

In conclusion, HD still has noise problems--always will, for some
users. More so at long ranges and with rain or snow attenuating the
signal. With a proper antenna, these are minor. In urban areas, closer
to the transmitters, probably no noise problems.


--Tim May
Jeff Liebermann
2008-02-25 18:48:04 UTC
Permalink
Post by Tim May
In conclusion, HD still has noise problems--always will, for some
users. More so at long ranges and with rain or snow attenuating the
signal. With a proper antenna, these are minor. In urban areas, closer
to the transmitters, probably no noise problems.
--Tim May
Yep. Even the FCC partially agrees that HDTV broadcasting is going to
be a problem. See report at:
<http://www.fcc.gov/oet/info/documents/reports/TR-05-1017-ATSC-reception-testing.doc>
(Sorry. It's MS Word formatted).
It's a bit of a rough read but it basically says that there were very
few test conditions which resulted in error free reception. 8VSB does
rather badly in the presence of multipath, impulse noise, adjacent
channel rejection, and co-channel rejection. The European system
using COFDM is far more tolerating to frequency selective fading (i.e.
multipath), and slightly better for noise rejection. The FCC had
enough political pressure applied in 2001 to run some field tests:
<http://www.hdtvmagazine.com/archives/mstvtestsum.html>
but concluded (my interpretation) that there are not enough
differences in field test results to justify a change in the standard
from 8VSB to COFDM.

They also mentioned something about your use of an indoor antenna:
"The results of the field testing of 8VSB and COFDM indicate that
although some viewers would be able to enjoy indoor reception
with either system, neither system exhibited the level of
reliability that would be required of a practical broadcast
service based solely on service to indoor antennas."
The problem is NOT the lack of signal signal, but rather reflections
off nearby building, hills, mountains, canyons, towers, etc. Lack of
signal is always a problem, but the pixellation error you observed
were probably caused by multipath. They recommend a 30ft pole and
directional antenna for OTA HDTV.

Most consumer ATSC HDTV 8VSB receivers do not have a detailed signal
quality display. It would be easy to do, but the manufacturers have
not seen fit to do this. Instead, you can use some test equipment to
characterize your location, maximize signal strength, minimize
reflections, and get real numbers:
<http://www.sencore.com/newsletter/Nov03/HDTV_files/HDTV.htm>
The Sencore SLM1453 goes for about $900 list. I'm told that some of
the PC based ATSC tuners will display some real signal quality data,
but I have not seen any or can find any definitive examples. At best,
they seem to offer a cell phone style bar graph with some relationship
to signal quality, which is not very useful. My guess(tm) is that if
you plug in this tester into your antenna, and check out the local
digital TV broadcasters, you'll find that you have adequate signal
strength, but that you're also getting quite a few reflections from
the hills in your area.
--
Jeff Liebermann ***@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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