[opendtv] Re: PBS National Datacast
- From: John Willkie <johnwillkie@xxxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 26 Feb 2006 20:57:04 +0000 (GMT+00:00)
Pardon me from trying to stop the bind from leading the sighted, but there =
are three contours for a TV station: city grade (must cover just about all =
[99% plus of the city of license], Grade A and Grade B. =20
The grade B contour for KABC-TV extends into at least seven counties in Sou=
thern California (on a good day, I can get the signal on a bow tie antenna =
in Tijuana). The Grade A covers approximatelyhalf the area of the Grade =
B signal.=20
To quote a 17% percent of the LA county population is a non-sequitur. =20
Were one interested in analyzing the situation fairly, one would run a quic=
k Grade B population study and compare the results with the population figu=
res cited to see if they can cover the entire Grade B coverage area. Also,=
one needs to make adjustments between "covered population" and actual "sig=
nal delivery" since LA has extensive shaded areas, even with he Tx on Mount=
Wilson. It's important to compare apples to apples, and to insure that a =
bushel is a bushel.
I do wonder about Kilroy's statement that Disney has empirical data compari=
ng ATSC to NTSC delivery. I concede they have empirical data on NTSC deliv=
ery, but if they have done real-world ATSC tests (let alone direct comparis=
ons) word hasn't reached me.
And, without knowing the engineering criteria used in the pass/fail analysi=
s on the web site, Bert's conclusions there are even further afield. A rea=
l engineering analysis would incude terrain, distance, elevation tx antenna=
patterns and power, rx antenna gain, pattern and location, and knife-edge =
analysis of intervening terrain. AntennaWeb's idea is mpre apt: red orange =
and green lights. Even then, probability comes into heavy play and teaches=
a few lessons about the difference between predictions and reality. My gu=
ess is that the pass/fail goes to fail if there is any doubt; if only to mi=
nimize Dermot's "truck roll" costs.
Also, I note that there are a heck of lot of fresh movies on a 100 gb had d=
rive.
John Willkie
(a real broadcast engineer; not someone playing as one on on the Internet)
Bert wrote:
Kilroy Hughes wrote:
[Bert] ... although I seriously dount that PBS thinks Dotcast provides bett=
er coverage than ATSC can.
[KH] They don't think that, they know that from a couple years of empirica=
l testing.
Sorry, then let me rephrase: "Even if PBS doesn't know this, Dotcast is wel=
l aware of the fact that their signal won't cover the same area a proper AT=
SC datacast can cover."
Here's direct from the horse's mouth:
http://www.dotcast.com/pdf/dNTSC_tutorial.pdf
"In a nutshell, the dNTSC system inserts data as a quadrature component to =
the TV signal. With Dotcast=E2=80=99s patented data insertion and extractio=
n techniques, the dNTSC system can provide unimpaired analog television vie=
wing while simultaneously delivering errorfree, rich multimedia content to =
a TV station=E2=80=99s Grade A contour=E2=80=94for example, about 1.7 milli=
on people in Los Angeles, CA for an ABC affiliate station."
Isn't that less than 20 percent of the population (9,937,739 in 2004, accor=
ding to http://quickfacts.census.gov/qfd/states/06/06037.html, which makes =
this 1.7M 17 percent).
The way Dotcast works, first you provide your street address (and name, and=
e-mail address) on their web site, *then* they tell you whether you have c=
overage. Well, I suppose under those constraints, you can claim pretty good=
reliability.
By the way, I visited Best Buy yesterday. I spoke to one sales person who i=
nsisted she wanted me to ask questions about their products. So I gave in a=
nd asked where the recording devices for DTT were. She gave me a blank star=
e. I was asking in Chinese, evidently.
Then I spoke with a more "mature" salesperson who seemed completely tuned i=
n to my questions. He said that he had bought a 32" Sony XBR integrated LCD=
TV, and that the ATSC receiver was much better than all the previous ones =
he tried. He also lives south of the DC area, and he said he could receive =
the two stations I can't seem to get *without* having to re-aim his antenna=
, but only on this Sony. One of the two is due West of where we live, and t=
he other is WETA-DT on a low tower and at low power.
The good news being that maybe other brands than just LG seem to have maste=
red 8-VSB. (Or maybe Sony builds in LG receivers.)
I asked him about the dearth of DTT products, like recorders. He thought th=
is had more to do with copy HD protection issues than anything else. He thi=
nks they will soon become available. We'll see.
Bert
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