[opendtv] Re: STATEWIDE DTV TEST

  • From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Sat, 20 Dec 2008 16:38:42 -0800

I've read all of your posts on the coverage issue with great interest and
almost always agree with your analysis. However, I don't recall you
mentioning the -6db equivalency issue, though I might have missed it. I do
know that I wasn't telling you anything you don't already know but many
others on the forum might not understand the power equivalency issue,
therefore I believe referenced in any numerical signal analysis.

Keep it up!

Dale


> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Albert Manfredi
> Sent: Saturday, December 20, 2008 3:05 PM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: STATEWIDE DTV TEST
>
>
>
> Dale Kelly wrote:
>
> >> I'd worry too. Especially because WPVI analog,
> >> on Ch 6, is transmitting an ERP of 74.1 KW, whereas
> >> in digital, they are scheduled for 7.56 KW, on the
> >> same tower. That's a 9.9 dB reduction in power.
> >
> > Equivalent power for analog to DTV is not 1:1. The
> > analog picture power level is about 6db lower than
> > it's peak power level, where the extra 6db is used
> > to transmit the synchronizing pulses. Since those
> > sync pulses are not part of the DTV signal, an
> > equivalent DTV power level for your example would
> > be about 18.5KW. In this case the channel 6 DTV power
> > is still down 3 to 4 db below equivalency, which is
> > certainly problematic
>
> That was my point. A 6 dB reduction in power, digital compared
> with analog, should result in similar reception range. A 10 dB
> reduction in power, when the analog is already barely receivable,
> is asking for trouble.
>
> I already posted on here that in the Balt and Wash markets, the
> VHF DTV stations will be operating between 12 and 18 dB BELOW
> where their analog levels are now.
>
> This is all part of the same reality I've been trying to point
> out for some time. In spite of the "common wisdom" that VHF is
> easier to receive, it looks like some of these ATSC VHF stations
> are trying to make it be exactly the opposite.
>
> By the way, it's also instructive to know just how difficult it
> is for Cliff to receive analog VHF at his location. In any other
> OTA country, there would be a repeater tower closer to where he
> lives. Over here, his reception problems are attributed to 8-VSB.
>
> Bert
>
> _________________________________________________________________
> It’s the same Hotmail®. If by “same” you mean up to 70% faster.
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q_broad1_122008

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