[opendtv] Re: USDTV demos at NAB
- From: Doug McDonald <dtvmcdonald@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 29 Apr 2004 12:19:29 -0700 (PDT)
--- John Shutt <shuttj@xxxxxxxxx> wrote:
> Bert,
>
> VHF runs at much lower ERPs than UHF for very good
> reasons, and you know
> them.
Not really. VHF uses lower powers because
a tuned dipole antenna has a receiving area
inversely proportional to the square of the frequency.
However, at UHF it is far easier to get gain; a UHF
antenna as big as a channel 2 dipole will have a truly
gigantic gain and will pick up the same actual
fraction of the ERP as will the Ch. 2 dipole.
Also, UHF signals penetrate modern houses with
foil heat barriers in the walls much better than
VHF, especially low VHF, because there are several
waves in the size of the average window at UHF, only
one at high VHF, and less that one on Ch. 2.
> VHF is much less line of sight.
This is true. Digital Ch. 3 needs far more power than
it is getting.
Doug McDonald
=====
Doug McDonald
my last name at scs dot uiuc dot edu, not here at Yahoo, please
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