----- Original Message -----
From: "mch" <[EMAIL PROTECTED]>
To: <Repeater-Builder@yahoogroups.com>
Sent: Tuesday, December 20, 2005 7:48 PM
Subject: Re: [Repeater-Builder] hdtv radio shack ant ????
> You know, this subject (mail subject line) reminds me of the stories I
> was told about them coming out with antennas for *COLOR* TV that were
> interpreted to be different from B&W TV antennas. Supposedly, for color
> TV you needed a Color TV antenna.
>
> B&W TV, Color TV, HDTV... they ALL use the same frequencies and the same
> antennas would work equally well.
>
> Joe M.
>
Yes, that is true, to a point. The 8VSB modulation used by DTV is prone to
multipath interference. This is easily seen with a spectrum analyzer when
turning an antenna...multipath will show up as a notch (or multiple notches)
in what is supposed to be a flat noise-like energy spectrum form the DTV
transmitter. Depending on where the notch is in the spectrum and its depth,
the digital decoder and loose lock on the signal with the result being the
dreaded blue TV screen. Thus, the best DTV performance is from antennas
that are more directional which reject any off-axis multipath signals
better. Multipath is why indoor antenna reception of DTV is so touchy.
However, the later generations of tuner chipsets are getting much better at
multipath compensation.
Hap Griffin
VP-Engineering
SCETV
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