[opendtv] Re: News: No Motive for HDTV Rollouts
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 28 Jun 2004 13:21:58 -0400
----- Original Message -----
From: "John Willkie" <johnwillkie@xxxxxxxxxx>
> Funny how all those stations had to upgrade their transmitters to deal
with
> non-linearity that didn't much matter with analog, but would have
prevented
> them from transmitting digital, if all that changed was sending digital
bits
> on an analog carrier. Only transmitters that were less than 5-6 years old
> didn't routinely have to be upgraded.
As John knows, an NTSC transmitter is designed from the ground up to
transmit two narrow carriers, one at the visual and one at the aural
freqencies. Modern IOTs can be retuned for wideband operation, but older
klystron transmitters, especially those with separate visual and aural
tubes, simply cannot transmit across the entire 6Mhz band linerally. Some
of the later MSDC klystrons may be an exception, if the aural cabinet is
removed or converted to a second wideband amplifier. I have my doubts about
an old RCA rig, though.
Then you have NTSC antennas that were peaked for the lowest SWR at the
visual and aural frequencies, not necessarily for flat response across the
band that have to be replaced as well, even if DTV were to occupy the same
frequency as NTSC.
> That, however, should not be used as any support for Bert's "full HDTV
> transmitter" which is just as non-sensical as your response. Is there
such
> a thing as a semi-HDTV transmitter?
Excuse me for speaking on his behalf, but perhaps Bert was referring to full
"POWER" HDTV transmitter. He has been known on occasion, and rightly so, to
cite low power and low height DTV transmission facilities as being a large
part of ATSC reception woes.
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