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                      THE CGC COMMUNICATOR
                            CGC #916
                     Friday,  June 19, 2009
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                Robert F. Gonsett, W6VR,  Editor
                <cgc (at) cgc333.connectnet.com>
    Copyright 2009, Communications General® Corporation (CGC)
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  GENERAL NOTES ON THE SOUTHERN CALIFORNIA DTV TRANSITION
  There are no large and unexpected problems associated with
the southern California DTV transition according to informed
sources and e-mails reaching our office.  There are a number of
small fires and some unexplained oddities, but that is to be
expected.  Our problems are nothing compared to those in,
say, Chicago.
  Proper rescanning (with the old channel memory dumped) and
antenna adjustments seem to have solved perhaps 50-60% of viewer
complaints.  However, mentally impaired viewers unable to deal
with DTV converter boxes constitute an ongoing challenge for TV
stations, and even some informed viewers are still having trouble
coming to grips with the new DTV landscape.  As one frustrated
viewer put it, "Why can't I just put in the channel number and
watch TV?"
  Turning to another subject, there is a question of whether
high-band VHF channels now used for DTV in Los Angeles (Channels
7, 9, 11 & 13) are as robust as UHF for building penetration.
While a land-mobile engineer might say that UHF penetrates best,
the jury is still out on this important question for L.A. DTV.
  Some people, even professional antenna installers, were under
the mistaken impression that Los Angeles would become a UHF-only
DTV market, so a number of viewers were totally unprepared to re-
ceive high-band VHF when DTV lit up.  That was strike one against
VHF in the minds of many, but the judgement was premature.
  Strike two came from folks using indoor rabbit ear antennas
with fully extend telescoping elements.  Little did they know that
fully extended elements, while fine for low-band VHF Channels
2-6, were lousy for high-band VHF reception.  Once they shortened
the elements to 14 inches each, reception markedly improved.
  First time DTV viewers are of course just beginning to come
to grips with the digital cliff edge effect where either a perfect
picture is received, or no picture at all, regardless of whether
VHF or UHF transmission is used.  A viewer with an indoor antenna
is particularly vulnerable to deep signal fades caused by people
moving about near the antenna and interfering with the incoming
waves.  That's one reason why an elevated outdoor antenna is best.
  The large issue looming for southern California is summertime
temperature inversion layer ducting where signals from Tijuana,
San Diego and Los Angeles will invade each others markets.  CGC
is already suggesting that co-channel DTV stations institute
precision frequency offsets to counter this well known problem.
Our office has already started to work with those clients who
are most likely to be affected.
  Have we forgotten anything?  Let us know.  Short letters (100
words or less) are always welcome.  We hope this special report
has helped put the southern California DTV transition in
proper perspective.
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  Corporation (CGC), consulting radio engineers, Fallbrook, CA.
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