[opendtv] Re: VHF Stations Seek Solutions for Reception Problems, by Doug Lung

  • From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 30 Jun 2009 10:42:45 -0700

Good info,  though I couldn't read the IEEE article, not being a member.

The WRAL DTV tests were always somewhat suspect in my mind:

    I believe they utilized the same transmitter coupled into the H-pol and
CP antennas. If so, that would effectively make the CP signal 3db less than
that of the H-Pol system (using a standard H Pol receive antenna).

    If one uses a standard H pol receive antenna for the comparison testing,
assuming equal signal intensities, CP and H-Pol results will seem to be
identical (in a generally free space environment).
However, if one uses a CP receive antenna, the reception from CP is
superior. Also, such testing should include marginal antennas and
orientations and a multipath environment (where DTV CP should be superior
with modern DTV receivers.)

Dale

-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]On
Behalf Of Richard Hollandsworth
Sent: Tuesday, June 30, 2009 7:25 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: VHF Stations Seek Solutions for Reception Problems,
by Doug Lung


      A couple bad tests with DTV at WRAL and KCIU apparently trumped a
dozen positive on-air tests with analog:
      http://www.tvtechnology.com/article/67946
      http://cat.inist.fr/?aModele=afficheN&cpsidt=1845203
      http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplor
e.ieee.org%2Fiel5%2F30%2F17220%2F00793638.pdf&authDecision=-203

      holl_ands

      ====================================================
      --- On Mon, 6/29/09, Dale Kelly <dalekelly@xxxxxxxxxxx> wrote:


        From: Dale Kelly <dalekelly@xxxxxxxxxxx>
        Subject: [opendtv] Re: VHF Stations Seek Solutions for Reception
Problems, by Doug Lung
        To: opendtv@xxxxxxxxxxxxx
        Date: Monday, June 29, 2009, 3:48 PM


        Bert wrote:
        "Doug Lung always has interesting insights":
        I've known Doug for a number of years and he has always been a
reliable
        source of information and analysis.

        "One of them is use of circular polarization":
        CP simply works and at all frequencies, though possibly better at
some than
        others. I have constructed and/or tested a large number of CP
facilities for
        VHF and UHF TV as well as for FM radio. It significantly improves
reception
        where marginal antennas exist and where CP receive antennas are
used.
        Before CP. FM radio was virtually useless in automobiles until that
        transmission mode was adopted by broadcasters.

        It has been said by some, but with no supporting evidence that I
know of,
        that CP won't work well for DTV. However, I know of no reason why it
will
        not improve reception in all services and it seems to me that DTV
mobile
        simply will not work without it.

        Dale


        -----Original Message-----
        From: opendtv-bounce@xxxxxxxxxxxxx
        [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Manfredi, Albert E
        Sent: Monday, June 29, 2009 7:58 AM
        To: opendtv@xxxxxxxxxxxxx
        Subject: [opendtv] Re: VHF Stations Seek Solutions for Reception
        Problems, by Doug Lung


        Dale Kelly posted:

        http://www.tvtechnology.com/article/83128

        Doug Lung always has interesting insights. One of them is use of
        circular polarization.

        The situation here, specifically with WJLA-TV on VHF Channel 7, has
been
        steadily improving at our location. I wish I knew what they had
done.

        From no reception on the 12th at noon, to constant pixellation and
no
        sound that same evening, to sound with constant image problems in
the
        days that followed, last week we finally got solid reception in the
        upstairs system (the one with RS double bowtie and 3rd gen
receiver),
        and last night I got virtually solid reception donwstairs too (the
dual
        Antenna Direct DB4s in fireplace).

        Only minor adjustments done at our end. A slight turning of the RS
        antenna upstairs, and a bit of VHF relector assistance downstairs.

        When it works, VHF is nice for its consistency. It seems that
whatever
        the reception quality is tends to remain the same over long periods
of
        time. Compared with UHF, when operating close to the margin, which
tends
        to drop off entirely then come back.

        Bert

Other related posts:

  1. Home
  2. opendtv
  3. Archive
  4. 06-2009