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Digital TV Antennae upgrade

Discussion in 'Hobby Electronics' started by RMD, Dec 29, 2011.

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  1. RMD

    RMD Guest

    Hi All,

    I'm in a difficult reception area here at Salisbury Heights in
    Adelaide. I have a ridgeline which shields me from the Mount Lofty TV
    transmitter antennas, and a 33KV trunk mains running across in front
    of my antenna complex.

    I have a two antenna set-up which I installed in 1996. It consists of
    a VHF/UHF Tandy 18 element VHF/UHF antenna plus a 12-element UHF
    antenna which I bought from K-Mart (I don't remember the brand). The
    two aerials feed into a VHF/UHF Tandy masthead antenna amplifier.
    There are also indoor booster amplifiers on the 6 room distribution
    system. The antennae system supplies signal to multiple TV's, PVR's,
    VCR's, FM radios, & DAB+ radio.

    UHF reception of SBS with the K-Mart UHF antenna is excellent, whereas
    the Tandy antenna is getting a bit sick up at analogue Channel 10.

    Digital TV reception is excellent for Channels 7, 9, 3, and 44 but is
    dodgy on Channel 10 and Channel 2. Channel 10 digital is the worst
    performing channel.

    My Strong PVR gives the following numbers for signal strength/quality
    with the Tandy/K-Mart antenna:

    (Ch7 83%/95%, Ch9 85%/95%, Ch10 81%/47%, Ch2 73%/50%, Ch44 83%/95%,
    Ch28 99%/95%)

    The above figures show why digital Channels 2 & 10 are bad performers.
    This is so particularly with a north wind which has the 33KV trunk
    line producing plenty of impulse noise.

    Anyway, I replaced the Tandy UHF/Antenna with a MatchMaster 01M-LP03F
    log-periodic antenna. Matchmaster actually recommend the 01MM-DC21A
    antenna for my location on their web antenna selection facility.
    However, my local Jaycar store had the LP03F in stock and it was only
    $79 instead of $149, so I figured I'd give the cheaper antenna a go.
    The performance figures seem much the same.

    So, I've kept the existing UHF K-mart antenna (which has strong and
    excellent performance), and put in the Matchmaster in to replace the
    old Tandy UHF/VHF antenna.

    I'm only using the UHF performance of the Matchmaster antenna, because
    of the old Tandy masthead amplifier requiring separate VHF and UHF
    antennas.

    My Strong PVR gives the following numbers for signal strength/quality
    with the Matchmaster/K-Mart antenna:

    (Ch7 90%/95%, Ch9 85%/95%, Ch10 85%/95%, Ch2 82%/95%, Ch44 82%/95%,
    Ch28 99%/95%)

    So, the Matchmaster log-periodic antenna has improved Channel 2 and
    Channel 10 reception to aproximate the Channel 7 and 9 performance
    with the old antenna system.

    The FM radio signal strength has dropped compared to the old antenna,
    but is still quite workable. The DAB+ radio seems to have perfectly
    adequate signal strength and is apparently working well as I write
    this.

    So far I'm jolly pleased with the results. Channel 2 analog even still
    works after a fashion, and is quite watchable in an emergency, which I
    didn't expect at all., since the Matchmaster is a Channel 6-12
    antenna.

    I'll be interested to see what happens with a north wind which usually
    has the 33KV trunk mains generating plenty of impulse noise. I have a
    heat wave/north wind coming soon, so I ought know how the new
    antenna copes in a week or so.

    So far I'm very pleased with the results. :)

    Ross
     
  2. RMD

    RMD Guest

    Errata

    <<<<I'm only using the UHF performance >>>>

    Should be "I'm only using the VHF perfornance" of the MatchMaster
    antenna.

    Ross
     
  3. RMD

    RMD Guest

    Hi All,

    We are in a heat wave here and the 33KV trunk main insulators are
    breaking down and producing quite severe impulse noise. This is
    visible as dashes on the screen from analogue Channel 2 to analogue
    SBS, and is breaking through the FM sound too.

    The new antenna setup has produced a fairly significant improvement
    in performance of previously susceptible equipment, but hasn't
    resolved the problem completely.

    I've found for best noise resistance the TV signal needs to be in the
    "Goldilocks zone" for any particular piece of equipment. In other
    words signal levels need to be "just right".

    The only problem is that the Goldilocks zone can differ for different
    digital TV devices. I have some Dick Smith variable gain booster
    amplifiers and using these to raise/lower the input signal level can
    help in finding the aerial signal "sweet spot".

    Even given the optimum signal level, then different tuners perform
    better than others, and price is no particular pointer in regard to
    this tuner performance.

    I have a fair idea where particular tuners fit in the performance
    heirarchy, but recently I rewired an antenna feed arrangement which
    was feeding, amongst quite a few other things, a Telstra T-box. I
    think there was possibly a dodgy cable interconnect somewhere in this
    particular antenna feed leg.

    Anyway, the Telstra T-box is now the best performing tuner in the
    house, whereas before it was one of the worst. Other tuners on the
    same feed are quite a bit better too, but not by such a lot. Somehow
    it happens that signal conditions are now really optimum for the
    Telstra T-Box.

    I also find high impulse noise levels can produce all sorts of
    equipment operational weirdness.

    For example, PVR's start recording but don't ever stop recording.
    Repeat recording times can suddenly skip a week. Using the remote
    control to set PVR's up can result in quite erratic behavior, and
    pulling out the aerial feed fixes the problem and stops the operation
    erratic-ness.

    In fact, it is easy to think that the dodgy equipment has suddenly
    developed an intermittent fault. Except that pulling out the aerial
    feed cures the problem.......... And the very next day without high
    impulse noise levels about then the equipment is back to being quite
    docile and well-behaved again.

    Luckily most of this really quite bizarre behaviour only happens quite
    rarely on really bad impulse noise days, and these bad days don't
    actually happen all that frequently.

    There is also a variation in impulse noise during the day. It usually
    gets gradually worse as the day progresses, but then gets better
    during the evening and often about 8pm or so the impulse noise
    completely disappears until about mid-morning the next day.

    Anyway, this diurnal effect means much evening viewing works out fine.
    Recording things at midday or afternoons is usually the worst time, if
    there is going to be trouble.

    Anyway, with the new antenna setup, then SBS is the most reliable
    feed, followed by Channel 7 and 9. Channel 2 is usually better than
    Channel 10, but not always.

    If everything performed as well as SBS does then I wouldn't have much
    of a problem.

    Ross
     
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