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Thread: Finding and eliminating HDTV interference QRM

  1. #1
    Join Date
    Oct 2017
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    Raleigh, NC, USA
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    Default Finding and eliminating HDTV interference QRM

    Not everyone gets to choose to live miles from their nearest neighbor and far away from the nearest cell phone/FM/TV/ham/CB tower. Interference is simply a fact of life for most of us. With HDTV it is impossible to identify the source of interference simply by looking at the artifacts in the picture - most of the time you don't even know that it is interference causing the poor reception.

    Back with analog TV you could frequently tell exactly the source of the interference - maybe not where it was coming from but you could ID it. Anyone out there have any suggestions for identifying and eliminating interference with HDTV?

    There are ways to block some of it if you just had a way to identify it!

    Suggestions? Comments?

  2. #2
    Join Date
    Mar 2007
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    Pembroke Pines, FL, USA
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    Dunno if this is the answer you are looking for....but....

    Maybe this is what you need:

    https://www.channelmaster.com/TV_Ant..._p/cm-3201.htm

    You might get it cheaper by shopping around, and I believe that other brands make these too.

    I don't use one, but I know (after a years-old thread here) that 4G/LTE is the cause of TV analog* channels 57-61 acting up on all my tuners.

    Did that help?

    [*Analog TV in nearby Cuba is still alive and well for at least 3 more years. Note this 2011 video, prior to the proliferation of smartphones:

    https://m.youtube.com/watch?v=3X0PNcnE6_0

    It's my most-viewed YouTube by a long shot.]

    cd

  3. #3
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    Yeah ... I know how to eliminate some types of interference - the problem is identifying what the source of the interference is! Can't get rid of it until you know what you have unless you want to buy every toy out there and add them one by one until you get rid of it!

    The solutions are out there for a lot of different types of interference - figuring out which of them you need is the problem - FM trap - LTE filter - single channel notch filter - ferrite cores on which devices/cables - have a talk with which CB/ham operator - replace which dimmer?

    My issue is that with HDTV you can no longer use the TV image/sound to diagnose the source of the interference. The interference is still there just as it was in the analog days - it's just that now it doesn't give you clues to identify the source - you just lose your picture. You can't tell if it's because of signal fade or a neighbor with a 500w CB linear feeding a poorly matched antenna!

  4. #4
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    OK....would it be possible to use an old analog TV, side by side with your digital TV, and have antennas hooked up to both, using a splitter.....and tune the analog TV to the same RF channel used by the interfered TV station? Maybe the analog TV would display the QRM somehow. (If you cannot use a splitter, you can switch the cable from the digital antenna input to that of the analog one.)

    Sorry if I'm not an expert about it, but maybe it is worth a try. As far as locating the problem, I wouldn't be surprised if its cable/satellite bleed from a neighbor. I would think in that case, the cable/sat provider has the responsibility to trace it.

    JMO.

    cd

  5. #5
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    Certainly that's a possible solution - what would be nice is something portable to sniff out the problem. Can't check with neighbors anymore to see if they have the same problem - everyone has cable

    Don't know if I can get away with another TV around the house! Maybe one of those old battery portables if one could be found.

  6. #6
    Join Date
    Jul 2005
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    Pleasant View, TN EM66
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    I suppose you could try RTL-SDR: https://www.rtl-sdr.com/about-rtl-sdr/

    It would give you a spectrum display which might give you some idea of the nature of the interfering signals.
    Doug Smith W9WI
    Pleasant View, TN EM66
    http://www.w9wi.com

  7. #7
    Join Date
    Jul 2011
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    Don`t forget about second harmonix of FM stations onto the hi-VHF band. I have a continuing problem getting KETA-13 OKC (4 channels) which I am pretty sure is caused by 214.2 MHz radiation out of KNID 107.1 Enid. Right in the middle of ch 13, 210-216 MHz. One of my antennas almost always gets breakup, another sometimes not, and best of all are rabbit ears precisely positioned (if I get enough signal in the first place from OKC). 73, Glenn Hauser

  8. #8
    Join Date
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    Thunderstorm, KY
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    Hi Jim...

    I've already had my issues with cell site interference...

    http://forums.wtfda.org/showthread.p...have-a-problem

    ... and it's only going to get worse.

    It's now my understanding that T-Mobile is making a big push to occupy frequencies that are mixed in with existing TV stations on channels 38 through 51. So, now, we not only have to eliminate whole chunks of RF spectrum (as I had to do with everything above channel 51) we also have to figure out which specific channels / frequencies, in the 38-51 range, are causing interference and eliminate / notch / trap those channels / frequencies. Whatta mess!

    I feel your pain, Jim.

    73, Ed NN2E
    Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds
    "You Might Be a Redneck If...
    Your TV is on 24/7.
    Your TV has been permanently on for over a decade.
    The only time your TV is off is during a power outage.
    Your TV gets 512 channels, but you go outside to use the bathroom.
    Your new TV is sitting on top of your old TV.
    Your TV costs more than all of your other furniture.
    Your deer-stand has a TV antenna on it.
    Your cable provider has no idea that you exist."
    Jeff Foxworthy

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