HDMI over Cat5e extender interference/noise?

Discussion in 'Cables & Switches' started by dingledell, Dec 30, 2011.

  1. dingledell

    dingledell
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    Hi folks,
    Please help;

    I am using a HDMI over cat5e extender;

    Neet® - HDMI Extender over Cat5 / Cat5e / Cat6: Amazon.co.uk: Electronics

    to send HDMI from my PC to my TV screen in another room which is only about 9 Metres away.

    I am using 2 of my existing installed (9 Metre) Cat5e UTP cables that are terminated with RJ45 wall plates, into which I have short Cat5e patch leads to the sender/receiver units. However, I am getting what I can best describe as black interference/freckles/snow/noise in the image (please see pic below).

    The receiver unit has a 5V DC power unit which appears to make no difference.

    I have set up a trial to test the sender by sustituting my 9 Metre Cat5e cables with 2 1M patch leads and the image is fine.

    After reading for hours on this (excellent) forum, I am suspecting that the 5e cables must be getting some interference or that I should have spent a bit more on the sender/receiver?

    The 9M cables at one point are about 4 inches from a 240V power socket :rolleyes:

    In order to avoid a huge re-installation of cables; Please could anyone advise me whether a more expensive extender with 2 power supplies, such as the 'OCTAVA' could/would improve the picture?

    Many thanks for reading. Any help will be greatly appreciated,

    dingle.
     

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  2. andy1249

    andy1249
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    UTP = Unshielded Twisted Pair
    Almost every single version of these extenders on the market recommend using shielded Cat5/6 cables.
    So , I strongly suspect that this is the issue.

    Edit : See the notes on the Amazon page , every other extender ( including Octavia) will have exactly the same requirements , So replacing the UTP with STP is your first step before spending more money on other extenders

     
    Last edited: Dec 30, 2011
  3. Joe Fernand

    Joe Fernand
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    Many Extenders don't work too well on short (sub 15m) CAT cables - the Octava HDCATIR will work on pretty much any cable from 1m!

    Joe
     
  4. dingledell

    dingledell
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    Krikey,
    Thanks for lightening fast replies.

    Yes, I also suspect the UTP may be picking up some interference Andy.

    Thanks Joe but I tried setting up over 1M cables and the picture was fine.
    Do you think the OCTAVA would deal with the suspected 'noise' on the 9M cables any better than the cheaper extender that I have?
     
  5. dingledell

    dingledell
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    Having re-considered this I'm now doubting that the symptoms are a result of interference.
    If I lower the resolution on the PC the pixel problem isn't there.
    Surely if the Cat5e cablles were suffering interference the picture would show symptoms at any resolution and be more intermittent/jumpy/spikey rather than constant speckles at only high resolution?
    My guess is that I have a poor quality feed into my receiver box due to cable length/quality/wall connectors/patch cables.
    The optional 5V power to the receiver obviously won't help if the signal it receives is weak.
    Now the OCTAVA and other more expensive extenders appear to also have power to the transmitter.
    I'm now minded to try a '2 power suppply extender'
    Or maybe I'm being optimistic?
     
  6. andy1249

    andy1249
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    Going by your picture, what you are seeing is sparklies , this is normal behaviour for sending high bitrate content over a long distance using cat5/6 extenders with UTP cable.
    It is a well known fail signature and the lack of shielding is the root cause , by unbalancing the signal ( which is what the extenders do ) it becomes prone to errors at higher bitrates and you must use STP or Shielded Twisted Pair cable.

    Lowering the resolution means significantly lowering the bitrate and as such the interference does not affect the signal as much. Read the reviews from your extender product on amazon , you will see that many users have your problem and fixed it by using shielded runs of Cat5/6.
     
    Last edited: Dec 30, 2011
  7. dingledell

    dingledell
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    Thanks again Andy,
    I'm now minded to take your advice and look at the cable spec.

    I'm going to look at setting up a test using 9M improvised patch cables (made of the left over Cat5e from the original install) in place of the installed ones and running them where there is no possibility of interference.
    By my reckoning, if the picture is ok under this test then it's confirming your diagnosis of a need for STP.

    I'll post my findings soon.

    P.s One question that has me baffled is why Cat 6 is often recommended when it appears to be (almost always) unshielded?

    Many thanks again Andy..
     
  8. andy1249

    andy1249
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    Cat 6 increased performance comes from better insulation that reduces crosstalk ,

    See here

    [​IMG]

    The "cross" section in the middle keeps each twisted pair apart , it also makes crimping them a hell of a lot more difficult , especially if using solid core , but there you go.
     
  9. dingledell

    dingledell
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    Oh well,
    I rigged up a test using 2 * 9M lengths of the same UTP hoping to prove the UTP was the cause and thus justifying me ripping the house apart to install STP. However I really needed to include the wall plates/modules to keep the exercise true.

    Now I really didn't fancy disconnecting/detaching/re-connecting the existing modules so I nipped to Screwfix and got 4 of their RJ45 modules expecting them to be pretty much the same as my MK ones.
    I tested the new set up (including new modules) for continuity then plugged into baluns/TV/PC.

    No picture whatsoever ! :devil:

    All I have learned is that my Screwfix modules aint as good as my MK ones. :rolleyes:

    I did notice however, that with the original set up; If I tried using different combinations of my RJ45 ports/cables the picture varied quite a lot and 1 paricular combination showed a fair improvement.

    Now I was looking at reluctantly using the MK mods (yes, I know; like I should have the first time:facepalm:).

    However, along the way I stumbled upon these on the web;

    HDMI over Cat 6 HDBaseT Super HDMI Extender

    Now they are a bit pricey but given the choice of taking the £300 hit or stripping half the house, they begin to look cheap. Also they should free up 1 of my cables.

    Has anyone any advice/experience of these before I 'bite the bullet' ?

    Regards,
    Ding
     

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