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Help diagnosing problem with Hdmi extender

Discussion in 'Cables & Switches' started by Goof, Feb 17, 2012.

  1. Goof

    Goof Member

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    Was wondering if anyone could help, I bought an Hdmi 1.2 extender last week off amazon and a couple of new cat6 cables. On receipt I hooked them up but when trying them from my free view box I was getting green dots all over the picture (on my ps3 I got no image at all). I made the possible mistake of not getting shielded cables, but I am only running 15m whereas they should be good for at least 30 on cat6.

    So, I sent that extender back and ordered another extender (looks exactly the same with the integrated Hdmi connector) but this one does v1.3. Unfortunately the exatc same symptoms though!

    So, are my network cables the problem or something else (they carry data ok)?
  2. andy1249

    andy1249 Active Member

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    One of the main functions of these units is a balun ( balanced to unbalanced ).

    Your converting the balanced HDMI signal to an unbalanced signal. The unbalanced signal is very very prone to noise.

    Because of the extremely high bit-rate , the network cables between them must be shielded. It doesnt matter how long they are , shielded works , unshielded usually doesnt.

    You are getting sparklies ( green dots ) and or no picture , that is typical of unshielded network cable used in this way , so , get shielded cable!
  3. stevelup

    stevelup Active Member

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    Cat6 is balanced too - that's the whole point of it. HDMI over Cat6 transceivers aren't baluns.

    Analogue video such as VGA uses baluns - converting the unbalanced video signal to a balanced signal for transmission over the twisted pair.

    We've just completed an install into 80 shops - all unshielded, all runs over 20M and everything worked fine. In fact, the extra capacitance of shielded Cat6 often makes things worse rather than better.

    It sounds to me like the original poster may be trying to use cheap passive extenders. Which ones are they?
  4. Goof

    Goof Member

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    Thanks for the replies - they are the unpowered ones (no brand) with integrated Hdmi cable you can find on amazon or eBay for 20 quid. I had to move my install into the sitting room (2nd son was born last week and selfishly stole my home cinema ;) ), the pj is ceiling mounted and wanted integrated connection if possible to cut down on messy looking longer cables. Likewise, preferred unpowered if poss...but looks like this might be a stretch too far.

    Question is, what's the best way forward - Steve, sounds like you're suggesting shielded cables probably won't help. If I have to compromise, I suppose I could get an extender with separate hdmi's, would prefer not to have to power as well though!
  5. andy1249

    andy1249 Active Member

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    Not all of these units work the same way ,

    HDMI is 19 pins , the pin out is here on the right ,

    HDMI - Wikipedia, the free encyclopedia

    Note each TMDS pair has a shield connection , now , two runs of CAT5/6 cable has 4 twisted pairs in each cable , thats only 16 wires , meaning that most of these units work by eliminating the shield connection between the TMDS pairs , some even split one of the TMDS pairs over separate twisted pairs in the cat5/6 cable , meaning any description of signal being still balanced as defined by the HDMI spec is tenuous at best.

    The signal needs all the help it can get when being sent over these cables , shielded is best.

    The vast majority of these units highly recommend shielded cables , see here for a quite blatant example .... they cant say it enough , and for good reason.

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

    Quote :

    OP , Shielded cables dont cost much more than you have , Ive seen many many of these units perform fine once you use shielded cable , its worth a shot.

    If that doesnt work , you should know that HDMI sockets are not designed in the same way as USB sockets and were never designed to power external devices , your units must get power from somewhere , so they are stealing it from the interfaces of the devices they are connected too , that could also be your problem , trying shielded cables is the cheapest first option.
    Last edited: Feb 17, 2012
  6. Joe Fernand

    Joe Fernand Active Member Assured Advertiser

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  7. stevelup

    stevelup Active Member

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    Goof, it's only 15M - just use a decent quality 15M HDMI cable and save yourself a load of pain.
  8. stevelup

    stevelup Active Member

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    That has zero chance whatsoever of working even over a few metres so it's pretty unlikely! What some of the nastier twin cable units do is put one of the TMDS pairs onto the second cable which then screws everything up unless the two cables are identical.

    Nope, only the cheap ones! None of the decent units ask for shielded cable.

    Shielded Cat6 is an absolute nightmare to work with, and impossible to terminate properly without expensive tooling. I guarantee you that you won't find any professional installer using it.
  9. andy1249

    andy1249 Active Member

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    Thats a very loose definition of the term professional dont you think?
    If I was Hiring a professional installer , I would expect him to have the proper tools for the job , how much they cost him is not my problem.

    His ability to handle shielded cable should be a very basic requirement in my opinion , and if I was paying for a professional job , Shielded cable would be minimum I would expect.

    Anybody telling me that Im not getting shielded cable because its too hard to work with would seem like an amateur to me.

    I work in HDMI design , Ive seen units as described above , some are very poor , some are very good , most work best with shielded cable , all of these units were expensive when they first showed on the market , the "cheap" Neet ones I would call the most popular at the moment , simply because they work well.

    I dont generally work with Network cable at the moment , though have done in the past , I wouldnt call myself a professional at it , but I have a 100m reel of shielded cat 6 that I ran and terminated myself for my home network , It wasnt that "hard".

    See the links below , it took me about 20 minutes for the four connectors I needed for the two runs to my Router. The tools cost me about 45 pounds , and if a so called professional was having trouble with it , I wouldnt be hiring him.

    http://www.lanshack.com/installing_cat6e_plugs.aspx

    http://www.lanshack.com/shielded-cat6a-jack.aspx
    Last edited: Feb 18, 2012
  10. stevelup

    stevelup Active Member

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    Utterly pointless using that for a connection to your router. What do you think it can possibly have achieved?

    If a professional told me I needed shielded Cat6, I'd send him packing.

    Sorry, but I do not agree with you at all. Not one bit.

    In your first post, you referred to HDMI extenders as baluns, and suggested that Cat6 was unbalanced - can you expand on that?
  11. andy1249

    andy1249 Active Member

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    I already have , in post 5 , or would you like to argue that the signal is the same as it exists on a standard HDMI link ?

    Why not? Its better than I'll ever need! Why put in the bare minimum and risk having to rip it out again in the near future , its my network , I'm not kitting out an office block to a budget here !

    Also , within the last five years Ive gone from broadband speeds of 512Kbps ADSL to 100mbps fibre , with all kinds of devices ( smartphones , broadband , PC's and macs ) competing for bandwidth , who knows what the next five years will bring , I could be streaming 4K Content to all kinds of devices by then ! Im not in the habit of ripping my walls apart every few years.

    There are wireless devices both in my home and in the neighbours sending out at 2.4ghz , 5ghz and all kinds of frequencies in between , todays home is a soup of noise , I want shielded cable in my network , and I now have it , it wasnt as difficult as you seem to think it is and it cost a pittance in relation to the rest of my gear , whats your problem with me having it ?
    Last edited: Feb 18, 2012
  12. stevelup

    stevelup Active Member

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    You didn't explain anything in post five. HDMI uses differential signalling just like ethernet and relies on balanced twisted pair cables.

    No it's not.

    No you're not. Tell me which bit of a HDMI over Cat6 cable is unbalanced?

    No they mustn't be.

    That's completely untrue.

    You can do whatever you like - no-one is going to stop you. The point I'm making is that it is unnecessary, but you are suggesting that it is completely necessary which is nonsense!

    None of this is helping the original poster who just needs to buy a 15M HDMI cable and be done with it. There is absolutely no point in messing around with HDMI over Cat6 for a 15M run anyway. Worse case scenario is drilling a slightly bigger hole that the HDMI plug will pass through!
  13. Goof

    Goof Member

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    Steve, I need to feed the cable under the floor so Hdmi was a no-go. I'd ordered up some shielded cat5 to try first off, no harm in trying that.
  14. Goof

    Goof Member

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    Well, the shielded cat5 works fine, take from that what you will. I dare say cheapo extenders need shielded, whereas better or powered ones may get by without.


    Edit: spoke too soon *sigh* getting flickering on the ps3 but free view works fine.
    Last edited: Feb 23, 2012

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