HDMI causes RF interference?

Discussion in 'Cables & Switches' started by pdonovan, Nov 29, 2005.

  1. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Hi,

    I got my new Sony Bravia V32A12U LCD set up last night. I've got a Mac mini connected to the HDMI input via a 2m DVI-HDMI cable from Videk. It took me about 3 hours to work out that the reason I was getting terrible RF signals (analogue, built-in Freeview and RF output from a Tivo) was because I had the HDMI cable connected! As soon as I unplug the HDMI cable from the TV the RF picture improves drastically.

    I've done a few google searches and have seen a few product descriptions saying that their cables are shielded to prevent RF interference, but there's nothing on these forums about it. Have I bought a crappy cable? 1280x720p on the Mac shows a view sparkles on the desktop, and 1920x1080i doesn't show at all, though the TV's OSD does say 1080i. This post http://www.avforums.com/forums/showpost.php?p=1910364&postcount=2 indicates that 1080i from a Mac via DVI should work fine.

    Can anyone recommend a DVI-HDMI solution. I've seen a QED cable for £49, are they any others that are known to not suffer from, or in my case, cause, RF interference?

    Thanks,

    Paul
     
  2. Nic Rhodes

    Nic Rhodes
    Well-known Member

    Joined:
    Mar 23, 2001
    Messages:
    17,152
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    133
    Location:
    Cumbria
    Ratings:
    +1,276
    all cables suffer to some extend and then stop working. To find ones that are well shielded look to ones that can go down long lengths even if you you don't need the length. Bettercables I think will help the problem, see The MediaFactory, forum sponsors. They have about the best track record in this respect. Also look to re siting the cables in different locations.
     
  3. ianh64

    ianh64
    Active Member

    Joined:
    Aug 7, 2004
    Messages:
    2,233
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    SW London/Surrey borders
    Ratings:
    +63
    You may have a ground loop problem.

    As for cables, Molex cable 88768-3510 is the 2m HDMI/DVI version. Costs about £10 + VAT + P&P from www.cpc.co.uk .

    It may be cheap, but Molex are one of the original people involved in HDMI. I believe that they are the only/most prolific manufacturers of HDMI sockets. Their cables are well constructed and work exactly as they should. If you fancy something more flash, just wrap tinsel aroud it and tell everyone it costs £50.
     
  4. StooMonster

    StooMonster
    Well-known Member

    Joined:
    Nov 20, 2002
    Messages:
    4,974
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    Kent
    Ratings:
    +314
    Yes you could have a ground loop problem, this usually shows up as horizontal bands of brightness / darkness on the screen.

    Shielding is key to digital cables, and poor quality shielding increases jitter (which shows up as "sparklies") and can create EMI / RFI problems for other kit. You'll note that some DVI / HDMI cables have bit fat ferrite cores at either end of the cable, this is to kill of EMI / RFI, perhaps a cable like this could help solve your problem. Your Mac should have zero sparklies on the screen.

    StooMonster
     
  5. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    If that's what a ground loop problem looks like then I don't think that's what I've got. The picture looks like I'm using a coat hanger for an aerial. I've attached a picture of analog TV. Simply unplugging the HDMI from the TV makes the picture look perfect.

    My cable doesn't have any ferrite cores on it. I plugged it in again last night and didn't see any sparkles, so it's definitely subject to positioning or dodgy contacts. I tried separating the cables but on the Bravia the RF and HDMI ports are close to each other.

    I looked at the Molex cables from www.cpc.co.uk but they didn't have any in stock. I've order one from Blue Jeans Cable who seem to have a good reputation (from what I've seen, hope I'm not wrong!) I want to get this resolved quickly so I know whether I have to return the TV or not.

    Thanks for the help guys.
     

    Attached Files:

  6. StooMonster

    StooMonster
    Well-known Member

    Joined:
    Nov 20, 2002
    Messages:
    4,974
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    Kent
    Ratings:
    +314
    Your picture looks like RFI interference, hopefully you ordered an HDMI cable with ferrite cores at either end which would stop your HDMI cable broadcasting. Another alternative is to buy some clip on ferrites.

    StooMonster
     
  7. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I initially thought they were out of stock when you first mentioned Molex, but I made a mistake. I have one of those on order too now! I ordered a couple of ferrite cores (CPC no. CBBR6910 ) too as they're cheap, but an electronics guy here isn't sure they'll work. Worth a shot though :)

    If both of the cables I've ordered don't fix the problem then I might have to consider sending the TV back. And I got it through staff sales (I work for a division of Sony) so the customer service for returns isn't straightforward :(
     
  8. Nick_UK

    Nick_UK
    Banned

    Joined:
    Nov 13, 2004
    Messages:
    9,748
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    103
    Ratings:
    +270
    You can tell that it's radiation from the cable, because (if you look carefully) you can make out the field and line blanking lines (looks like a cross on the display). As well as the ferrite'd cables, you could make sure that your RF cables are foil screened - most aren't. You may need to make your own RF interconnects - make them from foil-screened co-ax, and keep them as short as possible.
     
  9. StooMonster

    StooMonster
    Well-known Member

    Joined:
    Nov 20, 2002
    Messages:
    4,974
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    106
    Location:
    Kent
    Ratings:
    +314
    So why does he think almost all digital cables these days have ferrites on the ends? For decoration? ;)

    StooMonster
     
  10. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    :)

    His theory was that HDMI runs at very high frequencies (up to 750Mhz), much higher than an RF signal, so where's the interference to the RF coming from? And if I put ferrite on the HDMI lead then all it'll do is block specific (lower) frequencies, not the ones the HDMI uses. He did admit that his university electronics knowledge is very hazy....and I only did A-level physics :)

    Plus, none of the HDMI cables I've looked at have had ferrite cores on them. But yeah, keyboard, mouse, VGA and Playstation pads all have the cores on them, but they don't operate at 750MHz do they?

    I'd love a good explanation of interference in these situations, I'm intrigued now. Fingers crossed I'll get it sorted.
     
  11. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I've got rid of most of the RF interference I was seeing, in fact, only analogue BBC2 still has a bad picture, but not as bad as before.

    I re-routed the HDMI cable the other way under the TV (the Mac is on a shelf below the TV) and around the other side, finally going along the back of the TV. This keeps it as far away as possible from the RF lead.
    I also got a better shielded RF cabled (I was too impatient to attempt making my own) and the Blue Jeans Cable DVI-HDMI cabled arrived so I'm using that.

    Despite people saying that for shorter cables it doesn't really matter what you spend on an HDMI cable, this Blue Jeans cable is definitely better than the Videk, though both were around the same price. I don't get an sparkles on the Mac desktop with the new one.

    I've not had a chance to try the Molex one as CPC cocked up my order and seem incapable of sending me one :-(
     
  12. Nic Rhodes

    Nic Rhodes
    Well-known Member

    Joined:
    Mar 23, 2001
    Messages:
    17,152
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    133
    Location:
    Cumbria
    Ratings:
    +1,276
    Isn't that what I suggested at the beginning? Better screened cable and re siting.

    and yes there is loads of guff written about DVI / HDMI cables by people who don't know what they are talking about!!

    Still recon the Bettercables were you best option though!!
     
  13. JH4

    JH4
    Well-known Member

    Joined:
    May 6, 2003
    Messages:
    2,438
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    83
    Ratings:
    +285
    Did you check your TV aerial cable is foil screened, as Nick UK suggested ?
    That will help I'm sure. Old style single screened TV aerial cable is no good for modern setups. The cable should have a metal braid and a foil screen. (Hope you don't have to get the ladder out to renew it ! )
     
  14. Nick_UK

    Nick_UK
    Banned

    Joined:
    Nov 13, 2004
    Messages:
    9,748
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    103
    Ratings:
    +270
    Ever heard of harmonics ?
     
  15. Spanjab

    Spanjab
    Standard Member

    Joined:
    Apr 10, 2003
    Messages:
    33
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    6
    Ratings:
    +1
    Isn't the signal in HDMI digital then?
     
  16. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Sure, I just wanted to let people know how I was getting on.

    Unless I looked at the wrong one, it appeared to cost £70, more than double the cost of the Blue Jeans one and 7 times the price of the Molex cable!
     
  17. pdonovan

    pdonovan
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I can't replace the cable to the aerial I'm afraid - I live in a block of flats and the aerial is shared. It *is* in the loft that is accessed via my flat, but I don't fancy working out how the cable comes down the wall to the socket in my lounge. I'm thinking about changing the aerial to get better Freeview reception but don't want to annoy the other residents while I do it :D

    When I get some spare time I'll investigate building my own cable from the wall to the TV. Maplin seem to do the basic cable and 'high quality' nickel connectors. Any other suggestions for a source of parts?

    The one I bought (Cambridge Audio from Richer Sounds) claims it's aluminium mylar shielded but looks more substantial than the one it replaced.

    Nick, yes I have heard of harmonics, but I couldn't think of the term at the time so didn't suggest it in my initial query. I couldn't think of how to describe it clearly :)

    Edit: Corrected the type of shielding on the CA cable.
     
  18. FastEddieB

    FastEddieB
    Standard Member

    Joined:
    Feb 8, 2011
    Messages:
    1
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    1
    Ratings:
    +0
    Resurrecting an old thread from the dead, but...

    ...I was hooking a new ROKU box up to a Sony 32" Bravia with a really cheap HDMI cable ordered on eBay. Immediately started having wireless network issues.

    Seemed like if I went back to the video cable setup, the problem cleared up.

    Last night it occurred to me that RFI might be an issue, and Google led me to this site.

    My options are...

    ...buying a better cable, or...

    ...running an ethernet cable from my router to my ROKU box (which I was considering doing anyway for best speed, or...

    ...swapping ROKU boxes, since my new ROKU does not have component out and my old one does, and my Bravia only has one video input (already in use by a Wii).

    Though its old, this thread was useful to me!
     
  19. greyowl99

    greyowl99
    Standard Member

    Joined:
    Mar 6, 2011
    Messages:
    1
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    1
    Ratings:
    +0
    Hi people

    been looking at the many threads on this topic. Like many people, I have had loss of freeview signal quality when the HDMI link was active between my TV ( Sony 40EX503 ) and a Sony Blu ray player. I tried the usual: replace cables with better shielded ones; drive aerial amp from battery; putting ferrite loops on everything; shorter cables; longer cables; moving relative positions of the boxes; look for ground loops etc etc. The only thing that worked was to up the signal strength by changing from an internal aerial to a roof aerial but even then, although most MUX's now work, on weak signals there is still some interference present. Also, the effect occasionally reduces for a time then returns.

    In exasperation I just swapped the Sony with a Panasonic LCD ( TXL26x10b ) from elsewhere in the house and used all the original setup. Absolutely no interference on any MUX. I even degraded the signal as much as possible so that I had only 30% signal strength and 10-30% signal quality. I tried all ways I could think of to get some interaction between the HDMI link on/off and the freeview reception - zilch - the panasonic just worked.

    My tentative conclusion is that there is a design problem of inadequate RF shielding within some flat screen panel TV's

    Anyone else having similar experience ?
     

Share This Page

Loading...
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice