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Bad HD Signal
Hello,
I have a new BMD Decklink Extreme in an 8 core MacPro FCP system. The problem I am having is to do with a corrupt or bad HD signal – and all of our tests point to the card itself.
Basically we are finding that on moderate cable runs through our building that when we use the Mac system the HD signal erratically breaks up (audio and video). It’s like it’s almost there but doesn’t quite make it. We have correct Sync and the cable run is fine because when we connect other HD kit to the end we have no problems. All the cabling is professionally fitted and HD grade (I forget the cable name). The problem is that when we use very short cable lengths (i.e. move the deck from the machine room into the suite) we don’t have any problems.
I’m just asking if there are any other avenues to take before we ditch the card and send it back.
Many thanks,
Paul
Freelance DS/Symphony
London -
1 Reply
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you must use professional double shielded cable like Belden 1505A, Belden 1855A or Belden 1694A (Gepco VPM2000 works too), as well as some Canare cable models. If you use standard analog cable, like Belden 8241 (standard RG59 cable), no HD signal will travel beyond 150′. My first experience of this was to run 2 cables to a patch bay – both the HD card (an AJA) and the HD VTR were 100′ from the patch bay. The HD signal (a square wave) breaks down, but stays stable with with better quality cable. You can actually see this if you have a waveform monitor that displays an “eye” pattern, like the Tek WFM-601i.
How long is your “moderate run” 100 meters is not a moderate run – this is the total distance any HD signal can run – even with the best cable.
Bob Zelin
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