What causes interference (EMI?) on a DVI cable, and what can I do to stop it?

Question

I have a 50ft (supposedly high quality, 24AWG, triple shielded--whatever that means) DVI-D cable which weaves through walls, across other various power/computer/audio cables, through the attic, and into a kitchen. It's quite a journey. The highest resolution I can see on my LCD Monitor in the kitchen is 1024x768, and even then, there are occasional sparkles. I realize that DVI cables are not intended for these lengths, but don't really have any other choice. I bought a Gefen DVI Booster, which doesn't help. Would it help to attempt to shield the cable by keeping it away from other power/etc. cables. Or maybe wrapping foil or cloth, or something around it?

Answer 1

I think you partly answered your own question; I've done it with good, heavy-duty aluminum foil wrapped around the wire.

Answer 2

If the shielding is good on the cable then I doubt that adding more is going to solve this.

Running across cables is O.K. It is when you run next to a cable that you can get strong coupling between them.

The problem is that DVI does not send the full pixel clock, but pixel clock/8. If there is noise or degradation of the signal over the cable run then the signal can be degraded to be unreadable before the next clock pulse re-syncs it.

A different cable may help, but make sure you can return it if it does not. A different video card may help too, if it has better quality drivers, again there is no way to tell beforehand, so make sure you can return it.

Taking the 50ft cable back and getting two 25 ft cables with your repeater box in the middle of the run would also clean up the signal. The repeater should be bore than just an amplifier, it should receive the digital signal, and then send it on again totally clean, so it will be like having a 25 ft run rather than the 50 ft.

Answer 3

lead foil, or move one of the things closer to the source. Box closer to Monitor or Monitor closer to Box.
Can the Gefen be placed midways?