Quote:
Originally posted by JHouse:
Thanks guys, it looks like I'm tearing out crown moulding again.
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Joe,
You've definitely got a cable problem. As Dean points out, using a better cable will also make your picture clearer. The ghosting is caused by reflections of the signal. With a "perfect" cable, the signals are sent from your source to your projector and arrive there pretty much as they were sent. When you've got reflections, the reflected signal interferes with the primary signal. The ghost is a copy of the original signal after it has bounced back and forth in the cable. It is shifted to the right due to the added delay of the extra travel time. Reflections are caused by impedance mismatches. An analogy is throwing a rock into a still pool of water. The ripples will travel to the edge of the pool and then bounce back toward the middle of the pool. This is because the edge of the pool has a different "impedance" than the water. If however, you could replace the pool walls with a material that had the same impedance as water, then none of the ripples would be reflected. From the rock's point of view it would be just as if it had been thrown into a pool of infinite diameter. Back to the case of video cables, what we want is something that looks like an infinitely long cable, with a uniform impedance (namely 75 ohms). Anything in the chain that is a discontinuity in this 75 ohm impedance will cause reflections. Poor quality cables and cable-to-cable junctions can cause such problems. The longer your cable is, the worse it's going to be.
As for your crown moulding, you should think about making your own cables using shielded cat 5 ethernet cable, as described in
this thread , as long as your cable is 40' or less. I have a BetterCables component cable encased in crown moulding and I really REALLY did not want to tear it out to add an RGBHV cable. The cat 5 cable is so thin that I was able to run it externally, just below the crown moulding. I glued it on using Liquid Nails, and painted it the wall color. No one would even notice that it is there if I didn't point it out. Gluing it on and painting it took me less that two hours. Tearing out and re-installing crown moulding would have taken may times that long. There are other advantages to this solution too, as outlined in MrWigggles initial post on the referenced thread.
- Chris
