Originally posted by centaur
Ideally H & V would each be twisted with their own returns, but this is overkill. Common ground/shield is fine, twisted with these.
I will make this, and also will attach shield to only one end, to eliminate ground loop. Also will solder shield to connector shell, (hence the hood) for further shielding. (Less heat than it seems)
The point some make about the -'s & ground being commoned internal to the VGA card or display is true on many cards, but I'll connect private returns for the colors in anticipation of higher-quality cards.
Thanks Thumper & MrWigggles. I never would have dreamed the impedance of SCat5 would be close enough. What I think is happening here is the long runs you are using are reducing the effective impedance to the correct amount. Still though, I am surprised.
I'll let you know how it works with my Marantz VP12s1 on HD. Right now I have a 25' shielded VGA cable, and have one level of ringing (faint), only on black text with white bg.
The term ground loop is very poorly understood. Having two ground conductors doesn't make a ground loop. Ground loops cause problems when power ground current goes through signal lines.
The grounding mentioned in this design idea is all common. The R-, G-, B-, H-, V- etc. are all the same signal which is ground or GND. Length has nothing to do with lowering characteristic impedance, Z, of a cable. Having additional conductors, in this case the shield, in close proximity is what lowers the characteristic impedance.
Also, please bear in mind this Cat 5 technique is generally meant for cables that use HD-15 connectors on one or both ends. If you have a component output and a component input, I would recommend miniature bundled coax over what I have described here in a heart beat. Belden makes some good cable as well as others.