What makes good
VGA cable is that each of the signals in carried inside a miniature,
impedance matched, coaxial cable inside the over-all
jacket. Each signal has its own tiny
coax, and there are five of them inside the
jacket. The
impedance matching and shielding of the coaxial contruction reduces signal loss and high frequency roll-off, and prevents standing wave reflections that would cause
ghosting in the
image.
There seems to be an un-written rule about
VGA cables. The ones with smooth jackets are not
impedance matched, and may not use coaxial construction at all. I wouldn't trust smooth cable more than 6 feet. The ones with fine ribs running along the
jacket of the cable generally are
impedance matched and should work reasonably well over longer distances. There may be exceptions to ribbed/smooth, but I haven't encountered it yet. As others have said, 50 feet is a good rule of thumb. Farther if you can live with a little degredation.
Also, keep in mind that
VGA cables are inherently fragile. Kinks, crushes, and mechanical wear and tear can ruin the constant
impedance of the individual coaxes, and will reduce performance. That's why most of these cable are designed to be rather stiff to prevent damage.
Roll and un-roll it gently, limit the amount of handling, and protect it from abuse.
If you have the space for a really fat bundle of cables, you can go much farther without significant loss by using
VGA to
BNC adapters and then running five, RG-59 or RG-6 (75
ohm)
coax cables. The reason is that the bigger the diameter of the
coax, the less loss and roll-off it has. The individual coaxes need to be kept exactly the same length, or the
pixel colors won't
line up (more on
skew in a moment). Where space allows for this bundle of cables, it is probably the best long distance solution. For places where space is limited, such as small conduits, then conversion to Cat-5 is the next best.
Baluns and Cat-5 cable is often a decent solution, especially when the cable has to be small. But, you have to watch out for
skew.
Skew is mis-alignment of the three colors that make up the
image.
Skew is caused by the different length of each of the pairs in the cable, due to different twist rates of the pairs.
Skew becomes a factor as the cable becomes longer.
Skew is worse for Cat-6 cable. Belden and Mohawk make video-specifc, low
skew cable, and there are converter boxes that allow for
skew correction on standard cables. Again, mechanical damage and wear is a big factor with Cat-5 cables. At least they are cheap enough to replace frequently.
