(To which Gavin Adams ([email protected]) comments):
In the video industry we had a saying concerning malfunctioning gear:
"If it's broke, hit it with a hammer"
"If that doesn't fix it, paint it and sell it"
My DEC 16" monitor is case in point. Evey once in a while it would lose sync, and smacking it would bring it back (sometimes a few smacks). Recently it gave up the ghost completely, and after the local DEC office gave me a quote of $900 to fix it (Bermuda), I ordered a new Viewsonic 17" for the same price.
I ripped the guts out of the DEC beast, painted it with a marble finish, put plants in it, and sold it! :>
The video signals for red, green, and blue (or just a single signal for monochrome) are sent over cables which are generally 75 ohm transmission lines. These are coaxial cables that may be combined inside a single sheath for VGA, SVGA, MACs, and many workstations but may be separate coaxes with BNC (or other) connectors for other video applications.
Without going into transmission line theory, suffice it to say that to obtain good quality video, the following conditions must be met:
A good quality of cable must be used. This means one in which the characteristic impedance is close to the optimum 75 ohms, one which has low losses, and one which has good shielding. For installations using BNC connectors, a good quality of 100% shielded RG59U is often used. The BNC connectors must be properly installed or they will contribute to mismatch problems.
Where multiple monitors are to be connected to a single video source, all wiring is done in a daisy chain fashion. The only taps permitted are the minimum necessary to connect each monitor to the chain. This usually means a BNC-T connector or a pair of connectors on the monitor for each video signal. T connections with cable must be avoided. (BNC cables only - SVGA monitors cannot be daisy chained without additional hardware.)
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