Does anyone know about the specifications of the video and sync signals for VGA monitors?
Video: .7 V p-p, (more positive is brighter). Sync: separate horizontal and vertical TTL signals. May be either polarity. “I am trying to send VGA signals over some 180 feet of cable, I’d especially be interested in the required line impedance of the cable.” Line impedance: 75 ohms terminated at both ends. “Is it possible to produce a Composite Sync signal (or maybe even a composite video signal) that could be fed into an off-the-shelf VGA monitor, so I could use only 3 instead of 5 coaxial wires in parallel?” RG59U 75 ohm coax is what is normally used, but you will need a good quality cable to go 180 feet without too much signal degradation. Of course, it also depends on what resolution and thus what video bandwidth you need and how much dispersion (signal delay as a function of frequency) you can tolerate. It is relatively easy to combine the H and V syncs together and then combine these with the video (usually the green signal for ‘sync-on-green’) but most low cost VGA monitors do n
