Path: utzoo!utgpu!water!watmath!onfcanim!dave
From: dave@onfcanim.UUCP (Dave Martindale)
Newsgroups: comp.graphics
Subject: Re: RGB (and synch!)
Keywords: How far can it go?
Message-ID: <15558@onfcanim.UUCP>
Date: 29 Feb 88 15:01:24 GMT
References: <557@naucse.UUCP> <196@didsgn.UUCP>
Reply-To: dave@onfcanim.UUCP (Dave Martindale)
Organization: National Film Board / Office national du film, Montreal
Lines: 29

In article <196@didsgn.UUCP> jlc@didsgn.UUCP (jlc) writes:
>
>2) As far as the length of the cable(s) is concerned then it all depends of
>the size and interlace factor of your image.
>as a summary:
>512x512 60hz interlaced		-> 100 meters with good quality cable
>512x512 60hz non interlaced	-> I never tried this one but I would say 50m
>1024x1024 60hz non interlaced	-> 1 pixel <=> 6 nanosec. !!!
>				-> 15 Feet max or you'all have ringing and funny				-> edges
>1024x1024 60hz interlaced	-> I'ld say no more than 50 feet

This is simply not true.  If you use good 75 ohm (NOT 50 ohm!) cable with
properly-applied connectors and terminate the signal properly at the
monitor using either internal or external 75-ohm terminators, you can
run any length of cable you like without developing ringing and "funny
edges" on the monitor, no matter what the resolution of the image.

Make up cables in matched groups of 3 or 4 all the same length, to ensure
that all signals arrive at the far end at the same time.

You will get an overall loss of signal amplitude with distance due to
cable resistance, but normally the monitor's contrast control will take
care of this.  If you have real amplitude problems, you can use video
amplifiers to deal with it, but then the video amp's bandwidth has to match
that of the signal, which may go to 100 MHz.

The whole point of sending signals via a terminated transmission line
is that you can send them a distance that relatively independent of
the signal's wavelength.