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From: cetron@UTAH-CED.ARPA (Ed Cetron)
Newsgroups: mod.computers.vax
Subject: Re:  Cable Length for stationII GPX
Message-ID: <8610130136.AA02716@utah-ced.ARPA>
Date: Sun, 12-Oct-86 21:36:17 EDT
Article-I.D.: utah-ced.8610130136.AA02716
Posted: Sun Oct 12 21:36:17 1986
Date-Received: Mon, 13-Oct-86 03:07:35 EDT
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we did it, but not very well apparently.... we have a MVII in out computer
room and the GPX (installed as an add-on upgrade) in another room about 33-34
feet ('bout 10 meters) away....the technique we used:

	1. build a DB15 plug the attaches to the VCB02 connector plate (the one
which is on the MVII distribution panel)....

	2. have the digital lines (for the mouse/tablet and the keyboard)
go through a standard 9 line cable (since they are only rs232c anyway...) 
	READ THE MANUAL SO THAT IF YOU USE TWISTED PAIR CABLE, YOU DON'T
	PAIR UP MOUSE AND KEYBOARD LINES - (we forgot this and got some
	very wierd cross-talk)

	3. Using as large a guage and as short as possible, connect the
video lines to RG-79 (??) coax cable (I am at a loss for the number, but
specify it as 75 ohm coax.....the normal black coax with BNC connectors
is only 50 ohms) this cable might need to be special ordered.....

	4. run the cables (4 - 3 video, 1 digital) to the VR2xx monitor and
attach the video cables DIRECTLY to the monitor by installing BNC connectors
onto it....

	5. build an DB-15 connector and plug the supplied cable into it and
then the mouse/tablet and keyboard into the DEC cable....

	6. Caveats:  careful with the RS232c cable pairing...
		also, the coax might require some impedance matching
		it seems that 2 or our cables worked well, but the red is
		ghosting for some reason.....I think a little rc network
		and we will have that solved...

good luck,

-ed
Center for Engineering Design
Univ of Utah
cetron%utah-ced@utah-cs.arpa