Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!mailrus!tut.cis.ohio-state.edu!ucbvax!husc6!rice!sun-spots-request From: razzell@vision.cs.ubc.ca (Dan Razzell) Newsgroups: comp.sys.sun Subject: Re: Extended Monitor Cables info needed Keywords: Hardware Message-ID: <788@brazos.Rice.edu> Date: 8 Aug 89 17:45:00 GMT Sender: root@rice.edu Organization: Sun-Spots Lines: 86 Approved: Sun-Spots@rice.edu X-Sun-Spots-Digest: Volume 8, Issue 95, message 2 of 11 In article <34@brazos.Rice.edu> Stephen Miller writes: >X-Sun-Spots-Digest: Volume 8, Issue 63, message 9 of 14 > >I am going to purchase an 100 foot cable which will allow me to place my >Sun 3/260 in the computer room, while locating the monitor an office area. In article <286@brazos.Rice.edu> Paul Allen writes: > > I have the high-res mono monitors of four 3/280's located on the ends > of 50-foot cables. Someone (perhaps my local field engineer) gave me > a description of Sun's monitor and keyboard cables and I had a local > cable-maker build 50-foot duplicates. We've been running this way for > over 6 months. The keyboards work fine, but there's noticeable > horizontal smearing on the monitors. Switching to a bold font helps. > For the price we paid, I'm fairly satisfied, but I'm not sure I'd do > it again. For the past year or so I have been gathering and testing various bits of wisdom on the subject of Sun monitor cabling from Sun Spots and elsewhere. The arrangement I will describe below works perfectly for us with Sun's high res monitors at fifty feet, and would probably work at 100, at least I can say so for our particular keyboard cable. The horizontal smearing problem that Paul Allen describes is probably caused by a bad impedance match in the cable. Check the specs on the cable to be absolutely sure it's rated at 75 ohms. If that is okay then I can only think the problem is inductive. If so, it should get worse if the cable is coiled, so you might try that to see what happens. The Sun monitor cable has a differential video signal as well as horizontal and vertical retrace. Phil OKunewick claims success using twisted pair for the differential signal, but the Belden 8777 shielded twisted pair I used had the wrong impedance and did in fact cause smearing anyway. I think one of his arguments against coax was not to carry one of the video signals on the shield, and of course that makes sense, so if you do use coax you need to put the signals inside. I don't understand how he avoided the impedance problem if he really used plain twisted pair, but there is a cheap solution if it works. I'll just mention that for the time when we were using the wrong cable, we lived with the smearing by making the background raster on the screen a random dot pattern rather than the usual checkered texture. That keeps down the resonance at high frequencies. VIDEO CABLE Use any 4 x 75 ohm coax, 22 ga stranded works fine at 50 feet, probably more. We used Comprehensive Video CVC-RGBS, which puts four cables in one jacket. DB-9 connectors. Pin Signal (From Sun Hardware Installation Manual) --- ------ 1 video + 2 3 H sync 4 V sync 5 6 video - 7 ground 8 ground 9 ground KEYBOARD CABLE We used Belden 8458, 22 ga stranded works fine at 100 feet. DB-15 connectors. Pin Signal (From Sun Hardware Installation Manual) --- ------ 1 recv kbd 2 ground 3 trans kbd 4 ground 5 recv mouse 6 ground 7 trans mouse 8 ground 9 ground 10 power 11 power 12 power 13 power 14 power 15 power