Signal Loss on a 50ft VGA Cable

Discussion in 'Accessories, Cables, and Remotes' started by Chintak Patel, Apr 30, 2004.

  1. Chintak Patel

    Chintak Patel Auditioning

    Sep 12, 2003
    Likes Received:
    Hello Everyone.

    My Dad just bought a generic $25, 50 ft. VGA extension cord to connect my PC to a Yamaha LPX-500. Surprisingly, everything looks good, even when I up my resolution to 1920x1080 @ 60Hz! I keep my resolution to 1280x720, 60 Hz because that’s what the projector natively supports.

    I was wondering what types of signal loss I should be looking for (loss of brightness, ghosting, etc).

    Here is some more information:

    PC Specs:
    1.7 GHz Pentium 4
    ABIT TH7-RAID motherboard
    512 MB 800MHz RDRAM
    Asus V8200 Deluxe (Geforce3, 64 MB DDR)
    Dual 80 GB Western Digitals on RAID 0
    Sound Blaster Audigy 2
    Generic NIC, 520W PSU, CDRW, DVD, etc

    Video Specs:
    Yamaha LPX-500, approx. 30ft of cabling required from projector to PC
    110 in. Stewart Firehawk screen, approx. 15ft from screen

    Thanks in advance.
  2. Leo Kerr

    Leo Kerr Screenwriter

    May 10, 1999
    Likes Received:
    In our experience in long-haul signal transmission, here are things to look for:

    1. transient rounding - vertical edges start getting a little softer.

    2. smearing - sometimes this is hard to tell from the first.

    3. ghosting/reflections/echos. This is most obvious on those said transients, where there looks like there might be a shadow (slight,) to multiple echos (bad.)

    Brightness should decay in a reasonably linear fashion that correction via brightness and contrast controls will make it go away. It may put more stress on your video card's output stages and may, over time, degrade said output. (You're making the output stage work harder. If you make it work hard enough, it gets unhappy. How hard is hard enough? Your milage may vary.)

    There are two expensive fixes for long-haul video links... something like an Extron P/2 DA2+ UXGA distribution amp (good to 250 feet over good cable,) or a good 'keyboard extender.' We've had some good ones - at least for the 1024x768 displays we were driving - that took keyboard, mouse, serial, sound, and XGA video, massaged it into a CAT-5E cable, and then extracted it at the other end.

    If you're really concerned about long term, consider the following thoughts:

    1. Good VGA cable is not terribly expensive. If you're brave, you can solder your own ends on. Worst case guess: $3-4/foot.

    2. the Extron DA is probably about $400.

    3. The good keyboard extenders I think were in the $600 range, although I may be way off there. I'm a little leery of them because they're doing A-D / D-A conversions on the signal for you... before your projector does another A-D on it. Bad news all around.

    Leo Kerr
    [email protected]

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