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VGA Monitor Cable

Discussion in 'Electronic Design' started by Cliff, Oct 29, 2003.

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  1. Cliff

    Cliff Guest

    Don't ask me why, but I need to build a 1" VGA monitor cable to connect a
    very small motherboard to a fairly small LCD screen. The distance between
    the motherboard and the monitor VGA connectors is around ½ "

    My fist thought was to go out, get the connectors and some cables and solder
    a cable form pin 1 to pin 1, 2 to 2, 3 to 3 etc. but before I even got to
    that part I notice that my current VGA cables have some kind of cylinder
    component right before both ends of the VGA connectors.
    http://www.l-com.com/jump.jsp?lGen=...=35&iSubCat=120&iSubSubCat=121&iProductID=201


    What are these ugly things??? Even a more stupid question, can I just remove
    them???

    Thank you.
     
  2. CFoley1064

    CFoley1064 Guest

    Don't ask me why, but I need to build a 1" VGA monitor cable to connect a
    A while back I had to put a mini-tower PC in a NEMA box on a machine, and built
    a 5" adapter to do just what you're talking about (having the monitor connect
    to the back of the NEMA box, and using the adapter to connect the back of the
    NEMA box to the PC). No ill effects. Any longer than a few inches, though,
    and you'll probably have signal problems.

    Good luck.
    Chris
     
  3. They're ferrite beads; they serve to reduce transmitted RF interference; and
    for the purposes of your 1" long cable, you can remove them.

    (Of course, if you are manufacturing and selling this device, you'll have to
    subject yourself to EMI testing either way.)
     
  4. Chaos Master

    Chaos Master Guest

    I found ancient runes from Cliff[] in the floor of
    sci.electronics.design:

    They're ferrite beads to avoid RF problems. For a very small cable, they're not
    needed.
     
  5. Cliff

    Cliff Guest

    They're ferrite beads; they serve to reduce transmitted RF interference;
    and

    Got it, but I am still kind of confused on why some other long cables such
    as Ethernet cables that soemtimes are 50 times longer than a VGA cable do
    not have ferrite beads??? Aren't this cables acting like antennas too?



    Just curios.
     
  6. Ethernet (and its current variants such as 100Base/T) was designed as a
    transmission standard. So, signal rise and fall times and cable
    construction are controlled to minimize unintended radiation or reception.
    For instance, twisted pairs, in which current flowing one way tends to
    cancel current flowing the other way.

    VGA cables are just a bunch of wires, carrying very-high-frequency signals.
    RFI galore.

    Eventually things will probably switch to some other means of communication
    between the bus, video card, and monitor - like, and I'm just speculating,
    serial ATA from bus to card, with the card built into the monitor rather
    than into the PC.
     
  7. Gary Tait

    Gary Tait Guest

    Right now there is DVI, which is differential, like Ethernet is.
     
  8. Mac

    Mac Guest

    Ethernet uses differential signalling over twisted pair cable, which helps
    a lot. In addition, the transmit side is usually passed through a common
    mode choke and isolation transformer on the board of origin. The common
    mode choke in ethernet serves the same purpose as the ferrite on the VGA
    cable. All of this together helps tremendously, both with Electromagnetic
    Compliance (EMC) and suseptibility to EM Interference (EMI).

    Mac
    --
     
  9. Chaos Master

    Chaos Master Guest

    I found ancient runes from Cliff[] in the floor of
    sci.electronics.design:
    Because the Ethernet cables have a standard. With controlled signal
    rise/falltimes. Ex. Twisted pairs.

    VGA cables are just a lot of wires carrying very high-frequency signals.
    RFI anyone?
     
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