Here I thought S-Video was good

Discussion in 'Video Hardware' started by Howard S Shubs, Aug 7, 2010.

  1. I decided to try connecting my VCR to my eyeTV with an s-video cable.
    Unfortunately, I don't have an s-video cable, so I looked at the
    connector, thought for a minute, then got an old ADB keyboard cable, and
    hooked it up.

    Geez, that looks like crap.

    So I switched back to composite video, using a cable intended for such.

    It still looks like crap. I think it's the video tape itself.

    --
    May all your good dreams and fine wishes come true! - The Wizard
    May joy be yours all the days of your life! - Phina
    A corollary to the Golden Rule: how a person treats me is exactly how they
    want me to treat them. (remember this the next time you are mugged)
     
    Howard S Shubs, Aug 7, 2010
    #1
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  2. In article <isw-9D8DD7.21081407082010@[216.168.3.50]>,
    isw <> wrote:

    > For a short cable, that'll probably be OK. As the cable length grows,
    > you need to be more careful about impedance matching (S-video cable
    > should be 75 ohms).


    I suppose I could test the impedance with a multimeter... feh, I've
    only got pointy probes. Time to get some clampy probes.


    > But as you realized, starting with VHS, it's pretty much a GIGO
    > situation no matter what sort of interconnect you use.


    Yes. I've got other tapes which look much better. This one looks
    exceptionally bad. So be it.

    --
    May all your good dreams and fine wishes come true! - The Wizard
    May joy be yours all the days of your life! - Phina
    A corollary to the Golden Rule: how a person treats me is exactly how they
    want me to treat them. (remember this the next time you are mugged)
     
    Howard S Shubs, Aug 8, 2010
    #2
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  3. In article <isw-CC991A.11002308082010@[216.168.3.50]>,
    isw <> wrote:

    > Unless you have the world's fanciest multimeter, no, you can't. If you
    > happen to own a time-domain reflectometer, that'd do it, though.


    Hm. I thought resistance and impedance were the same. Guess not.

    --
    May all your good dreams and fine wishes come true! - The Wizard
    May joy be yours all the days of your life! - Phina
    A corollary to the Golden Rule: how a person treats me is exactly how they
    want me to treat them. (remember this the next time you are mugged)
     
    Howard S Shubs, Aug 8, 2010
    #3
  4. In article <isw-A07261.23562908082010@[216.168.3.50]>,
    isw <> wrote:

    > Under certain conditions, transmission lines have a "characteristic
    > impedance", which sort of means that if you had an infinitely long
    > piece, and you hooked your ohmmeter across the open end, it would read
    > in ohms, that value.
    >
    > If the line is shorter than that (and most are), the meter will read the
    > proper value for however long it takes for the signal to get to the
    > other end, bounce off, and return (at more-or-less two nanoseconds per
    > foot of length).
    >
    > So for any length of cable you're likely to have, your meter is just not
    > fast enough. A time-domain reflectometer is basically a very fast
    > responding ohmmeter. Sort of.


    That explains the results I got from the grounding shield.

    --
    May all your good dreams and fine wishes come true! - The Wizard
    May joy be yours all the days of your life! - Phina
    A corollary to the Golden Rule: how a person treats me is exactly how they
    want me to treat them. (remember this the next time you are mugged)
     
    Howard S Shubs, Aug 9, 2010
    #4
  5. Howard S Shubs

    Don Bruder Guest

    In article <2.de>,
    Howard S Shubs <> wrote:

    > In article <isw-9D8DD7.21081407082010@[216.168.3.50]>,
    > isw <> wrote:
    >
    > > For a short cable, that'll probably be OK. As the cable length grows,
    > > you need to be more careful about impedance matching (S-video cable
    > > should be 75 ohms).

    >
    > I suppose I could test the impedance with a multimeter... feh, I've
    > only got pointy probes. Time to get some clampy probes.


    Late to the thread, but FYI/FWIW:

    While both resistance and impedance are measured in ohms, and are
    similar in concept, they are ALMOST NEVER equivalent - a cable rated as
    75 ohms impedance is *EXTREMELY* unlikely to have a conductor resistance
    of 75 ohms.

    Y'see, impedance isn't about the "raw ohms" of the conductors being
    used. It's about "At a frequency between X and Y Hz, the cable behaves
    as if it were a Z ohm resistor". It doesn't matter that the individual
    conductors each show a resistance of 0.026 ohms per foot, or whatever -
    it's the interplay of frequency, conductors, insulation, spacing,
    physical layout, the types of connectors on the ends, and about half a
    metric buttload of other factors that all add up to "this is a cable
    with a Z ohm impedance". As a ferinstance, a nominally "75 ohm" cable
    (common for various flavors of co-ax used in TV work) might be 50, 100,
    or even 1000 ohms if you move outside the usual TV signal range. Strip
    back the braid and hook it up with solder, rather than using the usual
    co-ax connectors, and although the RESISTANCE remains the same (or close
    enough that most meters won't be able to show you the difference) you
    might well find that the IMPEDANCE has changed from 75 ohms to 30 - or
    1000 - or "pick-a-random-number".

    Unless you're blessed with the $$ to buy a very specialized meter (The
    ones that cable TV installers tote around can do it, but I'm told that
    the price tags on those babies would make a decent down-payment on a
    house) it's safe to say that you're a lot better off just going out and
    getting a pre-made cable intended for the purpose - You'll save yourself
    *MUCH* headache.

    --
    Email shown is deceased. If you would like to contact me by email, please
    post something that makes it obvious in this or another group you see me
    posting in with a "how to contact you" address, and I'll get back to you.
     
    Don Bruder, Aug 23, 2010
    #5
  6. In article <i4th5p$j5v$-september.org>,
    Don Bruder <> wrote:

    > Unless you're blessed with the $$ to buy a very specialized meter (The
    > ones that cable TV installers tote around can do it, but I'm told that
    > the price tags on those babies would make a decent down-payment on a
    > house) it's safe to say that you're a lot better off just going out and
    > getting a pre-made cable intended for the purpose - You'll save yourself
    > *MUCH* headache.


    Thanks. At this point, I'm finished. Ran out of tapes worth
    converting, I think.

    --
    May all your good dreams and fine wishes come true! - The Wizard
    May joy be yours all the days of your life! - Phina
     
    Howard S Shubs, Aug 23, 2010
    #6
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