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Thread: Glue Stick Variable Cap

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  1. #1
    Join Date
    Jan 2009
    Location
    Springfield VA
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    53

    Default Glue Stick Variable Cap

    The March 1 edition of Radio World Newspaper (trade paper for broadcasters) features a great 15-minute project: turning an empty glue stick into a variable capacitor, with a whopping range of 10-12 pf.

    http://www.nxtbook.com/nxtbooks/newb.../index.php#/18

    Maybe not a terribly useful item, but for coming up with it, Frank Hertel (the engineer submitting the tip to RW) is "MacGyver" of the Week in my book.

  2. #2
    Join Date
    Jan 2004
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    Beautiful Downtown Colorado. (Montrose, SW corner)
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    29,214

    Default

    Wonder what it's temco is?

    TOM K8ERV Montrose Colo

  3. #3

    Default

    VJD:

    At VHF and UHF, the capacitance variation range is more than enough to tune the resonant frequency through a fairly large range.

    This capacitor might be a good candidate for a VHF or UHF receiver local oscillator or for a VFO that is multiplied several times to get to the desired frequency.

    Glen, K9STH

  4. #4

    Default

    So simple it's genius.

    I'm sure the basic idea can be manipulated to drive a slug in and out of a close spaced winding on the outside of the tube to make an excellent component to be used in controlling a permeability tuned oscillator

    de VK2HHS
    Last edited by VK2HHS; 03-01-2012 at 11:37 AM. Reason: to make the inarticulate wording even more confusing

  5. #5

    Default

    Quote Originally Posted by VK2HHS View Post
    So simple it's genius.

    I'm sure the basic idea can be manipulated to drive a slug in and out of a close spaced winding on the outside of the tube to make an excellent component to be used in controlling a permeability tuned oscillator

    de VK2HHS

    But as Tom implied above, if the temperature coefficient isn't stable or predictable (and I'd wager different brands and even batches of glue have different characteristics) it's purely an experimental design and would need some careful and rigorous testing before considering such a "device" in any frequency critical or frequency stable use.

  6. #6
    Join Date
    Mar 2003
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    3763 Lyle Avenue, North Pole, AK 99705
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    22,650

    Default

    I maked a PTO with a mechanical pencil and a ferrite bead once. Worked really good too!
    Eric
    "The more you know, the less you don't know."

  7. #7
    Join Date
    Jan 2011
    Location
    Houston Texas
    Posts
    5,145

    Default

    You can also twist two wires together and get the same result.

    It was called a Gimmick (in old school days), and was used for low PF cap needs.

    Stability depends on the type of wire used, and the Cap value is set by the number of twists and length of the wire.


    That is a interesting article. Thanks for sharing.
    "Theory only works perfect in a vacuum." KA9JLM Don

  8. #8

    Default

    Absolutely not new. We have done this with empty lipstick, at least 20 years ago.

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