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gamma match insulating materials

Discussion in 'Home Brew' started by BOOTY MONSTER, Apr 23, 2011.

  1. trying to get a idea on the options i can use for insulating between the rod and tube on a gamma match . i know it has to be non-conductive to RF . the only way i can check that is doing the microwave trick . not the best way , but from what i understand is a good enough indicator for home-brewing .



    ATM im thinking heat shrink tubing would be a easier way to keep the layering consistent on the rod compared to wrapping it in teflon plumbers tape . plus the friction from it shrinking should hold it in place compared to having to tape or glue the teflon tape to keep it on . im gonna use 3/8 inch diameter solid aluminum rod and 1/2 inch inside diameter aluminum tube . 200 watts is the most i PEP (if i hit a small lottery i would bump up to an AL-80B...LOL) . i also want to use heat shrink over the shoulder where the rod exits out the top of the tube to keep moisture from running in , as well as on a few other sections .

    is the heat shrink tubing a decent material for this use ? or will it cause issues ?
    what would you suggest instead ?
     

  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I did use heat shrink on a gamma match but it ran no more than 75-100 watts pep. I would suggest some nylon ( preferably) or pvc tubing like that used in aquariums. The voltage won't be high at the feedpoint but the RF current will be at it's maximum however at the power you state it shouldn't be a big deal.
     
  3. mackmobile43

    mackmobile43 Jock Supporter

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    use the insulating portion from rg-8 coax.
     
  4. W5LZ

    W5LZ Crotchety Old Bastard

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    The only addition I'd make to 'Mack's is to not use the 'foam' type dielectric insulation, use the 'solid' stuff. Lasts longer and water/sun won't affect it like with the foam.
    - 'Doc
     
  5. unit_399

    unit_399 EL CAPO

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  6. mackmobile43

    mackmobile43 Jock Supporter

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    I got the idea from my wolf .64 gp, Eddie Chicone used the foam dielectric his his gamma matches and he had a 5000 watt upgrade on that which I suspect was either teflon or the the clear poly stuff:D
     
  7. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I tend to agree with 'Doc and Mack that Wolf uses 3/8" foam inside the 1/2" tubing for his gamma. This may account for why I saw the match go bad for a period of time as some point. I think Mack is also right when he suggested that the top end of Eddie C's gamma was left open to allow rain in and that likely saturated the dialectric and shorted until it dried. I placed a cap on mine, and that should help prevent this from happening again.

    However BM, I don't think the 1/4" insulator inside of RG8 will be large enough for a 1/2" gamma, unless you make all of the gamma elements smaller.

    I figure a gamma should have insulating material that is at least as effective at handling current/voltage as the coax used.
     

  8. coax wont work for the gamma that i need . ^^^^^
    it needs to be stiff enough for over 2 feet to stay vertical/straight on its own .

    i already have 3/8 solid aluminum rod
     
  9. mackmobile43

    mackmobile43 Jock Supporter

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    That's some monster rod there booty, are you gonna be putting like 10kw through it? if not you could get by with 1/8 or 1/4'' rod and a 3/8ths tubing and still have a 1 kw capacity.

    Just bang the rod end flat a bit and drill a hole through for connections.
     
  10. JoeDirt

    JoeDirt Well-Known Member

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    Teflon is the best but its cost more, Delrin is pretty good and fairly cheap.
     
  11. awwwwwwwwww............. you're gonna make me blush . ;)


    ive already got the 3/8 rod and i can get the tube for 3 bucks .... so i figgure .... why not ? ;)
     
  12. mackmobile43

    mackmobile43 Jock Supporter

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    baw haw haw b00ty monster rod

    So you're going with 1/2'' tube or 3/4''?
     
  13. GnG8d

    GnG8d Well-Known Member

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    LINK

    Link won't come up right. Virgin teflon tube for $4.40/ft., 1/2"OD x 3/8"ID.
     
  14. 1/2 inch inside diameter . im gonna use one of the ground elements off of this for the rod .
    thanks 359 :)
    [​IMG]
     
  15. GnG8d

    GnG8d Well-Known Member

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    They have it in phenolic too, called Garolite.
     

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