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Thread: Problem's tuning 2 meter beam with gamma-match

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  1. #1

    Default Problem's tuning 2 meter beam with gamma-match

    built a 7 element yagi on 3/4 pvc and can't get it tune to a decent swr. made gamma-match with 7in piece of 213 and 7.25" 3/8 copper tube..Not sure if 11in rg 58 would've been better..driven element is no.6 copper with 1/8 in alum. for rest..

  2. #2
    Join Date
    Jun 2011
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    N. Central Florida
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    Build one of these LFA yagis and no matching device needed!

    http://g0ksc.co.uk

  3. #3
    Join Date
    May 2006
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    Quote Originally Posted by KE5HWE View Post
    built a 7 element yagi on 3/4 pvc and can't get it tune to a decent swr. made gamma-match with 7in piece of 213 and 7.25" 3/8 copper tube..Not sure if 11in rg 58 would've been better..driven element is no.6 copper with 1/8 in alum. for rest..
    Hi OM Terry,

    What's the height of the antenna while testing?

    Is it out in the open?

    To keep the antenna from interacting with the ground and surrounding structures, it should located at

    a height of about 12', pointing upwards.

    73,

    Nandu.
    Last edited by VU2NAN; 09-01-2013 at 12:05 PM.

  4. #4
    Join Date
    Jan 2008
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    St. Mary's County Md since 2000
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    If all else fails, put the gamma match in a middle position, and try adjusting the Reflector element spacing.

    I don't know it this is your design or someone else's, but in my experience when using others' they should be built exactly to spec with same materials, sizes, dimensions (at least to start with) since any variation typical causes problems. Best to start with a working known design before experimenting.

    In any case, good luck! bill
    QRZed: "Professional Grade Paranoia From Amateurs"

  5. #5

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    Do you have an antenna analyzer?

    If so, what are the actual readings for R and X?

    I assume based on the descriptions of the materials used this beam is for indoor use. Are you testing it indoors also?
    What if soy milk is just regular milk introducing itself in Spanish?

  6. #6

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    Thanks, not high enough during test, will try your suggestion..73

  7. #7

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    This is not worth the hassle!! Ordered hy-gain VB214FM for 89.95...Wasted too much time on this.

  8. #8

    Default Cheaper to buy vhf yagi than build one!

    Gave up on 2M yagi, wasted too much time and hassle ordered hy-gain yagi, should have done this in the first place!!

  9. #9
    Join Date
    Nov 2004
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    Western Michigan. Great summers but nasty winters.
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    Quote Originally Posted by KE5HWE View Post
    Thanks, not high enough during test, will try your suggestion..73
    That conjures up an interesting mental picture.....

    73
    Mark, K8MHZ

  10. #10

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    Years ago, a friend gave me a 3-el 11m yagi. In a couple of hours, including tuning the Gamma Match, I had 6-el on 2m. My tuning indicator was the relative output meter of my Icom IC22S (better match = more output). For tuning purposes, I had it on a short mast, lashed to a 6' step ladder. That antenna worked VERY well.

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