Problem's tuning 2 meter beam with gamma-match

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE5HWE, Sep 1, 2013.

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  1. KE5HWE

    KE5HWE Ham Member QRZ Page

    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. WA8ZYT

    WA8ZYT Ham Member QRZ Page

  3. VU2NAN

    VU2NAN Ham Member QRZ Page

    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: Sep 1, 2013
  4. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    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
     
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    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?
     
  6. KE5HWE

    KE5HWE Ham Member QRZ Page

    Thanks, not high enough during test, will try your suggestion..73
     
  7. KE5HWE

    KE5HWE Ham Member QRZ Page

    This is not worth the hassle!! Ordered hy-gain VB214FM for 89.95...Wasted too much time on this.
     
  8. KE5HWE

    KE5HWE Ham Member QRZ Page

    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. K8MHZ

    K8MHZ Ham Member QRZ Page

    That conjures up an interesting mental picture.....

    :cool:
     
  10. WA7PRC

    WA7PRC Premium Subscriber QRZ Page

    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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