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Vertical yagi without mast and coax interference

Discussion in 'Amateur Radio Antennas' started by davev8, Feb 19, 2018.

  1. davev8

    davev8 Gold Star/Marvin Award Member

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    Ok i would like to run a vertical 10or11 (taking foundation soon) meter 4 element yagi but i understand they are not that successful as the mast and coax upsets the pattern i can get a fiberglass pole but that leaves the coax ...i was thinking on a home brew antenna i can make the elements thicker and run the coax inside say the director and choke the coax when it emerges from the tube ..i know the elements will end up a little shorter being thicker ...but will the concept work? ..i have not seen it done before


     

  2. 543_Dallas

    543_Dallas Sr. Member

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    Put it up and talk on it. I'm not saying there isn't an interaction but a lot of people have vertical beams on normal masts that work fine. This is a good time to use the K.I.S.S. rule.
     
  3. davev8

    davev8 Gold Star/Marvin Award Member

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    yes i like to KISS but swapping out a metal mask and making a choke is not deviating to much
    it depends what your interpretation of working fine is ..
    although i was not personally involved i know 2 guys back in the day that play with vertical beams and find that two 4 element beams flat side to flat side worked very well but not so good both vertical ..then they try Avanti PDLii quads that are switchable from vertical to horizontal the 4 element beams on the flat side was better than the PDLii but the PDLii was much better than the beam when vertical so the difference between a beam on the flat side and vertical is a lot
     
  4. HomerBB

    HomerBB Sr. Member

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    I think the choke would better serve you immediately after the feedpoint on the driven element. Unless you have a Common Mode Current issue coax is designed to be near conducting materials without suffering interaction problems.
    As for the mast interacting, very likely it will affect the pattern somewhat, but not necessarily to a great degree.

    Others can correct me, but first of all, the mast length will not likely be a resonant length so the signal will pretty much ignore it. Second, put up your yagi on the mast and tune it with the mast present.

    I once built a 2 element quad beam using metal spreaders except for the last 18" or so near the wire elements. Worked just fine. Screenshot_20180220-205259-01.jpeg
     
    ShadeTreeMechanic likes this.

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