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LFA Yagi Discussion

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  • Les Rayburn
    I ve been following the articles in DUBUS magazine with great interest concerning the Loop Fed Array Yagi designs of G0KSC. Chief among the advantages cited is
    Message 1 of 2 , Mar 11, 2010
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      I've been following the articles in DUBUS magazine with great interest concerning the Loop Fed Array Yagi designs of G0KSC. Chief among the advantages cited is lower overall noise response, and wide bandwidth.
       
      If true, both these characteristics have real advantages to those of us who operate from urban and suburban environments where local news are perhaps the biggest barrier to working weak stations. My own situation is particularly prone to these problems, with my antenna stack being located inside my attic.
       
      You can read a lot more about this design at:
       
       
      I know that Force 12 is marketing commercial versions of this antenna, but I haven't seen much feedback yet from end-users. I'd love to hear some comments from anyone who's had a chance to evaluate this design or who could comment on it's on air performance. I'm looking at having a couple custom made to fit inside my attic for 2 Meters and 6 Meters.
       
      I'm hoping they might really improve my ability to decode weak signals on the WSJT modes.
       
      Anyone had a chance to try these yet?
       
      73,
       
      Les Rayburn, N1LF
      121 Mayfair Park
      Maylene, AL 35114
      EM63nf
      Grid Bandit #222
      "Listen for the Weak Ones"
       
    • James Duffey
      Les - The low noise advantage quoted for these antennas is due to the low sidelobes in the patttern. They will not do anything to reduce the noise seen by the
      Message 2 of 2 , Mar 11, 2010
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        Les - The low noise advantage quoted for these antennas is due to the low sidelobes in the patttern. They will not do anything to reduce the noise seen by the main lobe of the antenna.

        I am not sure what antennas you are running now, but look at the patterns of your antennas and the patterns of the Loop Fed Yagis and see how much different they are. If the sidelobes on your antenna are substantially greater than the Loop Fed Yagi, you might see some advantage.

        I say might, because the sidelobes of an antenna are affected by materials in their fields, and if close stacked, by the other antennas in the stack. I suspect that the Loop Fed Yagis would perform similarly to the antennas you already have in the environment you have them in.

        The Loop Fed Yagis are not unique in the low sidelobe aspect. YU7EF and DK7ZB have also designed Yagis with low sidelobes and you might find it interesting to compare the patterns of antennas that have the length you are interested in. Although the patterns will be different in details, they all have pretty low sidelobes and good, if not great, front to back.

        Good modern Yagis from many commercial companies are designed to have low sidelobes as well.

        In short, I doubt that you would see significant improvement in signal to noise ratio in going from your current antennas to the new antennas, unless the antennas you have are pretty bad. Going to a longer antenna may help, if you can fit one in it, but if I recall correctly you have pretty much as long an antenna as you can swing.

        The increased bandwidth won't help much, most antennas tuned for the weak signal end of the band are wide enough.

        Let us know how things work out. - Duffey


        --
        KK6MC
        James Duffey
        Cedar Crest NM
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