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10 Meter/6 Meter Parasitic Dipole

Discussion in 'Amateur Radio Antennas' started by Riverman71, Dec 7, 2017.

  1. Riverman71

    Riverman71
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    Two antennas and only one feedline. I like the looks of this but am wondering how well the 6 meter portion works. Can't find any reviews and haven't seen any other antennas using this design.
    Thoughts?



    http://www.freqdev.com/ham/10 Meter and 6 Meter Rotatable Half Wave Dipole Antenna.pdf
     

  2. tba02

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    Technobabble "Fan (parallel) Dipole"?
     
  3. Riverman71

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    Fan dipoles are different because all segments are directly connected to the coax. Right?
     
  4. tba02

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    A fan dipole is multiple resonant dipoles connected to a common feedline. This sounds to me as the same as the one described in the link.

    i.e. I have a 20m/40m fan dipole. This would be a 10m/6m variant.
     
  5. tba02

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    To add - yeah, I guess this isn't directly connected to the coax (hard to tell) and they claim capacitive (lossy?) coupling as opposed to the direct connection.
     
  6. The DB

    The DB
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    I was wondering the same thing so I modeled this antenna from both the 6m and 10m perspectives.

    In these models, the 10 meter antenna is mounted 18 feet above moderate ground, and the 6 meter antenna is a few inches above that. Also, these antennas are made out of T6 aluminum and tuned for low SWR, not resonance.

    For these models I will show the 6 meter antenna info first, and the 10 meter second.

    To start, lets look at the general data.

    [​IMG] [​IMG]

    Here we see that the 6 meter parasitically fed antenna does have more losses due to the aluminum material I used in the model. Of 100% of the power being fed to the antenna, at 6 meters 0.36% of that is being lost compared to 0.1% on the 10 meter antenna from the aluminum being used in the antenna itself.

    However, after things like ground losses are factored in, the 6 meter antenna more than makes up for this difference, with 71.28% of its signal making it to the antenna's far field, while the 10 meter antenna has 63.8% of its signal making it to the far field.

    So, according to modeling, the answer to the questions on efficiency of having a parasitic elements of a different band, their doesn't seem to be a problem with efficiency.

    Next, I'll show the current distribution.

    [​IMG]
    [​IMG]

    One thing to notice here is on the 6 meter model most of the current is flowing on the parasitic element. The parasitic feeding of the 6m antenna is working very well.

    Next the SWR curves for this antenna.

    [​IMG] [​IMG]

    Here we see the parasitic element can be tuned to present a low SWR, however, the 2:1 SWR bandwidth on the 6 meter band is not very wide, in this case covering about half of the 6 meters band. This low SWR point can be adjusted to other parts of the band by adjusting the parasitic antenna length.

    I also want to point out that once you get the parasitic element length for the antenna to show resonance where you want it, you can actually fine tune the R variable at resonance (and by extension SWR) by moving the parasitic element closer or further away from the driven element. Because of this I was able to get the low SWR point of the 6 meters band below that of the 10 meters band.

    Now for the gain.

    [​IMG]

    You have all seen enough of this type of plot, so I will let you draw your own conclusions...


    The DB
     
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  7. Riverman71

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    Have to say I am pleasantly surprised and pleased.
    A much better antenna overall than I was expecting!
    Thanks, DB!
     
  8. tba02

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    And a very interesting overall topic too!
     
  9. Captain Kilowatt

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    There was another thread here somewhere about that same idea. someone was wanting to build such an antenna and someone else posted that same link. the idea is sound and works well. The Hygain Explorer 14 tribander uses a similar driven element configuration and by all accounts the antenna works VERY well. I hope so. I have one to go up in the spring/summer. LOL The EXplorer 14 uses a dual band trapped driven element for 15m and 20m and uses two isolated and parasitic elements spaced about six inches from that for 10m. They use the term open sleeve dipole and it is essentially "shock excited" on 10m from the RF that is fed to the 15/20m element. By using proper lengths and spaces the antenna resonates on 10m just as well as on 15m or 20m. Hygain uses this method on this antenna to increase the efficiency and bandwidth on 15m and 20m because it eliminates another trap (the 10m trap) from the driven element.

    [​IMG]

    http://www.hy-gain.com/Downloads/index.php?productid=EXP-14&filename=EXP-14.pdf&company=hygain
     
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  10. Riverman71

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    LOL. That was me. :D I searched and couldn't find it so posted it again. With better results.
    Good luck with the Explorer! I have confidence in the method now.
     
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  11. HomerBB

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    @The DB
    You are about as handy as a pocket magnifying glass to a 10 year old. :)
     
  12. BJ radionut

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    https://www.arrl.org/files/file/Technology/tis/info/pdf/9510032.pdf

    Here is a Vertical antenna using Parasitic Elements for Muti-band use.
    I know I had seen this before but could not remember where.
    This maybe a Field Day antenna next year be cool to try...
    Plus small foot print and single feedpoint
    All the Best
    Gary
     
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  13. Riverman71

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    Guess parasites are good for something after all. :)
     
  14. wavrider

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    Riverman71 likes this.

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