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Portable/Stealthy 20-Meter Antenna

Discussion in 'Amateur Radio Antennas' started by Riverman71, Sep 12, 2018.

  1. Riverman71

    Riverman71 Part-time Member

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    I am putting together a 20-Meter ground-mounted vertical using a MFJ-1620T hamstick style antenna and four 12.5' wire radials. In the next day or two, I will be posting pics and results. Stay tuned.


     

  2. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    OK I'll ask here: Why 12.5' radials?
    All the Best
    Gary
     
  3. Riverman71

    Riverman71 Part-time Member

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    Gary, I had two 25' rolls of copper wire and simply cut each in half. :whistle::D

    I decided that number (4) and length (12.5') would be worth trying after studying this 2-page document from the gentlemen at Ventenna detailing how they chose the number/length of radials for their HFp 20 meter ground-mounted vertical:

    http://www.ventenna.com/files/Radials.pdf
     
  4. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    OK Jim...go for it...
    However there are several statements in that article...I simply don't agree with, and my experience using ground mounted Vertical antennas, both temporary and long term installs. I do not claim to be a Engineer or know all theory(not even close), just personal experience, for my usage and working on a few commercial installs as an old wire-twister.
    All the Best
    Gary
     
  5. Riverman71

    Riverman71 Part-time Member

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    Got it, Gary. ;) Really doing it because:
    Parts didn't cost much.
    Have time on my hands.
    Weather's getting nice after a HOT summer.
    And I'm in it for the fun.
    Not expecting much and will report back. (y)
     
  6. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Never think I am mocking or dissing anyone for experimentation...To the contrary!!!!... Just going by personal old fashion hands on stuff.
    All the Best
    Gary
     
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  7. Riverman71

    Riverman71 Part-time Member

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    No worries. It's all good. (y)

    Maybe if I double up on the gypsum and watering and spread some BB's around, I can get my soil conductivity up to about 0.030 Siemens/meter and relative permittivity to 20. That should help performance. :D
     
    #7 Riverman71, Sep 13, 2018
    Last edited: Sep 13, 2018
  8. Riverman71

    Riverman71 Part-time Member

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    Okay, here it is.

    Parts:
    MFJ 1620T - $19.95 (from HRO)
    Stud Mount w/SO239 - $5.83 (from Love's)
    90 degree connector - $5.99 (from Love's)
    Simpson Strong Tie BC40Z - $5.78 (from Home Depot)
    25’ Roll 16AWG Stranded Primary Wire (2) - $5.70 ea= $11.40 (from Home Depot)
    Wire Terminals, nuts, bolts, washers – I had these on hand

    Pics: (Click on each for larger image)

    IMG_0326.JPG
    MFJ - 1620T

    IMG_0324.JPG
    Strong Tie with stud mount and connector attached. No bending was required.

    IMG_0325.JPG
    The four radials attached. (The Strong Tie came with 3 pre-drilled holes and rather than break out the drill I simply attached 2 radials to the same terminal.)

    IMG_0327.JPG
    This short piece of 1X4 is used to hold the bracket on the ground. It simply lays across the bottom flange and is secured with bricks. The four bolts attach to the ends of the radials and serve to hold them in place .

    IMG_0328.JPG
    All set up!

    IMG_0330.JPG
    Almost invisible.

    IMG_0331.JPG
    SWR readings after adjusting the length of the steel whip portion of the antenna.
    These were the best I could get, so I called it good. Experimenting with different radial lengths and increasing their number would likely result in better numbers but I'm happy with these.

    IMG_0332.JPG
    Impedance, Resistance, and Reactance.
    Not the best numbers in the world. Nor the worst.

    IMG_0333.JPG
    Patio station.

    Performance:
    Not much activity on 20 meters today but did make one contact to Connecticut (from Texas). Unable to do so QRP. Had to use 50 watts.

    Conclusion:
    It was simple to make. Didn't cost much. Not a worldbeater but it does work. And it was FUN! :D And it's not limited to 20 meters. MFJ makes their 1600T series antennas for all the bands.

    Will this be my go-to base antenna? Nope. Am going to stick with my attic end fed for now. But this antenna will be used when the weather is really nice and I want to get outside to operate. And it will be fun to take camping. (If I can ever get the wife to go.) :ROFLMAO:

    That's all I have for now. Thanks for reading.
     
    #8 Riverman71, Sep 13, 2018
    Last edited: Sep 13, 2018
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  9. Riverman71

    Riverman71 Part-time Member

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    After being on this thing for a while, I can tell you 40 meters is the place to be right now.
    S1 noise level (compared to S3-4 on 20 meters) and operators on 40 are BOOMING in across the band like they are right next door. Too bad I can't hit the PTT! :(
     
    #9 Riverman71, Sep 13, 2018
    Last edited: Sep 13, 2018
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  10. binrat

    binrat WDX Club Coordinator
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    Try elevating the feed point at 6'-8' with the counterpoise as guides with short lengths of rope on ends. It should bring the swr down some
     
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  11. Riverman71

    Riverman71 Part-time Member

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    Thought about doing that with my 12' painter's pole. Ground mounting was just quicker and stealthier.
    Have it put away today as the hot weather has returned.
    Wish fall would hurry and get here! o_O
     
    #11 Riverman71, Sep 14, 2018
    Last edited: Sep 15, 2018
  12. Riverman71

    Riverman71 Part-time Member

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    Here you go, binrat.

    IMG_0392.JPG
    11.5' high with sloping radials.

    IMG_0394.JPG
    SWR went down.

    IMG_0395.JPG
    Efficiency greatly improved.

    (y)(y)(y)(y)(y)
     
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  13. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    GOOD JOB...have fun with that!...Plus you can run FULL POWER:ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO:
    Gary
     
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  14. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    upload_2018-9-15_13-27-1.png

    BY the way 20 meters is OPEN!!!
    All the Best
    Gary
     
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  15. binrat

    binrat WDX Club Coordinator
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    That's where I figured it would be. I think you performance will be better as well. (y)
     
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