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diy full wave 11 meter loop antenna question

Discussion in 'Home Brew' started by Mudduckmobile, Sep 29, 2016.

  1. Mudduckmobile

    Mudduckmobile Well-Known Member

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    I want to build a "Bambi" or full wave loop antenna with 27.38500 as my center of the band.
    I read on some sites that I DO NOT need a feed point Transformer.
    I read on most sites that I DO NEED a feed point Transformer. I can buy a 75 ohm coax and cut, solder to antenna then put on my connecter to which my 50 ohm coax runs to my rig( FT450D).
    I know I need to use 1005/27.385= 110.097in. or 9.175ft. or279.646cm. of 14g wire (pvc covered).
    I just dont get how this antenna can work right WITH OUT a Transformer?
    I do know if I can put it up and not need a Transformer it will make for less work.....


     

  2. vkrules

    vkrules Sr. Member

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    Definitely needs the transformer.( it's about 120 ohm feedpoint impedance) Unless you make it a rectangle and feed it on the short side( then it's 50 ohm). Also you get a little bit more gain with the rectangle.
     
    #2 vkrules, Sep 29, 2016
    Last edited: Sep 29, 2016
  3. Mudduckmobile

    Mudduckmobile Well-Known Member

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    Thank you.
    I may just lay it on the ground in a loop. I may put it up 25-30ft. on a fishing pole. Or lay it on the roof of my home. I just did not get the no transformer thing.
    You say if I make a Rectangle I do not need a Transformer, is there a site you can give me for an out line? And do you think it best to make a Transformer from 75 ohm coax or to buy a store bought Trans.?
     
  4. vkrules

    vkrules Sr. Member

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    antenna LOOP 10M.jpg
     
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  5. Mudduckmobile

    Mudduckmobile Well-Known Member

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    So it looks like a 2 to 1 ratio for the Rectangle.....
     
  6. vkrules

    vkrules Sr. Member

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    Easy enough to make the 75 Ohm transformer .just remember that the length is 1/4 wave x velocity factor . It will be around 72 to 78 inches depending on type of cable you use. I use a GDO or analyzer to find the length, but as long as you can find the VF, measurements are close enough (nearest inch is close enough). Yes the 2 to 1 ratio is the Money and again you dont have to be perfect.
     
  7. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    http://www.w5sdc.net/delta_loop_for_hf.htm

    I use delta lops from 10 meter through 20 meters and they do work as described, 4:1 balun at feed point and 50 ohm coax to shack
     
    Mudduckmobile and 222DBFL like this.
  8. 222DBFL

    222DBFL Sr. Member

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    Thx for that link Wavrider!! Good read and gave me some good ideas!!! Much appreciated. May build one of these instead of a SWL long wire!! Again, thx for the link. It's added to my bookmarks!! Hope all is well up your way. Had some decent conditions yesterday and was the first time in a while I got on and talked to some of my radio friends. Anyhow. Have a great day and stay well my friend.
    Sean.
     
  9. Mudduckmobile

    Mudduckmobile Well-Known Member

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    Thank you!
    quick up date. I have worked out 6.1166ft. x 12.2333ft. i will use 14g and will order 75ohm coax from dx eng. w/ctr at 1/4 wave vf.
     
    #9 Mudduckmobile, Sep 29, 2016
    Last edited: Sep 29, 2016
  10. Robb

    Robb Yup

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    AND using 450 ohm feeder to the loop - too?
    Feeding the loop - at which corner?
     
  11. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    robb depends on what polarization you want to use, the article/link shows how to feed it for different polarizations
     
  12. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Mudduckmobile likes this.
  13. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    222DBFL thanks for the kind words, all is good, just long hours at work and not much time to play, speck season is coming so I busy on weekends playing with the boat on the lakes around here, hope all is good with you and family.
     
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  14. 222DBFL

    222DBFL Sr. Member

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    All is good here as well as it can be!! Working my reat off as well. Have fun catching some SLABS!! Been a while since I been speck fishin, but man is it fun!! Good luck and be safe on the water!!
     
    wavrider likes this.
  15. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Hey ROBB, finally got some time off from the work.

    I feed mine at the bottom in an upside down triangle configuration.

    If you one use an antenna coupler ( tuner) then feed it with ladderline to minimize losses with impedance mismatches.
     

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