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Fan dipole questions..

Discussion in 'Amateur Radio Antennas' started by PA770, Jul 15, 2018.

  1. PA770

    PA770 W9WDX Member

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    I have a 1:1 choke about 8' from the rig outside the shack wall.
    IMG_20180715_125040786.jpg

    And then another 18-20' of coax to the current 9:1 un-un to feed my endfed..

    IMG_20180715_125107144.jpg

    What new dipole current balun should I use.to make a fan dipole for 40/20/10m??

    I hear both 1:1 and 4:1, with 1:1 being more mentioned..



    Here is a sample pic of one (not a balun though)

    Screenshot_20180715-125638~2.png
     

  2. sp5it

    sp5it Master of puppets

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  3. 543_Dallas

    543_Dallas Sr. Member

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    1:1 because the resonant antenna will be in the 50 ohm ballpark. A 4:1 would be used to transform 200 ohms to 50 ohms. Your 1:1 choke in the first picture would work fine with some minor modifications. You can make your own by wrapping the coax through a large ferrite core.
     
  4. binrat

    binrat WDX Club Coordinator
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    If I do an inverted V fan, I would ditch the balun, tune to the frequencies I hang out on.
     
  5. PA770

    PA770 W9WDX Member

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    I have no problem buying a new 1:1 so I don't need to move or mod mine..

    Would mine be ok to leave inline??

    Or should i remove and just use a double so-239 to join the coax where the original 1:1 is??
     
  6. 543_Dallas

    543_Dallas Sr. Member

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    You can leave the other 1:1 where it is if you like. I assume it's nothing but a piece of coax and some ferrite in that pvc pipe. All the balun or choke is doing in a coax fed dipole is preventing common mode current on the feed line. A lot of people don't use one but it's good practice.
     
  7. 543_Dallas

    543_Dallas Sr. Member

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    There were a lot of trees in some of the pictures you've posted today. Would it be possible to string up a dipole for 80m out in the woods and run the coax to your house? Coax loss will be pretty low on 80m so a long run isn't a big deal. I have a hard enough time finding my tree stand so a dipole could go unnoticed for a ling time.
     
  8. PA770

    PA770 W9WDX Member

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    Can't. Not my trees. . Mobile home park.. no antennas allowed.. I have 1 tree to play with. Currently the endfed is up at 27' height and then makes a left back to edge of my house at like 13' height.. tied off with insulator.
     
  9. 543_Dallas

    543_Dallas Sr. Member

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    I knew you were in a mobile home park but not sure how wooded the area really was or what you could get away with...or ask forgiveness for later. ;)
     
    PA770 likes this.
  10. JoeDirt

    JoeDirt Well-Known Member

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    I would string some thin gauge wire up in those trees no way anyone would notice! I saw your other thread what tuner do you have?
     
  11. PA770

    PA770 W9WDX Member

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    MFJ-941E

    Other issue is the powerlines that run thru those trees though.. and my neighbors are literally 15-20' behind me.
     
  12. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    The Isolators are supposed to keep your coax feed line from radiating. Ideally it should be within 8 to 20 feet from your antenna feed point. Or that's what I was told.
     
  13. PA770

    PA770 W9WDX Member

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    Should I get the Jetstream with bolts on the side to add and remove terminals?? I would use ring connectors..

    Screenshot_20180716-204448~2.png

    Or the Unadilla W2AU with wires on it??

    Screenshot_20180716-204518~2.png

    I like the bolts on the Jetstream so I can just add and remove the bands as I need vs. unwire and rewire with the Unadilla..

    Which one??
     
  14. binrat

    binrat WDX Club Coordinator
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    If I was going to use 1 ( remember Im anti balun) and needed 1. Jetstream.
     
  15. 543_Dallas

    543_Dallas Sr. Member

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    I know that a lot of people have used dipoles with no cmc choke or installed one and didn't notice a difference. I am curious if you use an amplifier or have ever put a clamp on rf ammeter around the coax to see if you might need one.

    I would do it myself but I don't have coax fed dipole. I did recently make some changes to my balanced tuner for equal current up each leg of the feedline. It eliminated the rfi issues I had and lowered the noise floor. Feedline radiation hurts both ways. 100 watts on 20m used to come across my pc speakers but now legal limit doesn't bother them.

    At first I thought the doublet was longer on 1 side because the right inductor needed one less turn than the left on 20 and 40 but it was exactly the opposite on 15m and up. I'd like to take some readings from the stations that are feeding balanced feedline with a balun on the output of an unbalanced tuner, but that's another topic.
     

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