Unun: Can it be used on a dipole (balanced) antenna?

Discussion in 'Ham Radio Discussions' started by N8RFY, Jan 27, 2019.

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  1. N8RFY

    N8RFY XML Subscriber QRZ Page

    Can you use an unun on a balanced (dipole) antenna? I'm new to the world of antenna building and the unun diagram I have is so much easier to read than the balun diagram.


    Thanks and 73's,
    Calvin
    N8RFY
     
  2. AA5CT

    AA5CT Ham Member QRZ Page

    Have you tried it without yet? This might be time to try a 'field experiment' or two. Makes for a good learning experiment. You may find out one is not necessary!
     
    N8RFY likes this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Why would you want to do that?

    For coaxial feed and a balanced antenna, a balun is all that should be used. Often, a "choke" balun, which is a form of current balun, is all that's needed and those are really simple: Most of the commercially sold ones for the HF bands are just 50 ferrite cores slipped over the jacket of a piece of coax installed between two connectors.
     
    KA4DPO, WA9UAA and N8RFY like this.
  4. W4NNF

    W4NNF XML Subscriber QRZ Page

    You wouldn't normally need to use an UNUN with a dipole. Commonly, you'd want to use one of these transformers with an end-fed or 1/4 wave (vertical) antenna.
     
    K8PG, K8BZ and N8RFY like this.
  5. N8RFY

    N8RFY XML Subscriber QRZ Page

    Thanks you for your response. No, I haven't. I'm still collecting the materials I need to get started.
     
  6. N8RFY

    N8RFY XML Subscriber QRZ Page

    Thanks for your response. As I stated earlier, the diagram for the unun is much better than the diagram for the balun A link to the antenna I'm working on is below. If you scroll down a little bit, you can see the plans for both the balun and the unun.

    73's
    Calvin

    Oops, here's the link: http://hflink.com/antenna/#BBTDroof
     
  7. W4NNF

    W4NNF XML Subscriber QRZ Page


    Well, that's fine...but the thing is, you shouldn't need an UNUN on a dipole...

    As has been suggested, try your antenna without anything, see what the match is like, and take it from there. Don't put an UNUN in the mix just to be doing something. ;)
     
    N8ZL and N8RFY like this.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The "match" without any kind of balun could be perfect, but that doesn't mean a balun won't help with respect to performance (not matching).

    Even with a great, center-fed, 1/2-wavelength dipole perfectly installed and fed with coax, there's always some i3 current which can be reduced or eliminated. "How much" there is depends on many factors including line length, orientation and where (if at all) the outer conductor of the coax is grounded.

    Checking SWR won't reveal any of that.
     
    KA4DPO, K8BZ, N8ZL and 1 other person like this.
  9. N8RFY

    N8RFY XML Subscriber QRZ Page

    Okay, thanks! I was just trying to follow the instructions. When I get to that point, if I need to put something where it's indicated in the plans, will the unun work?
    Thanks for what you have shared. But, if I need something where it's indicated in the plans will the unun suffice?
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    A unun at the feedpoint of a dipole is inappropriate and will not suffice.
     
    KY5U, KA4DPO, N8ZL and 2 others like this.

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