43' Vertical: 4:1 or 9:1 unun?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WE2CAT, Jun 1, 2021.

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  1. WE2CAT

    WE2CAT XML Subscriber QRZ Page

    I have a 43' vertical mounted in a non standard configuration in that it is elevated. This is my configuration and it will not change so please don't tell me to move it! LOL.

    It came with a 4:1 unun and that is what I am using now a 4:1 unun from Balun Designs. Some posts I have seen regarding the 43' verticals said to use a 9:1 unun. Would this just be magnifying my matching issues? I use a Palstar AT2KD which matches it on all bands but I am always looking to do better.

    Thanks,
    John
     
  2. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    After I posted a question here, I looked at OP's QRZ page and found my answer.
     
    AK5B and AD5HR like this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    Impossible to answer without knowing more about your configuration, especially the height, number, and lengths of your radials. Knowing something about your coax routing, choking and grounding and station-grounding would help, too.
     
  4. WD4ELG

    WD4ELG Ham Member QRZ Page

    John, speaking from experience...

    4:1 or 9:1 unun, I don't think it will make much difference in terms of minimizing losses (which is the goal...get more RF "juice" going out into the ether).

    Here's what I recommend to improve your situation:
    • Use a low-loss coax, short as possible. That will minimize the losses due to the SWR in the coax. LMR-400. Not cheap, but it's what you need to get as much power to the antenna as possible.
    Or
    • Put a tuner at the base of the antenna, or get an automatic remote coupler to work at the base. These aren't cheap either, but you get max power to the antenna and you don't have to worry about SWR losses in the coax. I use an LDG AT-1000 to handle high power....it's located in a shed about 25 feet from the base of the antenna so the losses are minimized (300 feet of coax from shack to the LDG AT-1000 antenna).
     
    AK5B, WA7ARK and KU3X like this.
  5. AK5B

    AK5B Ham Member QRZ Page

  6. KU3X

    KU3X Ham Member QRZ Page

    John,
    You are using a non resonant antenna. On the bands you are using it on, it has a high impedance. All the 4 to 1 or 9 to 1 UnUn does is lower the impedance to make it easier for a tuner to work. The UnUn does not increase the performance of the antenna, whether it's a 4 or 9 to 1. It also does not make the antenna resonant.
    Your transmission line is kind of an impedance transformer in itself since the antenna is not matched.
    If your tuner achieves a good match for your radio to handle, there is no need to change the UnUn. You won't gain anything.
    If you make changes to your antenna, maybe add more radials and / or change your transmission line length, and at that point your tuner no
    longer is able to achieve a reasonable match, then it may be a good idea to change to a 9 to 1 UnUn, only to change the impedance the tuner sees.

    If you do not plan on making any changes and your tuner works for your liking, save your money since there is no need to change the UnUn.

    By the way, as mentioned above, the best thing you can do is to place a matching network at the base of the vertical and add as many ground radials
    as you can.

    Barry, KU3X
     
    Last edited: Jun 1, 2021
    WE2CAT and AK5B like this.
  7. AK5B

    AK5B Ham Member QRZ Page

    Forgot to mention: While i will not tell you to move it (big fan of elevated monopoles already) I will suggest that you change your avatar to a picture including your beautiful cats---it would suit and complement your callsign better---in the opinion of this fellow cat lover.

    73,

    Jeff

    IMG_4470CC.jpg
    Our Flying Mokita
     
    WE2CAT likes this.
  8. KK4OBI

    KK4OBI Ham Member QRZ Page

    Which UnUn?

    If you have an antenna analyzer use common sense to decide. You know the 4:1 ratio gives 50 Ohms to coax at an antenna impedance of 12.5 or 200 Ohms. Likewise the 9:1 ratio gives 50 Ohms to coax at 5.6 or 450 Ohms antenna impedance.

    Sweep the frequencies that you want to operate on and note the various impedances. It should be obvious which ratio gives the better performance for your personal operation with that exact antenna/coax set up.
     
    WE2CAT likes this.
  9. KI8DJ

    KI8DJ Ham Member QRZ Page

    I have a wire antenna about the same length with a 9 to 1 unun. It tunes up on pretty much all the bands with my tuner in my ft 950 which is not a very good tuner.
     
  10. KL7AJ

    KL7AJ Ham Member QRZ Page

    One of each. :)
     

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