20metre quarter wave vs Vertical doublet

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by M6KKR, Aug 12, 2021.

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  1. M6KKR

    M6KKR QRZ Member

    Hi

    I have a balanced tuner and plan to build a new vertical for use on 40,20,17,15 and 10.
    I am limited to about 5 meters in height.

    Option 1) is to use a 5 meter scaffold pole with top loading for use on forty meters. Then add radials, Bury coax to fence then add 1;1 balun(if required) and then ladder line back to my atu.

    Other option is to use a 5 meter pole and make a vertical dipole fed with ladder line. My understanding is that with a good Tuner a vertical dipole can be efficient up to 1/8th of a wavelength. (DJOIP website talks of a 12 meter pole being used for a vertical doublet on 80meters)

    In the real world with no salt water included which vertical mentioned here may be more efficient?

    Is there an advantage to ocf or balanced vertical dipoles?
     
  2. W9IQ

    W9IQ Ham Member QRZ Page

    In this case, ladder line will most likely have higher losses than a good coax cable. If you use ladder line, you should select a length that does not present low impedance to your tuner or you may have a quite inefficient antenna system.

    - Glenn W9IQ
     
  3. RW4HFN

    RW4HFN Ham Member QRZ Page

    Friends, this is still a worldwide site... I don't know what is it... :(

    It feels like you didn't have pencils in your childhood... o_O A joke! (36-th min). :D
     
    Last edited: Aug 13, 2021
  4. AA5MT

    AA5MT Ham Member QRZ Page

    I use the MFJ-1796 vertical dipole. It doesn't work well stateside on 20m, but it is outstanding on dx.

    My favorite contact was into Israel one night. The op was on, calling cq before going to work. I was on the computer typing, with him in the background. After about 20 or 30 minutes, I got tired of listening to him. Even more, I got tired of all the replies he was getting. I listened a few minutes, and most of the signals were over +20. A couple were at the limit of my s-meter, about s9+80. There must have been about 20 replies, and he had not answered a single one of them. I knew my dx was good with this antenna, so decided to try it. I turned on the 400 watt amp and replied to him. He came back to me on the first try! He only gave me an S3, but what the heck. I listened afterward, and the band really came alive when 20+ hams replied to him calling cq. I listened for about 20 minutes more, out of curiosity, and he did not answer a single one of them. It made my day.

    From this, I figured the only way to beat the pileup, was because the takeoff angle is around 5 degrees, and all of the power was going into that window. With a beam, most of it is higher angle, about 20 degrees.

    My future vertical will have a variable tilt, which will steer the main lobe directly into the dx window. Most ground mount verticals are between 15 and 45 degrees for the main window.

    Tom
     
  5. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    How long would the ladder line section be, compared to the coax?

    I have made that 12m vertical dipole and used it on 80m. Personally, I wasn't terribly impressed. It worked (not well), bandwidth was tight. I was running ladder line all of the way to the shack, and my vertical was on top of a 5-story building.
     
  6. W9IQ

    W9IQ Ham Member QRZ Page

    If you wish to minimize loss, do not use ladder line on a 1/2 wavelength dipole antenna. Coax will generally have lower loss and less complications.

    - Glenn W9IQ
     
    1 person likes this.
  7. K8JD

    K8JD Ham Member QRZ Page

    A vertical working against ground looks like an unbalanced antenna where ladder line is much more suited to feed a balanced high Z, antenna like a longer than halfwave, center fed dipole. An EDZ is an ideal antenna to feed with balanced line.
    I always had good results with verticals fed with coax.
     
  8. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    Pattern can be wonky on what you want to do.

    If you have a 12m pole, you are much better off (in my opinion) running with a fan dipole like this. I use this portable, and find it works well on 40m, very well on 20m, well on 15m, and acceptable on 17m despite requiring some tuning. You can run coax directly to it. It's nothing more than a fan dipole where the 20m element is vertical, and the 40m is inverted-V. You can also tune and run 10m on that, btw.

    [​IMG]
     

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