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Inverted V Antenna fed with Ladderline

  • 01 Nov 2017 11:37 AM
    Message # 5489879
    Rick Bean (Administrator)

    Chris asked for detail on my home made inverted V antenna. Really easy to make and use.

    For any dipole type antenna remember that it should be 1/2 wavelength long for whatever frequency you will be using. If you feed it with coax then your dipole will be "tuned" for the frequency that you made it for. 

    468/Frequency in Mhz is 1/2 wavelength. so let's say we want to make a dipole for 40 meters and use it in the voice range around 7.2Mhz. 468/7.2=65 feet. So each side of the dipole should be 32.5 feet long. If it is an inverted V, then it will be slightly less depend on the slope. We can feed this in the middle with coax and it will work. To fine tune, you need to use an antenna analyzer, but if you have an internal tuner in your radio you get to an acceptable SWR.

    But what if I want to put up 1 long dipole and be able to tune to more bands? Then we feed with ladder line and use a antenna tuner. The internal tuners probably won't be adequate for this though. The pics below are for my 80 meter inverted V. It is approx 135 feet long end to end. It really doesn't matter as long as it is longer than 1/2 wavelength on the lowest band I want to use. In my case I want to be able to get down to 3.5Mhz so 468/3.5=133.7, close enough. With this I can tune to any band from 10 meter to 80 meters. Because ladder line is 450 ohms and radios like 50 ohms I use a 4-1 Balun and then convert to a short run of coax. Also avoid these lengths of ladder line to avoid harmonics, 66, 135, 190 feet.


    Here are the 2 sides



    Poor mans eye loop



    An insulator made out of plexiglass



    Coiled up ladder line



    I use banana plugs to connect to balun



    4-1 balun with coax output.


    Last modified: 06 Nov 2017 7:31 AM | Rick Bean (Administrator)
  • 13 Nov 2017 7:37 AM
    Reply # 5583949 on 5489879
    Chris Doering (Administrator)

    Rick, thank you for this post. This is the one I'm really interested in building/duplicating. I've seen your results and I like this very much. It also does not take that long to deploy.

    For the time being I'm planning to get a coax (antenna switch) installed in the Jeep so I can easily toggle between the ATAS 120 and a "difference" (second) antenna off the rear. 

    The "difference" antenna I plan on starting with will be this one that you've shown in this post. I should then put my antenna tuner on this line to be able to tune this antenna to the frequency I'm using, right?



  • 13 Nov 2017 8:07 AM
    Reply # 5584004 on 5489879
    Rick Bean (Administrator)

    Yes as long as your tuner can tune high swr not just 3-1 or lower.

  • 14 Nov 2017 8:30 AM
    Reply # 5585843 on 5489879

    Rick;

    I thought a 450 ohm ladder-line required a 9-1 balun?

    450/50=9


    or is it not that simple...

  • 14 Nov 2017 10:58 AM
    Reply # 5586116 on 5489879
    Rick Bean (Administrator)

    Chris asked a similar question this weekend.

    If my wire is around 2-1 swr at 80 meters then 450/2=225

    225/4=56.25, pretty close. Also we are using the same wire to tune all bands so we just need to average it.

    Short answer is I use a 4-1 balun and it works really well.

  • 16 Nov 2017 2:30 PM
    Reply # 5590053 on 5489879
    Chris Doering (Administrator)

    ok, I think I'm starting to get it.

    Thanks for the reply

  • 14 Dec 2017 11:21 AM
    Reply # 5628652 on 5489879
    Chris Doering (Administrator)

    I'm guilty,

    I decided not to go with Ladder line. I went with a fan multiband.

  • 14 Dec 2017 1:18 PM
    Reply # 5628845 on 5489879
    Rick Bean (Administrator)

    Fan dipoles work well also and no tuner needed.

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