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60m vee in a 40m space

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KP4SX, Jan 4, 2020.

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  1. KP4SX

    KP4SX Premium Subscriber QRZ Page

    I have a 40m inverted vee which I don't regularly use and would like to re-do it for 60m.
    I cannot extend it any further and there's really no way to dangle an extra 11ft off each end.
    How do I go about calculating how much loading coil I could add to each leg (and where) to 'shorten' it to fit my space?
     
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    The easy way is to use an online calculator like this one: http://www.66pacific.com/calculators/coil-shortened-dipole-antenna-calculator.aspx

    It calculates loading coil values vs position, frequency and overall wire length for flat top dipoles so there will likely be a bit more field tuning in your inverted-V configuration but as you know you pretty much have to field tune any antenna in its installed location so it really doesn't change much.

    It would be easy to model variations of your loaded V as well but the calculator is probably quicker and lets you see things like tradeoffs between coil location and necessary loading inductance pretty quickly.
     
  3. K7JEM

    K7JEM Ham Member QRZ Page

    I found this calculator online. You just have to tell it the parameters:
    http://www.66pacific.com/calculators/coil-shortened-dipole-antenna-calculator.aspx
     
  4. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Thanks guys. I'll work with that one.
     
  5. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Well, that was too easy.
    What benefits are there in spacing the loading coil further in or out? I arbitrarily selected 16 ft out on each side.
     
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    - Closer to the feed point and you need less loading inductance for the same total wire length
    - Further from the feed point, the loading inductance goes up but overall antenna efficiency increases due to lower coil losses
    - About halfway out the antenna is the best from an antenna efficiency standpoint as long as the required loading inductance isn't excessive. Small variations from that aren't a big deal but it's usually better to place the coils somewhere from 1/3 to halfway out each radiator for best overall antenna efficiency.
     
    N0TZU, AJ5J and WB5YUZ like this.
  7. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Got it.
     
  8. WA7ARK

    WA7ARK Ham Member QRZ Page

    I have an AutoEz parametric model for a coil-loaded inverted V. Here are the parameters that describe my guess at your antenna:
    par.png

    I used the AutoEz optimizer to find the required loading coil inductance of 12.4uH. I guessed that the leg lengths were originally L=33.2ft with a down angle of 30degrees. If you can refine my guesses for H, L, or A, I will rerun the optimization for you.
     

    Attached Files:

    K0UO, KP4SX and AJ5J like this.
  9. KI8DJ

    KI8DJ Ham Member QRZ Page

    I would go with the 16 feet from center the coils will act like traps and give you a 20/60 dipole.
     
    K0UO likes this.
  10. KH6AQ

    KH6AQ Ham Member QRZ Page

    Hypower antenna company makes shortened 60 meter dipoles and the loading coils are available, $20 a pair.
     

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