50 mhz polarization

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by VE3EKJ, Nov 24, 2020.

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  1. W2EV

    W2EV Ham Member QRZ Page

    The science is clearly outlined (with enough information to allow someone to Google for specifics) in my post above. RF is wonderful magic until one takes the time to see how the "trick" is done. Once you understand the science, everything else falls into place and you can no longer say things like "ymmv". Results are highly predictable...but only if you are willing to both learn and probe enough data points to eliminate variables.
     
  2. VE3EKJ

    VE3EKJ Ham Member QRZ Page

    Thank you all for the replies! I've decided that over the winter I will make a horizontal square loop out of copper pipe. When spring arrives I'll put it up above my second story eavestrough by 4-5 feet, for a total of about 25 feet above ground. Then I might add the 6 metre accessory to my Butternut HF6V to try vertical polarization when the situation calls for it.

    So far I've scrounged a National RJX-610, an MFJ-9406 and yesterday made a deal for a Clegg Venus! (Did I mention I love tube boat anchors?).

    Can't wait until I grow at least one antenna! :)

    Bill VE3EKJ
     
    W2EV likes this.
  3. KE8OKM

    KE8OKM Ham Member QRZ Page

    I’m building a 6m “flower pot” antenna this weekend with some RG8. If you search “SOTA flower pot antenna” you will find a couple designs that are super easy to make. All you need is 10m of coax and a connector. Mine will hopefully work by hoisting it up in the trees with a light line and a weight on the end.
     
  4. W9XMT

    W9XMT Ham Member QRZ Page

    Below is a Longley-Rice analysis of the received h-pol and v-pol VHF fields for point-to-point paths over real, irregular terrain (other things equal).

    In this case there isn't a lot of difference.
    [​IMG]
     
  5. W2EV

    W2EV Ham Member QRZ Page

    Excellent addition to the thread! The result you've posted would (of course) be expected with your well stated "other things equal" included. Man...I need a 300 meter tall structure as used to calculate the plot! Lol.

    Of course in the context of this thread, all things are not equal. When a wave front encounters any non-homoginous, non-infinate dielectric (ionosphere, mountains, buildings, forests, etc.) as encountered in our real world, polarization is no longer assured to be preserved.

    The approach of having both a vertical and horizontal antenna to A/B allows for an operator to select the best "unpreserved" polarization for a given path when encountering ionospheric refraction at HF or object-based diffraction at VHF+. This A/B approach will provide a 3dB variability (because 45-degree polarization is 3 dB down from either) rather than 20dB variability (when fully cross-polarized because of polarization non-preservation).

    The other variable is height. A vertical antenna and horizontal antenna at the same height will have signals radiated at each-others elevation nulls. This will impact the "skip zone" exhibited by each one.

    There is enough basic information contained in this thread to allow an amateur radio operator to web-search more information to allow them to install an antenna (or pair of antennas) to meet their desired goal.
     

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