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A rather popular belief on this topic is that h-pol is superior to v-pol. Probably that is traceable to published "far-field" patterns over a lossy ground plane generated by Method of Moments software such as NEC (Numerical Electromagnetics Code). This post is a deeper dive into the topic.

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    $\begingroup$ Would the downvoter please explain why? $\endgroup$
    – rclocher3
    Jul 20, 2020 at 14:10

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As clearly shown in the graphic clip first below, h-pol e-m waves radiated at low elevation angles tend to be canceled by their reflections from the Earth near the antenna site. Note the last sentence in the text column at the right side of that graphic. (This clip is taken from a textbook printed in the 1940s, but Physics hasn't changed in the interim.)

The graphic second below shows a NEC4.2 comparison of the E-fields existing over a zero to 45° elevation sector, 0.1 km downrange from an h-pol and v-pol radiator both radiating 100 watts. (Note that an h-distance of 0.1 km from these radiators lies well within their far field.)

The reduced fields from the h-pol radiator are clearly evident.

enter image description here

enter image description here

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    $\begingroup$ Downvoting a question without explaining why that was done doesn't advance the knowledge that could be gained by the author of the question, or its readers. Neither does it encourage the continued participation of that author in this Forum. $\endgroup$ Jul 19, 2020 at 10:25
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    $\begingroup$ What does the horizontal axis of the NEC4.2 plot represent, and what are its units please? $\endgroup$
    – rclocher3
    Jul 20, 2020 at 14:25
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    $\begingroup$ It shows the value of the E-field at those "Z" elevations above the Earth, at a distance of 0.1 km. For example, the E-field from the vertical monopole at an elevation of 40m AGL and a range of 0.1 km from the antenna is ~ 406 mV/m. $\endgroup$ Jul 20, 2020 at 19:26
  • $\begingroup$ Your NEC4 graph says E(theta) on the top left, but for an Hpol source you want E(phi). Or are the red and blue graphs each for different field components? $\endgroup$
    – tomnexus
    Dec 15, 2020 at 16:35
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I think frequency band and application need to be considered as a context.

  • Satellite signals get randomly repolarized as they travel through the ionosphere, so I don't believe there is any advantage to one orthogonal polarization over another (e.g. horizontal vs. vertical, right-hand circular vs. left-hand circular, etc.)

  • UHF and higher radio waves in urban areas are subject to extreme multipath scattering that also tends to randomize polarization.

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