I haven't been able to find NEC cards or pictures of radiations patterns.

I'm used to seeing them as polar diagrams, however, the only description I've gotten is "[t]he modification of the loop antenna produces a radiation pattern which is orthogonal to the loop." from eh-antenna.com

What is the radiation pattern of a tubular EH antenna like in the picture below?

40m band EH antenna by WB5CXC

(Image from video by WBGCXC)

Bonus: What does the EH stand for?

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    $\begingroup$ NEC and other simulation packages use the regular laws of physics to calculate currents and predict radiation patterns and efficiency, but EH antennas don't work when analysed with these laws. This is also the reason they're found mostly on youtube and not in books. $\endgroup$
    – tomnexus
    Mar 20 '19 at 17:58
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    $\begingroup$ @tomnexus I'm sorry, but since I'm fairly new to the hobby, excuse the surprise: are you telling me this is snake oil?! $\endgroup$ Mar 20 '19 at 18:25
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    $\begingroup$ Bonus answer: E refers to the electric field and H refers to the magnetic field. $\endgroup$ Mar 20 '19 at 19:54
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    $\begingroup$ Note written comment from OM0ET under the cited YouTube video: "This antenna has the problem with a strong returning RF in to coax. This is the reason why I never tryed this antenna in a real outdoor conditions. Until now I did not solved this issue with RF. There is a big problem with resonant frequency instability due to this." $\endgroup$
    – Brian K1LI
    Mar 20 '19 at 21:19
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    $\begingroup$ @AminShahGilani "Is this antenna model ineffective for its purpose?" Inasmuch as one expects the transmission line to convey energy to the antenna for radiation but not to be the radiator, I would say the answer to your question is, "Yes." $\endgroup$
    – Brian K1LI
    Mar 21 '19 at 1:21

Appendix A of, "Crossed-Field” and 'EH' Antennas Including Radiation from the Feed Lines and Reflection from the Earth’s Surface," by Dr Kirk T. McDonald, Professor of Physics at Princeton University, provides a model and some pattern diagrams of an EH antenna. The paper also provides a list of useful references.

The paper concludes that, "As-built EH antennas use arms that are cylindrical sleeves, one of which surrounds the coaxial feedline and provides good capacitive coupling to the outside [of] the outer conductor of the coax. This configuration leads to strong currents on the outside of the feedline, which then acts as the principal radiator of the antenna." Tom Rauch, W8JI, arrives at the same conclusion in his analysis of the E-H Antenna. This subject is discussed, but not resolved, on the web site of EH Antenna Systems.

From my reading of the theoretical basis for the EH antenna, the authors appear to claim that electric and magnetic fields, separately produced by the fringing fields from a capacitor and leakage flux from a solenoidal inductor, respectively, are equivalent to an electromagnetic field produced by accelerating charge. Derivations of antenna radiation in standard antenna texts, e.g., "Antennas" by Kraus, contradict this notion.

  • $\begingroup$ Perfect! I knew that the EH antenna had been debunked and exposed for what it is, but couldn't find these references. $\endgroup$
    – Mike Waters
    Mar 20 '19 at 17:45
  • $\begingroup$ So, in short, it doesn't really have an effective radiation pattern because the EH antenna itself isn't radiating energy, but the coax is? $\endgroup$ Mar 20 '19 at 22:18
  • $\begingroup$ @AminShahGilani That's right. The LC network, together with the length of the transmission line, determines the impedance seen at the driven end of the feedline. $\endgroup$
    – Brian K1LI
    Mar 21 '19 at 1:17
  • $\begingroup$ E stands for Electric field and H stands, perhaps, for Joseph Henry, who discovered that a changing magnetic field induced a current. The two fields make up the electromagnetic wave. $\endgroup$
    – Ted
    Jun 12 '19 at 16:45

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