N0GW wrote:
Roy Lewallen wrote:
377 ohms does not describe the E and H fields in the near field. 377
ohms is the ratio of E to H in the *far field* when the medium is free
space or, for practical purposes, air. In the near field, the ratio of E
to H can be not only far from 377 ohms, but it's commonly also complex
(that is, E and H not in time phase). For an illustration, model a short
dipole or small loop with EZNEC or NEC-2, and use the near field
analysis to find E and H at some point close to the antenna (within a
fraction of a wavelength). When you divide E by H, you'll get a wide
variety of results(*) depending on the type of antenna and the
observation point. But as you get farther and farther from *any*
antenna, you'll find that the ratio always converges to 377 ohms, purely
real (that is, the E and H fields in time phase).

Yes, I agree with that completely Roy. I apologize for simplifying my
response so much as to not mention this. I was trying to answer the
question at the same level as was asked. I did not mean to offend the
more mathematically astute members of this group.

I will stand by my comment that radiation from antennas, no matter how
well predicted mathematically, is not well understood at a subatomic
level. I personally prefer a model that assumes photons result from
electron acceleration (or deceleration or energy level decrease).
There are obviously competing models.

I'm not the least bit offended; I just corrected a statement which
wasn't true.

Intelligent discussion of the subatomic and quantum physical aspects of
electromagnetic radiation are for people mathematically much more astute
than I, so I'll leave that for you.

Roy Lewallen, W7EL