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Roy Lewallen · April 30th 10, 10:06 PM posted to rec.radio.amateur.antenna

wrote:
On Fri, 30 Apr 2010 05:12:38 -0700 (PDT), Cecil Moore
wrote:

On Apr 30, 4:14 am, "Peter" wrote:
I know this group has some expertise on this subject and would appreciate
any constructive comment and suggestions regarding the attached article.
The two-dimensional Fig. 2-2 graph is confusing in that it could be
inferred that the E and H fields are 90 degrees out of phase in time
and are never zero at the same time. The E and H fields are in phase
in time as demonstrated by Fig. 2-4.
Hmmm. I'm no expert, but I thought they were 90 degrees out of phase.
It's the rapidly changing H field that creates the E field and vica
versa. If you look closely, Fig 2-4 also shows them 90 degrees out of
phase.
. . .

The time phase angle between E and H is determined by the medium the
wave is propagating through. The (complex) ratio of E to H is called the
intrinsic impedance of the medium, and for lossless media, it's always a
purely real number (about 377 ohms for air or free space), meaning that
E and H are in phase. Only when propagating through a lossy medium are E
and H not in time phase, and then the maximum phase difference is always
less than 45 degrees.

In any version of EZNEC including the demo, you can see the value of the
intrinsic impedance of nearly any medium. Select a real ground type,
click Ground Descrip in the main window, and enter the conductivity and
dielectric constant of the medium. (To simulate free space, enter a very
small number for ground conductivity, and 1 for the dielectric
constant.) Then open the Utilities menu and select Ground Info. Among
other things, it shows the intrinsic impedance of the ground medium in
polar form. The angle of the impedance is the time phase angle between E
and H of a wave propagating in the medium.

Roy Lewallen, W7EL

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