Richard:

[snip]
"Richard Clark" wrote in message
...
On Sun, 10 Sep 2006 16:01:34 -0700, Richard Clark
wrote:

In fact, in the near field of an antenna, there is nothing that
resembles 377 Ohms of Z.
[snip]

Correct, but don't we all believe that the wave impedance of "free space" is
approximately 377 Ohms...

Everywhere...

Even in the near field of an antenna.

That is an antenna itself has no effect on the fundamental u and e of the
media in which it is immersed. u and e are defined only in terms of and as
affecting "plane wave" [TEM mode?] propagation, and...

After all the antenna is very small, and free space is very large (grin),
and so a tiny antenna cannot change u and e everywhere!

The fields E and H in the "near region" of an antenna where the waves are
not "plane" on the other hand may not be related by 377 Ohms, simply because
the waves emanating from the "near" antenna are not plane, but...

There might just also be plane waves passing through identically the same
region of space, say emanating from a more distant antenna. The ratio for
those plane E and H fields will indeed be 377 Ohms over the exact same
region of space where Zo is different because of simultaneous but non-planar
waves.

So in fact... the wave impedance of free space can have many values
simultaneously, one [universal?] constant value of ~377 Ohms for plane
waves, while it may have many other [arbitrary] values for waves passing
through the same region of space that are not plane.

Thoughts, comments?

--
Pete K1PO
Indialantic By-the-Sea, FL

The page at:
http://home.comcast.net/~kb7qhc/ante...pole/index.htm
dramatically reveals that the near fields fluctuate wildly from 377
Ohms, and I have restricted my analysis to those values falling at
roughly 100 Ohms or 1000 Ohms (the hot spots marking the feed point
region and the tips of the dipole).

Other antenna design's modification of the 377 near field around them
can be observed at:
http://home.comcast.net/~kb7qhc/ante...elds/index.htm

73's
Richard Clark, KB7QHC