Re: Relativity & Maxwell's EM Theory


Bill Miller wrote:

In "real" antennas (disregarding "long" antennas that are multiples of a
wavelength) radiation is broadside to the conductor and near zero off the
ends. I'm not familiar with the calculation you refer to.

Calculation was done by a friend of mine to get a degree. Basic idea
was to use the TRUE maxwell equations rather than the more usual
simplified ones with near-field terms removed. This produced a
(computer) calculation of the TRUE fields about an antenna. If you do
that, you find the "seems to radiate from the ends" thing. This
doesn't SAY that it actually is radiating from the ends. It just says
that looking at the time-dependent fields about an antenna it APPEARS
to the eye as if that is going on. See P. D. McWane Ohio State
University.

Time Averaged Poynting Vectors (TAPV) can be formed from the results of
commercially available antenna analysis software. The fascinating thing
about such an anlaysis is that the TAPV flows smoothly from the source to
the antenna and thence to the rest of the world.

OF course the thing with practical commercial antenna software is that
one is only interested in the far field. Which is OK. But if you try
to extrapolate that back to the antenna mistaken impressions occur.

And THAT seems to imply that the antenna doesn't radiate anything. Its
function is merely to "guide" or "facilitate" radiation. But I have yet to
see a sensible description of the mechanism that causes the TAPV to stop
"hugging" the conductor and neatly turn and bop off into the aether --
whatever THAT is!

Of course the "impedance" transformer function of an antenna (from
transmission line to free space) is there. Horns and other impedance
transformers seem to show such an operation underway. But as you note,
there is little understanding of how the transition is made from the
end of the "transformer" to the impedance of free space. And one
thing we DO know about "aether" is that it has impedance to EM waves.
The Interesting thing about EM is that there are often widely
different "explanations" and BOTH can often give the correct answer!
The problem with this is that if one is trying to think of a "model"
for what is going on, now you have several models and they all work!

Generally, balls on the end of an antenna seem most useful in reducing or
eliminating corona discharge -- an important issue at higher power levels.
They seem to have little or nothing to do with the function of radiating
signals.

Sort of correct. Hertz used the "balls" only as spark gaps and were
his "detector". The balls only allowed a calibration of the spark gap
voltages.

Unless your last name is Tesla, of course.

Of course the large spheres of the Tesla wireless power transmission
systems were to create a CAPACITANCE to the sky as well as to reduce
corona at the monster voltages.

Benj

.

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