Hi Jim,
> I read, somewhere in ancient times, that the permitivity and
> permeability of space resulted in an optimum radiation
> impedance for travelling EM waves of 377 ohms: the
> impedance of the "ether".
>
> Now, if so, why are not antenna designs based upon the idea
> that they are really transformers, perhaps azimuth directional
> transformers, who have a job to do. That is, transform the
> energy coming forth from our 50 ohm transmission line
> systems, and efficiently couple said energy into the 377 ohm
> impedance of "space".
Unfortunately this 377 ohm stuff is the source of much voo doo and
pathological science Jim. Claims vary from antennas that synthesize "far
field" making a small antenna very efficient to other equally weird
stupidity.
This "impedance" only describes the ratio of electric to magnetic field in
free space EM radiation. That's true no matter what the source of radiation
is, and there isn't anything to be done about it. Noise from power lines,
light, 160 signals, and even Scowbuger on 11 meters all have the same ratio
in the free-space radiation field. That's true whether the antenna is a
small loop, big loop, long wire, yagi, dipole, or whip or if the source is
a 20 kV 1 mA arc or a 100 ampere .1 volt generator.
Making the induction fields assume a certain ratio and phase at the antenna
means nothing, we still have the antenna region, near field, far field, and
mixtures of all in every system. An antenna can be nearly 100% efficient
and very broad banded with a gross "mismatch to 377 ohms", and nearly zero
percent efficient and very narrow banded with a "perfect match to 377
ohms".
In conclusion, why worry about it? Worry about the antenna loss and loss
around the antenna, not what happens where you can't change it.
73 Tom
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