Re: NEC-LIST: Radiation

Hi Ed,

Your statement is correct, that the drift speed of electrons is not
related directly to radiation. Maybe my comment was misleading. I just
wanted to say that their mobility is very limited, so they can never
reach the end of the antenna.

And there is another point which is not quite correct in this simple
model I mentioned: The free electrons in a metal are never in a
position of rest at room temperature.

But I strongly disagree with your "domino" equivalent. Electrons do
not interact in that way. They are not the cause for a wave to
"move". The wave propagates in free space without any charges.
However, electrons are driven by a propagating wave to oscillate, and
they can do this very fast up to the so-called "relaxation frequency"
( I do not recall the correct value in usual metals at the moment,
maybe 10**12 or even 10**15 Hz).

If we talk of perfect conductivity, this relaxation frequency tends to
infinity.
 
As a result of this interaction, oscillating charges are the reason
for a wave to be bounded or guided. The hollow waveguide is a simple
and clear example, where a plane wave can be assumed, bouncing between
the walls, due to the reflection caused by oscillating charges, and
even the fundamental equations can obtained by this simple model.

Regards,

Achim
Received on Mon Feb 21 2000 - 05:57:32 EST