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Old March 6th 15, 11:02 PM posted to uk.radio.amateur,rec.radio.amateur.antenna
Spike[_3_] Spike[_3_] is offline
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First recorded activity by RadioBanter: Feb 2014
Posts: 180
Default E/M radiation from a short vertical aerial


Imagine a short rod vertical aerial not connected to ground, for the
(say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed
with RF energy and operating over ground of average conductivity.

Three different waves will be launched from this: the sky wave, the
space wave (including the reflected ray), and the surface wave. Each of
these have their own characteristics, inasmuch as the sky wave is
launched willy-nilly even if the band isn't open for that mode, the
space wave depends on the path to the receiver, and the surface wave
depends on the electromagnetic characteristics of the air and the
surface material, although to some extent the latter affects all the
waves generated.

My question is: since all these result from the emission of RF from the
short rod antenna, what proportions of the total RF power supplied to it
are found in each of these three separate waves, and what factors
control these proportions?

--
Spike

"Hard cases, it has frequently been observed, are apt to introduce bad
law". Judge Rolfe