On 3/6/2015 6:02 PM, Spike wrote:

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?


That depends entirely on the radiation pattern of the antenna. For
instance, the sky wave will be that part of the pattern which has fairly
high angle of radiation (but lower than the space wave), and the surface
wave will have a very low angle of radiation.

All of them depend on the characteristics of the antenna, the ground
system, the phase of the moon and how you hold your left foot with your
right hand when transmitting.

What you need to do is model your specific antenna to see what the
vertical pattern is in your particular installation. It can vary
significantly from one to another.

And BTW - don't worry about the trolls who have no idea what they are
talking about - but insist on showing their ignorance, anyway.

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Jerry, AI0K

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