On 08/03/15 18:08, Jeff wrote:

Spike, you seem to think that there are different components coming from
the antenna that make up the sky-wave component and the ground wave.
That is not correct the antenna only radiates one kind of wave (EM).
Whether it finds its way to the receiver by sky-wave or ground wave is
purely due to what angle the wave hits the atmosphere/ground, and the
state of the atmosphere.

As an Example take a transmission on top band; during the day normally
there will be virtually no sky-wave propagation; use exactly the same
set up during the night and there will be considerable sky-wave.

I think I knew that, Jeff...

If your question is what do you have to do to maximize the ground wave
the it is obviously to keep the maxima in the polar diagram as low as
possible and don't waste power shooting it at high angles.

No, I know how to do that. What I'm after is the relative amounts of
power that finish up at the ionosphere, travelling through the
atmosphere, and travelling along the surface, for a typical mobile set-up.

Of course that is easier said than done, particularly with a mobile
where the ground is likely to be poorer than a fixed station with a good
ground mat.

My initial conditions were a ground of average conductivity.

Using something like NEC to model antennas will show the effects of
various antenna configurations and ground configurations on the low
angles of radiation.

But it's only a model, and results depend on how it was constructed.


--
Spike

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