Spike wrote:

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.

I would rephrase your original question as follows. The approximate
signal strength of the space wave at a certain distance, assuming a
fairly low angle of the main lobe of the aerial with a moderate amount
of gain over isotropic, can be calculated from simple physics. At
about the same distance (and where of course you are not likely to see
the space wave unless you have a very tall pole, but it has a defined
signal strength well above you), what is the likely signal strength of
the ground wave? Is it very much lower due to poor coupling, losses
etc.? Is it about the same? Or is it much higher due to some
phenomenon which I can't explain at the moment? That is really the
same question as the one you asked (I think!), but couched in practical
and testable terms.

(It is rather trying to see the ignorant mocking a perfectly reasonable
question from a position of total incomprehension. A bit juvenile,
methinks.)

--
Roger Hayter