" In truth, i could receive that signal holding a hand held 10GHz receiver
while sitting on the ground. The 80m hill is nothing from an observer 10KM
away...only .006 degree from the top of the transmitter tower. It is part
of the horizon. I love it when you guys talk like you are sol
knowledgeable yet lack the common sense to conceptualize the problem as it
really exists.

So you are saying that you can achieve 30km at 10GHz to a hand held receiver
at ground level with a 300 foot hill in the way!!! I am sure that you could
not do this with any sensible power even at 2m let alone 10GHz.

Perhaps it is your concept of what is going on that is wrong. Have you heard
of Fresnel Zones??
When obstructions come within the first Fresnel zone significant attenuation
occurs.

With the situation that you are describing the path is totally obstructed,
with the path only possible due to diffraction from the hill top. The hill
top impinges to at least the top of the 5th Fresnel Zone, hence the
attenuation is very high.

As the height of the Rx antenna increases the attenuation is still very high
until the hill top only start to intersect with of the first zone (antenna
height~150m). It then drops quite rapidly until there is true line of sight
and bottoms out when the hill top is clear of the second zone.

You make a great deal of the hill only being 0.006 degree at the horizon. If
you plot it accurately and with reference to the Fresnel zones, it does make
a big difference. With the Rx antenna at ground level the top of the Fresnel
zones are never below the horizon, which is completely different to the
situation when the hill is there (-5th Zone obstructed).

Also, without the hill you only have to raise the Rx antenna to about 15m to
achieve line of sight compared to 200m with the hill there!!!!!! Quite a big
difference I think you will agree, and one that your 'conceptualisation
doesn't seem to allow for!!

73
Jeff