"Richard Harrison" wrote in message
...
Reg, G4FGQ wrote:
"It`s purely a matter of Spherical Geometry"

Edmund A. Laport agrees with Reg in his book "Radio Antenna
Engineering". On page 227 Ed writes:
"If, for example, the computed vertical beam angle for a one-hop circuit
uses 6 degrees at an azimuth of 332 degrees and the horizon in this
direction consisted of a mountain range with a height of 8 degrees, the
performance of the circuit would be greatly compromised by the
obstruction of the mountains. In such a case it might be better to work
this circuit with two hops. Then a vertical beam angle of 20 degrees can
be used instead, with adequate horizon clearance for the wave path. Or
if the circuit required 6 degrees for a two-hop circuit 5400 kilometers
long, with the same obstruction cited, one could change to a three-hop
circuit which for the same layer height would permit the use of a beam
at 14 degrees."

Best regards, Richard Harrison, KB5WZI



OR ....... you take advantage of diffraction abilities of physical parts
such as
mountain edges or other physical parts that can deflect the rays AFTER it
leaves
the FEED POINT which does NOT exclude an antenna array of which the feed
point
is part. The point of confusion emanates from.calculating hop distance on
the
basis of a :"standard:". TOA The "magic" of a stacked antenna exposes
the difference
:that occurs with a different TOA.
I suppose you could use Reg's program so that when the ideal conditions do
occur
maybe after several hours of waiting , when one can say that the upper
layers are now
exactly such or such a height and the assumption used in formulating the
program
are now correct. The fact is that ham radio is about formulating an array
that will
provide the hop distance required by the operator since that is something
he can change.
I am quite sure that LaPorte does NOT say that no amount of shaking an
antenna can
change the hop distance which is what TOA is all about and the subject of
this thread.
Maybe we need another thread to clarify the question that Reg and yourself
are
apparently addressing.

Art