"Sal M. Onella" wrote in message
...

"Jimmie D" wrote in message
...
The chart does seem to be
indicating that one should use the closest skip contacts to get an idea
of
the radiation angle. It was my doubts about this that inspired my
question.
Perhaps I am taking the chart out of context or maybe it is just wrong..

You shouldn't doubt a chart of things that happened. What you said makes
sense, otherwise. As Cecil said, the radiation leaves your antenna at
(optimum) angles between 9 and 53 degrees. (That's the half-power
beamwidth
in an elevation view.)

Low angle radiation, the ground wave, peters out after a few miles, but
you
do get local contacts with it. High angle radiation goes into space and
is
lost. The mid-angles are refracted in the ionospere and returned to
earth.
That's your set of distance range contacts.

Think of how it would be to toss a tennis ball toward a ceiling: If the
ball could go straight up through the ceiling, it would be lost; also, if
a
low-angle toss never hit the ceiling, it would also be lost. It's those
mid-length tosses that bring the ball down somewhere in the room that pay
off. I realize this is an imperfect metaphor, but it may do the trick
for
you.

"Sal"



I dont doubt waht Cecil said but the way this chart is written it would make
you think that you should base the angle of radiation on the closest
contacts that are "skip". I assumed that someone COULD make a chart like
this. I was actually hoping this would be the case because it is much easier
to discern that leading edge than try to pick out some point in the middle.
NOW I dont this this graph wa intended to be used to determine the radiation
angle of any particular antenna. Rather I believe now that it was intended
as an educational tool to get across the relationship between vertical angle
and skip zones.