"Roy Lewallen" wrote in message
...
Jimmie D wrote:

This afternoon while cleaning a closet I pulled out an old US map that
had been marked with contacts I made back when I worked 10M a lot. After
the local stations there is a big empty area on the map then I started
making contacts again at about 300 miles. Antenna used was a 1/4 lambda
groundplane with the radials drooping so to match 50 ohms. A chart I
found indicates that this means I have a vertical angle of radiation of
50 to 60 degrees. Is this correct??.
. . .

No, it's not. An antenna doesn't have a single angle of radiation, but
radiates at all angles.

Roy Lewallen, W7EL

Thanks Roy, I know but the chart I was using wasnt clear on what it was
presenting. It is a photo copied page out of a book and hopefully there was
more info that went with it than what I have. 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..

Jimmie

"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"

"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.