There are plenty of propagation programs available today. Just like antenna
modelling, the various propagation models are very accurate and can let you
know what
to expect under various conditions.
But, one does not need programs to predict takeoff angles, it's in the
literature and
can be obtained from experience.
My text below was intended to stimulate thinking. For example: If your goal
was to
be able to communicate to Europe from the Eastcoast of the USA (say, mid-New
York
State) on 20 meters, a small beam at 50 feet might do the job during the day.
(elevation angle= ? per modelling program), But to "open the band" during a
contest,
the elevation angle must be lower and a stack at 100/50 feet would be better at
that
time. In the middle of the day, when the propagation elevation angle to Eu
increases, the lower single beam might be better.
That's what I mean by "...analyze your situation..." Someone who isn't into
contests, won't need to "open the band" and won't need the low radiation angle
antenna. On the other hand, a low radiation angle antenna would certainly
help with
propagation from NY to Saipan or Singapore when the band is open to those
locations
in late afternoon (NY time).
Knowing what your goals are will help you decide what type of antenna system to
design/build.
Of course, you should make goal decisions first then design each subsystem to
achieve
those goals in an interactive design.
Bill, N3RR
http://www.erols.com/n3rr
Guy L. Olinger wrote:
> Where is a source of incoming angle by freq, etc? Has anyone ever
> *Measured* incoming angles carefully?
>
> 73, Guy.
>
> >
> > When planning stacks, you need to do a requirements analysis first. (Don't
> > you
> > do this for everything you buy/build/acquire/install/etc??) If you don't,
> > you
> > have no way of knowing whether what you install will do the job you want it
> > to. For example, you should analyze the areas of the country (world) you
> > wish
> > to communicate with on your band of interest and determine the elevation
> > angle(s) you need to achieve that goal, then plan your stack accordingly by
> > modelling it and iterating the design until you achieve (on paper) your
> > desired
> > goal. If you don't do this, you may wind up with a situation that would be
> > unacceptable to you when a little more planning would yield the desired
> > result
> > with the same resources (antenna/tower) only installed in a different
> > manner.I
> > really need to add this subject to my web site. It's crutial to good
> > amateur
> > design practice.
> >
> > 73
> >
> > Bill, N3RR
> --
> Guy L. Olinger K2AV
> k2av@qsl.net
> Apex, NC, USA
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