Mike,
With three monobanders on different bands, you can use one of the antenna
modeling programs to derive some initial estimates of the interactions (or
lack of them). For each test set-up, model the antennas one at a time at
the desired height. Then model the array, of course feeding each antenna
one at a time within the array--see whether there is any performance
degradation--and how much.
Although modeling is not the last word on the subject, it can tell you
some valuable things, like real bad separations, whether the separation is
critical or loose (that is, some change yields nothing bad), etc.
If you begin with models that use tapered diameter elements, perhaps you
can develop equivalent models with mono-taper elements--and hence need to
use fewer segements per element. That will make the array run faster and
should have no significant effect on the outcome. Once you have settled
on something close to a definite plan, you can do a final model with the
antennas detailed as finely as you wish.
The antenna modeling programs are limited to level homogenous earth
beneath them, so if terrain is a concern, you can work out some of the
details using Dean Straws or Brian Beezley's terrain programs. However, I
have never heard it established that terrain would affect stacking
distances.
Some commercial antenna makers provide some recommendations on stacking
their monobanders, so you would have a starting point if some of the folks
on the list have those handy. But in the end, for such a complex array
with so much both electrical and machanical riding on your design
decisions, you may wish to research the question for your specific
situation--and one of the modeling programs can certainly help.
I recommend a version of NEC (rather than MININEC) with Sommerfeld-Norton
grounds, although MININEC is likely good enough if you can get the final
array within the segmentation limitations. AO/NW; EL/EZNEC; and Nec-Win
will all do the job you have in mind.
Hope this is useful.
-73-
LB, W4RNL
L. B. Cebik, W4RNL /\ /\ * / / / (Off)(423) 974-7215
1434 High Mesa Drive / \/ \/\ ----/\--- (Hm) (423) 938-6335
Knoxville, Tennessee /\ \ \ \ / / || / (FAX)(423) 974-3509
37938-4443 USA / \ \ \ \ || cebik@utk.edu
URL: http://funnelweb.utcc.utk.edu/~cebik/radio.html
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