I should have added some additional information....
I was discussing the value of modeling monoband yagis, stacked on the same
tower, not wire antennas and verticals, which may or may not model as well.
However, like all things in life, NOTHING is perfect and no model is
perfect. As in business, I never look for perfection or guarantees, but
anything that can save me time and effort and help me to more quickly narrow
my focus, has great value.
As with all things, you must test thoroughly and compare to see for yourself
what the results really are at your station.
If the model predicted that my "best" JA antenna on 10 was at 13', I might
put an antenna at that height to test it. However, using YT would allow you
to "see" what % of the time signals would arrive at that angle. If 13'
equated to an arrival of 26 degrees and only 1% of the time JA signals
arrived at that angle, I could care less about the 13' antenna.
OTOH, if 38' has a particular JA arrival angle about 15% of the time, that
certainly is worth sticking an antenna there.
Of course the arrival angles are not for my particular QTH and the antenna
in question is not identical to what I am using, but it is close enough to
make it worth while. The results of the past three contests clearly showed
that the modeling was a MUCH more effective and valuable approach than my
Had I not used my experience first, I might not have seen such a huge
difference and been unconvinced. OTOH, had I modeled it first, my contest
scores would have been higher.
It is not important to me that a model might show stacking gain with
antennas separated by 3'. One has to have some understanding of what you
are trying to do and the results that you might see. Often I "test" the
model with ridiculous scenarios to see how well it can predict "off-beat"
situations. This helps me to better understand the limitations and work
with the program rather than take pot-shots at it.
Of course modeling is not a requirement and I did just fine in the past
based on my experience and knowlege. My point was that in the quest to
build an efficient and effective station our time and effort and money is
better spent on using modeling software to plan things rather than rely on
luck. In the end, it will be the combination of modeling and real
experience that will allow us to improve things even more!
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