[TowerTalk] Two 15m yagi stacking...and SteppIRs

[Cqtestk4xs at aol.com]

In a message dated 2/24/2007 4:25:59 A.M. Greenwich Standard Time,  
jimlux at earthlink.net writes:

The best  way to answer these questions is to get a copy of HFTA, 
which comes with  the ARRL Antenna book. It lets you model the pattern 
of stacked antennas,  varying spacing, etc., and factoring in your 
terrain, as well.  You  just select the kind of antenna (e.g. 5 
element beam), 


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
But there is a rub to doing that, isn't there?  I think the program  assumes 
a standard length boom for 3 el and a standard length for a 4 el and so  on.  
If one uses the 4 element STeppIR for 10 will it not behave more like  a 6 
element in a stack since it has a boom which is what a usual 6 element  has?  I 
believe the boom on the SteppIr is around 32 feet and the usual 6  el 10 meter 
is around 27.
 
What this means to me is the antenna will "behave" more like a 6 el in  
stacking since the boom length is a primary consideration in stacking  distance.  
The same concept is true for 15 for the SteppIR, with the boom  somewhere 
between what a 5 or a 6 element standard Yagi would have ...32  ft.
 
Because of the above reasoning, I have input the 4 element on 20, a 5 el on  
15 and a 6 el on 10 on the HFTA program in computing stacking distances...not  
the standard 4 element for all bands.
 
I'd like to hear from others on this idea, since I am in the middle of  
modeling the three high stack of SteppIRs on that HFTA program.  I have a  wide 
range of available heights and want to do it right the first time.
 
Bill K4XS/KH7XS
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