You are correct. The program uses the number of elements as a surrogate for
the boom length. It assume "traditional boom lengths for the number of
elements. I have a 4 element 20 meter beam on a 54 boom (W2PV says that on
a 3/4 wavelength boom you can use 4, 5 or 6 elements with little difference
in performance) so I use a 6 element beam in the program. For my TH7DXX I
use 3 on 20, 4 on 15 and 6 on 10. But, as others have pointed out, the
benefit of the program is the angle coverage from the stack, not the gain.
The gain figure is only for relative comparisons. GL 73 Saul K2XA
----- Original Message -----
From: <Cqtestk4xs@aol.com>
To: <TOWERTALK@contesting.com>
Sent: Saturday, February 24, 2007 12:17 PM
Subject: Re: [TowerTalk] Two 15m yagi stacking...and SteppIRs
>
> In a message dated 2/24/2007 4:25:59 A.M. Greenwich Standard Time,
> jimlux@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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