[Antennaware] Using YO to analyze stacked Yagis

[George Dubovsky]

OK, I know that there is interaction between the antennas, and between the
ground and the antennas; all that shows up in the models. But knowing that
the antennas will be used as upper, lower, and both, what is the default
condition to optimize and tune (each Yagi) to? Does everyone do it
differently?  I have seen enough difference in the tuning in YO (for
individual Yagi in free space, single Yagi at one height, and Yagis at a
certain stacking distance) to make me ask the question.

Guy, I have 2 over 2 on 40, at 145' and 85', and I do believe that it works
as a proper array when the Yagis are pointed in the same direction. And it
definitely works when I split them apart and beam in different directions.

Is there a YO guru in PVRC?

73,

geo - n4ua

On Sun, Feb 26, 2012 at 3:21 PM, Guy Olinger K2AV <olinger at bellsouth.net>wrote:

> This is true, always has been.  Typically a commercial yagi is designed
> for single use, far and away the most common use.  Stacking three plus
> elements does produce the kinds of improvements proffered for stacks.  The
> difference in a stack of single use design and a stack designed as a stack,
> probably cannot be detected by the other end, with other issues, like
> feedline loss, or corrosion issues a far greater villain.  Further, even in
> stacks, a lot of the use is still lower only or upper only, STILL
> vindicating design for single use.
>
> Stack interaction is VERY evident if you stack two element beams, as their
> interaction is huge, rendering two element stacks not worth the effort.
>  The free space pattern of a yagi needs have an over/under null to stack
> "well".  This is very easy to model.
>
> 73, Guy.
>
> On Sat, Feb 25, 2012 at 5:21 PM, George Dubovsky <n4ua.va at gmail.com>wrote:
>
>> I am trying to optimize a pair of HyGain 204BA for use in a stack. I am
>> using YO v7.61 and, mostly, I think I know what I'm doing at a basic level
>> ;-)
>>
>> I intend to mount one at 70' and one at 110' (that seems to work in HFTA
>> for this location), but that's not my problem. I can optimize an antenna
>> at
>> either height, and I can design a new Beta match. But when you select the
>> stacking feature of YO (using 40'), the element spacing seems to want to
>> be
>> different and the matching of course changes. What that seems to be
>> telling
>> me is that when I select upper, lower or both using a stack-match only one
>> condition is going to be correct, and the others will be a compromise.
>>
>> It can't be this tough - I feel that I am mis-interpreting the YO
>> instructions or something. For instance, It may be that the stacking
>> feature of YO is only intended to tell me what the combined pattern will
>> be, but I don't get that from the manual. (My manual is marked Version
>> 7.5).
>>
>> What is the proper sequence of steps for optimizing a stack?
>>
>> 73,
>>
>> geo - n4ua
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>
>