[TowerTalk] Stacking Tribanders

[David Gilbert]

Exactly this ... in every respect.

73,
Dave   AB7E


On 6/21/2022 7:30 PM, john at kk9a.com wrote:
> Incorrect because you can wind up with Yagi's that are too close together.
> HFTA does not compute interactions between individual Yagis, EZNEC does.
>
> The manual https://manualzz.com/doc/10293860/hfta---instructions states the
> following:
>
> The internal Yagi model in HFTA is a very simple mathematical model. It does
> not compute interactions between individual Yagis in a stack-HFTA assumes
> that each antenna is a "point source." For antennas stacked more than about
> a half wavelength apart this is not a problem. For example, you should be
> cautious specifying spacings less than about 20 feet on 20 meters (and
> proportionately scaled on other bands) because of mutual-coupling effects
> between real antennas. Spacings less about 20 feet on 20 meters will show a
> false increased gain in HFTA, even though the real effects of interaction
> between the beams will actually be to decrease the gain.
>
> John KK9A
>
>
> Ron WV4P wrote:
>
>   HFTA should Always be used to try to optimize stacking distance.
>   It shows the nulls and enhancements created by Your Terrain, and how to
> exploit and or cover them. Then you can use another program, like EZNEC to
> calculate the stacking gain as a function of stacking distance based on the
> HFTA data.
>
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