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
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.
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
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