Not sure how many times it needs to be said, so just go back and read
KK9A's post.
But in a nutshell, HFTA is an extremely valuable tool for terrain
assessment and deciding how high to put your antennas. It is virtually
useless for deciding on stacking distance because it was never intended
to calculate that, and it will absolutely give you wrong results for
close spacings. You can prove that for yourself simply by running
various iterations.
Dave AB7E
On 6/21/2022 7:37 PM, Billy Cox wrote:
Dean stated in the documentation that there are
known 'traps' with the methodology used. As in
what happens to the reported gain when the ants
are too close ... cautions as to moving each of
the antennas a foot or two higher/lower to also
detect false results. Like any tool, physical or
software based ... used properly, it's useful,
used improperly, well we all know this answer.
Or is Dean wrong also? Did the ARRL make an error
by including the software (with instructions and
stated limitations) as part the ARRL Antenna Book?
So outside of the cautions Dean shared, and used
with other methods (EZNEC/etc.) why would one not use
HFTA as a useful software tool for stack planning?
"That's just plain wrong" B-) B-) B-)
73/bc/NU
On 06/21/2022 9:17 PM David Gilbert <ab7echo@gmail.com> wrote:
Funny ... Ron privately answered me to thank me for the correction.
I never said that HFTA wasn't extremely valuable. I used it when
designing my station to determine the optimum heights for my antennas
given my terrain profile ... at least within the physical limits of hwat
I could afford.
What I said was that HFTA is of no use in determining optimum stacking
separation, and I stand by that statement.
Dave AB7E
On 6/21/2022 6:43 PM, Billy Cox wrote:
Dave G. ... did you miss or ignore this line of Ron's reply?
"One without the other is a waste of time."
Ron is correct, neither program provides a complete answer,
as both have known limitations. On the other hand, Ron is
quite the fast learner, as demonstrated by the excellent
station he has built, with scores that support his planning.
73 de Billy, AA4NU
On 06/21/2022 3:48 PM David Gilbert <ab7echo@gmail.com> wrote:
That's just plain wrong. That's using HFTA to determine optimum height
above ground ... not optimum stacking distance (i.e., separation). They
are NOT the same thing. HFTA does NOT properly calculate anything based
upon stacking separation.
Dave AB7E
On 6/21/2022 11:23 AM, 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.
One without the other is a waste of time.
HFTA tells you where to put the antennas.
EZNEC tells you what antennas to put there.
Ron, WV4P
On Tue, Jun 21, 2022 at 1:00 PM David Gilbert <ab7echo@gmail.com> wrote:
HFTA should never be used to try to optimize stacking distance. It
simply does not actually calculate the stacking gain as a function of
stacking distance like EZNEC would.
73,
Dave AB7E
On 6/21/2022 10:34 AM, sawyered@earthlink.net wrote:
> HFTA kinda sorta calculates stacking properly. It seems to
assume you get
> the optimum 2.7db stacking gain whether the spacing is optimum
or not. And
> it draws the HFTA ray from the center point between the 2. So
it would
> calculate a 2 high stack of 20M yagis having an added 2.7db of
gain even if
> they are stacked only 20 ft apart and will draw the enhanced ray
from the
> midpoint between the 2 yagis.
>
>
>
> Ed
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|