That long rant doesn't change anything, I'm afraid. Nobody is trying to
trash anyone, but it doesn't serve you or anyone else for you to keep
insisting something that isn't technically accurate. This is an
educational forum and if you want to believe something that isn't true
that's your business, but don't expect everyone to sit by while you
mislead others.
Just look at your rant below. It almost exclusively talks about HFTA's
terrain analysis capabilities. That isn't the point here at all. HFTA
has been shown to work fine for most terrain studies ... excellent in
most cases as that's what it was designed to do. But that doesn't carry
over to stacking calculations. You keep acting like they are the same
... they are not. HFTA doesn't have a "tolerance for error" on stacking
distance ... IT DOESN'T CALCULATE THE EFFECTS OF STACKING DISTANCE AT
ALL. That isn't my opinion ... that's the word from Dean Straw, the
author of the program.
Dave AB7E
On 6/21/2022 9:08 PM, Billy Cox wrote:
Several of you must just like to b**** when ever a
younger/newer ham asks questions to learn something.
"Go read about it, learn it", and so when they
do using an "approved" source (ARRL publications,
including HFTA) then some now claim to be experts
and trash others when someone tries to actually
learn/build/use/enjoy the technical side of things.
Dean warned about possible errors, what else could
he do? I also mentioned that in a previous post.
Dean did not state HFTA was "virtually useless" for
modeling stacks over terrain did he? No, what he did
state was to be very careful in specific situations.
Yes, I have used HFTA, and prior to that we used a
similar package from K6STI for many years. I have
compared the software predictions with real world
results, and more time than not, it does provide
useful data. Notice I said useful, meaning much
better than ham lore or no information at all.
Perfect? No, again ... but that may also be true as
to the other data used in these HFTA calculations?
Case in point? Let's chat about how accurate is
the terrain data? What if there is large building
at a reflection/refraction point, or nearby, or
... or ... wait ... do we have to throw all HFTA
results out for even single antennas?
Anyone care to debate (I do not) the real world
impact on seasonal terrain foliage at HF bands?
Or how accurate really is your x element yagi as
compared to the gain stated with the HFTA models?
Or do we forget the optimum wave angles in HFTA are
averages, so at one specific time, are not very
accurate, and yet we use it for station planning.
Or the W4-TN profile ... is that accurate for
west TN, middle TN, or east TN? Well?
Or interactions with other antennas, that HFTA
cannot accurately (nor was it designed to take
into consideration) predict what the pattern is?
Do we toss HFTA for interactions? Well?
A practical option is to do what Ron stated, use
HFTA and EZNEC as a way to usefully (note I did
not say absolute accuracy) crosscheck results.
As in the old "trust, but verify" many of us
have used daily in other settings.
At the end of the day, this comes down to the
probability of error and what level of tolerance
(as in inaccuracy) one is willing to accept.
My doctoral chair cautioned that without reliable
and repeatable data, you only have an opinion, and
that everyone has one or more, but such does not
mean an opinion is credible without proven evidence.
So perhaps we need to ask Steve, K7LXC to add a tag
line to remind all of us, in the absence of reliable
and repeated data, we are just a bunch of old farts
trying to out-opinion the last opinion offered? hihi
Here's a closing "opinion" ... why don't together
we make TowerTalk a safe place for any person with
an interest in learning about antenna/towers/safety
to come here and post and not regret doing so ...
73 Billy, AA4NU
On 06/21/2022 9:56 PM David Gilbert <ab7echo@gmail.com> wrote:
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
>
> _______________________________________________
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