[TowerTalk] Stacking Tribanders

[David Gilbert]

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 at 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 at 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 at 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 at 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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