[TowerTalk] Modeling vs Experimenting Crowds

[Jeff Blaine]

I'm with Grant on that.  The real value of modeling is not that it will 
ensure you build a good antenna, but rather it will help you avoid 
building ones that have no chance of working the way you wanted.  All 
from the relative comfort of your chair.

There are a lot of reasons why an antenna that modeled well did not work 
when you put it up, but most of those involve things in the environment 
that were not part of your model.  The model thinks that the antenna and 
maybe the ground exist, but nothing else does.  In the real world, there 
is a LOT of stuff around, even if you live in the country.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com


On 9/12/19 10:41 AM, Glenn Pritchard wrote:
> Well said Grant.
>
> Glenn, VA7UO
>
> On Thu, Sep 12, 2019 at 8:18 AM Grant Saviers <grants2 at pacbell.net> wrote:
>
>>
>> On 9/11/2019 9:45 PM, David Gilbert wrote:
>>> I think most of that is fairly misguided advice when it comes to
>> antennas.
>>>
>> I would agree and the rest well said.
>>
>> The NEC programs continually amaze me how well they predict behavior and
>> performance.  There is very little magic left beyond Maxwell.  Creative
>> ideas?  Great - give them a spin in the NEC washing machine. I must have
>> 200 bad ones thankfully never built.  Plus, EZNEC has some nifty
>> generation routines.  Want a tapered wound spiral vertical? - easy.  A
>> few hours of modeling and then we built one - resonance F and R very
>> close, measured A/B gain in the predicted minus few db ballpark. Was
>> that model perfect? - of course not, some significant variables were not
>> possible to model, but the prediction was very close to reality.  As
>> W8JI pointed out, without controlled A/B performance testing, there are
>> just too many variables to declare any sort of victory.  That pretty
>> much wipes out experimental optimization unless you have a real antenna
>> range.
>>
>> I find it depressing to see hams put up at great effort even simple wire
>> antennas that just don't work very well. No need to debate which yagi is
>> better.  Now when asked to help build a DOG of an antenna, I pass.
>> Especially if I was asked and counseled against it.  The folklore that
>> causes folks to build (and buy) them has amazing staying power.
>>
>> Junk antennas are likely one reason folks get frustrated and quit the
>> hobby.  So, I think we have a self interest to encourage building (or
>> buying) good ones.
>>
>> Grant KZ1W
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>