[TowerTalk] 80 M 4 SQUARE MODELING

jimlux jimlux at earthlink.net
Fri Jul 21 15:19:57 EDT 2017

On 7/21/17 10:18 AM, Kenneth Goodwin wrote:
> Whether it works or doesn't work, what's your alternative?  Biggest problem
> with antenna modeling software is that the software can't take into
> consideration the physical constraints without extensive sensitivity
> analysis.

There are tools now that let you do that kind of sensitivity analysis in 
an automated way - since it doesn't take hours to run the NEC model for 
each try.

And, from a sensitivity analysis standpoint, you can use a "reduced 
complexity" model  - you're interested in whether there are major 
changes in VSWR or gain or null depth (mostly the latter) as things move 
in the wind or relative to surroundings.

The surroundings can be modeled fairly simply for this kind of thing 
(sure, if you have a really good model of your house and surrounding 
trees, then load it in as  numerical Green's function, but you probably 
don't need that).

And if you move your baseline model by 6 inches, the whole thing
> changes and you don't have the means to control the physical parameters to
> that degree.  Here is what you are supposed to have learned in numerical
> analysis, the optimum solution is not necessarily the best solution. Ken
> K5RG

Very much so.
Or another way - HF Yagi-Uda designs which have performance that falls 
apart if the end of the element moves an inch are probably not "robust"

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