[TowerTalk] Tips for Modelling swaged antenna tubing sections

[K9MA]

I haven't tried it, but you could do a simple model experiment. Model a 
dipole with various different swaged sections: ignored, average 
diameter, etc. Use lots of segments, and see how much the resonant 
frequency changes. If those changes are really small, like 0.1 percent, 
it's probably not going to make any difference in performance of, e.g., 
a yagi.

73,
Scott K9MA


On 9/29/2020 12:10 PM, jimlux wrote:
> On 9/29/20 10:00 AM, Mark - N5OT wrote:
>> Back when I would model stuff all the time (K6STI's YO) I just put in 
>> the swaged parts as separate segments that were the correct diameter 
>> and length as the swaged parts. That does not really compensate for 
>> the tiny bit of transition from larger to smaller, but my segments 
>> were chosen arbitrarily to be halfway through that tiny bit of 
>> transition (i.e. the combined lengths added up to the actual phisical 
>> length of the HyGain part I was modeling.  I figured no matter how 
>> inaccurate my method was,
>
> but does the model actually show much difference? One can get way down 
> in the weeds with this - put a tapered segment in that's 1 cm long, 
> etc. But if the wavelength is 20 meters, a 1 cm transition is 0.0005 
> wavelength.  I'd worry more about numerical instability than model 
> accuracy at that point.
>
>
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-- 
Scott  K9MA

k9ma at sdellington.us