[TowerTalk] Have you had success with ....

[jimlux]

On 7/20/19 10:50 PM, Grant Saviers wrote:
> I think the topic "resonance of yagi elements" has a total attention in 
> publications of about zero.  Then the topic, "coupled resonances of yagi 
> elements" has substantially less coverage.  With a big stack it is 
> interesting to watch how turning one affects all others.

It has zero attention in ham publications.  I can assure you it has a 
lot of attention in things like spacecraft design, power line design, etc.

ALL structures are coupled resonators of some sort, and particularly 
when there's an excitation to worry about (earthquakes, aeolian, road 
vibrations), people pay a lot of attention.


> 
> IMO real understanding is beyond any rule of thumb, however I do like 
> the thin wall connected to thick wall reasoning.  And building decent 
> models for analysis would be exceeding difficult to get all of the 
> reality captured correctly.


Yes and no - a *good* model is difficult, especially with a complex 
structure (anything other than a single beam of uniform properties).  - 
An *ok* model might be enough to tell you you have a potential problem.

There are tools out there no more complex to use than NEC which can 
handle this. I don't know if they're free, and just like NEC, there is a 
learning curve with a fairly tall first step - just because you need to 
know a fair amount of mechanical engineering terminology. (which, for 
various reasons uses different symbols and definitions than electrical 
engineering terminology)


BTW, a well known aeolian vortex killer is the spiral rope/tube wrapped 
around the *outside* of the element.