[TowerTalk] F12 C19XR Rivets

[jimlux]

On 3/9/16 8:25 AM, TexasRF at aol.com wrote:
> There are plenty of reasons that this capacitance scenario is bogus. It
> would be nearly impossible to maintain a spacing of 1 mil or 3 mils
> between conductors with the pressure created by the element weight and
> wind forces. Then there is the ever changing dielectric constant of
> joint compound as moisture comes and goes with rain. There is the loss
> tangent of the dielectric as well.

Sure, but I think the point is that you have some sort of ohmic 
connection (screws, rivets, what have you) and in parallel with that is 
some fairly decent capacitive connection.  Both change with conditions, 
and both are low enough that it's not a big deal.

I would suggest that since the outer  (farther from the boom) part of 
the element is a cantilever beam hanging inside the inner part of the 
element, that one side has a good high pressure connection of outer wall 
to inner wall, and the other side has a capacitive connection (or lossy 
joint compound or whatever).

In any case, with a 3 element Yagi, I doubt it makes any difference.  If 
you were looking at some sort of exotic superdirective design with a lot 
of stored energy, and where tiny changes in the elements make big 
differences in the pattern, it might be important.  But in that case, 
the wind blowing the elements around is probably a bigger deal.