[TowerTalk] Capacitors To Tune 160 Vertical

[Jim Brown]

On Thu, 29 Nov 2007 15:56:39 -0500, Martin Ewing - AA6E wrote:

>I know Jim knows better, but there are 
>few components that know or care how much power is "pumped 
through" 
>them, although people often speak as if they did.

Oh, but capacitors DO care (or at least WE care) what power they're 
dissipating. Yes, it's current and I squared R or voltage and E 
squared divided by R, where R is the ESR in the case of current, and 
the equivalent parallel resistance in the case of voltage. That's an 
important part of what we pay for when we buy a capacitor for high 
power applications -- low loss. The same can be said for inductors, 
of course. Indeed, the STRAY elements of a component are often more 
important than the nominal value stamped on them (or that we measure 
at low frequencies). 

In the simple experiment I did, I did not take time to measure the 
feedpoint Z. I did this experiment with the antenna that is 
currently installed, which is tuned even lower in frequency than I 
plan for the new one. When I build the new one, it will be tuned per 
the design I've worked out with NEC. Of course a vacuum capacitor 
would be better. :) 

I hope the assembled multitudes will put up with my somewhat poetic 
descriptions of things, which are intended to describe what I'm 
talking about while not being excessively pedantic. Many of us had 
enough of that in school. :)

73,

Jim K9YC