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Re: Natural RF suppression?



Hi Chris,

> Original Poster: mel wise <mwise44-at-flash-dot-net> 
> 
> Tesla List wrote:
> > 
> > Original Poster: "Barton B. Anderson" <mopar-at-uswest-dot-net>
> > 
> > Gary,
> > 
> > Tesla List wrote:
> > 
> > > Original Poster: Gary Lau  28-Oct-1998 0735 <lau-at-hdecad.ENET.dec-dot-com>
> > >
> > > >Original Poster: "Barton B. Anderson" <mopar-at-uswest-dot-net>=20
> > > >
> > > >Could you elaborate more how you constructed the aluminum standoffs in
> > > >between each copper pipe? I was discussing with someone today an idea
> > > >of using aluminum components in a sparkgap. Not to conduct energy,
but to
> > > >utilize aluminum's RF suppression characteristic to enhance quenching.
> > >
> > > What RF suppression characteristic?  Are you saying different metals
> > > favor conduction at different frequencies?  I don't think so.
> > >
> > > Gary Lau
> > > Waltham, MA USA
> > 
> > I'm saying the conductance changes at RF frequencies for aluminum. I have
> > heard this on this list. I don't know how dramatic the change is. At first
> > thought, I was relating this to the resistive oxidation which aluminum
> > develops, but posts indicated it is at the RF frequencies which aluminum's
> > conductive ability drops, and this tells me that it is not the resistive
> > oxidation, but the actual characteristic of aluminum at high
frequencies. I
> > don't know why, and it may or may not be true, but if it is true, then
could
> > this variable be used somehow.
> > Bart
> 
> Heres a question. If aluminum is not a poor RF conductor, then why is it
> usable in a capacitor? I would think that the capacitor would be
> subjected to the same RF the rest of the coil would.
> 
> Chris

The plates in a capacitor are usually thinner than a single skin 
depth so all materials are roughly equal. Personally I don't think 
there is much in it anyway. Consider: the higher resistivity of 
aluminium causes the current to penetrate deeper anyway so conduction 
x-sectional area increases.

Malcolm