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Re: Natural RF suppression?



Before anyone jumps on me, here is a correction/addition to my 
earlier post:


> 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. 

Not quite. In fact at this thickness, the differences show! BUT, the 
plates of a capacitor are so wide it hardly matters.

> 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 

in something as thick as a primary coil conductor.  Bottom line is, 
if it's thick enough and/or wide enough, the differences between most 
conductors is insignificant.

Sorry for fouling up. Too early in the morning :(

> > Malcolm