Re: RF conductor materials (fwd)

To: tesla-at-pupman-dot-com
Subject: Re: RF conductor materials (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Thu, 30 Apr 1998 08:38:31 -0600 (MDT)
Approved: mod1-at-pupman-dot-com


---------- Forwarded message ----------
Date: Thu, 30 Apr 1998 08:29:24 -0500
From: David Huffman <huffman-at-fnal.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: RF conductor materials (fwd)

I agree with you Chip. Unless the oxide is very lossy the current will just
move into the conductive part. We have some large transmission lines here at
work which deliver 100KW that are bare copper. The joints are tin plated to
keep the connection integrity. BTW tin oxide, like silver, are conductive.
Dave Huffman

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Wednesday, April 29, 1998 11:44 PM
Subject: Re: RF conductor materials (fwd)


>
>
>---------- Forwarded message ----------
>Date: Wed, 29 Apr 1998 22:27:17 -0600 (MDT)
>From: Chip Atkinson <chip-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: RF conductor materials
>
>
>>>>>
>oxidize in air.  Over time this layer can become very thick.
>Aluminum oxide is an excellent insulator and is used as such in the common
>form of alumina.  Copper oxide easily forms with similar results.  Since
>RF currents travel on the outside surface of conductors, this can have a
>very significant effect over time as the oxide layer builds up.
><<<<
>
>I have a couple questions about the above statements.  First, please
>explain the difference between an enamel insulating cover and an Al2O3
>insulating cover.  How can it make any difference what type of insulation
>that is on a wire as far as its current carrying capabilities go?  (short
>of the temperature at which the insulation burns or melts).
>
>If the concern is reduced diameter of the conductor due
>to the conversion of Al to Al2O3 then is it really such a big deal?  Even
>well weathered (in the dry climate of Colorado anyway) Al has at the very
>most 1/64" oxide.
>>>>>
>Aluminum
>house wiring used years ago keeps fire departments busy today :-((
><<<<
>I believe that the reasons that Al wire is so bad are as follow:
>Al-Cu connections corrode leaving small contact areas which can heat up.
>Not necessarily as an effect of the previous sentence, an Al wire melts at
>a significantly lower temp. than Cu.  Also, Al burns quite readily once it
>gets started.  As any pyro knows, Al powder can be quite flammable.
>
>Chip
>
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> Chip Atkinson
> http://www.pupman-dot-com
> --- If I can't fix it, I can fix it so it can't be fixed --
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>