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Re: Electrical Properties of Aluminum and Network Analzyer was : RE: Brass



Original poster: "Ed Phillips by way of Terry Fritz <teslalist-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
 >
 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<dhmccauley-at-spacecatlighting-dot-com>
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Monday, April 21, 2003 8:05 PM
 > Subject: Re: Electrical Properties of Aluminum and Network Analzyer was :
 > RE: Brass
 >
 >  > Original poster: "Ed Phillips by way of Terry Fritz 
<teslalist-at-qwest-dot-net>"
 > <evp-at-pacbell-dot-net>
 >  >
 >  > Tesla list wrote:
 >  >  >
 >  >  > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 >  > <dhmccauley-at-spacecatlighting-dot-com>
 >  >  >
 >  >  > Terry,
 >  >  >
 >  >  > That test is severely flawed:
 >  >  > First, we already know that for the same cross-sectional area, 
aluminum
 > has
 >  >  > a higher resisitivity per unit length than copper.  No need to use
 >  >  > a network analyzer for this.
 >  >  > Secondly, a network analyzer is not going to tell you squat about how
 > an
 >  >  > oxidized coil performs under high rf current conditions like those
 > occurring
 >  >  > in a
 >  >  > tesla coil.  You really need to make the measurements somehow at the
 > rated
 >  >  > power levels you are going to operate at for the data to be 
meaningful.
 >  >  >
 >  >  > The Captain
 >  >
 >  > Guess I disagree with that.  The increase in effective resistance due
 >  > to skin effect is independent of the current; there's no mechanism which
 >  > could make it any different.
 >  >
 >  >
 >  > Ed
 >
 > Thats where you are wrong Ed.  At high power, things are always much
 > different than at low power.  For example, take a 10 foot piece of waveguide
 > and hook it up to your
 > network analyzer.  The thing looks like an ideal transmission line.
 > Reflected RF is practically nil.  Now measure it again but at 600 kW peak
 > power.  You cannot imagine the
 > things that start going haywire.

	Well, I guess I still disagree.  I've worked with X and Ku band radar
systems from 250 kW peak, 250 watt average to 10 kW peak, 6000 watts
average and have seen all sorts of heating and breakdown due to the high
power, but never any evidence that attenuation or VSWR varied with power
level.  The forward and reflected power monitors would have shown that
clearly.

Ed

Ed