RE: Electrical Properties of Aluminum and Network Analyzer was : RE: Brass

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>

Dan wrote:
 >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.

I disagree.  The fundamental circuit elements in a real primary inductor, 
Rdc, Rac, L, and C, are all linear.  At any given frequency, these 
parameters are constant regardless of voltage or current levels.  If there 
is some _significant_ loss mechanism that is non-linear, I'm not aware of 
it and I would be interested to learn more if you know of one.  Corona 
losses are not linear, but for similar coil geometries, an Al coil would 
have the same corona losses as a Cu coil.  A curve plotting AC resistance 
vs. frequency on a network analyzer for similarly constructed copper and 
aluminum inductors would be a definitive comparison.  If AC resistance of 
the Al coil is higher on the network analyzer, it most certainly will have 
comparably higher losses in a TC tank.  How much an x% increase in primary 
AC resistance may impact the secondary spark length is still an open 
question however.

Terry wrote:
 >Radio Shack sells like 10 gage aluminum ground wire for TV antennas.  Bare
 >copper wire of the same gage is common.  Just making a coil of each and run
 >them in a high RMS current primary circuit (secondary system not needed)
 >would do it.  I have too many things going on at the moment, but maybe
 >someone else ;-))

It was my plan to construct an aluminum coil for my series of network 
analyzer AC resistance measurements, but I came up empty searching at Home 
Depot and flea markets for Al wire.  Radio Shack - I never would have 
guessed!  Their web site describes a 40 ft roll of 8 gauge aluminum ground 
wire.  That sounds a bit stiff, but I'll check it out and see.  If they 
stock it and if it is solid, I will construct and network-analyze an 
aluminum primary, both before and after a salt-water soak.

Regards, Gary Lau
MA, USA