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Re: [TCML] primary tubing

Thanks, Gary, for your input. As is often (usually) the case with most situations presented on the list, there is usually more than one way to accomplish something. I suppose the proof, as they say, is in the pudding. In this case, I think "pudding" :) the aluminum primary to use on an existing coil with known results will prove it out, one way or another. If I understand correctly, I should use a diameter larger than the 1/4" copper I'm currently using. We shall see, 

Neal.
Ps. What would your other reasons for not using aluminum be, if not the resistance/frequency issues? 



DC,
I have refuted this oft-repeated but mistaken belief of yours that aluminum exhibits some frequency-dependant resistance, several times in the past and I will continue to do so. It does not, to any significant degree. I have made frequency-sweep measurements of the AC resistance for many different conductor geometries, including Al vs. Cu. Of course the aluminum has a higher resistance than copper, but this is due to the intrinsic resistively difference between them and is NOT frequency dependant for the frequencies that we are interested in. If the aluminum conductor diameter is scaled up to compensate for the higher resistively, it's a wash.
There are many good reasons to choose copper conductors over aluminum and I wouldn't use anything but copper myself, but frequency-dependant resistance is not one of them. Please either supply quantitative evidence of your claim, or stop propagating this myth.
To Neal's question - Primary resistance is a very bad thing for Tesla coils. Every (reasonable) effort should be made to minimize tank circuit resistance, if you're going for maximum performance (and not everyone is). 

Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of DC Cox
Sent: Friday, November 06, 2009 5:54 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] primary tubing

At RF frequencies aluminum is a poor conductor as compared to copper.  Use
copper for HF applications. Alum will limit your peak RF current, something you don't want to do. Peak RF current determines peak magnetic field which 
of course links all your power into the sec inductor.

Dr. Resonance


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