[TCML] primary tubing

[Neal Namowicz]

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 at pupman.com [mailto:tesla-bounces at pupman.com] 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
>