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Re: Fine Tuning a Spark Gap
To Mike, D.C., All.
I have to agree with Mike's statement below. If one has an aluminum
conductor in a (Tesla coil) tank circuit, that is of sufficient surface
area,
I see little (if any) degredation in the performance of the circuit. People
have been using aluminum rectangular strip for flat spriral primary
inductances, for many years, with very good success. Moreover, if
aluminum is so poor a conductor at radio frequencies, then how come
all the commercial capacitor manufactures use this material in their
extended foil construction? The high end polypropylene capacitors
using this foil exhibit very low ESR and ESL numbers, and very high
Q's.
Of course, the conductivity of aluminum is not as good as copper.
In coil designs where every precious joule of input energy must be
conserved (at any cost,) then clearly, copper is the superior choice.
Granted, you wouldn't want to use aluminum wire for a secondary
inductance, but where a primary inductance is concerned (typically
say less then 100-150 feet in length and a strip width of say, 2",) I
know of a number of very effective and efficient coils that have been
built, using this material. One common trick has been to use 4 to 5
strips of equal width, and sandwich them together, then wind the
flat spiral. Using this method, each individual strip had a thckness
of around 0.020 to 0.030"; therefore a composit thickness of 0.100" to
0.150".
Bill Wysock.
--------------------------------------------
Tesla Technology Research
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From: Tesla List
To: Tesla List
Subject: Re: Fine Tuning a Spark Gap
Date: Thursday, October 29, 1998 7:59AM
Original Poster: Hollmike-at-aol-dot-com
In a message dated 10/28/98 9:43:43 PM Mountain Standard Time,
tesla-at-pupman-dot-com writes:
>
> Mike,
> What I've heard has been from this list. Aluminum at RF frequencies is a
> poor
> choice for a conductor. The conductance is affected by the frequency and
> the Q of
> the conductor drops. That's what I meant by RF suppression. I didn't mean
> the
> frequency was suppressed.
> Bart
>
I didn't think that the frequency could be suppressed as mentioned in your
last sentence. I am not sure I can agree with the statement that aluminum
is
a poor conductor at TC frequencies. Chip uses a primary made from a strip
of
aluminum(about two inches wide) cut from a roll of flashing. His coil does
quite nicely with it. Perhaps it would do even better with a copper strip
of
identical size, but as far as I can tell, aluminum works just fine. Maybe
this is simply due to the large surface area of the conductor. Whatever the
case, I wouldn't hesitate to use a similar design.
Mike