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*To*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Subject*: Re: [TCML] [Secondary wire length) question*From*: paul <tcml88@xxxxxxxxxxx>*Date*: Thu, 07 Jun 2012 10:58:18 +0000*Delivered-to*: teslaarchive@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxx*In-reply-to*: <53912507.1432972.1338907883476.JavaMail.root@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>*List-archive*: <http://www.pupman.com/pipermail/tesla>*List-help*: <mailto:tesla-request@pupman.com?subject=help>*List-id*: Tesla Coil Mailing List <tesla.pupman.com>*List-post*: <mailto:tesla@pupman.com>*List-subscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=subscribe>*List-unsubscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=unsubscribe>*References*: <53912507.1432972.1338907883476.JavaMail.root@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>*Reply-to*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Sender*: tesla-bounces@xxxxxxxxxx*User-agent*: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.28) Gecko/20120313 Thunderbird/3.1.20

Greg Westfall wrote: > I found on one site that the length of wire on the secondary, > that has always been 1/4 wavelength, is no longer valid, > that it has been proved wrong. It was never valid, only a myth, so there is no disproof to cite, Just measure any Tesla coil to see that it doesn't work. Further to Matt Siri's answer, here's a graph showing how the velocity factor (with respect to the wire length) of the 1/4 wave resonance varies with the ratio height/diameter of the winding. http://abelian.org/tssp/ph1.gif Mutual inductive and capacitive coupling from one part of the coil to another have significant effect on the propagation of signals from one end to another. The resonant frequency of the wound wire is quite a lot higher than that of the straight wire, at least for normal TC h/d ratios. The velocity factor is roughly ln(h/d) * 0.39 + 1.19 where ln(h/d) is the natural log of the height/diameter ratio. This formula can be turned around to give an expression for resonant frequency given the h/d ratio and wire length, Fres = (0.39 * ln(h/d) + 1.19) * 75e6/wire_length Similar curves exist for the overtone resonances, eg http://abelian.org/tssp/ph3.gif http://abelian.org/tssp/ph5.gif A related myth is that you should add toploading to the coil to pull its resonant frequency down to the frequency that its wire would have if straightened out. Nothing special happens if you do that, although the resulting TC ends up with a large topload which is desirable anyway for other reasons. -- Paul Nicholson -- _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla

**References**:**Re: [TCML] [Secondary wire length) question***From:*dave pierson

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