Re: Ungrounded Secondary

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 17 Feb 2004, at 13:12, Tesla list wrote:

 > Original poster: "Gavin Dingley" <gdingley-at-ukf-dot-net>
 >
 > Hi Antonio,
 > am I right in thinking that connecting a top-load to either end
 > results in a half-wave resonant mode, rather than the quarter-wave
 > mode found with a grounded secondary that has only one top-load. As I
 > understand it a standard TC secondary has a low impedance at the
 > grounded base, and a high impedance at the top. In the case of a
 > half-wave resonant coil, there is a high impedance either end, and a
 > low impedance in the centre.
 >
 > I have to admit, the 1.41 factor does appear in some of my own
 > experiments, and I have often wondered why it is higher in frequency
 > when the coil should be resonating at half the frequency. However, you
 > have cleared this up for me very elegantly!
 >
 > Cheers,
 >
 > Gavin

A side note: a grounded secondary in effect does have two toploads,
one being a giant (like the whole globe). You might view the dominant
resonant mode as being a centre-of-gravity-like phenomenon. I wonder
what sort of results one might get by running a coil with a large and
small topload and driving it proportionally towards the end with the
larger topload rather than in the middle? Something to try sometime.

Malcolm




 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Monday, February 16, 2004 12:46 AM
 > Subject: Re: Ungrounded Secondary
 >
 >
 >  > Original poster: "Antonio Carlos M. de Queiroz"
 >  <acmq-at-compuland-dot-com.br> > > Tesla list wrote: > >  > Original poster:
 >  "Gavin Dingley" <gdingley-at-ukf-dot-net> >  > >  > if you connect a
 >  "top-load" to either end of a secondary coil, then you
 > will
 >  >  > find it will resonate at half the usual frequency, i.e. at
 >  half-wave >  > resonance rather than quarter-wave, providing the coil
 >  is positioned >  > horizontally (parallel to the ground). > > Humm...
 >  > You have the same coil with inductance L, with two terminals. Let's
 >  > assume that the terminals account for the greater part of the load
 >  > capacitance C. So we have the same coil, and two capacitances C in
 >  > series (assuming not much changed due to the different position). >
 >  This would resonate at: > f=1/(2*pi*sqrt(L*C/2)). > The frequency
 >  would be -greater- than the "1/4" wave frequency by a > factor of
 >  sqrt(2)=1.4142. >
 >
 >
 >