Re: Ungrounded Secondary

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

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


----- 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.
 >