Re: [TCML] Q

["Jared Dwarshuis" <jdwarshuis@xxxxxxxxx>]

Hi Gary:

In a nutshell, minimizing dispersion will raise Q. When coupling is tight
there are large frequency shifts, and so there will also be greater
dispersion within the inductor as its energy content is no longer tightly
grouped around a mean value.

Jared Dwarshuis

On Dec 4, 2007 4:33 PM, Lau, Gary <Gary.Lau@xxxxxx> wrote:

> I'm having a difficult time with suggestions that the secondary Q changes
> as a function of its coupling to the primary.
>
> Allow me to preface my comments by noting that while I am an electrical
> engineer, my formal training did not focus on RF electronics, so what I know
> about Q has been absorbed strictly from hobby-level interests.  I may not be
> 100% clear on the strict definition of Q.
>
> My understanding of Q is that it is a measure of the losses present in a
> component.  Let us assume that we have a "perfect" lossless primary, cap,
> gap, and secondary.  Though clearly impossible, the Q of everything would be
> infinite.  The only "losses" would be in the form of sparks coming off the
> top load.  We could adjust the pri/sec coupling and see that there is still
> frequency splitting (NOT an indication of losses), and we can see that the
> rate of energy exchange varies as a function of coupling, just as it does
> with real, lossy components.  Would you suggest that the Q is still varying,
> even though the components have infinite Q?  I don't think that the fact
> that higher coupling permits energy to be transferred more rapidly counts as
> evidence that the Q is reduced.  Or does the definition of Q not care
> whether energy is being transferred to an intended load or to parasitic
> losses within the component?  Regardless, it seems foolish to lower coupling
> if only to keep the primary (or secondary) ringing longer, in the belief
> that this improves the Q.
>
> Regards, Gary Lau
> MA, USA
>
>
>
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf Of Jared Dwarshuis
> > Sent: Monday, December 03, 2007 6:08 PM
> > To: Tesla Coil Mailing List
> > Subject: Re: [TCML] Q
> >
> > As coupling decreases, frequency splitting decreases. The secondary will
> > have its highest Q when completely uncoupled.
> >
> > Secondary Q for a quarter wave coil will be highest at the self resonant
> > frequency ( C/ 4 wire length)
> >
> > Any top load will decrease the Q of the secondary as it allows energy to
> > escape from the secondary. Large top loads allow more energy to escape
> per
> > cycle.
> >
> > Low Q for the system means that energy is disappearing from the system
> > through spark formation.
> >
> > The problem with lightly coupled coils is that you need real big tank
> > capacitors  (it gets expensive).
> >
> > Jared Dwarshuis
>
>  _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla