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Re: TC Output Voltage
Greg, love your sense of humour...
> > > Re:
> > > "A friend of mine who is an RF engineer has examined some
> > > structures and come to the conclusion that a low Zo is required in
> > > the secondary. That is, a low L/C ratio in the helix itself. That runs
> > > completely counter to what we actually do in these machines (Lo
> > > Zprim, Hi Zsec) with Zsec dragged down by a lumped topload."
>
> The surge impedance [SQRT L/C] of the secondary may very well be the most
> important parameter of the TC, as it must closely match the effective arc
> impedance for the best performance.
> Regarding the handful of documented coils where a large toroid improved the
> performance, I have noticed that they all have had a Zsec in the range of
> 30,000 to 50,000 ohms, before the big toroid was added. I tried adding
> a big toroid to my coil (earthmover innertube covered with cable mesh) but
> I didn't see any noticable improvement, and so I initially thought that the
> whole idea was a fraud because, after all, more capacitance should only reduce
> the output voltage, right??? HOWEVER, the Zsec of my coil is only 19,000 ohms,
> and if the arc impedance happened to be in the range of 15,000 to 20,000 ohms
> then a big toroid wouldn't help my coil like it would the higher-Z ones.
>
> Does anyone have opinions or observations as to what a typical arc impedance
> might be? Also, has anyone ever improved the performance of a TC by adding
> a bigger toroid to a secondary with a Zsec of 20,000 ohms or less?
>
> <snip>
> >
> > We are not tied to any particular frequency in designing a coil and
> > I see no reason to use a low inductance in the helix if that is so.
> > Certainly I agree the surge impedance can be arbitrarily lowered
> > by the topload and I think that is where it should be lowered. I would
> > think that under discharge conditions the ESR of the structure is what
> > counts? Your idea of examining equivalent networks is an interesting
> > one and could perhaps lead to some quite different physical
> > configurations. I like it! Definitely one to be explored IMO.
> >
> > Regards,
> > Malcolm
>
> Hey Malcolm, have you ever tried to load the secondary with physical
> capacitors, instead of a toroid in order to improve the performance?
>
> -GL
Point taken :) I think effective arc resistances can only be measured
for and be singly applicable to a well defined set of conditions for
a particular system. I remember doing a rough estimate on one running
coil of several kilohms. Channel current and channel length are both
rather variable quantities. A low Zo is going to give a rather low
unloaded Zshunt which equates with low voltage production for a given
Zbase IMO. (Zo^2 = Zbase x Ztop)
Malcolm