Re: Calorimeter response #1

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <paul-at-abelian.demon.co.uk>

R.E.Burnett wrote:

> In my tests the resonator impedance increased steadily with spark
> length, but input current, and toroid voltage remained essentially
> constant as described in Gary's old paper.  Available for download
> here:
> 
> http://hot-streamer-dot-com/TeslaCoils/OtherPapers/GaryJohnson/*.jpg
> 
> Paul,  have you seen this paper ?

Not until now. I didn't like it - there are many problems with it. You
describe it as an old paper (couldn't see a date on it) which is why
I've not commented in detail. I suspect Gary has moved on some way
since it was written, so to review it now might be inappropriate.

> I also saw a drop in resonant frequency as the corona grew. 
> My tests were quite rough so I haven't presented any results on the
> list,  but will try to quantify the impedance and detuning at a
> range of powers above breakout if I can.

Yes. To all - the frequency shift is important for analysis and must
be recorded.

> It seems that we are now in a position to understand resonator
> behaviour far better,  thanks to the great work being done by list
> members.

Yes, we have yourself, Gary, Terry, and a recent posting by John
Freau on a closely related observation - John, I'm still pondering
the latter. It's good to see the interest in making loss and load
measurements, but somehow the efforts are disparate.

Guys, there's a problem here. We have to specify what we're looking
for. Me - I want to know what the effective impedance of the breakout
loading is, as a function of frequency, top voltage, and resonator
geometry - a tall order. By looking at the view from the coil base,
the picture is somewhat complicated by the effect of resonator losses,
which is a minefield of traps for the unwary. Now I'm as interested in
resonator losses as anyone, but for the present the breakout loading
seems to be the issue we ought to focus on (+). In which case, I think
the approach used by Terry and partially described in his notes at

 http://hot-streamer-dot-com/TeslaCoils/MyCoils/CWCoil/CWImpedance.txt

has a lot going for it. Simultaneous measurements of coil top voltage
and top load current allow us to gauge the breakout loading directly,
without concern for what's going on in the coil beneath.

Richie, I agree, the constant current at the base is a reflection of
a constant voltage characteristic at the top. The thing is it won't
be quite constant voltage - and to assume so throws the baby out with
the bathwater. What needs to be looked at is just how the load voltage
and current vary in the approximately constant voltage regime above
breakout. Somewhere within that non-linear regime is an equilibrium
point - a condition of optimum coupling to the load, which I would
like to be able to model and calculate. The essential experimental
data from which this would come doesn't appear to exist in the Tesla
community and the tentative results so far put forward by
experimenters such as Terry and Gary are mere forays into the topic
compared with the concerted effort that would be required to make real
progress.  So my request to the experimenters on this list is to stop
giving us tantalising snippets and to join heads in a coordinated
effort to map out the characteristics of load impedance.

On the subject of humidity effect - Gary's observations are a real
eye opener and may go some way to accounting for the apparent day to
day variability of Q measurements. We've given Gary a heap of
suggestions to follow up and I hope the he can find a way to discern
just what the humidity loss mechanism is.

(+) The reason being that for impulsed coils, the secondary Q appears
to be of little consequence - performance being determined by the 
primary gap losses, and the ability of the secondary resonator to
couple effectively to the breakout loading. If we ever want to say 
what the optimum design of a secondary is, for a given power level, we
must try to get some kind of handle on the load impedance.

Regards All,
--
Paul Nicholson,
Manchester, UK.
--