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Re: s-s testing of Mag
Malcolm and all,
<SNIP>
>> I wonder, though, if the Z which the extra-coil or resonator represents
>> might change under rep-rate conditions. The resonator voltage
distribution
>> will change when repetitively driven and thus the complex feed point
>> impedance will change in phase/magnitude.
>
>Why should it change?
Really, I was thinking that the electric field distribution of the resonator
would be different under s-s conditions, compared with rep-rate conditions.
If this was the case, then the total stored electric field per cycle of
excitation would be different and hence, the capacitance looking into the
resonator feedpoint would be different under s-s compared with rep-rate
operation. Thus the change in complex Z.
Having said that, I suppose that that is an unlikely state of affairs in
real-life: rep-rate driving would almost certainly result in breakout.
However, the crux of this discussion is that we are looking at the
characteristics of the resonator when it is unloaded by streamer formation.
I think we recognise that the resonator feedpoint impedance will vary
wildly, once streamer breakout is promoted.
>> Thus I think the voltage seen at the output end of the resonator will
>> change when it is repetitively driven, but the voltage at the input to
the
>> resonator will not vary (assuming that the source Z of the pri-sec
>> combination is low such that it looks like an ideal "stiff" voltage
source
>> and is not significantly loaded by the resonator).
>
>Does the primary really look like a voltage source? It is ringing
>down as the transfer proceeds.
This is true but I was inferring that the impedance ratio of the secondary
output:resonator input was high ie a 5:1 or 10:1 ratio. That meant, in my
mind, that the load variation presented to the secondary by the resonator is
small. The secondary is not significantly loaded.
I certainly appreciate your point that the secondary is decaying but is it
not still a compliant source, in relative terms? The log decrement would be
considered as droop but I suppose I could argue that the droop is small even
if the Q is low. Maybe the Q would drop to 10 or something like that? In
which case, the secondary still looks more or less stiff in terms of loading
effects of the resonator on the secondary.
>> As a corollary to this: when the feedpoint impedance of the resonator
>> changes under rep-rate conditions (assuming no breakout which would end
up
>> with the 220k/1pF per foot Z being transformed to its conjugate at the
>> feedpoint), and the pri-sec combination is not low enough Z (I'd assume a
>> 5:1 or preferably 10:1 ratio would be needed), then the feedpoint voltage
at
>> the resonator input may droop.
>
>Given the figure Richard Hull gave for the transmission line
>discharge under repetitive running, I would be interesting to see the
>sshot length and compare the two. Would I be right in thinking that
>you are suggesting it might be longer under sshot conditions?
Hmm, good point. I suppose that's what my argument says, yes.
If the loading under s-s is lessened, then the secondary power arc would be
longer, IF you could resolve the fact that arc extension effects could be
nullified. I mean that the secondary-to-ground discharge is an ARC i.e. it
is current dominated and the peak voltage may not be as high as in s-s
operation.
However, my original idea was that the secondary was stiff enough not to be
bothered by the resonator loading (under s-s and rep-rate conditions). In
which case, the secondary output lengths should be the same (arc effects
notwithstanding).
I certainly stand to be corrected...
Cheers
Richard Craven, Malvern, England