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RE: Coherence ?
Malcom,
Although I'm still a bit fuzzy on the theory related to this thread,
perhaps my meager understanding of RF theory will help. If the voltage
along the secondary is redistrubuted, then the current also will be. It may
be easier to instrument a secondary with current probes along its length and
look for such a redistribution of energy. At first blush the idea of
voltage distrubution changing from linear to another distribution seemed
impossible, but after considering the math from a few different
perspectives, it seems more plausible to me.
The impulse nature of TCs impose boundary conditions I am not accustomed
to solving, but here goes: Let us ssume for simplicity that a helical
resonator is shock excited by a uniform flux U(2) unit function arriving at
t=0. The linkage equation implies the initial boundary condition is the
voltage gradient along the resonator is linear at t=0. The other boundary
condition, at t=inf, an unloaded lossless resonator will have a voltage
distribution of sin(wt)/cos(x). A believe it could be derived that a loaded
lossy resonator will approximate this distribution as it decays to zero, but
our practical experience leads us to believe something similar to this
simplistic model actually occurs. Therefore the Corums may be right.
Bear in mind I have not read these controversial authors' papers, and
please excuse this TC novice if I have totally misunderstood the questions
in my attempt at a theoretical treatment. I am grateful for the posts of
you and all the experienced coilers out there, your patience and willingness
to help us novices is invaluable.
Makin lil tiny sparks in Georgia
Will
> My understanding: the argument is made by them that during
> ringup (or resonator fill?), the resonator behaves as a lumped
> circuit exhibiting a uniform current throughout its windings (how it
> could possibly be identical at the top and bottom with no topload is
> beyond me). They argued (in the notes) that this uniformity was due to
> the primary coupling to the entire resonator. Well it does - sort of.
> k at the top as we all know is a tiny fraction of what it is at the
> bottom if one measures it. However, they then say that once the energy
> is trapped therein by primary gap quench, over a period of time
> (coherence time) the current changes from being uniform to being a
> maximum at the base and minimum at the top. As a result, voltage
> gradient across the windings also changes from being linear (I x Xl)
> to assuming a non-linear gradient (sinusiodal presumably). The
> voltage is always going to be ideally zero at the bottom in the two
> coil system so that doesn't change but what does (they say) is the
> volts/turn across different portions of the winding. The difference
> in total output voltage is claimed to be VSWR vs Q (i.e. rises to
> about 1.3x the fully rung-up value). That's how it reads to me anyway
> and whatever the final value is claimed to be, Ken C. reinforced this
> view in some email to me. It is this redistributed voltage rise that
> I have been looking for and failed to find. He claims it is easy to
> see. I never have. Perhaps I have it all wrong but the implication to
> me is that if the system quenches at the end of the second ringup and
> system losses are low enough, voltage some time down the track
> (Tcohere) will rise to a value that might exceed the value it reached
> at the end of the first ringup. Perhaps somebody can throw some light
> on this. I've never seen any rise beyond natural ringup rise in
> dozens of tests. They claim it happens in the normal course of events
> in a standard two-coil system after gap quench.
> If anyone knows of an experimental setup that would allow this
> to be seen, I would be most grateful to hear from you.
>
> Regards,
> Malcolm
>
>