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Re: First magnifier

In a message dated 99-04-19 09:37:49 EDT, you write:

<< snip>
 >  Interesting note, extra coils larger than 4" dia. did not work good at 
all. 
>  Even when properly tuned, the output was no more than 3' regardless of 
> input.  The input was increased to over 10 kVA to check operation, spark 
> would only go 3' and stop.
 
>   It appears simply as I see it that small drivers = small extra coils 
> (resonators), large drivers = large extra coils. Comments welcomed.
 
> Kevin E.
  >>

Hi Kevin,

I'd say it's all related to the ratio of inductances between the secondary
and the extra coil, and the effective coupling that results, along with the
driver coupling.  If the extra coil inductance is too high vs. the secondary
inductance, the effective coupling will be too low.

Antonio M. DeQueroz posted the following formula some time ago
which can be used to calculate the effective coupling of a magnifier:

          Ke = Kd*sqrt[Ls/(Lr+Ls)]

Where:       Ke = effective coupling
                  Kd = coupling of driver
                  Ls = inductance of secondary
                  Lr = inductance of extra coil

I did some work with this on my video tape # 21, and I posted my
results some time ago.  The bottom line is that the effective coupling
of magnifiers is very similar to that of standard TC's.  For instance
with a driver coupling of k = .42, and practical ratios of inductance
for the secondary and extra coil, the effective coupling might be 
k = .2 or so, which is within the realm of standard classic coil
couplings.  The spark gap sees this lower (k = .2) coupling, and does
not have to battle with the k = .42 quenching conundrum.

If the driver coupling is already too low to start with, the effective
coupling will fall off rapidly with larger secondary/extra coil ratios,
and spark output will fall off accordingly.

Regards,
John Freau