Re: Magnifier questions

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

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> 

Tesla list wrote:

 > Original poster: "J. B. Weazle McCreath" <weazle-at-hurontel.on.ca>

 > Here's what I do know:  1) The "extra coil" can have a high inductance
 > and a larger than normal top load.

A large top load always increases the power of the discharges. Works
in a regular coil too, but a magnifier may be convenient to put this
large terminal away from the primary circuit.

 > 2) The secondary is tightly coupled
 > to the primary, which is in the helical form rather than a flat spiral.

This is fundamentally to compensate for the removal of the top part
of the secondary as the third coil. A wide and short secondary coil
with a flat primary also results in high coupling, with less problems
with insulation.

 > 3) The secondary is not resonant, but rather works more like a step up
 > transformer, mainly due to the high coupling.

A possible first approximation, but the coupling in any reasonable
system is still too low for this.

 > Now the questions:  1) Is the primary's resonant frequency the same as
 > that of the "extra coil's"? {I suspect that it is}

The primary resonates at the same frequency of the combination of
the secondary and tertiary coils with the top load:
L1*C1=(L2+L3)*C3
This is absolutely essential. Without this, nothing works.

There is an optimal design that requires some other conditions, but
with just this you will have a working system.

 > 2) Is there a rough
 > ballpark figure as to the turns ratio between the primary and secondary
 > of the driver?  3) How much does the secondary effect the frequency of
 > the "extra coil", as I would think it would lower it to some degree?

See the first equation above. L2 and L3 add up. A first step in the
direction of the optimum design is to adjust the coupling coefficient
between L1 and L2 following the relation:
k12^2=L2/(L2+L3)

 > I've gleaned most of what I know on magnifiers from Hull's guide to the
 > CSN and from searching the list's database, but I'm still in the dark.

All that appears in Tesla's writings about magnifiers (and in the
comments) is mostly empirical.
Tesla even writes that the correct relations in his systems were not
known to him.

Antonio Carlos M. de Queiroz