Re: Foil wound pancake secondaries.

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

Original poster: Finn Hammer <f-h-at-c.dk> 

I now think different of the turn to turn capacitance. I now think that if 
i have a capacicance from each turn to the other, then these capacitances 
will be in series, and therefore will add up to less. The more turns, the 
smaller the capacitance.
So the turn to turn capacitance should not be a problem.
The self capacitance of a coil, as I understand it, is determined by it`s 
physical dimentions, and to some part, the potential of it. Since a pancake 
coil is small, and has it`s high potential hidden in the midle of the coil, 
it probably exibits less self-C than a solenoid coil of identical inductance.
And therefore should be able to let go of it`s charge in a more prompt manner.
Wintesla (My _registered_ copy, that is) says the inductance of a 1000 
turns pancake coil, 8inches outside diametre, is 69.54mH .
However, it stops decreasing the self-C when the coil length approaches the 
coil diametre. When the coil get`s shorter than the diametre, wintesla 
starts to report higher self-C numbers.

JavaTC estimates 76.45mH and a C-es of 4.9pF

A "hats off" for the new JavaTC, by the way. (Even I seem to be able to use 
it now)

I guess I have to wind this coil to find out if it`s any good.

Coils like this are used in loudspeaker pass filters, and they are the rave 
of the Hi-Fi scene.

Cheers, Finn Hammer