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Re: Formula for true self capacity of a coil.


	I can't understand the interest in great accuracy in  calculating TC
inductance and capacitance when some of the factors  are not readily
quantifiable.  For example, the reactive component of streamer loading
is a non-linear function of time and power being dissipated in the
streamers.  Most of the simple formulae are quite adequate "for
government work".  As for "Wheeler's formula", he had more than one,
their use depending on the L/D of the coil.  Furthermore, in many cases
a correction for "current-sheet inductance" is needed.  Stuff is all
available in almost any edition of The Radiotron Designer's Handbook,
for instance.

	For those who might be interested I have written some DOS programs 
(have Mac versions too) which calculate inducatance to an accuracy
determined strictly by the accuracy with which the coil dimensions are
known. Also have same for calculating mutual inductance and coupling
factor for coaxial round coils such as TC's.  If anyone is interested
I'll be glad to email them.


Tesla List wrote:
> Original Poster: "Gavin Dingley" <gavin.dingley-at-astra.ukf-dot-net>
> Hi Dick,
> actually there were slight differences between the inductance values
> calculated by Malcolm and those by myself, even though we both used the
> Wheeler formula. In the end I just posted Malcolm's original values, but
> probably used my own in the actual calculations. Even if yours ahd been used,
> I guess the difference would not be much.
> However, I have personally run into an interesting little problem with the
> Wheeler formula, but this I shall describe in a separate posting.
> As for the formula for the intrinsic capacity of a coil (Ccox), I have a
> little question to pose; does this formula only work for an upright coil,
> it the same coil were horizontal to ground instead or even far removed from a
> ground plane?
> Regards,
> Gavin