Re: Formula for self C of a Coil (not Medhurst)

• To: tesla-at-pupman-dot-com
• Subject: Re: Formula for self C of a Coil (not Medhurst)
• From: "Ed Phillips" <evp-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Tue, 25 Apr 2000 18:33:31 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

> 
I believe the formula actual produces a value that when used with the
> > inductance of a coil  correctly  calculates the resonance frequency but
> it
> > is not the self C of the coil.  Its just an imperical relation to
> calculate
> > Fr.

	Probably correct.  What is your definition of self C?  Normal
engineering use is that capacitance which produces the observed
self-resonant frequency of a coil well isolated from its surroundings. 
Look up original articles by Medhurst and Palermo, which are referenced
in the various editions of the "Radiotron Designer's Handbook".

Ed

	By the way, use of the Medhurst tables or formulae based on them give
predictions of SRF which are plenty good enough for determining the
properties of TC secondaries.  In my own measurements the calculated SRF
is within 3% for coils with an L/D of the order of 4.

Ed

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