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April 1st 06, 09:10 PM posted to rec.radio.amateur.antenna

On Sat, 1 Apr 2006 12:55:51 -0600, (Richard
Harrison) wrote:

Richard Clark wrote:
"The apparent capacitance based on reported resonances and modeled
reactance is on the order of 12 -14 pF."

Have you calculated the self-capacitance of a 2in x 12in single-layer
coil for yourself?

Of course not. There have been a myriad of coils twisted through this
thread and I specifically selected the one that started this epic: the
subject of Yuri's investigation (2½" by 10").

The length to diameter ratio is 6.
H = .92
D = 5 cm

HD = 4.6 pF by the formula on page 451 of the "Radiotron Designer`s
Handbook". Course, formulas are a dime a dozen and disputed.

Hi Richard,

And by virtue of their being offered renders the dismissal of
"approaching zero" as cavalier.

And this was "Self Capacitance" and not distributed capacitance? It
seems to me that any formula for capacitance that neglects the
discussion of surface area must be a very crude estimate. Are we to
believe that a coil of
H = .92mm
D = 5 mm
wound with #44 wire has the same 4.6 pF of Self Capacitance?

I can see the dime's worth of value and the source of dispute. Perhaps
there is more commentary to be found on page 451 that resolves this
and elevates the dime's worth both.

Going further, if I take your coil and merely set the turns count to
18.4, then the coil will self resonate in the 20M band. The
capacitance you computed is not very trivial for HF.

73's
Richard Clark, KB7QHC