Re: Resonance

That's a reasonable value, but how to calculate it is:

Determine your coil's inductance, using this equation:
where mu is the magnetic permeability of the core (4*pi*10^-7 for
N is the number of turns (count turns per inch),
A is the cross-sectional area of the coil in square meters,
l is the length of the coil in meters, and a is the radius of the coil
in meters.

Next, calculate its Medhurst constant using this formula:
where h is the height of the coil, and d is the diameter of the coil
(units don't
matter, as long as they're the same)

Now, you can calculate its self-capacitance by multiplying the Medhurst
by the diameter of the coil in centimeters:
where Cself is in picofarads.

Therefore, to determine its free-resonant frequency (frequency with no
use this formula, using the self-capacitance for C. If you want to get
its actual
resonant frequency, add the self-capacitance to the topload capacitance:
where L is in henries, C is in farads, and F is in hertz.

And to get the ideal frequency (quarter-wave resonance), use:
where Wl is the secondary wire length (not winding length) in meters,
and Fq is
in hertz.

Tesla List wrote:

> Original Poster: Philip <shadow42-at-totcon-dot-com>
> I have recently been trying to determine resonance of my coil. I dont
> really know
> what value it has, but ive seen that quite a few people have measured
> Does 243khz sound reasonable for a 4.5 x 20" coil?
>     Thanks
> Philip Mac Duffie

           --Mr. Postman (Doug Brunner)