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Re: Keeping up with the theory (was is Corum and Corumforbidden topic?)

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Ray,
        I think there are two issues here:

On 6 May 2002, at 7:08, Tesla list wrote:

> Original poster: "Ray von Postel by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <vonpostel-at-prodigy-dot-net>
> Ed:
> Thanks for the information on the availability of programs.....even expensive
> ones.  My 
> comments were based on the method of computation using empirical equations
> rather
> than those that are general in nature.  Why use approximations if there are
> better methods?
> Rob:
> Are you saying that the equations currently being used for distributed
> capacitance yield
> accurate and precise results and are based on Maxwell's equations?  If
that is
> the case,
> then why bother with Wheeler et al?

First there is a scientific approach to model resonators etc. as 
exactly as present techniques will allow. This will probably lead to 
optimizations for building a coil specified requirements and possibly 
new phenomena to be investigated as precision in the result improves.
     Secondly, there is a dirty quick and simple approach to designing 
coil which *will work* even if not optimally. Approximations such as 
Wheeler and Medhurst are ideal for back-of-the-envelope calcs to get 
well within the ballpark. I frequently use these methods with 100% 
success. Suppose I have a friend over who wants to see a coil going - 
or I wish to show him/her something about a running coil. I can pull 
a resonator off the shelf, pull a primary out of the rafters, do some 
quick calcs and have a running coil for some particular power level 
in a matter of minutes. 

> No one, so far, has convinced me that a project to come up with a 
> equation
> for the calculation of parasitic capacitance of a solenoid would not be worth
> while.  The 
> limitation on precision and accuracy should be the ability to readily measure
> dimensions
> and not on the math.  Any such equation, set of equations, or procedure
> be usable
> by any one on the list who has a computer.  Why any one building a coil would
> want to do so is beyond me.  It seems to be a mountain that is there and  has
> not been climbed.

I think there are a number of programs around that would fulfil that 
need. I don't personally use them. A calculator is sufficient for me. 
Regarding an accurate Cself for the resonator, Medhurst does a pretty 
good job but in the end, take sno account of the terminal one usually 
places on top of the resonator. Likewise, a formula for the bare 
capacitance of a particular terminal takes no account of the mutual 
interaction with the resonator below it. 

> This seems to be getting a bit far from coiling,  I would be glad to continue
> this
> discussion off list.
> Best
> Ray

Don't agree - unless I've misunderstood.