Secondary resonance freq

From:  Bill the arcstarter [SMTP:arcstarter-at-hotmail-dot-com]
Sent:  Wednesday, June 10, 1998 10:16 AM
To:  marco-at-vistacom.fi; tesla-at-pupman-dot-com
Subject:  Re: Secondary resonance freq

Marco, coilers,
> I measured yesterday the resonance frequencies of my secondary. It is 
> 4.3" diameter PVC tube, winded for a length of 19.7" with AWG 26 wire.
> I got the following results:
> 324 KHz
> 813 KHz
> 1475 KHz
> 1766 KHz
> 2053 KHz

I measured some similarly 'weird' values for a friend's coil.
Approx dimensions are 3 inch diam, ~24 inches long, way too many turns 
of #30 or smaller magnet wire...
First resonance was at 208 KHz
Second was at 512 KHz
Third was at 800 some odd KHz.

I would have expected the 2nd resonance at 2x or 3x 208KHz but it didn't 
work that way...

I noticed that only the first resonance was very deep (an indication of 
Q?).  The others did dip, but not as far, etc.

Any ideas what this means?

All resonance points shifted according to the proximity of stray 
objects, etc.  Testing was performed w/o a topload and the output of the 
sine generator was scoped directly through a sense resistor.

-Bill Pollack (arcstarter)