RE: Bart's Coil

["Tesla list" <tesla-at-pupman-dot-com>]

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

John,
      You've got my interest:

On 27 Nov 2001, at 21:07, Tesla list wrote:

> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> 
> 
> Bart -
> 
> Thank you for making the K Factor Test. It looks like the K of your coil is
> definitely 0.165 and the 653.52 is the correct mutual inductance. This is
> proof that these two tests can certainly be used to find these two
> parameters accurately when tests are properly made. I admit the tests are
> not easy to perform and you did a good job.
> 
> The reason I wasn't sure that you could make the test is because when the K
> becomes smaller (looser coupling) the two frequencies get closer together
> and it is harder to read the frequencies. A frequency counter would make it
> easier to read the frequencies than an oscilloscope. Note that it is a
> coincidence that the operating frequency is near these two frequencies.
> Changing the toroid size would change the operating frequency but not the K
> factor frequencies.
> 
> Several years ago I made a rough graph of the K factor vs Fo/Fs ratios. It
> is obvious from the graph that for K's lower than 0.2 the two frequencies
> get very close together. As an example when the K = 0.165 the ratio of Fo/Fs
> is 0.986 (7.2/7.3) and when K = 0.10 the ratio is 0.995, a difference that
> will require careful measuring. For the graph click on
> 
>        www.mgte-dot-com/graph10.pdf
> 
> You will need Acrobat 4 or 5 (free) to review and print the graph. I lived
> in California when I made the graph but now live in Jacksonville Florida.
> 
> Here is an unsolved problem for advanced coilers. What is the relationship
> between the resonant frequency of the unloaded secondary coil (114.56 KHz)
> and the open secondary (unloaded) test frequency Fo (68.493 KHz)? Is there a
> theoretical equation that relates these parameters?
<snip>

Would you mind re-stating the last paragraph please? I'm not sure 
exactly what it is you're asking. Is one frequency quoted with the 
secondary shorted end-end? 

Thanks,
Malcolm