RE: K Factor & Mutual Inductance

        RE: K Factor & Mutual Inductance
        Mon, 14 Apr 1997 19:23:17 -0400 (EDT)
        richard hull <rhull-at-richmond.infi-dot-net>
        Tesla List <tesla-at-pupman-dot-com>

At 04:59 PM 4/13/97 -0500, you wrote:

>Whoa! It is the resistance at the frequency of interest (effective 
>AC resistance). The rho of the material is factored in. The only 
>reason it is difficult to calculate is the many-bodied problem. The 
>surroundings affect it. You can test this for yourself. Try mounting 
>a primary and cap close to ground and measure its Q without the gap. 
>Then sit it up a few feet and measure again. This should be of 
>interest to anybody wanting to couple more primary power to the 
>secondary than ground etc.  You can also see the effect of doing this 
>on the secondary.


We did all this work over 5 years ago and you are correct, of course. 
found also that given a coil length X, that at an altidue above earth of
the Q just didn't change any more and that at 3X altitude, there was
to be gained in Q with more altitude.  The shortest coil used was 6" and
largest 30".  Most of them were in the range of 2.5:1 to 4:1 L/D ratios.
All this work is visually documented on one of our old video report

 As always, these are generalizations but at least are based on some
experiment.  So, in conclusion, nothing is easy and there are no pat
formulae where every variable is considered or even knowable.

Richard Hull, TCBOR