RE: Best Primary Coil

Subject:      RE: Best Primary Coil
       Date:  Thu, 24 Apr 1997 13:11:39 +1200
       From:  "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization  Wellington Polytechnic, NZ
         To:  tesla-at-pupman-dot-com

Hello all,
              Interesting comment....

>   From:   "William Noble" <William_B_Noble-at-msn-dot-com>
>     To:   "Tesla List" <tesla-at-pupman-dot-com>
> that's an amazing set of tests and very interesting results - but it
> brings to 
> mind another primary configuration that I think would potentially act
> like 
> your 15 deg coil but without the slant - it seems from your notes that
> the 
> secondary likes to have the outer turns of the primary closer to it
> rather 
> than farther away (at least that's the conclusion I draw from the
> experiments 
> with spacing).  two possible configurations of fairly flat coils could
> do 
> this.  You describe a 16 turn primary, so what do you think would happen
> with 
> the following 2 configurations??
> 1. a two layer X8 turn flat pancake coil - start at the outside, spiral
> in for 
> 8 turns, then raise up an inch and spiral back out another 8 turns.  I
> guess 
> if I were doing this I'd wind it on either side of an acrylic sheet. 
> This 
> would get the turns closer to the secondary without raising them up any.

That is precisely the configuration I will be using except that I am 
planning to use three stacked to give a total of about 200uH. Also
saves half the money for the copper - good use of mutual inductance.