Re: Four Layer Coil

Subject:  Re: Four Layer Coil
  Date:  Sun, 15 Jun 1997 16:39:48 -0500
  From:  "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
    To:  Tesla List <tesla-at-pupman-dot-com>

> Date:          Sun, 15 Jun 1997 09:43:05 -0500
> To:            tesla-at-poodle.pupman-dot-com
> Subject:       Four Layer Coil
> From:          Tesla List <tesla-at-pupman-dot-com>

> Subject:  RE: Latest magnifier results - wire shape
>   Date:   Sun, 15 Jun 1997 07:33:38 +0500
>   From:   "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
>     To:   Tesla List <tesla-at-pupman-dot-com>
> On Fri, 13 Jun 1997 22:40:13 +0000 Bert Pool
> <bertpool-at-flash-dot-net> wrote;
> > I covered this in earlier posts, but here it is again.
> > 
> > We wound our first layer exactly as always.  The second layer over 
> > over the first - same direction.  You'll find that it is very 
> > important that there be NO gaps in the underlying layer or you will 
> > have problems with the next layer.  We did a total of four layers.  
> > Next, we soldered all four wires together.  In effect, the four coils 
> > are in parallel.
> It would see to me that placing the layers in parallel you would be 
> decreasing the inductance, ie.
>  Total I = 1 / (1/Ifirstlayer) + (1/Isecondlayer)...+(1/Inthlayer)
> Are you saying that even though it reduces the inductance it is still 
> a gain over using the equivelent larger gauge wire?

Bert Pool's scheme of winding additional layers of secondary, 
precisely over the first one laid down does NOT reduce the inductance 
because the additional wire is continuously and mutually enveloped in
magnetic field of the original coil.

If these were separated single layer solenoids 
connected in parallel then yes, the result would be reduced 

Bert's scheme is like winding rectangular wire on edge 
to give greater copper cross section without changing the 
turn-to-turn spacing.  In this manner he maintains high inductance.
His technique is actually superior to a single 
rectangular wire however because splitting the cross section over 
several conductors acts like Litz wire, increasing the available skin 
area, and thusly giving lower total RF resistance to the coil.