Re: Flat coils & undamped waves (was Wire Length)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

Tesla list wrote:

> Original poster: "David Thomson" <dwt@xxxxxxxxxxxx>
>
> >      Answer to your question is that "inductors are inductors" no
> > matter what the shape and flat spirals have no special and desireable
> > electrical properties.
>
> This is not my experience.  Wind a flat spiral coil to 300 kHz, then wind a
> solenoid coil to 300 kHz.  Coat each coil with 1/8" epoxy.  The flat spiral
> coil will rise in frequency, the solenoid will drop in frequency.  The
> geometries definitely do make a difference.
>
> Further, there are two separate Wheeler equations for calculating the
> inductance of flat spirals and solenoids.  The reason there are two
> different equations, rather than just one, is because the geometry *does*
> make a difference in the coil's properties.
>
> Also, flat spiral coils have a greater range of resonance than do solenoid
> coils.  For the same amount of wire and same average radius, a flat spiral
> coil will have an output with lower potential and higher current than a

   Too much to comment on in one note.  Of course the geometries 
make a difference, the question is whether one is superior to the 
other and I voted for the solenoid.  I can't understand how the flat 
spiral can rise in frequency with the epoxy coating and find it hard 
to believe.
Haven't tried it myself so am no expert.

   I'm not sure what you mean by "greater range of resonance" - 
that's not a familiar term.  As for lower potential and higher 
current, that is a function of the surge inpedance of the circuit and 
not the geometry of the inductor.  For the same L/C ratio the 
performance should be the same.

Ed