Re: Primary spacing, again

["Albert Hassick" <uncadoc-at-juno-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Jon.  My experience is that when You get the windings too close it
becomes difficult to attach a tuning device to the tube without shorting
across to the adjacent tubing.  I like to space mine with 1/4" dowel rods
as a minimum to make the coil easy to tune.  But I think you can get the
windings a bit closer together if you wish, and come up with a
alternative way to affix your tuning connection upon the tube  I use a
big alligator clip on my 3/8" tube primary for tuning and it works good. 
But sometimes when it is set not quite straight on the tube, I will get
arcing across the tubes even though they are not touching.  The thickness
of a wooden tongue depressor  about (1/16") seems to be approaching the
air gap limit of electrical breakdown between the windings.  But I found
that this can be a bit troublesome having the coil wound this close,
especially under humid conditions.    Al.

On Fri, 15 Sep 2000 19:45:24 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
> Original poster: "Jon Rosenstiel" <jonr-at-pacbell-dot-net> 
> 
> Hi all,
> 
> I'm in the process of constructing a 4" coil a la John Freau. I'm 
> thinking
> about using around 30 turns of 0.125 copper tubing for the pancake 
> primary.
> The power supply is a hot-rodded 15kV/ 30mA, (now 42mA), NST. What 
> I'm
> wondering is what turn to turn spacing should I use? At first I 
> planned on
> 0.250", but it seems to me that with so many turns the turn to turn 
> voltage
> wouldn't be that great and I could probably get by with a smaller 
> spacing.
> But how much smaller I don't know.
> 
> Comments and suggestions welcome,
> 
> Jon
> 
> 
>