Re: Space Winding - was What to look for...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Ed, John,

On 14 Jul 01, at 19:55, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
> 
> In a message dated 7/14/01 2:53:05 PM Eastern Daylight Time,
tesla-at-pupman-dot-com 
> writes:
> 
> >   The 50% to 70% wire "fill" factor is for coils working at higher
> >  frequencies, where skin effect in large wires limits the Q.  In my
> >  opinion, in the region of 200 kHz or less the difference in losses is
> >  not worth the nuisance of trying to space wind the turns.  I have wound
> >  a couple of antenna loading coils for use at 181 kHz.  The wire size was
> >  #28 and the coil diameter was 5.5".  The space-wound coil (used
> >  monofilament fishing line for the spacing and removed it after the
> >  windings has been doped) and the other coil was close wound.  Couldn't
> >  measure the difference in Q, which was around 400 at the operating
> >  frequency.This is neglecting the fact that, at least (again in my
> >  opinion)  the unloaded Q of the secondary isn't of much importance when
> >  the effects of streamer loading are included.
> >  
> >  Ed
> 
> Ed,
> 
> I didn't realize those fill parameters mattered only at higher
> frequencies.  If that's the case, then I agree, the space winding
> would seem to be a waste of time.  The unloaded Q may matter
> some before the sparks break out I would think, but since it was
> 400 in either case, that seems plenty good enough to me.  
> I wasn't really suggesting or advocating the space winding, but
> just saying that a coil can be space wound with thinner wire, 
> and maintain the same inductance, and not hurt performance.
> The space winding may be useful for a person who has some
> thinner wire that they want to use on a taller coil which would 
> otherwise use too many turns.  A practical consideration really.
> The insulation would be improved too I suppose, by space winding.
> 
> John Freau

I'm a fan of space winding for larger coils but don't bother for 
small ones. The major benefits I've noticed are the improved turn-
turn insulation and the cost of the wire.

Regards,
Malcolm