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

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

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