Re: 3000 turn secondary

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Bart, Marc,
              This is a gnarly one:

On 23 Aug 00, at 20:06, Tesla list wrote:

> Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net> 
> 
> Hi Marc, 
> 
> Tesla list wrote: 
> >
> > Original poster: "Metlicka Marc" <mystuffs-at-orwell-dot-net> 
> >
> > Tesla list wrote: 
> > > Hi Marc, 
> >  
> > bart, malclm, john, all 
> > after digging the spool out i found that it is a 9 pound spool. john f. 
> > gave me a 
> > suggestion of winding the 3k coil and maybe a 2.5k or 2k one for 
> > comparison, and 
> > your suggestion sounds good also. so i started winding the 3k coil tonight,
> > i'm 
> > winding by hand with a rolling jig so it will take a while. after i get it 
> > done, if 
> > it works well, i will wind a 2k coil same dia. (which i finally put a tape 
> > measure 
> > to and found out it has a 8.75" outer dia.. hind sight 20/20 on me) for 
> > comparison.
> 
> 
> I know exactly what your talking about with the "hind-sight". When I first
> built my 12" coil, it was 34" high. I later went to buy an add-on form and
> found ALL different sizes. They vary greatly! I used a tape measure to
get the
> right diameter (which I found to be 12.75"). 
> 
<snip>
> I'm glad to hear you taking on this task. We should all discuss the
spacewound
> coil. There are several methods to spacewinding a coil. Personally, I
think you
> should spacewind the coil with the same number of turns keeping the
inductance
> as close as possible between coils. This will make the form a little taller,
> but... I don't know, what does anyone else think? I'll have to run some more
> numbers and look at the frequencies. I would like to see all the coils at the
> same resonant frequency. Sd should be the same between coils and proximity
> losses can then be quantified accurately. 

If the secondary resonates at a different frequency it 
necessitates some change in the primary, be it L or whatever. 
Suddenly there are other variables changing. I agree Fsec 
should remain the same. To spacewind with the same number of 
turns, a smaller gauge of wire will be needed in addition to 
what Marc already has. If on the other hand, Ns is reduced and 
more top C is added to keep Fsec constant, top storage 
suddenly changes. There are fish hooks in this exercise 
everywhere. I've agonized over similar problems for months.  
I once had two coils which were pretty much identical save for 
the wire gauge. They were progressively stripped down as 
several days of measurements took place. I should have fired 
them up before reducing the from 5:1 to 0.5:1. A lost 
opportunity.

Malcolm