Re: 15" coil project

["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 Scot,

On 21 Oct 2001, at 14:42, Tesla list wrote:

> Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<bigfoo39-at-telocity-dot-com>
> 
> > BIG SNIPPERZZZ...
> >
> > Exactly.  Someone with experience and adequate
> > equipment really needs to write a paper on how wire
> > gauge/turns etc. affect coil efficiency...hint..hint.
> >
> > >  This sounds like a nice project
> > > you're planning.
> >
> > Thanks.  I hope so.
> >
> > -Brett
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Make a great connection at Yahoo! Personals.
> > http://personals.yahoo-dot-com
> 
> Hi Brett....
> 
> I used 2 secondaries of different design in a coil system ( everything else
> was the same except for
> tune point)
> 
> the first secondary was an 8" 22Ga. wound to 1100 turns   the 2nd secondary
> was 12" with 18 Ga.
> with 1050 turns..  applying the same power to both resulted in 10 - 12'
> arcs on the 12" secondary
> and the 8" secondary resulted in a disaster of racing arcs and fried
> windings....
> 
> I would say it makes a difference :)

Unfortunately, it is difficult to separate the wheat from the chaff 
so easily. Your conclusion takes only a couple of factors into 
account. One not mentioned is the winding length, something to which 
I would attach the utmost importance. My question is: was the voltage 
handling capability of your two coils the same? (Bet = no).

    On the question of wiresize and efficiency, a bunch of 
measurements I did on a range of coils showed clearly that there is 
an optimum sized topload for a given secondary and that if you start 
with a wiresize that is too small, adding topload to the bare coil 
will cause its Q to start diving. A more useful coil will have a 
sufficiently large wiresize that causes its Q to go UP as topload is 
added (until some point where it starts to go back down again as the 
L/C ratio is dropping). An ideal coil will have a topload sized for a 
peak in Q with the coil, a radius of curvature that puts it right on 
the edge of breakout for the voltage being developed, a sufficient 
height for the voltage being developed (to prevent flashovers), and a 
primary surge impedance in the 50 - 100 Ohm range with sufficiently 
large conductors in all primary components. 

Regards,
Malcolm