Re: More Coupling...

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 12/9/00 1:52:11 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "BunnyKiller" <bigfoo39-at-telocity-dot-com> 
>  
>  Hi All...
>  
>  while reading all of the coupling threads, I began to wonder about the
>  coupling of
>  a helical primary and if anyone has done any experimenting on the distance 
> from
>  the secondary. ( e.g. instead of having a helical primary say 2" from the
>  secondary , how about having it 6 or 8" from the secondary?)

Scot,

A helical primary has to be much farther away from the secondary
than a pancake primary, because it's sort of the average distance
that matters.  So if a pancake primary is 1" away from secondary
but extends out to 10" from secondary, the average distance is
about 6", so the helical primary would need to be about this far
away, except it has to be even further away.  This is because
the helical primary extends upwards around the secondary which
increases the coupling even more.  So if you use a helical primary,
it has to be really wide and far away from the secondary, or it
will overcouple.

>  
>  would this extra distance decrease the coupling or would it matter?

Extra distance has the effect of decreasing the coupling in general,
but even with it far away, the coupling can be tight enough as 
explained above.

>  
>  it seems most of us use the 1-2" distance of primary/secondary distance to
>  prevent
>  pri/sec flashover. ( this is on conicals and flats)
>  
>  another thought .....   what do yall think about a parabolic curve instead 
> of a
>  conical? you would have the reduced coupling near the secondary form (( 
> inner
>  turns of the primary would be nearly flat or conical)) but in addition a
>  helical
>  style coupling factor at the outer edges of the primary?( more parallel to 
> the
>  secondary)

I never bother with unusual types of primaries, since the coil will
likely work the same.  But any primary which extends upwards,
makes toroid streamer strikes to the primary more likely, thus I
use only flat primaries now.

John Freau

>  
>  if any of you have any input to this id like to hear from yall before i
>  spend 40$
>  or so on tubing to try this ;)
>  
>  Scot D