Re: Larger secondary more efficiency?

["Kelly & Phillipa Williams" <kellyw-at-ihug.co.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

> >I would like an 8" or larger secondary, to increase efficiency,
> >but over 6 inches PVC pipe becomes too expensive for me.
> >I asked around about cardboard tubes equivalent to sonotube,
> >(for forming concrete columns) but all I can obtain
> >is 300mm OD tube, (that's 11.8 inches). - BTW this is cheap.

> I have PVC and Sonotube coils and I like the PVC better.  The Sonotube is
> really strong but it does get frayed at the edges a little and basically
> looks like "cardboard".  We also suspect that the Sonotube is very lossy
> (if that makes a difference).  The PVC coils are rock stable and looks
good.

> However, larger diameter secondaries have higher coupling.  In this case
it
> is about .12 with the 6 inch and 0.2 with the 12 inch secondary.
>
> >
> >With 120 mA of current, can I use that large a secondary?
> >(It's all I can get )
> >I have heard that larger coils are more efficient, but surely
> >there is a cut off point where efficiency starts to drop as coil forms
> >get larger?
>
> 15kV at 120mA implies a 1.8kVA coil which should put out streamers about
72
> inches long.  So a 30 to 36 inch secondary would be fine.  I like longer
> secondaries to reduce racing arcs and primary strikes.  I would think the
6
> inch dia. would be good but you may want a conical primary to help
> coupling.  The 12 inch may have to be rasied a bit if racing arcs appear.
> If you close wind, count on having about 15-20 primary turns but run the
> numbers through one of the programs to check on all that.
>
> cheers,
>
> Terry

I must clarify here. When I say 11.8 inches, I mean diameter. I intended on
making the secondary
8" wide and 40" tall,
but 11.8" Wide is all I can get. I would keep the 40" Tall dimension.
Is this too large?

Thanks,

Alan Williams