Overcoupling?

• To: tesla-at-pupman-dot-com
• Subject: Overcoupling?
• From: "Alex Crow" <user-at-alexcrow.clara-dot-net> (by way of Terry Fritz <twf-at-verinet-dot-com>)
• Date: Sat, 01 May 1999 14:43:10 -0600
• Approved: twf-at-verinet-dot-com

Dear All

I was tuning up my coil again a couple of days back (I now have my other
NST back from repair and have stretched by alu duct toroid to 36" dia - 2kW
in) and at full power (2kVA) it now tunes at around 8.3 turns (WinTesla
predicted 7.6). However when I hit this tune I think that I identified
symptoms of 'double-humping' - I saw a ring of heavy inter-turn corona and
mild sparking about 3/4 of the way up the secondary, and the occasional
spark all the way down the secondary coil.

I raised the secondary up about 1/2" and this was reduced, although not
absent. The sec base is now about 1/4" above the level of the primary, and
the gap around the sec is about 1.5". My toroid's centre disc is temporary,
not covered completely with foil, so maybe this is causing probs too.

Anyone else have any experience with coupling adjustments? If you have any
advice I'd be happy - I don't want to reduce the coupling too much...

PS Spark length so far is 60", although since I am in a confined space, if
I try for beyond this, the coil seems to favour the roof beams and walls as
targets. I hope I can achieve more - do you think I can get that 6 feet??

Alex Crow

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