First light - sort of

To: tesla-at-pupman-dot-com
Subject: First light - sort of
From: "Ron West" <ronwes1-at-juno-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sat, 19 Feb 2000 12:51:49 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

I had somewhat puzzling results with my new coil last night.  The first
thing I should say is that I am building this coil in two stages:

First stage, I built it with a VERY low power source (anyone familiar
with the "Solid State Tesla Coil" plans in the Nov. '99 Popular
Electronics? - 24 volt transformer stepped up by two auto ignition
coils).  I did this to learn the priciples and safety involved in
building a coil and as an introduction into HV before jumping in with
something larger.  My coil has a primary with 11.5 turns of 1/4" copper
tubing wound with inside diameter of 7" and outside of 18".  Secondary is
4" coil form with 21.2" of 22AWG polyester-amide-imide magnet wire.  Cap
is two series-connected Glasmike mylar caps totaling 27,500 volts 25nF. 
Voltage out from the ignition coils is about 12KV but I have no idea what
the current is.  Torroid is 4" X 12" aluminum ducting.  I went all out on
my ground, I have 5 - 8' copper clad rods spaced at 8' interconnected
with 4 AWG bare copper wire and connected to the coils via 2" wide copper
strap.

Second stage, to use the coil (primary and secondary coils and the base)
as a "stepping stone".  I plan to upgrade this to a 'real' coil with NST
power source, MMC, improved spark gap, etc.

I had expected to have 6" - 8" streamers (according to the article) but
only got 4" sparks with some corona visible on a ground wire held near
the toroid at about 6".  This may be all this coil is capable of (and it
may already be time to proceed with stage 2), but it brings up a few
questions I hope somebody can answer.

When tuning it seems to tune at (only) 4 turns.  I had expected it to end
up closer to 8+ turns.  Is this somehow related to the low power, or is
it simply a result of the frequency of the secondary?  In other words
when I change to my NST will I need to re-tune to more turns?

Could the torroid be too large or two small for the coil?  I tried the
coil without the torroid and the sparks were only about 1" in length
instead of the 4".  So the torroid does seem to be doing it's job, but
maybe it could be more efficient?

Thanks to everyone for a great list,
Ron West