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RE: [TCML] Bi-Polar TC

Hi John,

I plan to wind a small 1/2wave. I have seen Dr' Spark's in Arizona - a
really nice one- and noticed he had a gap in the center winding which was my
plan as it allows for coupling adjustment.

I am a bit confused about the center point ground while understanding the
value in doing so. Is the center RF grounded (which takes away from the
advantage of a 1/2 wave) or?

Jim Mora

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of futuret@xxxxxxx
Sent: Thursday, February 12, 2009 4:37 PM
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Bi-Polar TC


My guess is that when you used the continuous secondary coil,
then the coupling was too tight between primary and secondary.
By making the secondary non-continuous, you reduced the coupling.
If you instead made the primary larger in diameter, that would have
also reduced the coupling, then a continuous secondary would
work OK.  I'm saying that it's a matter of achieving correct coupling, 
this can be achieved in more than one way.

Regarding the midoint grounding, this keeps the voltages balanced.
Without the ground, the voltage shifts to one side or the other
depending on arc-loading from either end, and this can cause flash-overs
between primary and secondary.  It gives the impression of a too-tight


-----Original Message-----
From: Weinhold Shannon L <Shannon.L.Weinhold@xxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Thu, 12 Feb 2009 4:15 pm
Subject: RE: [TCML] Bi-Polar TC

I have a pretty nice bipolar coil one that I built a while back.
I learned a lot about them, and I'm still tweaking it as I go.
Bipolars are very flexible in that there are a variety of effects you
can achieve with them.
I had someone recently ask me about mine, and how I mounted the
secondary, having seen it on youtube.
I don't know if that's you or not.  If not, go to youtube and search for
"capacitive coupling" and tesla and it should come up.
You can also look me up by my profile, which was moneraths but is now
Klasdja. I don't know which brings it up, as youtube seems to be holding
on to them both in some fashion.
Note that the video was taken in the early stages of development, and is
much refined in appearance since then. Email me if you'd like to see a
current pic of it.
So on mine - I found some nice looking towel holders that seemed like
they would fit the bill as secondary mounts. I painted them black and
they looked pretty sharp.
I used two lantern globes (glass tubes) that fit perfectly around the
secondary, as both insulation and a spacer to bridge the gap between the
secondary and the secondary holders.
I used a painted coupling section of pvc as my primary former, and
utilized some solid foam epoxied in place as a spacer between the
primary former and the glass enclosing the secondary.
One key point with these, breakout will take place along the secondary
if there is no coupling of some kind between the outputs, unless the
power is low and the spark gap is narrow.
I used a 15/30 nst to run it, and it runs it quite nicely with the gap
open wide, or you can obtain much more mellow effects with the gap
fairly narrow.
Key point number two, don't run a continuous coil length for your
secondary. It needs to be two separate coils, and the center should be
connected to the center of your primary.
I had read that it should be grounded to earth at the center, but it
completely ceases to function if you do this. I didn't know that the
secondary should be broken up initially, and had to cut my coil in the
middle and unwrap about 1/4" of turns and center tap it, and it worked
much better after I did this.
Performance will be less than you're used to for whatever sized
secondary you use, because  you really have two small secondaries rather
than one continuous coil, but the coupling is too great without the
midpoint grounding to primary, unless you have a really large primary
Hope that helps.

Shannon Weinhold
Coffee Creek Correctional Facility
Behavioral Health Services
Mental Health Infirmary

"The problems of today cannot be solved by thinking the way we thought
when we created them."
-Albert Einstein

-----Original Message-----
From: jhowson4@xxxxxxxxxxx [mailto:jhowson4@xxxxxxxxxxx]
Sent: Wednesday, February 11, 2009 6:42 AM
To: tesla list
Subject: [TCML] Bi-Polar TC

Hey Guys I was wondering if i could pick your brains about the bipolar
Tesla coil. Specifically what the best way to mount the secondary Like
this would be. I am planning on making a small 9kv 30ma coil over the

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