Nick: Your new coil
I just visited your site last night. I noticed you are using 0.6
mm wire to wind your new secondary coil, so I decided to
fool around with a calculator and I think you might be running
into some trouble with this setup.
Diameter: 325 mm
Height: 1400 mm
Wire: 0.6 mm
L: 366 mH
H/D ratio: 4.3:1
What I was suspicious of, was the resulting DC resistance. Letīs
have a look at this.
I will assume 0.6 mm is bare wire diameter, so with enamel this
would be around 0.635 mm in diameter. (0.6 mm ~~AWG 23). I
will also 1st assume that you wound only 1300 mm of the tube
(is 1400 mm the total length or the actual winding length?).
Length per turn: PI*d or ~1.021 meters per turn.
# of turns: 1300 mm/0.635 mm ~2050 turns
Length of wire: 2050t*1.021mpt= 2093 meters of wire
AWG 23/0.635 mm wire roughly has 0.067925 ohms per meter, so
your coil has a DC resistance of ~142 ohms. This is quite high and
I could imagine your 10kV power source might have a hard time,
driving this (with 4J of input power) coil. Of course, you WILL get
sparks, but I think you will be loosing quite a bit of efficiency in
Now my question to you: Why did you go this route of using such
thin wire? For a ~13" secondary I would have used at least AWG
18, maybe even bigger. From my experience, there is no need for
an ultra high secondary inductance (My 8" has ~36 mH and 17 ohms
DC-R). In fact, a high impedance might even give you some further
headaches, when it comes to driving the toroidīs capacitance. I
would definitely stay well below ~60-70 ohms DC-R, when it comes
to the secondary coil construction.
I back calculated the inductance values with my HBTCP (homebrew
TC program) and the 366 mH seems high. With the 1300 mm
winding length used above, I get 301 mH and with the full 1400 mm
length (which would further increase DC-R) I get 325 mH. For my
coil the program was very accurate. I calculated 35.67 mH and
measured a true 36 mH (LCR meter) for my coil. Also, your
unloaded FRes is ~60 kHz. With a 6x40" toroid this will drop your
FRes (loaded) to around 36 kHz. This will require a VERY large
primary inductance (as your cap is kind of small for this sort of
FRes) in order to tune properly. This further means your primary
current wonīt be very high and your setup will (probably) need a
pretty high coupling factor. I would suggest you reduce your BPS
(simply donīt use all 12 electrodes) and go for quite a bit bigger
No offenses meant. I just thought I would mention it. Of course, I
will be awaiting your (spark) results in suspense.
Coiler greets from Germany,