tuning primary and harmonics

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Justin Wright by way of Terry Fritz <teslalist-at-qwest-dot-net>" <justin-at-tracesofnut-dot-com>

Hi All,

I tuned my primary coil using a freq generator and scope.  I used the
frequency that suited the secondary.  It was about 180khz.

I didn't have a freq meter, so I just left the generator running and
used the same frequency on the primary.

As I tuned the primary by moving the tap around, I found the amplitude
on the scope rising and falling at different tap points.  I guessed
these were harmonic frequencies?

Anyway, I found a tap point that made the highest single on the cro and
used than.  It was at 9.5 turns.  The coil works fine with this.

When I later keyed in the figures into WinTesla, it reported the tap
point as being just over 11 turns.

I didn't try this far out when tuning the primary, so I am wondering if
I had just found another harmonic at 9.5 turns.

Are there a lot of places around the primary that will create a large
signal on the scope?  Has anyone else found multiple tap points that
make a coil work ok?

I plan to test this when the weather improves.


My coils specs are...


Secondary:
110mm (4.33") pvc
860mm (33.85") of 0.63 enamelled copper
150x300mm (6"x12") topload - 450mm (18") total diameter

Primary:
11 and a bit turns of 6mm (0.236") copper tubing at 6mm spacing
19.4 nf MMC (0.33uf x 17 -at- 1600v)

Static Spark Gap
15kv at 60, 90 and 150ma