Measurement questions

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

Original poster: "J. B. Weazle McCreath by way of Terry Fritz <twftesla-at-uswest-dot-net>" <weazle-at-hurontel.on.ca>


Hello Coilers,

I took some measurements on my first coil, which I built long before I
was aware of this list and hence uninformed, and the results have me a
bit puzzled.

Some coil details first:

Top Load  - Sphere roughly 6" dia. (8.52 pF. from WinTesla)
Secondary - 3" x 13.5" of no. 22 (3.65 mH. from WinTesla)
Primary   - 7.5 turns of 1/4" tubing, spaced 1/4" with
            60 deg. conical! (.0086 mH. from WinTesla)
Capacitor - Glass & aluminum plates in oil (6 nF. measured)
Gap Type  - Two 1.5" disks spaced about 0.15" with fan
Power     - 10 K.V. -at- 23 mA. (one OBIT)
Frequency - 698 kHz. (from WinTesla)

Using Terry's method of finding mutual inductance I measured
a primary current of 9 amps and a secondary voltage of 110
millivolts across the 10 K resistor, 1 uF. cap as suggested.
If my calculator got it right then my M = 38 uH. or .038 mH.

Applying that figure plus the values of Lp and Ls from above
I get 0.2212 as my K figure yet WinTesla gives 0.75 as the K.
I expected to see a bit of a difference, but not that much!

Could this be due to my extreme primary angle?  Like I said,
this coil was built before I knew the facts.  I didn't make
the same mistake (and others) on my subsequent coils!


73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
           or ve3ear-at-rac.ca
Web site:  www.hurontel.on.ca/~weazle