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On 4/4/14 8:42 AM, Phil Tuck wrote:
Teslalabor wrote: "it is completely useless"
No no, I wouldn't that!
True the streamers have a capacitance of a couple of pf / foot to upset
things, but the scope method gives a very good estimate and the smaller the
coil the more accurate it should be - less output, less effect.
You simply use the 'wire' method mentioned and then compare the difference
with and without the wire. I tune the primary around 8% lower, (82 down to
74 KHz approx)
Only trouble with the scope method is that you get harmonics show up as
well, so doing a sweep involves looking for the highest amongst the several
peaks that will occur. Using JavaTC beforehand will tell you the figure
reasonably accurately as a guide though, to avoid mistaking a harmonic as
the correct peak.
Phil
And to echo Phil, the other thing you can check for is some egregious
error like having the topload not connected to the secondary. Oddly it
sort of works, because the "sparkgap" at the top of the secondary
connects it to the topload, sort of.
(not that I'd ever have done that, no, never, uh-uh)
measuring your secondary is also handy for other reasons: how many of
us have tried increasing Csec by piling something else on top of the
toroid (like another toroid, or a bucket, or a pumpkin, or an aluminum
christmas tree).
The wire test is also pretty instructive in general. You can see if
moving stuff around your test area causes a "significant" change in
resonant frequency.