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Re: How much does aspect ratio of secondary really matter (is it all about K factor)?

Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>

The low 2:1 ratio might present some tempting sparks from top of sec to bottom of sec. Testing will tell the story. At low power you might get away with it.

Dr. Resonance

I've been crunching numbers on a low-power,
low-frequency coil, and one of the options that has
presented itself (while playing with JavaTC) is going
with an aspect ratio less than 3:1 (specifically:
2.5:1).  For whatever reason, conventional wisdom
calls this "not recommended", however going with a
short-and-fat secondary permits me to match the low
frequency of the primary (which is due to low voltage
and large primary cap) while maintaining a low
profile.  Since the coil is only going to be ~150W or
so and can't be expected to put out sparks more than
24" or so, I don't want the physical size of the coil
to promise more than it can possibly deliver ;-)  For
that reason, I'd rather grow "out" than "up".

All talk of aspect ratio that I can find seems to
center on K factor, however the K factor I get out of
JavaTC for this 2.5:1 ratio coil is 0.17, which seems
"normal" to me.  Any other gotchas associated with low
aspect ratios?  If I have coupling under control,
should I be "ok"?

Best regards,
Aaron, N7OE