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