Behold, qrk signalled from keyed 4-1000A filament:


Air-core my good man, air-core ;-)

Try air-core with 500+ uH. Then pack em in to a small area. That's what
I get for being a low-freq weenie.

Ah! I too am a LowFER - Made a 6Hy coil in about 4 sq. inches on my
winding jig. No current capacity but a great 20-76KHz preselect for the
vacuum tube RX :-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca