LF: Linear amplifiers , MSK, and 500kHz

[Andy <actalbot@southsurf.com>]

Has anyone got anywhere with developing soundcard based MSK ?   Surely that is 
the next obvious move on LF where switch mode PAs rule and a linear PA isn't a 
realistic option for high powers, knocking PSK31 on the head.
Just as a novel test (at very low poer of course :-) I tried tuning up the T 
antenna at 500kHz.  A variometer purchased at a junk sale a few years ago - an 
old NDB thing I guess, that tunes over 100 to 400nH, worked instantly, and I 
had about 30 - 40 ohms antenna resistance at resonance.
Any moves on that band ???

Andy  G4JNT