From ARRL web site, dated 4/16/15:
The FCC has yet to act on the
ARRL’s 2012 Petition for Rulemaking asking it to create a domestic Amateur Radio allocation at 472-479 kHz, known variously as 600 meters and 630 meters.
ARRL 600 Meter Experiment Coordinator Fritz Raab, W1FR, said the mission of the multi-station experimental operation “has actually been accomplished,” but since the US still has no medium-frequency (MF) Amateur Service allocation, he believes the Experimental license ought to be renewed. The WD2XSH license is set to expire in August.
The full story is here:
http://www.arrl.org/news/arrl-600-meter-experiment-coordinator-recommends-renewing-experimental-licenseOn these frequencies, you need BIG coils: