Hello Walt
Having just done a quick Internet search I have come up with an
interesting site:
www.qsl.net/sv1xv/lf.htm
The site is called 'the world below 535 kilohertz'
It has a load of links which I don't have time to explore at present.
One mention is of the LFCA - Low Frequency Club of America - these
bits of information may help you further.
73
--
David W Wood