Here is a list of links to other LF/MF websites of interest:

• Long Wave Lowdown site.  This site provides a LOT of information about Lowfer operations.
• Non-Directional Beacon (NDB) list by country.  NDBs are useful for receiver testing.
• North Amreica Beacon list by William Hepburn.
• Various LF/MF/other useful information and links by W6/PA0ZN
• W4DEX (Part 5 epxerimenter) website
• G0MRF web site.  Lots of LF/MF information, including amplifiers, exciters, antenna tuning, etc.
• George, M1GEO site, includes 472kHz antenna and EIRP calculator info.  George provides some information on calculating EIRP, and shows a 473 kHz antenna he implemented in his yard.  Check out his 472 kHz page.
• John Langridge, KB5NJD and WG2XIQ web site.  John has good information on operating on both the 630 meter and 2200 meter bands.  He also has a 100W amplifier and transmit downconverter for sale at reasonable prices.