At the last World Administrative conference a new amateur band on 630m (472-479 kHz) was authorized. Hopefully in the near future our respective FCC's will authorize amateur operation on this new band.
Other than some experimental licenses amateurs haven't been allowed below 160m for over 100 years so few amateurs have any experience with MF antennas. I've been part of the ARRL sponsored 600m experimental group for several years and over that time have built several antennas for 600 and 630m. I feel that if this band is to "take off" those of us who have been operating on MF need to share our experience. With that in mind I have begun a multi-part series of articles on antennas for 630m. Parts 1 and 2 are now available: Download 600m verticals part 1 and Download 600m verticals part 2. These two parts are mostly a NEC modeling study which is fine but we still need experimental confirmation. Part 3 of the series will be a description of actual antennas which have been built and tested. I am currently engaged in building and testing several antennas for 630m. The results should be available late this fall and will be summarized in part 3 of the series.