*See the 600m section of http://showcase.netins.net/web/wallio/600m.htm and then ask Fritz for use of his SNRD software to estimate 630m ground-wave propagation. See https://www.fcc.gov/encyclopedia/m3-map-effective-ground-conductivity-united-states-wall-sized-map-am-broadcast-stations for a Ground Conductivity map. -- Ralph W0RPK *