20 watts over 650Km on 500 kHz band

With ROS7 MF, you can maintain communication on 500 Khz band keyboard to keyboard with a a reasonable qso speed and a extraordinary power efficiency. 

http://lfistes.erst.azerttyu.net/viewtopic.php?f=17&t=1982&sid=5f68ac5172a5c1206214df5b03c2bc50