The link below leads to a plot of field intensity vs distance for a Part 15 AM transmitter using a high-efficiency circuit as its final r-f amplifier, for the assumptions and conditions shown.
This configuration is functionally compliant with Part 15.219.
http://i62.photobucket.com/albums/h85/rfry-100/Coverage-Hi_Eff_Part15_AM.jpg
This configuration is functionally compliant with Part 15.219.
http://i62.photobucket.com/albums/h85/rfry-100/Coverage-Hi_Eff_Part15_AM.jpg