I found an article online with an interesting title: "It's Time For An AM Radio Revival"...some good reading material from Stephen Winzenburg, a media professor and former broadcaster in Iowa:
http://stephenwinzenburg.com/yahoo_...Its_Time_for_an_AM_Radio_Revival.36365953.pdf
http://stephenwinzenburg.com/yahoo_...Its_Time_for_an_AM_Radio_Revival.36365953.pdf