To address Dave Burnham's original post, which I somehow missed:

> Theoretically AM broadcasting should be capable of a 5k bandwidth.

According to historian Fred Krock, up until the mid-1940s, network radio 
actually carried a maximum of 8k bandwidth. Station crowding wasn't as 
much of a problem as it is today, I suppose.

http://bayarearadio.org/schneider/netsnd.shtml

Michael Shoshani
Chicago