WNAX would have to at least be in the conversation. Unlike KFYR and CBK, they're directional daytime. Also some of their signal touches the Sandhills of Nebraska, where the ground conductivity drops off dramatically. Pretty much the same story for CFTR. Directional daytime, and their signal to the east runs into the Canadian shield area, where conductivity drops from exceptional to lousy in a hurry.I wonder of there is a list of the largest service areas in the country. WNAX 570 and WMAQ 670 have to be pretty high on the list. Not sure if they use 0.5 mV/m or 0.1 mV/m to determine this.
As for WSCR (WMAQ), the ground conductivity in most of their coverage area is good. But not as good as the stations mentioned above. Also, WSCR's signal is inhibited to the east by the sand dunes and sandy soil in much of southwest Michigan. Although that said,, WSCR daytime makes it to Detroit and beyond into Ontario.

