I suspect KSIB Creston IA 1 kW true daytimer on 1520 gets hammered in the same manner by KOKC (KOMA) during critical hours. But, KSIB also has a 25 kW FM that probably handles most of their listenership.
When I was in college during the late '60s in southeast Iowa (Mount Pleasant), I was well out of range from KSIB, and never heard it.
During the day, 1520 was basically blank. There was a 1510, WKAI from Macomb, IL, about 60 miles away from me. 500 watts ND, IIRC. Still listenable, but not a factor in terms of generating splatter. (The 1510 in Macomb is still going, but with different call letters).
Usually, what would happen during late afternoons in winter, is that KOLM with 10kw from Rochester Minnesota, would be the first station to roll in during CH. Format was the same as KOMA (top 40), so for a few minutes, you might not be sure what you had. Eventually, KOMA on day ND pattern would start trashing KOLM , and finally take over completely. KOLM would then sign off, and not long after that, KOMA would power down, but still be listenable with a good signal. Alone, save for an occasional whiff of WKBW either during KOMA fades or underneath.
Back to 1510, WKAI....as you might expect, WLAC would clobber them at my locations during those late afternoons. But of course, we were well beyond their intended service area.