I've always been curious about this, but I wasn't alive at the time to ever test it myself. Maybe someone here knows. 

In January 1934, WLW-AM in Cincinatti became the first (and eventually the only) station in North America allowed to broadcast at an incredible 500,000 watts. It was such a powerful signal that the Crosley-owned radio outlet was actually able to charge advertisers national rates for their programs.

You can guess what happened next - stations across the country started bombarding the FCC with requests to do the same. Eventually, in 1939, the Commission decided to restrict radio stations in the U.S. to a maximum power of just 50K - still pretty good, but not even in the same league as half a million watts. 

My question is this - while obviously this would have boomed into Toronto at night, would listeners here have been able to hear WLW during the daytime? How well would it have come in? Was it like a local or maybe something from out of town, like Buffalo? 

I can guess the signal did make it here - CFRB, which at the time was on neighbouring 690 AM - complained constantly about the Cincinatti giant's interference with its signal and WLW engineers had to reconfigure its pattern to try to fix the problem.

From an old but interesting Radio World article on the issue:

"The existence of such a powerful signal on the radio airwaves was certain to create interference. And sure enough, in the summer of 1934, the FCC began receiving complaints from the Canadian government about interference to CFRB, which operated with 10 kW on 690 kHz in Toronto, 400 miles Northeast of Cincinnati. “With station WLW operating with 500 kilowatts,” read the official complaint, “the service area of the Toronto station was reduced to little more than the city of Toronto itself, and 50 miles out the signals from Toronto were completely obliterated.”

The article goes on to explain how they fixed the problem but kept the power.

When the Ohio station eventually went back to 50,000 watts, the problems went away for good and CFRB relocated to its next frequency - 860 - in 1941. (When the CBC demanded use of that frequency, 'RB moved one last time to its current home at 1010.)

So for those who are more technically inclined than me (which is most of you!) would this 500K giant have come in here during the day? I wonder what the AM DX was like back then, with so many fewer stations and so much less electrical noise on the dial.

Image courtesy Wikipedia