Interference To WGN 720 In SE Michigan

I'm getting an apparent ground wave heterodyne on top of 720 of about 2 Hz in SE Michigan, seems to be close to the FI of WGN. Any ideas as to what this is? There's a station near Harrisburg, PA that has a CP for 3.9 kW. This isn't exactly Daytime Skywave Season. There is a 50 kW station in NC, but I doubt that is even it, again unless there is Daytime Skywave. I was just trying to compare the new WBBM signal to WGN and WSCR. The heterodyne seemed the strongest of the three. I don't see any new stations in Canada on 720 either.

Are you sure that is not 2 kHz? In that case you might want to be looking at first adjacents.

Nope. It's fading and increasing twice per second approximately. I think now it may be an intermodulation product of WJR 760 and CKLW 800, interfering with WGN 720. I've never heard it before, on any receiver, so I assume it's radiated, not receiver induced.

I'd say it would be the WJR transmitter. 2 X 760 = 1520 1520 - 800 = 720.

I'd say it's about 0.1 mV/m in my RL. WJR is around 20 mV/m. If it's radiated, that would be about 50000/200^2 = 50000/40000 = 1.25 watts, 46 dB down from the main signal. Should be down 80 dB at least.