Brett
I have been a AM DXer since the late 1940's Haven't done much since the band went to thousands of low power stations. I live in DX heaven now,low noise,high elevation,middle of the east coast.
I live in DX nightmare, sea level, incredible interference. On BC the best I have done is Hartford CT (not bad, about 3000 miles) in very special conditions, Zenith 6G501 w/stock Wavemagnet stuck up in the air on a long pole, and the hottest 1LA6 and 1LN5's I can get, and brand new batteries. If I go over the hill to block the local interference, at night, I can get just about any AM station in the US. That's not all that much of an accomplishment, the radio in my car - with the window-embedded antenna - can pick up Denver and Salt Lake city like they are next door. I haven't gotten anything outside the continent of North America, but that's not too surprising, the Pacific is a lot bigger than the Atlantic and Europe is out of the question from here. I have no way to put up any 1/2 mile antennas, and I suspect if I did it would just make all the CFL lights and computer oscillators that much louder. The loops like the various Wavemagnets seems to handle the interference a lot better.
I do a lot better on shortwave, Zenith Transoceanic 8g005, same hot 1LN5 and 1LA6 from the other radio, and the shortwave loop wavemagnet, although the stock vertical antenna works pretty good if the antenna loop it tuned properly. I can easily get anything in the Pacific rim on 25 and 31 meters, Voice of Russia from Vladivostok can almost be picked up on your fillings from here, Radio New Zealand and Australia, no problem, the Chinese are always blasting something (including their horrible Chinese folk music jammer), and I have gotten Radio France and Deutsche Welle in the mornings a few time. Pretty much have antipodal coverage on that one. The 8g005 works better mostly because 1LA6s are so cheap that I am willing to run the filament voltage pretty high compared to a 1L6 radio and that increases the performance quite a bit. But I think when I get my Philco 40-150 tweaked up, it might be even better, even half-restored it seems to be just about as good as an average Transoceanic, although very hard to tune.
I took a Transoceanic B600 with me when I drove down to Tucson for the SWR, and at a rest stop in Arizona at about sundown, no interference, and the sound quality and reception were both amazing.
Brett