This question came to mind, something I haven't seen mentioned anywhere I've read.
Do Part 15 AM stations skip, meaning are they ever heard well outside of their usual coverage areas at night? That goes for 100 mW, or even carrier current stations, like schools use. I'd think schools would be good dx targets as known stations that would operate every night.
As it starts to get dark, I can hear fading effects on even local stations at the high end of the band inside the red circle on radio-locator, so why not .1 watt?