Regularly spaced carriers like that are often caused by radiation from TV receivers. That kind of RFI shows up here, too, although I haven't checked the exact spacing. I don't watch TV or even have a TV here in my apartment, but there's an unused live cable outlet, and I'm sure my neighbors watch TV. In fact, one of them has a TV with a 54-inch screen. One clue is that the interference doesn't start until the early evening, which is when most people switch on their TVs.
The RFI may be due to poorly shielded TV cables, radiation coming directly from the TV sets, or both. At any rate, it's a real nuisance. Even this computer sitting right next to my receiver doesn't cause that much interference, and my antenna is indoors!