First, is this only with sideband or also with AM? Typically noise is worse for AM. I don't know how noise blanking works on that radio but it could be it doesn't work well or at all on SSB.
Now then, assuming the noise is being received and it's not a radio problem, the sources of noise are many. You'll find dozens of threads on this subject in the Amateur Radio section. Here's some examples, Ethernet router, Internet gateway, washing machine (seriously, the new electronic controls can do this), furnace (same deal), computer monitors, TV sets (plasma sets generate monstrous noise), thermostats, switch mode power supplies (which is just about everything that plugs in these days, phone chargers, game consoles, stereos, power tools) ... you have to turn everything off, switch off circuit breakers. Then listen, if the noise is gone you know it's in your place, which is almost always the case. Then turn stuff back on until you find what it causing it. Power line noise is an issue but the most likely culprit is a piece of equipment you have. If it is indeed power line noise then next thing to do is carry a portable AM radio around the neighborhood listening for this noise. If you can find the source you can contact the power company. They're glad to hear about it. But, just because you hear it the worst in a spot doesn't mean that's the source.
