Because I live in the sticks, I don't get much PL or other interference.
Until last year, when I was plagued with a huge amount of broadband hash for virtually the whole spread of HF.
The culprits were a dodgy LED dimmer, a dodgy LED lamp and the really broad hash was coming from my LAN.
I binned the dimmer and LED, and put ferrite rings around every end of the LAN cables - about 9 turns each end.
The noise went from a steady S7 down to S1 and lower. There's still the odd splash and warble here and there, but I can live with it. Most recently, a cheapo PSU started playing up and I was able to quickly isolate that as the cause - while it lasted, it was fierce.
If I was still living in a town, I'd be driven to drink by neighbours' noisy appliances, I think.