[Florin_Andrei]

All digital gizmos basically radiate electromagnetic energy at more or less all frequencies all the time while they're on. But some gizmos are better behaved than others, and are rather quiet. Some are total trash, and they're just "shouting" loudly across a broad interval in the RF spectrum.

If there's something like that nearby, your receiver will drown in noise, and you'll be unable to pick up faint signals from distant transmitters.

I don't know much about Powerline, but typical offenders are plasma TVs, cheap computers, etc.