Turns your entire house into an antenna that radiates across useful frequencies. Like whispering between two people while a tornado siren is going off 100 feet away.

"Unfortunately these devices tend to wipe out almost the entire HF spectrum for anyone listening nearby. As household powerline cables are not shielded for RF emissions they radiate in the HF spectrum quite heavily."

https://www.rtl-sdr.com/showing-the-hf-interference-problem-...

https://www.youtube.com/watch?v=6IW3FVhHR58

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.

Think of every wire that connects your outlets together, generally these are pretty long. Powerline Ethernet turns those wires into antennas so you get things like this[1].

When you're talking about radio waves there's two power measurements PEP and ERP. PEP is roughly what wattage a radio is spec'd at. ERP is PEP * Antenna Gain, so your long runs of wire make them a high gain antenna.

To use a poor car analogy PEP = horsepower, ERP = 0-60mph. Powerline is a motorcycle, not a lot of HP but still stupid quick(loud).

What makes this even worse is that since your wires are different length is means the noise is pretty wide-band(every frequency) and so it's not something that can be easily filtered.

[1] https://youtu.be/6IW3FVhHR58?t=91