[vvanders]

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