No it doesn't. Powerline adapters lay a signal over AC. There was talk of using the earth pole as well as the mains circuit to increase speeds, not sure what happened with that though.
This.
Powerline networking works by superimposing a high-frequency radio signal onto the mains, and then using that to transmit the ethernet data. It can't do that on earth, because earth is already tied to ground, so it uses Line (or "live") to do it.
My experience of it is that it can work surprisingly well, especially when you think that what you're doing is to put a fairly small signal onto a wire carrying a high voltage, and connected to all kinds of electrically noisy devices. There are some caveats, though...
- Don't plug powerline adapters into extension leads - I have seen significant degradation in performance and reliability with these when they're plugged in other than to a wall socket. This might be an RF problem, in that all those trailing wires then become antennae, either picking up or radiating RF signals which is interfering with the data, or reducing its range;
- Not all house wiring is equal - it can be difficult, sometimes, to get a decent connection between powerline adapters on different circuits if they're at the "far" end of the circuit. That might be something to do with the way the wiring has been installed - it might be just fine for carrying big meaty mains current, but presents a challenge to RF - or simply that the sheer range, in from the far end of one loop, through the consumer unit, and back out through to the far end of another. I tried to connect to the shed at the bottom of the garden over powerline (about 30 metres from house to shed) and found that, while they could negotiate a connection, it was rarely good enough to be usable.
- Some powerline adapters are better than others - I've used TP-Link and some no-name (or can't remember) brand, which had the advantage of a socket on the front. The TP-Links were far more reliable under all circumstances than the latter. I can still use it, but only for shorter hops.
I am not 100% sure, but I think that the way the powerline network operates is that all stations negotiate with each other, which means that, if you've got a connection issue, just plugging in another adapter somewhere "between" the others (so, probably nearer the CU on one of the circuits) can improve things, as it acts as a kind of relay. I haven't tested this exhaustively, but I did notice an effect that seemed to bear this out when I was networking an office with quite widespread circuits, which could have been this "relay" effect.
The big downside with powerline is that, if you have any friends or neighbours with an interest in short-wave radio,
don't tell them you're using it. Because they will hate you. And say rude things about it (and, possibly, you). The frequencies it uses do clash with some of the frequencies used by radio amateurs and the like, and they get very annoyed about it.
