I would strongly advise against using powerline.
At least if you have no detailed knowledge about your electric configuration topology. For example, there are still some 127V networks in some regions of Europe. The 220V you get from these are not true 220V to ground, instead this is the differential of two phases shifted 120 degrees, as PacketMan described. These have no real ground connection because the currents flow between two floating phases, and powerline will perform poorly because it has to go through the transformer and side channels like appliances. This will result in poor and inconstant performance, if it works at all.
Another possible problem results in that if your house is supplied with three phases, they could be distributed differently for load balancing. For example, if L1 supplies room A and L2 supplies room B, you won't get a powerline connection working (except maybe poor connection via side channels like three-phase appliances, heaters and the like ).
But the worst thing is that it can make heavy radio interferences, and if somebody complains about, say, bad radio reception, the local authorities can find where this comes from.
And if they find it's your powerline ethernet, you are responsible, and will have not only to pay a fine, but also get prohibited to use that again, possibly even getting your equipment confiscated.
Your local jusrisdiction might be slightly different, but afaik it's the same all over the world. If you are responsible, you have to pay.
This is the reason why there exist no such things which insert an additional networking band into a broadband cable. It would cause many issues, as it would inevitably distort the whole cable segment, causing much anger with people still using analog TV etc. This would be as punishable as causing distortions via RF emissions using powerline, as described above.
As SirDice said, coaxial ethernet is history, 10Base2, using RG58 or the like with 50 ohms impedance.
I had to maintain a big network of a German newspaper a quarter of a century ago. Total length of cabling was about a kilometer, with about 100 computers connected.
It was horrible task. So many possibilities for things to go wrong. And things went wrong often.
Bad terminations, weak connections, damages in the cables, defective network cards or MAUs. A single of these problems could put a whole segment of the network out of operation.
Luckily I had a specialized ethernet tester, showing problems like this, open connections, shorts, bad terminations etc and indicating the cable distance where the problem was.
When a problem occurred, I had to rush, as often dozens of journalists were waiting for me to find and fix the problem asap. This was quite stressy, as the premises were quite big.
For example, one day some plumbers drilled holes in the walls, and drilled into a cable. I had to hurriedly lay almost 100m temporary cabling through the stairways, connecting the remote floor to the servers again.
This I'd really suggest to lay an additional twisted pair ethernet cable. But, make sure to cut the grounding of the cable if your electric installation has no separate ground connection, which is often the case with older installations which have floating grounds.
At least if you have no detailed knowledge about your electric configuration topology. For example, there are still some 127V networks in some regions of Europe. The 220V you get from these are not true 220V to ground, instead this is the differential of two phases shifted 120 degrees, as PacketMan described. These have no real ground connection because the currents flow between two floating phases, and powerline will perform poorly because it has to go through the transformer and side channels like appliances. This will result in poor and inconstant performance, if it works at all.
Another possible problem results in that if your house is supplied with three phases, they could be distributed differently for load balancing. For example, if L1 supplies room A and L2 supplies room B, you won't get a powerline connection working (except maybe poor connection via side channels like three-phase appliances, heaters and the like ).
But the worst thing is that it can make heavy radio interferences, and if somebody complains about, say, bad radio reception, the local authorities can find where this comes from.
And if they find it's your powerline ethernet, you are responsible, and will have not only to pay a fine, but also get prohibited to use that again, possibly even getting your equipment confiscated.
Your local jusrisdiction might be slightly different, but afaik it's the same all over the world. If you are responsible, you have to pay.
This is the reason why there exist no such things which insert an additional networking band into a broadband cable. It would cause many issues, as it would inevitably distort the whole cable segment, causing much anger with people still using analog TV etc. This would be as punishable as causing distortions via RF emissions using powerline, as described above.
As SirDice said, coaxial ethernet is history, 10Base2, using RG58 or the like with 50 ohms impedance.
I had to maintain a big network of a German newspaper a quarter of a century ago. Total length of cabling was about a kilometer, with about 100 computers connected.
It was horrible task. So many possibilities for things to go wrong. And things went wrong often.
Bad terminations, weak connections, damages in the cables, defective network cards or MAUs. A single of these problems could put a whole segment of the network out of operation.
Luckily I had a specialized ethernet tester, showing problems like this, open connections, shorts, bad terminations etc and indicating the cable distance where the problem was.
When a problem occurred, I had to rush, as often dozens of journalists were waiting for me to find and fix the problem asap. This was quite stressy, as the premises were quite big.
For example, one day some plumbers drilled holes in the walls, and drilled into a cable. I had to hurriedly lay almost 100m temporary cabling through the stairways, connecting the remote floor to the servers again.
This I'd really suggest to lay an additional twisted pair ethernet cable. But, make sure to cut the grounding of the cable if your electric installation has no separate ground connection, which is often the case with older installations which have floating grounds.