@Ghorghor All Deco units can be mixed and matched, so if you have new wiring, what you probably could do is to get you a pair of Deco P7  (AV600 powerline) or P9 (AV1000 powerline), they use powerline as a backhaul and this could help you to get the signal to the extension not by using WiFi but with the help of the powerline backhaul. This backhaul would also work with Ethernet connection, although, I suppose you do not run an Ethernet cable from your house to the extension.

If you connect your M4 with an ethernet cable, they will use Ethernet as backhaul. You can check for this in the Deco app.

Have you tried other electrical sockets with your existing powerline? Also do not use any powerstrips, PCL need to go directly into the wall socket.

@StardustOne I moved the M4 next to the door of the extension a it works better (around 1/3 of wired connection speed).

Do you think a P7 or P9 could really improve this?

BTW, I followed all guidelines for placement of CPL and I don't understand why it doesn't work well in the extension (I tested all electrical sockets) but that's another story.

Thanks for your time and advices.

Ghorghor

@Ghorghor Well the P7 uses AV600 and the P9 has AV1000, so from the starting point for AV600 or AV1000 devices, connection speed goes only down, the higher you start, the more you will have at the end point. I do not know what AV speed your PLC has, but keep in mind the P7 CPL function only works as a backhaul, meaning that the P7 or P9 themselves do not integrate themselves into your CPL network, they operate independently from your other CPL.

If you already own AV1000 or faster CPL devices, the P7 or P9 would probably not bring much benefit. If you own something that is lower than AV600, it may well be worth to try the P7 or P9 (whatever comes cheaper).