I have a ZyXEL 500Mbps powerline ethernet adapter and when I plug it into the wall and my wireless router, the connection speed to the internet degrades and eventually I get less than 1mbps down/up speeds. Without the powerline adapter plugged in, I get around 60 down/ 20 up (pay for 50 down 10 up). I get these speeds when I am connected directly to the modem, connected to the router, connected over wifi and when connected over the powerline ethernet cable when I first plug in the powerline adapter. Over the course of a couple hours or so, the speed of all of these connections degrades to sub-1Mbps speeds. If I disconnect the Ethernet powerline adapter and reset the modem/router, the regular high speed comes back.
Also - I transferred a couple files between two computers on my local network while the speeds were slow and it was decently fast - pretty much the same speed as when the internet has full speed. It seems the LAN is not affected by this issue...
I have Cox internet service in Phoenix. My modem is a Motorola SB6141. My router is an Asus AC66U. The powerline ethernet adapter is a ZyXEL PLA4225 500Mbps.
If anyone has any idea what might be causing the internet signal to degrade or what I might be able to do to fix this issue, It would be a big help!