Pixellation is 100% the fault of the splitter or cabling/connections
if using a no-name splitter this is probably the problem, use a Tratec, Technetix or Labgear, other splitters than these aren't suitable or VM.
long cables/poor quality cables can also cause this, check ebay for Tratec cables with moulded green ends, these are excellent quality and fairly cheap
If you want to check power levels and SNR in the router:
on the bottom of the router is a 'settings password' write it down
open a browser window on laptop and type 192.168.0.1, click enter
use that password to login to the router
click Advanced settings on the left, then tools>network status
this opens a new page, click Downstream tab at the top and it'll show all the data in a list
copy and paste it here