nimicitor

My internet has only started to work when I connect the modem directly the black cable that goes outside, bypassing the white cable and isolator.
Ive tested it all using a spare white cable and the same isolator and it still didnt work which leads me to believe that its the problem.
Do I NEED the isolator or can I just go and buy a converter so I can attach the black and white wires directly?
If not then whats then whats a good model to buy (i don't want an engineer out)?
I have a VQ302LC at the moment and its huge.
I don't need a splitter as I only use the internet is this room.

Thanks for any help