I've just moved and brought my equipment over to the new place myself. There is only one coax line/outlet though and I have a modem (Arris Surfboard) and the cable box (new small X1 box with no digital display). Each item works with a direct run from the outlet.
I've tried running the cable from the outlet to the cable box and then using the cable out port on the cable box to run it to the modem, and also tried using a basic 2 way splitter, but in the first case the modem wasn't receiving a signal, and with the splitter, whichever one I connect first works, but not the second item.
Is it worth trying a better splitter than the one I have (https://www.amazon.com/GE-Digital-2-Way-Coaxial-Splitter/dp/B0054EILOE/), or an amplified splitter? If so, any recommendations?
No, I actually just ended up switching out the cables, which were admittedly old and had been crunched up in a box a long time, and then it worked fine with the splitter I already had.