My cable modem drops out every time it snows or gets real cold. I have given up getting Comcast out so have decided to DIY. Cable guys are even more unreliable than plumbers or semi-professsional plumbing designers in the US, which is
really saying something. I've had guys come out, fail to do the repairs and promise a "line man" that never came.
After replacing all of the cable and all of the connectors myself, my last ditch effort is to use an Active return amplifier.
My downstream signal was too weak on the modem so I tried a passive return amp to boost this. This worked great on everything except the cable modem which then had to work too hard to send a signal back. It was shouting too loud to be heard.
Hopefully an active return amp (more expensive) will resolve my cold weather issues. I have bought an Electroline EDA-FT08300. Wish me luck.
Your modem upstream level should never go above 55. Most of the time you can access the modem diagnostics by going to
http://192.168.100.1/ and look for the 'return path' or 'upstream power'. While on this page you can check your downstream signal level (forward path or downstream) and it should be between -10 and +10 (some companies allow -15 to +15 while others like -8 to +8).
Most installers would argue that a cable modem never be on a split connection if this can be avoided.