Comcast XFINITY → [Connectivity] Troublesome signal level on Arris TG1682G? [ screenshot ]

Random thoughts.

Do you, perhaps, have an amp somewhere? The upstream power levels are at the low end, which sometimes happens when one uses some amps with upstream amplification, and a too low power can cause issues (your modem is too "quiet" for its signal to get over the noise floor).

Your high frequency dropoff is a bit high (for only 50' of RG-6), and as Comcast usually expects one to use at least one splitter (between the TV and the modem), those power levels are below what they nominally would find as acceptable at an install.

I would connect the modem directly (or as close as possible) at the demark (the Comcast box) and verify that the levels are "interesting" there. If so, call Comcast for a visit. If it is good there, there is something wrong with your cabling.

Never use a coupler in an outside environment if the coupler, and the connectors on the cable, and the cable itself, are not rated appropriately, for you will have problems (eventually).

Do the logs indicate various timeouts (ranging, etc.) that might suggest the actual reason for the outages?

I think it's time for a tech visit.

The tilt on your downstream looks bad.

Upstream power levels are low as well.

First, the downstream power is reasonably OK at the demark.

But, they indicate that that 50' cable (or the barrel connector) is crap (there is 6-7dB drop over the 50' you mentioned. You should expect to see a little over 2dB for reasonable quality RG-6). At least if this 50' cable is normally connected to the same location. If it is being feed from some other splitters or other devices, it could also be any of those.

Unfortunately, this time your modem did not choose the 651MHz downstream, so it is not possible to know the power for that downstream (which would indicate if you are not getting a proper signal into your residence; given the 50' RG-6 is crap, perhaps it is the cause of the higher frequency losses, so it may not be Comcast's issue).

The upstream power is still lower than is usually reliable.

The logs might be useful (which I will expect to show ranging/timeout errors, due to the low upstream power numbers, but there may be other things of interest there).

Unfortunately, with the latest firmware update, the logs in the TG1682G have been rendered useless, there is absolutely no info in there at all, system,event and firewall...Not that there was much of any use in there before the update...LOL!

I'm the original poster. I submitted a ticket to Comcast via the
DSL Reports Comcast Direct forum. I'll post the outcome here,
and I forget to do so, please remind me.

The ticket is multiple paragraphs long. But its core statement
is that the TG1682G's screenshot at the house's main Comcast
box seems to indicate that the upstream power levels are too
low for a dependable connection.