Is it the cable modem or the cable company


I have a Motorola SB6120 cable modem that I bought last November or December. It's been working great since I got it. I have the cable modem connected to an APC surge protector and turn the surge protector off at night to save a few pennies on electricity. About 2 weeks ago on a Thursday morning when my wife turned everything back on, there was no Internet. Stayed down all day, I played with it when I got home, and I ended up scheduling an service call for the following Saturday. Later that night, I got creative, reset the cable modem to the factory defaults, left it off for about half an hour, and when I turned it back on – Internet!

We were fine until the following Thursday (Thursday thing is weird too) then the exact same scenario. Didn't come up in the morning, stayed down all day, but this time even after trying similar tricks from previous outage, nothing got us back online. Waited to Friday morning to see what would happen over night, and after still nothing scheduled service call for following Monday. By the way, no internet all weekend – really sucks!

On Monday, tech comes out, says signal is weak, thinks cable is damaged where neighbor behind us put in fence last year. On Tuesday, repair crew comes out and does something out by fence, but still no internet. Tech comes out later that afternoon, is able to get cable company's modem online (Scientific American) but my modem won't.

I ended up calling Motorola support, and I learn the power levels the modem is reporting are too low. Upstream power is 0, signal to noise ratio in the low 20s. So he says the signal strength is too low. I start paying closer attention after that and begin to notice a pattern. When I first turn on the modem, it reports good signal strength: signal to noise of 37, downstream power of 3, upstream power of 49. But after 10-15 minutes, signal to noise drop to low 20s and upstream drops to 0.

So now I'm not sure what to do. Call the cable company and demand they fix the frickin' line? Or call Motorola and insist they RMA the modem? I don't have a way to test my modem elsewhere, so I can't really verify it's still good. Cable company says signal must be fine if their modem will connect. I've also verified they have the right mac address.

Best Answer

If the signal drops in a reproducible pattern after the modem has been turned on for N minutes, that suggests a problem with the modem, not the cable. The cable is essentially passive and can't tell if the modem is turned on or not.

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