Posted by: wfaulk
Cable modem troubleshooting - 19/12/2009 18:24
Last night, my home internet access, provided via cable modem, went bad. It's still up, but I'm getting 10%-25% packet loss. We had a small ice storm yesterday, and I would be surprised if it wasn't a major culprit.
So this morning, I went outside to my demarc to see if there was anything that looked storm damaged. Nothing storm-related really jumped out at me, but I noticed that the grounding wire had snapped off of the coupler, and there was generally a lot of corrosion. There was no lightning in the storm, so I don't think that the lack of a ground fried the modem, and the corrosion might have been dessicated dielectric grease.
The connections were like this: the cable from Time Warner was connected to a coupler, which is where the ground was/would have been attached. There was a 6 inch cable running from the coupler to the input of a 3-way splitter. There were cables attached to all three outputs, but only one of those is attached inside the house. I don't know which is which, sadly. The splitter was marked to show -7dB on two of the outputs and -3.5dB on the third.
I figured a reasonable idea was to connect the cable modem's line directly to the main cable, and lose the splitter. Figuring that it would be easy enough just to try all three cables, I connected one of them up. It didn't seem to work, so I connected the second. It also didn't work, and I connected the third, which still didn't work. I played with a lot of things before I gave up and just put it back the way it was. At which point, my internet service came back up, with about the same signal quality as before.
So what I want to know is: is there some reason that it would work going through the splitter, but not when hooked up directly? Obviously, it's easy enough now to figure out which cable is which; I can just unplug them one at a time until my service goes out. But I tried all three. Why would it fail that way?
So this morning, I went outside to my demarc to see if there was anything that looked storm damaged. Nothing storm-related really jumped out at me, but I noticed that the grounding wire had snapped off of the coupler, and there was generally a lot of corrosion. There was no lightning in the storm, so I don't think that the lack of a ground fried the modem, and the corrosion might have been dessicated dielectric grease.
The connections were like this: the cable from Time Warner was connected to a coupler, which is where the ground was/would have been attached. There was a 6 inch cable running from the coupler to the input of a 3-way splitter. There were cables attached to all three outputs, but only one of those is attached inside the house. I don't know which is which, sadly. The splitter was marked to show -7dB on two of the outputs and -3.5dB on the third.
I figured a reasonable idea was to connect the cable modem's line directly to the main cable, and lose the splitter. Figuring that it would be easy enough just to try all three cables, I connected one of them up. It didn't seem to work, so I connected the second. It also didn't work, and I connected the third, which still didn't work. I played with a lot of things before I gave up and just put it back the way it was. At which point, my internet service came back up, with about the same signal quality as before.
So what I want to know is: is there some reason that it would work going through the splitter, but not when hooked up directly? Obviously, it's easy enough now to figure out which cable is which; I can just unplug them one at a time until my service goes out. But I tried all three. Why would it fail that way?