Home Networking Filter: Why do I have to keep resetting my cable modem?

September 26, 2006 4:23 PM

Internet access at home comes and goes, but can be resolved by resetting (powering on/off) the cable modem. Sometimes has to be done once a day, sometimes once every 30mins. No obvious pattern. What could be causing this?

The cable modem is plugged into an Apple Airport Express, which I've had for over a year and have never had problem with before. I recently moved and the new cable hookup (though same company as before) has been relatively flakey. Sometimes I have to reset the modem, sometimes the Airport Express. I've tried fiddling with the settings -- different channels, b and/or g, different security options, nothing seems to consistently fix the problem. I'm using a Powerbook G4 under OS 10.4, but my roommate is running WinXP and has the same problems. Resetting the modem almost always seems to temporarily fix the problem but there is no obvious pattern as to how long is required until I have to reset again.

posted by modernnomad to computers & internet (15 comments total)

Is there perchance a filter at the base of the cable line, where it screws into the wall? This isn't immediately obvious, but the prior tenant of my apartment had an old notch filter installed on the line, and I was having the same issues you describe. Once I noticed it and took off the filter (at the cable company's recommendation), all was golden.
posted by mykescipark at 4:30 PM on September 26, 2006

Do you have splitters on the line? Try replacing the splitters with ones you can get for free at the cable co and have extras on hand.
posted by bigdave at 4:38 PM on September 26, 2006

It's probably a signal problem. The randomness can be attributed to temperature (the warmer it is, the more the cables on the poll and from the poll to your house stretch. Thus more signal is needed to get to your modem).

Simplest solution is to have your cable company send out a tech to throw a meter on the line.

Things you can do in the meantime which will help: If you have any splitters, get rid of them (temporally.) See if it improves. Splitters go bad, especially the cheap gold ones you get at Radio Shack. If it does turn out to be a splitter problem, make sure when you replace it you get one in the right signal range (in my area it's 711mhz, but we just changed over from 585mhz). These splitters tend to be a little more expensive. $10 as opposed to $2. But it's worth it.

If you have a guy from the cable co. come out, he will have the right kind of splitter as well.
posted by quin at 4:39 PM on September 26, 2006

ALso, you may need a digital booster to raise the signal. Heloed me considerably. Or have the cable company boost the signal outside.
posted by JohnnyGunn at 4:39 PM on September 26, 2006

get rid of them (temporally.)

Heh, yeah. I want you to go in and get rid of them using nothing but the power of time. [cue spooky music]

Temporarily. That is the word I was going for.
posted by quin at 4:45 PM on September 26, 2006 [1 favorite]

I had the same problem with a push-on cable connection at the wall. I replaced it with a screw-on connection and the problem disappeared.
posted by weapons-grade pandemonium at 5:09 PM on September 26, 2006

When I moved recently, I had the cable installation guy run a brand new wire directly from the pole to the cable modem, making no stops on the way. The previous owner had several splitters and amplifiers on the other cable lines in the house. This is usually fine for television usage, but cable modems don't operate like televisions, and splitting the line can weaken the signal enough to cause problems.

Have your cable company come out to fix the problem, and run a dedicated line to your modem.
posted by odinsdream at 6:03 PM on September 26, 2006

Thanks for the tips so far; keep 'em coming. I don't think the splitters are an issue as they are brand new and were installed by the cable guy tech when he came out -- they split the cable into one PVR and then to the modem, nothing else. There's no apparent filter on the line and it's currently a screw-in type.

Of note, I just had to reset the modem before this posting -- it died immediately after I turned off the TV. Coincidence or is it possible the TV (or PVR/digital cable box) is sending some sort of feedback into the splitter that's disrupting the signal?
posted by modernnomad at 6:13 PM on September 26, 2006

Of note, I just had to reset the modem before this posting -- it died immediately after I turned off the TV. Coincidence or is it possible the TV (or PVR/digital cable box) is sending some sort of feedback into the splitter that's disrupting the signal?

My gf had no end of troubles with her cable modem-based internet, similar to the troubles you're having (intermittent signal drop, necessary resets at random, etc.). The cable techs who came out finally determined (after four hours) that the problem was due to a neighbor's TV feeding back power into the cable line, which was causing enough signal distortion to knock her signal out for her internet, even though there was no noticeable difference in her television reception.

So yes, it's possible. I'll fifteenth the recommendation of having a tech come out and assess the problem. Generally speaking, the signal quality requirements for internet usage are higher than what's necessary for TV viewing. Signal degradation can come from a variety of technical and environmental sources, many of which you likely will not have the means to troubleshoot yourself. If/when they do come out, be sure to have them check the voltage on the line. Our techs didn't consider this until very late in the troubleshooting game.
posted by Brak at 6:35 PM on September 26, 2006

I used to have that same problem with my cable modem; the culprit was the strength of the signal which was too much for the modem to handle. The cable guy installed an extra splitter just to weaken the signal a little bit and it hasn’t gone dead on me for the past 6 months.
posted by LeavenOfMalice at 6:12 AM on September 27, 2006

It is a long shot, given crappy consumer networking gear, but can you access the cablemodem and look at a log page? It might tell you what's happening.

Another possiblilty -- overheating of the cablemodem, bad power supply putting out weak power, bad filter caps leaving AC noise ontop of the DC, which locks the processor.
posted by eriko at 6:47 AM on September 27, 2006

I had this issue, especially when I had running torrents. Eventually I returned the cable modem to my internet provider and had it replaced with a new model. I've had no trouble since.
posted by backwards guitar at 6:56 AM on September 27, 2006

Do you have a signal amplifier installed? If you do this could be the problem. The line used for the signal to your cable modem needs to enter modem before the amplifier.
posted by gogomickey at 11:42 AM on September 27, 2006 [1 favorite]

The cable company is sending someone out, though not till Oct 8 -- I'll post the results then. Thanks for the help thus far.
posted by modernnomad at 3:03 PM on September 27, 2006

Update. The cable tech determined that not enough signal was getting to the modem. He replaced the 4-way splitter that the original tech had installed with a 2-way to reduce interference, badmouthing the original tech as stupid and lazy. That seems to have cleared the problem up, though he added it was also possible that interference was being generated by older TVs somewhere else in the building, and that in combination with interference picked up by the extra plugs on the original splitter probably was the cause.
posted by modernnomad at 10:42 AM on October 9, 2006