Internet Connection Keeps Dropping Out

[naiku]

Over the past few weeks my internet connection keeps dropping out, sometimes it requires me unplugging the modem and plugging it in again, other times it just comes back on its own. My ISP is Comcast, and the modem is a DPC2100R2.

If I look at the stats of the modem when the connection to the internet is lost they show as:

Receive Power Level
-15 to 12 dBmV (this fluctuates)

Signal to Noise Ratio
25.3 dB

Transmit Power Level
55.2 dBmV

Cable Modem Status
Not Sychronized

I watched it for a couple minutes, and the receive power was fluctuating, but the SnR and transmit power stayed fairly static.

Any idea's what to do? My wireless network (using DD-WRT over 2 routers) works fine through out all of this. So I am fairly certain it's either a modem or ISP issue. Any suggestions on what to try to figure out the problem and get it fixed?

[Egilbe]

Over the past few weeks my internet connection keeps dropping out, sometimes it requires me unplugging the modem and plugging it in again, other times it just comes back on its own. My ISP is Comcast, and the modem is a DPC2100R2.

If I look at the stats of the modem when the connection to the internet is lost they show as:

Receive Power Level
-15 to 12 dBmV (this fluctuates)

Signal to Noise Ratio
25.3 dB

Transmit Power Level
55.2 dBmV

Cable Modem Status
Not Sychronized

I watched it for a couple minutes, and the receive power was fluctuating, but the SnR and transmit power stayed fairly static.

Any idea's what to do? My wireless network (using DD-WRT over 2 routers) works fine through out all of this. So I am fairly certain it's either a modem or ISP issue. Any suggestions on what to try to figure out the problem and get it fixed?

Call Comcast and have them fix it. If it's your modem, replace it. If it's comcast's, have them replace it.

[jokenokid]

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[PhReE]

Receive Power Level
-15 to 12 dBmV (this fluctuates)

This is rather low. You should be between +10 to -10. How many splitters do you have? Can you put the cable modem on a drop with less splits?

Signal to Noise Ratio
25.3 dB

This is also wayy to low. It will probably improve if you can fix the above problem, but it may also be an indication of a lot of noise. You should be seeing 35-40dB here.

Transmit Power Level
55.2 dBmV

This is rather high, you should be seeing ~48dBmV MAX here. The higher this number, the 'louder' the cable modem is talking in attempt to reach the head end. Also probably due to too many splitters.


See if you can plug the cable modem into a direct drop with no splits and see if the numbers improve.

[Loke]

PhReE's advice is good, but I've worked for a few different providers and different cable modems and CMTS sometimes have different tolerances. You also may be seeing a snapshot without enough speed in updating to see fast fluctuations. Sometimes a tech can pull some of that from the head end or CMTS with better accuracy but the best is by a tech with a good line tester. You mentioned the numbers you posted are when you lose connection. I would compare to when it is working well. Are they any better? Its a good idea for everyone to occasionally document their signals so they have a baseline for when it has a problem.

Splitters are the #1 cause for cable modem signal issues. If I recall, each standard one-into-two splitter affects the signal by 3db. Each one adds up, so try to run your modem off a direct line. Also, they work a bit like light bulbs, deciding to reap havoc one day without notice. For this reason, never build a splitter in the walls and try to avoid splitting in the attic and then topping off your insulation with a few more R factors.