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sjbianco87's avatar
sjbianco87
New Contributor
5 years ago

Need help with modem throwing error Dynamic Range window violation. Believe error to be causing modem to reboot numerous times throughout the day. What does it mean and how do i get it resolved?

Modem will periodically reboot several times per day for what i believe to be the Dynamic Range window violation error. Could this be to high SNR? SNR ranges from 39.8-41.8. Any assistance is appreciated.

7 Replies

  • Dave9's avatar
    Dave9
    Contributor III

    Dynamic Range Window is a concept related to upstream power on bonded channels, so it can't be directly related to your downstream SNR. In general there could never be such a thing as having too high of an SNR.

    A Dynamic Range Window Violation occurs when the CMTS asks the modem to set an upstream power level on one channel that is significantly different from the other channels. For example, if one of the channels is at 38 dBmV and then the CMTS asks for another channel to be set to 51 dBmV, that would create a violation because all channel powers need to be within a 12 dBmV range.

    I haven't been able to find the exact details, but I think this often happens in response to a very brief spike of noise on the line, since I've never seen the high power level stay in effect long enough to see it in the status page.

    The DRW violations on their own probably aren't causing the modem to reboot since they are event level 5 (warning), but when I was having that problem I did get brief upstream issues at the same time as the DRW violation in the log. Look for items in the event log that are event level 3 or lower such as T4 timeouts. Those are more likely to cause the reboots, and of course it's not the T4 itself causing the reboot. It's a problem on the line which causes a T4, and then the T4 triggers a reboot to try to clear the problem.

    • sjbianco87's avatar
      sjbianco87
      New Contributor

      the screen grab of the log i took last night shows both a T4 and a T3 timeout. Is this something that will require a technician to fix?

      • Dave9's avatar
        Dave9
        Contributor III

        It depends on what's wrong. Post the signals and the logs here. Not as a screen grab but as a copy/paste.

    • Dave9's avatar
      Dave9
      Contributor III

      Signals look pretty good, so it might be an intermittent problem. Check your interior coax connections and replace the interior coax with RG6 or better if it's old or if it's ever been kinked. Make sure connections are tight. A slightly loose connection lets in a lot of noise.

      Cox often likes to say it must be a bad modem and you need to replace the modem, but I don't agree with that. Modems do go bad but not nearly as often as Cox likes to think. If you replace the coax and tighten all connections and the problem continues, you will probably need a service call.

      • sjbianco87's avatar
        sjbianco87
        New Contributor

        they tried telling me yesterday that it must be my modem. I replaced it about 2 weeks ago thinking it was the problem. I'm thinking my old one wasn't bad and i replaced it for no reason. Is there a way to tell if the current coax is rgb6 just by looking at it? I know ethernet usually stamps the what type it is on the outer coating, i don't work with coax much. Thanks for the help.