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Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing Error

Regular Visitor

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing Error

I'm getting this same error from a Motorola MB8600 that I installed back in October.  Prior to that, I'd been using a unit rented from Comcast that *never* had any trouble for years. 

 

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Accepted Solutions
Expert

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing Error

The stats as read at the modem level at that moment in time were o/k but there are three additional signal stats that can case that error which can't be read by the modem. They can only be read from their end by them polling the CMTS (Cable Modem Termination System) at the local headend facility.

They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

You can call in and ask what these figures are. The Upstream Receive Power Level should fall within the range of -2dB to +2dB with 0dB being in the middle and perfect.

The Upstream SNR should be least 31dB, and the higher it is the better.

The ICFR should be no higher than 2 dB.

You could have an intermittent noise ingress issue in only the upstream channel(s) / return path only somewhere.

They will be able to see whether or not everything is in the green zone and also see a history plot for the modem.



All Replies
Expert

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing Error

The stats as read at the modem level at that moment in time were o/k but there are three additional signal stats that can case that error which can't be read by the modem. They can only be read from their end by them polling the CMTS (Cable Modem Termination System) at the local headend facility.

They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

You can call in and ask what these figures are. The Upstream Receive Power Level should fall within the range of -2dB to +2dB with 0dB being in the middle and perfect.

The Upstream SNR should be least 31dB, and the higher it is the better.

The ICFR should be no higher than 2 dB.

You could have an intermittent noise ingress issue in only the upstream channel(s) / return path only somewhere.

They will be able to see whether or not everything is in the green zone and also see a history plot for the modem.


Regular Visitor

Re: SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing Error

Tried chatting with Comcast support and they don't seem to be able to give me these values.  Will call when I get a chance.  Too loud for a call here now.