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6 Messages
downstream OFDM SNR????
I just connected a new netgear CM1000V2 because my old zoom modem had to be rebooted about once a day to to lock-up (would lose connection completely). Netgear seems to have solved the loss of connectivity. I pay for 300mbps plan and comcast speed test shows my downstream is 200mbps +/-. House desktops and TVs all hardwired with home run connections to aggregating PCs<->Gig-E switch <-> router<->cblmodem. After a lot of reading-up on modem signal levels, I am questioning my downstream OFDM SNR - its 30-31 db. All other downstream channels are 35-39 SNR. Power levels look good (downstream running 0-4dbmv). Uncorrectables are very small.
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kvjkhjkhdfghjdf
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6 Messages
5 years ago
Well, tried comcast phone support with no result other than hearing the script, so did more debugging by reading lots of posts for CM1000 users seeing what their levels were before/after issues, developed a list of things to check, etc.
Rehung 70' coax run in basement to move 12"+ away from AC power lines, removed 'Y' splitter that splits TV/Modem to boost signal a bit and turned off all options on linksys router to strip/simplify everything. Performace went from 200mbps to 385mbps which is a little higher than advertised plan speed. Success.
Case closed for now. Thanks to all who helped and answered PMs regarding their case as it helped me move forward with debugging.
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kvjkhjkhdfghjdf
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6 Messages
5 years ago
Tried to insert image of modem status page with channels/levels etc, no go. So, below is a text paste.... See RED line near bottom.
Also, I tried plugging coax enetering home straight to modem to bypass splitter that splits TV/internet and there was no improvement to SNR or download speed.
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kvjkhjkhdfghjdf
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6 Messages
5 years ago
Do we have a list of those known modems?? Based on prior posts on this forum, seems other CM1000 modems report in the correct range. See prior post https://forums.xfinity.com/t5/Your-Home-Network/Connectivity-Issues-with-Netgear-CM1000/m-p/3333159 where they show 39db on the OFDM channel. I think I'm running low at 30db??
Also, in my event log, I only get nags about OFDM. Not sure what they tell us if anything:
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EG
Expert
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110.1K Messages
5 years ago
It is a known issue that some makes and models of modem's measuring mechanisms do not read the power level and the SNR of the OFDM channel accurately.
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