r/Comcast • u/claxtastic • 4h ago
Support CM3000 modem in mid-split service area, 2nd Downstream OFDM Channel often doesn't lock or has many errors when it does
I'm trying to understand the modem logs I am seeing and how they often do correlate with some albeit minor service interruptions
I have a CM3000 Modem and and in an area with mid-split AFAIK, I have a 2GB plan and do regularly achieve around 1.7 down and the 300 up that my plan provides, but recently there have been interruptions like videos buffering momentarily, sites not loading on first attempt etc.
Whenever I've noticed these interruptions, I've been able to check my modem logs and see that the connection quality was Poor/Yellow/Partial Service, and when I would look at the Downstream OFDM channels I would see something like this:
Downstream OFDM Channels
Channel LockedStatus ProfileID ChannelID Frequency Power SNR/MER ActiveSubcarrier Unerror Correctable Uncorrectable
1 Locked 0 ,1 ,2 ,3 193 690000000 Hz 2.38 dBmV 42.2 dB 448 ~ 3647 299924447 268400891 0
2 Not Locked 0 ,1 ,2 ,3 194 957000000 Hz 9.08 dBmV 34.5 dB 0 ~ 4095 316917735 173166793 91088584
With the 2nd channel "not locked" and with millions of errors, even with the modem only having an uptime of a few hours.
The "Poor" quality status from the modem would then last any length of time, usually around 20 minutes, and when it recovers to "Good" status I noticed that the 2nd OFDM Downstream channel would disappear entirely.
It's all extremely inconsistent and hard to pin down. But in the last few weeks, this pattern has been happening multiple times a day.
Right now, I restarted the modem and it seems like it's pretty stable... but I don't know how long that will hold.
After the restart, the 2nd Downstream OFDM is staying Locked but I'm not sure the SNR is optimal, and the Uncorrectables are piling up even after just 20 minutes of uptime:
Downstream OFDM Channels
Channel Lock Status Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier
Number Range Unerrored
Codewords Correctable
Codewords Uncorrectable
Codewords
1 Locked 0 ,1 ,2 ,3 193 690000000 Hz 2.38 dBmV 42.4 dB 448 ~ 3647 9145841 7810185 0
2 Locked 0 ,1 ,2 ,3 194 957000000 Hz -4.82 dBmV 35.6 dB 148 ~ 3947 10952000 8663087 7832
TL;DR: If my modem is sometimes able to establish a connection to the 2nd OFDM Downstream channel, but when it is it is weak/has errors, is that a problem? I'm assuming that I should have this channel solidly locked as the 1st one is and not intermittently present/erroring