Weak DOCSIS 3.1 OFDM downstream channel

Other errors seen in the logs:

TLV-11 - unrecognized OID

Config File Rejected due to Invalid or Unexpected TLV 11

RNG-RSP CCAP Commanded Power in Excess of 6 dB

No Ranging Response received - T3 time-out

Hey there, @brownrice2025, thanks for reaching out through Xfinity Forums regarding your signal issues. I know how important it is to have a solid connection, as I work from home and rely on my connection too. You have reached the right place to troubleshoot. I would like to take a look at your signals on our end. 

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@brownrice2025 

What do the bonded QAM downstream channel power values look like ?

FWIW, we've seen this here before, where Comcast places an OFDM channel too high in the frequency range near the end of the plant's bandwidth capability. Many of their plants and equipment only extend to 1000 MHz operation. At 957 MHz, it may be too close to the roll-off point of the plant's bandwidth / spectrum capability, hence the weak power and SNR level.

This may need to be escalated to their engineering department for correction. 

Here is what ChatGPT says about my latest numbers.

5. Key Takeaways

1. Power is slightly low across many channels. Ideally, Comcast should aim for closer to -5 to 0 dBmV.

2. SNR is mostly fine, but the high-frequency channels and OFDM channel are borderline.

3. Uncorrectable errors are high on several channels. This is a sign of line issues, splitters, or noise interference.

4. Overall, your modem is connected and operational, but these stats indicate signal issues that could cause intermittent slowdowns or occasional drops, especially on DOCSIS 3.1 OFDM channels.

Yeah, so in addition to my last post about the OFDM channel, everything is either out of spec or close to it. Here are some things that you can try;

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/reconfigured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also, check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, or animal chews.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Good luck with it !