dlai817's profile

New Poster

 • 

3 Messages

Sat, Jan 23, 2021 11:00 AM

Internet Speed Always changing

Hi, I'm in an attached townhome on a plan for up to 200 Mbps. The speed is always changing and inconsistent. When I check the modem which is an SB 6183, there are 4 channels with millions of Uncorrectables, and one of them has a constantly changing SNR that ranges from 0~28 dB, while the others are more or less over 30:

 

ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectedUncorrectables
1LockedQAM25617579000000 Hz-4.4 dBmV38.9 dB10
2LockedQAM25618585000000 Hz-4.1 dBmV38.9 dB30
3LockedQAM25619591000000 Hz-3.8 dBmV38.7 dB40
4LockedQAM25620597000000 Hz-4.1 dBmV38.2 dB20
5LockedQAM25621603000000 Hz-4.7 dBmV38.8 dB20
6LockedQAM25622609000000 Hz-5.5 dBmV38.5 dB50
7LockedQAM25623615000000 Hz-5.2 dBmV38.5 dB110
8LockedQAM25624621000000 Hz-5.3 dBmV37.9 dB39053111
9LockedQAM25625627000000 Hz-4.8 dBmV35.8 dB7969152143525
10LockedQAM25626633000000 Hz-4.3 dBmV37.7 dB14462172332452
11LockedQAM25627639000000 Hz-4.9 dBmV37.2 dB7182792704669
12LockedQAM25628645000000 Hz-4.9 dBmV0.0 dB8581361681920
13LockedQAM25629651000000 Hz-5.3 dBmV38.3 dB50
14LockedQAM25630657000000 Hz-5.2 dBmV38.3 dB30
15LockedQAM25631663000000 Hz-4.9 dBmV38.3 dB70
16LockedQAM25637669000000 Hz-4.8 dBmV38.3 dB70

 

 

Checking my event log, there are a couple of critical errors which include (I removed MAC address for privacy reasons):

 

Time Not EstablishedCritical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
Time Not EstablishedCritical (3)No Ranging Response received - T3 time-out
Sat Jan 23 12:54:48 2021Critical (3)Resetting the cable modem due to docsDevResetNow
Time Not EstablishedCritical (3)No Ranging Response received - T3 time-out
Time Not EstablishedNotice (6)Honoring MDD; IP provisioning mode = IPv6
Sat Jan 23 13:33:58 2021Warning (5)MDD message timeout
Sat Jan 23 13:34:12 2021Critical (3)Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sat Jan 23 13:47:36 2021Warning (5)MDD message timeout

 

Could somebody explain what I need to do? It's a brand new modem and I did all the normal troubleshooting including checking all connections for tightness.

Responses

Accepted Solution

EG

Expert

 • 

86.2K Messages

3 m ago

The upstream power is high and it may be intermittently fluctuating even higher to out of spec levels. The downstream power is on the low /weak side as well. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

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.

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!tick
EG

Expert

 • 

86.2K Messages

3 m ago

please also post the upstream channel stats.

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!tick

New Poster

 • 

3 Messages

3 m ago

Upstream Bonded Channels

ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA35120 Ksym/sec22800000 Hz49.3 dBmV
2LockedATDMA15120 Ksym/sec35600000 Hz49.8 dBmV
3LockedATDMA25120 Ksym/sec29200000 Hz49.8 dBmV
4LockedATDMA45120 Ksym/sec16400000 Hz49.5 dBmV

New Poster

 • 

3 Messages

3 m ago

So after chatting with an xfinity rep, we replaced the ethernet cable connecting the modem and router, and turns out that was causing the problem!

EG

Expert

 • 

86.2K Messages

3 m ago

O/k but the signal stats / connection quality problem should be addressed nevertheless as it is a problem just waiting to happen... Good luck !

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!tick

New to the Community?

Start Here