New Poster
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3 Messages
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:
| Channel | Lock Status | Modulation | Channel ID | Frequency | Power | SNR | Corrected | Uncorrectables |
| 1 | Locked | QAM256 | 17 | 579000000 Hz | -4.4 dBmV | 38.9 dB | 1 | 0 |
| 2 | Locked | QAM256 | 18 | 585000000 Hz | -4.1 dBmV | 38.9 dB | 3 | 0 |
| 3 | Locked | QAM256 | 19 | 591000000 Hz | -3.8 dBmV | 38.7 dB | 4 | 0 |
| 4 | Locked | QAM256 | 20 | 597000000 Hz | -4.1 dBmV | 38.2 dB | 2 | 0 |
| 5 | Locked | QAM256 | 21 | 603000000 Hz | -4.7 dBmV | 38.8 dB | 2 | 0 |
| 6 | Locked | QAM256 | 22 | 609000000 Hz | -5.5 dBmV | 38.5 dB | 5 | 0 |
| 7 | Locked | QAM256 | 23 | 615000000 Hz | -5.2 dBmV | 38.5 dB | 11 | 0 |
| 8 | Locked | QAM256 | 24 | 621000000 Hz | -5.3 dBmV | 37.9 dB | 39053 | 111 |
| 9 | Locked | QAM256 | 25 | 627000000 Hz | -4.8 dBmV | 35.8 dB | 796915 | 2143525 |
| 10 | Locked | QAM256 | 26 | 633000000 Hz | -4.3 dBmV | 37.7 dB | 1446217 | 2332452 |
| 11 | Locked | QAM256 | 27 | 639000000 Hz | -4.9 dBmV | 37.2 dB | 718279 | 2704669 |
| 12 | Locked | QAM256 | 28 | 645000000 Hz | -4.9 dBmV | 0.0 dB | 858136 | 1681920 |
| 13 | Locked | QAM256 | 29 | 651000000 Hz | -5.3 dBmV | 38.3 dB | 5 | 0 |
| 14 | Locked | QAM256 | 30 | 657000000 Hz | -5.2 dBmV | 38.3 dB | 3 | 0 |
| 15 | Locked | QAM256 | 31 | 663000000 Hz | -4.9 dBmV | 38.3 dB | 7 | 0 |
| 16 | Locked | QAM256 | 37 | 669000000 Hz | -4.8 dBmV | 38.3 dB | 7 | 0 |
Checking my event log, there are a couple of critical errors which include (I removed MAC address for privacy reasons):
| Time Not Established | Critical (3) | SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; |
| Time Not Established | Critical (3) | No Ranging Response received - T3 time-out |
| Sat Jan 23 12:54:48 2021 | Critical (3) | Resetting the cable modem due to docsDevResetNow |
| Time Not Established | Critical (3) | No Ranging Response received - T3 time-out |
| Time Not Established | Notice (6) | Honoring MDD; IP provisioning mode = IPv6 |
| Sat Jan 23 13:33:58 2021 | Warning (5) | MDD message timeout |
| Sat Jan 23 13:34:12 2021 | Critical (3) | Started Unicast Maintenance Ranging - No Response received - T3 time-out; |
| Sat Jan 23 13:47:36 2021 | Warning (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.
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Accepted Solution
EG
Expert
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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.
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EG
Expert
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86.2K Messages
3 m ago
please also post the upstream channel stats.
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dlai817
New Poster
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3 Messages
3 m ago
Upstream Bonded Channels
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dlai817
New Poster
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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!
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EG
Expert
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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 !
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