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Poor SNR on downstream channel

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Poor SNR on downstream channel

About  2 weeks ago there was a bad storm roll through my area and a poll on our stream was knocked down and had to replace, it took out the internet for the entire day. (I live on a peninsula of a lake and it took out the whole area) They did not replace the lines, jsut the pole, infact some of the lines were hanging there for days tied to a street sign before they were put back up. Ever since then I have been getting terrible download speed usually in the 5mbps  area. I know my modem is no longer supported, I have a new one being delivered tomorrow, I currently have a SB6141 (I am replacing it with a netgear CM1000 32x8) I want to know will i still run in to these issues with the new modem? Ill post my stats below, note channel 3 SNR is low and has TONS of codes. I am guessing thats whats causing me to drop my speed.

 

Downstream Bonding Channel Value
Channel ID
Frequency 465000000 Hz  471000000 Hz  477000000 Hz  483000000 Hz  489000000 Hz  495000000 Hz  507000000 Hz  519000000 Hz 
Signal to Noise Ratio 37 dB  37 dB  30 dB  35 dB  38 dB  37 dB  37 dB  33 dB 
Downstream Modulation QAM256  QAM256  QAM256  QAM256  QAM256  QAM256  QAM256  QAM256 
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
-2 dBmV   -2 dBmV   -2 dBmV   -1 dBmV   -2 dBmV   -2 dBmV   -1 dBmV   -1 dBmV  

 

Upstream Bonding Channel Value
Channel ID 15  13  14 
Frequency 22800000 Hz  36400000 Hz  29600000 Hz 
Ranging Service ID 13059  13059  13059 
Symbol Rate 5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec 
Power Level 51 dBmV  51 dBmV  51 dBmV 
Upstream Modulation [2] QPSK
[1] 32QAM
[3] 64QAM
 
[2] QPSK
[1] 32QAM
[3] 64QAM
 
[2] QPSK
[1] 32QAM
[3] 64QAM
 
Ranging Status Success  Success  Success 

 

Signal Stats (Codewords) Bonding Channel Value
Channel ID
Total Unerrored Codewords 116206362  116189417  6282558  116193677  116170622  116171535  116171788  115254488 
Total Correctable Codewords 189  64  23361639  3200  65  66  50  901299 
Total Uncorrectable Codewords 597  568  13736857  1495  574  667  1404  18448 

 

 

Time Priority Code Message
Jun 30 2018 20:53:34 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:53:12 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:53:12 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:52:37 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:52:28 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:52:28 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:50:33 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:50:33 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:50:33 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:47:22 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:45:56 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:45:56 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:45:31 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:43:49 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:43:49 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:43:24 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:43:13 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:43:12 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:42:17 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Jun 30 2018 20:41:54 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b8:16:19:f9:1f:39;CMTS-MAC=00:01:5c:87:24:49;CM-QOS=1.1;CM-VER=3.0;
Contributor

Re: Poor SNR on downstream channel

Hi proxy , 

 

Your downstream look fine , if the db is too high you would starting getting noise , if you are concerned you could use a "Motorola Drop Amp" , although the are extremly hard to find , I do agree some look on the low side , like 3 & 9 .

What concerns me more is the QAM , I think on your newer modem you should see QAM256.

 

Right now all looks nominal even though 3 & 9 could be higher.

 

I have isses as well , not sure where you are from , I am from NH and receive my signal from the Londonderry sub-station , and it has a known history of mucking up.

 

Good luck , 

 

Gary

Expert

Re: Poor SNR on downstream channel

Hi @Jedi29

Your power levels are fine and your SB6141 is still a supported device. (see http://mydeviceinfo.xfinity.com)

Your error log and uncorrectables confirm your connection issues. Replacing the modem will probably not correct the issues. There is the possibility that the SB6141 is failing, but probably not. Most likely you'll want to look for wiring issues at your premise.

 

See the troubleshooting guide for more information. The issue may be outside of your control, so if you don't find any obvious issues, consider getting a tech out.


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Gold Problem Solver

Re: Poor SNR on downstream channel


@proxy42086 wrote: ...
Channel ID         15           13           14      ...
Power Level   51dBmV  51dBmV  51dBmV ...

51dBmV on the upstream is too high. These should be below 50.

Expert

Re: Poor SNR on downstream channel


@Jedi29 wrote:


What concerns me more is the QAM , I think on your newer modem you should see QAM256.


FWIW, that is on the downstream channels only. Comcast doesn't support QAM256 for the upstream.



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New Poster

Re: Poor SNR on downstream channel

Just an update heres a post of my new stats with new modem + router. Went from 8 channels to 30, internet hasnt dropped and speed has been 150+ still getting some errors on channels 12 and 3 their snr seems to be lower than all other channels

 

<tabindex=-1>Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 465000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enable BPI+
IP Provisioning Mode Honor MDD IPv6 only

<tabindex=-1>Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 1 465000000 Hz -2.9 dBmV 40.1 dB 1247081938 29 0
2 Locked QAM256 2 471000000 Hz -3.2 dBmV 40.0 dB 1247152861 29 1
3 Locked QAM256 3 477000000 Hz -2.6 dBmV 32.9 dB 1247105741 50483 4103
4 Locked QAM256 4 483000000 Hz -2.1 dBmV 38.0 dB 1247170503 568 382
5 Locked QAM256 5 489000000 Hz -2.5 dBmV 40.5 dB 1247180764 26 0
6 Locked QAM256 6 495000000 Hz -3.0 dBmV 39.9 dB 1247172568 28 0
7 Locked QAM256 7 507000000 Hz -2.3 dBmV 40.5 dB 1247198904 18 0
8 Locked QAM256 8 513000000 Hz -2.1 dBmV 34.1 dB 1247203939 3185 1246
9 Locked QAM256 9 519000000 Hz -2.5 dBmV 39.7 dB 1247219562 31 1
10 Locked QAM256 10 525000000 Hz -2.8 dBmV 35.7 dB 1247228352 186 118
11 Locked QAM256 11 531000000 Hz -2.7 dBmV 38.9 dB 1247237884 30 3
12 Locked QAM256 12 537000000 Hz -2.2 dBmV 30.9 dB 1246461399 415224 162583
13 Locked QAM256 13 543000000 Hz -2.3 dBmV 35.9 dB 1247256068 471 522
14 Locked QAM256 14 549000000 Hz -2.8 dBmV 32.0 dB 1247237875 13528 6952
15 Locked QAM256 15 555000000 Hz -3.0 dBmV 36.6 dB 1247274420 760 298
16 Locked QAM256 16 561000000 Hz -2.6 dBmV 40.1 dB 1247293488 24 0
17 Locked QAM256 17 567000000 Hz -2.6 dBmV 40.3 dB 1247302704 21 0
18 Locked QAM256 18 573000000 Hz -3.2 dBmV 39.9 dB 1247312039 18 0
19 Locked QAM256 19 579000000 Hz -3.5 dBmV 39.5 dB 1247321369 22 0
20 Locked QAM256 20 585000000 Hz -3.0 dBmV 36.1 dB 1247329547 576 600
21 Locked QAM256 21 591000000 Hz -2.5 dBmV 38.2 dB 1247339952 133 19
22 Locked QAM256 22 597000000 Hz -2.6 dBmV 39.8 dB 1247349429 28 0
23 Locked QAM256 23 603000000 Hz -3.1 dBmV 36.7 dB 1247358099 381 410
24 Locked QAM256 24 609000000 Hz -3.1 dBmV 35.5 dB 1247365477 820 1764
25 Locked QAM256 25 615000000 Hz -2.6 dBmV 34.8 dB 1247369983 2770 3233
26 Locked QAM256 26 621000000 Hz -1.7 dBmV 38.3 dB 1247386233 357 147
27 Locked QAM256 27 627000000 Hz -1.9 dBmV 39.5 dB 1247396253 16 0
28 Locked QAM256 28 633000000 Hz -2.3 dBmV 39.0 dB 1247403132 20 0
29 Locked QAM256 30 639000000 Hz -2.0 dBmV 38.9 dB 1247409457 18 0
30 Locked QAM256 31 645000000 Hz -1.0 dBmV 39.8 dB 1247417798 13 0
31 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0

<tabindex=-1>Upstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 13 36400000 Hz 51.0 dBmV
2 Locked ATDMA 14 29600000 Hz 51.0 dBmV
3 Locked ATDMA 15 22800000 Hz 51.0 dBmV
4 Not Locked Unknown 0 0 Hz 0.0 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV

<tabindex=-1>Downstream OFDM Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 1 29 720000000 Hz -0.7 dBmV 38.0 dB 1108 ~ 2987 58321536 8695028 2
2 Not Locked 0 0 0 Hz -1.6 dBmV 0.0 dB 0 ~ 4095 0 0 0

<tabindex=-1>Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked Unknown 0 0 Hz 0 dBmV
2 Not Locked Unknown 0 0 Hz 0 dBmV

Current System Time: Mon Jul 02 22:59:31 2018 
Expert

Re: Poor SNR on downstream channel

The upstream power is still too high. There is an impairment somewhere.



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