U

Visitor

 • 

5 Messages

Sat, Jan 8, 2022 10:00 PM

residential cable modem and business cable modem both on same coax?

Hello,

I'd like to know if it's acceptable to have both cable modems connected to the same main coax cable?  Our internet went out today out of the blue, and I tracked it back to a bad cable splitter that the installer put in when they added my wifes business internet for her home office.  I was under the impression that this was an invalid setup, causes signal interference, and other issues, but I'm not a pro so didn't push back on it at the time.  We have been unsatisfied with our internet performance, when it works, it's good and very fast.  But it frequently has outages and disconnects for 10-15 seconds multiple times/day.  Even now after changing the spliter I still see warnings in the event log, and wondering if this is the cause or something else.

REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;


Cable Connection
Cancel Apply
Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency
 
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 531000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 21 531000000 Hz 7.6 dBmV 42.5 dB 0 0
2 Locked QAM256 13 477000000 Hz 6.7 dBmV 42.3 dB 0 0
3 Locked QAM256 14 483000000 Hz 6.7 dBmV 42.3 dB 0 0
4 Locked QAM256 15 489000000 Hz 6.8 dBmV 42.3 dB 1 0
5 Locked QAM256 16 495000000 Hz 6.7 dBmV 42.3 dB 0 0
6 Locked QAM256 17 507000000 Hz 6.9 dBmV 42.3 dB 0 0
7 Locked QAM256 18 513000000 Hz 7.0 dBmV 42.3 dB 0 0
8 Locked QAM256 19 519000000 Hz 7.1 dBmV 42.4 dB 0 0
9 Locked QAM256 20 525000000 Hz 7.4 dBmV 42.4 dB 0 0
10 Locked QAM256 22 537000000 Hz 7.8 dBmV 42.6 dB 1 0
11 Locked QAM256 23 543000000 Hz 7.9 dBmV 42.6 dB 0 0
12 Locked QAM256 24 549000000 Hz 7.8 dBmV 42.5 dB 0 0
13 Locked QAM256 25 555000000 Hz 7.6 dBmV 42.4 dB 0 0
14 Locked QAM256 26 561000000 Hz 7.7 dBmV 42.5 dB 0 0
15 Locked QAM256 27 567000000 Hz 7.7 dBmV 42.5 dB 0 0
16 Locked QAM256 28 573000000 Hz 7.7 dBmV 42.4 dB 2 0
17 Locked QAM256 29 579000000 Hz 7.8 dBmV 42.4 dB 0 0
18 Locked QAM256 30 585000000 Hz 8.0 dBmV 42.5 dB 0 0
19 Locked QAM256 31 591000000 Hz 8.2 dBmV 42.6 dB 0 0
20 Locked QAM256 32 597000000 Hz 8.4 dBmV 42.6 dB 0 0
21 Locked QAM256 33 603000000 Hz 8.4 dBmV 42.6 dB 2 0
22 Locked QAM256 34 609000000 Hz 8.5 dBmV 42.7 dB 1 0
23 Locked QAM256 35 615000000 Hz 8.5 dBmV 42.6 dB 0 0
24 Locked QAM256 36 621000000 Hz 8.2 dBmV 42.6 dB 1 0
25 Locked QAM256 37 627000000 Hz 8.0 dBmV 42.5 dB 1 0
26 Locked QAM256 38 633000000 Hz 7.8 dBmV 42.4 dB 0 0
27 Locked QAM256 39 639000000 Hz 7.4 dBmV 42.2 dB 0 0
28 Locked QAM256 40 645000000 Hz 7.0 dBmV 42.1 dB 0 0
29 Locked QAM256 41 651000000 Hz 6.7 dBmV 42.0 dB 1 0
30 Locked QAM256 42 657000000 Hz 6.6 dBmV 42.0 dB 0 0
31 Locked QAM256 43 663000000 Hz 6.5 dBmV 41.9 dB 0 0
32 Locked QAM256 44 669000000 Hz 6.7 dBmV 42.0 dB 2 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 2 5120 16400000 Hz 57.3 dBmV
2 Locked ATDMA 3 5120 22800000 Hz 57.8 dBmV
3 Locked ATDMA 4 5120 29200000 Hz 58.3 dBmV
4 Locked ATDMA 5 5120 35600000 Hz 58.8 dBmV
5 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
 
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 0 159 678000000 Hz 7.7 dBmV 41.9 dB 1126 ~ 2969 61210990 109683 0
2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV
 
Extended Upstream Transmit Power
 
Current System Time:Sat Jan 08 16:53:49 2022
System Up Time:00:27:05

Accepted Solution

EG

Expert

 • 

91.7K Messages

13 d ago

Specs look great now. The uncorrectables may be due to the linework that was done. You can reboot the modem to reset the error counter and start from scratch. Keep an eye on the amount of them, and whether they happen quickly or over a longer length of time. The bottom line is if the connection is now more stable. Good luck !

Visitor

 • 

5 Messages

@EG

thank you so much for all of your help.  you are right, after 1/2 hour, no uncorrectables.  I believe my issues are solved, only time will tell if the drops are done, but we can call this closed.   thanks again

EG

Expert

 • 

91.7K Messages

@user_f26f9d wrote;

@EG

thank you so much for all of your help.  you are right, after 1/2 hour, no uncorrectables.  I believe my issues are solved, only time will tell if the drops are done, but we can call this closed.   thanks again


You're welcome but I'd give it at least 24 to 48 hours and see. Hope things hold up for you ! 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.

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EG

Expert

 • 

91.7K Messages

18 d ago

The upstream power is WAY out of spec !!! That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an 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 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, 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, kinks, sharp bends, etc.

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 !

(edited)

Visitor

 • 

5 Messages

@EG  That's the only splitter in the whole house, one leg goes to our cable modem, the other goes to wife's employer's cable modem.  We only have internet so no other devices besides the 2 cable modems, and no other coax besides those 3 lines (counting the feed).  I had already checked the 3 connections for corrosion and tightness when I was troubleshooting before.  The splitter (Antronix CMC2002H-A 5-100Mhz 2 way) may be poor quality I don't really know, it's the only one I had on hand after finding the Extreme BDS108H the installer put in is no longer functioning about an hour ago.  I'm waiting for an Extreme BDS102H to show up in the mail, already ordered, when it arrives I'll swap it out and check again.  Can you tell me what the upstream power range should be?  I think it might be worthwhile to swap out the coax between the modem and the splitter also.  I don't see an RG value on it, it only says perfectflex series 6 18awg.

(edited)

EG

Expert

 • 

91.7K Messages

18 d ago

The Antronix is a very good quality splitter that Comcast uses widely, but it may be malfunctioning. Only a swap would rule that out.

That's RG6 which is the preferred cable. But it may not be *quad shield* which may be better depending on the length of the run. But it's also more difficult (stiffer) to work with.

40 to 50 dB is the preferred range with 45 being the *sweet spot*. 

So if there is nothing that you can do to improve the connection quality, then you should get a tech out to investigate / correct the problem as stated.

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.


Good luck !

EG

Expert

 • 

91.7K Messages

18 d ago

BTW, the signal stat ranges / values are in the pinned Troubleshooting Tips topic at the top of this board's page: https://forums.xfinity.com/conversations/your-home-network/internet-troubleshooting-tips/602dae4ac5375f08cde52ea0

 

Check your signal levels

To view your modem’s status page go to http://192.168.100.1 or http://10.0.0.1

 

Specification      Min             Max
Downstream Power Level    
Cable Modems -10dBmV +10dBmV
Gateways and EMTAs -7dBmV +7dBmV
Downstream Signal to Noise Ratio 35dB -
Upstream Power Level +35dBmV +50dBmV
Upstream Signal to Noise Ratio 31dB -
Upstream Receive Power -2dBmV +2dBmV

 

Note: Not all modems will allow you to view the status page and some will have different URLs to access this info. If you are unable to access your modem’s status page, you can contact Comcast Customer Support and ask the support representative for these values.

 

(edited)

Visitor

 • 

5 Messages

16 d ago

@EG I removed the splitter and connected the cable modem directly to the drop from the pole, and get even more errors in the log.  I don't want to waste your time, I'm escalating to Comcast, just wanted to get this additional info out there in case it changes your advice in any way

Mon Jan 10 14:40:37 2022 (Notice (6)) CM-STATUS message sent. Event Type Code: 24; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:40:30 2022 (Notice (6)) CM-STATUS message sent. Event Type Code: 22; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:40:10 2022 (Notice (6)) CM-STATUS message sent. Event Type Code: 23; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:40:06 2022 (Warning (5)) DBC-REQ Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:39:55 2022 (Critical (3)) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:39:35 2022 (Warning (5)) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:39:35 2022 (Critical (3)) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

Downstream power is now out of spec, too high.  Upstream power is lower, but still over 50

Cable Connection
Cancel Apply
Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency
 
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 531000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 21 531000000 Hz 10.8 dBmV 42.2 dB 6629 307
2 Locked QAM256 13 477000000 Hz 10.0 dBmV 42.0 dB 8 0
3 Locked QAM256 14 483000000 Hz 10.0 dBmV 42.0 dB 362 1167
4 Locked QAM256 15 489000000 Hz 10.1 dBmV 42.0 dB 360 1215
5 Locked QAM256 16 495000000 Hz 10.1 dBmV 42.0 dB 319 1204
6 Locked QAM256 17 507000000 Hz 10.2 dBmV 41.8 dB 388 1170
7 Locked QAM256 18 513000000 Hz 10.3 dBmV 42.0 dB 362 1175
8 Locked QAM256 19 519000000 Hz 10.4 dBmV 42.0 dB 350 1119
9 Locked QAM256 20 525000000 Hz 10.6 dBmV 42.2 dB 364 1101
10 Locked QAM256 22 537000000 Hz 11.0 dBmV 42.3 dB 315 1161
11 Locked QAM256 23 543000000 Hz 11.1 dBmV 42.3 dB 327 1124
12 Locked QAM256 24 549000000 Hz 11.1 dBmV 42.3 dB 353 1093
13 Locked QAM256 25 555000000 Hz 10.9 dBmV 42.1 dB 333 1192
14 Locked QAM256 26 561000000 Hz 11.1 dBmV 42.2 dB 325 1192
15 Locked QAM256 27 567000000 Hz 11.1 dBmV 42.2 dB 316 1221
16 Locked QAM256 28 573000000 Hz 11.0 dBmV 42.2 dB 326 1203
17 Locked QAM256 29 579000000 Hz 11.0 dBmV 42.2 dB 354 1191
18 Locked QAM256 30 585000000 Hz 11.1 dBmV 42.2 dB 357 1202
19 Locked QAM256 31 591000000 Hz 11.3 dBmV 42.2 dB 352 1217
20 Locked QAM256 32 597000000 Hz 11.6 dBmV 42.3 dB 300 1255
21 Locked QAM256 33 603000000 Hz 11.6 dBmV 42.3 dB 368 1246
22 Locked QAM256 34 609000000 Hz 11.8 dBmV 42.4 dB 332 1271
23 Locked QAM256 35 615000000 Hz 11.9 dBmV 42.4 dB 351 1246
24 Locked QAM256 36 621000000 Hz 11.8 dBmV 42.4 dB 343 1270
25 Locked QAM256 37 627000000 Hz 11.7 dBmV 42.3 dB 365 1261
26 Locked QAM256 38 633000000 Hz 11.4 dBmV 42.2 dB 330 1215
27 Locked QAM256 39 639000000 Hz 11.0 dBmV 42.0 dB 361 1295
28 Locked QAM256 40 645000000 Hz 10.6 dBmV 41.8 dB 391 1270
29 Locked QAM256 41 651000000 Hz 10.1 dBmV 41.7 dB 369 1270
30 Locked QAM256 42 657000000 Hz 10.0 dBmV 41.6 dB 347 1268
31 Locked QAM256 43 663000000 Hz 9.9 dBmV 41.6 dB 354 1235
32 Locked QAM256 44 669000000 Hz 10.0 dBmV 41.7 dB 375 1212
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 2 5120 16400000 Hz 54.3 dBmV
2 Locked ATDMA 3 5120 22800000 Hz 54.3 dBmV
3 Locked ATDMA 4 5120 29200000 Hz 54.8 dBmV
4 Locked ATDMA 5 5120 35600000 Hz 55.0 dBmV
5 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
 
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 0 159 678000000 Hz 11.3 dBmV 42.0 dB 1126 ~ 2969 6445485741 18903108 136
2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV
 
Extended Upstream Transmit Power
 
Current System Time:Mon Jan 10 14:44:28 2022
System Up Time:1 day 22:17:44

(edited)

EG

Expert

 • 

91.7K Messages

16 d ago

Yep. You need a tech out to properly balance the line. Good luck with it ! Please post back with how things turn out.

Visitor

 • 

5 Messages

@EG thanks for your help.
Tech came out today and guessed the symptoms before I even had a chance to explain.  He found and a filter, and removed it, but power was still out of spec.  He escalated to another team who showed up an hour or 2 later.  Power levels are in spec now based on the guideline you shared earlier.  I now have uncorrectables, but I'm guessing that doesn't mean much by itself if we don't have other issues going forward?

Cable Connection
Cancel Apply
Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency
 
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 651000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 41 651000000 Hz 5.0 dBmV 42.0 dB 220 780
2 Locked QAM256 13 477000000 Hz 4.5 dBmV 42.4 dB 321 1328
3 Locked QAM256 14 483000000 Hz 4.6 dBmV 42.4 dB 455 1587
4 Locked QAM256 15 489000000 Hz 4.6 dBmV 42.4 dB 373 1501
5 Locked QAM256 16 495000000 Hz 4.6 dBmV 42.4 dB 319 1391
6 Locked QAM256 17 507000000 Hz 4.8 dBmV 42.3 dB 281 1226
7 Locked QAM256 18 513000000 Hz 4.9 dBmV 42.4 dB 202 681
8 Locked QAM256 19 519000000 Hz 5.0 dBmV 42.5 dB 273 1127
9 Locked QAM256 20 525000000 Hz 5.3 dBmV 42.5 dB 238 1102
10 Locked QAM256 21 531000000 Hz 5.5 dBmV 42.6 dB 250 1082
11 Locked QAM256 22 537000000 Hz 5.7 dBmV 42.6 dB 242 1067
12 Locked QAM256 23 543000000 Hz 5.8 dBmV 42.6 dB 268 1051
13 Locked QAM256 24 549000000 Hz 5.8 dBmV 42.6 dB 257 1077
14 Locked QAM256 25 555000000 Hz 5.7 dBmV 42.5 dB 268 1092
15 Locked QAM256 26 561000000 Hz 5.8 dBmV 42.5 dB 239 1091
16 Locked QAM256 27 567000000 Hz 5.8 dBmV 42.5 dB 292 1060
17 Locked QAM256 28 573000000 Hz 5.7 dBmV 42.5 dB 242 1101
18 Locked QAM256 29 579000000 Hz 5.9 dBmV 42.5 dB 271 1078
19 Locked QAM256 30 585000000 Hz 6.0 dBmV 42.5 dB 286 1084
20 Locked QAM256 31 591000000 Hz 6.3 dBmV 42.6 dB 304 1062
21 Locked QAM256 32 597000000 Hz 6.5 dBmV 42.6 dB 276 1106
22 Locked QAM256 33 603000000 Hz 6.6 dBmV 42.6 dB 374 1632
23 Locked QAM256 34 609000000 Hz 6.6 dBmV 42.7 dB 422 1568
24 Locked QAM256 35 615000000 Hz 6.6 dBmV 42.7 dB 373 1643
25 Locked QAM256 36 621000000 Hz 6.4 dBmV 42.7 dB 408 1655
26 Locked QAM256 37 627000000 Hz 6.2 dBmV 42.5 dB 445 1631
27 Locked QAM256 38 633000000 Hz 5.9 dBmV 42.4 dB 441 1622
28 Locked QAM256 39 639000000 Hz 5.6 dBmV 42.3 dB 510 1592
29 Locked QAM256 40 645000000 Hz 5.3 dBmV 42.2 dB 459 1628
30 Locked QAM256 42 657000000 Hz 5.1 dBmV 42.1 dB 335 1275
31 Locked QAM256 43 663000000 Hz 5.2 dBmV 42.1 dB 348 1287
32 Locked QAM256 44 669000000 Hz 5.2 dBmV 42.2 dB 356 1161
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 2 5120 16400000 Hz 44.3 dBmV
2 Locked ATDMA 3 5120 22800000 Hz 44.3 dBmV
3 Locked ATDMA 4 5120 29200000 Hz 44.8 dBmV
4 Locked ATDMA 5 5120 35600000 Hz 45.3 dBmV
5 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 0 Hz 0.0 dBmV
 
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 0 159 678000000 Hz 6.1 dBmV 42.3 dB 1126 ~ 2969 725748932 686432 143681
2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV
 
Extended Upstream Transmit Power
 
Current System Time:Thu Jan 13 15:07:10 2022
System Up Time:05:13:31

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