Observer

Disconnect Cable to Normalize Signal Levels?

I have a strange issue, and I am hoping I can get some input. The modem will always keep a connection for several days (I have the SB6183) but then the signal will slowly degrade and accumulate a large amount of uncorrectables. Also, the power levels on the downstream channels goes down by several dBmV (from 2 or 3 down to 0) and the upstream will go up by several dBmV (from 44 or 45 to 47 or 48). I have some screenshots but I don't know how to post them.

The only thing that seems to resolve the issue is to remove the coaxial cable from the back of the modem for several seconds and plug it back in. After that the signal levels are normal and I have no issues for several days, until I have to repeat the procedure.

I live in an apartment building. I've had technicians come out here but no one seems to know what the issue is, and usually when they come out, they disconnect and reconnect something, and natually that resolves the issue while they are here until it crops up again later after they've left.

12 REPLIES
Helper

Re: Disconnect Cable to Normalize Signal Levels?

Something is causing the signal to degrade, maybe some electrical noise, when you disconnect the modem it resets the connection to the server and power levels will adjust for conditions, modem tells server...not good enough, not good enough increase upstream power(when things are bad, and gives up) Maybe someone else can help on how to post screenshots
Expert

Re: Disconnect Cable to Normalize Signal Levels?

Have they put new connectors on everything?

Is there a splitter or connector behind the wall plate?

If not, there's a splice somewhere in the building that's bad.

Good luck getting it fixed

 

Observer

Re: Disconnect Cable to Normalize Signal Levels?

I don't know a lot about the connections in the building, but from the line that comes into the apartment there is one splitter (-3.5, -3.5), and the cable modem runs off a direct line from there. It's not a very long run and the cable is relatively new, the connectors seems to be ok, and all the connections are tight. There are no unterminated connectors, no amplifiers or other devices on the line, and I cleaned the copper at every point with rubbing alcohol and let them dry, but it doesn't seem to resolve anything. I still have the same issues.

Highlighted
Contributor

Re: Disconnect Cable to Normalize Signal Levels?

Check the system grounding.  Be sure the ground is continuous from the entrance to the modem - no connector shells broken loose from the sheilds.  It's possible to get a static voltage build up on the cable and that affects the modem. 

Expert

Re: Disconnect Cable to Normalize Signal Levels?

What does the other port of the splitter feed?

Alcohol won't fix a bad connection. Is the center wire shiny copper or dull or corroded?

 

Observer

Re: Disconnect Cable to Normalize Signal Levels?

The other end of the splitter goes to another splitter, and from there to two cable boxes. All the connectors look shiny, so I don't think that's the issue. I was thinking it could be noise ingress or static, but I have no tools to check or verify either one, and about grounding I am not sure what to look for. The cable comes into the apartment, to the splitter and from there to the modem in one single cable run. All the connectors are intact (no breaks or cracks). Is there anything I can do on my own or am I only limited to having a tech come out and tell me that everything is working fine?

Expert

Re: Disconnect Cable to Normalize Signal Levels?

anything wrong/ intermittent with the cable tv?

what modem errors show up while it's working?

 

Observer

Re: Disconnect Cable to Normalize Signal Levels?

I'm sorry. I've been a little busy and I didn't have a lot of time to reply.

 

The cable TV is working fine. I never see any issues or dropouts in the service. This is a list of items in the log that I can see since the last time I rebooted it (I removed some of the MAC details):

 

Mon Mar 16 09:54:21 2015Notice (6)DHCP Renew - lease parameters Time Protocol Servers modified;
Mon Mar 16 09:54:21 2015Error (4)DHCP RENEW WARNING - Field invalid in response v4 option;
Sun Mar 15 14:14:54 2015Critical (3)Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Thu Mar 12 21:54:18 2015Notice (6)DHCP Renew - lease parameters Time Protocol Servers modified;
Thu Mar 12 21:54:18 2015Error (4)DHCP RENEW WARNING - Field invalid in response v4 option;
Wed Mar 11 21:03:16 2015Critical (3)Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Tue Mar 10 18:16:54 2015Notice (6)TLV-11 - unrecognized OID;
Tue Mar 10 18:16:54 2015Error (4)Missing BP Configuration Setting TLV Type: 17.9;
Tue Mar 10 18:16:54 2015Error (4)Missing BP Configuration Setting TLV Type: 17.8;

 

The modem hasn't rebooted yet, but I see the signal degrading again:

 

Downstream Bonded Channels
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectedUncorrectables
1LockedQAM25616369000000 Hz0.8 dBmV40.4 dB26538
2LockedQAM2562285000000 Hz1.0 dBmV40.3 dB45381
3LockedQAM2563291000000 Hz1.0 dBmV40.3 dB39883
4LockedQAM2564297000000 Hz1.0 dBmV40.5 dB31690
5LockedQAM2565303000000 Hz1.0 dBmV40.5 dB33746
6LockedQAM2566309000000 Hz0.7 dBmV40.3 dB36784
7LockedQAM2567315000000 Hz0.8 dBmV40.4 dB33069
8LockedQAM2568321000000 Hz0.7 dBmV40.3 dB35839
9LockedQAM2569327000000 Hz0.9 dBmV40.4 dB33569
10LockedQAM25610333000000 Hz0.9 dBmV40.5 dB31047
11LockedQAM25611339000000 Hz0.6 dBmV40.2 dB31256
12LockedQAM25612345000000 Hz0.9 dBmV40.3 dB31654
13LockedQAM25613351000000 Hz1.1 dBmV40.5 dB276121
14LockedQAM25614357000000 Hz0.9 dBmV40.4 dB28345
15LockedQAM25615363000000 Hz0.7 dBmV40.3 dB27443
16LockedQAM2561279000000 Hz1.4 dBmV40.6 dB39399

 

 
Upstream Bonded Channels
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA42560 Ksym/sec37000000 Hz48.0 dBmV
2LockedATDMA25120 Ksym/sec24200000 Hz46.5 dBmV
3LockedATDMA35120 Ksym/sec30600000 Hz47.0 dBmV
4LockedTDMA12560 Ksym/sec19400000 Hz46.5 dBmV
Helper

Re: Disconnect Cable to Normalize Signal Levels?

  • DS signals look good considering modem has been up 5+ days.
  • US power at 48 is something to watch. it is out of spec if it goes over 51.
  • what data prompted your comment on signal degradation?
redrock in Austin, Tx