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Visitor
jschug
Posts: 2
Registered: ‎06-18-2013

intermittent loss of signal

I'm currently having an issue where my cable modem will lose signal and have to refresh its connection. This happens usually 2-3 times a day, sometimes more and sometimes less. It can be really annoying when it happens while I am trying to send an email or use Skype. I've had this problem in the past, and it was resolved when a tech came out and removed a splitter from the cable box that someone in my apartment complex had installed to steal cable television, so I'm kind of thinking that may be what is going on again. There is a single splitter on the cable after it enters my apartment, which was installed by Comcast to split the cable between my cable modem and HD receiver.

 

Modem signal stats:

 

Downstream SNR: 41.5 dB

Downstream power: 2.4 dBmV

Upstream power: 43.2 dBmV

 

I notice that the upstream power is really high, and I'm wondering if that could be caused by an extra splitter. I didn't check my signal stats the first time this happened, which was about 5-6 months ago so I have nothing to compare it to.

 

I've also tested my setup by taking the my splitter out of the equation by connecting the coaxial cable from the wall directly into the modem and I've also removed my router and connected the modem directly to my desktop PC, and the problem persists so I don't think it has anything to do with the equipment in my apartment.

Connection Expert
EG
Posts: 40,192
Registered: ‎12-24-2003

Re: intermittent loss of signal

Post split out in to its own thread / topic here on this board. Click on the above link to follow it.

Cable Expert
i-am-nerdburg
Posts: 10,043
Registered: ‎06-27-2009

Re: intermittent loss of signal

We need more information please:

- Post your upstream and downstream signal levels. Click the link or type: http://192.168.100.1 or http://10.0.0.1 into your browser. We are interested in your power levels (dBmV) and your Signal to Noise Ratio (SNR). You may also want to contact Comcast and ask for your upstream SNR (uSNR) and receive level.
- Post your modem’s error logs.
- Post the make and model of your modem.
- Post the make and model of your router if you have one.
- Let us know if you contacted Comcast or had a tech visit.
- Let us know what the lights on your modem are doing when you are having problems.
- If you have already posted some of this information, you don't need to post it again.

Visitor
jschug
Posts: 2
Registered: ‎06-18-2013

Re: intermittent loss of signal

Signal level information in previous post.

 

Make/model of cable modem: Motorolla Surfboard Model SB5101U

Make/model of router: Belkin N150 Model F9K1001v1

 

Modem log:

 

1970-01-01 00:00:24 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:14 3-Critical R002.0 No Ranging Response received - T3 time-out

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-19 18:55:43 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-19 18:55:43 3-Critical Ô7954.20 Resetting the cable modem due to docsDevResetNow

 

1970-01-01 00:00:22 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-19 18:47:20 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-19 18:47:20 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no

Unicast Maintenance o

 

2013-06-19 18:47:20 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire

QAM/QPSK symbol timing

 

1970-01-01 00:00:26 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-19 17:32:08 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-19 17:32:08 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-19 17:32:08 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:21 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-18 21:50:02 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-18 21:50:02 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-18 21:50:01 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:28 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-18 17:39:37 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-18 17:39:37 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-18 17:39:37 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:26 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-18 13:14:10 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-18 13:14:10 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-18 13:14:10 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

2013-06-18 04:30:07 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-18 04:30:05 6-Notice M571.0 Ethernet link down - not ready to pass packets

 

2013-06-18 04:30:01 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-18 04:29:59 6-Notice M571.0 Ethernet link down - not ready to pass packets

 

1970-01-01 00:00:20 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-17 09:51:10 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-17 09:51:10 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-17 09:51:10 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:25 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-16 07:23:39 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-16 07:23:39 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-16 07:23:39 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:26 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-15 21:47:32 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-15 21:47:32 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-15 21:47:32 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:27 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-14 21:29:58 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-14 21:29:58 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-14 21:29:58 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:22 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-13 00:40:34 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-13 00:40:34 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-13 00:40:34 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:27 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 21:50:17 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-12 21:50:17 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-12 21:50:17 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

2013-06-12 20:51:00 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 20:50:58 6-Notice M571.0 Ethernet link down - not ready to pass packets

 

2013-06-12 20:50:54 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 20:50:48 6-Notice M571.0 Ethernet link down - not ready to pass packets

 

1970-01-01 00:00:21 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 20:50:08 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-12 20:50:08 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-12 20:50:08 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

2013-06-12 19:10:41 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 19:10:39 6-Notice M571.0 Ethernet link down - not ready to pass packets

 

1970-01-01 00:00:21 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 19:09:55 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-12 19:09:55 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-12 19:09:55 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

2013-06-12 18:25:52 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 18:25:50 6-Notice M571.0 Ethernet link down - not ready to pass packets

 

1970-01-01 00:00:20 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:11 3-Critical R002.0 No Ranging Response received - T3 time-out

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 18:24:50 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-12 18:24:50 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-12 18:24:50 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:22 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:12 3-Critical R002.0 No Ranging Response received - T3 time-out

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

1970-01-01 00:00:22 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 16:54:41 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-12 16:54:41 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

2013-06-12 16:54:41 3-Critical T001.0 SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

 

1970-01-01 00:00:26 5-Warning D003.0 DHCP WARNING - Non-critical field invalid in response ;CM-MAC=00:25:f2:57:7e:ea;

 

1970-01-01 00:00:08 6-Notice M571.1 Ethernet link up - ready to pass packets

 

2013-06-12 16:34:39 6-Notice M573.0 Modem Is Shutting Down and Rebooting...

 

2013-06-12 16:34:39 3-Critical R004.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance o

 

 

As I said in the original post, I've had a tech come out for this problem previously and the issue ended up being someone had put an unauthorized splitter in the cable box which was degrading my signal. It was also causing picture and sound problems with my cable television as well.

 

When I lose signal (which seems to coincide with the critical time synchronization failures in the modem's log), I actually lose connection on my PC first, dropping Skype calls and interrupting anything that is currently loading, before the modem lights flash off and begin to re-establish a connection. Once the modem reconnects and the router refreshes its connection with the modem, my internet works fine until the issue happens again. However, it can take several minutes for the modem and router to recover from the interruption, and this issue can sometimes occur several times over the course of an hour. This is just really annoying.