Observer

Fluctuating RX Issue

Hi,

 

From time to time I take a look at my modem's RF parameters, and I've noticed my Downstream tends to go in and out of spec. Last week, my RX was a consistent -8 dbmv, and when I checked today things looked a little different. I don't have record of how things looked last week, but this is what I saw when my modem finally connected after a four hour outage:

 

Downstream

 DCIDFreqPowerSNRModulationOctetsCorrectedsUncorrectables
Downstream 120579.00 MHz-11.10 dBmV36.61 dB256QAM1231680158704
Downstream 29513.00 MHz-8.00 dBmV36.39 dB256QAM920724600
Downstream 310519.00 MHz-8.10 dBmV36.61 dB256QAM898488800
Downstream 411525.00 MHz-8.80 dBmV36.61 dB256QAM869453200
Downstream 512531.00 MHz-8.40 dBmV38.98 dB256QAM856643600
Downstream 614543.00 MHz-9.40 dBmV38.61 dB256QAM893073800
Downstream 715549.00 MHz-9.10 dBmV38.61 dB256QAM930026900
Downstream 816555.00 MHz-9.80 dBmV38.61 dB256QAM880800500
Downstream 917561.00 MHz-10.10 dBmV37.64 dB256QAM930978200
Downstream 1018567.00 MHz-10.30 dBmV37.64 dB256QAM903726200
Downstream 1119573.00 MHz-10.90 dBmV36.61 dB256QAM933054170
Downstream 126495.00 MHz-7.50 dBmV38.98 dB256QAM9253149150
Downstream 1321585.00 MHz-12.00 dBmV31.34 dB256QAM93712937920
Downstream 1422591.00 MHz-12.20 dBmV33.06 dB256QAM859635930
Downstream 1523597.00 MHz-11.60 dBmV35.97 dB256QAM9436930260
Downstream 1624603.00 MHz-10.60 dBmV35.78 dB256QAM888707300

 

Upstream

 UCIDFreqPowerChannel TypeSymbol RateModulation
Upstream 1436.90 MHz48.00 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 2119.00 MHz48.00 dBmVDOCSIS1.x (TDMA)2560 kSym/s16QAM
Upstream 3330.40 MHz48.00 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 4223.90 MHz48.00 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM

 

Event Log

Date TimeEvent IDEvent LevelDescription
8/20/2017 16:43840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:44840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:46840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:46840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:47840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:47840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:48840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:48840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:48840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:49840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:50840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:51840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:57840005003SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:57840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:57840005003SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:57840202005Lost MDD Timeout;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 16:58820004003Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 20:18840007005RCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 20:18850102005TCS Partial Service;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;
8/20/2017 20:19840005003SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=78:71:9c:95:27:22;CMTS-MAC=00:17:10:86:57:1f;CM-QOS=1.1;CM-VER=3.0;

 

My understanding of RX and TX levels is very basic. I know RX ideally shouldn't go above 8 dbmv, or below -8 dbmv, and I know TX should never go above what my modem shows above, but there's so much I don't know about this, so if you guys have time I'd be grateful if hit me with a bit of your knowledge in this thread.

 

So here are my questions:

1. What are the most common reasons RX and TX behave this way?

2. Which lines in this event log would give insight as to what's wrong?

3. Do the numbers in the frequency column hold any significance? Are my frequencies common? What's too high, or too low?

 

Thanks in advance.

 
4 REPLIES 4
Expert

Re: Fluctuating RX Issue

Read the latest solved thread...

the usual... too many splitters, incorrectly installed splitters, open splitter ports, water damaged rodent chewed outside lines etc.

 Your modem is not on the first 2 way splitter or no splitter for a start.

I can tell by the US and DS levels.

Looks like rg59 or water in outside line due to the excessive rolloff as freq's increase.

 It appears to have damaged line somewhere and open/ shorted lines on one or more splitter ports.... It also looks like broadcast tv ingress on the 2 low s/n channels due to open ports, loose corroded connectors, etc....

 

 

Expert

Re: Fluctuating RX Issue

This is a Physical issue between the modem and the outside pole and can't be fixed over the phone by whatever phony excuse they claim to send the modem, lol....

This needs a tech out if You can't clean up the mess, lol.

 

Observer

Re: Fluctuating RX Issue

Thank you for replying!

When you mentioned I wasn't on the first splitter or no splitter, I got really curious as to what the US/DS told you that helps draw that conclusion.

Also, I checked outside and we've got a low hanging wire that goes into a box the cable guy was messing with when he installed us, so the likelihood of you being right is high. If it turns out you're 100%, I need you to take me on as padawan.

Expert

Re: Fluctuating RX Issue

levels should have been measured by the installer and corrected then rather than a repeat service call.

Sounds like they reused an old line from a previous cable installer rather than running a new line.  If you only have a modem and a cable box, those 2 devices must be on a single 2 way splitter. DS Levels should be at a -4 dBmv minimum a 4 way would push them down to -8 dBmv

 they get an F for the job....need to come out and fix it.