US Cable Support > Comcast HSI > [Signals] Signal check

[Signals] Signal check

That downstream SNR looks low

Your Upstream power is rather low.

I think your within the spec tho.

reply to kerfuffle
These levels are fine. 35dB SNR is totally fine. Not sure what the last guy was eluding to. If you think you are having problems due to level inconsistency you should check the signal page while you're having the problem. Otherwise you'll want to examine the modem log file and decode the log entries. Have you checked to see that all the fittings you can touch in your install are tight?

An upstream transmit of 35 is not low - don't know who's been telling you guys that. 30 is low, 25 is REALLY low but 35 is just fine.

Fairly low compared to other user's signals around here. Not saying it's anything to be concerned about unless he's having problems with his connection.

reply to TechnoScott

Yes, in fact the maximum transmit requirements drop for D3 bonded when they bond over 3 channels.

reply to nysports4evr
And he is having issues.

35 dB SNR on the downstream is within spec but I would prefer to have it higher.

The DOCSIS 3 spec only requires 30db SNR on the downstream for signals between -6 and +15. 35db should be fine.

reply to kerfuffle
Although it appears "ok", with a downstream of -3ndBmv, I would have expected a higher upstream value...at least in the 40s, no? Seems to me a little unbalanced.

I notice that this is either not a Docsis 3.0 modem (only one downstream channel showing) or not yet a D3 area?

If you are in a Docsis 3.0 area, I would definitely recommend a D3 modem, as you should get more consistent performance due to channel bonding.
--
Deeds, not words

I was originally using a Motorola SB5100, which was subsequently swapped out to a SB5120 by the line tech that was dispatched. He ran some readings on my line, and he confirmed exactly what you said about the upstream value being out of wack. The signal from the pole was borderline, but it was no where near as bad as the reading from the modem. He assured me that he will escalate the issue to the guys with the "bucket trucks" to take a look into it at the headend/cmts.

I did not receive an update or confirmation from them whether or not that had actually taken place. However, I did notice the signals change slightly from what it was when the issue(s) started. So I assume work was done at the headend.

Initial readings
Downstream Value
Frequency 693000000 Hz Locked
Signal to Noise Ratio 37 dB
Power Level -9 dBmV
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

Upstream Value
Channel ID 3
Frequency 30100000 Hz Ranged
Power Level 37 dBmV

=====

Current readings after multiple tech rolls
Downstream Value
Frequency 693000000 Hz
Signal to Noise Ratio 35 dB
QAM QAM256
Network Access Control Object ON
Power Level -3 dBmV
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
Upstream Value
Channel ID 1
Frequency 30100000 Hz
Ranging Service ID 649
Symbol Rate 5.120 Msym/s
Power Level 35 dBmV

I am from Massachusetts, which as far as I know we are DOCSIS 3.0 ready.

Since the modem is pre-used, I am open to the idea of purchasing a new DOCSIS 3.0 compliant modem.

reply to TechnoScott

The upstream power level does seem to fluctuate a few dBs throughout the course of the day. Latest reading:

Downstream Value
Frequency 705000000 Hz
Signal to Noise Ratio 36 dB
QAM QAM256
Network Access Control Object ON
Power Level -4 dBmV
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
Upstream Value
Channel ID 1
Frequency 30100000 Hz
Ranging Service ID 649
Symbol Rate 5.120 Msym/s
Power Level 33 dBmV

The signal fluctuation coincided with these log entries which refer to channel changes. Is this a sign of ongoing issues?

2012-06-22 16:56:43 7-Information Channel Change Complete - Enabling Bridge
2012-06-22 16:56:43 7-Information C203.0 DCC arrive new
2012-06-22 16:56:38 7-Information Starting Ranging On Channel 1
2012-06-22 16:56:38 7-Information Dynamic Channel Change of Downstream Requested - Disabling Bridge
2012-06-22 16:56:38 7-Information Dynamic Channel Change of Downstream Requested - Setting tuner to 705.0MHz
2012-06-22 16:56:38 7-Information C202.0 DCC depart old
2012-06-22 14:16:39 7-Information Channel Change Complete - Enabling Bridge
2012-06-22 14:16:39 7-Information C203.0 DCC arrive new
2012-06-22 14:16:34 7-Information Starting Ranging On Channel 1
2012-06-22 14:16:34 7-Information Dynamic Channel Change of Downstream Requested - Disabling Bridge
2012-06-22 14:16:34 7-Information Dynamic Channel Change of Downstream Requested - Setting tuner to 711.0MHz
2012-06-22 14:16:34 7-Information C202.0 DCC depart old
2012-06-20 07:46:57 7-Information SNMP: Working in SNMP V1/2c Only NmAccess mode
2012-06-20 07:46:55 7-Information INITIALIZATION COMPLETE - MODEM IS OPERATIONAL
2012-06-20 07:46:55 7-Information B401.0 Authorized
2012-06-20 07:46:55 7-Information SEC: Co-Signer CVC from configuration file was verified
2012-06-20 07:46:54 7-Information REGISTRATION COMPLETE - Waiting for Operational status
2012-06-20 07:46:54 7-Information REG: Capability type isn't supported by CMTS
2012-06-20 07:46:54 7-Information Registration file - downloaded
2012-06-20 07:46:52 7-Information Trying to download Configuration file ...

reply to EG
Because some systems are lazy and think padding return amplifiers will get them better carrier to noise figures because the modems are transmitting higher?

My logs are capturing a lot of entries pertaining to dynamic downstream changes. Is this normal behavior? I don't recall the frequency changing as often as it is right now, or at all.

2012-06-24 14:39:48 7-Information Channel Change Complete - Enabling Bridge
2012-06-24 14:39:48 7-Information C203.0 DCC arrive new
2012-06-24 14:39:43 7-Information Starting Ranging On Channel 1
2012-06-24 14:39:43 7-Information Dynamic Channel Change of Downstream Requested - Disabling Bridge
2012-06-24 14:39:43 7-Information Dynamic Channel Change of Downstream Requested - Setting tuner to 705.0MHz
2012-06-24 14:39:43 7-Information C202.0 DCC depart old
2012-06-23 17:38:25 7-Information Channel Change Complete - Enabling Bridge
2012-06-23 17:38:25 7-Information C203.0 DCC arrive new
2012-06-23 17:38:20 7-Information Starting Ranging On Channel 1
2012-06-23 17:38:20 7-Information Dynamic Channel Change of Downstream Requested - Disabling Bridge
2012-06-23 17:38:20 7-Information Dynamic Channel Change of Downstream Requested - Setting tuner to 711.0MHz
2012-06-23 17:38:20 7-Information C202.0 DCC depart old
2012-06-23 15:30:38 7-Information SNMP: Working in SNMP V1/2c Only NmAccess mode
2012-06-23 15:30:36 7-Information INITIALIZATION COMPLETE - MODEM IS OPERATIONAL
2012-06-23 15:30:36 7-Information B401.0 Authorized
2012-06-23 15:30:36 7-Information SEC: Co-Signer CVC from configuration file was verified
2012-06-23 15:30:35 7-Information REGISTRATION COMPLETE - Waiting for Operational status
2012-06-23 15:30:35 7-Information REG: Capability type isn't supported by CMTS
2012-06-23 15:30:35 7-Information Registration file - downloaded
2012-06-23 15:30:33 7-Information Trying to download Configuration file ...
Event Log has reached maximum size. Older log entries are lost.

That small sampling of log entries shows only one or two of these events per day. By no means is that a lot. Intermittent / occasional noise on the lines can cause these.