Basic Internet Connectivity And Modem Help

[emblue]

Over the past week or so I've been having problems with my modem shutting down/rebooting -- sometimes it gets a signal after that, other times it doesn't. On repeat calls to Comcast tech support, I've mostly been told that I have low signal strength (sometimes they say there are all red lights, other times they say there are green and yellow).

My current modem signal info:

Downstream Frequency: 669000000 Hz

Downstream Signal to Noise Ratio: 36.7 dB

Downstream Power Level: -5.6 dBmV

Upstream Frequency: 29400000 Hz

Upstream Power: 54.0 dBmV

• The Downstream Power Level has been in the same range, but the Upstream Power Level has been fluctuating pretty dramatically -- Comcast told me it was at -0.9 the other day, and over the course of a phone call today it went from 28.53 to 0.5. Do those numbers indicate anything helpful for troubleshooting this?

• When I check the Modem logs, for the problem times, over and over I see "Received Response to Broadcast Maintenance Request, But no Unicast Maintenance" and then "Modem Is Shutting Down and Rebooting..." -- sometimes I see "DHCP WARNING - Non-critical field invalid in response." (and once "No Ranging Response received - T3 time-out (US 10)") -- does that indicate anything helpful for troubleshooting this?
  
  
• When I ping comcast.net, it times out and all 4 packets are lost.
  
  
• When I tracert comcast.net, it times out starting at about hop 7 (and stays timed out from there).

I'm going to try a different modem and also see if all cables are tightly connected/if any long cables or splitters can be eliminated in the mix, but I'm trying to figure out if that's even the issue at this point.

They tell me it'll be at the tech's discretion when the tech comes out as to whether they'll charge me for the visit or not -- I'd like to resolve it without having to pay $30-40 for the visit.

Thanks for any direction/insight!

[EG]

Looks like you have an excessive attenuation issue. Are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured ?

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 putting them back together again, then perhaps it's best to book a tech visit to investigate and correct.

[emblue]

Thanks for the response EG. Just removed one splitter/length of coax, and the numbers modified as follows:

Downstream Signal to Noise Ratio: was 36.7 dB, now 36.1 to 37.3 on repeat checking

Downstream Power Level: was -5.6 dBmV, now 3.0 to 3.1 dBmV on repeat checking

Upstream Power: was 54.0 dBmV, now 48.4dBmV on repeat checking

That enough to make a difference, or is the problem still there?

(Otherwise, I'm in a condo and not familiar enough with where the lines come from/go to, so don't know that I can configure it as you described. I'll do what I can to eliminate splits I don't need, and I'll refresh all the connections as you suggest and see where I am from there.)

[emblue]

Still fluctuating a bit more on recheck -- 

Downstream Signal to Noise Ratio about the same.

Downstream Power Level about the same, but going a bit higher than earlier -- 3.2 to 3.5 dBmV

Upstream Power about the same, but up a bit, too -- around 50.2 dBmV

[emblue]

Swapped a splitter, removed a few more cables between the modem and the primary splitter, and got it to:

Downstream Frequency: 675000000 Hz

Downstream Signal to Noise Ratio: 36.7 dB

Downstream Power Level: 0.0 to 0.4 dBmV

Upstream Frequency: 36200000 Hz

Upstream Power: 54.0 dBmV

From the original:

Downstream Frequency: 669000000 Hz

Downstream Signal to Noise Ratio: 36.7 dB

Downstream Power Level: -5.6 dBmV

Upstream Frequency: 29400000 Hz

Upstream Power: 54.0 dBmV

So what does that say? My problem, or something Comcast still needs to address?

Can I improve upon it any further? 

[EG]

Seems you gave yourself a little wiggle room at first but something is still intermittent in the lines / plant / infrastructure. This may need to be referred  / escalated to the maintenance dept. techs by a premise facing tech if they can't find / fix it. It may be somewhere in the neighborhood lines.

[emblue]

Thanks again for the response.

If I'm reading your response correctly (that there's still an issue), it sounds like I need to just take a chance on possibly paying the $40 service call fee (which I'm told is "at the technician's discretion"?) and see what they can do.

(It hasn't had the issue since I made the modifications -- router's not plugged in at the moment, so we'll see how things go later on....)

[EG]

They would only charge you if they find that the problem lies with the hardware that you own. There should be no charge if they find that the problem is with the property that Comcast owns.

[emblue]

Right -- I don't think it's my modem, but they said it could be something in the wiring/lines -- so if it's a bad splitter (or just the fact that there's a splitter) or an issue with a coax cable in the house, that's considered my  property/responsibility, not theirs, right?