Comcast XFINITY → [Connectivity] Intermittent connectivity - upload power @54 dBmV

Internet cuts out intermittently... seems to happen more so in the AM. I am a newby to cable modem issues... did a little googwork (synonym for google homework) before posting here. When internet was working, I logged into modem and it seems my upload power is dangling near the upper limit of acceptable range (reading of 54 dBmV). Download power and S/N were fine.

Modem: Motorola SB5101.
I do have a -3.5dBmV splitter to modem, other side to TVs, but this only affects the download power when removing and connecting directly to wall.

Question: am I dangling on edge of upload power because of modem (need a new one) or is this an issue with the outside connection? By the way, I keep a fan blowing on my modem. Thanks, John.

Unless it is unseasonably hot where you are a fan should not be needed, normal unimpeded convection is plenty.
I think the reason it doesn't change the upstream is that modem is screaming as loud as it can.
If it is pegged at the max it is likely a line/wiring problem.
So you should probably call for a tech visit. The tech can test the actual signal levels (modem is making a rough estimate, it's not a precision meter) check the modem and call for line maintenance if it's not an in house problem.

I would get a tech out 54 Dmv is high.

They can also check for other problems such as noise ingress etc.

54 upstream is the most modern modems can transmit at, and depending on what else is going on may or may not be an issue, the companies would like you to be at 51, this is an ideal value, not a must have or you are not working value. 51 means there is room for the plant to fluctuate and the CMTS will still hear you in its appropriate range of -1 to +1. If you start off at 54, and it gets hot you may end up with 54 transmit and -3 receive at the head end, this is not good.

Reasons your transmit would be that high vary from start to finish. A single loose fitting in the path, thermal regression, too many splitters in the home coax network, damage to home network cables, over padded/eq'd amps, bad passives, you installed a splitter wrong [yes there is an input and it must be the input] you ran it through a power strip on the coax [these generally do not provide return as they are intended for antenna use not cable], etc..

You can check your logs for 192.168.100.1 and note errors most noteable t3 for return issues, but in the end, I think you need a visit from a technician, before they arrive make sure all debis, trash, furniture, etc. is moved OUT of the way for cable outlets in the house, the utility access points outside [generally where the power meters is] and any splitters you may have in or around the house. If you hide or leave something clutters, they cannot get there to repair it, and they are NOT supposed to sit there while you clear it after they arrive, so get it ready or deal with multiple visits for the problem until you do.

love the explaination, but how would a bad cat5 cable cause upstream transmit issues on a docsis modem?

This is not necessarily so throughout CC's footprint. Individual plant specs / tap values vary in different areas.

w/ D3, it's fairly standard and close to that now.

My understanding is that 40 dB to 50 dB is now the preferred range for return with 45 dB being ideal and not 51 dB.

I've seen plenty of posts here and other places which show people already having connectivity issues at 51 dB.

Some modems are more or less tolerant than are others. We must also keep in mind that the accuracy of any given modem's measuring mechanism isn't an exact science.

If everything else about the connection is ok, 51 would still "work". There is no way 45 would be ideal. There are a lot of plant situation where the return is that or more from the tap.

I don't disagree with that depending on an individual's own unique environment / equipment / conditions, but it does not leave much wiggle room. I prefer not making "one size fits all" statements..

Definitely should have a tech come out. Mine was topping out at 51-54 every hour. Had a few techs come out and fixed the noise issue coming off the pole.

Also, the max upstream also depends on the QAM level. The higher QAM level, the lower the max upstream. 54dB may barely work for 64QAM, but not affect 16QAM much.

51 i wouldnt bat an eye at....

We all know how *subjective* interpreting signal stats can be.

And I already know this stuff Andy, thanks.

Peace out.

I was told by the last tech that came out to my house that at a 54dBm upstream that the modem would loose connection. He was right too, because every time our modem reach that signal we would have to power cycle the modem. Also like to mention he replaced the cable from the tap to the house and had to replace the modem.

I never said cat5 anywhere.... I assume my scattered thoughts saying home network cable is where you are assuming cat5, but it could be power cables with a converter pair to be honest and I think you know I meant "home coax network cables"... >

EG - Sigh I will correct the text to be more specific for you....

Docsis STANDARD max transmit levels
qpsk = 58
16 qam = 55
32 qam I forget and cannot find it but I bet its 55.
D2 64 qam = 54
D3 64 qam = 57 but back to 54 when bonding so no one bothers using 57 since bonding is the ultimate goal

»www.cable360.net/cablefa ··· 829.html
and
»www.cable360.net/ct/depl ··· 887.html

Hopefully this is more clear for you.

These have nothing to do with the taps on your network, this is the DOCSIS actual specifications. These specifications did force higher value taps out of coax networks in the past, but that's history.

As to comcast install specs there is only ONE printed spec available to all comcast employees at the global teamcomcast web site, and it says 54 at the outlet. Not 51, but 54.

Local FFO's may impose different values as a TARGET but not a REQUIREMENT. But that's all they are. 51 makes sense, as networks fluctuate and change you may need 3db of play However, 10 db of play on low frequencies is ludicrous. What are you changing the return pad from 7 to a 17 to fix noise outages or something? Someone considering that should probably consider a rebuild instead. While I have seen old systems where the amps and taps looked like what you buy in radio shack, if that's what you are running off of, the 45 won't really help you anyway.

There is no open to interpretation, the docsis standard says exactly what it says, and there is no reading +54 and seeing +45 unless you're dyslexic.

youre quote i was questioning is: "damage to home network cables".

that to me sounds like patch cables.....

I will comment only on this;

People are human so I assert that no matter what the specs are, people will still make it subjective and have their own individual opinions and beliefs. This always was and always will be and we all know what *opinions* are like..

I run a constant 54-55 and don't experience issues (and haven't for the last couple of years when I first got the service). No doubt it's just on the edge, but it's been stable.

Anyone know how to get to the logs on a Cisco DPC3000?

FWIW, when I had that modem two years ago I was able to access the error log entries when I first got it. After about two weeks they pushed a firmware update to it which disabled that feature however I still could access the signal status page.

I thought I remembered that as well. But I hadn't looked in a while. That stinks.