Arris S33 low power on upstream channels

Hello,

I have gigabit service from Comcast.. My internet is NOT dropping out entirely but the speeds are wildly erratic. Several devices buffering for long periods before and during videos. I noticed my upstream channels are all hovering around 28 and 29dbmv. I've looked at other similar issues on the forum and I believe they should be above 35dbmv.

I did have an earlier issue of line noise but I've worked on that and the modem is only showing uncorrectables on QSFDM now. Speeds are between 8 and 200 to an iPhone connected to the wifi (not perfect but it shows the speed roller coaster).

Lastly, is the number of upstream channels correct? Thanks in advance!

Responses

XfinityThomasA

Official Employee

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2K Messages

1 year ago

Greetings, @Crowdog72! Thank you for your detailed post, and for visiting the Xfinity Forums for help with the signal levels on your Arris S33 cable modem. It's important to us that you have a great connection and we will get to the bottom of this! You'll want to double-check with the owner's manual for the specifications. I've located the Arris S33 cable signal levels article so we can double-check together. Is it one, two, three, or more channels? It says in the article the Downstream Bonded Channels section, the Power levels of - 15 dBmV to + 15 dBmV are within the acceptable range for each downstream channel. Is this issue isolated to your iPhone, and have you tried troubleshooting your Xfinity internet using the Xfinity App?

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C

Crowdog72

11 Messages

I noticed the 45 as well but up until now I was getting at least 34 on those channels. Thomas, I believe I have found the culprit. The error only occur when my recently installed LED lights are on. I've peeked up into the ceiling and my cables are indeed passing within two feet of the light. They are throwing off major interference. Pulling the cables was too difficult so I am going to run a line from the box into the room just on the other side of the wall. I've tested the modem previously at the box and everything was perfect there. It should eliminate the issues. Comcast may have reduced my power to limit line noise??? Hopefully I can report back on it after the weekend!

1 year ago

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XfinityKrista

Official Employee

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1.5K Messages

We would love to hear back from you. Please feel free to reach out whenever you'd like.

One of the things I love most about this platform is that we are able to help customers at their convenience and can pick up right where you left off.

We know you have choices, and we thank you for choosing Xfinity. I hope you have a great day.

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1 year ago

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C

Crowdog72

11 Messages

Update: Still getting uncorrectables but sporadically. It's not steady but it is definitely severely reduced. It might be as simple as a bad coax connector (I had to me a length of quad shield rg6 myself).

I noticed that when connected to the Comcast grounded coupler in the box that my downstream dBmv are about +3db than when not (-5 when not or -8 when on grou ded coupler). My noise levels are a little high maybe. I am currently connected to the grou ded coupler btw. See current snapshot below.

1 year ago

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C

Crowdog72

11 Messages

Occasionally get a buffer during streaming video and multiple ping tests show a slowdown every two minutes or so. I am not sure if that means anything or not AND I am not sure why that is. I am using an app I cannot take snapshots of...unfortunately. I may be over analyzing everything.

1 year ago

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XfinityVianney

Official Employee

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1.9K Messages

I'll be glad to review this further on our end. I ask that you reach out privately, so we can cover the details of your account. You can start by clicking the chat icon located in the top right corner of your forums page when signed in. Once there, you can direct your messages to "Xfinity Support." Please add your full name and service address to help us locate your account. Let me know if you have any questions @Crowdog72

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1 year ago

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BruceW

Gold Problem Solver

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26.2K Messages

1 year ago

@XfinityThomasA wrote: "... I've located the Arris S33 cable signal levels article ...

Note that the document you linked calls for the modem to transmit an upstream power level of AT LEAST 45 dBmV, which is absurd.

The important number is not the modem's transmit power, it's the signal level received at the CMTS (ideally 0 dBmV).

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

(edited)

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BruceW

Gold Problem Solver

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26.2K Messages

1 year ago

"... Comcast may have reduced my power to limit line noise??? ..."

Probably not. The modem upstream power levels are controlled automatically and continuously by Comcast's equipment to maintain the signal received by them at zero plus or minus 2 dBmV. As long as modem upstream power is not maxed out, what's important is not the level at the modem, it's the level (and quality) of the modem's signal as received at Comcast.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

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EG

Expert

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108.1K Messages

1 year ago

@Crowdog72 wrote;

Comcast may have reduced my power to limit line noise???

FWIW. Just to add here. It actually would be the opposite of that theoretically. The power would need to be increased to overcome the effects of a high noise floor level so that the modem would be heard more clearly by the CMTS / system.

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Crowdog72

Arris S33 low power on upstream channels

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Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

BruceW

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

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