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user_4c21d8

31 Messages

Monday, September 11th, 2023 7:14 PM

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Issues with Arris SB8300 Modem

Anyone have issues or tips with this modem? A family member has this for when I visit, and in the last few months it's been cutting out, sometimes multiple times a day. Based on an old forum post, I tried adding a splitter; usually that hekps for a few days, but then it goes back to cutting out, remove the splitter, works for a week, cycle ad nauseum. Unfortunately the modem is out warrenty.

Question

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Updated 

2 years ago

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XfinityDilary

Official Employee

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2.2K Messages

2 years ago

Hello, @user_4c21d8. Thanks for posting on our community forums. I'm sorry to hear about the random disconnections. Have you tried manually rebooting the modem or through our Xfinity App too? How are you connecting to it Wi-Fi or Ethernet?  

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user_4c21d8

31 Messages

Yes I do that, sometimes by unplugging, other times through the modem's web portal. It's always a temporary help - on really bad days it only lasts for a few minutes before cutting out. Really bad days seem to come about every week or two (before I got the splitter it was more like every day or two).

This modem is also a wifi router, and that's how it's being used here. It has a coaxial cable plugged in that goes right to the wall (at least, before I inserted the splitter in between)

(edited)

2 years ago

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XfinityDilary

Official Employee

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2.2K Messages

Thanks for sharing, @user_4c21d8. When you experience the disconnection, is the modem rebooting completely? Or is it just the Wi-Fi signal that's lost? Have you checked to see if you experience the same disconnection while hardwired (ethernet) to the modem? 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

2 years ago

0

user_4c21d8

31 Messages

Most of the time it's not the wifi. I haven't tried plugging into ethernet, but I determined that because I can still connect to the modem's web portal even as the internet is cut out. That being said, on really really bad days sometimes the web portal is somewhat unstable, and I wonder about that. But even on those days, I can still run a test from the portal and it shows it can't reach the outside. Plus, restarting just the wifi mobile never helps.

2 years ago

0

XfinityDilary

Official Employee

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2.2K Messages

What do you mean by the web portal, @user_4c21d8? Are you referring to the modem admin page? Also, @EG shared some websites we can use to test the modem signal. Thanks for your help @EG. Have you had a chance to try those? 

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

2 years ago

user_4c21d8

31 Messages

Yes, I mean the modem admin page (basically what @EG shared, though it's set to a different IP address here).

2 years ago

0

EG

Expert

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110.3K Messages

2 years ago

What do the modem's signal stats look like ? Try getting them here; http://192.168.100.1 or here http://10.0.0.1 

Please copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.


What is the exact make and model number of the modem / gateway device ?

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user_4c21d8

31 Messages

It's an Arris SBG8300

This is what it shows about 5 minutes after coming back, with the splitter attached.

Downstream QAM

Index Frequency (Hz) Power Level (dBmV) SNR (dB) Modulation Lock Status
17 525000000 -0.500000 40.946209 QAM256 Locked
14 507000000 -0.700001 40.366287 QAM256 Locked
15 513000000 -0.599998 40.366287 QAM256 Locked
16 519000000 -0.599998 40.946209 QAM256 Locked
18 531000000 -0.299999 40.946209 QAM256 Locked
19 537000000 -0.500000 40.946209 QAM256 Locked
20 543000000 -0.200001 40.946209 QAM256 Locked
21 549000000 -0.099998 40.946209 QAM256 Locked
22 555000000 -0.200001 40.366287 QAM256 Locked
23 561000000 0.099998 40.946209 QAM256 Locked
  • <<
  • <
  • 1
  • 2
  • 3
  • 4
  • >
  • >>

Downstream OFDM

Index FFT Type Channel Width (dB) # of Active Subcarriers First Active Subcarrier (MHz) Last Active Subcarrier (MHz) Avg RxMER Pilot (dB) Avg RxMER PLC (dB) Avg RxMER Data (dB) Power Level (dBmV) Modulation Lock Status
29 4K 96 1880 691 784 50 44 44 0.6 QAM4096 Locked

Upstream QAM

Index Frequency (Hz) Power Level (dBmV) Channel Type Symbol Rate (KSym/sec) Modulation Lock Status
17 16300000 43.520599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE
20 35600000 44.270599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE
19 29200000 44.520599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE
18 22800000 43.770599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE

Upstream OFDMA

Index First Active Subcarrier (MHz) Last Active Subcarrier (MHz) Symbol Rate (KSym/sec) Power Level (dBmV) Lock Status Modulation

There is no data to display.



Before I put the splitter, these numbers looked very different. I don't have a screenshot saved unfortunately, but basically the downstream power levels were all above 0 while the upstream power levels were around 42. With the splitter I see the latter usually being 45-52, but it fluctuates greatly.

Edit: In the last 3 minutes the upstream numbers went back to 45-46, while downstream is -0.9 to -1.5.

(edited)

2 years ago

0

user_4c21d8

31 Messages

@EG​ During times it cuts out (like this very moment; posting from my phone now), those tables basically become almost empty - there's one row in downstream reporting 0.2 dBmV upstream reporting 43.5 dBm. I copied the text, so I'll paste it here whenever the internet comes back.

Edit: It came back on its own just now. Sometimes that happens. Here's the sample I took while it was out:

Downstream QAM
Index  Frequency (Hz)  Power Level (dBmV)  SNR (dB)  Modulation  Lock Status
17 525000000 0.200001 40.946209 QAM256 Locked
Downstream OFDM
Index  FFT Type  Channel Width (dB)  # of Active Subcarriers  First Active Subcarrier (MHz)  Last Active Subcarrier (MHz)  Avg RxMER Pilot (dB)  Avg RxMER PLC (dB)  Avg RxMER Data (dB)  Power Level (dBmV)  Modulation  Lock Status
There is no data to display.
Upstream QAM
Index  Frequency (Hz)  Power Level (dBmV)  Channel Type  Symbol Rate (KSym/sec)  Modulation  Lock Status
17 16300000 43.520599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE

(edited)

2 years ago

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user_4c21d8

31 Messages

I removed the splitter and it looks more like this now:

Downstream QAM

Index Frequency (Hz) Power Level (dBmV) SNR (dB) Modulation Lock Status
17 525000000 2.900002 40.946209 QAM256 Locked
1 417000000 2.400002 40.946209 QAM256 Locked
2 423000000 2.799999 40.366287 QAM256 Locked
3 429000000 2.799999 40.946209 QAM256 Locked
4 435000000 2.799999 40.366287 QAM256 Locked
5 441000000 3.200001 40.946209 QAM256 Locked
6 447000000 2.799999 40.946209 QAM256 Locked
7 453000000 3.299999 40.946209 QAM256 Locked
8 459000000 2.900002 40.946209 QAM256 Locked
9 465000000 3.000000 40.946209 QAM256 Locked
  • <<
  • <
  • 1
  • 2
  • 3
  • 4
  • >
  • >>

Downstream OFDM

Index FFT Type Channel Width (dB) # of Active Subcarriers First Active Subcarrier (MHz) Last Active Subcarrier (MHz) Avg RxMER Pilot (dB) Avg RxMER PLC (dB) Avg RxMER Data (dB) Power Level (dBmV) Modulation Lock Status
29 4K 96 1880 691 784 51 45 45 5.0 QAM4096 Locked

Upstream QAM

Index Frequency (Hz) Power Level (dBmV) Channel Type Symbol Rate (KSym/sec) Modulation Lock Status
17 16300000 43.520599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE
20 35600000 41.270599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE
19 29200000 44.770599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE
18 22800000 44.020599 US_TYPE_STDMA 5120 KSym/sec 64QAM ACTIVE


Things are still quite unstable, unfortunately.

2 years ago

0

EG

Expert

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110.3K Messages

2 years ago

Leave the splitter out. It's hurting more than helping. Obviously, something intermittent is going on with the line(s) somewhere. I'm going to post some standard things that you can try that may or may not apply;

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

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 check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.


Good luck with it !

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