NHMagicRyan's profile

6 Messages

Wednesday, September 20th, 2023 2:13 AM

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SB8200 drops DOCSIS3.1 off and on throughout the day

Upgraded to 900down/25up plan, needed to update to a DOCSIS 3.1 compatible modem.  I upgraded to the SB8200 a few months ago.  Everything was going great.  Awesome speeds; my router's daily speed test was averaging 800-900.  Then about a month ago Xfinity was making "upgrades in our network, in our neighborhood" and over the course of a week we had several outages.  Since then I have noticed my SB8200 loosing it's 3.1 connection off and on throughout the day.  When ever it does I go though about an hour of horrible speeds and dropped packets.  Eventually it stabilizes but my speeds will drop down to 400-600 down.

Now one of two things happen overnight:  it automatically reconnects to 3.1 or I wake up to download speeds less than a meg and uploads up to 25, so I'll reboot the modem and it typically connects first try to 3.1 or it wavers and connects later in the day.  I have removed the only splitter I had.  I am now connected directly to the line straight off the pole.  I have moved the Modem to my office where I can watch it (the SB8200 has an easy to note blue light for when DOCSIS 3.1 is engaged).   I have also done a factory reset of the modem.  Now reviewing the forums I think I am now getting enough power to my connection and that is throwing off my modem.  Posted is my is my rates, first when in 3.0 mode, then in 3.1 mode. 

Accepted Solution

Gold Problem Solver

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25.7K Messages

10 months ago

...  900down/25up plan ... SB8200 ... loosing it's 3.1 connection ...

Many of your downstream channel power levels are out of spec (too low), and the (presumably OFDM) 957 MHz channel power level is, as the Brits sometimes say, "right out!". Network connection problems like this are often due to poor coax connections or damaged coax cable, usually in or near your home. Running the cable through a surge protector, a defective splitter, or too many splitters can cause signal problems as well. If there is an amplifier in the line make sure it's getting power. 

If you want to troubleshoot this yourself, please see Internet Troubleshooting Tips. If you can't find the problem or you'd rather have Comcast take care of it and an employee does not respond to your message here, call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. It's not likely they can fix the problem remotely. If not, insist they send a tech out to identify the cause and correct it.

If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit (approx $100) unless you have their Service Protection Plan ( https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device or anything outside your home you shouldn't be charged.

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6 Messages

10 months ago

For some reason I don't see the ability to attach a photo so I am sharing from google docs.

So here are the connection rates from tonight... connected to DOCSIS3.0

https://drive.google.com/file/d/16_RIiKDs3-cxttEGjdnH-sk9mhTA0DKo/view?usp=drive_link

And then after a reboot connected very briefly to DOCSIS3.1 (less than 2 minutes tonight before falling back to 3.0)

https://drive.google.com/file/d/1wOG-gHEjPVT-f_9X_Sv2D1-_K9LM2hz-/view?usp=drive_link

6 Messages

10 months ago

Bruce, thanks for your insight.  Just called and I am on the waitlist for as early as tomorrow at 10AM, or 10AM Monday.  I have a confirmed appointment for Tuesday at 8AM if nothing opens Sunday or Monday. 

Didn't even fight me or try to take me through troubleshooting or rebooting the modem.  Thanks to you confirming what I thought I was confident to say I had sever downstream channels out of spec and that I have observed my modem going in and out of docsis 3.1 mode several times a day, which has cascading performance effects. 

Never before have I had them offer to send a tech the next day.  

I was looking at the line outside my house for any damage and while out there I was reminded of two recent changes. 

1. They put in a new telephone pole about a year ago and just over a month ago they came through and moved all the non power lines to the new pole and took out the old pole.  Wonder if they didn't twist down my coax all the way at the pole.  

2. I have a new neighbor moved in about 2 months ago.  House has been vacant for a year, previous owners had satellite, I noticed a new coax line running from the junction box to their house.  Would one new house on the circuit be enough to cause my low levels?

Either way thanks again Bruce for confirming what I wasn't confident enough to call with.   I'll post a follow up after the tech comes.

Gold Problem Solver

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25.7K Messages

10 months ago

... moved all the non power lines to the new pole ... new neighbor ... new coax line ...

I'd say you are right to wonder if those changes have something to do with the signal problems you are having.

... I'll post a follow up after the tech comes.

Please do! We always wonder how these things turn out.

Good luck!

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.

6 Messages

10 months ago

Update... Xfinity tech came out today.   Nice guy was well informed and had already seen my low readings and had a plan of attack.  He replaced all my coax connectors (at the modem, at the pole, at the house) to make sure we were not getting leaks there. Took one extra step and went back up the pole and moved my connect to another port, nothing changed.  Levels all read the same.  Said the issue is definitely not localized to my house. The problem is in the line that feeds the house or in the junction box that my house is connected too.  Interestingly the neighbors came out when he saw us said he has been having issues too. 

So the tech is escalating it up as this fix is more than he is trained or authorized to address. 

What seems odd to me is Xfinity must be able to monitor/level these power thresholds for the neighborhood?  If this was a neighborhood level issue, wouldn't they see it, get alerted to it?

6 Messages

10 months ago

Also after monitoring things through the day my power levels actually look worse?   Even more interesting is the number of uncorrectable that didn't exist before vs exist before.   I chatted with a support today to be sure the tech escalated the issue up and see if I could get an estimate on time frame.   This is what I was told: "our higher team is checking on this like it can take more time because they going to take a on your network it going to take at least 5 to 7 working days because it will check weekly basis"    I got a ticket number so I guess I just wait 5 to 7 days and bug them again.  

Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
20 Locked QAM256 567000000 Hz -8.9 dBmV 35.8 dB 133 615
1 Locked QAM256 453000000 Hz -3.9 dBmV 39.8 dB 0 0
2 Locked QAM256 459000000 Hz -6.2 dBmV 37.3 dB 98 472
3 Locked QAM256 465000000 Hz -7.8 dBmV 36.8 dB 88 483
4 Locked QAM256 471000000 Hz -7.2 dBmV 36.3 dB 93 477
5 Locked QAM256 477000000 Hz -7.5 dBmV 36.7 dB 98 473
6 Locked QAM256 483000000 Hz -6.6 dBmV 37.0 dB 96 475
7 Locked QAM256 489000000 Hz -7.1 dBmV 36.7 dB 83 487
8 Locked QAM256 495000000 Hz -7.1 dBmV 36.2 dB 96 474
9 Locked QAM256 501000000 Hz -7.7 dBmV 36.4 dB 97 473
10 Locked QAM256 507000000 Hz -7.5 dBmV 36.1 dB 97 473
11 Locked QAM256 513000000 Hz -7.2 dBmV 36.9 dB 93 476
12 Locked QAM256 519000000 Hz -7.4 dBmV 36.1 dB 74 496
13 Locked QAM256 525000000 Hz -6.6 dBmV 37.2 dB 87 483
14 Locked QAM256 531000000 Hz -7.4 dBmV 36.5 dB 111 465
15 Locked QAM256 537000000 Hz -8.5 dBmV 35.2 dB 458 483
16 Locked QAM256 543000000 Hz -8.8 dBmV 34.3 dB 188 475
17 Locked QAM256 549000000 Hz -7.8 dBmV 37.0 dB 123 448
18 Locked QAM256 555000000 Hz -8.0 dBmV 32.3 dB 4411277 1926661
19 Locked QAM256 561000000 Hz -7.9 dBmV 36.2 dB 395 488
21 Locked QAM256 573000000 Hz -10.0 dBmV 34.3 dB 85 486
22 Locked QAM256 579000000 Hz -10.3 dBmV 35.3 dB 107 464
23 Locked QAM256 585000000 Hz -11.4 dBmV 34.0 dB 97 476
24 Locked QAM256 591000000 Hz -10.7 dBmV 34.8 dB 93 482
25 Locked QAM256 597000000 Hz -11.6 dBmV 34.1 dB 96 476
26 Locked QAM256 603000000 Hz -12.0 dBmV 33.1 dB 133 471
27 Locked QAM256 609000000 Hz -13.8 dBmV 32.2 dB 210 487
28 Locked QAM256 615000000 Hz -16.6 dBmV 28.9 dB 2802982 474
29 Locked QAM256 621000000 Hz -15.2 dBmV 30.7 dB 1584 475
30 Locked QAM256 627000000 Hz -15.6 dBmV 30.5 dB 9688 483
31 Locked QAM256 633000000 Hz -14.7 dBmV 31.0 dB 4160 488
32 Locked QAM256 639000000 Hz -16.2 dBmV 30.2 dB 57457 484
193 Locked Other 957000000 Hz 0.9 dBmV 0.0 dB 48078870 9836070

Official Employee

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412 Messages

@NHMagicRyan We would be happy to look into your internet concerns. 

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Gold Problem Solver

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25.7K Messages

10 months ago

...  I got a ticket number so I guess I just wait 5 to 7 days and bug them again.

You're kinder than I would be. Comcast is not exactly famous for keeping their promises, nor for doing so in a expeditious manner. I'd be jumping up and down on them hollering "FIX MY . . . STUFF!". But maybe they'll surprise us. Again, good luck!

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.

6 Messages

9 months ago

Finally!  After two more tech visits!  I am fixed.   They sent a second tech out (Contractor for Comcast) after changing all the coax ends didn't work.  This one came with some kind of meter device and could see my low ends very clearly.  He replaced the line in my house (I only have two lines, pole to house, house to modem).  He didn't think it would help, but he wanted to try it first as comcast will charge for the pole to house line.   My numbers went up but still not strong enough for a docsis 3.1 connection.    So he said that was all he could do with out charging me for the pole to house line.  I needed to go so I didn't argue with him and sent him on his way.  

Contacted comcast again via chat to confirm if the line from the pole to house was my responsibility, they actually said no.  I asked can you send someone out to replace it (really scratching my head as this could of been solved in one service call).  They said yes and scheduled someone next day.   Tech showed up.. took all of 20-30 minutes and I was back up and running and have been fine for 48 hours.  The problem was my wire had been riddled with what look like tears... like a squirrel was grinding down their teeth on my wire!

So for anyone else reading this forum having the same issues... be more persistence that I am... make your sure your power levels are between -10 and +10  (Thanks Bruce for your help there) and based on my experience don't let the contractors tell you the pole to house is your responsibility. 

Look at the difference in my power and SNR numbers now, compared to 20 days ago!

Official Employee

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1.6K Messages

Hi, @NHMagicRyan! We are happy to hear that everything is now working correctly. While we have you, you should know that we are also experts in saving our valued customers money. Would you like us to do an account review to ensure you have the best deal available for your services?

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
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