Very slow upload speed

Yes, the signal level image is visible now. The downstream channel levels are weak, and the upstream levels are too high. And the "Dynamic Range Window violation", "Commanded Power Exceeds" and other errors in the log suggest an intermittent coax connection.

Signal problems are often due to loose, damaged, or corroded coax or coax connectors, usually in or near your home. If you can't find the problem or you'd rather have Comcast take care of it, 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/. If they can't fix the problem remotely (unlikely), 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 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.

The image you posted isn't visible. It looks like this:

This is probably because you are a new poster and the image requires moderator approval. That could take a while. If you don't want to wait you could upload the image to a file sharing site and post a link to it here, or post text instead of an image.

Meanwhile please see Connection Troubleshooting Tips and Information Requested for Connection-Related Posts.

Thank you for that information, Bruce. I noticed that when I posted, but had to leave. Now it appears to be working. I will start reading through the troubleshooting link you you sent.

• Post your modem’s error logs. 
  • See below.
  • [REDACTED] = CM1150V
  • [REDACTED_2] = Local Comcast
• Post the make and model of your modem/gateway.
  • Netgear CM1150V
• Post the make and model of your router if you have one.
  • Issue resides when connected directly to the modem, even after a fresh restart.
• Let us know if you contacted Comcast or had a tech visit.
  • Not yet.
• Let us know what the lights on your modem are doing when you are having problems.
  • Power, Up link, Down link, WWW, both phone line lights are solid green. LAN light flickers green, as usual.

Error Logs

"Event Logs" per Netgear Genie interface:

Thank you for your insight! I really appreciate it. I think I'll move the gateway to the first splitter in the basement, disconnect everything else, and check the singal levels there before calling Comcast - just to mitigate the risk of being charged for the visit.

Per the link you sent, I'm targeting these levels, correct?

Downstream Power Levels: -8dBmV to  +10dBmV (Currently too low at -11.4 to -9.0)

Downstream Signal to Noise Ratio (SNR):  >35dB  (Currently fine)

Upstream Power Level:  +25dBmV to +54dBmV (Currently too high at +55.5)

Upstream Signal to Noise Ratio (uSNR): >31dB   (Currently unknown?)

Upstream Receive Power: -2dBmV to +2dBmV (Currently unknown?)

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@CnSWEST wrote: ... I think I'll move the gateway to the first splitter in the basement, disconnect everything else, and check the singal levels there before calling Comcast ...

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I think that's a solid plan.

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... Per the link you sent, I'm targeting these levels, correct? ...

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Correct, except that I always like to see upstream power below +50 dBmV if possible. To me, +54 is borderline/too high, but that's how some modems run.

Note that Upstream Signal to Noise Ratio (uSNR) and Upstream Receive Power can only be measured by Comcast, not at the modem. Some reps know enough to find them for you, most do not.

Please let us know your results, thanks.

Here are the results of being attached directly to the incoming coax line for the house.

Per our discussions:

Downstream Power Levels: -8dBmV to  +10dBmV

Office: Currently too low at -11.4 to -9.0

PoE: On the high side. 7 to 10.1

Downstream Signal to Noise Ratio (SNR):  >35dB

Office: fine.

PoE: fine. 40.9 to 41.6 dB

Upstream Power Level:  +25dBmV to +50dBmV

Office: Too high, +55.5

PoE: fine. 40.5 dBmV.

Notably, I ran a speed test connected to the modem and had the same results as I have in the office. 360 down, ~10 up. Do you think this is sufficient for Comcast to investigate the matter without charging me?

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@CnSWEST wrote:

Here are the results of being attached directly to the incoming coax line for the house.

 

 

Per our discussions:

Downstream Power Levels: -8dBmV to  +10dBmV

Office: Currently too low at -11.4 to -9.0

PoE: On the high side. 7 to 10.1

Downstream Signal to Noise Ratio (SNR):  >35dB

Office: fine.

PoE: fine. 40.9 to 41.6 dB

Upstream Power Level:  +25dBmV to +50dBmV

Office: Too high, +55.5

PoE: fine. 40.5 dBmV.

 

Notably, I ran a speed test connected to the modem and had the same results as I have in the office. 360 down, ~10 up. Do you think this is sufficient for Comcast to investigate the matter without charging me?

 

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Can't see your picture just yet.

+7 to +10.1 is still on the high side but ok for being at PoE. Other than not knowing the uSNR nor the Upstream Receive Power currently, especially from the PoE, everything else seems fine from PoE indicating the problem could be inside as you are losing way too much from PoE to office. Are there any splitters that are not needed or are the connections tight?

If the tech finds the problem to be on your side of the demarcation point, you will likely be charged.

Some stuff that you can try before you call;

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there 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 types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

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.

Here's the route trace from PoE to office:

1. PoE
2. MoCA Filter (Holland B00DC8IEE6)
3. VoIP Amp and MoCA splitter, powered and grounded (Commscope CSMAPDU9VPI) - 6 alt paths connected, 1 used: media center MoCA adapter.
4. RG6/U, ~30ft
5. 2-way splitter (Holland GHS-2Pro-M) - 1 alt path connected, 0 unused
6. RG6/U, ~40ft
7. 3-way splitter (Ideal 85-333) - 2 alt paths connected, 0 used
8. RG6/U, ~10ft
9. RG6 keystone jack (VCE 4335095229)
10. RG6/U, ~3ft
11. 2-way splitter (GE 33526) - alt path used: MoCA adapter
12. RG6/U, ~1ft
13. Modem (Netgear CM1150V)

At the point of entry I am getting <50% of the advertised upload speed at best. That's the same result I'm getting when the modem is connected in my office. Do you not agree, then, that the root cause of the slow upload speed is independent of anything to do with my property? I'd rather divert my attention to the root cause of the immediate problem before improving my home network.

meant to say I get 14.7 upload after 5 pm, and about 2-5 mbs upload from 11 am - 5 pm.  The advertised speeds only apply when few people are using the internet.  That's why fiber optic is needed rather than shared cable internet.

Dead thread from last year now being closed.