dolo5's profile

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Mon, May 18, 2020 12:00 PM

Sharp Decline in Upload Speeds

Over the last week, my upload speeds have become slower and slower, making it impossible to have relaible voice and video calls.  I'm in SF with a 100/5 tier package.  When I run speed tests on Google, Ookla, Xfinity Speed Test, DSL Reports etc, I see download speeds of 75-88, and upload speeds that often average less than 1 Mbps. Two interesting things:  (1) the tests show that upload speeds initially spike to 5-8 Mbps and then quickly decline till they get to zero, and (2) this issue disappears over the weekend, when upload speeds are stable in the 5-8 Mbps range.  My cable modem was a Sb6141 , which I replaced with an Mb7621 over the weekend, but the issue remains.  I am connecting through a Netgear r6400 router, which I've rebooted to factor settings and uploaded all firmware on, without improvement.  **I know I need to test levels directly from modem to computer, but am waiting on delivery of the adapter that will let me do this.**. Here is a paste of what I'm seeing on the cable modem.  Any ideas on what's causing this?  I have a tech visit scheduled for tomorrow, is this likely to help?


   Upstream Bonded Channels




   Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
1 Locked ATDMA 2 5120 22.8 51.3
2 Locked ATDMA 3 5120 29.2 50.8
3 Locked ATDMA 1 5120 16.4 52.0
4 Locked ATDMA 4 5120 35.6 50.0
5 Locked ATDMA 5 1280 40.4 49.5
6 Not Locked Unknown 0 0 0 0.0
7 Not Locked Unknown 0 0 0 0.0
8 Not Locked Unknown 0 0 0 0.0






86.6K Messages

1 y ago

The upstream power is too high and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, and latency problems.

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.

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