Community Forum

Slow upload speed: only 2 of 5 upstream channels are locked.

tomwyn
Frequent Visitor

Slow upload speed: only 2 of 5 upstream channels are locked.

I have Xfinity Gigabit service, using the Motorola MB8600 DOCSIS 3.1 cable modem.  My download speed is fine.  All bonded channels are locked and I get up to 900Mbps.   However, my upload speed is typically 20MBps, lower than the expected speed of 35MBps.

My neighbor has the same service, and he gets 40Mbps for upload.  All 5 of his Upstream Bonded Channels are locked. 

Is this why I get slower upload speed?

 

Also, without an Arris cable amplifier, my upstream channel power goes up about 5dBmV more than what's shown below (up to 58 dBmV)

Can both of these problems be solved by a Xfinity tech checking the cable connections at the drop (on the pole)?

 

My modem --- Upstream Bonded Channels

Channel Lock Ch.Type ID Ksym/ Freq. Pwr (dBmV)
1 Not Locked SC-QAM  6  5120  17.3  52.3
2 Not Locked SC-QAM  7  5120  23.7  50.8
3 Not Locked SC-QAM  8  5120  30.3  46.3
4 Locked     SC-QAM  9  5120  36.7  50.3
5 Locked     SC-QAM 10  1280  41.2  50.8

EG
Expert

Re: Slow upload speed: only 2 of 5 upstream channels are locked.

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.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
tomwyn
Frequent Visitor

Re: Slow upload speed: only 2 of 5 upstream channels are locked.

Thank you so much, EG.   I already troubleshooted all my internal cables when a tech came to my house recently.      I'd need to ping the Comcast tech again to fix things at the drop. 

I wonder why only 2 of the 5 channels are locked.  Is it  because there isn't enough network capacity in my neighborhood?  The tech mentioned that Comcast is upgrading the network capacity in my neighborhsood. But my neighbor gets the full bandwidth.    The tech said that the upstream power can go up to 55, while the recommendation on the internet is only 50. 

EG
Expert

Re: Slow upload speed: only 2 of 5 upstream channels are locked.

No. 55 is wrong. They are conning you...The upstream power has nothing to do with capacity. Only an RF signal impairment can make it go higher.

 

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.

Good luck with it !



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!