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Only one upstream channel

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Frequent Visitor

Only one upstream channel

So currently we've got a Motorola MB7621 modem hooked up. Seeing all 24 downstream channels but only getting a single upstream with a high power level of 57dBmV. It is connected to a splitter that also feeds the cable box for TV. I've read that this can be caused by too many splitters. As far as I know, the splitter we have for the two services is the only one. We are in an apartment however which means there are way more splitters going on before our apartment. I will also note that our signal is weak in general so a tech installed an amplifier some years ago.

 

Is there anything I can do to help it?

 

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Expert

Re: Only 1 bonded upstream channel

The upstream power is way too high / out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

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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Re: Only 1 bonded upstream channel

I spoke with support today and despite all my detailed information he just blamed it on my modem. How are they not able to see that they are not getting a proper connection to my modem?
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Expert

Re: Only 1 bonded upstream channel

Did any of the self troubleshooting stuff that I supplied apply ?



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Re: Only 1 bonded upstream channel

All of those have been checked. Most direct connection possible, shortest cables possible, splitter is from Comcast, everything snug, no kinks or anything like that. The amplifier seems to be working fine.
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Expert

Re: Only 1 bonded upstream channel

Then you'll need a tech out to investigate. Good luck with it !



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Re: Only 1 bonded upstream channel

Maybe i'll try calling them again because when I chatted with a support person they insisted it was my modem that was the issue.  : /

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Re: Only 1 bonded upstream channel

One thing I noticed, that the modulation on my one upstream channel is ATDMA which isn’t even DOCSIS 3.0. Is that right? I also noticed that some others that have this issue still see some other available channels but they aren’t locked. It seems like Comcast isn’t even making those an option for my modem.
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Expert

Re: Only 1 bonded upstream channel

Those two terms / properties are not directly related. 



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