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Not Locked downstream channels

Abcnow
New Poster

Not Locked downstream channels

I'm using a Motorola MB7621 cable modem.

I noticed that if the frequency of a downstream channel is below 500MHz, that channel is "Not Locked".

A Motorola tech says this is under Comcast's control.

 

How can that be fixed?

 

EG
Expert

Re: Not Locked downstream channels

Please post the entire signal status page.



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Abcnow
New Poster

Re: Not Locked downstream channels

Connection page from modem

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
1 Locked QAM256 24 549.0 0.2 40.3 199 15
2 Not Locked Unknown 0 447.0 0.0 0.0 0 0
3 Not Locked Unknown 0 453.0 0.0 0.0 0 0
4 Not Locked Unknown 0 459.0 0.0 0.0 0 0
5 Not Locked Unknown 0 465.0 0.0 0.0 0 0
6 Not Locked Unknown 0 471.0 0.0 0.0 0 0
7 Not Locked Unknown 0 477.0 0.0 0.0 0 0
8 Not Locked Unknown 0 483.0 0.0 0.0 0 0
9 Not Locked Unknown 0 489.0 0.0 0.0 0 0
10 Locked QAM256 16 495.0 -13.8 29.4 526734661 27007959
11 Locked QAM256 17 507.0 -1.9 34.3 517 2004
12 Locked QAM256 18 513.0 -0.6 39.5 450 1566
13 Locked QAM256 19 519.0 -0.8 40.0 192 34
14 Locked QAM256 20 525.0 -0.5 37.7 163 68
15 Locked QAM256 21 531.0 0.1 40.1 144 38
16 Locked QAM256 22 537.0 0.1 40.3 170 45
17 Locked QAM256 23 543.0 0.9 41.3 183 15
18 Locked QAM256 25 555.0 0.9 41.2 179 2
19 Locked QAM256 26 561.0 0.6 41.2 166 3
20 Locked QAM256 27 567.0 0.3 41.2 175 13
21 Locked QAM256 28 573.0 0.6 41.0 131 15
22 Locked QAM256 29 579.0 0.5 41.2 144 8
23 Locked QAM256 30 585.0 0.1 41.1 169 7
24 Locked QAM256 31 591.0 -0.6 40.8 193 3
Total 526737836 27011795

EG
Expert

Re: Not Locked downstream channels

Please also post the upstream power figures.

 

Have you tried power-cycling / rebooting the modem ?



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Abcnow
New Poster

Re: Not Locked downstream channels

The modem is a 24x8 channels.

Reset doesn't usually make a difference. It did 2 weeks ago, when all 24 download channels were Locked. I happened to save that information, and indeed, all freq. are above 549MHz.

 

Here are the upload channels:

Upstream Bonded Channels

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
1 Locked ATDMA 86 5120 25.7 52.3
2 Locked ATDMA 85 5120 19.3 52.8
3 Locked ATDMA 87 5120 32.3 52.0
4 Locked ATDMA 88 5120 38.7 54.0
5 Not Locked Unknown 0 0 0 0.0
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

EG
Expert

Re: Not Locked downstream channels

The upstream power is too high / out of spec. It appears that there is a connection quality problem / signal impairment (and that would affect the downstream channels as well). 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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