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user_ffb328
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Monday, March 20th, 2023 8:34 PM

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problem on only 2 downstream channels

I recently upgraded from a docsis 3.0 to a 3.1 cable modem.  The new modem is an Arris SB8200.  I seem to be having trouble on 2 downstream channels:

37 Locked Other 690000000 Hz 2.2 dBmV 38.2 dB 89392525 104
38 Not Locked QAM256 0 Hz 0.0 dBmV 40.5 dB 0 0

Is this a problem that has to be corrected, will it cause me issues?  Here's the entire status table:

Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
42 Locked QAM256 639000000 Hz 3.7 dBmV 40.7 dB 0 0
14 Locked QAM256 471000000 Hz 4.3 dBmV 41.8 dB 0 0
15 Locked QAM256 477000000 Hz 4.4 dBmV 42.1 dB 0 0
16 Locked QAM256 483000000 Hz 3.9 dBmV 41.6 dB 0 0
17 Locked QAM256 489000000 Hz 3.9 dBmV 41.6 dB 0 0
18 Locked QAM256 495000000 Hz 3.8 dBmV 41.5 dB 0 0
19 Locked QAM256 507000000 Hz 3.8 dBmV 41.7 dB 0 0
20 Locked QAM256 513000000 Hz 3.3 dBmV 41.5 dB 0 0
21 Locked QAM256 519000000 Hz 2.7 dBmV 41.1 dB 0 0
22 Locked QAM256 525000000 Hz 3.2 dBmV 41.7 dB 0 0
23 Locked QAM256 531000000 Hz 2.6 dBmV 40.9 dB 0 0
24 Locked QAM256 537000000 Hz 3.0 dBmV 41.2 dB 0 0
25 Locked QAM256 543000000 Hz 3.1 dBmV 41.2 dB 0 0
26 Locked QAM256 549000000 Hz 2.6 dBmV 40.8 dB 0 0
27 Locked QAM256 555000000 Hz 3.0 dBmV 41.1 dB 0 0
28 Locked QAM256 561000000 Hz 2.9 dBmV 41.1 dB 0 0
29 Locked QAM256 567000000 Hz 2.6 dBmV 40.8 dB 0 0
30 Locked QAM256 573000000 Hz 3.2 dBmV 41.1 dB 0 0
31 Locked QAM256 579000000 Hz 2.8 dBmV 40.8 dB 0 0
32 Locked QAM256 585000000 Hz 2.8 dBmV 40.9 dB 0 0
33 Locked QAM256 591000000 Hz 3.4 dBmV 41.1 dB 0 0
34 Locked QAM256 597000000 Hz 3.4 dBmV 40.9 dB 0 0
35 Locked QAM256 603000000 Hz 3.7 dBmV 41.0 dB 0 0
36 Locked QAM256 609000000 Hz 3.4 dBmV 40.8 dB 0 0
37 Locked Other 690000000 Hz 2.2 dBmV 38.2 dB 89392525 104
38 Not Locked QAM256 0 Hz 0.0 dBmV 40.5 dB 0 0
39 Locked QAM256 615000000 Hz 3.4 dBmV 40.9 dB 0 0
40 Locked QAM256 621000000 Hz 3.7 dBmV 40.6 dB 0 0
41 Locked QAM256 627000000 Hz 3.4 dBmV 40.4 dB 0 0
43 Locked QAM256 633000000 Hz 3.3 dBmV 40.3 dB 0 0
44 Locked QAM256 645000000 Hz 3.2 dBmV 40.4 dB 0 0
45 Locked QAM256 651000000 Hz 3.2 dBmV 40.4 dB 0 0


Upstream Bonded Channels
Channel Channel ID Lock Status US Channel Type Frequency Width Power
1 2 Locked SC-QAM Upstream 16400000 Hz 6400000 Hz 38.0 dBmV
2 3 Locked SC-QAM Upstream 22800000 Hz 6400000 Hz 38.0 dBmV
3 4 Locked SC-QAM Upstream 29200000 Hz 6400000 Hz 38.0 dBmV
4 5 Locked SC-QAM Upstream 35600000 Hz 6400000 Hz 38.0 dBmV
5 6 Locked SC-QAM Upstream 40400000 Hz 3200000 Hz 40.0 dBmV

Question

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Updated 

2 years ago

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Accepted Solution

EG

Expert

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110.1K Messages

2 years ago

Channel 37 (Other) is the OFDM / PLC channel. It is a very wide bandwidth channel that packs a lot of data within. Due to that fact, seeing a large number of corrected errors is normal. The FEC (Forward Error Correction) circuitry / system is doing its job. All of those errors are *corrected* ones. 

And as far as channel number 38 showing as being "not locked", many, if not most local systems have gone down from using 32 QAM 256 DOCSIS 3.0 downstream channels to now using only 31 since the implementation of the DOCSIS 3.1 / OFDM channel. So that would be normal as well. The SNR value reading is an aberration.

(edited)

1

user_ffb328

Visitor

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2 Messages

@EG​ Thank you so much for the quick reply and the information!  I'm not having any issues, but it looked odd to me, so I thought i would ask. 

2 years ago

0

EG

Expert

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110.1K Messages

2 years ago

@user_ffb328 

Quite welcome ! 

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