CM1200 Modem Upstream LED Flashing - Spectrum Internet

I've had this modem for just over a year and it started dropping signal a couple days ago. The upstream LED was flashing green so I had a tech from Spectrum come out and check on everything. They pro...

FURRYe38

Guru - Experienced User

Jan 12, 2021

You would need to check to be sure.

Your power levels seems a bit high...

Heres mine:

Startup Procedure

Procedure	Status	Comment
Acquire Downstream Channel	837000000 Hz	Locked
Connectivity State	OK	Operational
Boot State	OK	Operational
Security	Enabled	BPI+
IP Provisioning Mode	Honor MDD	honorMdd(4)

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Correctables	Uncorrectables
1	Locked	QAM256	31	837000000 Hz	-2.5 dBmV	37 dB	0	0
2	Locked	QAM256	1	651000000 Hz	-2.5 dBmV	36.4 dB	0	0
3	Locked	QAM256	2	657000000 Hz	-2.6 dBmV	36.4 dB	0	0
4	Locked	QAM256	3	663000000 Hz	-2.3 dBmV	36.6 dB	0	0
5	Locked	QAM256	4	669000000 Hz	-2.3 dBmV	36.6 dB	0	0
6	Locked	QAM256	5	675000000 Hz	-2.1 dBmV	36.7 dB	0	0
7	Locked	QAM256	6	681000000 Hz	-2 dBmV	36.9 dB	0	0
8	Locked	QAM256	7	687000000 Hz	-1.8 dBmV	36.8 dB	0	0
9	Locked	QAM256	8	693000000 Hz	-1.7 dBmV	36.9 dB	0	0
10	Locked	QAM256	9	699000000 Hz	-1.5 dBmV	37 dB	0	0
11	Locked	QAM256	10	705000000 Hz	-1.5 dBmV	36.8 dB	0	0
12	Locked	QAM256	11	711000000 Hz	-1.3 dBmV	36.9 dB	0	0
13	Locked	QAM256	12	717000000 Hz	-0.8 dBmV	37.1 dB	0	0
14	Locked	QAM256	13	723000000 Hz	-1 dBmV	36.9 dB	0	0
15	Locked	QAM256	14	729000000 Hz	-0.7 dBmV	36.9 dB	0	0
16	Locked	QAM256	16	741000000 Hz	-0.6 dBmV	37.1 dB	0	0
17	Locked	QAM256	17	753000000 Hz	-0.7 dBmV	37.2 dB	0	0
18	Locked	QAM256	18	759000000 Hz	-0.9 dBmV	37.1 dB	0	0
19	Locked	QAM256	19	765000000 Hz	-1.3 dBmV	37.1 dB	0	0
20	Locked	QAM256	20	771000000 Hz	-1.3 dBmV	37.2 dB	0	0
21	Locked	QAM256	21	777000000 Hz	-1.5 dBmV	37.3 dB	0	0
22	Locked	QAM256	22	783000000 Hz	-1.7 dBmV	37.3 dB	0	0
23	Locked	QAM256	23	789000000 Hz	-1.7 dBmV	37.4 dB	0	0
24	Locked	QAM256	24	795000000 Hz	-1.9 dBmV	37.3 dB	0	0
25	Locked	QAM256	25	801000000 Hz	-2.1 dBmV	37.1 dB	0	0
26	Locked	QAM256	26	807000000 Hz	-2 dBmV	37.2 dB	0	0
27	Locked	QAM256	27	813000000 Hz	-2 dBmV	37.2 dB	0	0
28	Locked	QAM256	28	819000000 Hz	-2.4 dBmV	36.9 dB	0	0
29	Locked	QAM256	29	825000000 Hz	-2.3 dBmV	37.2 dB	0	0
30	Locked	QAM256	30	831000000 Hz	-2.3 dBmV	37.1 dB	0	0
31	Locked	QAM256	32	843000000 Hz	-2.5 dBmV	37 dB	0	0
32	Not Locked	Unknown	0	0 Hz	0.0 dBmV	0.0 dB	0	0

Upstream Bonded Channels

Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	1	5120 Ksym/sec	36000000 Hz	38.8 dBmV
2	Locked	ATDMA	2	5120 Ksym/sec	29000000 Hz	37.5 dBmV
3	Locked	ATDMA	5	5120 Ksym/sec	22000000 Hz	38 dBmV
4	Locked	ATDMA	6	2560 Ksym/sec	16000000 Hz	37 dBmV
5	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
6	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
7	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
8	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV

Downstream OFDM Channels

Channel	Lock Status	Modulation / Profile ID	Channel ID	Frequency	Power	SNR / MER	Active Subcarrier Number Range	Unerrored Codewords	Correctable Codewords	Uncorrectable Codewords
1	Locked	0 ,1 ,2	33	547000000 Hz	-4.0 dBmV	36.5 dB	1108 ~ 2987	107438938	87612859	0
2	Not Locked	0	0	0 Hz	0 dBmV	0.0 dB	0 ~ 4095	0	0	0

WaveWarper

Aspirant

Jan 12, 2021

Thanks for that. They said the power seems fine (I just asked again). Is there anything I can do on the modem side to rule out it is not faulty? I want to be able to bring some ammo back to Spectrum so they can't punt it back. As of now their provided modem is working, so I don't have a lot of leverage.

plemans
Guru - Experienced User
Jan 12, 2021
You're actually the first person with a locked upstream on the ofdma channels I've seen.
You're power levels are technically within spec. You didn't post your whole logs but the one had a dynamic window violation and t3 errors. Dynamic window violations usually occur when the power gets to high/low for a period of time. it can cause instabilities.
Your power levels are also a little backwards. Usually when you're power level on the upstream is high, it means you're close to the node so you tend to have a lower upstream level because it doesn't take as much power to communicate with the node.
Is there an amplifier in the line?
Also, have you tried checking off the "enable extended upstream transmit power"
- WaveWarper
  Aspirant
  Jan 12, 2021
  The "power" box is right outside the window from the modem, so the cable run is pretty short. I'm not sure if there is amp or not though. I will try giving the checkbox a try.
  
  Thank you!
  - ctem81
    Star
    Jan 29, 2021
    You are the victim of OFDMA being enabled on the upload channels. Modem running 1.02.01 breaks when OFDMA is enabled. You can read my journey here. https://www.dslreports.com/forum/r32832397-Netgear-CM1200-is-now-crap-OFDMA-just-enabled-on-upstream

Forum Discussion

CM1200 Modem Upstream LED Flashing - Spectrum Internet