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user_seaue8
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Thursday, February 20th, 2025 7:43 PM

Low Downstream Power (Netgear Nighthawk CM2500 )

Hi all,

I'm kind of new to this. I just got my own equipment and my modem is giving me a "Cable Connection Status Poor" message. It says I have low downstream power. Below is the text--any help would be greatly appreciated. I don't know what to do with the information.

Acquire Downstream Channel 651000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
IP Provisioning Mode Honor MDD IPv6 only
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 41 651000000 Hz -10.2 dBmV 37.1 dB 0 0
2 Locked QAM256 13 471000000 Hz -7.7 dBmV 38.1 dB 0 0
3 Locked QAM256 14 477000000 Hz -7.9 dBmV 38.1 dB 0 0
4 Locked QAM256 15 483000000 Hz -7.7 dBmV 38.1 dB 0 0
5 Locked QAM256 16 489000000 Hz -7.8 dBmV 38.1 dB 0 0
6 Locked QAM256 17 495000000 Hz -8.1 dBmV 37.9 dB 0 0
7 Locked QAM256 18 507000000 Hz -8.6 dBmV 37.5 dB 0 0
8 Locked QAM256 19 513000000 Hz -8.9 dBmV 37.5 dB 0 0
9 Locked QAM256 20 519000000 Hz -8.7 dBmV 37.6 dB 0 0
10 Locked QAM256 21 525000000 Hz -9.4 dBmV 37.1 dB 0 0
11 Locked QAM256 22 531000000 Hz -9.2 dBmV 37.3 dB 0 0
12 Locked QAM256 23 543000000 Hz -9.4 dBmV 36.9 dB 0 0
13 Locked QAM256 24 549000000 Hz -9.4 dBmV 37.2 dB 0 0
14 Locked QAM256 25 555000000 Hz -10.0 dBmV 36.8 dB 0 0
15 Locked QAM256 26 561000000 Hz -10.2 dBmV 36.7 dB 0 0
16 Locked QAM256 27 567000000 Hz -9.7 dBmV 37.0 dB 0 0
17 Locked QAM256 28 573000000 Hz -9.9 dBmV 37.0 dB 0 0
18 Locked QAM256 29 579000000 Hz -9.6 dBmV 37.2 dB 0 0
19 Locked QAM256 30 585000000 Hz -9.7 dBmV 37.1 dB 0 0
20 Locked QAM256 31 591000000 Hz -10.1 dBmV 36.9 dB 0 0
21 Locked QAM256 32 597000000 Hz -9.8 dBmV 37.1 dB 0 0
22 Locked QAM256 33 603000000 Hz -10.5 dBmV 36.8 dB 0 0
23 Locked QAM256 34 609000000 Hz -10.2 dBmV 37.0 dB 0 0
24 Locked QAM256 35 615000000 Hz -10.0 dBmV 37.1 dB 0 0
25 Locked QAM256 36 621000000 Hz -10.0 dBmV 37.1 dB 0 0
26 Locked QAM256 37 627000000 Hz -9.9 dBmV 37.2 dB 0 0
27 Locked QAM256 38 633000000 Hz -10.3 dBmV 36.9 dB 0 0
28 Locked QAM256 39 639000000 Hz -10.3 dBmV 37.0 dB 0 0
29 Locked QAM256 40 645000000 Hz -9.9 dBmV 37.3 dB 0 0
30 Locked QAM256 42 657000000 Hz -9.7 dBmV 37.4 dB 0 0
31 Locked QAM256 43 663000000 Hz -10.0 dBmV 37.2 dB 0 0
32 Locked QAM256 44 669000000 Hz -9.9 dBmV 37.3 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 5 5120 Ksym/sec 35600000 Hz 47.5 dBmV
2 Locked ATDMA 1 2560 Ksym/sec 10400000 Hz 47.5 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 16400000 Hz 46.0 dBmV
4 Locked ATDMA 3 5120 Ksym/sec 22800000 Hz 47.0 dBmV
5 Locked ATDMA 4 5120 Ksym/sec 29200000 Hz 47.0 dBmV
6 Locked ATDMA 6 2560 Ksym/sec 40400000 Hz 48.5 dBmV
7 Not Locked Unknown 0 0 0 0.0 dBmV
8 Not Locked Unknown 0 0 0 0.0 dBmV
 
Downstream OFDM Channels
Channel Lock Status Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier
Number Range		 Unerrored
Codewords		 Correctable
Codewords		 Uncorrectable
Codewords
1 Locked 0 ,1 ,2 ,3 159 722000000 Hz -9.32 dBmV 37.2 dB 946 ~ 3149 291802148 148015389 0
2 Not Locked 0 0 0 Hz 0 dBmV 0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV

Question

 • 

Updated 

3 months ago

 • Edited

65

2

0

Accepted Solution

EG

Expert

 • 

110.5K Messages

3 months ago

Yep. The downstream power is indeed too low / out of spec on most of the channels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels. Are you actually experiencing any of those issues ?

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are 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 from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

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.


Good luck with it !

1

user_seaue8

5 Messages

@EG​ Hello--thank you very much for getting back to me. I appreciate the detailedness of your reply.

I do experience some of those issues--latency being foremost among them. Lots of inexplicable lag spikes, especially after a fairly big storm in my area.

The internet does occasionally disconnect, too. Usually the whole modem won't restart but the upstream light or downstream light will flash.

The Netgear modem wasn't reporting packet loss, but I had to switch to an Arris Surfboard S34 (unrelated reasons) and that modem does report packet loss, especially on this channel:

159 Locked OFDM PLC 722000000 Hz -8.8 dBmV 38.0 dB 1157227147 160

There was some packet loss on three other channels too, but very minor and no uncorrectables. 

The coax cable coming out of the wall and into the modem is fine. Otherwise, I have no clue how to go about checking all those things--the owners of this property have forbidden me from "tearing up the yard."

Thanks again--and I'm sorry for my belated response--I hadn't received any notification of it.

 

Like

Reply

3 months ago

XfinityAldrik

Official Employee

 • 

2.2K Messages

3 months ago

Thank you for reaching out to us @user_seaue8! I see @EG shared some really helpful tips, thank you for your help!

 

Have you been experiencing random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels?

 

Are all the coaxial connections going into the modem and the wall outlet the modem is connected to are finger tight? If there is a splitter between the modem and wall outlet, we will want to make sure all the splitters' connections are finger tight.

4

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