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

Responses

Accepted Solution

EG

Expert

•

109.7K Messages

2 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

U

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.

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2 months ago

XfinityAldrik

Official Employee

•

2.1K Messages

2 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

U

user_seaue8

5 Messages

@XfinityAldrik Hello--thanks for getting back to me. I am indeed experiencing some of those things, especially latency problems.

I talked to someone over the phone who said that any tech visits in the first 30 days would come with an installation fee, so I guess I'm waiting out the first 30 days.

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2 months ago

0

XfinityAldrik

Official Employee

•

2.1K Messages

I appreciate you for confirming these details @user_seaue8! There could be a charge for the visit if the technician makes any repairs, replacements, or reconfiguration of the wiring in your home or if the issue is caused by the new modem. The appointment fee covers the cost to inspect the interior and exterior wires as well as replace any of the connections if needed. If there are any interior wires that need to be replaced by wall fishing, a qualified third-party contractor or electrician will be needed to complete the work. A wall fish is a method of running and “fishing” wiring through the drywall.

When working with one of our representatives over the phone, did they mention a technician was recommended while troubleshooting your services?

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2 months ago

0

U

user_seaue8

5 Messages

@XfinityAldrik Yes, the person I spoke with over the phone recommended that a tech come out.

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2 months ago

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XfinityChristy

Official Employee

•

1.9K Messages

user_seaue8 Good morning. I would be happy to help you get that appointment set up . To get started, please send our team a Direct Message with your full name, the name listed on the account (if different), and the service address associated with your account.

To send a "Direct Message" message:

Click "Sign In" if necessary

Click the "Direct Messaging" icon at the top of the page (looks like a text bubble)

Click the "New message" (pencil and paper) icon

Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list that appears. The "Xfinity Support" graphic replaces the "To:" line

Type your message in the text area near the bottom of the window

Press Enter to send it

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer. tick

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2 months ago

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Your Home Network

user_seaue8

Low Downstream Power (Netgear Nighthawk CM2500 )

EG

user_seaue8

XfinityAldrik

user_seaue8

XfinityAldrik

user_seaue8

XfinityChristy

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