CAX80: Poor Cable Connection Status

[brownbear55]

Hi everyone. I have Xfinity's Gig speed Internet plan and recently purchased the Nighthawk CAX80. Currently, its cable connection status shows as poor.

I did a quick search in the forums and I come across multiple responses that state to have the ISP come out to check the line up to the modem. Before I do that, I was wondering if anyone had any interpretation on the diagnostic results below:

Startup Procedure

Procedure Status Comment Acquire Downstream Channel 405 MHz Locked Connectivity State OK Operational Boot State OK Operational Security Enabled BPI+

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked 256 QAM 38 405000000 Hz 12.4 dBmV 40.8 dB 0 0 2 Locked 256 QAM 1 483000000 Hz 12.3 dBmV 40.8 dB 0 0 3 Locked 256 QAM 2 489000000 Hz 12.2 dBmV 40.8 dB 0 0 4 Locked 256 QAM 3 495000000 Hz 12.1 dBmV 40.8 dB 0 0 5 Locked 256 QAM 4 501000000 Hz 12.0 dBmV 40.8 dB 0 0 6 Locked 256 QAM 5 507000000 Hz 12.0 dBmV 40.9 dB 0 0 7 Locked 256 QAM 6 513000000 Hz 11.9 dBmV 40.9 dB 0 0 8 Locked 256 QAM 7 519000000 Hz 11.9 dBmV 41.1 dB 0 0 9 Locked 256 QAM 8 525000000 Hz 11.9 dBmV 41.2 dB 0 0 10 Locked 256 QAM 9 531000000 Hz 11.8 dBmV 41.2 dB 0 0 11 Locked 256 QAM 10 537000000 Hz 11.8 dBmV 41.3 dB 0 0 12 Locked 256 QAM 11 543000000 Hz 11.6 dBmV 41.3 dB 0 0 13 Locked 256 QAM 12 549000000 Hz 11.6 dBmV 41.3 dB 0 0 14 Locked 256 QAM 13 555000000 Hz 11.6 dBmV 41.3 dB 0 0 15 Locked 256 QAM 14 561000000 Hz 11.5 dBmV 41.3 dB 0 0 16 Locked 256 QAM 15 567000000 Hz 11.5 dBmV 41.7 dB 0 0 17 Locked 256 QAM 16 573000000 Hz 11.3 dBmV 41.6 dB 0 0 18 Locked 256 QAM 17 579000000 Hz 11.4 dBmV 41.7 dB 0 0 19 Locked 256 QAM 18 585000000 Hz 11.5 dBmV 41.6 dB 0 0 20 Locked 256 QAM 19 591000000 Hz 11.4 dBmV 41.7 dB 0 0 21 Locked 256 QAM 25 459000000 Hz 12.3 dBmV 40.6 dB 0 0 22 Locked 256 QAM 34 465000000 Hz 12.2 dBmV 40.7 dB 0 0 23 Locked 256 QAM 35 471000000 Hz 12.3 dBmV 40.8 dB 0 0 24 Locked 256 QAM 36 477000000 Hz 12.3 dBmV 40.8 dB 0 0 25 Locked 256 QAM 39 411000000 Hz 12.3 dBmV 40.7 dB 0 0 26 Locked 256 QAM 40 417000000 Hz 12.3 dBmV 40.7 dB 0 0 27 Locked 256 QAM 41 423000000 Hz 12.3 dBmV 40.7 dB 0 0 28 Locked 256 QAM 42 429000000 Hz 12.4 dBmV 40.7 dB 0 0 29 Locked 256 QAM 43 435000000 Hz 12.4 dBmV 40.6 dB 0 0 30 Locked 256 QAM 44 441000000 Hz 12.2 dBmV 40.5 dB 0 0 31 Locked 256 QAM 45 453000000 Hz 12.3 dBmV 40.6 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 8 5120 Ksym/sec 16400000 Hz 35.0 dBmV 2 Locked ATDMA 5 5120 Ksym/sec 35600000 Hz 36.0 dBmV 3 Locked ATDMA 6 5120 Ksym/sec 29200000 Hz 36.0 dBmV 4 Locked ATDMA 7 5120 Ksym/sec 22800000 Hz 35.8 dBmV 5 Locked ATDMA 10 1280 Ksym/sec 39600000 Hz 41.8 dBmV 6 Not Locked Unknown 0 0 0 0.0 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 Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked 0 ,1 ,2 ,3 37 690000000 Hz 13.28 dBmV 41.6 dB 1108 ~ 2987 76989044 54742587 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

[plemans · Accepted solution]

Your power levels are to high. 

You need a 3-6db attenuator or a 3-4x splitter in line to get the power down a bit. 

The power level should be between-7.5dbmv and 7.5dbmv. You're above 12. 

[plemans · Accepted solution]

Your power levels are to high. 

You need a 3-6db attenuator or a 3-4x splitter in line to get the power down a bit. 

The power level should be between-7.5dbmv and 7.5dbmv. You're above 12. 

[Kitsap]

Technically the power level is the responsibility of the ISP.  More frequently today, end users that own their own modems find the ISPs are less than responsive to requests for support.

@plemansrecommendation to add a splitter or attenuator to the line is action you can take.  If you do not have either of these items, they are available for a reasonable cost from Amazon.  If you use a splitter, be sure and buy caps to cap off any unused connections.  Make sure both the splitter and attenuator are specified for cable TV frequency range, usually up to 3 GHz.

[brownbear55]

By using a coaxial splitter to slightly reduce the power, would I then see increased speeds or at least in theory?

[brownbear55]

I used the Xfinity app and walked through the prompts for slow connection and using a variety of responses, Xfinity always places the responsibility of slow connection speeds on not themselves.

[Kitsap]

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@brownbear55 wrote:

By using a coaxial splitter to slightly reduce the power, would I then see increased speeds or at least in theory?

---

You are way too hung up on throughput (speed).

If your cable input signal power levels are not within specification, the modem will not have a chance to do the job it was designed to do.

Give your modem a chance to do it's job.  If you still have throughput problems, work your way downstream to find the problem.

[Kitsap]

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@brownbear55 wrote:

I used the Xfinity app and walked through the prompts for slow connection and using a variety of responses, Xfinity always places the responsibility of slow connection speeds on not themselves.

---

Surprise!  Surprise!  NOT

[brownbear55]

I placed an order for a 6db attenuator. It should be here within a week. I'll post results after I install it and run another diagnostic.

[Kitsap]

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@brownbear55 wrote:

I placed an order for a 6db attenuator. It should be here within a week. I'll post results after I install it and run another diagnostic.

---

When the attenuator arrives, power down you modem before you connect it in line.  Then power up your modem and give it time to boot and stabilize.

[brownbear55]

@plemans @Kitsap Thank you for your contributions and input! I installed the db attenuator (powered down the modem router first) and can confirm this $9 part I purchased from Amazon resolved the poor downstream status. And to think Xfinity wanted to charge me $100.

Here are the results:

Startup Procedure

Procedure Status Comment Acquire Downstream Channel 507 MHz Locked Connectivity State OK Operational Boot State OK Operational Security Enabled BPI+

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked 256 QAM 5 507000000 Hz 6.1 dBmV 41.1 dB 0 0 2 Locked 256 QAM 2 489000000 Hz 6.2 dBmV 41.1 dB 0 0 3 Locked 256 QAM 3 495000000 Hz 6.0 dBmV 41.1 dB 0 0 4 Locked 256 QAM 4 501000000 Hz 6.0 dBmV 41.1 dB 0 0 5 Locked 256 QAM 6 513000000 Hz 6.0 dBmV 41.2 dB 0 0 6 Locked 256 QAM 7 519000000 Hz 6.1 dBmV 41.4 dB 0 0 7 Locked 256 QAM 8 525000000 Hz 6.1 dBmV 41.4 dB 0 0 8 Locked 256 QAM 9 531000000 Hz 6.1 dBmV 41.5 dB 0 0 9 Locked 256 QAM 10 537000000 Hz 6.0 dBmV 41.5 dB 0 0 10 Locked 256 QAM 11 543000000 Hz 5.7 dBmV 41.5 dB 0 0 11 Locked 256 QAM 12 549000000 Hz 5.7 dBmV 41.5 dB 0 0 12 Locked 256 QAM 13 555000000 Hz 5.6 dBmV 41.5 dB 0 0 13 Locked 256 QAM 14 561000000 Hz 5.6 dBmV 41.5 dB 0 0 14 Locked 256 QAM 15 567000000 Hz 5.7 dBmV 41.9 dB 0 0 15 Locked 256 QAM 16 573000000 Hz 5.5 dBmV 41.8 dB 0 0 16 Locked 256 QAM 17 579000000 Hz 5.6 dBmV 41.9 dB 0 0 17 Locked 256 QAM 18 585000000 Hz 5.7 dBmV 41.8 dB 0 0 18 Locked 256 QAM 19 591000000 Hz 5.7 dBmV 41.9 dB 0 0 19 Locked 256 QAM 20 597000000 Hz 5.8 dBmV 42.0 dB 0 0 20 Locked 256 QAM 21 603000000 Hz 5.9 dBmV 42.1 dB 0 0 21 Locked 256 QAM 22 609000000 Hz 5.9 dBmV 42.2 dB 0 0 22 Locked 256 QAM 23 615000000 Hz 5.8 dBmV 42.2 dB 0 0 23 Locked 256 QAM 24 621000000 Hz 5.9 dBmV 42.2 dB 0 0 24 Locked 256 QAM 26 627000000 Hz 6.0 dBmV 42.2 dB 0 0 25 Locked 256 QAM 27 633000000 Hz 6.1 dBmV 42.3 dB 0 0 26 Locked 256 QAM 28 639000000 Hz 6.2 dBmV 42.3 dB 0 0 27 Locked 256 QAM 29 645000000 Hz 6.3 dBmV 42.4 dB 0 0 28 Locked 256 QAM 30 651000000 Hz 6.4 dBmV 42.4 dB 0 0 29 Locked 256 QAM 31 657000000 Hz 6.6 dBmV 42.4 dB 0 0 30 Locked 256 QAM 32 663000000 Hz 6.7 dBmV 42.5 dB 0 0 31 Locked 256 QAM 33 669000000 Hz 6.7 dBmV 42.5 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 6 5120 Ksym/sec 29200000 Hz 36.5 dBmV 2 Locked ATDMA 5 5120 Ksym/sec 35600000 Hz 36.8 dBmV 3 Locked ATDMA 7 5120 Ksym/sec 22800000 Hz 36.5 dBmV 4 Locked ATDMA 8 5120 Ksym/sec 16400000 Hz 35.8 dBmV 5 Locked ATDMA 10 1280 Ksym/sec 39600000 Hz 42.8 dBmV 6 Not Locked Unknown 0 0 0 0.0 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 Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked 0 ,1 ,2 ,3 37 690000000 Hz 7.48 dBmV 41.7 dB 1108 ~ 2987 3528589 2618028 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

[plemans]

Much more in line with what I'd expect or where it should be. 

Hope it stays stable!