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davkim's avatar
davkim
Aspirant
Dec 08, 2021

CAX30 OFDM impairment, Channel disabled by modem

Hi,

 

I bought a new modem CAX30 (modem +wifi combo, AX2700, DOCSIS 3.1) to use for my RCN 1gig plan.

 

however it is only showing 30 mbps...

 

RCN is showing "The modem is operating in Partial mode. This may negatively impact service and could indicate a problem with one or more Upstream or Downstream channels." and "OFDM impairment. Channel disabled by modem."

 

RCN replaced the COAX line from my unit to the hallway box. still no improvement.

RCN is saying that the signal is fine..

 

It looks like Netgear SW is intentionally blocking the signal.

 

Please help me so that i can get my internet speed back so that i can at least WFH...

 

Thank you in advance

 

<tabindex=-1>Downstream Bonded Channels</tabindex=-1>
 
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectablesUncorrectabables
1Locked256 QAM16609000000 Hz6.5 dBmV41.0 dB00
2Locked256 QAM1519000000 Hz6.9 dBmV40.7 dB00
3Locked256 QAM2525000000 Hz6.8 dBmV38.8 dB00
4Locked256 QAM3531000000 Hz6.7 dBmV39.3 dB00
5Locked256 QAM4537000000 Hz6.7 dBmV40.7 dB00
6Locked256 QAM5543000000 Hz6.6 dBmV40.9 dB00
7Locked256 QAM6549000000 Hz6.5 dBmV40.8 dB00
8Locked256 QAM7555000000 Hz6.4 dBmV40.8 dB00
9Locked256 QAM8561000000 Hz6.5 dBmV39.3 dB00
10Locked256 QAM9567000000 Hz6.4 dBmV41.0 dB00
11Locked256 QAM10573000000 Hz6.3 dBmV39.9 dB00
12Locked256 QAM11579000000 Hz6.3 dBmV40.9 dB00
13Locked256 QAM12585000000 Hz6.4 dBmV41.0 dB00
14Locked256 QAM13591000000 Hz6.4 dBmV41.0 dB00
15Locked256 QAM14597000000 Hz6.6 dBmV41.0 dB00
16Locked256 QAM15603000000 Hz6.6 dBmV41.0 dB00
17Locked256 QAM17495000000 Hz7.2 dBmV40.8 dB00
18Locked256 QAM18501000000 Hz7.2 dBmV40.9 dB00
19Locked256 QAM19507000000 Hz7.1 dBmV40.3 dB00
20Locked256 QAM20513000000 Hz7.1 dBmV40.9 dB00
21Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
22Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
23Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
24Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
25Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
26Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
27Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
28Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
29Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
30Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
31Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
32Not LockedUnknown00 Hz0.0 dBmV0.0 dB00
 
<tabindex=-1>Upstream Bonded Channels</tabindex=-1>
 
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA15120 Ksym/sec36800000 Hz40.5 dBmV
2LockedATDMA25120 Ksym/sec30350000 Hz40.3 dBmV
3LockedATDMA35120 Ksym/sec23900000 Hz40.0 dBmV
4Not LockedUnknown00 Ksym/sec0 Hz0 dBmV
5Not LockedUnknown00 Ksym/sec0 Hz0 dBmV
6Not LockedUnknown00 Ksym/sec0 Hz0 dBmV
7Not LockedUnknown00 Ksym/sec0 Hz0 dBmV
8Not LockedUnknown00 Ksym/sec0 Hz0 dBmV
 
<tabindex=-1>Downstream OFDM Channels</tabindex=-1>
 
ChannelChannel IDIndicatorSubcarrier Zero FrequencyActive Subcarrier Number RangeTotal CodewordsUncorrectable Codewords
1159Non-Primary593.6 MHz646 ~ 34492166717980
20Other0 MHz0 ~ 000
 
<tabindex=-1>Upstream OFDMA Channels</tabindex=-1>
 
ChannelUpstreamIsMutedRanging StatusSubcarrier Zero FrequencyActive Subcarrier Number RangeSymbols Per FrameTx Power
1 Other0 MHz0 ~ 000 dBmV
2 Other0 MHz0 ~ 000 dBmV

 

9 Replies

  • FURRYe38's avatar
    FURRYe38
    Guru - Experienced User
    Dec 08, 2021

    What Firmware version is currently loaded?

     

    Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
    Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
    Be sure your using good quality RG6 coax cable up to the modem. 
    Be sure to power OFF the modem for 1 minute then back ON.
    https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853
    https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html

    • davkim's avatar
      davkim
      Aspirant
      Dec 08, 2021

      I power cycle multiple times. checked the firmware updates(

      Firmware VersionV1.4.10.8
       
      Cable Firmware VersionV1.04.09

      ). ISP came to check all the lines, no splitter, no issue with the lines.

       

      I also got a replacement for the same modem thinking that the first modem that i got is malfunctioning. However, it has the same issue.

       

      ax Speed Ability: 1000Mbps / 20MbpsManufacturer:Netgear Wireless Cable GatewayModem Model: CAX30Last Power Cycle: 21 hours, 49:22ⓜ
      Provision Status: ACTIVEProvisioned Speed: 1Gbps / 20Mbps With 1 Dynamic IP's
      Last Connection Status: PARTIALLY OPERATIONAL  as of 2021-12-08 13:37:47Current Date/Time: 2021-12-8 12:38:35
       
      this is the current status on my modem. provision is active but really slow connection.
  • FURRYe38's avatar
    FURRYe38
    Guru - Experienced User
    Dec 08, 2021

    Just curious, do you have the prior ISP modem by chance or where you using a ISP provided modem? 

    • davkim's avatar
      davkim
      Aspirant
      Dec 08, 2021

      When i moved to this place no.

       

      so i was using the first BYOD modem from Arris, it was fine but it droped to 30 mbps.

       

      i got a new one cax30 and it still shows 30 mbps.

       

      they brought their own to test once and it looked fine.

       

      that was the only time that they tried their modem.

      • FURRYe38's avatar
        FURRYe38
        Guru - Experienced User
        Dec 08, 2021

        Look fine but was it online long enough to notice the drop?

         

        Seems like if you experiecned this with an Arris modem and now a NG modem, this would be an ISP issue. 

        You might go back to the ISP and ask them to use there modem unit for say a month or so. See if the problem appears on there device.