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S33: Cable Signal Levels

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Question
What are the acceptable cable signal levels for the S33 cable modem?
Answer
Cable signal levels for all DOCSIS cable modems need to be at acceptable levels for the modem to operate properly.  The three signal levels that need to be within the acceptable level are Downstream Power LevelSNR (Signal to Noise Ratio), and Upstream Power Level
  • Downstream Power Level: cable signal sent from the cable provider to cable modem.  
  • Downstream SNR (Signal to Noise Ratio): cable signal being sent in relation to the noise on the line.  
  • Upstream Power Level: cable signal from the cable modem to transmit data back to the cable provider.
This document describes how to check the three signal levels to determine if they are within the acceptable levels for the modem to operate properly. 



Checking Signal Levels

NOTE: If the S33 is connected to a router, it is recommended to disconnect the router and connect the S33 directly to a computer with an Ethernet cable.

  1. Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter http://192.168.100.1 into the address box, and press the Enter key.  The Login page will appear.

    NOTE: A security or private risk alert may appear on the web browser advising users to proceed with caution when accessing the Web Manager. There is no risk in proceeding to the Web Manager.  For instructions to by-pass the alert screen, refer to article # 18181 - Alert Message for Web Manager Access.
     
  2. On the Login page, enter admin in the Username field.

  3. Enter a customized password or the default admin password in the Password field.

    NOTE: If this is the first time login to the Web Manager, the default password could be password or the last 8-digit of the serial number.  It is required to set a unique password to proceed to the Web Manager.  For assistance with Web Manager Access, refer to article # 18552 – S33: Web Manager Access.

     
  4. Click the Apply button.  The Product Registration window will appear.

    User-added image

  5. The Product Registration window includes information about enhanced product support, product warranty registration, and promotional offers from ARRIS.
    • Click the Register button to take a few minutes to register the product.  For assistance with product registration refer to article # 18558 - S33: Product Registration.  When the product is registered the product registration window will not appear during the next login. 
    • Click the Ask me later button to by pass the product registration window.  The product registration window will appear during the next login.
    • Click the Stop asking button to stop the product registration window from appearing the next login.
       
      User-added image
  6. In the Downstream Bonded Channels section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel. 

    User-added image
     
  7. In the Downstream Bonded Channels section, identify the Modulation and Power to verify SNR levels are within the acceptable range for each downstream channel. 

    Acceptable SNR Levels (dB)
    If QAM64SNR should be 23.5 dB or greater. 
    If QAM256 and DPL( -6 dBmV to +15 dBmV) SNR should be 30 dB or greater. 
    If QAM256 and DPL(-15 dBmV to -6 dBmV) SNR should be 33 dB or greater.   


    User-added image
     
  8. In the Upstream Bonded Channels section, identify the number of Channels and Type to verify Upstream Power levels are within the acceptable range for each upstream channel. 

    User-added image

    Acceptable Upstream Power Levels (dBmV)

     
    Upstream Transmit Power Level
    ChannelUS Channel TypeAcceptable Upstream Power Levels
    SingleSC-QAM45 dBmV to 61 dBmV
    TwoSC-QAM45 dBmV to 54 dBmV
    Three or moreSC-QAM45 dBmV to 51 dBmV
  9. Refresh the page at least twice to identify variations in SNR, Downstream Power, and Upstream Power.   

    NOTE: If either of the signal levels are outside of the acceptable range, power cycle or factory reset the modem.  Performing a Factory reset will erase any configuration changes and revert the custom admin password back to the default password (password).  For assistance with the Web Manager, refer to article # 18522 - S33 Web Manager Access.

     
  10. Contact the cable provider to adjust the signal level to the acceptable level range.

Acceptable Signal Levels
 
Acceptable Downstream Power Level
-15 dBmV to +15 dBmV
Downstream Signal to Noise Ratio (SNR)
ModulationDownstream PowerAcceptable Downstream SNR
64 QAMn/a23.5 dB or greater
256 QAM-6 dBmV to +15 dBmV30 dB or greater
-15 dBmV to -6 dBmV33 dB or greater
Upstream Transmit Power Level
ChannelUS Channel TypeAcceptable Upstream Power Levels
Single (1)SC-QAM45 dBmV to 61 dBmV
Two (2)SC-QAM45 dBmV to 54 dBmV
Three or more (>=3)SC-QAM45 dBmV to 51 dBmV

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