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SBG6782 (v8.4.x): Cable Signal Levels

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Question
What are the acceptable RF Signal levels for the SBG6782 Gateway?

 

Answer
Cable signal levels for all DOCSIS cable modems require to be within the acceptable level for the modem operate properly.  The three signal levels that need to be within the acceptable level are Downstream Power, SNR (Signal to Noise Ratio), and Upstream Power.  Downstream Power refers to the line signal sent from the cable provider to cable modem.  Downstream SNR (Signal to Noise Ratio) refers to the signal being sent in relation to the noise on the line.  Upstream Power refers to the line signal from the cable modem to transmit data back to the cable provider.  This document describes how to check the three signal levels to be within the acceptable level for the modem operate properly. 
 

To Verify Signal Levels

  1. Launch a Firefox or Safari browser.  Enter http://192.168.0.1 into the address box, and press the Enter key.  

    NOTE: A browser message on Chrome, Edge, Firefox, and Opera, may appear when accessing the Web Manager.  The message includes 192.168.01 uses an unsupported protocol and ERR_SSL_VERSION_OR_CIPHER_MISMATCH.  The Web Manager uses an earlier version of the TLS protocol and does not match the version allowed by the web browser.  Safari browsers on Apple PC and mobile devices are not impacted.  The workaround to access the Web Manager with a PC is to use the Firefox browser and set the TLS version to 1.  For workaround instructions refer to article # 19435 - 192.168.0.1 uses an unsupported protocol.
     
  2. 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 bypass the alert screen, refer to article # 18181 - Alert Message for Web Manager Access.
     
  3. On the Login page, enter admin or a customized username in the Username field.
     
  4. Enter motorola or a customized password in the Password field.

    NOTE 1: On later versions of the SBG6782-AC, the Wi-Fi Security Key is used as the default admin password printed on the bottom white label.  For assistance with Web Manager Access, refer to article # 18755 – SBG6782-AC: Web Manager Access.


    User-added image

    NOTE 2:  If the unit has been leased or purchased by Shaw Communications, retrieve the username and password from the black label on the unit, and enter that information into the Username and Password fields.

    NOTE 3:  If the unit has been leased or purchased by Time Warner Cable, and the admin username and motorola password does not allow access to the GUI, please contact Time Warner Cable for assistance.

     
  5. Click the Login button. The Home page will appear.

    Image

     
  6. Move the mouse cursor over Status on the top menu, and click the Connection link from the drop-down submenu.  The Status - Connection page will appear.
     
  7. 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

     
  8. In the Downstream Bonded Channels section, identify the Modulation and Power to find verify SNR levels are within the acceptable range for each downstream channel. 

    Acceptable SNR Levels (dB): 
    If QAM64, SNR 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.

    Right click on the image to save it to your computer.

     
  9. In the Upstream Bonded Channels section, identify the number of Channels, Type, and Symbolic Rate to find verify Upstream Power levels are within the acceptable range for each upstream channel. 

    Acceptable Upstream Power Levels (dBmV):

    Right click on the image to save it to your computer.

     
    Upstream Transmit Power Level
    ChannelUS Channel TypeSymbol RateAcceptable Upstream Power Levels
    Single
     
     
    TDMA1280 Ksym/sec45 dBmV to 61 dBmV 
    ATDMA2560 Ksym/sec45 dBmV to 58 dBmV
    5120 Ksym/sec45 dBmV to 57 dBmV
    TwoTDMA1280 Ksym/sec45 dBmV to 58 dBmV
    ATDMA2560 Ksym/sec45 dBmV to 55 dBmV
    5120 Ksym/sec45 dBmV to 54 dBmV
    Three or moreTDMA1280 Ksym/sec45 dBmV to 55 dBmV 
    ATDMA2560 Ksym/sec45 dBmV to 52 dBmV
    5120 Ksym/sec45 dBmV to 51 dBmV
  10. Refresh the page at least twice to identify variations in SNR, Downstream Power, and Upstream Power.   

    NOTE: If either of the signal levels is outside of the acceptable range, power cycle or factory reset the modem. 

     
  11. 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 BmV30 dB or greater
-6 dBmV to -15 dBmV33 dB or greater
Upstream Transmit Power Level
ChannelUS Channel TypeSymbol RateAcceptable Upstream Power Levels
Single (1)TDMA1280 Ksym/sec45 dBmV to 61 dBmV 
ATDMA2560 Ksym/sec45 dBmV to 58 dBmV 
5120 Ksym/sec45 dBmV to  57 dBmV  
Two (2)TDMA1280 Ksym/sec45 dBmV to 58 dBmV  
ATDMA2560 Ksym/sec45 dBmV to 55 dBmV  
5120 Ksym/sec45 dBmV to 54 dBmV  
Three or more (>=3)TDMA1280 Ksym/sec45 dBmV to 55 dBmV 
ATDMA2560 Ksym/sec45 dBmV to 52 dBmV  
5120 Ksym/sec45 dBmV to 51 dBmV  

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