G18/G20: Cable Signal Levels

• Downstream Power Level: cable signal sent from the cable provider to the Wi-Fi 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 Wi-Fi cable modem to transmit data back to the cable provider.

Checking Signal Levels

1. Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter http://192.168.0.1 into the address box, and press the Enter key.  The https:// Redirect page will appear.   
    
2. The SURFboard Web Manager is redirecting to a more secure connection, click the Proceed button to continue.  The Gateway > Login page will appear.
   
   
    
3. 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.
   
   NOTE: The Home Network Wizard will appear if this is the first time accessing the Web Manager.  For assistance with the wizard, refer to article # 19602 - G18/G20: Web Manager First Time Login.
    
4. The Username field has admin populated, enter the custom password in the Password field.
   
   NOTE: If the Login page prompts for email address and password, retrieve the email address and password in the app to sign-in.  For detail instructions in the app, refer to article # 19069 - SURFboard Central: Web Manager Access.
    
5. Click the Login button.  The Gateway > Summary page will appear.
   
   
    
6. On the left hand-menu, click the Connection link then click the WAN link on the sub-menu.  The Gateway > Connection > WAN page will appear.
   
   
    
7. In the Downstream QAM section, verify Power Levels (dBmV) are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel.  Click the > next icon to review and capture all the downstream channels.   
   
   
    
8. In the Downstream QAM section, identify the Modulation and Power Level (dBmV) to verify SNR (dB) levels are within the acceptable range for each downstream channel.  Click the > next icon to review and capture all the downstream channels. 
    

   Downstream Signal To Noise Ratio (SNR)
   Modulation	Downstream Power	Acceptable Downstream SNR
   QAM64	-15 dBmV to +15 dBmV	+23.5 dB or greater
   QAM256	-6 dBmV to +15 dBmV	+30 dB or greater
   	-15 dBmV to -6 dBmV	+33 dB or greater

   
   
    
9. In the Upstream QAM section, identify the number of Index and Symbolic Rate (KSym/sec) to verify the Power Level (dBmV) is within the acceptable range for each upstream channel.
    

   Upstream Transmit Power Level
   Index	Symbol Rate	Acceptable Upstream Power Levels
   Single	1280 Ksym/sec	45 dBmV to 61 dBmV
   	2560 Ksym/sec	45 dBmV to 58 dBmV
   	5120 Ksym/sec	45 dBmV to 57 dBmV
   Two	1280 Ksym/sec	45 dBmV to 58 dBmV
   	2560 Ksym/sec	45 dBmV to 55 dBmV
   	5120 Ksym/sec	45 dBmV to 54 dBmV
   Three or more	1280 Ksym/sec	45 dBmV to 55 dBmV
   	2560 Ksym/sec	45 dBmV to 52 dBmV
   	5120 Ksym/sec	45 dBmV to 51 dBmV

   
    
10. Refresh the page at least twice to identify variations in the SNR, Downstream Power Level, and Upstream Power Level.   
    
    NOTE: If either of the signal levels are outside of the acceptable range, power cycle or factory reset the Wi-Fi cable modem.  Factory resetting the Wi-Fi cable modem will erase any customized settings.
     
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)
    Modulation	Downstream Power	Acceptable Downstream SNR
    QAM64	n/a	+23.5 dB or greater
    QAM256	-6 dBmV to +15 dBmV	+30 dB or greater
    	-15 dBmV to -6 dBmV	+33 dB or greater
    Upstream Transmit Power Level
    Index	Symbol Rate	Acceptable Upstream Power Levels
    Single (1)	1280 Kysm/sec	45 dBmV to 61 dBmV
    	2560 Kysm/sec	45 dBmV to 58 dBmV
    	5120 Kysm/sec	45 dBmV to 57 dBmV
    Two (2)	1280 Kysm/sec	45 dBmV to 58 dBmV
    	2560 Kysm/sec	45 dBmV to 55 dBmV
    	5120 Kysm/sec	45 dBmV to 54 dBmV
    Three or more (>=3)	1280 Kysm/sec	45 dBmV to 55 dBmV
    	2560 Kysm/sec	45 dBmV to 52 dBmV
    	5120Kysm/sec	45 dBmV to 51 dBmV