T25: Cable Signal Levels

• 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.

Checking Signal Levels

NOTE: If the T25 is connected to a router, it is recommended to disconnect the router and connect the T25 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 1: 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.
   
   NOTE 2: On firmware prior to version 11.02, the Status page will appear and the admin Login page is unavailable.
    
2. On the Login page, enter admin in the Username field.
    
3. Enter a customized password in the Password field and then click the Login button.  The Status page will appear.
   
   NOTE: If this is the first-time access to the Web Manager Access, refer to article # 18100 – T25: Web Manager Access. 
   
   
    
4. In the Downstream QAM section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel.
   
   
    
5. In the Downstream QAM section, identify the Modulation and Power to verify SNR levels are within the acceptable range for each downstream channel.  
    

   Downstream Signal To Noise Ratio (SNR)
   Modulation	DS Power Level (dBmV)	Acceptable DS SNR (dB)
   64QAM	-15 to +15	+23.5 or greater
   256QAM	-6 to +15	+30 or greater
   	-15 to -6	+33 or greater

   
   
    
6. In the Upstream QAM section, identify the number of Upstream channels and Symbolic Rate to verify the Power levels are within the acceptable range for each upstream channel. 
   
   
   
   Acceptable Upstream Power Levels (dBmV)
    

   Upstream Transmit Power Level
   Channel	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

7. Refresh the page at least twice to identify variations in 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 modem.  Factory resetting the modem will erase any customized settings.
    
8. 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
   64 QAM	n/a	23.5 dB or greater
   256 QAM	-6 dBmV to +15 BmV	30 dB or greater
   	-6 dBmV to -15 dBmV	33 dB or greater
   Upstream Transmit Power Level
   Channel	Symbol Rate	Acceptable Upstream Power Levels
   Single (1)	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 (2)	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 (>=3)	1280 Ksym/sec	45 dBmv to 55 dBmV
   	2560 Ksym/sec	45 dBmv to 52 dBmV
   	5120 Ksym/sec	45 dBmv to 51 dBmV