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SBG6580: Cable Signal Levels

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Question

What are the acceptable RF Signal levels for the SBG6580 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 web browser, such as Internet Explorer, Firefox, or Safari. Enter http://192.168.0.1 into the address box.

    NOTE: By default the LAN IP address is 192.168.0.1. If the default address has been changed, enter the custom address in the address box.
     
  2. Enter admin in the Username field.
  3. Enter motorola in the Password field.
  4. Click the Login button. The Status page appears.

    Right click on the image to save it to your computer.
     
  5. In the Downstream Bonded Channels section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel. 
  6. 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 QAM64SNR should be 23.5 dBmV or greater. 
    If QAM256 and DPL( -6 dBmV to +15 dBmV) SNR should be 30 dBmV or greater. 
    If QAM256 and DPL(-15 dBmV to -6 dBmV) SNR should be 33 dBmV or greater.   
     
  7. In the Upstream Bonded Channels section, identify the number of ChannelsTypeSymbolic Rate to find verify Upstream Power levels are within the acceptable range for each upstream channel. 

    Acceptable Upstream Power Levels (dBmV):
     
    Upstream Transmit Power Level
    ChannelUS Channel TypeSymbol RateAcceptable US Power Level
     
    Single
    TDMA1280 Ksym/sec+61 dBmV to 45 dBmV
    ATDMA2560 Ksym/sec+58 dBmV to 45 dBmV
    5120 Ksym/sec+57 dBmV to 45 dBmV
     
     
    Two
    TDMA1280 Ksym/sec+58 dBmV to 45 dBmV
    ATDMA2560 Ksym/sec+55 dBmV to 45 dBmV
    5120 Ksym/sec+54 dBmV to 45 dBmV
     



    Three or more
    TDMA1280 Ksym/sec+55 dBmV to 45 dBmV
     
     
     
    ATDMA
     2560 Ksym/sec+52 dBmV to 45 dBmV
     5120 Ksym/sec+51 dBmV to 45 dBmV
  8. Refresh the page at least twice to identify variations in SNRDownstream Power, and Upstream Power.   

    NOTE: If the either of the signal levels are outside of the acceptable range, power cycle or factory reset the modem. 
     
  9. Contact the cable provider to adjust the signal level to the acceptable level range.
Acceptable Signal Levels
 
Downstream Power Level (DPL)
+15 to -15dBmV
Downstream Signal to Noise Ratio (SNR):
ModulationDownstream Power LevelAcceptable DS 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 US Power Level
 
Single
TDMA1280 Ksym/sec+61 dBmV to 45 dBmV
ATDMA2560 Ksym/sec+58 dBmV to 45 dBmV
5120 Ksym/sec+57 dBmV to 45 dBmV
 
 
Two
TDMA1280 Ksym/sec+58 dBmV to 45 dBmV
ATDMA2560 Ksym/sec+55 dBmV to 45 dBmV
5120 Ksym/sec+54 dBmV to 45 dBmV
 



Three or more
TDMA1280 Ksym/sec+55 dBmV to 45 dBmV
 
 
 
ATDMA
 2560 Ksym/sec+52 dBmV to 45 dBmV
 5120 Ksym/sec+51 dBmV to 45 dBmV

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