Consumers - TG862G/CT & TG862R: Cable Signal Levels

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TG862G/CT & TG862R: Cable Signal Levels

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What are the acceptable cable signal levels for the TG862 Gateway?
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 into the address box, and press the Enter key.  The Login page will appear.

    NOTE: By default the LAN IP address is If the default address has been changed, enter the custom address in the address box.

  2. On the Login page, enter admin in the Username field.
  3. Enter password in the Password field.
  4. Click the Login button. The Gateway > At a Glance page will appear.


  5. On the left-hand menu, click Gateway.  A sub-menu will appear.
  6. In the sub-menu, click Connection.  A second sub-menu will appear.
  7. In the second sub-menu, click XFINITY Network.  The Gateway > Connection > Xfinity Network page will appear.
  8. In the Downstream section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel. 

    User-added image

  9. In the Downstream 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 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

  10. In the Upstream section, identify the Symbolic Rate to find verify Upstream Power levels are within the acceptable range. 

    Acceptable Upstream Power Levels (dBmV):

    User-added image

    Upstream Transmit Power Level
    ChannelUS Channel TypeSymbol RateAcceptable US Power Level
    TDMA1280 Ksym/sec+61 dBmV to 45 dBmV
    ATDMA2560 Ksym/sec+58 dBmV to 45 dBmV
    5120 Ksym/sec+57 dBmV to 45 dBmV
    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
     2560 Ksym/sec+52 dBmV to 45 dBmV
     5120 Ksym/sec+51 dBmV to 45 dBmV
  11. 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. 

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

Acceptable Signal Levels
Recommended Max Downstream
Power Level (DPL)
Recommended Min Downstream
Power Level (DPL)
+15 dBmV-15 dBmV
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 RateRecommended Max US Power LevelRecommended Min US Power Level
SingleTDMA1280 Ksym/sec+61 dBmV 45 dBmV
ATDMA2560 Ksym/sec+58 dBmV 45 dBmV
5120 Ksym/sec+57 dBmV 45 dBmV
TwoTDMA1280 Ksym/sec+58 dBmV 45 dBmV
ATDMA2560 Ksym/sec+55 dBmV 45 dBmV
5120 Ksym/sec+54 dBmV 45 dBmV
Three or moreTDMA1280 Ksym/sec+55 dBmV 45 dBmV
ATDMA2560 Ksym/sec+52 dBmV 45 dBmV
5120 Ksym/sec+51 dBmV 45 dBmV



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