Consumers - SVG2482AC: Cable Signal Levels

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SVG2482AC: Cable Signal Levels

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What are the acceptable cable signal levels for the SVG2482AC 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. 

Checking Signal Level​
  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.
  2. On the Login page, enter admin in the Username field.
  3. Enter password in the Password field then click the Login button.  The Gateway > At a Glance page will appear.

    NOTE: A prompt to change the password appears when the SVG2482AC is using the default password.  To change the password click the OK button or click the Cancel button to bypass it.

    User-added image

  4. On the left hand-menu, click the Connection link then click the XFINITY Network link on the sub-menu.  The Gateway > Connection > XFINITY Network page will appear.

    User-added image

  5. 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

  6. In the Downstream 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)
    ModulationPowerAcceptable SNR
    64QAM-15 to 15 dBmV23.5 dB or greater
    256QAM-6 to 15 dBmv30 dB or greater
    -15 to -6 dBmV33 dB or greater
    User-added image
  7. In the Upstream section, identify the Symbolic Rate to verify Upstream Power levels are within the acceptable range.
    Upstream Transmit Power Level
    ChannelUS Channel TypeSymbol RateAcceptable US Power Level
    TDMA1280 Ksym/sec45 to 61 dBmV
    ATDMA2560 Ksym/sec45 to 58 dBmV
    5120 Ksym/sec45 to 57 dBmV
    TDMA1280 Ksym/sec45 to 58 dBmV
    ATDMA2560 Ksym/sec45 to 55 dBmV
    5120 Ksym/sec45 to 54 dBmV

    Three or more
    TDMA1280 Ksym/sec45 to 55 dBmV
     2560 Ksym/sec45 to 52 dBmV
     5120 Ksym/sec45 to 51 dBmV
    User-added image
  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 gateway. 

  9. Contact the cable provider to adjust the signal level to the acceptable level range if the signal levels are outside of the acceptable range.

Acceptable Signal Levels
Recommended Min Downstream PowerRecommended Max Downstream Power
-15 dBmV15 dBmV
Downstream Signal to Noise Ratio (SNR)
ModulationDownstream Power Acceptable Downstream SNR
64QAMn/a23.5 dB or greater
-6 to 15 BmV30 dB or greater
-15 to -6 dBmV33 dB or greater
Upstream Transmit Power Level
ChannelUS Channel TypeSymbol RateRecommended Min Upstream Power Recommended Max Upstream Power
SingleTDMA1280 Ksym/sec45 dBmV 61 dBmV
ATDMA2560 Ksym/sec45 dBmV 58 dBmV
5120 Ksym/sec45 dBmV 57 dBmV
TwoTDMA1280 Ksym/sec45 dBmV 58 dBmV
ATDMA2560 Ksym/sec45 dBmV 55 dBmV
5120 Ksym/sec45 dBmV 54 dBmV
Three or moreTDMA1280 Ksym/sec45 dBmV 55 dBmV
ATDMA2560 Ksym/sec45 dBmV 52 dBmV
5120 Ksym/sec45 dBmV 51 dBmV



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