Cable signal levels for all DOCSIS cable modems require to be within the acceptable level for the modem operate properly. Â The three signal levels that need to be within the acceptable level are Downstream Power, SNR (Signal to Noise Ratio), and Upstream Power. Â Downstream Power refers to the line signal sent from the cable provider to cable modem. Â Downstream SNR (Signal to Noise Ratio) refers to the signal being sent in relation to the noise on the line. Â Upstream Power refers to the line signal from the cable modem to transmit data back to the cable provider. Â This document describes how to check the three signal levels to be within the acceptable level for the modem operate properly.Â
Checking Cable Signal Levels
- 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 Status page will appear.
 - In the Downstream section, verify Power levels are within the acceptable range of - 15 dBmV to + 15 dBmV for each downstream channel.Â
 - In the Downstream section, identify the Modulation and Power to verify SNR levels are within the acceptable range for each downstream channel.Â
Acceptable SNR Levels (dB):Â
If QAM64, SNR should be 23.5 dB or greater.Â
If QAM256 and DPL( -6 dBmV to +15 dBmV) SNR should be 30 dB or greater.Â
If QAM256 and DPL(-15 dBmV to -6 dBmV) SNR should be 33 dB or greater.  Â
 - In the Upstream section, identify the number of Upstream Channels, Channel Type, and Symbolic Rate to verify thePower levels are within the acceptable range for each upstream channel.Â
Acceptable Upstream Power Levels (dBmV):
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Upstream Transmit Power Level |
Channel | US Channel Type | Symbol Rate | Acceptable US Power Level |
Single   | TDMA | 1280 Ksym/sec | +61 dBmV to 45 dBmV |
ATDMA | 2560 Ksym/sec | +58 dBmV to 45 dBmV |
5120 Ksym/sec | +57 dBmV to 45 dBmV |
Two | TDMA | 1280 Ksym/sec | +58 dBmV to 45 dBmV |
ATDMA | 2560 Ksym/sec | +55 dBmV to 45 dBmV |
5120 Ksym/sec | +54 dBmV to 45 dBmV |
Three or more | TDMA | 1280 Ksym/sec | +55 dBmV to 45 dBmV |
ATDMA | 2560 Ksym/sec | +52 dBmV to 45 dBmV |
5120 Ksym/sec | +51 dBmV to 45 dBmV |
- Refresh the page at least twice to identify variations in SNR, Downstream Power, and Upstream Power.  Â
NOTE: If the either of the signal levels are outside of the acceptable range, power cycle or factory reset the modem. Factory resetting the modem will eliminate any customized settings.
 - Contact the cable provider to adjust the signal level to the acceptable level range.
Acceptable Signal Levels
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Recommended Max Downstream Power Level (DPL) | Recommended Min Downstream Power Level (DPL) |
+15 dBmV | -15 dBmV |
Downstream Signal to Noise Ratio (SNR) |
Modulation | Downstream Power Level | Acceptable DS SNR |
64 QAM | n/a | 23.5 dB or greater |
256 QAM Â | -6 dBmV to +15 BmV | 30 dB or greater |
-6 dBmV to -15 dBmV | 33 dB or greater |
Upstream Transmit Power Level |
Channel | US Channel Type | Symbol Rate | Recommended Max USÂ Power Level | Recommended Min US Power Level |
Single | TDMA | 1280 Ksym/sec | +61 dBmVÂ | 45 dBmV |
ATDMA | 2560 Ksym/sec | +58 dBmVÂ | 45 dBmV |
5120 Ksym/sec | +57 dBmVÂ | 45 dBmV |
Two | TDMA | 1280 Ksym/sec | +58 dBmVÂ | 45 dBmV |
ATDMA | 2560 Ksym/sec | +55 dBmVÂ | 45 dBmV |
5120 Ksym/sec | +54 dBmVÂ | 45 dBmV |
Three or more | TDMA | 1280 Ksym/sec | +55 dBmVÂ | 45 dBmV |
ATDMA | 2560 Ksym/sec | +52 dBmVÂ | 45 dBmV |
5120 Ksym/sec | +51 dBmVÂ | 45 dBmV |