All DOCSIS cable modems require that the cable signals fall within a very specific range to be an acceptable level for the modem to operate properly. These levels apply to all ARRIS cable modems and cable modem/gateways. This document describes how to verify the cable signal levels.
To Verify Cable Signal Levels
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Launch a web browser, such as Internet Explorer, Firefox, or Safari. Enter http://192.168.100.1 into the address box. The Status page appears.
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Verify the Downstream Power, Downstream SNR, and Upstream Power (as shown below).
These levels apply to all ARRIS cable modems and cable modem/gateways. These values are absolutes. If the cable modem is experiencing levels that approach the minimum or maximum acceptable levels, then it is a warning sign that there is a possible cable plant issue. If the cable connection at the modem is OK, then it is advised to contact the cable operator to address the issue.
Acceptable Signal Levels (per channel)
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Downstream Power Level (DPL): |
+15 to -15dBmV |
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Downstream Signal to Noise Ratio (SNR): |
23.5 dB or greater (if 64 QAM) |
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30 dB or greater (if 256 QAM and DPL = -5 to +15 dB) |
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33 dB or greater (if 256 QAM and DPL = -6 to -15 dB) |
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Upstream Transmit Power Level: |
57dBmV or less (1 downstream channel) |
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54dBmV or less (2 downstream channels) |
51dBmV or less (3 or more downstream channels)
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