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
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To Verify Cable Signal Levels
- 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.
 - Click the Signal link on the left-hand menu. The Signal page appears.
These levels apply to all Motorola 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)
| Downstream Power Level (DPL): | +15 to -15dBmV |
| Downstream Signal to Noise Ratio (SNR): | 23.5 dB or greater (if 64 QAM) |
| 30 dB or greater (if 256 QAM and DPL = -5 to +15 dB) |
| 33 dB or greater (if 256 QAM and DPL = -6 to -15 dB) |
| Upstream Transmit Power Level: | 57dBmV or less (1 downstream channel) |
| 54dBmV or less (2 downstream channels) |
| 51dBmV or less (3 or more downstream channels) |
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