Answer | 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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Checking Cable Signal Levels
NOTE: If the SB6141 is connected to a router, it is recommended to disconnect the router and connect the SB6141 directly to a computer with an Ethernet cable.
- Launch a web browser, such as Internet Explorer, Firefox, or Safari. Enter http://192.168.100.1 into the address box. The Cable Modem Status page will appear.
 - Click the Signal link on the top menu . The Signal 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 find 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 Symbolic Rate to find verify Upstream Power levels are within the acceptable range.Â
Acceptable Upstream Power Levels (dBmV)
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| Upstream Transmit Power Level | | Channel | US Channel Type | Symbol Rate | Acceptable Upstream Power Levels | | Single | TDMA | 1280 Ksym/sec | 45 dBmv to 61 dBmV | | ATDMA | 2560 Ksym/sec | 45 dBmv to 58 dBmV | | 5120 Ksym/sec | 45 dBmv to 57 dBmV | | Â Two | TDMA | 1280 Ksym/sec | 45 dBmv to 58 dBmV | | ATDMA | 2560 Ksym/sec | 45 dBmv to 55 dBmV | | 5120 Ksym/sec | 45 dBmv to 54 dBmV | | Three or more | TDMA | 1280 Ksym/sec | 45 dBmv to 55 dBmV | | ATDMA | Â 2560 Ksym/sec | 45 dBmv to 52 dBmV | | Â 5120 Ksym/sec | 45 dBmv to 51 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.Â
 - Contact the cable provider to adjust the signal level to the acceptable level range.
Acceptable Signal Levels
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| Acceptable Downstream Power Level | | -15 dBmV to +15 dBmV | | Downstream Signal to Noise Ratio (SNR) | | Modulation | Downstream Power | Acceptable Downstream SNR | | 64 QAM | n/a | 23.5 dB or greater | 256 QAM
 | -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 | Acceptable Upstream Power Levels | | Single (1) | TDMA | 1280 Ksym/sec | 45 dBmv to 61 dBmV | | ATDMA | 2560 Ksym/sec | 45 dBmv to 58 dBmV | | 5120 Ksym/sec | 45 dBmv to 57 dBmV | |  Two (2) | TDMA | 1280 Ksym/sec | 45 dBmv to 58 dBmV | | ATDMA | 2560 Ksym/sec | 45 dBmv to 55 dBmV | | 5120 Ksym/sec | 45 dBmv to 54 dBmV | | Three or more (>=3) | TDMA | 1280 Ksym/sec | 45 dBmv to 55 dBmV | | ATDMA |  2560 Ksym/sec | 45 dBmv to 52 dBmV | |  5120 Ksym/sec | 45 dBmv to 51 dBmV |
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