said by harald:
No cable modem is capable of reading SNR.
What they display as SNR is a calculated value based upon the ratio of packets with correctable errors to good packets, using the formulas derived by Claude Shannon in the 1040's. The details of how this is done is proprietary to Broadcom and other chip makers. Inferences about what will cause the SNR to change are pretty shaky...
I have seen references to that as well, but that does not explain why Channel ID 6 in my SB6121 does not have a much higher DS SNR than the other three channels, instead of all of them reading 38dB.
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