said by telcodad:While I'll agree that "very high" might have been a little too much, if some people are saying that they have had issues when their upstream levels hit 50 dBmV, then it is more than just "marginal." You also have to allow for a few dB of "headroom," given the normal, daily fluctuations most HFC systems experience.
I have stress tested my current SB6121 by moving it from its normal -3.5 db splitter leg to a -7 db splitter leg. When on the -3.5 db leg, my upstream levels read ~-45-48 dBmV. When on the -7 db leg, my upstream levels read ~-49-52 dBmV. I have left it on the -7 db leg (with at least one upstream channel at the -52 dBmV level) for multiple days, and my connection remained solid.
I have also tested my old (backup) D-Link DCM202 modem in a similar fashion, and its upstream level readings consistently read ~ 3 dBmV lower on either splitter leg than my SB6121. So, if my old D-Link had started failing at the -50 dBmV reading, would it really have failed at -50 dBmV, or would it have failed at -53 dBmV, or perhaps both of my cable modems are so far off in their readings that it would have actually failed at -55 dBmV ?
Cable modems are not expensive cable line testers, and their line level readings are not to be taken seriously. At best, the day to day readings on the same cable modem on the same connection, are good as a relative measure of conditions on a day to day basis for that specific modem on that specific connection. Those readings bear no real or reliable relationship to actual values measured with a high quality tester.
