I have RCN cable modem service in Washington DC. For many years I have been happy using a Motorola Surfboard SB5100 modem. It works flawlessly. Recently I was persuaded to upgrade to a DOCSIS 3.0 modem so I bought the Motorola SB6141. RCN could not get it to connect and declared it defective. On a hunch I called Motorola/Arris tech support who had me log into the modem's web page and check its signal. The tech said the upstream power level was too erratic, varying from one browser refresh to another from 20dBmv to 58dBmv. He said DOCSIS 3.0 was much pickier about power stability and would never connect with that much volatility. He said I would have to call someone into the house to inspect all my cabling. So now I am back to my SB5100 and it works perfectly. BTW, the upstream power level for the SB5100 never varies from 44dBmv no matter how many refreshes.Is the SB6141 defective or is the Motorola tech correct? Should I give up on the upgrade or call RCN in to check my house's cabling? Should I try another sample of the SB6141 or another brand of DOCSIS 3.0 modem?Thank for you advice!