Here are my numbers, also off of a DCP3825:
Downstream Channels Power Level: Signal to Noise Ratio:
1: -1.3 dBmV 40.9 dB
2: -1.3 dBmV 40.9 dB
3: -1.5 dBmV 40.6 dB
4: -1.5 dBmV 40.4 dB
5: -1.3 dBmV 40.7 dB
6: -1.5 dBmV 40.5 dB
7: -1.8 dBmV 39.9 dB
8: -1.9 dBmV 39.9 dB
Upstream Channels Power Level:
Channel 1: 37.5 dBmV
Channel 2: 39.7 dBmV
Channel 3: 37.2 dBmV
Channel 4: 0.0 dBmV
Looking at your numbers, -11dBmV seems low. Going back to my university days (its been a while) -3db of anything is down 50%, or down to half power. Converting your -11dBmV to mV shows that you are at 28% of where you should be which in theory is 0 dBmV, or 1mV. Don't know why tech support didn't flag that but obviously at that level, its still acceptable. The problem however is what happens when it drops below that level. I had a similar problem not so long ago. A normally stable DCP3825 started to drop offline for no apparent reason. After a visit from a tech, we ended up with a new cable running from the external distribution box to our house. Problem solved. Out of all the houses on that particular distribution box, there is only one left with the original cable. While the -11dBmV level might still work, my guess would be that the incoming power level is low enough that any further momentary drop in power level within the neighborhood distribution network is enough to kick the modem offline. fwiw....