The fact that my sytem has worked for years with the splitter and now does not, and the fact that the uplink power is 54 dB w/o the splitter tells me that the modem is hitting the max output limit with the splitter installed. I suspect that the cable loss in the house or on Comcast's side has increased. I will test the signal strength at the outside block and go from there. Thanks for you input.
Comcast fixed the problem. The tech bypassed the main multi-way splitter outside. The splitter has a 10 db loss. The added a 2-way splitter and fed the output to the modem and the main splitter. The uplink signal now reads 52 dB and is workin fine with my original internal setup.
