said by Jim721:You did not post the model number but likely it's a docsis 2 emta
If there are 2 (or 3) upstream channels as he/she mentioned, then I don't think it will be a DOCSIS 2.0. As far as I know, only DOCSIS 3.0 allows for multiple channels.
As to the original question, if there are signal problems, then it would be likely best to call Comcast & get them involved. You could try tightening all of the coax connections between the modem and the wall/the rest of the connections that you are aware of. As well, remove any unnecessary splitters that you are aware of.