You can connect a DVD recorder's Line Input (typ. L1, L2 or L3) to one of the Comcast outputs and make a DVD copy much like a VHS tape...press play on Comcast and Rec on DVDR.
There are other features of DVDRs that make them slightly more complex than a VHS rec. if you choose to use those features. There also may be one or more settings on the Comcast box you need to make to get an output signal to the DVDR...some boxes have an "Out to VCR" or similar connection.
Some DVDRs have a Hard Disk Drive (HDD)...Philips DVDR3575H for one, $298 at Wal-Mart and other places...that makes time-shift recording of programs, transferring from STBs, and copying to DVDs much easier than a DVDR with just a DVD drive. High-quality DVDs cost ~30 cents each.
No degrees needed!