When my customers would ask me how to record TV after Cable made changes, I told them to rent the cable company DVR because there was no way to explain it to them. Just telling someone how to connect things usually doesn't work unless the person actually has an understanding of signal distribution and conversion.
In its simplest form, every tuner requires its own box. (set-top-box, DTA, CECB, satellite receiver)
If a device has multiple inputs, each input needs its own box.
While you can combine multiple channels on a single coax cable, you are, in essence, building your own personal cable system, or MATV system and that is fairly hard to design.