Any AV gurus here?

Need some modulation help if anyone can provide it…

I have set up a modulation system through my house via coax, running components from one central hub to each tv in the house. However, I can only seem to modulate an analog signal. Does anyone know how to modulate a digital/hd signal? The incoming digital signal is via coax so I assume I can modulate a digital signal to other tv’s using it…