A lot depends on how your rig is wired. If you have a cable input jack in the electrical compartment that goes to a switchbox then you can use that cable for your DTV antenna if it's RG6 cable. Disconnect the cable from the switchbox and run it to the DTV receiver or the DTV SWM power supply box. You'll still have the problem of getting the HDMI signal from the DTV box to the TV.
In my Georgetown, the "cable input" cable from the rear compartment goes to the common side of an A/B switch One side of the switch goes to the FR supplied switchbox (antenna, cable, aux), the other to the SWM power brick. When I'm hooked up to a park's cable system, the signal from the cable is fed to the switchbox then to the TVs in the unit. When I'm using the satellite receiver, the A/B switch connects the cable to the SWM power supply which then connects to the receiver.
The HDMI signal from the DTV receiver is fed to an ActionTec HDMI over wifi transmitter which feeds two receivers, one for each TV. I am limited to watching the same program on both TVs at the same time but since they're only 15' apart, there'd be audio interference between them if they were playing different programs.