I have been evaluating your responces to our suggestions , so now I will present one more option. Thats 2 separate antenna systems , one system aimed at 247 and a second system aimed at 210. . Thats double of every thing , the antennas the preamps the splitters the coax wiring and etc.. . The 2 separate systems are Not Connected Together. At each Tv location is a Remote Control A/B antenna system switch , With a hand held Remote Control you switch from one antenna to the other antenna. . Yes this is a 'chunk of change' . If the one antenna system is not quite do in it. Then you can add the second system later. Here are remote control A/B antenna switches ,
http://www.antennasdirect.com/store/..._B_switch.html ,
http://www.radioshack.com , enter 2049643 in the radioshack search box