Easier to build than that (and without any FCC worries) would be a device that converts ATSC to NTSC and can re-transmit them via 75ohm cable.
All of my sets are hard-wired to my outdoor antenna. The antenna comes into the basement and then gets split to about 5 different locations. It would be nice to simply add a converter which would constantly be putting out about the 15-or-so ATSC signals we have, plus the worthwhile digital side channels on unused dial space. (Currently, that's just RTN, lol)
I even drew this diagram for an electronically inclined friend at work and told him to build it for me!
