Matt, Computers (Linux or otherwise) don't have RF modulators. I do not know of a single-channel IP-in analog modulator (I looked at Blonder Tongue, Drake and Pico Digital).
It is possible to cobble together a Linux system running VideoLAN <http://videolan.org> player, and get analog audio and video out of the computer, and pipe that into an analog modulator. Dave Devereaux-Weber University of Wisconsin-Madison
