Part 74 of the FCC Rules have provision for 50 mW FM transmitters such as this Comtek unit:
Such transmitters are authorized for broadcast production locations, film/video on-location, and live entertainment applications. Of the 119 possible frequencies spanning TV channels 5 & 6 this can be set for 87.7 MHz for use with FM receivers.
Atrain radio might qualify because he has a TV version of his radio show on Sstream, Bob Felmly no doubt qualifies because he does regular live broadcast productions for LPFM station WCFI, KDX would qualify because we have KDX-TV and the video production facility which was my profession from 1990 to 2000, and by generating feeds to a TV webcam everything would be set.
Contact Comtek and discuss your plans, they will guide you along.
If there is a TV station using a channel you can't use it.
