Please to be enjoying this comprensive white paper from Dr. Jack Gittings, foremost broadcast electronics expert, PhD from Standford, former chief hardware engineer at Cisco and professor at Stanford, who tells us that:
The objective of limited area broadcasting is different from conventional commercial broadcast applications.
Instead of trying to cover the maximum area possible, limited areas are chosen and a broadcast signal is focused on them.
In the United States the FCC has defined limited area broadcast methods and limits under Part 15 of its Rules, which do not require either a license or notification for operation.
Enjoy the remaining 2000 or so words here: White Paper on Limited Area Broadcasting
Is limited area broadcasting in your future?