Over the many decades the physical bandwidth for OTA TV keeps shrinking.

[HDTV1080P]

Over the many decades the physical bandwidth for over the air broadcast television keeps shrinking as the FCC keeps auctioning off the spectrum. In the future perhaps one day the entire over the air broadcast television spectrum might be completely auctioned off. The new ATSC 3.0 system will increase the virtual bandwidth but not the physical bandwidth. ATSC 3.0 will have better audio quality, Ultra HD resolution support, and HDR. However, consumers and broadcasters keep losing the physical bandwidth for free over the air broadcast television.

Perhaps one day the FCC might decide to auction off some of the FM and AM radio physical bandwidth and use HD Radio to increase the virtual bandwidth.

QUOTE

“The amount of spectrum devoted to TV broadcasters is shrinking—from a peak of 486 MHz before 1983 to 294 MHz today. The incentive auction could easily reduce that to 210 MHz or less. How will broadcasters be able to deliver the same variety of programs and offer new services over the air with less spectrum? I don’t see any option but to make the move to ATSC 3.0, as difficult as that may be.”

http://www.tvtechnology.com/resources/0006/getting-ready-for-atsc-30/276660