America’s first HD-only FM stations? That’s what David Wilson had intended to do with a pair of FM CPs near Cape Hatteras, NC. He won the two-licenses in the 2007 FCC auction. 101.5 WHDZ, 99.9 WHDX are licensed as C3s both at 50,00 watts. Wilson asked the FCC for experimental authority to run them with only HD signals, no analog. That's two 500-watt HD signals, from a 55-foot tower near his home.He stated that he intended to study coverage and consumer acceptance of IBOC. Essentially by foregoing the analog signal, the stations would only have listeners with HD radios. He also intended to examine the both horizontal-only and vertical only polarization of HD signals. the FCC said NO. More here.
In the years since then we learned that HD needs to run at 10x the normally licensed power for cover the same area. That's something I think the FCC already suspected from their own field tests. Effectively the legacy of Kevin Martin is a mandatory digital codec that everyone will have to have. But also one that nobody wants and no one is allowed to actually use. In the end the two stations were downgraded to 110 watt Class A stations with most of their coverage over the Atlantic Ocean. WHDZ runs News talk and WHDX runs travelers information, both in analog.