Unused broadcast spectrum could be worth up to US$50 billion, FCC Chairman Julius Genachowski said during a recent briefing. About 300MHz of spectrum is set aside for broadcast TV, but in TV markets with fewer than 1 million people, about 36MHz are typically used for broadcasting, and even in the largest TV markets, only about half of the broadcast spectrum is used, he said.

The National Association of Broadcasters (NAB), representing U.S. TV stations, pledged to work with the FCC on the broadband plan, but a spokesman said the plan raises concerns.

"We were pleased by initial indications from FCC members that any spectrum reallocation would be voluntary, and were therefore prepared to move forward in a constructive fashion on that basis," said Dennis Wharton, NAB's executive vice president. "However, we are concerned by reports today that suggest many aspects of the plan may in fact not be as voluntary as originally promised. Moreover, as the nation's only communications service that is free, local and ubiquitous, we would oppose any attempt to impose onerous new spectrum fees on broadcasters."

The FCC and Congress should conduct an inventory of all available spectrum before moving ahead, Wharton added. "No reallocation plan should move forward without a complete accounting of how the airwaves are allocated, licensed and used," he said.

Broadcasters returned 108MHz of spectrum as part of the transition from analog to digital TV that freed up the 700MHz spectrum auctioned in early 2008, Wharton noted. Broadcasters gave back more than a quarter of their spectrum for the 700MHz auction, he said.