UPDATE, 12:40 PM: NAB chief Gordon Smith warns that the FCC may be disappointed by the number of TV stations that will volunteer to give up their spectrum. “If there’s a stampede coming, we don’t hear any hooves,” he says. And the FCC probably won’t be interested in the rural stations that are most likely to be interested in a payout from an auction. The need for spectrum for wireless broadband “is an urban concern, not a rural concern. Oregon, where I’m from, will never run out of spectrum.” The NAB will cooperate with the FCC as it enters what Smith says is “uncharted territory.” But the trade group will try to ensure that stations aren’t coerced to participate in the auction. “That remains the focus of our concern.” Since the FCC action follows congressional legislation, the process likely will proceed no mater who wins the presidential election in November.

PREVIOUS, 11:30 AM: The plan has been a long time coming, and FCC Chairman Julius Genachowski says it’s “a big deal” — although it could result in a bruising fight with broadcasters. The commission today unanimously endorsed a notice of proposed rulemaking that would enable broadcasters to voluntarily give up some of the airwave spectrum that they currently use, and share in the proceeds when it’s auctioned to wireless broadband providers. Genachowski has said that the country urgently needs more spectrum to feed the burgeoning number of smartphones, tablets and other mobile devices. And the auction plan provides “a once in a lifetime financial opportunity” for stations that have more spectrum than they need, he says. The auction could be especially appealing to small and independent stations, analysts say. Internet activists are delighted by the initiative. “While broadcasting remains important for some communities, some broadcast signals are primarily watched only as re-carried by pay TV systems,” says Public Knowledge Senior Staff Attorney John Bergmayer. Still, the National Association of Broadcasters has been wary. It has warned that Genachowski and others are overstating the need for broadcasters to give up spectrum — and questioned whether the process would be purely voluntary. (The NAB will hold a press conference this afternoon where it will respond to the FCC vote.)

The plan voted on today would have three stages: Broadcasters willing to give up some spectrum would engage in a so-called “reverse auction.” The FCC would decide whether it wants the spectrum being offered and, if it does, how much it would be willing to pay the station. Once the government knows how much spectrum can be freed, it would have to repack signals, reassigning frequencies so the airwaves could be used most efficiently. Then the FCC could conduct what it calls a “forward auction” where spectrum would go to the highest bidders — most likely wireless broadband providers.