The head of the FCC tried to convince broadcasters to sell off their spectrum in voluntary auctions during a speech yesterday at the National Association of Broadcaster’s annual conference in Las Vegas.

Chairman Julius Genachowski told attendees that selling off their spectrum through the auctions “presents an unprecedented opportunity … to improve their financial position.”

“Don’t be afraid to be interested in incentive auctions,” Genachowski said in a copy of his prepared remarks.

He argued that broadcasters could get a “sizeable cash infusion” for selling off their airwaves and could share a channel or move to VHF if they chose to stay on the air.

As with the wireless industry, spectrum is the lifeblood of broadcasters – without it, they cannot operate. However, some television stations are struggling to remain profitable amid competition from audience-eroding online content. For them, selling off their spectrum assets could provide a viable exit from the business.

The broadcast show was a tough crowd for Genachowski, whose plans to sell off more television spectrum were deeply unpopular with the broadcast industry when they were initially announced.

In his own keynote address, NAB CEO Gordon Smith voiced suspicion about the wireless industry’s long-term objectives for gleaning additional airwaves from television broadcasters. Smith did not encourage NAB members to participate in the auctions, instead warning them of further encroachment by mobile operators.

“Recent press reports quote the telecommunications industry saying the spectrum legislation passed by Congress is only the beginning – a “down payment” of what they’re seeking in terms of access to the airwaves,” he said in his prepared remarks. “They want us out of this game. We can’t let down our guard.”

Broadcasters were wary of selling off additional airwaves so soon on the heels of the transition to digital television and pushed hard to ensure the auctions were completely voluntary.

Even though legislation authorizing the auctions codified their voluntary nature, the television industry has remained reticent to sell off their spectrum, sparking concerns that the incentive auctions won’t free up the amount the FCC was hoping for to address the bandwidth shortage facing wireless operators.

The agency has pledged to open 500 MHz for mobile broadband, with a substantial portion of that coming from broadcasters.