The TV industry can count on more Hill support in its battle to persuade the FCC not to permit the use of unlicensed wireless devices to share the broadcast spectrum.

Four more letters from Senate Democrats and Republicans were sent to FCC Chairman Martin expressing concerns about the agency’s possible approval of such unlicensed devices like wireless laptops and PDAs that would share the so-called white spaces or vacant between broadcast channels.

“The use of these devices now or in the future poses an unacceptable risk of harmful interference that would permanently undermine over-the-air television in the United States,” wrote Georgia Republican Senators Johnny Isakson and Saxby Chambliss.

Martin also heard from Senators Charles Grassley (R-Iowa), Lindsey Graham (R-S.C.) and Mary Landrieu (D-La.).

The senators are worried about potential interference from the unlicensed devices.

“This interference is impossible to police. Consumers will not know the cause or source of the interference disrupting the programming they are watching,” wrote Landrieu.

The lawmakers also emphasized that the device could interrupt the digital transition.

“A smooth digital transition is of the utmost importance to Congress, to the FCC and the American people. Please do not jeopardize the success of that transition by permanently undermining digital television,” said the Isakson-Chambliss letter.

Martin has been getting an earful from Congress on this matter especially from the North Carolina House delegation (11 of its 13 representatives) wrote Martin stating their opposition to the use of these unlicensed devices.