NAB President-CEO David Rehr sent a letter late yesterday to FCC Chairman Kevin Martin asking a series of questions related to the agency's plan to allow unlicensed "white spaces" devices to operate in television spectrum.

Rehr's letter reinforced NAB's support for the concept of geolocation as an alternative to spectrum-sensing, but urged the commission to seek public comment on a 400-page technical report recently released by the FCC's Office of Engineering and Technology.

The technical report, which shows that spectrum-sensing technology is inadequate and threatens the viability of interference-free television, will reportedly serve as the basis for a Nov. 4 FCC vote on whether to allow 'white space' devices to operate in television spectrum.

Rehr's letter addressed several questions concerning the FCC's white spaces plan, including issues related to spectrum-sensing and device power limits.

"Broadcasters again want to emphasize that we do not oppose the use of vacant channels in the television broadcast bands. We support the concept of geolocation in combination with an accurate database as a method of avoiding interference with television broadcasts and wireless microphones," wrote Rehr. "However, spectrum sensing alone, as the data within the OET report actually show, does not provide adequate interference protection."