Radio Spectrum Inventory Act - Amends the Communications Act of 1934 to require the National Telecommunications and Information Administration (NTIA) and the Federal Communications Commission (FCC) to: (1) biennially inventory each radio spectrum band, at a minimum, from 300 megahertz to 3.5 gigahertz managed by each such agency, including information on the licenses or government user assigned in the band, the total spectrum allocation of each licensee or government user, the number of deployed intentional and end-user intentional radiators, and (if available) other specified information; and (2) make the information available to the public through the Internet. Directs the NTIA and FCC to report to Congress on such inventory.
Allows a licensee or government user to petition the NTIA or the FCC for a partial or total exemption from website inclusion. Allows an exemption to be granted only to the extent that each such agency determines that disclosure of the information would be harmful to U.S. national security. Makes such exemptions applicable for a two-year period, unless there is a request for, and granting of, an extension. Requires information excluded under an exemption to be compiled and reported to Congress on a confidential basis.