Spectrum Coexistence Act This bill requires the Department of Commerce to convene a working group to develop and periodically update technical specifications and other measures to minimize interference from commercial operations in the portions of the electromagnetic spectrum that are allocated for federal use or shared use. This includes developing voluntary standards and other measures for encouraging the design, manufacture, and sale of radio receivers operating in federal systems with features that provide interference immunity (i.e., features that limit interruptions or obstructions of federal operations when spectrum is shared). The working group must include representatives from federal agencies, the telecommunications industry, and academia. Additionally, the National Telecommunications and Information Administration (NTIA) and the Federal Communications Commission must publish the measures developed by the working group on the website of the NTIA and in the Federal Register .