Who sets the limitations on radio power, antenna height, and frequency use?

The correct answer is the Federal Communications Commission (FCC), which is the governing body responsible for regulating interstate and international communications by radio, television, wire, satellite, and cable across the United States. The FCC sets specific guidelines and limitations on radio power, antenna height, and frequency use to ensure efficient operation and to prevent interference between different communication systems. This regulation is essential for maintaining safety and ensuring that all users of the electromagnetic spectrum can operate without disrupting one another.

The importance of the FCC's role lies in its ability to manage a limited resource—the radio spectrum—and to facilitate public safety communications by enforcing rules that ensure all communication systems can coexist. The other organizations listed have their own specific areas of focus but do not regulate these aspects of communications. For instance, the Federal Bureau of Investigation primarily handles criminal investigations and security matters, while the Department of Transportation focuses on transport systems and policies. The National Security Agency is involved in intelligence and national security matters, rather than the regulation of communication frequencies.