The FCC says the most controversial aspect of Reflect Orbital's Earendil-1 satellite, its giant mirror, falls outside its authority since the regulator mainly focuses on radio spectrum.
From a physics perspective there isn’t a reason you can’t utilize other parts of the em spectrum for radio communication. Radio can be amplitude (AM) or frequency (FM) modulated, or now even digital. The same techniques can be applied to other bands. The different groups, radio, microwave, come from human categorization, as well as different engineering approaches related to technical limitations.
From a physics perspective there isn’t a reason you can’t utilize other parts of the em spectrum for radio communication. Radio can be amplitude (AM) or frequency (FM) modulated, or now even digital. The same techniques can be applied to other bands. The different groups, radio, microwave, come from human categorization, as well as different engineering approaches related to technical limitations.