The right to emit a radio wave of a given frequency is conceptual. What's owned here is not a specific wave or a specific photon, but the right to create one from scratch, and only if it has a certain property.
What is owned is the right to emit radio waves of a given frequency in a given geographic region. This right is, in some ways, similar to the right to emit noises or even pollution, though the radio wave emission is the main, rather than a side-effect.
The reason it makes sense as a property right is the interference of two broadcasters working within the same area and using the same frequency. Because (and to the degree that) interference is restricted to a narrow frequency band and limited geographic area, so are property rights.
This, in fact, is an excellent illustration of how the scope of property rights is tailored narrowly to the minimum required to avoid physical interference by newcomers with an ongoing project - in this case, broadcasting on a given frequency.
If you extend this to visible spectrum: it's like the difference between a green object or a green light beam, and the concept of the color green itself. It's like owning an exclusive right to painting things green, or shining a green light.
That would be a relevant comparison if your project involving painting things green is physically interfered with by others doing the same. This is obviously not the case here, but is the case with radio transmissions.
Or similarly, it's like the difference between owning a book containing a novel, and owning the novel itself, or the right to publish a book containing that novel.
Owning frequencies (in a limited geographical area) is exactly analogous to owning a physical book, not the copyright to one. Owning a book means that others may not make unauthorised use of the specific copy you own, because such use interferes with your enjoyment of that specific copy. Similarly, owning frequencies means that others may not broadcast on that frequency and within the limited geographic area precisely because (and to the extent) that such competing broadcasts physically interfere with your ability to broadcast your signals to others in that area.
By contrast, violating copyrights in no way interferes with your enjoyment of your physical property, nor in your ability to communicate with others.
Violating your copyrights may cause you financial loss, but the prevention of financial loss is far too broad a criterion for preventing others from acting.
Government is not the solution. Government is the problem.