We can detect microwaves, infrared rays, light rays, ultraviolet rays, X-rays, and gamma rays. We might not be able to transmit and receive FM radio in those frequencies, but we are able to detect the presence, polarization, and direction of such radiation.
But if you can't modulate or demodulate gamma rays (which is anything above a certain frequency), you can't even see if they are transmitting information or not. Even radio waves modulated with spread spectrum techniques look like noise. Who knows what we'll be using in the future.
