Edit: the 2 comments below give a pretty good explanation as to why the following comment is not correct. Original comment, as always:
I don’t see why they’d have to have big eyes. We use massive radio telescopes for sensitivity, not for the spectrum range. AM radio is in the order of 100 meter wavelengths, but handheld devices can receive it. Wavelength isn’t really the defining factor as much as being able to handle the frequency of the data over the time required. Wavelength is not how tall the wave is, amplitude is.
Handheld devices can receive it, but to actually “see” with it you need a very large aperture(iris) and a “retina” with many of those antennas that respond to different wavelengths. The overall structure of an eye capable of seeing would be massive, not because the signal is faint or you can’t “fit” the amplitude in the aperture but because that’s what you need for acuity and to actually have meaningful angular resolution. Those long waves have more limited angles to fit in a given eye diameter. For something like AM, we’re talking a very big structure.
θ ≈ λ/D where θ is the angular resolution, λ is the wavelength, and D is the diameter of the aperture
As you can see, increasing the wavelength by orders of magnitude means you need to increase the aperture by orders of magnitude to get the same angular resolution.
Edit: the 2 comments below give a pretty good explanation as to why the following comment is not correct. Original comment, as always:
I don’t see why they’d have to have big eyes. We use massive radio telescopes for sensitivity, not for the spectrum range. AM radio is in the order of 100 meter wavelengths, but handheld devices can receive it. Wavelength isn’t really the defining factor as much as being able to handle the frequency of the data over the time required. Wavelength is not how tall the wave is, amplitude is.
Handheld devices can receive it, but to actually “see” with it you need a very large aperture(iris) and a “retina” with many of those antennas that respond to different wavelengths. The overall structure of an eye capable of seeing would be massive, not because the signal is faint or you can’t “fit” the amplitude in the aperture but because that’s what you need for acuity and to actually have meaningful angular resolution. Those long waves have more limited angles to fit in a given eye diameter. For something like AM, we’re talking a very big structure.
https://en.m.wikipedia.org/wiki/Angular_resolution
θ ≈ λ/D where θ is the angular resolution, λ is the wavelength, and D is the diameter of the aperture
As you can see, increasing the wavelength by orders of magnitude means you need to increase the aperture by orders of magnitude to get the same angular resolution.
I realize now I was thinking of data in the time axis rather than the width/resolution direction