Yes, radio waves are attenuated in the atmosphere. This is highly frequency dependent - for practical applications the lower the frequency, the less radio waves are attenuated. In comparison with attenuation from obstacles in non-line-of-sight situations, the atmospheric component is not significant.

For really long range propagation on earth, reflections on atmospheric layers are the dominant factor (as there is no line of sights due to the curvature of the planetary surface).

See https://www.sciencedirect.com/topics/engineering/atmospheric... for some nice graphs.

Does that mean that there is an electromagnetic frequency that, no matter how much power we can feasibly put into it, it simply will not transmit through earth's atmosphere due to its' instantaneous attenuation outside of a vacuum?

Yes, in the terahertz band range for example you have very high attenuation of more than 1000 db/km. It's a spectrum (no pun intended), so depending on where you draw the line on "through earth's atmosphere" in terms of how far you want to transmit, you'll have some frequency where this becomes infeasible or you'll need more directed antennas and/or more transmit power.

Atmosphere does play a part but just freespace losses are going to be massive, probably at least 250dB just for the distance voyager is at. Atmosphere could add another 60-100dB. Voyager's antenna has about 40dB of gain but the DSN network can array multiple antennas to make up for the losses. They have up to 2 70m dishes and several 34m dishes that can point at Voyager, quite a massive antenna gain.

it does, but it is not as significant in normal weather conditions in the frequency ranges we're dealing with here (Likely sub 2.4 Ghz) [1], (General rule of thumb, Atmosphere absorbs everything except visible spectrum and 10 cm - 10 m wavelength), compare this to effect from the inverse square law. :)

Now this might be significant enough in directional waves with a huge constant multiplier (like a 'ideal' laser with no divergence). Someone can probably give insight on it here.

1. https://www.researchgate.net/publication/270512069_Propagati...

I'm curious why you ordered the wavelengths the way you did, you totally potholed my entire comprehension. 10 meters (28mhz) through 10cm (2800mhz) to me reads "left to right".

Oh I just wrote it like that cause that's what I remembered off the top of my head. For some reason my brain prefers using wavelengths for Radio waves (short wave radio, long wave radio) while frequencies when looking at the whole spectrum.