Machining Waveguides for 122 GHz Operation Is Delicate Work

Interestingly, at the beginning of the video he mentions that 122 GHz antenna transmission has shown to work for distances of 60 kms.

The curvature of the earth is that you need to be elevated 400-500 meters over sea level to have a sight of line of 60 kms to the horizon; the horizon is only 5 kms away at the 2 meters elevation.

Perhaps those measurements were done mountaintop-to-mountaintop.