This shows the four rectangular waveguides (coming from the radios in the building) being combined into one round waveguide up to the antenna horn. I believe the larger waveguides carry the 4 GHz signals, which have a longer wavelength, and the smaller waveguides carry the 6 Ghz signals with a shorter wavelength.

Note, however, that there are two pairs of each size of waveguide, and that the same-size waveguides are inserted into the round waveguide perpendicular to each other. This is how the vertically- and horizontally-polarized radio waves of the same frequency can coexist on the same route ? with each frequency transporting totally different circuits. By doing this, four different radios share one waveguide/antenna assembly. I assume that if an antenna is rotated on its vertical axis to accurately point to another tower, the entire assembly of combining networks, round waveguide, and horn must be rotated as one unit. Hence, the flexible black waveguides are needed to make the graceful 90 degree bends and rotations. It?s quite a plumbing project.