I’d like to confirm that on the B5, chains 1 and 2 are horizontal, 3 and 4 are vertical. It turns out that they behave rather differently on an over-the-water path.
It’s well known in the microwave business that over-the-water paths are risky. All sorts of strange things can happen, especially if the path is low. Ducting effects near the surface, especially around dusk, can bend signals. And tides can move the Fresnel zone boundaries, if the link is low. It turns out that the tide effect can be really, really intense…
Someone I work with put up a whole bunch of B5 and B5c’s along the coastline (for a maritime application). In some cases the link is high enough so that it’s pretty steady. But when I chart the chains, I see two chains having shallow fades and two chains having deep fades on what looks like a tide-related basis. I am guessing that this is vertical. The one with the biggest impact is 14 miles long, mostly over the ocean. It’s actually a B5c, but I suspect chain 3 and 4 are vertical. From this chart, I may suggest that future links be configured slant 45 polarization, to avoid this.
The red line is total power, but only the purple, not blue, gets lost completely during what seem to be mostly tide-related events.
I think the moral is that yes, you can shoot over water, yes, it will behave weirdly, and having two chains with different polarizations is also helpful, since they don’t fade equally, but I think vertical is worse.