Jack, Another small challenge! I'm planning to make a 3 or 4 km link over the sea across a small bay here in Tenerife. One side of the link is fairly high (40-50m above sea-level), but the other is at half the height (20m). In theory I am not infringing the Fresnel zone (at 3 miles is almost 8m), but I am slightly concerned over possible reflections from the sea. I know that normally water absorbes microwaves, so I don't think it will be a problem, but I wondered if, on those days of dead-calm, there could be any reflection; the signal is almost parralel to the water, I am using horizontal polarisation: what is the worst that could happen to the link? Now that we're talking about it, how low can I go with my link? What would happen with vertical polarisation? Are there any "water-effects" that I have to be especially aware of? That I can even take advantage of? Could one "reflect" ALL of the signal? WOuld that be usefull?
Sorry if its abit long! Andy Middleton
