BTW, speaking of "peeking" over another building, can you > explain why the fresnel zone around a dish is so large? I > know it exists and that I have to allow for it, but I've > never understood the reasons.
It's been a long time since I did any Fresnel zone calculations (I retired in 2000), so I don't have access to my good old GTE Lenkurt manual [*] on the subject. However, a Google search turned up a couple of links that look right:
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[*] GET Lenkurt: Engineering Considerations for Microwave Communication Systems. By Senior Staff Engineer Robert F. White (preface). Out of print and usually unavailable, although Amazon has a used hardcopy at the moment (2nd printing of 1970 edition) for $399.13.Neal McLain