Dish antenna Calculations

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Dish antenna Calculations

Postby vcarriere » Thu Nov 04, 2004 10:10 pm

I'm trying to figure out the focal point of a dish antenna that is elliptical (Not the same diameter everywhere)(from Bell Expressvu like this one).
Image
I found the folowing formula to find the focal point of a dish but its for a parabola, f=D²/16C where D is diameter and C center to top of dish. Is there a formula like this for elliptical dish? Also should i use the normal mounting point which is angled and does not hit the dish perpendicular but rather at a slight angle like the first dish in the illustration or make a mounting point out of 3 metal rod to hit the perfect center?

Also, i know because i read it, that the f/D ratio for 2.4Ghz should be between 0.25 and 0.55 but why?
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vcarriere
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