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[QUOTE="a33, post: 4652229, member: 195592"]
Dish focal length 72 cm likely is the focal length for the mother (primefocus) parabola. Would be [B]about[/B] the distance bottom of dish to focal point (depending on still unknown position of parabola vertex).
Needed f/D setting can be calculated from LNB viewing angle (f/D-value from an offset dish has a rather indirect relation to f/D setting of a feedhorn!).

Why not measure some more dish measures, and thus be able to calculate more precise parabolic specs?

Needed are exact height and width measure of the parabolic working area of the dish (assuming the dish has a flat face, and passes the string test).

And depth measure, very precise: easiest at the center 
(but taken at another height of the dish is also possible, but the measureing height must then also be given (as height along dishface, measured from the bottom; or (better, I think) as straight-line-distance from bottom to measuring point of the dish surface) ).
Please do mention which of these measures you've taken.

Greetz,
A33
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