Focal Length Calculation

Anyone have a formula for calculating the focal length of a C band LNBF? I am trying to get a BSC741-2D set up on a 7 1/2 foot Super Ten dish. Everything else seems fine and I can get Signal Strength of 84% to 99% but 0% Q. Hoping it is only my focal point adjustment that is off.

Look at these links. EB

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