"Focal Length Calculator"
"A.C.H.1"
"A satellite dish antenna is a lot like a camera, taking a picture of"
"the microwaves being transmitted by a satellite in orbit.  There is"
"a proper distance between the lens and the film in a camera for a"
"picture to be in focus.  The same is true for a satellite dish antenna."
"The focal length, on most home satellite dish antennas, is the distance"
"between the center (apex) of the dish and the feed assembly.  To"
"calculate the focal length, you need to know the diameter of your dish,"
"in inches, and the depth of the dish.  The depth of the dish can be"
"measured by attaching a piece of string to one edge of the dish, pull"
"it across the dish to the opposite edge and attach it.  Now measure the"
"distance, in inches, between the apex and the string.  Some feed"
"assemblies are designed for dish antennas with a certain f/D ratio."
"The f/D ratio is the difference between the focal length and diameter."

