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Enter the antenna's 3 dB vertical beamwidth (<120°)		degrees
Enter the antenna's downtilt angle (<90°)		degrees
Enter the effective Earth radius (K factor)
Enter the antenna's height (AGL)		meters feet

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AGL  Above Ground Level.  Height above common ground to the the mid-point of the radiating antenna.

The K factor accounts for refraction of radio waves close to the surface of the earth.  For antenna towers less than a couple of thousand feet above the surface, a K factor of 1.33 is usually adequate for most line-of-sight calculations over average terrain.

Typical Values of K

                                        Summer  Winter

Dry mountains (above 1500 meters)       1.20    1.20
Mountains (to 1500 meters)              1.25    1.25
Midwest and Northeast                   1.50    1.30
South and West Coast                    1.55    1.35
Southern Coast                          1.60    1.50