While practical range testing is a preferred method to determine range, theoretical mathematical formulas can be used to predict the transmission range of Digi radios through freespace. This is the fromula for free space path loss:
C = speed of light = 3 x 108 m/s
The freespace formula can be used to predict radio performance in an ideal environment such as mountain top to mountain top, or on the ground to an Arial vehicle.
In more practical applications the ground can have some interference especially in moderately rolling terrain where the ground can have a significant effect on the path loss. We usually build in a fade margin of 21 dB in our calculations.
There are many online free space path loss calculators that can be found by doing a search on the term.
You can use repeaters to extend the link distance of an application or use the mesh functionality in the XBee and Xtend radios. See the application note on Digi's website for additional information by searching on the terms "digi range test" or "repeater funcationality digi" or "digimesh".
Aug 23, 2017