Reference Designer Calculators
Free Space Loss Calculator
Free Space Loss is the power loss of a radio signal as it travels through free space. Free Space loss calculation helps RF designers estimate the receive power strength for a given transmitter power. It helps determine the line of sight distance.
Free space loss depends upon frequency and distance. The loss increases with increas in frequency and obviously with increase in distance. Following is the formula for Free Space los $$ FSPL(dB) = 20 log_{10}\left(\frac{4π}{c}\right)+20 log_{10}(d)+20 log_{10}(f) $$ Where,
f is the signal frequency (in hertz),
d is the distance from the transmitter (in metres),
c is the speed of light
or
Free Space Loss (dB) = 36.6 + 20 x Log (Frequency (MHz) x Distance (Miles))
If you wish to enter distance in kilometer , check the calculator here
For derivation of the Free path loss formula check here