Editing Path loss (section)

==Radio engineer formula==
Radio and antenna engineers use the following simplified formula (derived from the [[Friis transmission equation|Friis Transmission Formula]]) for the signal path loss between the feed points of two [[isotropic]] antennas in free space:

Path loss in [[decibel|dB]]: 
:<math>L = 20 \log_{10}\left(\frac{4\pi d} \lambda \right) </math>

where <math>L</math> is the path loss in decibels, <math>\lambda</math> is the wavelength and <math>d</math> is the transmitter-receiver distance in the same units as the wavelength. Note the power density in space has no dependency on <math>\lambda</math>; The variable <math>\lambda</math> exists in the formula to account for the [[Antenna aperture|effective capture area]] of the isotropic receiving antenna.<ref name="Stutz">{{cite book|last1=Stutzman|first1=Warren|last2=Thiele|first2=Gary|title=Antenna Theory and Design|date=1981|publisher=John Wiley & Sons, Inc.|isbn=0-471-04458-X|page=60}}</ref>