free-space loss

In telecommunication, free-space loss is the signal attenuation that would result if all absorbing, diffracting, obstructing, refracting, scattering, and reflecting influences were sufficiently removed so as to have no effect on its propagation. Note: Free-space loss is primarily caused by beam divergence, i.e., signal energy spreading over larger areas at increased distances from the source. The equation for free-space loss is below where $\lambda$ is the signal wavelength, f is the signal frequency, R is the distance or radius of the signal from the transmitter, and c is the speed of light in the signal transmission medium. Note that the units used should be consistent, e.g.,

\lambda

and R in meters, and c in meters/second.

free\ space\ loss = \left ( \frac{4\pi R}{\lambda} \right )^2 = \left ( \frac{4\pi R f}{c} \right )^2

Source: from Federal Standard 1037C and from MIL-STD-188

<< Previous

Word Browser

Next >>

filled cable
filtered symmetric differential phase shift keying
firmware
fixed access
flag sequence
flat weighting
flood search routing
flutter
flywheel effect
fm improvement factor
fm improvement threshold

foreign exchange service
foreign instrumentation signals intelligence
forward echo
forward error correction
forward scatter
frequency of optimum transmission
four wire circuit
four wire terminating set
data frame
frame rate
constitution of vermont

frame slip
frame synchronization
framing
framing bit
freeze frame television
f region
frequency assignment
frequency assignment authority
frequency averaging
frequency change signaling
frequency compatibility

frequency deviation
frequency exchange signaling
frequency frogging
frequency sharing
frequency shift
frequency shift keying
frequency standard
fresnel reflection
fresnel zone
front to back ratio
fts2000