[Antennas] Signal loss (path loss)

[Terry Conboy]

At 11:56 AM 2007-08-27, A10382 wrote:
>If anyone has the path loss formulae handy, they would be appreciated.

This is the standard Friis free-space-loss equation between isotropic 
antennas, in decibels:

FSL (dB) = 32.45 dB + 20*log[frequency(MHz)] + 20*log[distance(km)]

or for subjects of the Empire:

FSL (dB) = 36.6 dB + 20*log[frequency(MHz)] + 20*log[distance(miles)]

Of course, the free space loss doesn't account for attenuation 
through the earth's atmosphere for satellite communications.

FYI, from http://voyager.jpl.nasa.gov/mission/didyouknow.html

"The sensitivity of our deep-space tracking antennas located around 
the world is truly amazing. The antennas must capture Voyager 
information from a signal so weak that the power striking the antenna 
is only 10 exponent -16 watts (1 part in 10 quadrillion). A 
modern-day electronic digital watch operates at a power level 20 
billion times greater than this feeble level."

73, Terry N6RY