AndyS wrote:

Andy asks:

The Friis equation at the above website states that the distance
exponent may be a number different than "2".

Can anyone here explain why a number other than "2" could be
used, and under what conditions ??

Thanks,

Andy W4OAH

The exponent of 2 assumes no dissipative path loss. That is, the
reduction in field strength is due solely to the power being spread out
over an area which increases with distance from the source, and not to
any reduction in the total power at any distance. A larger exponent
would be appropriate when the path is lossy, for example when ground
wave attenuation is present. A path through air could also get lossy at
microwave frequencies due to water in the air in liquid or gas form, and
at extremely high frequencies due to absorption by various atmospheric
gases.

Roy Lewallen, W7EL