AndyS wrote in
:



Owen Duffy wrote:
Look up the Friis Transmission equation on Google.

Here is a little application for solving the Friis Transmission
equation: http://www.vk1od.net/software/fsc/ .


Andy asks:

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

I don't think I say that, Friis uses an exponent of 2, but the calculator
can also solve the equation with an exponent other than 2.

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

An example is that the FCC stipulates exponents of other than 2 for some
field strength interpolation / extrapolation, up to 4 IIRC, and this is
for application in real situations at closer distances than radiation far
field conditions.

The use of the exponent is to account for some other effects. In some
cases the value of the exponent has been challenged. If I understand the
case correctly, the ARRL has challenged some instances used for BPL and
the court has required the FCC to scientifically substantiate its
exponent, or use another which it can scientifically substantiate.

The ability to specify the exponent is principally provided for peforming
those interpolation / extrapolations.

Owen


Thanks,

Andy W4OAH