On 3/9/2015 3:29 AM, Jeff wrote:

I've been lurking in this thread and it reminded me of a time many years
ago when I was working on a receiver setup. A colleague gave me a book
with an equation for signal strength of a signal in the cell phone
frequency range in various terrestrial environments. I had a little
trouble accepting an arbitrary equation that wasn't at least close to
the typical 1/r^2 formula in free space. I seem to recall there was no
1/r^2 term at all rather it was more like a linear or maybe had a
rlog(r) term.

In any event, no one could explain where the equation came from. I
suppose it was an empirical equation rather than something derived from
theory. Ignoring waves bounced off the upper atmosphere, I assume the
earth acts to help focus the signal and strengthen it close to the
ground?


You are correct, most of those formulas are empirical, base on actual
observations. Look up papers by Egli and by Hatta, they will five you
some idea on how theses formulas were derived.

Jeff

As are basically all formulas. Even Ohm's Law was derived from actual
observations.

Although Einstein's equations such as E=mc^2 wasn't derived from actual
observation, it did come by projection of existing knowledge by an
exceptional mind.

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