Subject:  (Fist) Re (Curry) Re EMR - How close is too close? (fwd)
Date:     Mon, 5 Oct 1998 213300 -0500 (CDT)
From:     "Roy L. Beavers" <rbeavers@llion.org>
To:       emfguru <rbeavers@llion.org>
--------------------------------------------------



---------- Forwarded message ----------
Date: Tue, 06 Oct 1998 09:44:15 +1000
From: Stewart Fist 
To: "Roy L. Beavers" 
Subject: Re: (Curry) Re: EMR - How close is too close? (fwd)

Bill Curry writes

>  At the distances you mentioned to both types of microwave sources, I don't
> think you can use a simple spherically expanding radiation law to estimate how
> the radiation power density will fall off with distance from the sources you
> mentioned.  This is because TV antennas and Cell phone antennas are
> directional, and hence their emitted radiation will off with distance more
> slowly than an inverse square law until you are far enough away from all the
> sources for them to appear as nearly point sources.

Not so.  Even a searchlight falls off in intensity according to the inverse
square law.  It is just that the concentration of power at the source makes it
act as if it were a more powerful source than it would if it were an isotropic
radiator (spraying the power in all directions).  So the inverse square law
still acts, but you should consider the radiator to be more powerful than its
rating because the energy is concentrated in one direction.


-- 
Stewart Fist - writer and columnist
See http://www.newsit.com.au/index_opinion.htm 
       http://www.abc.net.au/http/sfist/         (some archives)
       http://www.electric-words.com              (main archives)
70 Middle Harbour Road, Lindfield, 2070,   N.S.W,   Australia
Phone +61 2 9416 7458                        Fax  +61 2 9416 4582



Archive provided courtesy of WaveGuide, http://www.wave-guide.org
Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html