Subject: Re A question about Antennas (Teule)(Tegenfeldt).
Date: Thu, 05 Oct 2000 063105 -0500
From: Roy Beavers
To: guru
--------------------------------------------------
........Response from EMF-L........
Thanks Clas..... It is very reassuring to know that you are still
"with us"........guru.......
-------- Original Message --------
Subject: Re: A question about Antennas (Teule).
Date: Thu, 05 Oct 2000 13:20:17 +0200
From: Clas Tegenfeldt
To: roy@emfguru.com
At 06:01 2000-10-05 -0500, you wrote:
>-------- Original Message --------
>Subject: A question about Antennas
>Date: Thu, 05 Oct 2000 12:27:54 +0200
>From: teule
>Reply-To: teuleger@wxs.nl
>To: roy@emfguru.com
>CC: Wim Roskam
...
>other sources of radiation (radar, electrical engines, speed control etc.). His
>question is this: if you throw some stones in a swimming pool at different
>positions, than the waves spread out over the whole pool. When these waves meet
>each other, than you get at certain points strong waves or even wild moving
>water. The places of these strong movements are difficult to predict. That
>depends on the shape of the pond, the places where you throw in the stones and
>of course the timing.
This is called superposition of waves and is true for all kinds of waves,
mechanical
or electromagnetic fields. You get weak points and strong, another part of this
issue is resonance where the geometry of space and waves interact so that these
weak and strong points not only becomes pronounciated but also standing still at
the same place, also called standing waves.
>If the same phenomenon is valid for electromagnetic waves, than we might expect
>in the real world a lot of places, where radiation really gets out of hand,
>although the distance to the GSM towers do not suggest a problem. These places
>depend on antenna-placement, the siting of buildings, reflections (glass or
>aluminium walls?), and your own position. Walking though a city can, in EM
>sense, become an interesting experience.
Theory is fine, but only be measurements and experiments can we even start to
comprehend the complexity out there in the real world. No model of any kind
can approximate the chaotic complexity.
>Do we have any experience or measurements on this possibility? Did anyone ever
>do a series of measurements during a stroll though a city? The question is
>simple, but I suspect that the answer is overwhelmingly complicated. This looks
>like chaos-theory, does n't it?
You can see this by yourself just by moving your FM radio around in your
room and
see that you have bad reception in some places and good in others, amazingly
theory and practice comes together and you will find those spots spaced around
some meters apart, if you do the same thing with your cellular phone (if your
field strength meter is useful enough) you will find those weak and strong
points are just some tens of centimeters apart (wavelength for 100 MHz is 3
m and
for 1000 MHz is 0,3 m, depending on geometry you will find nodes at some special
fractions of a wavelength).
The answer is simple, but the complexity is overwhelming and chaotic may be one
word for it, but the rules of the game is NOT chaos theory but quite stringent
and "simple" and quite predictable, if you know all the parameters of a space
you can predict it completely (no chaos theory at all, no fractals). Of course
in the real world we havenīt the time or money to map out all the parameters...
Just go ahead and measure!
>Gerrit Teule
>Netherlands
Clas Tegenfeldt
BEMI
Tornevalla Gamla Skola
S-590 62 LINGHEM, SWEDEN
tegen@bemi.se, http://www.bemi.se
Telephone +46 (0)13-74 000, telefax +46 (0)13-13 47 00
Archive provided courtesy of WaveGuide, http://www.wave-guide.org
Reprinted with permission of Roy Beavers, http://www.emfguru.com