hello! experience with 802.11x and extreme humidity?

[George W Gerrity]

On 08 Jun 2004, at 22:03, wireless-request at lists.samba.org wrote:

>
> Message: 1
> Date: Mon, 07 Jun 2004 16:55:29 -0700
> From: "Dr. Steven R. Hessel" <srhessel at netscape.net>
> Subject: hello! experience with 802.11x and extreme humidity?
> To: wireless at lists.samba.org
> Message-ID: <40C50071.9000606 at netscape.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Dear Darryl;
>
> I have found a fragment of something you wrote in 2002.  It reads:
>
> The book has some information under the heading
>     "The non-existant microwave absorbtion peak of water"
>
> It gives a few references on absorbtion of water at varieous
> frequencies, and notes that microwave ovens do not work by exciting
> water molecules, but by twisting both the dipoles in a water atom
> increasing its kinetic energy.
>
> Anyone looking at the theory of 802.11 and how to break the standard
> should look at this book. I know a lot about 802.11, but this gives so
> much more...
>
> Darryl
>
> ---------
> Darryl Smith, VK2TDS   POBox 169 Ingleburn NSW 2565 Australia
>
>
> Since I am interested in the R.F. characteristics of materials in 
> 802.11 signals (including absorption) do you know of any good 
> references on the subject?
>
> Thank you.
>
> Sincerely yours,
> Steven Hessel
>
A Google search on “RF absorption in water vapor” yields lots of hits, 
but

<http://www.rfcafe.com/references/electrical/atm_absorption.htm>

is just what you want. As you can see, atmospheric absorption at 802.11 
frequencies (2400–2463 MHz) is pretty low, and is mainly due to Oxygen, 
not Water Vapour.

Rain, of course, can scatter radiation, but it is inversely 
proportional to the sixth power of the ratio of the wavelength of the 
radiation and the size of the droplets. Thus, scattering at RF 
wavelengths is negligible. By the way, this sixth power law means that 
blue light (~4000 Å) is scattered about 18 times greater than yellow 
light (~6500 Å), and that is why fog lights have traditionally used 
yellow-filtered light rather than white light.

George