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

Sorry, that should be an inverse fourth power law (Rayleigh 
Scattering). I was going by memory (30 years ago) and should have 
checked it _before_ I shot off my mouth. That still gives a hefty seven 
times advantage for yellow light over blue, and incidently, explains 
why the sky is blue.

George