hello! experience with 802.11x and extreme humidity?

Bob Tenty bobtenty at sympatico.ca
Mon Oct 14 13:30:37 EST 2002


The whole meaning from ISM was changed from only medical
equipment, ovens and other equipment that should not or minimal
radiate to include wireless lans in certain ISM bands..
The easiest solutions was to change the definition of ISM..
due to industry pressure
Also because some ISM bands like 2.4 Ghz are more or
less worldwide and more equipment can be sold and
cheaper produced because of the higher quantities.
The ISM 2.4 Ghz band is not worthless and is partly shared
with licensed Amateur Radio already for 50 years.
They have their own satellites in that band, TV repeaters, data
links, etc and also use it for worldwide communications using the moon
as reflector (EME/ Moon bounce)
Also your local TV broadcaster can have licensed portable
microwave links higher in that ISM band (like in helicopters)
That is not to say that interference of microwave ovens
can be very very nasty :=( if you live in a city.
So it  is not a "free for all" band as you may have read in the press or
so but 'free' for some low power equipment who mostly are not allowed
to interfere with licensed services. 
DECT and GSM work in another band..

Bob Tenty
VE3TOK


 
----- Original Message ----- 
From: "Timothy Murphy" <tim at birdsnest.maths.tcd.ie>
To: <chris.hill at crhtelnet.com.au>
Cc: <wireless at lists.samba.org>
Sent: Sunday, October 13, 2002 10:59 PM
Subject: Re: hello! experience with 802.11x and extreme humidity?


On Sun, Oct 13, 2002 at 09:10:19PM +0800, Chris Hill wrote:
 
> Why do you say that 2.4GHz is a resonance frequency of water?  It's not.
> For a basic starter, see :
> http://howthingswork.virginia.edu/microwave_ovens.html

I found this article quite interesting,
but very unconvincing on one point.
The author says 
"Since leakage from these ovens 
makes the radio spectrum near 2.45GHz unusable for communications,
the frequency was chosen in part because it would not interfere 
with existing communication systems."

Both DECT phones and GSM phones use this frequency range
without apparent interference from microwave ovens.
I've never noticed any interference with WiFi from these ovens.

I've certainly always understood that 2.4GHz was alloted to ISM
because it was unsuitable for long-range wireless communication
on account of some interaction with something in the atmosphere.





-- 
Timothy Murphy  
e-mail: tim at birdsnest.maths.tcd.ie
tel: 00353-86-233 6090
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland




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