[Ninux-Wireless] Perche' 2.4Ghz?

[Clauz]

Ciao.
Oggi ho scoperto che questa cosa non e' ancora passata qui in lista: uno
studente ha raccolto dei fondi per fare una tesi sull'origine della
scelta della frequenza dei 2.4GHz per forni a microonde e quindi Wi-Fi,
bluetooth, etc. A quanto pare la frequenza di risonanza dell'acqua non
c'entra [*], e la verita' sembra sia racchiusa in antichi documenti
dell'FCC.

http://www.indiegogo.com/why2point4?c=home
http://www.indiegogo.com/why2point4?c=activity

"""
The question

It seems like a simple question, why do so many of our wireless
conveniences like Wi-Fi and Bluetooth work on such a particular
frequency? There's so many frequencies available, yet somehow they all
ended up there.

I'm writing a masters thesis on interference between wireless systems,
and as soon as I began writing my introduction, explaining that these
things interfere because they're all on the same frequency band, I
stumped myself by wondering why that was.

Being a student, I had time, being an engineer, I had knowledge and
being slightly crazy I had the insatiable desire to know why.


What we know

Most techies, when asked would tell you it's because of microwave ovens;
and they're partly right, but microwaves as we know them didn't exist
when these frequencies were laid down, and anyway, microwave ovens can
work on pretty much any frequency between 1 and 20 GHz.

I did my digging, and found the original microwave oven patent calls for
frequencies around 3GHz - so why 2.4?

I've done a lot of research across old documents (1940's) made available
by groups like the ITU and the FCC. Unfortunately the trail leads
definitively into FCC territory, and the last piece of the question, the
documents describing the hearings that led up to the decision, are not
available online.
"""

Clauz

[*] http://www.howeverythingworks.org/page1.php?QNum=1456