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 _______________________________________________ Wireless mailing list Wireless@ml.ninux.org http://ml.ninux.org/mailman/listinfo/wireless