Date: Sun, 06 Mar 2011 10:59:00 -0500 From: Etienne Robillard <erob@gthcfoundation.org> To: Diane Bruce <db@db.net> Cc: freebsd-current@freebsd.org Subject: Re: can somebody explains OFDM in FreeBSD? Message-ID: <4D73AF44.9070909@gthcfoundation.org> In-Reply-To: <20110306153517.GA86035@night.db.net> References: <4D7398C6.8030800@gthcfoundation.org> <201103061533.32138.hselasky@c2i.net> <4D73A085.4030009@gthcfoundation.org> <AANLkTinAowO5pOvzA0XOy0RX7_jkZLK6ivfF3wXNLjh=@mail.gmail.com> <4D73A41A.4050109@gthcfoundation.org> <20110306153517.GA86035@night.db.net>
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. > https://gthc.org/investigations/OFDM/72_armstrong_ofdm.pdf > > That paper is a basic paper. COFDM is being used just about everywhere now. > OFDM was used in the Telebit modems of years gone by. To this day > (last I checked) it is superiour to the v32.bis format used today on > third world phone lines, because of its ability to ignore dead spots > in the frequency spectrums used. > > ... > Reference(s) please? >> I'm worried from a amateur computer scientist point-of-view about the >> harmfulness >> of EMF fields; in particular the ELF/VLF frequencies as defined in OFDM, >> for operating WLAN devices as 'ethernet-class subcarriers'.. >> > I personally would not worry about DSL and ethernet. The fields are > self cancelling due to the twisted pair. It's a transmission line. > I do worry much more about cell phone and wifi signals. I advise others > not to use cellphones for long periods of time without a remote earpiece. > (And of course, do likewise). Cell phone towers provided they are up high > enough do not bother me. Keep in mind the inverse square law here. > I would also suggest you look for the papers on double blind studies of > so-called RF sensitive individuals. (ES) I am very sceptical personally > of the effects. That said, I would not want to be within the near field > of any high power transmitter. This is why broadcast stations have > fences around their antennas and warning signs. The high power stuff > is dangerous. > > Its not phone lines who are the main issue, rather the radiation levels of OFDM ethernet class devices (including USB devices and routers) using ELF/VLF frequencies below 30khz as per the newer 802.11(ng) drafts... ;-) -- Etienne Robillard Company: Green Tea Hackers Club Occupation: Software Developer (and CEO) E-mail: erob@gthcfoundation.org Work phone: 450-936-2123 Website (Company): https://gthc.org/ Website (Blog): https://gthc.org/blog/ PGP public key fingerprint: F2A9 32EA 8E7C 460F 1728 A1A7 649C 7F17 A086 DDEC During times of universal deceit, telling the truth becomes a revolutionary act. -- George Orwell If a free society cannot help the many who are poor, it cannot save the few who are rich. -- John F. Kennedy
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