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Re: WiFi question
From: Esmond <Esmond_Kane () harvard edu>
Date: Fri, 19 Nov 2004 15:54:03 -0500

On 10:50, Fri 19 Nov 04, Paul Schmehl wrote:
--On Thursday, November 18, 2004 09:32:27 AM -0600 Paul Schmehl
<pauls () utdallas edu> wrote:

--On Wednesday, November 17, 2004 12:41:44 PM -0500 "Lachniet, Mark"
<mlachniet () sequoianet com> wrote:


I find it hard to believe that this is possible.  2.4Ghz is the 9th
harmonic.  By the time you get to the 4th harmonic of a signal, even in
very very noisy radiators, the strength of the harmonic component of the
signal is extremely minute.  And, given the fact that one of those sensors
(which most likely does *not* truly operate in the 240MHz portion of the
spectrum) will have a very low output (Part 15 device), the 10th harmonic
of that signal will be undetectible as it will be at or below the level of
background noise.

Despite your disbelief, this is basic physics and a core component of
musical amplification. It may not be solely due to the device. There may
be building cavities amplifying the signal. The is a radio wave we're
talking about after all.

Sufficient Harmonic Oscillation can result in a boosted signal or
Resonance:

http://www.sasked.gov.sk.ca/docs/physics/u5c42phy.html

Finally, if a device managed to get past all of the improbabilities above,
the chances of it *accidentally* creating a signal that looked like an
802.11 beacon packet, complete with preamble, header, etc is so off the
charts as to be laughable.

Its not an accident. Cheap equipment = low quality control = no
suppression and filtering.

One other thing...  If that device truly was operating at 240MHz, then the
first harmonic would be 480MHz.  I'm pretty sure that frequency lies in the
public service bands (ie fire/police).  If not, its very close.  Given that
and the fact that the first harmonic would be much stronger than the 9th
harmonic, I'm pretty sure someone in those bands would have complained
loudly to the FCC as they don't take intereference issues in those bands
lightly.

Eh, not only does this happen, heres a recent story on one instance:

http://www.technewsworld.com/story/37435.html

Paul Schmehl (pauls () utdallas edu)
Adjunct Information Security Officer
The University of Texas at Dallas
AVIEN Founding Member
http://www.utdallas.edu

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html

--
Esmond Kane
Sys Admin
HUAM DIT

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html


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