Re: WiFi question

[Esmond <Esmond_Kane () harvard edu>]

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
>
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--
Esmond Kane
Sys Admin
HUAM DIT

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