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'[OT] Late arival on the store security device thre'
1998\01\27@004856 by Chris Eddy

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I picked up some asprin at the store today, and lo and behold, it had a
security sticker on it.  I thought of that old thread on these types of
devices, and took a closer look.  The device is a spiral foil antenna,
stuck face down on the box.  The outside dimension of the square is
37mm, the inside dim is 13mm, and the turns are 11.  Now, are there any
ambitious individuals out there that can model the RF loop in software,
and figure out what the frequency response of the loop is?  Just a
thought.

Chris Eddy, PE
Pioneer Microsystems, Inc.

1998\01\27@073706 by peter

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Chris Eddy wrote:
>
> I picked up some asprin at the store today, and lo and behold, it had a
> security sticker on it.  I thought of that old thread on these types of
> devices, and took a closer look.  The device is a spiral foil antenna,
> stuck face down on the box.  The outside dimension of the square is
> 37mm, the inside dim is 13mm, and the turns are 11.  Now, are there any
> ambitious individuals out there that can model the RF loop in software,
> and figure out what the frequency response of the loop is?  Just a
> thought.

Without the capacitance no
but anyone with a GDO(grid dip osc) that covers that frequency
should be able to tell you, if it hasn't been disabled

spam_OUTpeterTakeThisOuTspamcousens.her.forthnet.gr

1998\01\27@173313 by Alberto Smulders

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Chris,

A "standard" resonating frequency for HF security tags seems to be 8.2 MHz
(also 9.5 MHz is mentioned), while for UHF (microwave) tags a frequency of
915 MHz seems to be used, see US Patents  5,574,431; 4,063,229 and
3,895,368.
In Patent 5,300,922 a system is described where the frequency of the
transmitter is swept between 7.4 and 8.8 MHz (at a rate of 178 Hz), with a
synchronized circuit in the receiver (there are more patents of this sort, I
don't have the numbers here), probably in order to count for small
off-frequencies because of production methods and/or the parasitic
capacities caused by the articles the labels are affixed on etc.
The patents you can see on:

     http://patent.womplex.ibm.com/.

Regards,

Albert Smulders
InSAD - Encarnaci—n
Paraguay


-----Mensaje original-----
De: Chris Eddy <.....ceddyKILLspamspam@spam@NB.NET>
Para: PICLISTspamKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Fecha: Martes 27 de Enero de 1998 01:54
Asunto: [OT] Late arival on the store security device thread


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