Re: [oc] Project suggestion: RFID tag reader

[Simon Gornall <simon@gornall.net>]

On Mon, 2002-11-18 at 03:49, Rudolf Usselmann wrote:
> On Sunday 17 November 2002 19:54, John Dalton wrote:
> > Here is a suggestion for a project:
> >
> > A reader for Auto-ID RF identification tags:
> >
> > http://www.autoidcenter.org/
> >
> > As I understand it, auto-ID will be replacing the
> > barcodes you see on practically everything you
> > purchase.   The main differences to a barcode are:
> >
> > 1) You can't read the number without a reader.
> > 2) Individual items will be coded with unique numbers.
> >    With barcodes, all packets of "brand X" washing
> >    powder are marked with the same number.  With RFID
> >    tags, each packet carries a unique number.  If you
> >    are carrying that packet of washing powder (or wearing
> >    clothes), it will be possible to track your movements.
> > 3) RFID codes can potentially be read over longer distances
> >    than barcodes can (ultimately by satellite???).
> 
> Holly sh... !!!  I think what we really need is a RFID Jammer ! I'm
> not exactly thrilled by haveing any government agency (specially
> a foreign one) being able to track my movements.
> But than, aren't these things powered by the reader ? I guess
> they would have to Emmit some sort of energy beam from low
> orbit to activate a particular (or all) RFIDs in an area ...
> Scary though ...

The above is a bit optimistic as regards current technology, and a ways
into the future as well, IMHO. RFID runs on (typically) 125KHz or
13.46MHz (which interferes quite nicely with the PAL colour burst
frequency ...) Read range for the "normal" 2cm-wide tags is about 10cm
plus or minus 2cm depending on aerial and conditions (it's a lot less in
wet conditions, for example). It can be larger as a function of aerial
radiative power, but you're stuck with the inverse square law... It's
also larger with respect to aerial area, although there are limits due
to tuning requirements.

RFID is powered by the transmitter, and I wouldn't like to be in the
beam-width of any satellite which could power the chip from orbit! 

Oh yeah, they're also dependent on the phase of the moon. At least
that's the way it seemed when I was using them a year or so ago. They
may have got over that :-)

Simon.


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