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[aprssig] RFID antennas

William McKeehan mckeehan at mckeehan.homeip.net
Mon Jul 14 14:40:17 UTC 2008


I would question the need for such a device. I can see it being used at
something like Dayton's Hamvention, but I wonder if there is a significant
enough collection of Hams in other avenues to justify the cost.

Where do you see this system used?
-- 
William McKeehan
KI4HDU
http://mckeehan.homeip.net


On Mon, July 14, 2008 10:33 am, Bob Bruninga wrote:
>> The RFID tags that are cheap are pre-programmed
>> with unique serial numbers.  We'd need some way...
>
> GOod point.  I wonder if we want to roll our own. Besides readers are
> expensive.  But if we do our own, then it becomes a nice ham club kit project.
>
> I think of an IR link.  The reader uses lots of IR LED's to interrogate as the
> ham walks through the door.  His tag responds in IR with his callsign ID.
>
> THe reader than sends out an APRS packet for that ham with his callsign and a
> vicinity plot in the vicinity of the reader.
>
> All it takes is a PIC, an IR transistor and an IR LED.  Done.
>
> A great ARRL project!
>
> Bob, WB4APR
>
>  (ie central server) to register your unique serial number and map it to a
> callsign.  There are RFID tags that are programmable, and they would be slick
> for this application...  I suppose you'd want a RFID reader to send data to a
> PIC processor that would combine a canned GPS location with the serial number
> of the RFID tag.  Perhaps you'd want the PIC processor to randomize the
> position it used with the RFID tag serial number?
>
> Hmm... many aprs clients will display a tactical callsign, so if the RFID pic
> processor were to construct a 3rd party APRS packet using the RFID serial
> number as the "callsign" we could manually assign it a tactical call of the
> user's actual callsign on our aprs client (like xastir).  But aren't we
> limited to 9 digits for a callsign in the aprs spec?  I think the RFID serial
> numbers are longer than that.  Of course the serial numbers would be serial in
> a sequence, so perhaps we could truncate the RFID number and just use the last
> 9 digits?
>
> I've thought about indoor tracking.... have a tiny track or open track (what
> have you) and program it so that it will transmit w/o a GPS fix.  Have a pic
> processor above the doorway into a room sending via IR either a fixed GPS
> position string (ie fake GPRMC), or a fake GPRMC that chooses random coords
> with set boundaries.  If you randomize the coordinates it will prevent
> everyone in the room from appearing to "stack up".  your tracker is able to
> receive serial data from a 38khz IR photo transistor or from your personal GPS
> unit.
>
> It goes like this....   When you walk indoors, the GPS will loose lock and
> begin to transmit (serially) that it is out of lock.  The pic processor in the
> opentracker should ignore this data.  The GPS data is fed to the open tracker
> via a 10k series resistor.  The data from the IR photo transistor is fed via
> no resistor and is easily able to "over power" the serial signal from the real
> GPS unit.
>
> If it were me, I'd place one of the fake GPRMC sentence generators over a
> doorway shining down at a 45 degree angle into the room.  One on each side of
> a door header to catch you entering the room and leaving the room.
> Wes
>
> On Sun, Jul 13, 2008 at 11:05 AM, Bob Bruninga <bruninga at usna.edu> wrote:
>
>> "The Texas Instrument HF Antenna Cookbook."
>> The designs are for RFID at 13.56 MHz.
>
> I seriously want to see the ARRL/Ham radio invest in RFID for ham radio ops.
> Embed the chip in the ARRL name tag.
> Then we can have gateways to APRS...
>
> Put one at each venu or checkpoint or clubhouse, or whatever.
> Range should be about 100 feet...
>
> Bob,WB4APR
>
>
>
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>
> --
> Wes
> ---
> Where there's silence, there is no Hope.
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