<div>The runners in jogging races wear a cylindrical tag tied to their shoe laces. Looks a lot like a speedpass tag.</div>
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<div>I gotta say, I sure wish we could change the tag ID numbers to the ascii of my callsign.</div>
<div><br clear="all">Wes<br>---<br>God help those who do not help themselves.<br><br><br></div>
<div class="gmail_quote">On Mon, Feb 1, 2010 at 16:14, Patrick <span dir="ltr"><<a href="mailto:winston@winston1.net">winston@winston1.net</a>></span> wrote:<br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">The issue is you run into is with the magnetic field generated. Passive rfid tags are being powered by the magnetic inductance of the field they are moved through, so you run out of power the further away from the reader you are. This is sorta on purpose because they also typically do not contain collision handling ability so you can't have more then one tag in the read area at the same time.<br>
<br>There are commercial grade reader / chip systems which don't have the same constraints, but the costs go up accordingly.<br><br>That said you really don't need more range.. Instead of putting the chips on their hats, put them on their feet.. if people are walking through the door with both their feet 10" off the floor, then they are purposely making themselves unreadable. This is the way most RFID based timing systems work for distance races.<br>
<font color="#888888"><br>p</font>
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<div class="h5"><br><br>Quoting Robert Bruninga <<a href="mailto:bruninga@usna.edu" target="_blank">bruninga@usna.edu</a>>:<br><br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">I still think APRS-RFID... Is a next thing for APRS<br>experimenting<br><br>Every ham hat could have a $2 chip in it.<br>
<br>Then we can tell who enters the clubhouse or EOC... (it gets<br>converted to APRS...)<br>See <a href="http://www.aprs.org/aprs-rfid.html" target="_blank">http://www.aprs.org/aprs-rfid.html</a><br><br>Problem is, the maximum range reader I can find is only good for<br>
10 inches max and it costs about $24:<br><a href="http://www.sparkfun.com/datasheets/Sensors/ID-12-Datasheet.pdf" target="_blank">http://www.sparkfun.com/datasheets/Sensors/ID-12-Datasheet.pdf</a><br><br>It has provisions for a wind your own antenna but still can<br>
only get to about 10 " (25cm). But since hams are RF<br>experimenters, it would seem that we could improve on this. One<br>sentence in the limited docs says that there has to be enough<br>energy to activate the chip. This implies to me that the limit<br>
is on the energy transmitted to the chip, not necessarily the<br>read range. Frequency is 125 KHz.<br><br>To get reliable coverage for people walking through a door, I<br>think we need about 48" range...<br><br>Does anyone want to fill us in on the details? I assume a 125<br>
KHz carrier in the antenna coil provides the energy for the RFID<br>chip (this can be scaled up... Just needs more power)... But<br>then I guess it has some off cycles so the chip can send back<br>the 32 bit code?<br><br>
Bob, WB4APR<br><br><br>_______________________________________________<br>aprssig mailing list<br><a href="mailto:aprssig@tapr.org" target="_blank">aprssig@tapr.org</a><br><a href="https://www.tapr.org/cgi-bin/mailman/listinfo/aprssig" target="_blank">https://www.tapr.org/cgi-bin/mailman/listinfo/aprssig</a><br>
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