[aprssig] more on locating

[Jim Lux]

Bob wrote:
"Here is how I envision that Ham Radio can use
these RFID tags:

We build these pocket-tracker type RFID=>APRS
translators.  They are simply the PIC and RF transmitter
of the Pocket Tracker, comnbined with the RFID reader
for our ARRL style RFID tags.  Depending on the
size of the reading device, these "translators" can
be mounted in any room or gate, or checkpoint
where we need to know where adjacent participating
hams are.
"


But... you don't need the RFID tags for this.  The "trackees" are already 
carrying a transmitter that beacons its name periodically.  In either case 
you'd have to have some sort of centralized widget that receives the ID 
signals (be they RFID or APRS) and translates that to 
position/location/id/whatever.

Why not just detect the 144.39, read the id, and shoot that out.  If you 
want a cheap tracker source for nametags, use one of the little transmitter 
tags with unique ids (like garage door openers and car keys).  Nothing says 
it has to be in the ham bands.  Or, if you want to be in the ham bands, why 
not program a PIC to send your coded callsign on 40 or 80m (run the clock 
at, e.g. 7.1 MHz), and then DF that indoors. (There ARE some legality 
aspects on this latter approach that would need some work).  Actually, 10m 
might work, since lots of processors can run at 29 MHz, or you could run at 
a third of that, and filter for the third harmonic (or maybe radiate on 6m, 
using the third or fifth harmonic).  The antenna can actually serve as part 
of the filtering network.