Can you explain how this works, like we're a class of 8th graders? We'll,
7th graders, really. See, 8th grade just started, but we're still reviewing
from last year...
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Ummm, okay. Let's start by taking apart a GPS unit. Get rid of the
display, keyboard and housing, the guts boil down to a circuit board
about the size of a business card. You still need the antenna and a
source of power but the heart of the GPS unit is that single circuit
board, which has been available as new-surplus for at least ten years.

Whenever there's power to the circuit board -- and the antenna can see
the sky -- the circuit board spits out a constant stream of data. The
data would normally go to the GPS units display.

What hams have done is to make an equally small circuit board that
takes that stream of data, encodes it in a usable format and feeds it
to a ham radio -- typically a 'walkie-talkie' that uses the 2-meter
ham band. The ham radio broadcasts the data in short bursts for all
to hear. We call it our 'Automatic Position Reporting System' and it
has proven very useful in keeping track of things. (Indeed, a few
years ago I posted a message here suggesting it be used to keep track
of friends at Oshkosh, since the unit is small enough to put in your
pocket.)

On the ground, hams have covered the nation with receiving stations
tuned to the frequency used for automatic position reporting. Connect
a computer to a suitable radio, load the free software, and you can
track your friends -- or your cars, airplanes or whatever -- on a
nifty moving map display. It doesn't have to be a big computer --
there's software available for those palm-sized units.

'Tiny Trak' is one such unit and there's a Google group devoted to
automatic position reporting.

-R.S.Hoover
-(KA6HZF)