[aprssig] Trackers from Heaven?

[Eric Goforth]

Bob, is that AM & PM EST?

Eric J. Goforth, N6GOF
www.APRSDEPOT.com



-----Original Message-----
From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Robert Bruninga
Sent: Monday, July 30, 2007 11:36 AM
To: 'TAPR APRS Mailing List'
Subject: [aprssig] Trackers from Heaven?

Someone just walked into my office with a NWS Radiosonde they found in a
field.  Talk about TRACKERS from HEAVEN...

The sign on the side says what it is and that it is of NO FURTHER USE.
So therefore its now his.  We opened it up and noticed a GPS patch
antenna and on the other side of the board was a pair of GPS chips in
1.2" square cans.  Also there was anotehr can for the RF transmitter and
a 4 position dip switch and a frequency table.

We hooked up a 9v power supply across the dead battery and it sprang to
life.  Could just barely see it on a spectrum analyzer.  RF power output
is probably about 10 milliwatts or less.  Looked up the battery and it
appears the battery life is designed for about 6 hours.

200 of these are launched every day at 0000 and 1200 UTC by the WX
service and they all fall into someone's backyard every day...  Using HT
Dfing techniques, it should be easy to find these things before the 6
hours is up..

Of course the telemetry format is not APRS, in fact, I think the GPS
chip set only recovers GPS doppler rates and sends those to the ground
for further processing???  but it would be fun for someone to write  a
decoder.  Then all we have to do is HACK the RF oscillator to get it
onto a HAM band and we have a continuous source of GPS trackers for
throw-away events.

I didn't have time to take photos, before the person had to leave, but
having had so much fun chasing the APRS balloon last week, I now realize
that you can chase balloons every day if you simply tune to one of the
frequenceis below, about 3 hours after the NWS launches them at the same
time every day..

400.250
400.625
401.000
401.375
401.750
402.125
402.500
402.875
403.250
403.625
404.000
404.375
404.750
405.125
405.500
405.875

Lets see, 1200 and 0000 UTC is 8 AM and PM, and about perfect for a
quick ballooon chase.  Now to find out our local launch site...

Bob, Wb4APR


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