[aprssig] K6RPT-12 Balloon Seems To Be Having GPS Problems

Greg Clark k7rkt at bigredbee.com
Mon Dec 3 13:01:26 EST 2012

There is some evidence of the entire system resetting.

take a look back at UTC TIME 13:37:10, and you'll see an altitude reading
of 109373, and note that for the previous 37 minutes or so the lat/lon are

When the firmware powers up, it initializes the altitude to 33,333 meters
(or roughly 109373 feet).  If  the firmware doesn't get a valid set of
coordinates from the GPS, it transmits this altitude along with the last
known good coordinates

Then at time 13:39:02 it gets new coordinates and an altitude of 102174.

This doesn't explain the other behavior that we're seeing now, where a
large percentage of the packets have an altitude way too low.

Greg K7RKT

On Mon, Dec 3, 2012 at 8:13 AM, Stephen H. Smith <wa8lmf2 at aol.com> wrote:

>  On 12/3/2012 10:38 AM, Greg Clark wrote:
> I don't think it's resetting, I think it's losing lock, or dropping
> intermittently into 2D mode as it gets fewer than 4 satellites.
>  Greg K7RKT
> How could it EVER get fewer than 4 satellites at 100,000 feet?
> It is clearly losing lock, whether from resets, low battery voltage,  RFI
> from the two-meter transmitter when it keys up (crap quarter-wave whip
> without a proper ground plane??), or possibly extreme cold at 100,000 feet.
>    I haven't seen any details on the packaging of the payload.
> .
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