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

Steve Noskowicz noskosteve at yahoo.com
Mon Dec 3 18:51:59 UTC 2012


 
 
Thanks, Greg,
  Is the payload similar to CNSP-11 that made it to the Med?

73, Steve, K9DCI 


--- On Mon, 12/3/12, Greg Clark wrote:

 
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 repeated.

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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