[aprssig] Better of two GPS units for high speed aircraft?

Scott Miller scott at opentrac.org
Mon Jan 21 11:46:45 EST 2008

The old Sony chipset wasn't nearly as good as the newer SiRFstar III, 
but I haven't personally tested either of them at high speeds.  The GPS 
18 does seem to do a pretty good job while spinning and falling, at least.

If you decide to go with the SiRF type, you might want to wait a few 
days - I've got a new 'store brand' model on the way from Taiwan now. 
It's the same as the Progin SGM-208 (SiRFstar III) but with a DB9 wired 
for direct tracker connection and my own logo.  It's slightly larger 
than the Deluo, but has an easier to see LED and has an IPX7 rating - 
doesn't mind being immersed in water for days at a time.  It'll probably 
sell for a bit less than the old Sony type.

If you were running a Tracker2, it should be possible to use two 
receivers, one configured in Garmin binary mode and the other in NMEA 
mode, on opposite sides of the plane.  I haven't tested it for that kind 
of rapid switching, but in theory it ought to prefer one and switch to 
the other if it loses lock.  I set it up that way so you could run a 
permanently-installed NMEA tracker and still hook up a handheld or 
dash-mounted Garmin without reconfiguring anything.  I never thought 
about the failover aspect, but it'd be interesting to try.


Kriss A Kliegle wrote:
> I was testing my Deluo GPS with laptop and Opentracker while on my trip 
> the other day and found that that GPS unit (not the Deluo Universal GPS 
> PRO SiRF Star III that N1VG currently is selling but previous model) 
> will not re-establish its position while under motion faster than 250 
> kts. Due to ATC, we had to make some +90 degree turns and once it lost 
> it's GPS lock, it would never come back until our speed was reduced. 
> either for landing or holding over central MI. Anybody have experience 
> w/the Garmin -18 or the newer Deluo unit he's selling now with aquiring 
> SATs while under motion. I've noticed the same unit in all my vehicles 
> takes several minutes (even at automobile speeds) to lock on after 
> powering up. The GPS unit is placed in a large, unheated side window of 
> the flightdeck, and can only see 1/2 the sky at a time in level flight. 
> Steep turns to left typically cause it to unlock.
> Anybody???
> Kriss KA1GJU
> KA1GJU-6
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