[aprssig] Ambiguity due to GPS

Scott Miller scott at opentrac.org
Sat Jan 7 14:52:55 EST 2006

> Fortunately for us, not every developer or 
> software/hardware/firmware is
> supplying products capable of transmitting 140 packets per minute.  I
> haven't been able to document any cases where other vendors 
> products produce
> anywhere near the volume of traffic of some OpenTrac users.  Can you?

To get it anywhere close to that rate without modifying the firmware, you
have to put the tracker into diagnostic mode and have it send back-to-back
test packets.  It offers that in addition to the 'send mark', 'send space',
and 'send alternating' test patterns a la TinyTrak3.  Someone did modify the
code to add a sequence number to the test pattern, which happens to be very
useful for quantifying decoding performance since you can see how many
packets you missed.

The 140 packet/minute example I mentioned was a 20 mW transmitter carried on
a few party balloons, solely for the purpose of performance testing.  Try it
with the normal operating firmware and you're not likely to get more than
one packet every second or two, about the same as the TinyTrak.

My point was that the 140 packets/minute I was sending was completely
appropriate for the application.  People use these things for telemetry and
tracking on balloons, race cars, and so.  It's not my place to decide what
rate someone should use for a particular application.


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