Geoff, Thanks a lot for comparing firmwares. That hard information helps tremendously.
Joe Gray W5JG On Tue, Jan 4, 2011 at 8:46 PM, Kiwi Geoff <[email protected]> wrote: > Joseph Gray wrote: >> If I am using the NMEA data (as in the Garmin is the only time >> source), what firmware is recommended by all those using a GPS18x-LVC? > > I thought I would run some tests for you Joe, using Version 3.0 and 3.2 > > Although I myself have run version 3.0 for a number of months (when it > first came out in 2009) without issues, I take note of what Kasper > Pedersen wrote about his experience - so I have now loaded version > 3.2 into my 18x, rather than any newer version (until Garmin fix the > NMEA latency issue). > > I ran my tests for 2 hours each (7,200 one second samples) with GPS > sitting on an inside window sill with a very limited view of the sky, > so my readings should be taken as perhaps worse case rather than from > a perfect view of the sky. The GPS was using 9 - 10 satellites for the > fix solution during the test. > > The RF sensitivity of the 18x is much better than the Garmin 18. > > I measured the time of the "START" character ($) of the $GPRMC > sentence and the "LAST" 0x10 (Linefeed) character, GPS 18x set to > 4800 Baud. > > Following times are in milliseconds from the leading edge of the 1PPS marker. > > Version 3.00 firmware for Garmin 18x > START Min = 365 > START Avg = 427 (N = 7200) > START Max = 499 > LAST Min = 513 > LAST Avg = 576 (N = 7200) > LAST Max = 648 > > Version 3.20 firmware for Garmin 18x > START Min = 370 > START Avg = 433 (N = 7200) > START Max = 518 > LAST Min = 519 > LAST Avg = 582 (N = 7200) > LAST Max= 667 > > So if you use Version 3.20 firmware for the 18x, at 4800 baud the NMEA > RMC sentence will give the time of the current UTC second and will be > received by an average of 582 ms after the leading edge of the 1PPS > transition (with a maximum jitter of plus 85 ms / minus 63 ms). > > From what I have said earlier in the thread, and from tests that > Kasper Pedersen has done, I think we can say that currently version > 3.2 is the "best" version if you want to use the 18x NMEA timestamps > to be given early in the second (rather than much later as per version > 3.3 and 3.5). > > Joe, you can download GPS18xPC_LVC_320.exe from here: > > http://www.gawisp.com/perry/oem_sensor/ > > The above file is identical to the one I downloaded in 2009 from Garmin. > > Hope that helps. > > Regards, Geoff (Christchurch, New Zealand). > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
