[time-nuts] Moving GPSDO

Bob Camp kb8tq at n1k.org
Mon Oct 17 13:53:20 EDT 2016


Hi

Survey is pretty much a bad thing while in motion :)

Some (but not all) GPS modules allow you to set up in a “mobile / do not survey” mode. This is one area that the 
newer ( = not 1997 era) devices do much better at. It also is something that SBAS / EGNOS / WAAS may indeed
help you out on. You may be changing *many* settings on the part to make it behave in a mobile setting. There
are a few bugs you just may turn up while doing this ….

Bob


> On Oct 17, 2016, at 1:38 PM, Nick Sayer via time-nuts <time-nuts at febo.com> wrote:
> 
> Speaking for my GPSDOs specifically, you can’t disable the survey mode with the Venus838 receiver (well, you can, but it requires you to talk to the module with SkyTraq’s software, which requires disabling the GPSDO’s controller - possible to do, but annoying). I haven’t attempted to see what it would do if it were moved after the survey is completed (if you move during the survey, then the survey will fail and repeat).
> 
> The older GPSDOs that had PA6H receivers were navigation receivers that didn’t have a survey mode.
> 
> In either case, without a surveyed position, PPS stability will suffer if/when the constellation degrades due to poor reception, which can happen if, say, the unit is in a moving vehicle in interesting terrain. Poor PPS stability will have an impact on the PLL, obviously.
> 
>> On Oct 16, 2016, at 9:19 PM, Joseph Gray <jgray at zianet.com> wrote:
>> 
>> I'm curious to know how accurately a GPSDO will keep its 10 MHz output
>> while moving. No initial survey to set a position would be done. I
>> don't care about the UTC time.
>> 
>> Joe Gray
>> W5JG
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