[time-nuts] GNSS Disciplined Clock

Bob kb8tq kb8tq at n1k.org
Thu May 25 11:56:01 EDT 2017


I don’t speak for Trimble and their interpretation of all this may be a bit unique. Normally 
what the 15 ns means is the time out of a simulator compared to the 1 pps out of the module. 
Put another way, it’s just a measure of the receiver. It does not include any ionosphere / troposphere 
issues. It assumes a perfect estimate of the location (no bias from antenna multipath). IT also 
does not take into account any delay in the antenna or coax to the antenna. Time errors between
Glonass and GPS are not included (bad broadcast offset estimate etc).  Finally there is the
fairly important qualifier of “one sigma” on the 15 ns number. 

All that said, two devices with the same antennas, same cables, close to each other, looking at the
same sats, using the same systems, … should track pretty well. 


> On May 25, 2017, at 9:27 AM, Ebrahim Roghanizad <e.roghanizad at gmail.com> wrote:
> Dear members
> I am a new amateur member in your group. Maybe my question has been asked.
> Recently I found Trimble Mini-T GG, whose data sheet is attached, as a good
> GNSS disciplined time reference. I would like to know if there exists a
> more accurate one, since it does not employ dual frequencies to compensate
> ionospheric delay, though it handles both GPS and GLONASS. Besides, could
> anyone guide me about the presented accuracy in the datasheet? There, it is
> stated that "When operating in Over Determined Timing Mode, the accuracy of
> pulse per second (PPS) is within 15 nanoseconds of GNSS/UTC." Does it mean
> that it includes both bias and the noise? In other words, is it true to say
> that "The time-synchronization error between two of them with a long
> distance is less than 2*15 ns"?
> Best Regards
> <Trimble Mini-T GG.pdf>_______________________________________________
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