[time-nuts] adafruit $40 GPS

Kasper Pedersen time-nuts at kasperkp.dk
Tue May 14 14:58:47 EDT 2013

On 05/14/2013 07:57 PM, George Lu wrote:
> According to the documentation at
> http://www.adafruit.com/datasheets/GlobalTop-FGPMMOPA6H-Datasheet-V0A.pdf:
> High accuracy 1-PPS timing support for Timing Appli
> cations (10ns jitter)
> George

Here, have some data.

I am testing a few MT3339 modules at the moment; They all seem to have
the same firmware. The (live, updates every minute) plots of one are at

http://cm.kasperkp.dk/mc1010p.png  (phase)
http://cm.kasperkp.dk/mc1010a.png  (adev of this and others)
http://cm.kasperkp.dk/mc1010p.txt  (pps phase in seconds)

It is far better than others cheap navigation receivers I have tested,
but it does peculiar things sometimes, such as the 60ns excursion at
2500 seconds.

And I am looking for a navigation receiver at the moment, not a timing
one, so this is just because I can.

/Kasper Pedersen

The receiver is fed off of a splitter from an external antenna.
The counter is one of my homebrew ones with ~250ps-ish resolution, and
the FEI-5680A in it was turned on 15 mins before starting the run, so
it's still settling.

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