[time-nuts] uBlox F9T testing - best settings?

[Michael Wouters]

I have uploaded the paper that appears in the conference proceedings:
http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019_paper.pdf

Cheers
Michael

On Sun, Sep 22, 2019 at 9:49 AM Michael Wouters
<michaeljwouters at gmail.com> wrote:
>
> Hello Anders,
>
> We did some work on single-frequency time-transfer with the F9P earlier this year which we presented at IFCS-EFTF in April.
> http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf
> There's a paper too, which I should upload.
> In short, the F9P is very suitable for code-based time-transfer, and we will be using it , or the F9T, in the next iteration of our time-transfer system.
>
> But, I don't see how you can feed an external 10 MHz and 1 pps to the F9T. There don't appear to be any inputs for this on the chip. The TIMEMARK inputs only seem to be useable for measurements. Have I missed something?
>
> Regards
> Michael
>
> On Sun, 22 Sep 2019 at 12:30 am, Anders Wallin <anders.e.e.wallin at gmail.com> wrote:
>>
>> Hi all, we are testing an uBlox F9T (RCB-F9T timing-board) for the past few
>> days. Small uBlox puck antenna in a not-so-great location.
>> I get an ADEV of 3e-8/tau long-term (see pictures or blog)
>>
>> Through the UART there are lots and lots of settings to tweak with the
>> uBlox software - I am wondering if anyone figured out optimal settings for
>> stationary operation and best stability when the pulse1/pulse2 outputs are
>> configured for 1PPS and 10 MHz. Is it using just GPS (or multi-GNSS?), dual
>> or single-frequency, as the default setting?
>>
>> Also, it seems that on 10MHz there is dithering (8ns granularity?) - is
>> there any simple way to generate a round-number out of the uBlox, and use a
>> (simple) multiply/divide to get dithering-free 10MHz?
>>
>> we made a carrier-board for the RCB-F9T with an USB/UART conversion and
>> buffered dual BNC outputs for pulse1/pulse2 - this might be published
>> later...
>>
>> Further down the road, if the F9T really can do dual-frequency
>> observations, and either the receiver clock 1PPS measured (TICC?) against
>> an external 1PPS, or the entire receiver clocked from external 10M/1PPS -
>> and dual-frequency RINEX generated from this - then there seems to be an
>> obvious opportunity for making a low-cost dual-frequency time-transfer
>> setup? Or am I missing something?
>> PPP with F9T seems to be possible:
>> https://gpsd.gitlab.io/gpsd/ppp-howto.html
>>
>> thanks,
>> Anders
>> board https://www.u-blox.com/en/product/rcb-f9t-timing-board
>> antenna https://www.u-blox.com/en/product/ann-mb-series
>> blog http://www.anderswallin.net/2019/09/ublox-f9t-test/
>>
>> [image: uBlox_oadev_tdev.png]
>> [image: uBlox_F9T_timeseries.png]
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