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

[Michael Wouters]

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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