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

[Anders Wallin]

Hi Michael, thanks for the reminder about your slides!
Your page 4 has the two setups. I think you are right in that the F9T
doesn't seem to take an external receiver clock (even if working with the
bare part, not the RCB-board).
(FWIW, AFAIK the not-so-low-cost septentrios use the left external receiver
clock scheme, while Dicom GTRs use the right - both in the 15k cost range)

Did you use an external TIC (like the TICC?) - to get lower than the 8ns
granularity of the TIMEMARK?

If I understand CGGTTS the TIC and sawtooth-correction are used to provide
one single time-offset value into the CGGTTS file, for each 780s=13 min
satellite track observed?
https://tycho.usno.navy.mil/cggtts.html
is that correct?
Can the same TIC-based sawtooth correction work for 30s RINEX data instead?
If gpsd can produce dual-frequency RINEX from the F9T, then the new
(software)part needed is the sawtooth-correction at 30s intervals applied
to the raw RINEX from the F9T.
https://gpsd.gitlab.io/gpsd/ppp-howto.html

Anders



On Sun, Sep 22, 2019 at 3:00 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
>
> > 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
>
>