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

[Bob kb8tq]

Hi

All of the current crop of uBlox modules do the “dither stuff” when you ask them
to generate an output frequency. Indeed pretty much every device on the market
(that is not a GPSDO) does the same thing ( = free running oscillator and hop edges
to get the output).

Bob

> On Sep 21, 2019, at 2:08 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]
> <uBlox_F9T_timeseries.png><uBlox_oadev_tdev.png>_______________________________________________
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