Hi All, I have a ublox ZED-F9T with a very short RF trace to an SMA connector (< 1cm), so I expect the delay due to the RF line to be in the ~100's pico sec range. Using a GNSS simulator I measure the average 1pps delay relative to the simulator to be about 25ns. This figure is quite close to a typical GNSS SAW group delay. My question is if anyone has done something similar or knows what the actual delay is for a ZED-F9T module. Thanks Fred

Hi Fred, there are three things to consider: 1) alignment of the 1PPS from your GNSS simulator to the simulator’s RF output. GNSS simulators are typically aligned to L1 C/A signal with different level of accuracy. 2) 1PPS cable delays, and 1PPS measurement threshold - those can influence your absolute 1PPS offset from GNSS simulator. 3) ZED-F9T module carrier board. I am assuming you have ZED-F9T module soldered on something. Even though ZED-F9T may have been calibrated in production, as soon as it undergoes solder heating cycle, this can easily shift the group delay of internal components of ZED-F9T. I think best way to go around this is to calibrate 1PPS output against good GNSS simulator after the ZED-F9T is soldered on the PCB. No more solder heat cycles after calibration! Best regards Zdenek > On 29 Apr 2024, at 11:36, rf lab via time-nuts <time-nuts@lists.febo.com> wrote: > > Hi All, > > I have a ublox ZED-F9T with a very short RF trace to an SMA connector (< > 1cm), so I expect the delay due to the RF line to be in the ~100's pico sec > range. Using a GNSS simulator I measure the average 1pps delay relative to > the simulator to be about 25ns. This figure is quite close to a typical > GNSS SAW group delay. > > My question is if anyone has done something similar or knows what the > actual delay is for a ZED-F9T module. > > Thanks > Fred > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hi Unfortunately, the group delay of the typical SAW(s) varies a bit from part to part and across the passband of the SAW(s). Indeed, what you are seeing is “in the ballpark” ( = 10 to 40 ns) for this sort of thing. Why SAW plural? In a multi-band design they just might have one for each band …. Bob > On Apr 29, 2024, at 6:36 AM, rf lab via time-nuts <time-nuts@lists.febo.com> wrote: > > Hi All, > > I have a ublox ZED-F9T with a very short RF trace to an SMA connector (< > 1cm), so I expect the delay due to the RF line to be in the ~100's pico sec > range. Using a GNSS simulator I measure the average 1pps delay relative to > the simulator to be about 25ns. This figure is quite close to a typical > GNSS SAW group delay. > > My question is if anyone has done something similar or knows what the > actual delay is for a ZED-F9T module. > > Thanks > Fred > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com