[time-nuts] Re: Ublox M6T -M8T

[Matthias Welwarsky]

Hi Rich,

I'm using a LEA-M8T in a GPSDO project. I've gathered a bit of experience with 
the M8 timing receivers over the past two or three years.

Both timepulse outputs can be programmed to any frequency and duty cycle you 
like, 10kHz is certainly not a problem. However, some things to consider:

Only frequencies that are even multiples of the internal crystal frequency 
(48MHz) are "clean". Everything else is, as Bob puts it, "drop a pulse, add a 
pulse" approximations. However, that's normally easy to filter.

The receiver adjusts the phase of the time signal once every measurement 
interval. That means, you'll typically get a phase jump every one second. You 
can adjust the measurement frequency, 5Hz is certainly possible, maybe more, 
but consult the data sheet on that.

On top, there is the quantization error. The phase of the time signal will be 
off by some 20 nanoseconds against the "true" GNSS time. The error will be 
different for each measurement interval.

If you want to use the time signal as a PLL reference frequency, your loop 
filter will have to be quite narrow to compensate for all these effects.

BR,
Matthias

On Samstag, 28. Mai 2022 19:05:36 CEST R&M Putz via time-nuts wrote:
> Has anyone done anything with the Ublox GPS timing receivers? As it appears
> the Navman with the 10khz outputs seem to be drying up, I'm wondering about
> the Time Pulse 2 output being set to 10 Khz or 100 Khz. Thoughts anyone?
> Rich
> W9ENG
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