Hi

There are a number of threads on the uBlox receivers.

Quick summary: All of the outputs from the typical examples are run
with a “drop a pulse / add a pulse” approach to steer them to the
correct frequency. If you are after a “clean” output for some sort of
gear (like a synthesizer) … not so much. If further division for a timing
process, they may be useful.

The drop / add happens on a second to second basis. You get a
“step” in the process each time a PPS “happens”. This results in
a bit of excitement when trying to measure just how good (or bad)
the output is.

Bob

Rich, stand by.  I've been doing a lot of testing with higher-speed
pulserates on the u-blox F9T/M8T/M9N (as high as 20+ MHz) and will be
ready to report some results in a week or two, I hope.  There are some
interesting findings.

And that testing underlies a new TAPR project I'm working on; I hope to
announce that before the end of the summer.

John

On 5/28/22 13:05, R&M Putz via time-nuts wrote:

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:

Yes, we did,

and learned, that the device -- the ublox6 --  forgets the the program
very fast, thus we added one arduino, which loads the program into the
ublox at every new turn on. By using low output frequency -- 10kHz --
the jitter is low, at higher output frequency the jitter is getting
larger, presumably because the internal clock of the ublox is a "free
running " crystal oscillator.
We did not do any "deep quality investigation" to the output of our
10MHz signal source output, 10 is just used as frequency calibrator for
instruments.
I made one phase phase comparation, --comparator one input  GPS -ublox
derived 60kHz the other input is wwvb 60kHz from Fort Collins Colorado,
it show the typical phase change during the day of the wwvb.

73

Alexander Pummer[hard ware] + David Fannin [soft ware]

On 5/28/2022 10:05 AM, R&M Putz via time-nuts wrote:

Do you mean "even submultiples"?  ie. even division ratios.

Andy
www.g4jnt.com

On Sat, 28 May 2022 at 21:11, Matthias Welwarsky via time-nuts <
time-nuts@lists.febo.com> wrote:

I just come accross this application note directly from u-blox.
https://content.u-blox.com/sites/default/files/products/documents/Timing_AppNote_%28GPS.G6-X-11007%29.pdf https://content.u-blox.com/sites/default/files/products/documents/Timing_AppNote_(GPS.G6-X-11007).pdf
They evaluated 8 kHz output.
https://content.u-blox.com/sites/default/files/products/documents/Timing_AppNote_(GPS.G6-X-11007).pdf
.md