[time-nuts] u-Blox ZED-F9T block diagram or timing knowledge available here?

[Bob kb8tq]

Hi

If you go back in the list archives, there is a lot of info on doing this and that with the 
F9P and the F9T. For a while, there was speculation that the price on them would come
down quite a bit. So far that does not seem to be happening. 

Bottom line is that both the F9P and F9T have roughly a +/- 4 ns sawtooth range. The
sawtooth error correction information out of the device will take this down a bit, but not
quite as far as some of us hoped.

Since both devices are dual band, you can easily post process the data against various
services. I put out some plots suggesting a pretty good level of performance doing this. 
(sub nanosecond at short tau). I have not revisited the project since then. 

As far as either device tagging an input to better than 4 ns …not so much. Same thing 
with the PPS doing better than that. 

At the moment, the Furuno modules have the smallest sawtooth window that I know of.

Bob

> On Jan 6, 2020, at 8:56 PM, Tim S <tim.strommen at gmail.com> wrote:
> 
> Hi, first time poster, just getting into the time rabbit-hole.
> 
>    I'm looking at building my own 10MHz double-oven + Rubidium standard
> for home-lab use, and I wanted to investigate GPS disciplining.  I read
> some remarkable work using Jupiter engines and a simple N/1000 and PLL, but
> with those receivers becoming much more outdated and higher precision GPS
> receivers now fairly cheap - I thought I'd try something new from uBlox to
> not repeat prior efforts.  I've gone all through every resource I can find
> online and on the uBlox forums, but there is a general lack of public
> information about the time and clock features of the u-Blox F9 engine.
> 
>    Suffice it to say, there is a section in the integration manual where
> they elude the 1PPS signal is set to the closest one of 1023 edges - which
> seems to suggest a possible sawtooth phase noise creation.  Talking with a
> person "clive1" on the uBlox forum it sounds like the internal GPS engine
>>> MAY<< now running at 384MHz there sounds like a possibility to align a
> 1PPS edge to a much finer resolution clock which is closer tied to the GPS
> solution and thus less digital divider phase noise might be possible.
> 
>    Does it sound like I'm way out in left field here?  Anyone have the
> luxury of more insight into the construction of the uBlox F9 GPS engine?  I
> don't mind spending a few grand on some factory new components to get a
> decent 10MHz standard, but I'm less interested in doing so if I'm not going
> to understand what's going on inside.
> 
> Thanks in advance for responses,
> 
> -Tim Strommen
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