[time-nuts] Re: FPGA-based GPS NTP server project

[HÃ¥kan T Johansson]

Hi,

perhaps the uBlox ZED-F9T would be a suitable choice, on a RCB-F9T board?
That looks like 8 ns jitter, and the UBX-TIM-TP message should give the 
sawtooth.

A 0.5 ns sampler I actually have on the FPGA.

Cheers,
HÃ¥kan


On Sun, 12 Feb 2023, Ed Marciniak wrote:

> Your mediatek GPS receiver is probably a really lousy pick for low jitter.
> 
> There are options from Navspark like the NS-T, other receiving chips/modules
> from the same, as well as some uBlox parts that would do better.
> 
> There’s options with under 20ns jitter on those, and if memory serves
> there’s one that’s available that with a good sky view and antenna might be
> more like 8ns jitter.
> 
> Get Outlook for iOS
> 
> ____________________________________________________________________________
> From: Bob kb8tq via time-nuts <time-nuts at lists.febo.com>
> Sent: Saturday, February 11, 2023 4:38:23 PM
> To: Discussion of precise time and frequency measurement
> <time-nuts at lists.febo.com>
> Cc: HÃ¥kan T Johansson <f96hajo at chalmers.se>; Bob kb8tq <kb8tq at n1k.org>
> Subject: [time-nuts] Re: FPGA-based GPS NTP server project  
> Hi
> 
> If you want to get the short term jitter down to around a second or so,
> set it up with a GPS module that puts out a sawtooth correction. You
> also need to get the Arty A7 measuring at the 1 ns level. That’s do-able
> without insane amounts of effort.
> 
> Bob
> 
> > On Feb 11, 2023, at 4:09 AM, HÃ¥kan T Johansson via time-nuts
> <time-nuts at lists.febo.com> wrote:
> >
> >
> > Hi,
> >
> > I have a NTP server project based on a Digilent Arty A7 FPGA board with a
> MediaTek GPS MT3329.  Board-to-board NTP tests over network show about 20 ns
> jitter, with long-term wanders of 100 ns, presumably due to my limited
> sky-view.  More details:
> >
> > http://fy.chalmers.se/~f96hajo/fakernet/board_Arty_A7-35-GPS-NTP.html
> >
> > Cheers,
> > HÃ¥kan
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