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

[Ed Marciniak]

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.

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________________________________
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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