Hi all,

We would not claim 100ps (at Fugro), but stick with the sub-ns spec.

We have tested this extensively with a mosaic-T (in devkit format) at NIST as well as PTB in Germany. If you go to the website, there are some links on the end of the page to papers published on this.

We are currently running a measurement campaign with 2 NMIs in Europe and a large telecom provider, results will be showed at IFCS/EFTF in a poster: https://epapers2.org/ifcs-eftf2025/ESR/paper_details.php?paper_id=2108

This will be running the SparkFun GNSSDO and comparing the 1PPS output to an ELSTAB link as well as TWSTFT.

The sub-ns accuracy spec is referenced to the AtomiChron timescale, but later this year we will offer real-time comparison to UTC(NIST) and UTC(PTB) as well. We have commercially contracted equipment installed at both sides with access to both UTC realizations. It definitely is NOT referenced to UTC, as that would be impossible, we won't know UTC today...

I've done a talk on the technology at OCP-TAP call last year: https://www.youtube.com/watch?v=pSnQuAtU8OM

It's alike what the BIPM does with post-processing raw observations, but we do it in real-time.

If any questions, shoot me an email, or continue here for that matter.

Roell.

-----Original Message-----
From: Gary E. Miller via time-nuts time-nuts@lists.febo.com
Sent: Tuesday, 18 March 2025 23:24
To: Poul-Henning Kamp via time-nuts time-nuts@lists.febo.com
Cc: Gary E. Miller gem@rellim.com
Subject: [time-nuts] Re: SparkFun GNSS Disciplined Oscillator

Time-nuts!

UTC(NIST) can vary from UTC(USNO) by more than 5 ns.

https://www.nist.gov/pml/time-and-frequency-division/time-services/nist-usno

So waht does "within 100 ps" mean?

RGDS
GARY

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com  Tel:+1 541 382 8588

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Sean Hollister via time-nuts time-nuts@lists.febo.com writes:

I'm coming at this from the hobbyist perspective, so a $2500 GNSSDO is
interesting to look at for a few minutes and that's it.  There are a few
aspects of it that I'm unhappy about, which are a trend.

I'll second the comments about power consumption.  Coming from the ham
radio 12V world, I always wonder:

• can I power this off a 12V lead acid or LiFePO4 system (you answer
  this as 9-36V, so that's fine)

• what is the current draw (in the 11-14V range, mostly)?  I realize
  that when you have wall power, 200 mA vs 2 A doesn't matter so much,
  but as soon as you start to contemplate hobbyist-scale offgrid
  solar/battery, even 200 mA adds up fast.

I am also surprised not to see NTP mentioned.  I realize this device is
overkill for NTP, but still.

The "trend" comments, including the RTK Express/Facet family.

• specs

  I tend to see specs that look like copies of some manufacture's
  values, and often I don't believe them.  In the RTK line, I see a
  combination of very small numbers for accuracy, "set up your own base
  station", people working in ITRF-based frames.  I would expect
  essentialy no one doing down that path to achieve the claimed
  accuracies, even though they'll have a nice low number coming out of
  the receiver.  For the accuracies claimed, the the F9P not applying
  ANTCAL is a big deal, and there's no help to figure out the
  in-practice average APC/ARP offset as a workaround.  That said, the
  achieved accuracy with a good RTK network (MaCORS run by MassDOT) is
  impressive and a great value for the price.

  The Facet L-band claims 14mm accuracy.  I'm skeptical (vs close
  network solution), and I'd like to see such claims backed up with test
  data of occupying marks with published coordinates.

  The Facet L-band claims 500mm without corrections.  I don't believe
  that either, but maybe that's unfair of me.  With an RTK Express I see
  greater than mater-level wander without RTK.  Either way, it doesn't
  specify CEP vs 95% vs ?.

• subscriptions and leaving out those who don't want them

  The RTK Express kit and the Facet are around $700, and then you pretty
  much only need a pole and a phone to be a data collector and obtain
  RTK network data (for those with RTK network access).  That's a very
  appealing price/performance ratio.

  The Facet L-Band is $1600, $900 more.  I find this surprising, even
  seeing that it includes a 1-year subscription (with additional years
  at $600 each).  It's still a $300 premium for something, and it's not
  clear if it's a hardware addition to the BOM, NRE, or ?.  But, because
  it's offered with and without, it's easy to buy the version without.

  The Facet mosaic is only available in L-Band, for $1500.  It seems
  this is without a subscription.  But I don't want to buy something
  that has cost baked in to enable a subscription I don't want.  Based
  on the F9P Facet, I'd expect Facet mosic non-L-Band to be $1200.

  All of this makes me wonder how much your GNSSDO would/should cost,
  were it not to support Atomichron subscriptions.

  Overall, it feels like you are moving to a position of only intending
  to serve customers who wish to purchase expensive subscriptions.
  Maybe you don't mean that, but that's how it feels as a potential
  repeat customer and someone who gets asked for recommendations (you've
  sold 3 Facets to other people in significant part due to me).

Greg

Hi

I’ve run Atomicron here in the past. I certainly do not have UTC sitting in my basement. However, using the maser as a reference, their “sub ns” claim does indeed appear to be valid. So: valid in what sense? If I compare the Atomicron number to the maser over many days, they both fit together quite well. No not UTC !!!!  Valid simply a source of timing that is stable to < 1 ns. Do I believe it traces to PTB / NIST  pretty darn well? Yes, but that’s not something I’m set up to test here at the < 1 ns level.

Bob