[time-nuts] Re: Phase coherence with 2x GPSDO

[Michael Wouters]

Dear Krishna

You should probably check with the manufacturer exactly how one should
interpret  eg SYNC:FEE?
The manual says:
"This query returns the Frequency Error Estimate."
but is this a offset due to eg a DAC resolution limitation, or is it
the uncertainty in the frequency?
I am guessing it is the latter.

Regards

On Mon, Mar 7, 2022 at 5:01 AM Krishna Makhija  wrote:
>
> Hello,
>
> I am new to the whole precision time-keeping game (and to this mailing
> list) so I apologize in advance if my question is too naive or has been
> answered already in your mailing list.
>
> Is it possible to have two separate GPSDOs, each with their own antennas,
> be phase coherent to each other? I have a Jackson-Labs Fury
>  and a Mini-JLT
> . I am using each to
> provide a 10 MHz reference to two separate software-defined radios (SDRs).
> In my tests I find that the phase offset between said SDRs has a slow
> time-varying behavior. I know the frequency errors of the GPSDOs are of the
> order of parts per trillion which will show up as slow time-varying phase
> offsets but I was hoping to use the PPS offsets and instantaneous frequency
> errors that I get from these modules (using SCPI commands) to be able to
> "back out" or predict what that time-varying phase offset would be. Is such
> a thing possible? Currently, the time-varying phase change does not seem to
> follow any discernible pattern and my attempts at backing out the phase
> change do not match my measurements.
>
> Here is the math I am using for calculating what I *think *the phase
> *should* be:
> [image: image.png]
> [image: image.png]
>
> [image: image.png]
> Does any of this seem sensible? Any input is appreciated.
>
> TL;DR: Trying to get phase coherence between two separate GPSDOs may not be
> possible but can you use PPS offsets and frequency errors metadata to
> correct for it in post?
>
> Regards,
> Krishna
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[time-nuts] Re: Long term ADEV of 5071

[Michael Wouters]

Dear Attila

We have clock comparison data going back 25 years so you could DIY.
But I thought I sent that to you a couple of years ago?

Cheers
Michael

On Fri, 26 Mar 2021 at 3:34 am, Attila Kinali  wrote:

> Moin,
>
> Does someone of those who own a 5071 have long-term ADEV data?
> I'm looking for multi-year data. While there are plenty of ADEV
> plots online, most of them stop at 1Ms or even at 100ks.
>
> Background: I'm involved in a project where long term frequency
> stability is important. And I need some rule of thumb to evaluate
> whether what we are trying to do makes sense or not.
>
> Thanks in advance!
>
> Attila Kinali
>
> --
> The driving force behind research is the question: "Why?"
> There are things we don't understand and things we always
> wonder about. And that's why we do research.
> -- Kobayashi Makoto
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Re: [time-nuts] U-blox teaser

[Michael Wouters]

Typical L1 antenna delays range from 20 to 70 ns.
I know of only one antenna for which a delay is given by the vendor and the
technique used was just to measure the electronic delay ie by injecting a
signal into the circuit. To do it properly, you need a setup in a microwave
anechoic chamber with transmitting antenna etc. The practical difference
may be small though, 1 or 2 ns ( sample of one antenna!).

Cheers
Michael

On Sat, 27 Feb 2021 at 11:42 am, John Ackermann N8UR  wrote:

> They're claiming "even better than" 5 ns for relative time, which given
> the 4 ns jitter seems at least sort-of reasonable.  But until someone
> shows me otherwise, I'm still thinking that getting better than 25 ns
> absolute accuracy is a pretty good day's work.
>
> John
> 
>
> On 2/26/21 5:26 PM, Bob kb8tq wrote:
> > Hi
> >
> > I can’t think of many antennas (multi band or single band) that claim to
> know their
> > delay to < 5 ns. Simply having a *differential* delay spec of < 5 ns is
> quite good.
> > Same thing with delay ripple, you see specs out to around 15 ns on a lot
> of antennas.
> > None of this is getting you to the actual total delay of the antenna.
> It’s a pretty good
> > bet that number is a bit larger than either of these.
> >
> > Some of the ripple probably comes out in the standard modeling. I’m not
> sure that
> > the differential delay is taken out that way. Total delay, not taken out
> in any obvious
> > fashion ( at least that I can see). If the F9 has a built in antenna
> database, that’s not
> > mentioned in the doc’s. Any benefit from the corrections would have to
> be part of
> > post processing.
> >
> > No, that’s not the same as talking about the F9 it’s self doing X ns,
> but it would be part
> > of any practical system trying to get close to 5 ns absolute accuracy.
> >
> > 5 ns *relative* accuracy between two F9’s? I probably could buy that if
> the appropriate
> > one sigma / on a clear day / with the wind in the right direction sort
> of qualifiers are
> > attached.
> >
> > Bob
> >
> >> On Feb 26, 2021, at 4:27 PM, John Ackermann N8UR  wrote:
> >>
> >> It's interesting that they talk about the F9 receivers offering 5 ns
> absolute time accuracy.  Does anyone know of tests confirming that, and
> what sort of care was required in the setup to get there?
> >>
> >> John
> >> 
> >>
> >> On 2/26/21 9:34 AM, Robert LaJeunesse wrote:
> >>> FWIW. No detailed content, and a rather quick read. "Five key trends
> in GPS".
> >>> https://www.u-blox.com/en/blogs/insights/five-key-trends-gps
> >>> ___
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Re: [time-nuts] Long Wave Radio-Frequency standard testing

[Michael Wouters]

Hello Gilles

There's a reasonable way of treating data with gaps in it:

https://iopscience.iop.org/article/10.1088/0026-1394/45/6/S19

Essentially, any averaging interval with missing data is dropped from
the ADEV summation.
This reduces the number of intervals averaged over and increases the
uncertainty but is better than faking data.

Stable32 provides an  implementation of the algorithm. See p18 of the manual.

Cheers
Michael




On Tue, Jan 19, 2021 at 6:18 PM Gilles Clement  wrote:
>
> Hi,
> Yes outliers removal creates gap in Stable32.
> The « fill »  function can fills gaps with interpolated values.
> It does not change much the graphs, except in the low Tau area (see attached).
> Do you know a discussion of impact of outliers removal ?
> Gilles.
>
>
>
> > Le 18 janv. 2021 à 22:06, Bob kb8tq  a écrit :
> >
> > Hi
> >
> > As you throw away samples that are far off the mean, you reduce the sample
> > rate ( or at least create gaps in the record). Dealing with that could be 
> > difficult.
> >
> > Bob
> >
> >> On Jan 18, 2021, at 1:33 PM, Gilles Clement  wrote:
> >>
> >>> Hi
> >>>
> >>> Very cool !!!
> >>>
> >>> The red trace is obviously the one to focus on. Some sort of digital loop 
> >>> that
> >>> only operates under the “known good” conditions would seem to make sense.
> >>>
> >>> Thanks for sharing
> >>>
> >>> Bob
> >>
> >> Hi,
> >> I tried something with the idea to consider night records fluctuations as 
> >> « outliers » as compared to day records.
> >> Indeed the 3 days record mean value is flat and the histogram quite 
> >> gaussian.
> >> So I processed the 3 days record (green trace) with Stable32’s « Check 
> >> Function »,
> >> while removing outliers with decreasing values of the Sigma Factor. The 
> >> graph below shows the outcome.
> >> The graph with Sigma=0.8 (blue trace) connects rather well with the 1Day 
> >> record (red trace).
> >> Would this be a workable approach ?
> >> Best,
> >> Gilles.
> >>
> >>
> >>
> >>
> >>
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Re: [time-nuts] Query about insulated coax panel connectors?

[Michael Wouters]

Dear Jim

These, in conjunction with some M6 nylon washers, work OK for
isolating an SMA bulkhead feedthrough from the case:
https://www.minikits.com.au/components/hardware/washers/Metric-M6-Washers
(the nylon shoulder washers down the bottom)
The connector will rotate though if you try to torque up the SMA nut -
you can really only make them finger tight.

Otherwise, you can buy isolated bulkhead feedthroughs eg
https://www.fccable.com/SMA-Female-To-SMA-Female-Bulkhead-Isolated-Ground-Adapter/2068/A1636/
or
https://www.centricrf.com/adapters/sma-adapters/sma-to-sma-bulkhead-adapters-18ghz/c3150b-sma-f-f-isolated-ground-bulkhead-adapter/
I never found anything cheaper than about $US20 per connector.

Cheers
Michael


On Sun, Oct 25, 2020 at 7:44 AM AC0XU (Jim)  wrote:
>
> Time-nuts:
>
> Having recently run into major ground loop noise issues, I have begun 
> reworking some of my homemade pieces of equipment using insulated coax 
> connectors. My goal is to have one ground connection only in the cases, and 
> that is at the power entry point, either a power cord or the outer terminal 
> of a DIN. I am also installing isolation baluns on inputs and/or outputs.
>
> Insulated BNCs are readily available. Others not so. In some cases, there is 
> not room to install an insulated BNC. I am not finding any insulated SMA, 
> SMC,  SSMA, or SSMC despite googling and searching catalogs.
>
> Does anyone know of a source for insulated small threaded coax panel 
> connectors?
>
> Another option would be a compact insulating bushing that an SMA panel 
> connector, for example, could be mounted in. I am not finding anything like 
> that either...  In fact the ideal solution would be an insulated SMA with an 
> integrated 1:1 balun.
>
> And I am not thinking about using plastic cases - that would introduce a 
> whole other set of problems. I think about my lab area at work where a bundle 
> of dozens of gigabit ethernet cables run through the roof directly over the 
> lab bench - the ambient noise level is quite high.
>
> Suggestions???
>
> The only idea I have some up with is to design something myself, possibly 3-D 
> printed...  Any suggestions about how to get started on something like that?
>
> Thanks in advance-
> Jim
>
>
>
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Re: [time-nuts] xDEV "spread" on parts of data

[Michael Wouters]

Hello Ole

Have you looked at dynamic Allan variance ? Patrizia Tavella wrote a few
papers about this.

Cheers
Michael

On Wed, 16 Sep 2020 at 7:28 pm, Ole Petter Ronningen 
wrote:

> Hi, All
>
>
>
> I am currently working on some lather long time-series, and I find myself a
>
> little unsure of how to present the data. I've attached a TDEV plot below
>
> (that I hope makes it through) for illustration purposes, but the same
>
> dilemma holds for ADEV/MDEV etc. It concerns how instability is averaged
>
> out on long data series.
>
>
>
> The pink line below is the TDEV of the whole series and represents about 14
>
> days of data. The blue lines are generated by using the "trace history"
>
> facility in TimeLab, each line representing roughly 12-hour "chunks" of the
>
> same data.
>
>
>
> It can be seen that some of the blue plots are "worse" than the pink plot -
>
> not only at the tail end, where it might be expected but also at short tau.
>
> The implications are of course that there are stretches of data where the
>
> TDEV is better/worse than others, but it is also clear that the TDEV plot
>
> of the whole data in some sense masks this.
>
>
>
>  ADEV/TDEV/MDEV is what it is, and that is fine - but this is still
>
> information that is relevant when looking at the plot. The question at hand
>
> is how to convey this information in an accurate way? The error bars are
>
> really no help.
>
>
>
> Some kind of "min/max TDEV per tau displayed as error bars" comes to mind,
>
> but there are a number of issues with that approach.
>
>
>
> I am also hoping that perhaps this has been thought of before - is there
>
> some "standard" (or even good, or half-decent) way of calculating/showing
>
> this "spread of xDEV"?
>
>
>
> Thank you all,
>
> Ole
>
>
>
>
>
> [image: image.png]
>
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Re: [time-nuts] Satelles PNT from Iridium satellites

[Michael Wouters]

Dear Tom,

A one year, single device licence to access the signal cost about AUD10K
 when I asked about a year ago. The plugin card for a commercial timing box
was about AUD3K.

Cheers
Michael

On Mon, 10 Aug 2020 at 9:05 am, Tom Van Baak  wrote:

> Hi Stu,
>
> There's no problem with a semi-commercial posting here. You've been a
> member for a decade and frequent contributor plus the subject matter is
> exactly on-topic. So thanks for posting.
>
> I spent a while on your web site and didn't uncover a trove of white
> papers. If you could post some URL's that would be appreciated. You
> don't have to worry about being less accurate than GPS. I mean, there
> are often far more important factors than nanosecond precision. You
> didn't mention pricing; it's hard to imagine it's as free as GPS so that
> seems like another disadvantage to me.
>
> Your comment about fewer satellites is spot on. That will be taken care
> of if you give SpaceX / Starlink a call and join that bandwagon. There
> are already 597 Starlink [1] satellites up there vs. 82 Iridium [2]
> satellites, yes?
>
> If you have entry-level / hobbyist grade evaluation kits I'm sure a
> number of us would be very interested to try it out.
>
> Thanks,
> /tvb
>
> [1] https://en.wikipedia.org/wiki/Starlink
>
> [2] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
>
>
> On 8/9/2020 2:53 PM, Stewart Cobb wrote:
> > Taka Kamiya and Forrest Christian both asked recently about the
> alternative
> > satellite PNT system using the Iridium satellites. That system was
> > developed by my company, Satelles. It has been commercially available for
> > more than a year now.
> >
> > The biggest advantage is that our signal is at least 30 dB stronger than
> > GNSS signals (the exact numbers depend on whether you're talking to
> > engineering or marketing :). You can easily get a usable signal in deep
> > jungle, or a data center in the middle of a building's basement, or even
> > inside a locked shipping container. The stronger signal is
> correspondingly
> > more difficult to jam or spoof than GNSS, and our signal has
> anti-spoofing
> > features as well.
> >
> > The biggest disadvantage is that it is not quite as accurate as GPS,
> > because there are fewer satellites in view at any given time.
> >
> > I don't want to quote exact timing numbers here, because they depend a
> lot
> > on system integration details, but you can easily steer an OCXO within a
> > few hundred nanoseconds of USNO time. With a rubidium, you can do
> > considerably better.
> >
> > If you want to know more, our website is www.satellesinc.com.
> >
> > (If this message has been too commercial, I apologize in advance. The
> > boundary between information and salesmanship is not always sharp.)
> >
> > Cheers!
> > --Stu
> > ___
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Re: [time-nuts] Vibration isolation of quartz oscillators

[Michael Wouters]

Hello Tom,
(and thanks everyone for your advice)
I want to do the same as you: rack mount the oscillators. Elaborate
vibration isolation solutions are not possible in the available space viz 3
to 4 RU.


I have the manufacturer’s test data for the oscillators, plus my own test
data, so I think I will just make a trial test with the existing isolation
system and then see if there any problems when in the rack.


Cheers
Michael

On Tue, 30 Jun 2020 at 2:52 am, Tom Knox  wrote:

> I am enjoy this Nth degree Vibration Isolation discussion. Countless
> amazing tables where I work.
> I have been focused on more practical solutions for Vibration isolation of
> my rack mount oscillators in my home lab, and I think at that level in some
> ways are focused on eliminating resonances as well as trading one frequency
> for another taking higher intensity "square waves" and dissipating them
> over time.
> Any thoughts?
> Cheers;
>
> Tom Knox
>
> SR Test and Measurement Engineer
>
> Ascent Concepts and Technology
> Much
> 4475 Whitney Place
>
> Boulder Colorado 80305
>
> 303-554-0307
>
> act...@hotmail.com
>
> "Peace is not the absence of violence, but the presence of Justice" Both
> MLK and Albert Einstein
>
> 
> From: time-nuts  on behalf of
> Poul-Henning Kamp 
> Sent: Monday, June 29, 2020 12:16 AM
> To: Discussion of precise time and frequency measurement <
> time-nuts@lists.febo.com>; ed breya 
> Subject: Re: [time-nuts] Vibration isolation of quartz oscillators
>
> 
> ed breya writes:
>
> > The nicest optical bench I've ever seen in person, was in one of our
> > labs many years ago. It was a huge, precisely flat polished granite slab
> > about 6-8" thick, about 4x8' or maybe 5x10', mounted on active-leveling
> > pneumatic bladders. It was loaded with thousands of threaded inserts,
> > uniformly spaced on a grid, for mounting optical devices and equipment.
>
> It is worth foot-noting here, that at that level of quality they
> are usually not made from natural granite, but rather from
> "epoxy-granite", which can be designed to have very low temp-co.
>
> > There are lower-grade type platforms available, commonly called "optical
> > breadboards," that are made from thick sheets of aluminum or stainless
> > steel, [...]
>
> and these obviously have a sizeable temp-co, so the money you saved on
> your bench you get to spend on your air-con.
>
> They are a lot easier to move around though.
>
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
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[time-nuts] Vibration isolation of quartz oscillators

[Michael Wouters]

I have three Oscilloquartz 8607-Bs that I'm rehousing.

In their former life they were part of the frequency synthesis chains
for H-masers and they hung vertically from a rubber suspension that was
presumably intended to provide vibration isolation. Unfortunately, the
person responsible for this has long since retired so is no longer
around to ask questions of.

In the experiment I will be averaging over  100 s, which suggests to
me that very low frequencies are what I need to filter out (if at
all), and I am skeptical that the rubber will do this. Space is tight
so I am wondering
whether I should simply ditch the isolation.

What do other people do with their quartzes ? I thought I should ask
for some advice before attempting measurements.

Cheers
Michael

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Re: [time-nuts] What’s the BEST crystal?

[Michael Wouters]

Hello Jim

>How does a CSO compare with a Mercury Ion clock - the latter does fit in
>a satellite and is intended to replace the USO kind of function.


The current CSOs can be surprisingly compact. I was visiting a university
colleague who had recently bought one from Cryoclock for use in quantum
computing experiments. The total package was about half a rack. One big
improvement has been moving to a closed cycle cooling system. It’s
difficult imagining it going into a spacecraft or satellite though.

Cheers
Michael

On Mon, 2 Mar 2020 at 2:40 am, jimlux  wrote:

> On 2/29/20 2:47 PM, Attila Kinali wrote:
> > On Sat, 29 Feb 2020 17:01:27 -0500
> > Bob kb8tq  wrote:
> >
> >>> Isn't that where "whispering gallery" modes come into the picture ?
> >>
> >> …… and done with sapphire.
> >>
> >> This is the real answer to “why is nobody going to do this?”. You
> already
> >> have something ( the sapphire resonators ) that does better than
> >> anything you could reasonably expect.
> >
> > It's the other way round. Yes, we have *a* solution for better phase
> noise
> > and stability, but not *the* solution. A CSO is a full size 19" rack
> > filled with equipment that needs constant maintenance. Nothing you can
> > put on a satellite, much less carry around. People wouldn't even put it
> > in cellphone base station, although they would love to have the
> additional
> > frequency stability and phase noise performance to squeeze in some
> > more customers into the limited frequency space.
>
>
> How does a CSO compare with a Mercury Ion clock - the latter does fit in
> a satellite and is intended to replace the USO kind of function.
>
> >
> > It is actually very hard to beat crystal oscillators and vapor cell
> > frequency standards in the stability/phase noise/size/power
> consumption/cost
> > trade-off. And until recently, quartz oscillators and vapor phase
> > standards occupied seperate areas in this trade-off space. Until the
> > CSAC came around and connected them.
> >
> >
> >   Attila Kinali
> >
>
>
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Re: [time-nuts] u-Blox ZED-F9T block diagram or timing knowledge available here?

[Michael Wouters]

Hello Tim,

There’s a TDEV plot here:
http://www.openttp.org/scripts/blog.php
PPS measurements were post -processed using the sawtooth corrections.

Cheers
Michael


On Tue, 7 Jan 2020 at 1:07 pm, Tim S  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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Re: [time-nuts] Cold Rubidium over hyped?

[Michael Wouters]

I think you are missing the key selling point of this device, namely
it's long term stability and accuracy of a few parts in 10^15. From my
point of view as a national timekeeper, this is much more useful than
good short term stability. UTC reporting is at 5 day intervals so what
the clock does at 1000 s is not so important. By the way, there is
another comparison with 12 NIST masers in the current brochure:
https://spectradynamics.com/product-sheets/cRb-Clock-2019.pdf
There are evidently two models of maser here ,which politely, they do
not identify.

Cheers
Michael

On Sat, Nov 9, 2019 at 11:00 AM  wrote:
>
> Well I have been looking at the data in the
>
> https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_
> atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range
>
> link and find that maybe they are overstating their performance!
>
> In the plot of figure 5 my HP 5065A almost perfectly matches the Allan
> deviation
> out to 1000 Sec.! (Although mine does have VERY good performance)
>
> Also if you look at figure 7 all the Maser data shown seems to be from
> poorly
> operating Masers so any judgement of better clock performance versus the
> Masers
> is a bit much!
>
> The figure 5 data looks much better but still is not beating a good
> active Maser.
>
> The EFOS2 a 1982 vintage Maser as well as the MHM 2010 and several other
> modern Masers
> I could find data for show between 2 and 5X10-15th at 1000 Sec.
> The MHM 2010 specs at 5X10-15th at 100Sec and 2.0X10-15th at 1000Sec
> All the Masers shown are worse than that spec!
> Also my old Kvarz passive maser has  2x10-13th at 100 Sec just shy of
> matching the top two Masers at 100Sec, which I don't believe!
>
> Something does not add up in their data!
>
> So I'm not really that impressed and would take an Active or Passive
> Maser anyday.
>
> Just wonder if some  5065A can get so impressive that they don't just
> make a modern large/cool cell classic Rubidium with modern electronics
> technology! Certainly would be cheaper and more long lived also.
>
> Just my thoughts!
>
> Cheers,
>
> Corby
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Re: [time-nuts] Cold Rubidium?

[Michael Wouters]

The atoms are laser cooled and held in a magneto-optical trap. It’s
basically a short, one-way fountain.

Cooling the microwave cavity would be useful for reducing the black body
radiation shift, but without checking the numbers, this would not be so
useful at the relatively low accuracy claimed for the clock. Otherwise,
it’s pretty much irrelevant to the atom temperature. It’s all UHV, so
there’s no time to come to thermal equilibrium with whatever residual gas
is in the vacuum enclosure.

NIST used to operate a mercury ion microwave clock at cryogenic
temperatures.

Cheers
Michael

On Sun, 27 Oct 2019 at 8:01 am, Dana Whitlow  wrote:

> I can only answer one of your questions with any confidence, but I'd
> suspect that the
> chamber walls are cooled a fair bit in addition to being highly
> reflective.  Your other
> questions age very good ones, too, and I'm looking forward to *somebody*
> answering
> them.  I'd also love to hear the details of how they go about interrogating
> that cloud of
> cold Rb atoms in such a short time (< 100 msec).
>
> Dana
>
>
> On Sat, Oct 26, 2019 at 3:01 PM Richard (Rick) Karlquist <
> rich...@karlquist.com> wrote:
>
> > The proverbial "dumb questions":
> >
> > Is there an actual refrigerator somewhere
> > in this gadget, or are the Rb atoms in a
> > room temperature vacuum and the laser cools
> > just the atoms.  It appears to be the latter.
> >
> > So the enclosure has low emissivity so it
> > doesn't transfer too much heat to the atoms
> > by radiation?
> >
> > And is it correct that the atoms are not ionized
> > to trap them because the laser does that?
> >
> > Rick N6RK
> >
> > On 10/26/2019 1:39 AM, Anders Wallin wrote:
> > > ptti2018:
> > >
> >
> https://www.researchgate.net/publication/322920519_Long_term_frequency_instability_of_a_portable_cold_87Rb_atomic_clock
> > > ifcs2018:
> > >
> >
> https://www.researchgate.net/publication/325499937_A_portable_cold_87_Rb_atomic_clock_with_frequency_instability_at_one_day_in_the_10-15_range
> > >
> > > this one is apparently a darpa/spectradynamics/nist effort, and
> there's a
> > > similar story with muquans and syrte in france, see:
> > > https://www.muquans.com/product/muclock/
> > >
> > >
> > > On Fri, Oct 25, 2019 at 11:09 PM AC0XU (Jim) <
> james.schatz...@ac0xu.com>
> > > wrote:
> > >
> > >> Does anyone have any experience/first hand knowledge of this Cold
> > Rubidium
> > >> standard?
> > >>
> > >> 
> > >> https://spectradynamics.com/products/crb-clock/
> > >>
> > >> The specs look very good. The mfr claims that, unlike traditional
> > rubidium
> > >> oscillators, it has no long-term drift.
> > >> Thanks!
> > >> Jim
> > >> ___
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> > >
> >
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Re: [time-nuts] Talking Clock

[Michael Wouters]

Hello Dana

The prototype system I built used an E1 digital telephony card with 30
lines. I think it cost about $12000/year to lease the associated 2
megabits per second data capacity but we didn't do that; we just
commandeered a few lines from our site's capacity.
I believe the live system needed several hundred lines to deal with
peak demand, usually at DST transitions.

Cheers
Michael

On Tue, Oct 1, 2019 at 6:00 PM Dana Whitlow  wrote:
>
> What kind of telephone service would one request for a talking clock, that
> permits a
> large number of users to be listening in at once?  I suspect that this
> would be the real
> difficulty and would incur considerable monthly expense.
>
> Dana
>
>
> On Mon, Sep 30, 2019 at 9:08 PM jimlux  wrote:
>
> > On 9/30/19 3:00 PM, Neville Michie wrote:
> > > Here in Australia we are suffering the loss
> > > of one of the significant developments in accurate time keeping and
> > dissemination.
> > > The talking clock, built in England, with sound tracks on rotating glass
> > disks,
> > > has been on the Australian telephone system for more than half a century.
> > > The system was timed by quartz oscillators, synchronised to the local
> > observatory time.
> > > Now in spite of the trivial cost of maintaining the system it has been
> > removed by
> > > the money-hungry telco which took over the government run telephone
> > system.
> > > Now it occurs to me that the sound tracks occupy a very small digital
> > space, and
> > > with modern flash drives and a little logic the talking clock could be
> > driven by
> > > any time nut's disciplined time source.
> > > So is there a time nut who could design a voice output that we could all
> > use?
> > >
> > > “At the third stroke the time will be…”
> > >
> >
> >
> >
> > using Bash on my mac:
> >
> > $ date +"The time is now, %H, %M, %S, coordinated universal time" | say
> > -v Karen
> >
> > I think that one could do a bit of scripting and have it have your
> > preferred wording, and synchronized to the top of the second.
> >
> > I leave it as an exercise for the reader to do it in French:
> > $ say -v Amelie "Le Temps Universel Coordonné"
> >
> >
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> >
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Re: [time-nuts] Talking Clock

[Michael Wouters]

I designed the hardware and wrote the software for the now defunct
Australian speaking clock.
The prototype pieced together the audio from fragments and it did
indeed take quite a bit of effort to get this to sound clean.
Mismatches in sound levels at the boundaries caused 'pops', for
example. I spent about a week with my headphones on.

Cheers
Michael

On Tue, Oct 1, 2019 at 12:08 PM Bob kb8tq  wrote:
>
> Hi
>
> Based on only dimly remembered conversations long long ago:
>
> Getting all the “message fragments” so they sound natural and not choppy is
> not quite as easy as it seems at first. It’s by not quite rocket science, but 
> there
> is more fiddling involved than one might think.
>
> One “solution” is to use fewer fragments and record larger portions of the 
> message.
> Back in the day, storage limited your ability to record every message “full 
> up”.
>
> Assuming you record the “at the stroke the time will be” only once, the rest 
> is
> under 3 seconds of audio. At maybe 16 bits / 32K sps. (yes that’s overkill). 
> this comes
> up just under 200 K bytes. Recording the full time message for every minute 
> of the
> day would be less than 270 megabytes.
>
> That’s a pretty small flash drive ….
>
> Bob
>
>
>
>
> > On Sep 30, 2019, at 4:00 PM, Neville Michie  wrote:
> >
> > Here in Australia we are suffering the loss
> > of one of the significant developments in accurate time keeping and 
> > dissemination.
> > The talking clock, built in England, with sound tracks on rotating glass 
> > disks,
> > has been on the Australian telephone system for more than half a century.
> > The system was timed by quartz oscillators, synchronised to the local 
> > observatory time.
> > Now in spite of the trivial cost of maintaining the system it has been 
> > removed by
> > the money-hungry telco which took over the government run telephone system.
> > Now it occurs to me that the sound tracks occupy a very small digital 
> > space, and
> > with modern flash drives and a little logic the talking clock could be 
> > driven by
> > any time nut's disciplined time source.
> > So is there a time nut who could design a voice output that we could all 
> > use?
> >
> > “At the third stroke the time will be…”
> >
> > cheers,
> > Neville Michie
> > ___
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>
>
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Re: [time-nuts] uBlox F9T testing - best settings?

[Michael Wouters]

I have uploaded the paper that appears in the conference proceedings:
http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019_paper.pdf

Cheers
Michael

On Sun, Sep 22, 2019 at 9:49 AM Michael Wouters
 wrote:
>
> Hello Anders,
>
> We did some work on single-frequency time-transfer with the F9P earlier this 
> year which we presented at IFCS-EFTF in April.
> http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf
> There's a paper too, which I should upload.
> In short, the F9P is very suitable for code-based time-transfer, and we will 
> be using it , or the F9T, in the next iteration of our time-transfer system.
>
> But, I don't see how you can feed an external 10 MHz and 1 pps to the F9T. 
> There don't appear to be any inputs for this on the chip. The TIMEMARK inputs 
> only seem to be useable for measurements. Have I missed something?
>
> Regards
> Michael
>
> On Sun, 22 Sep 2019 at 12:30 am, Anders Wallin  
> wrote:
>>
>> Hi all, we are testing an uBlox F9T (RCB-F9T timing-board) for the past few
>> days. Small uBlox puck antenna in a not-so-great location.
>> I get an ADEV of 3e-8/tau long-term (see pictures or blog)
>>
>> Through the UART there are lots and lots of settings to tweak with the
>> uBlox software - I am wondering if anyone figured out optimal settings for
>> stationary operation and best stability when the pulse1/pulse2 outputs are
>> configured for 1PPS and 10 MHz. Is it using just GPS (or multi-GNSS?), dual
>> or single-frequency, as the default setting?
>>
>> Also, it seems that on 10MHz there is dithering (8ns granularity?) - is
>> there any simple way to generate a round-number out of the uBlox, and use a
>> (simple) multiply/divide to get dithering-free 10MHz?
>>
>> we made a carrier-board for the RCB-F9T with an USB/UART conversion and
>> buffered dual BNC outputs for pulse1/pulse2 - this might be published
>> later...
>>
>> Further down the road, if the F9T really can do dual-frequency
>> observations, and either the receiver clock 1PPS measured (TICC?) against
>> an external 1PPS, or the entire receiver clocked from external 10M/1PPS -
>> and dual-frequency RINEX generated from this - then there seems to be an
>> obvious opportunity for making a low-cost dual-frequency time-transfer
>> setup? Or am I missing something?
>> PPP with F9T seems to be possible:
>> https://gpsd.gitlab.io/gpsd/ppp-howto.html
>>
>> thanks,
>> Anders
>> board https://www.u-blox.com/en/product/rcb-f9t-timing-board
>> antenna https://www.u-blox.com/en/product/ann-mb-series
>> blog http://www.anderswallin.net/2019/09/ublox-f9t-test/
>>
>> [image: uBlox_oadev_tdev.png]
>> [image: uBlox_F9T_timeseries.png]
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Re: [time-nuts] uBlox F9T testing - best settings?

[Michael Wouters]

Hello Ragnar

Mktimetx uses the receiver-provided sawtooth correction in the TP message.
The TDEV plots in the presentation I linked show its effectiveness.

Cheers
Michael

On Mon, 23 Sep 2019 at 4:21 pm, Ragnar Sundblad  wrote:

>
> Hello Michael,
>
> > On 22 Sep 2019, at 23:54, Michael Wouters 
> wrote:
> >
> > The OpenTTP software mktimetx applies sawtooth corrections to the TIC
> > measurements, as you guessed. The corrected TIC measurements are combined
> > with the raw GNSS pseudo ranges, and then this is what goes into the
> output
> > RINEX and what is used for CGGTTS generation.
>
> Have you considered using the UBX-TIM-TP qErr correction (the receivers own
> estimate of the quantisation error for the TIMEPULSE output) instead of
> sawtooth filtering?
>
> I have played with it a little on a u-blox M8, and it sure seemed to smooth
> things out, but I haven’t made any real measurements on the result.
>
>
> Anders,
> Thanks for sharing your results! I am a but surprised that you have so
> large
> variations, I wonder how much the antenna placement affects the results.
> Just for fun - can you tell us more about how your antenna is place now?
>
>
> Best regards,
>
> Ragnar
>
>
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Re: [time-nuts] uBlox F9T testing - best settings?

[Michael Wouters]

Hello Peter

The aim of our study was to characterise the performance of single
frequency receivers for time-transfer.  The F9P was a late addition to our
study and extending our software to dual frequency was too much work at the
time. Having a measured ionosphere was not such a huge improvement anyway,
because there are other ways to get an improved ionosphere correction when
post-processing.

Regards
Michael

On Mon, 23 Sep 2019 at 7:03 am, Peter Vince 
wrote:

> Hello Michael,
>
>  Thank you for your Powerpoint presentation slides - if the paper you
> mentioned added some descriptive words, I would love to see that.
>
> Might I ask why you didn't use the F9P in dual-frequency mode, as I
> understood that gives a much better result, being able to (almost?)
> eliminate ionospheric effects?
>
>  Regards,
>
>   Peter
>
>
> On Sun, 22 Sep 2019 at 01:00, Michael Wouters 
> wrote:
> >
> > We did some work on single-frequency time-transfer with the F9P earlier
> > this year which we presented at IFCS-EFTF in April.
> > http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf
> > There's a paper too, which I should upload.
> > In short, the F9P is very suitable for code-based time-transfer, and we
> > will be using it , or the F9T, in the next iteration of our time-transfer
> > system.
> > ...
> > Regards
> > Michael
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Re: [time-nuts] uBlox F9T testing - best settings?

[Michael Wouters]

Hello Anders,
Yes, we used  TAPR TICCs do the testing. It’s a very economical solution
for testing multiple receivers in parallel.

The OpenTTP software mktimetx applies sawtooth corrections to the TIC
measurements, as you guessed. The corrected TIC measurements are combined
with the raw GNSS pseudo ranges, and then this is what goes into the output
RINEX and what is used for CGGTTS generation.

One complication is that the raw pseudo ranges have ms ambiguities in them.
  But mktimetx fixes that.

I’ll put the paper on the openttp website.
Unfortunately, it appears that it will otherwise be behind a paywall.

Cheers
Michael





On Mon, 23 Sep 2019 at 12:00 am, Anders Wallin 
wrote:

> Hi Michael, thanks for the reminder about your slides!
> Your page 4 has the two setups. I think you are right in that the F9T
> doesn't seem to take an external receiver clock (even if working with the
> bare part, not the RCB-board).
> (FWIW, AFAIK the not-so-low-cost septentrios use the left external receiver
> clock scheme, while Dicom GTRs use the right - both in the 15k cost range)
>
> Did you use an external TIC (like the TICC?) - to get lower than the 8ns
> granularity of the TIMEMARK?
>
> If I understand CGGTTS the TIC and sawtooth-correction are used to provide
> one single time-offset value into the CGGTTS file, for each 780s=13 min
> satellite track observed?
> https://tycho.usno.navy.mil/cggtts.html
> is that correct?
> Can the same TIC-based sawtooth correction work for 30s RINEX data instead?
> If gpsd can produce dual-frequency RINEX from the F9T, then the new
> (software)part needed is the sawtooth-correction at 30s intervals applied
> to the raw RINEX from the F9T.
> https://gpsd.gitlab.io/gpsd/ppp-howto.html
>
> Anders
>
>
>
> On Sun, Sep 22, 2019 at 3:00 AM Michael Wouters  >
> wrote:
>
> > Hello Anders,
> >
> > We did some work on single-frequency time-transfer with the F9P earlier
> > this year which we presented at IFCS-EFTF in April.
> > http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf
> > There's a paper too, which I should upload.
> > In short, the F9P is very suitable for code-based time-transfer, and we
> > will be using it , or the F9T, in the next iteration of our time-transfer
> > system.
> >
> > But, I don't see how you can feed an external 10 MHz and 1 pps to the
> F9T.
> > There don't appear to be any inputs for this on the chip. The TIMEMARK
> > inputs only seem to be useable for measurements. Have I missed something?
> >
> > Regards
> > Michael
> >
> > > Further down the road, if the F9T really can do dual-frequency
> > > observations, and either the receiver clock 1PPS measured (TICC?)
> against
> > > an external 1PPS, or the entire receiver clocked from external
> 10M/1PPS -
> > > and dual-frequency RINEX generated from this - then there seems to be
> an
> > > obvious opportunity for making a low-cost dual-frequency time-transfer
> > > setup? Or am I missing something?
> > > PPP with F9T seems to be possible:
> > > https://gpsd.gitlab.io/gpsd/ppp-howto.html
> >
> >
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Re: [time-nuts] uBlox F9T testing - best settings?

[Michael Wouters]

Hello Anders,

We did some work on single-frequency time-transfer with the F9P earlier
this year which we presented at IFCS-EFTF in April.
http://www.openttp.org/downloads/Multi-GNSS_IFCS-EFTF_2019.pdf
There's a paper too, which I should upload.
In short, the F9P is very suitable for code-based time-transfer, and we
will be using it , or the F9T, in the next iteration of our time-transfer
system.

But, I don't see how you can feed an external 10 MHz and 1 pps to the F9T.
There don't appear to be any inputs for this on the chip. The TIMEMARK
inputs only seem to be useable for measurements. Have I missed something?

Regards
Michael

On Sun, 22 Sep 2019 at 12:30 am, Anders Wallin 
wrote:

> Hi all, we are testing an uBlox F9T (RCB-F9T timing-board) for the past few
> days. Small uBlox puck antenna in a not-so-great location.
> I get an ADEV of 3e-8/tau long-term (see pictures or blog)
>
> Through the UART there are lots and lots of settings to tweak with the
> uBlox software - I am wondering if anyone figured out optimal settings for
> stationary operation and best stability when the pulse1/pulse2 outputs are
> configured for 1PPS and 10 MHz. Is it using just GPS (or multi-GNSS?), dual
> or single-frequency, as the default setting?
>
> Also, it seems that on 10MHz there is dithering (8ns granularity?) - is
> there any simple way to generate a round-number out of the uBlox, and use a
> (simple) multiply/divide to get dithering-free 10MHz?
>
> we made a carrier-board for the RCB-F9T with an USB/UART conversion and
> buffered dual BNC outputs for pulse1/pulse2 - this might be published
> later...
>
> Further down the road, if the F9T really can do dual-frequency
> observations, and either the receiver clock 1PPS measured (TICC?) against
> an external 1PPS, or the entire receiver clocked from external 10M/1PPS -
> and dual-frequency RINEX generated from this - then there seems to be an
> obvious opportunity for making a low-cost dual-frequency time-transfer
> setup? Or am I missing something?
> PPP with F9T seems to be possible:
> https://gpsd.gitlab.io/gpsd/ppp-howto.html
>
> thanks,
> Anders
> board https://www.u-blox.com/en/product/rcb-f9t-timing-board
> antenna https://www.u-blox.com/en/product/ann-mb-series
> blog http://www.anderswallin.net/2019/09/ublox-f9t-test/
>
> [image: uBlox_oadev_tdev.png]
> [image: uBlox_F9T_timeseries.png]
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Re: [time-nuts] Galileo service currently degraded

[Michael Wouters]

Hello Kevin

There is a Perl script to configure and log the ublox that is
available as part of OpenTTP
https://github.com/openttp/openttp/tree/master/software/gpscv/ublox

Cheers
Michael

On Sun, Jul 14, 2019 at 8:03 AM Kevin Croissant
 wrote:
>
> This is the library I am using:
> https://github.com/jkua/ubx
>
> Basically the only applicable files are ublox2.py and ubloxMessage.py.
> There's some bug in how it handles its byte buffer and the buffer grows out
> of control, which causes all sorts of issues. I tried to fix it but failed
> due to time constraints. Highly recommend against touching that library...
>
> I started off by using NMEA but found that there is was more resolution in
> the UBX messages, so that's why I went that route. I thought there must be
> a way to get the same resolution, but did not figure it out, and eventually
> I had to just get it online so I could move on. Looking at gpsd, I'm still
> not sure that it supports UBX, and I think that was why I disregarded it
> before. Do you know if it does? The only UBX messages my project truly
> needs are NAV-PVT and NAV-DOP, though I look at other ones for data
> validation and debugging.
>
> Kevin
>
> On Sat, Jul 13, 2019 at 5:06 PM Hal Murray  wrote:
>
> >
> > ke...@kevincroissant.com said:
> > > The library I used for the U-blox UBX protocol frankly sucks, and was a
> > major
> > > source of issues.
> >
> > What library are you using and/or did you look at gpsd?
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> >
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> >
>
>
> --
> Kevin Croissant
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Re: [time-nuts] Galileo service currently degraded

[Michael Wouters]

We  monitor GNSS timing in this way ie with common, single-frequency
receivers configured to track a single GNSS system only, measured with
respect to UTC(AUS). The plan was to make the data publicly available
but that's still on the TODO. Currently we monitor GPS, GLONASS and
BeiDou.

Over the two years or so we've been doing this, I've noticed multiple
problems with receiver loss of tracking, even when many SVs  are
visible and useable, and lockups when tracking non-GPS signals. I
attribute this to bugs in the receiver firmware, rather than the GNSS.

There is of course a vast amount of data available already through the
many IGS stations reporting multi-GNSS data, just not in a convenient
form.

Cheers
Michael

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Re: [time-nuts] Galileo service currently degraded

[Michael Wouters]

The Galileo outage is being attributed to problems at the Precise Timing
Facility in Italy

https://insidegnss.com/update-galileo-service-degraded-on-all-satellites-precise-timing-facility-problems-cited/

Cheers
Michael


On Sun, 14 Jul 2019 at 7:06 am, Mark Sims  wrote:

> The satellite tracking / health  info is sent by the receiver.  Heather
> just reports what the receiver is sending.
>
> Oh, and the Galileo system status has changed from "degraded" to "service
> outage".
>
> https://www.gsc-europa.eu/system-status/Constellation-Information
>
> What is amazing is that I can find no other reports that the system is
> down.  Also how such a long and severe outage could happen.  I expect heads
> will be rolling...
>
> --
>
> > What prompts Heather to mark visible satellites as yellow, and not use
> them?
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Re: [time-nuts] Used Hydrogen Maser

[Michael Wouters]

I recently got some prices on Russian masers. The passive masers are about
$us90K and the active masers are about $US250K. There’s apparently quite a
bit of paperwork to do with the export licensing but it just needs a bit of
patience :-)


Cheers
Michael

On Thu, 11 Jul 2019 at 3:01 am, Bob kb8tq  wrote:

> Hi
>
> One of the gotcha’s if you are in the US is that the most often seen
> “alternate
> brand” of Maser comes out of Russia. Depending on the phase of the moon and
> just what the rule book says this week, you may well not be able to bring
> one
> into the country.
>
> Back when things were a bit more cordial and trade was more rational, the
> quoted
> price was in the $150 $200K range.
>
> Bob
>
> > On Jul 10, 2019, at 8:57 AM, Dana Whitlow  wrote:
> >
> > Perry,
> >
> > The only H-maser with which I've had direct experience (the MHM-2010)
> costs
> > around $250,000 new.  But there are some other brands, mostly foreign.
> >
> > The immediate operating cost is that of AC power.  IIRC, the '2010 uses
> > about
> > 100W or maybe 125W, *all the time*.  The H-maser is *not* the kind of
> thing
> > one
> > turns on when needed and back off in between uses.
> >
> > The hydrogen supply is usually large enough to last about 15 years or
> more.
> >
> > A sort of hidden cost is that the unit must be operated in a
> > temperature-controllled
> > environment for best stability- hence there is also the purchase and
> > operating costs
> > of a suitable A/C system.
> >
> > Also note that H-masers *do* drift in frequency over time.  The one we
> had
> > at Arecibo
> > typically needed frequency correction of about 3.5E-14 about every 4
> months
> > on average,
> > to keep the observatory's master clock on time within 25-50 nsec as
> needed
> > for certain
> > types of radio astronomy situations.  We used the H-maser because it has
> > the best
> > stability (over the range of seconds to hours) of anything commercially
> > available.
> >
> > The maser operated without difficulty for about the first 8 years before
> it
> > lost one of
> > its two vacion pumps.  We had to pay $12k for an engineer from
> Symmetricom
> > to
> > bring down a pair of new pumps and oversee the installation.  He replaced
> > the failed
> > one on one day while I took notes; then the next day I replaced the 2nd
> one
> > under
> > his close supervision and scrutiny.  Because the maser was well designed
> > with vacuum
> > isolation valves, both pump replacements were accomplished without
> shutting
> > down
> > the maser and with no disturbance to observations.
> >
> > A few years later the maser's internal log data showed that the hydrogen
> > pressure
> > was oscillating, along with synchronized fluctuations in drive to the Pd
> Pd
> > "valve",
> > with a period of about 11 days.   At this point there was no noticeable
> > effect on timing
> > accuracy.  A series of calls to Symmetricom customer service indicated
> that
> > they had
> > no idea what was going on, and they counseled "watchful waiting".  We did
> > that for
> > several more years up until I retired in Dec 2016, with the only change
> > being a very
> > gradual drift in oscillation period and amplitude.  The in late Dec 2018,
> > the maser
> > basically died outright, and Symmetricom (then part of Micro-Semi) was
> > unable to
> > provide a definite diagnosis- just a couple of theories.  But they
> advised
> > against
> > trying to fully diagnose and repair the unit, considering its advanced
> age
> > (approx
> > 15 years at the time).
> >
> > Hope this helps ...
> >
> > Dana
> >
> >
> >
> >
> > On Wed, Jul 10, 2019 at 7:00 AM Perry Sandeen via time-nuts <
> > time-nuts@lists.febo.com> wrote:
> >
> >> Yo Bubba Dudes!,
> >> OK, I'll finally ask the question that probably a lot of list members
> >> wanted to know but were reticent to ask.
> >> First, what is the price of one of a new Hydrogen Maser? (This is
> >> important if I win the lottery.)
> >> Second, what would be prices for used Hydrogen Maser in *reasonable*
> >> working condition and what might be the long term costs to keep it
> running?
> >> Thirdly, what are the chances of finding a used one?
> >> Then again, might it be better, money wise just to limp along with used
> HP
> >> Cs?
> >> Regards,
> >> Perrier
> >>
> >>
> >>
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Re: [time-nuts] Used Hydrogen Maser

[Michael Wouters]

about 20 years ago, JPL was operating a Hg ion clock at the  Tidbinbilla
tracking station just outside Canberra, Australia. I think they installed a
few at various nodes in the Deep Space Network at the time. It operated for
a few years but never reliably enough to be a useful UTC clock ( we were
submitting the data to BIPM). I don’t know what happened to it.

Cheers
Michael

On Thu, 11 Jul 2019 at 3:01 am, jimlux  wrote:

> On 7/10/19 6:10 AM, Azelio Boriani wrote:
> > Tom Van Baak said on Aug 29, 2013:
> >
> >> The pursuit of precision tends to be exponential rather than linear.
> > ...
> >> As a rough example in the ADEV world:
> >> - for 1e-11, you can buy almost any XO, TCXO, or risky OCXO for $10.
> >> - for 1e-12, you can find a reputable OCXO on eBay for under $100.
> >> - for 1e-13, you can find an old but maybe working cesium clock for 1
> k$.
> >> - for 1e-14, spend 10 k$ and get a certified working hp 5071A.
> >> - for 1e-15, spend 100 k$ and find a used active H-maser.
> >> - for 1e-16, spend 1 M$ to hire physicists and build a Cs fountain.
> >> - for 1e-17, spend 10 M$ to fund a national research institute to build
> ion or
> >> optical clocks.
> >
> >
> > Add the 1k USD running cost per year just to keep the active maser
> running.
> > I think that chances of finding an active H-maser used are near 0.
> > Better to stick with GPSDOs: they bring into your home the stability
> > and accuracy of the USNO UTC (well, close to...).
> >
>
>
> I wonder what it would cost to build a trapped Hg ion clock - I don't
> think it's $10M, but it might be in the range of $500k-1M if you pay
> people to do the work.  Things like the quadrupole trap and ion sources
> are catalog items.  The whole vacuum system, including a turbo pump, is
> probably in the $10k range (looking at the Cole Parmer catalog, first
> hit on google), maybe another $5k in various vacuum plumbing bits and
> pieces.
>
> back in 2005-2006 (published in 2007), Prestage et al had a lab version
> https://ieeexplore.ieee.org/document/4319251
>
> pumped, backfilled with Ne, then sealed
>
>
>
>
>
>
>
>
>
>
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Re: [time-nuts] Advantages of GNSS ???

[Michael Wouters]

Hello Luiz,

(Did we meet at IFCS-EFTF in Orlando? If so, my apologies for not
remembering your name, and for repeating here what you know). I presented
some preliminary time-transfer data for the F9P at IFCS and wrote a short
paper for the proceedings; if you’d like a copy, I am happy to send you one.

For any other time-nuts interested in post processed GNSS time -transfer:

Since the conference, I have been working on and off on adding dual
frequency support to OpenTTP ( www.openttp.org), principally for the F9P/T
and have four F9P receivers under test. The aim is to have a nice long data
set for EFTF next year.

Cheers
Michael

On Sat, 6 Jul 2019 at 2:02 pm, Luiz Paulo Damaceno <
luizpauloeletric...@gmail.com> wrote:

> Hey Graham,
>
> I'm gonna start a project soon to evaluate a F9P as a Time Transfer GNSS
> receiver. For now i haven't too much answers for you but only i know is:
> the BIPM uses all labs that participate from UTC to make corrections of
> GNSS satellites frequency, also for the TAI use. I think GNNS T is a good
> and reliable source for many projects. Here in my lab with Septentrio's
> Pola RX 3 Tr we have a very low Time Dilution Of Precision when the Glonass
> and all anothers becomes enabled, so our frequency if compared to all GNSS
> constallations is good, i think the same logic can be applied for frequency
> generation / distribution. What i want to say is: with more satellites of
> different constellations you can have a better end signal (more stable and
> reliable). Tests should be done. I hope can help more in the future.
>
> Best regards,
>
> Luiz
>
> Em sex, 5 de jul de 2019 às 23:00, Graham / KE9H 
> escreveu:
>
> > I have several questions for the group, since there are several members
> > that have been able to start evaluating the uBlox F9P and perhaps the F9T
> > GNSS receivers.
> >
> > For the purposes of time and frequency determination, is there an
> advantage
> > to using the GNSS receivers, relative to just the US GPS?
> >
> > It appears that a really good GPS (only) based GPSDO can get into the
> 1e-11
> > and perhaps the 1e-12 accuracy range.
> >
> > Does using the signals from GPS (USA), plus GLONASS (Russia), plus Beidou
> > (China), and plus Galileo (Europe), actually provide any improvement in
> > time/frequency accuracy?
> >
> > Is that what the F9P actually does, or only some sub-combinations of the
> > above?
> >
> > Down at that level of accuracy, do the four systems agree within 1 e-12,
> > anyway?
> >
> > Is there any advantage to using the GNSS for time/frequency?
> >
> > Does using the RTCM Corrections, needed to achieve the ~ 1 cm positioning
> > accuracy also improve time/frequency accuracy?
> >
> > The underlying question I am trying to get at is: Will a GNSS based GPSDO
> > have any advantage over a GPS-only, or a dual band L1/L2 GPS-only GPSDO?
> >
> > Thanks,
> > --- Graham
> >
> > ==
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Re: [time-nuts] Cloudflare

[Michael Wouters]

>A cable run from your rack in the middle of the datacenter, through to the
>roof, is either impossible or thousands of dollars and weeks of planning.
I've done this 4 times now for GPS antennas connected to NTP servers.
I agree with the thousands of dollars (2K to 4K for cable runs of
around 50 m) but there wasn't really much planning to do. We simply
engaged a contractor and they did all the rest.

Cheers
Michael


On Sat, Jun 22, 2019 at 1:00 PM Sanjeev Gupta  wrote:
>
> Bob,
>
> The hardware is cheap.  The software is free.  The skills to deploy are
> widely available.  But...
>
> A cable run from your rack in the middle of the datacenter, through to the
> roof, is either impossible or thousands of dollars and weeks of planning.
>
> Data centers can run wires within the building for exorbitant costs, asking
> them to run one to the exterior is, well, impossible.
>
> --
> Sanjeev Gupta
> +65 98551208 http://www.linkedin.com/in/ghane
>
>
> On Sat, Jun 22, 2019 at 6:06 AM Bob kb8tq  wrote:
>
> > Hi
> >
> > Given the relatively low cost of a GPS based “Stratum 1” NTP, it’s not
> > real clear
> > why (at the end of the paper) they go off and “exchange emails
> > individually with the
> > organizations that run stratum 1 servers, as well as negotiate permission
> > to use them.”
> > to source the root time for the system. I would have thought that some
> > sort of combo
> > of on site and off site sources would be at the “top of the tree”.
> >
> > Bob
> >
> > > On Jun 21, 2019, at 2:20 PM, Marco Davids via time-nuts <
> > time-nuts@lists.febo.com> wrote:
> > >
> > > Opinions, anyone?
> > >
> > > https://blog.cloudflare.com/secure-time/amp/
> > >
> > > ("Introducing time.cloudflare.com")
> > >
> > > --
> > > Marco
> > >
> > > ___
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Re: [time-nuts] The forbidden question

[Michael Wouters]

As promised, here's one pertinent paper, about using cryogenic
sapphire oscillators at mm-wavelengths ( 1 mm = 300 GHz ).
https://arxiv.org/pdf/1106.0021.pdf
It's not the one I was looking for but it's a useful entry point.
One interesting number is that at one mm, the coherence time is
limited to at most tens of seconds because of atmospheric turbulence.
Table 3 is worth a look too.

Cheers
Michael

On Fri, Jun 7, 2019 at 7:17 AM Michael Wouters
 wrote:
>
> My radio astronomer colleagues tell me that there is about a 20 minute limit 
> to VLBI observing runs because of atmospheric instability so this limits 
> improvements to be had from better clocks. My recollection is that a maser is 
> still sufficient out to 100 GHz. There is a paper about this that I will dig 
> out later.
>
> Cheers
> Michael
>
> On Thu, 6 Jun 2019 at 12:01 pm, Joseph B. Fitzgerald 
>  wrote:
>>
>>
>> Regarding Dana's remarks on VLBI, consider the recent black hole image 
>> released by the Event Horizon Telescope.Measurements were taken at 230 
>> GHz, and they would like to begin measurements at 345 GHz.Hydrogen 
>> masers were used at each telescope.I am no expert, but I strongly 
>> suspect that a better clock would result in longer/better observations.
>> The H maser only runs at 1.42 GHz ... the astrophysicist wizards are 
>> proposing to do their measurements at about 250 times higher in frequency!
>>
>>
>> -Joe
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Re: [time-nuts] The forbidden question

[Michael Wouters]

My radio astronomer colleagues tell me that there is about a 20 minute
limit to VLBI observing runs because of atmospheric instability so this
limits improvements to be had from better clocks. My recollection is that a
maser is still sufficient out to 100 GHz. There is a paper about this that
I will dig out later.

Cheers
Michael

On Thu, 6 Jun 2019 at 12:01 pm, Joseph B. Fitzgerald <
jfitzger...@alum.wpi.edu> wrote:

>
> Regarding Dana's remarks on VLBI, consider the recent black hole image
> released by the Event Horizon Telescope.Measurements were taken at 230
> GHz, and they would like to begin measurements at 345 GHz.Hydrogen
> masers were used at each telescope.I am no expert, but I strongly
> suspect that a better clock would result in longer/better observations.
> The H maser only runs at 1.42 GHz ... the astrophysicist wizards are
> proposing to do their measurements at about 250 times higher in frequency!
>
>
> -Joe
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[time-nuts] Rollover: Trimble Resolution T

[Michael Wouters]

Some older ResTs with v1.2 firmware stopped tracking 15 minutes after the
rollover but recovered trackingafter a hard reset. UTC time of day in the
8FAB message has stepped back 20 years, unsurprisingly.

Cheers
Michael
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Re: [time-nuts] GPS week rollover

[Michael Wouters]

A multichannel, L1 GPS-only simulator/recorder costs about US5k. We have
one of these that we used to test for rollover problems with some older
receivers that we use (none found). The software with this lower cost
device is not very sophisticated. As Bob hints though, a top of the line
simulator is very expensive, about us200k, the last time I asked.


On Sat, 30 Mar 2019 at 8:00 am, Bob kb8tq  wrote:

> Hi
>
> Obviously the real answer is going to be “that depends”.
>
> Back when I worked for a living, we had an HP generator that would “play
> back” a recorded ~ 30 minute
> set of GPS “full sky” observations. It was strictly a playback with no
> real way to tweak this or that. We also
> had a single channel device that could be set to do just about anything
> (but only a single channel / sat). The
> “full sky” gizmo is fine for things like sensitivity. The single channel
> device is of more use for poking at rollover
> issues.
>
> Indeed if you have the budget, you can get a setup that will let you run
> multiple sat systems with a dozen sats
> on each system at any simulated location,  time, signal level, errors …...
> Last time I priced one … .yikes ….. I don’t
> know of anybody doing timing with that sort of setup.
>
> Bob
>
> > On Mar 29, 2019, at 3:22 PM, John C. Westmoreland, P.E. <
> j...@westmorelandengineering.com> wrote:
> >
> > To All:
> >
> > I have a related question; hope it's OK:
> >
> > What are these companies using for their "GPS Simulation/Simulators?".
> >
> > Is it actually simulating the RF downlink or is a direct data stream
> > injection into a tap into the receiver??
> >
> > Thanks In Advance,
> > John W.
> >
> >
> > On Fri, Mar 29, 2019 at 11:00 AM Michael Shields via time-nuts <
> > time-nuts@lists.febo.com> wrote:
> >
> >> Avidyne avionics are known to be affected by the rollover, causing the
> >> loss of some displayed data.
> >>
> >> https://www.avidyne.com/files/downloads/606-00182-019.pdf
> >>
> >>
> >> On Thu, Mar 28, 2019 at 3:04 PM Mark Sims  wrote:
> >>>
> >>> I doubt that any GPS receivers will be newly affected on April 6.
>  Some
> >> very early receivers were hit on the first GPS rollover, but those made
> >> since then usually have a 1024 week compensation built in based upon the
> >> firmware creation date.  Those rollover 1024 weeks from that date and
> start
> >> sending incorrect dates at other places in the 1024 week cycle.  Some
> >> receivers even let you force the rollover week.
> >>>
>  I have a Z3816A that’s showing a yellow “ro” next to the date in LH
> >> and is 18 seconds ahead of a Motorola 12 channel
> >>>
> >>> If Lady Heather sees a date earlier than a set year (currently 2017),
> it
> >> assumes the GPS device has rollover issues and adds 1024 weeks to
> correct
> >> the date and shows the "ro" flag.
> >>>
> >>> As far as the 18 second time difference, one of the devices is
> >> configured to show GPS time and the other is set for UTC time.  At the
> top
> >> right corner of the screen it should say either "UTC time OK" or "GPS
> time
> >> OK" (as long as the device has a valid time).  The TG and TU commands
> can
> >> switch between GPS and UTC time displays.  Some receivers have firmware
> >> commands to switch between the two.  For the others, Heather does the
> >> conversion in software using the "UTC offset" (i.e. leapsecond count)
> >> value.  Many receivers send this offset.   If it does not, the user can
> set
> >> the value.  And if no value is available Heather makes a best guess as
> to
> >> what the value might be (and shows it in RED).  The guessed value is
> rather
> >> prone to errors, but is better than nothing.
> >>> ___
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> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >>> and follow the instructions there.
> >>
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Re: [time-nuts] Frequency Ensemble

[Michael Wouters]

Oops, units for TDEV are seconds, not nanoseconds!

On Wed, 20 Mar 2019 at 7:41 pm, Michael Wouters 
wrote:

> Hello Dan,
>
>
> As promised here is a comparison of the ZED-F9P and NEO-M8T
> sawtooth-corrected PPS. The PPS is measured against a 5071 with standard
> tube. Three days of data were used. The 5071 was measured against another
> 5071 and I divided the TDEV by sqrt(2). The 5071 data at shorter than 300s
> is limited by the counter resolution so I didn't show it. The ZED-F9P is
> significantly better than the M8T between 10 and 1000 s but much the same
> past 1s.
>
> Cheers
> Michael
>
> On Tue, 19 Mar 2019 at 8:02 am, Dan Kemppainen 
> wrote:
>
>> Bob,
>>
>> I recalled the plot you posted a few days ago. Nice plot on the F9P,
>> BTW. Thanks for posting that.
>>
>> I don't supposed you happened to be recording a similar plot with a L1
>> only Ublox part at the same time by chance, did you? I think it would be
>> interesting to compare a 6T or M8 part to the F9P. (I lack a standard
>> good enough to compare them to...)
>>
>> Thanks!
>> Dan
>>
>>
>>
>>
>> On 3/18/2019 1:00 PM, time-nuts-requ...@lists.febo.com wrote:
>> > Message: 2
>> > Date: Mon, 18 Mar 2019 12:26:55 -0400
>> > From: Bob kb8tq
>> > To: Discussion of precise time and frequency measurement
>> >   
>> > Subject: Re: [time-nuts] Frequency Ensemble
>> > Message-ID:<88460ea2-6034-48d1-a77a-fed1f824d...@n1k.org>
>> > Content-Type: text/plain; charset=utf-8
>> >
>> > Hi
>> >
>> > There are a variety of GPS devices that put out a PPS. uBlox makes
>> some, there
>> > are a number of other companies that do so. The PPS comes out modulo
>> the local
>> > timebase. On a precision part, there is a ?sawtooth correction? message
>> that also
>> > comes out to further quantify the best guess time of that pulse.
>> >
>> > Noise wise, even with correction you are lucky to get a one second ADEV
>> in the
>> > 1 to 2 ppb range with a typical L1 receiver. With a L1 / L2 device like
>> the F9P,
>> > you might do a bit better than that.
>> >
>> > The ADEV of your other sources at short tau will be much better than
>> the GPS PPS
>> > noise. As you average out over long periods, the GPS will win the race.
>> >
>> > Bob
>>
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>>
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Re: [time-nuts] Frequency Ensemble

[Michael Wouters]

Hello Dan,

As promised here is a comparison of the ZED-F9P and NEO-M8T
sawtooth-corrected PPS. The PPS is measured against a 5071 with standard
tube. Three days of data were used. The 5071 was measured against another
5071 and I divided the TDEV by sqrt(2). The 5071 data at shorter than 300s
is limited by the counter resolution so I didn't show it. The ZED-F9P is
significantly better than the M8T between 10 and 1000 s but much the same
past 1s.

Cheers
Michael

On Tue, 19 Mar 2019 at 8:02 am, Dan Kemppainen 
wrote:

> Bob,
>
> I recalled the plot you posted a few days ago. Nice plot on the F9P,
> BTW. Thanks for posting that.
>
> I don't supposed you happened to be recording a similar plot with a L1
> only Ublox part at the same time by chance, did you? I think it would be
> interesting to compare a 6T or M8 part to the F9P. (I lack a standard
> good enough to compare them to...)
>
> Thanks!
> Dan
>
>
>
>
> On 3/18/2019 1:00 PM, time-nuts-requ...@lists.febo.com wrote:
> > Message: 2
> > Date: Mon, 18 Mar 2019 12:26:55 -0400
> > From: Bob kb8tq
> > To: Discussion of precise time and frequency measurement
> >   
> > Subject: Re: [time-nuts] Frequency Ensemble
> > Message-ID:<88460ea2-6034-48d1-a77a-fed1f824d...@n1k.org>
> > Content-Type: text/plain; charset=utf-8
> >
> > Hi
> >
> > There are a variety of GPS devices that put out a PPS. uBlox makes some,
> there
> > are a number of other companies that do so. The PPS comes out modulo the
> local
> > timebase. On a precision part, there is a ?sawtooth correction? message
> that also
> > comes out to further quantify the best guess time of that pulse.
> >
> > Noise wise, even with correction you are lucky to get a one second ADEV
> in the
> > 1 to 2 ppb range with a typical L1 receiver. With a L1 / L2 device like
> the F9P,
> > you might do a bit better than that.
> >
> > The ADEV of your other sources at short tau will be much better than the
> GPS PPS
> > noise. As you average out over long periods, the GPS will win the race.
> >
> > Bob
>
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Re: [time-nuts] Frequency Ensemble

[Michael Wouters]

The f9p is about 3 times better than  the ublox m8t. Will post a plot
later..

Cheers
Michael

On Tue, 19 Mar 2019 at 9:00 am, Bob kb8tq  wrote:

> Hi
>
> ….. and here I was wondering if it had ever gone out :) Glad it made it.
>
> No, I did not run any single frequency units beside it. It is much better
> than any similar plot
> I’ve done in the past on an L1 only part.
>
> Indeed, as long as you just look at the first ~ 100 seconds, the
> “reference standard” is less of an issue.
> A fairly typical OCXO will hang in there at 2 ppt or so out to a couple
> hundred seconds.
> You can get a very good idea of what’s what simply by going out that far.
> Indeed you might spend
> some “quality time” finding a working example of something like a MT-260.
> That’s part of the fun ….
> Some of the better parts will be 5 MHz units. A HP 5335 can come in handy
> to turn 5 MHz into
> 10 MHz ….. there are a lot of ways to get that done.
>
> Yes LH and a TAPPR TICC would also help in the process …. still need those
> 25 orders :)
>
> Bob
>
> > On Mar 18, 2019, at 3:29 PM, Dan Kemppainen 
> wrote:
> >
> > Bob,
> >
> > I recalled the plot you posted a few days ago. Nice plot on the F9P,
> BTW. Thanks for posting that.
> >
> > I don't supposed you happened to be recording a similar plot with a L1
> only Ublox part at the same time by chance, did you? I think it would be
> interesting to compare a 6T or M8 part to the F9P. (I lack a standard good
> enough to compare them to...)
> >
> > Thanks!
> > Dan
> >
> >
> >
> >
> > On 3/18/2019 1:00 PM, time-nuts-requ...@lists.febo.com wrote:
> >> Message: 2
> >> Date: Mon, 18 Mar 2019 12:26:55 -0400
> >> From: Bob kb8tq
> >> To: Discussion of precise time and frequency measurement
> >>  
> >> Subject: Re: [time-nuts] Frequency Ensemble
> >> Message-ID:<88460ea2-6034-48d1-a77a-fed1f824d...@n1k.org>
> >> Content-Type: text/plain;charset=utf-8
> >> Hi
> >> There are a variety of GPS devices that put out a PPS. uBlox makes
> some, there
> >> are a number of other companies that do so. The PPS comes out modulo
> the local
> >> timebase. On a precision part, there is a ?sawtooth correction? message
> that also
> >> comes out to further quantify the best guess time of that pulse.
> >> Noise wise, even with correction you are lucky to get a one second ADEV
> in the
> >> 1 to 2 ppb range with a typical L1 receiver. With a L1 / L2 device like
> the F9P,
> >> you might do a bit better than that.
> >> The ADEV of your other sources at short tau will be much better than
> the GPS PPS
> >> noise. As you average out over long periods, the GPS will win the race.
> >> Bob
> >
> > ___
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> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
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Re: [time-nuts] Frequency Ensemble

[Michael Wouters]

This project www.openttp.org provides software for post-processing of raw
data for time-transfer from some currently available single frequency
receivers. It provides CGGTTS and RINEX, the latter for use with the
various PPP services. There are some tools in there too for doing eg common
view and all-in-view comparisons. If you want to try it out, the develop
branch in the GitHub repo is the place to start. I'll be talking about it
at IFCS-EFTF.

Cheers
Michael


On Tue, 19 Mar 2019 at 5:08 am, Anders Wallin 
wrote:

> If you search for "GNSS time transfer" you will find a lot of papers etc.
> For example these might get you started:
>
> https://www.bipm.org/ws/CCTF/TAI_TRAINING/Allowed/Fundamentals/Training-2012-GNSS-Defraigne.pdf
> https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7909843
>
> I tried to collect some tools for PPP post-processing on github:
> https://github.com/aewallin/ppp-tools
> I am not sure what (open) software exists for common-view analysis...
> PPP uses satellite clock-corrections and orbit-corrections from an IGS
> data-centre. They have "ultra rapid" and "rapid" products (=downloadable
> files) that are available with some days or hours of delay.
> The "final" products can have up to two weeks (?) of delay.
> With a dual-frequency receiver the ionosphere delay can be removed
> ('ionosphere-free L1/L2 linear combination') and my understanding is the
> troposphere-delay (water content) is one of the larger remaining
> uncertainties.
>
> AW
>
>
> On Mon, Mar 18, 2019 at 5:03 PM Rodger via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
> >
> > Regarding your comments on collecting raw time data from GPS and post
> > processing it.  Can you provide any reference info, links, etc. with more
> > detail on that topic?
> > Clearly I'd need a GPS that outputs the proper raw messaging and the
> > software for processing it.  I'm somewhat familiar with the techniques
> > involved to improve GPS position data, but hadn't thought about it as
> much
> > for timing.
> >
> > Thanks,
> >
> > Rodger
> >
> >
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Re: [time-nuts] PRS-10 Warm-up Time, Calibrating/Adjusting, and long-term poweron

[Michael Wouters]

We have operated  about 40 PRS10s over the past 20 years or so. These are
all run continuously in benign environments and monitored via GPS
time-transfer . Some have died after just over a year; others have operated
for more than 12 years. A new one generally takes a few months to burn in,
before its frequency drift stabilises to something like the specifications.
They do not behave very predictably, showing sudden changes in frequency
and so on. One exhibited frequent steps for a few years and then the
problem went away. Trying to predict what they would do at the level of
better than a few parts in 10^11 seems difficult.

 Cheers
Michael


On Sat, 9 Mar 2019 at 3:03 am, Attila Kinali  wrote:

> On Fri, 8 Mar 2019 06:31:48 -0600
> Dana Whitlow  wrote:
>
> > The point here is that there are apparently a number of warm up drift
> > mechanisms operating, some of which take days to sensibly settle down.
>
> Longer. I know of one measurement, where the Rb had a kind of stable
> drift until it suddenly switched to another slope quite suddenly
> (within a few days) about half a year after power up.
>
> The aging mechanisms of Rb vapor cell standards are many and not
> all of them are well understood, much less controlled. Compared
> to that, an OCXO has "only" thermal stability of the oven, strain
> relaxation of the holder/crystal and deposition/removal of contaminants
> on the crystal surface. Ok, there are a couple more, but these three
> are the main contributors for most OCXO out there. While for the
> Rb vapor cell standard I could name you half a dozen just like that
> and I am far from being an expert on these.
>
> For those interested, John Vig wrote a couple of papers on the aging
> of OCXO in the 80s and 90s. The topic of Rb vapor cell aging is a lot
> more messy and I don't know whether there is any good paper that reviews
> the main contributors.
>
> Attila Kinali
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>  -- Miss Matheson, The Diamond Age, Neal Stephenson
>
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Re: [time-nuts] ZED F9T first look

[Michael Wouters]

Fwiw, I have been evaluating the F9P for post-processed time transfer
(code-based) and it's looking significantly better than the NEOM8T. Tdev is
about 3 times better, mainly due to a reduction in the tdev of the
sawtooth-corrected pps. Zero baseline performance is getting close to that
of a top of the line time-transfer receiver for code-based transfer.

Cheers
Michael



On Mon, 4 Mar 2019 at 1:30 pm, Chris Burford 
wrote:

> For those that are interested in the soon to be released ZED-F9T receiver
> here is a quick write up on the RTLExplorer blog:
>
> https://rtklibexplorer.wordpress.com/
>
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Re: [time-nuts] Leitch CSD-5300 Master Clock Manual

[Michael Wouters]

Hello Rodger,
We have one of these still operating in the lab and I have a manual. Please
contact me off list.

Cheers
Michael

On Tue, 26 Feb 2019 at 3:00 am, Rodger via time-nuts <
time-nuts@lists.febo.com> wrote:

> Thanks but that manual is for the slave clock displays.  I'm looking for
> the
> manual for the master, which is a single unit, rack mounted device.
>
> -Original Message-
> From: time-nuts  On Behalf Of Joseph
> Gray
> Sent: Monday, February 25, 2019 3:52 AM
> To: Discussion of precise time and frequency measurement
> 
> Subject: Re: [time-nuts] Leitch CSD-5300 Master Clock Manual
>
> Older model, but this may help.
>
>
> http://www.drivehq.com/file/df.aspx/shareID3748302/fileID641557522/641557522
> .pdf
> 
>
> Joe Gray
> W5JG
>
>
> On Sun, Feb 24, 2019 at 9:03 PM Rodger via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
> > Hello List,
> >
> >
> >
> > I am looking for the manual for a Leitch CSD-5300 master clock.  These
> > were used in the broadcast industry in the 80s and 90s.  There is a
> > related white paper on the internet titled "A Telephone-Based Time
> > Dissemination System"
> > with a filename of ADA499239.pdf that describes the system but this is
> > NOT the document I'm looking for.  I'm hoping to find an
> > operations/service manual that includes connector pinouts, schematics,
> > etc.  I know it exists but it's been many years since I've seen a copy.
> >
> >
> >
> > This is an interesting device that is frequently available on the
> > auction sites.  It accepts a 5 or 10 mhz reference input and outputs
> > SMPTE timecode,
> > BCD time/date, as well as impulse drive.   Any help with the manual will
> be
> > appreciated.
> >
> >
> >
> > Thanks in advance.
> >
> >
> >
> > Rodger Adams, WB4HIR
> >
> > ___
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> >
> >
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Re: [time-nuts] GPS Weekly Rollover Fail

[Michael Wouters]

BeiDou, Galileo and GLONASS all broadcast UTC time of day (or thereabouts
for GLONASS - it's offset by the timezone for Moscow) so any multi-GNSS
receiver has a sanity check on UTC calculated from GPS.

Michael

On Wed, 6 Feb 2019 at 11:03 am, Bob kb8tq  wrote:

> Hi
>
> From what I can see, you can send it a command that puts a new “oldest
> date”
> number into flash. Since it also tracks Glonass and Galileo, that will
> stretch out the
> time before you *need* to do something (like into the next century). They
> also have
> the “no dates before the firmware was issued” check.  There may be other
> date
> checks in there. Those are just what I’ve found so far.
>
> It also is likely that the “new” GPS sats will be flying within 19 years.
> That will add
> more bits to the GPS time fields. Who knows if the “modern” modules
> already handle
> those bits or not ….
>
> Bob
>
> > On Feb 5, 2019, at 5:23 PM, Hal Murray  wrote:
> >
> >
> > kb...@n1k.org said:
> >> The F9P has multiple cross checks, traps, and even a user configurable
> >> “oldest  possible date” entry.
> >
> > Neat/thanks.
> >
> > Is that stored in flash, or lost on power cycle?
> >
> > If it's in flash, I can "fix" things for another 20 years by extracting
> the
> > device from its box, taking it to a bench setup, running a flash-update
> > program, then reassembling things.  As ugly as that is, it may be
> simpler than
> > updating the firmware in the box.
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> >
> > ___
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Re: [time-nuts] Ublox F9P multi-band GPS receiver

[Michael Wouters]

If you scroll down to the bottom of the product pages for the zed-f9x
modules, you'll see the 'ANN-MB', a L1/L2/E5b antenna that ublox is
presumably making to go with the ZED-F9. It's still marked 'preorder'

Cheers
Michael




On Tue, 22 Jan 2019 at 6:00 am, Bob kb8tq  wrote:

> Hi
>
> To be more precise, what you want is a L1/L2/L5 triple band antenna.
>
> Bob
>
> > On Jan 21, 2019, at 11:32 AM, Bob kb8tq  wrote:
> >
> > Hi
> >
> > Based on the F9P data sheet, you will need an L1 / L2 antenna that is
> wide enough
> > to get the Galileo E5B as well as the Glonass L1OF and L2OF bands. The
> gotcha
> > is that (so far) I have not found a gain number for the target antenna.
> As we have
> > found on other modules, you do want to get the right gain. L1/L2
> antennas range
> > from 50+ db down to below 30 db. Simply tacking a pad on a 50 db antenna
> is not
> > the best way to do things if you are in an urban area.
> >
> > There also is the issue of powering the antenna. It is not clear what
> sort of antenna
> > bias circuit the SparkFun module has on it. If it simply is using the
> module’s bias setup
> > that also could be an issue. Max Vcc on the module is 3.6V. The VCC_RF
> pin can have
> > main Vcc - 0.1V max on it. If that *really* means that 3.3V is about it
> for antenna bias,
> > that eliminates roughly 100% of all the used antennas out there. It also
> eliminates a
> > number of the new ones.
> >
> > If you put in an external bias setup, there are a lot of antennas to
> pick from on eBay.
> > They come and go. The used stuff generally will be 12V powered. It also
> is likely
> > to have a pretty good data sheet on it. The new stuff from China seems
> to be sold
> > by a variety of people who pop up for a while and then go away for a
> while. Making
> > sure of what you are getting is a bit tough as a result. There are
> extensive stories
> > in the archives …..
> >
> > Bob
> >
> >> On Jan 21, 2019, at 10:21 AM, Graham / KE9H 
> wrote:
> >>
> >> What kind of antenna is needed to simultaneously hear all of the
> systems at
> >> once?
> >> My PCTel GPS antenna has a filter that limits it to only the US GPS
> system.
> >>
> >> --- Graham
> >>
> >> ==
> >>
> >> On Mon, Jan 21, 2019 at 4:01 AM Dustin Marquess 
> wrote:
> >>
> >>> If DigiKey's pricing is accurate, the ZED-F9T is $13.89 more than a
> >>> ZED-F9P.  I would have gladly paid $14 more for a version of the
> >>> SparkFun board using the T(iming) version instead :(.
> >>>
> >>> On Mon, Jan 21, 2019 at 12:10 AM Bob kb8tq  wrote:
> 
>  Hi
> 
>  From a *very* quick read of the doc’s:
> 
>  1) The device *does* have a position hold capability
> 
>  2) There is some level of data on the time pulse. It it only 1 ns
> >>> resolution?
> 
>  3) It does appear to support Galileo and Glonas in addition to GPS.
> 
>  4) It is clearly multi-band for GPS. It is unclear from a quick read
> if
> >>> it is multi-band for the other systems.
> 
>  5) If you get one, make sure you have the RF cable connector it needs.
> 
>  6) I have not (yet) found a recommendation for the antenna gain.
> 
>  Again, all from a quick read ….
> 
>  Bob
> 
> > On Jan 20, 2019, at 5:42 PM, Mark Sims  wrote:
> >
> > Sparkfun is now selling the Ublox F9P L1/L2 GPS receiver module on a
> >>> board ($219).  The F9P supports GPS/Galileo/Glonass/Beidou and tracks
> L1/L2
> >>> data.  It outputs carrier phase data and has survey-in and fixed
> position
> >>> support along with RTK support (10 mm accuracy).   Looks like the F9P
> has 1
> >>> time pulse output.
> > ___
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> > To unsubscribe, go to
> >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> 
> 
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> >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>  and follow the instructions there.
> >>>
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> >>> and follow the instructions there.
> >>>
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Re: [time-nuts] Ashtech Z12T

[Michael Wouters]

Hello JF

(Ccing to time nuts because probably still of interest)
The TTR6 is a single channel receiver so you had to install an observing
schedule appropriate to your geographical region, which specified which
satellite you would track at which time. The BIPM used to generate and
distribute these schedules every 6 months or so but stopped doing this 7?
years ago - I think this is what you mean by "ephemerides".

If you have N satellites tracked then you can reduce the time transfer
noise by sqrt(N) roughly speaking. You can either do common view, where you
match satellites at each location and time, and then take an average of the
differences, or all in view, where you average all of the satellites
visible at each location, and then difference. Common view gives you less
noise (because of better cancellation of eg the effects of the ionosphere)
on short baselines. However as the baseline increases in length, the number
of satellites in common view decreases and the statistical noise increases.
At distances of a few thousand km, all in view starts to win because more
satellites are used. You can improve the processing by doing things like
weighting  the satellites according to their elevation.

The current best method of doing GNSS time-transfer is PPP or precise point
positioning, and is a form of all in view, with much better post-processing
that uses both code and phase observatIons. You can do this with the
Septentrio receivers. But CGGTTS-based time transfer is still used in the
timing community.

Cheers
Michael


On Tue, 4 Dec 2018 at 9:19 pm, JF PICARD  wrote:

> Hello,
>
> Thank you very much for your explanations but, as a newbie in this immense
> domain, I have got some questions. With the Allen Osborne TTR-6 we received
> from the LNE SYRTE (french observatory)  and loaded the ephemiredes (data
> about the GPS satellites passing above us the next week or month) and we
> will follow satellite X, the Y... , we sent our received data and we got
> the data from LNE for the same satellite...
> How does the actual system operate with several satellites ? I haven't
> seen any mention (quick overlook in the data sheet) neither in the
> Septentrio nor in the NVS...
>
> Cheers.
>
> JF
> ------------
> On Mon, 12/3/18, Michael Wouters  wrote:
>
>  Subject: Re: [time-nuts] Ashtech Z12T
>  To: "Discussion of precise time and frequency measurement" <
> time-nuts@lists.febo.com>, "JF PICARD" 
>  Date: Monday, December 3, 2018, 8:42 PM
>
>  Hello
>  There are many alternatives to the
>  Z12T. It all depends on your budget. I am guessing that you
>  want to establish legal traceability to your local UTC, is
>  that right?
>  Starting
>  at the top end, you can buy complete systems from Dicom and
>  Piktime. These cost about $25K and $40K respectively. These
>  are multi-frequency, multi-GNSS systems.
>  There are also some cheaper, single
>  frequency systems (GPS only)  available too, from a company
>  in Japan and one in the U.K. Just search for "time
>  transfer system".
>  Some NMIs in countries like Canada,
>  Australia, Japan, ... offer remote calibration services of
>  the kind you want to set up. These  are too far away for
>  common view but I suppose all in view would be the method in
>  this case ( you would still have traceability to your UTC
>  via the CIPM Mutual Recognition Agreement). Costs are
>  something like $5K per year, in addition to the
>  hardware.
>  You can just
>  buy a shiny new time-transfer receiver like the Septentrio
>  PolaRx5TRPRO with a geodetic antenna for about $20K. These
>  are the most popular in the timing community at the moment.
>  But other receivers like Javad and Trimble are good
>  too.
>  If single
>  frequency performance is good enough, and you're willing
>  to do a bit of work setting up software, then the really low
>  cost solution is something like the software from www.openttp.orgThe
>  main receiver supported, the NVS NV08C is less than $100.
>  You can get accurate antenna positions from this receiver in
>  a base rover configuration. All the rest is post processing
>  and there are various options here. You will also need a
>  counter/timer and the low cost solution here is the TAPR
>  TICC, which is also supported by OpenTTP.
>  CheersMichael
>
>  On Mon, 3
>  Dec 2018 at 10:21 pm, JF PICARD via time-nuts 
>  wrote:
>  Thank you
>  for answer and sorry for delay. Purpose is simultaneous view
>  of GPS satellites with the french official time laboratory
>  LNE SYRTE . The corrections factors from the laboratory will
>  enable to get with our high performance cesium about 5.
>  10-13  . Today the cesium is running alone. Discussion with
>  some people involved 

Re: [time-nuts] Ashtech Z12T

[Michael Wouters]

Hello

There are many alternatives to the Z12T. It all depends on your budget. I
am guessing that you want to establish legal traceability to your local
UTC, is that right?

Starting at the top end, you can buy complete systems from Dicom and
Piktime. These cost about $25K and $40K respectively. These are
multi-frequency, multi-GNSS systems.

There are also some cheaper, single frequency systems (GPS only)  available
too, from a company in Japan and one in the U.K. Just search for "time
transfer system".

Some NMIs in countries like Canada, Australia, Japan, ... offer remote
calibration services of the kind you want to set up. These  are too far
away for common view but I suppose all in view would be the method in this
case ( you would still have traceability to your UTC via the CIPM Mutual
Recognition Agreement). Costs are something like $5K per year, in addition
to the hardware.

You can just buy a shiny new time-transfer receiver like the Septentrio
PolaRx5TRPRO with a geodetic antenna for about $20K. These are the most
popular in the timing community at the moment. But other receivers like
Javad and Trimble are good too.

If single frequency performance is good enough, and you're willing to do a
bit of work setting up software, then the really low cost solution is
something like the software from www.openttp.org
The main receiver supported, the NVS NV08C is less than $100. You can get
accurate antenna positions from this receiver in a base rover
configuration. All the rest is post processing and there are various
options here. You will also need a counter/timer and the low cost solution
here is the TAPR TICC, which is also supported by OpenTTP.

Cheers
Michael


On Mon, 3 Dec 2018 at 10:21 pm, JF PICARD via time-nuts <
time-nuts@lists.febo.com> wrote:

> Thank you for answer and sorry for delay. Purpose is simultaneous view of
> GPS satellites with the french official time laboratory LNE SYRTE . The
> corrections factors from the laboratory will enable to get with our high
> performance cesium about 5. 10-13  . Today the cesium is running alone.
> Discussion with some people involved in this worlwide common practice spoke
> about the Z12T but if there is anything more modern..
> 
> On Wed, 11/28/18, Tom Van Baak  wrote:
>
>  Subject: Re: [time-nuts] Ashtech Z12T
>  To: "Discussion of precise time and frequency measurement" <
> time-nuts@lists.febo.com>
>  Date: Wednesday, November 28, 2018, 10:12 PM
>
>  The Z12T is a bit old by now, although some
>  of us own or have used them. Z12 documentation is available
>  on multiple archived Ashtech web sites. Lots of conference /
>  technical papers describing time transfer with Z12T
>  receivers exist. AFAIK a number of national timing labs
>  still use them.
>
>  What is it you're trying to do? Do you
>  own a Z12T and are just looking for spare parts? Or are you
>  looking for modern time transfer via GPS / GNSS? If so, what
>  level of timing accuracy are you looking for? Perhaps you
>  could explain a bit more what your actual request is, or
>  what timing infrastructure you already have running.
>
>  /tvb
>
>  - Original Message -
>  From: "JF PICARD via time-nuts" 
>  To: 
>  Cc: "JF PICARD" 
>  Sent: Wednesday, November 28, 2018 9:33
>  AM
>  Subject: [time-nuts] Ashtech Z12T
>
>
>  > Hello,
>  > I am looking for a time transfer
>  system Ashtech Z12T or equivalent. Thank you.
>  >
>  >
>  ___
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>  there.
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>
>
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