Re: [time-nuts] LeoNTP PPS output to PC DB9 input

[Mike Cook]

I don’t have one of these but I wouldn’t connect anything to anything without 
knowing the specs. 

I went to their site but could not find any specs on the outputs on the BNC 
connector. I should mail them at ord...@uputronics.com for the details. 
 
It could be a simple BNC to DB9 soldering job.  But there is something else to 
consider.
What happens when there is a power cycle? 
Does the LeoNTP BNC output come up in the last configured state? Does it come 
up in OFF mode or with 10MHz? I doubt that your BSD box would appreciate 10Mhz.



> Le 29 mai 2019 à 07:18, tom burkart  a écrit :
> 
> Quoting Anthony Dunne :
> 
>> Firstly would this work?
> Yes.
> 
>> Secondly, my dilemma is the pin-out.
>> I believe on the DB9 pin 1 is DCD (the actual pulse) and pin 5 is the 
>> ground. Is this correct?
> Yes.
> 
>> Could I use a cable such as this:-
> No.
> 
>> Alternatively, is there a simpler way to achieve the goal?
> No, you really need a level shifting stage that converts the PPS to RS232 
> levels.
> 
> Tom
> 
> 
> 
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Re: [time-nuts] imprecise but adequate time

[Mike Cook]

> Le 28 mai 2019 à 16:38, Eric Scace  a écrit :
> 
> Hi fellow time nuts —
> 
>   I’m looking for a sanity check or alternative suggestions for the problem 
> and tentative solution described below.

You have a situation where the application in any one system is unaware of the 
validity of the underlying OS time. So I think you have to have a mechanism 
where transactions are refused/re-routed if that validity can not be 
established. So I would say that some mechanism be put in place to check the 
local clock against the time reported by a majority , or a large enough sample, 
of the networks systems. Depending on the transaction rate that could be done 
on a per transaction, or reasonable interval. 

> 
>   Thanks for your thoughts.
> 
> — Eric
> 
> Problem:
> 
>   In one of my day jobs, I am designing a global network of systems (using 
> open-source software) that provide well-researched information about rights 
> and licenses for musical works (e.g., songs, compositions).
> 
>   Claiming rights, registering licenses (some of which are temporary), and 
> time-stamping changes to data each exemplify cases where date/time must be 
> included. In many cases the time order of events can be important — 
> potentially changing who gets paid how much when music is performed or 
> distributed.
> 
>   The machines are scattered around the planet and the usual problems of time 
> distribution exist. Furthermore, systems are operated independently. We 
> assume  occasional use of NTP to correct system clocks, but not a local 
> GPS-provided time. The software development team is generally oblivious to 
> the issues of time in distributed computer networks.
> 
>   A grim picture — but, fortunately, this application does not require high 
> precision time.
> 
> My tentative proposal:
> 
>   1. To avoid burdening systems with multiple local time conversions, all 
> date/time information throughout the system shall be UTC. Implications:
> user apps will be responsible for converting from a human user’s local time 
> to UTC
> thus, user app developers will have to do this conversion correctly
> 
>   2. Date/time stamps in the data shall be rounded to the nearest EVEN second 
> by the system instances; e.g., to 2019 May 28 14:24:28 UTC. Implications:
> user apps that submit claims or updates will have their claims/updates 
> date/time-stamped by the receiving system node with this rounding method. 
> Example: “John Smith claims that he and Jane Doe wrote these lyrics, making 
> an equal contribution between them, on 2019 May 27 15:00:00 UTC. His claim 
> was received by the system at 2019 May 28 14:26:50 UTC.” One or more 
> blockchain ledgers record a hash of the musical work [the lyrics, in this 
> example], the claim [who wrote the lyrics when], and which app/system 
> registered the claim and when.
> events occurring roughly within ±1 second of each other will be deemed to 
> have occurred simultaneously. This is entirely adequate for this application.
> competing leap second smearing methods employed by different operating 
> systems and data center operators will be washed out of the time stamp by 
> this rounding requirement.
> 
> — end —
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Re: [time-nuts] Updating the unit of,time: the second.

[Mike Cook]

> Le 27 mai 2019 à 11:13, Dave B via time-nuts  a 
> écrit :
> 
> Hi.
> 
> This from the recent ShortWave Radiogram broadcast, may be of interest.
> 
> ~ ~ ~
> 
> (Snipped stuff about other SI units undergoing a revamp...)
> 
> Scientists now have their sights set on updating the unit of
> time: the second.
> 
> Currently, the second is defined by atomic clocks made of cesium
> atoms. Those atoms absorb a certain frequency of light. The
> wiggling of the light's electromagnetic waves functions like the
> pendulum on a grandfather clock, rhythmically keeping time. One
> second is defined as 9,192,631,770 oscillations of the light.
> 
> But a new generation of atomic clocks, known as optical atomic
> clocks, outdo the cesium clocks. "Their performance is a lot
> better than what currently defines the second," says physicist
> Andrew Ludlow of the National Institute of Standards and
> Technology in Boulder, Colo. Because those optical atomic clocks
> operate at a higher frequency, their "ticks" are more closely
> spaced, making them about 100 times more precise than cesium
> clocks.
> 
> Ideally, the length of a second should be defined using the most
> precise timepieces available. A switch might happen in the late
> 2020s, Ludlow says.

I disagree with this.

a. There is no need for a new definition.
b. Any new definition would have to be realizable and easily verifiable. 
c. The first commercial cesium clocks were available in 1956, but the second 
did not get redefined until 1967.  There is no rush.
I believe that commercial optical clocks are available but:
d. There are too many flavors of optical clocks around on lab benches. So 
despite their increased precision and stability which flavor would get the vote?

So I predict that that will be no change in the definition in the next 20 years 
and chip scale optical clocks will be available before five years hence.


> 
> The change to the kilogram's definition was carefully
> orchestrated so that it wouldn't affect normal people: A kilogram
> of flour still makes the same number of biscuits. Any change to
> the second will be similarly coordinated.
> 
> So, sorry, there'll be no chance to squeeze any extra seconds
> into a day.
> 
> https://www.sciencenews.org/article/kilogram-just-got-revamp-unit-time-might-be-next
> 
> ~ ~ ~
> 
> So, perhaps a host of surplus cesium clocks on the market at some point?
> 
> 73
> 
> Dave B G0WBX.
> 
> -- 
> Created on and sent from a Unix like PC running and using free and open 
> source software:
> 
> 
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[time-nuts] GPS rollover repair???

[Mike Cook]

Hi,
  Yesterday, pre-rollover,  I reported that my Emap nav device had rolled over 
once:

"I checked my Garmin Emap, 1999 vintage IIRC. That is telling me that it is 
20/05/2014. "

I left it out over the rollover this morning and surprise surprise the date has 
switched back to the correct date. 

Anyone see that behavior with other old devices?



Have a nice day,
Mike

Those who would give up essential Liberty, to purchase a little temporary 
Safety, deserve neither Liberty nor Safety. 


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Re: [time-nuts] GPS 50 bps recording today

[Mike Cook]

Ok.
I have a bin file recording going via winoncore12 of the Raw data from an M12 .
I hope that it is OK. 
Mike


> Le 6 avr. 2019 à 21:14, Tom Van Baak  a écrit :
> 
> Would someone be a hero and record the raw subframe data from GPS today? It's 
> only 50 bits per second (that's about 8 bytes/second) per SV.
> 
> A select few GPS receivers have binary commands that return this low level of 
> detail: M12 (@@Tr), SiRF (8), uBlox (RXM-SFRB).
> 
> My attempts to pull this off today have failed. It's your once* in a lifetime 
> chance to record a GPS WNRO at the bit level. I'm looking for the raw serial 
> data stream binary dump; something re-playable in the future, not some ascii 
> output or screen shot.
> 
> /tvb
> 
> 
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Re: [time-nuts] GPS week rollover

[Mike Cook]

> Le 6 avr. 2019 à 17:53, jimlux  a écrit :
> 
> On 4/6/19 12:53 AM, Mike Cook wrote:
>> The OP doesn’t state where he got the  « quote » from, but IMHO it is wrong. 
>> As I understand it.
>> The GPS epoch started at 0h 1st June 1980
> 
> 6 Jan 1980 00:00:00 UTC

Just so… 01/06  tripped me

> 
> 
> 
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Re: [time-nuts] GPS week rollover

[Mike Cook]

The OP doesn’t state where he got the  « quote » from, but IMHO it is wrong. As 
I understand it.
The GPS epoch started at 0h 1st June 1980 and the week number roles at 1024 
week intervals at 0h GPS time. When a leap second is added its as if the clock 
stops for a second so GPS time will be in advance of UTC buy the number of leap 
seconds added.  18 leap seconds have been added to date, so 0h GPS 07 april 
2019 will be crossed at 23:59:42 UTC on April 6 as you indicated.


> Le 6 avr. 2019 à 00:40, Steve Olney  a écrit :
> 
> Just curious - WNRO is not an issue for me even if my GPS receivers are 
> affected - but I note that the time of rollover is being quoted as 23:59:59 
> UTC 6th April.
> 
> Wouldn't the time actually be 18 seconds earlier ? - i.e., 23:59:42 - due to 
> leap seconds ?
> 
> BTW - I'm not clear about GPS time vs UTC (which is probably relevant to the 
> above).  Any pointers to a clear explanation ?
> 
> Cheers
> 
> Steve
> 
> 
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"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
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Re: [time-nuts] GPS week rollover

[Mike Cook]

I checked my Garmin Emap, 1999 vintage IIRC. That is telling me that it is 
20/05/2014. 

I found this for Trimble which shows a number of devices affected by this which 
are commonly used bt timenuts.



Have a nice day

> Le 28 mars 2019 à 20:21, Steve - Home  a écrit :
> 
> 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 (and my iPhone). I haven’t had time to 
> look into it as I’m adjusting to “voluntary” retirement and trying to clear 
> out some excess stuff. 
> 
> Steve
> 
> 
> 
> 
>> On Mar 28, 2019, at 1:30 PM,   wrote:
>> 
>> Are we expecting any week rollover problems with the receivers we time
>> nuts like to play with???
>> 
>> Cheers,
>> 
>> Corby
>> 
>> 
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Re: [time-nuts] GPS week rollover

[Mike Cook]

Hi,
  I just got a heads up fro TomTom, saying my Go Live 825 bought 2012 « may » 
have WNRO problems after the April 6 rollover and invited me to update the 
firmware. I wouldn’t think it would affect the navigation, but it might brick 
the device. Unfortunately I can’t test it as it went to recycle 3 month ago . 
This could be an interesting week.
Mike

> Le 28 mars 2019 à 20:21, Steve - Home  a écrit :
> 
> 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 (and my iPhone). I haven’t had time to 
> look into it as I’m adjusting to “voluntary” retirement and trying to clear 
> out some excess stuff. 
> 
> Steve
> 
> 
> 
> 
>> On Mar 28, 2019, at 1:30 PM,   wrote:
>> 
>> Are we expecting any week rollover problems with the receivers we time
>> nuts like to play with???
>> 
>> Cheers,
>> 
>> Corby
>> 
>> 
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Re: [time-nuts] Frequency Ensemble

[Mike Cook]

> Le 17 mars 2019 à 02:16, Anton Moehammad via time-nuts 
>  a écrit :
> 
> Hi Everyone,I like to know if it possible to run let say 10 GPSDO, 16 Rb 
> clock together and take the average to control 1 "master clock" and have 
> better stability ?like what BIPM or NIST doing.

I think the answer to this is probably no but it would make a nice project. I 
say no because your GPSDO will already be benefiting the from the clocks in GPS 
constellation that are being steered, probably indirectly) by the UTC(NIST) 
clocks, steered by the AT1 time scale, created from a whole bunch of cesium , 
maser and optical clocks  , so your GPSDO is the equivalent of a master clock. 
This means that you only need one…well three to verify that one is not going on 
the blink. A GPSDO or Rubidium stability will probably be in the range of a few 
parts in 10^11 - 10^12. 
Measuring the phase offsets of a bunch go those and applying corrections to a 
another free running clock might buy you a zero but it is questionable I think. 
You are probably constrained by the quality of the chosen ‘master’. If there 
was a distinct advantage I would expect to see products on the market using 
this approach. I haven’t heard of any.

> I have search about ensemble system but I have no idea how much advantage I 
> get from some clock that I already have.Thank YouAnton 
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Re: [time-nuts] Bricked Garmin GPS 18x LVC

[Mike Cook]

Hi,
   I don’t know if you saw, but on the same page it is mentioned that it may 
un-brick itself after being left powered off for a long time - weeks.
Hope you get it back.

> Le 23 févr. 2019 à 09:41, Anthony Dunne  a écrit :
> 
> Hi everyone
> 
> I am hoping someone will have some information on how to unbrick a Garmin GPS 
> 18x LVC?
> 
> I was trying to rollback the firmware on the unit because I was experiencing 
> similar issues to what is described here:
> https://satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm
> 
> The unit kept randomly dropping the configuration I set up on it.
> 
> I could see no way to rollback the firmware from the current 4.00 to 3.90, so 
> I renamed the 3.90 firmware to make it 4.10 (bad idea I hear you say).
> 
> All seemed to go well with it erasing the previous firmware and installing 
> the "new" firmware, but now I think I have bricked the unit as I am getting 
> no response at all.
> 
> Is there any way that you know of to reset the unit, perhaps by connecting 
> two pins or something similar?
> 
> Thank-you
> 
> 
> 
> Anthony
> New South Wales
> Australia
> 
> 
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Re: [time-nuts] GN-GGB0710 GPS Antenna Mounting Thread

[Mike Cook]

The doc from a Chinese site says 
（Mounting Method）

5/8-11 Threaded installation 

 

> Le 14 févr. 2019 à 21:09, Skip Withrow  a écrit :
> 
> Hello Time-Nuts,
> As I have been playing with some dual-band GPS receivers, I decided to
> order a dual-band antenna to replace my permanent L1 antenna that I
> use for all the GPSDOs.  I purchased one of the Chinese TOPGNSS model
> GN-GGB0710 units.  Much smaller than the choke ring I currently have
> up (which uses a 1"-10TPI thread).
> 
> However, when I went down to the local hardware emporium to acquire
> parts to assemble a mounting bracket I seem to have run into an issue.
> A 5/8"-11 bolt appeared to be about right for the mounting threads,
> but bound after a turn or two.  So, I went over to the metric section
> and found an M16-2 bolt.  It started easily enough, but again bound
> after a couple of turns.
> 
> Back home I measured the thread pitch and got .08175 inches.  Turns
> out this is between the 5/8-11 thread (.0909") and the M16-2 thread
> (.0787").
> 
> I looked up the Trimble antenna mounting specs and they specify 5/8-11
> for their geodetic survey antennas.
> 
> Since the 5/8 hardware is a lot cheaper than the M16 I'll probably
> just use a 5/8 bolt and just screw it on reasonably tight and call it
> a day.  Just wanted to give the list a heads-up.  If there is a secret
> mounting thread out there please let me know.
> 
> Thanks,
> Skip Withrow
> 
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Re: [time-nuts] Ublox F9P multi-band GPS receiver

[Mike Cook]

So the ultimate question is: Do you need a F9P  in order to find the precise 
position of your F9T Antenna so that you can set up the F9T or is the F9T’s 
survey mode as accurate ( I doubt it as the doc gives position accuracy 2m ). 
Come to think of it, do you need three positioning receivers to be sure of your 
position? and three P9Ts so that you can use differential mode for best timing 
accuracy. I see no on board quantization error correction mentioned, nor 
quantization error reporting though I expect that is there, so for best 
accurracy that has to be added.  This looks as though it could get expensive.


> Le 24 janv. 2019 à 07:30, Dustin Marquess  a écrit :
> 
> This looks ideal to me:
> 
> https://www.u-blox.com/sites/default/files/RCB-F9T_ProductSummary_%28UBX-18069985%29.pdf
> 
> -Dustin
> 
> On Wed, Jan 23, 2019 at 8:01 PM Angus via time-nuts
>  wrote:
>> 
>> Hi,
>> 
>> It doesn't look like the F9P does anything special for timing - the
>> timing specs given in the F9T spec sheet are 5 ns (1-sigma, clear sky,
>> absolute mode) and +/- 4ns jitter, but for the F9P are 30ns RMS and
>> 60ns for 99%.
>> 
>> I think I want an F9T :)
>> 

In the year 1000 CE, the Persian Muslim scholar al-Biruni first used the term 
second in Arabic and defined it as 1⁄86,400 (that is, 1/(24 × 60 × 60)) of a 
mean solar day.


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Re: [time-nuts] leapseconds, converting between GPS time (week, second) and UTC

[Mike Cook]

AFIK no programming systems professing POSIX compliance implements Leap 
Seconds. There is however a timezone UTCLeapSeconds will allow this apparently.

>> t1.TimeZone = ‘UTCLeapSeconds'

Obviously youR TZ data base needs to have it and your Python needs to be at the 
required level;

My test didn’t work, maybe I am not at the right levels.

>>> t1 = datetime
>>> t1.timezone = 'UTCLeapSeconds'
>>> t1 = datetime.datetime(2016,12,31,23,59,58)
>>> dt = datetime.timedelta(seconds=1)
>>> print t1
2016-12-31 23:59:58
>>> print t1+dt
2016-12-31 23:59:59
>>> print t1+dt+dt
2017-01-01 00:00:00
>>> print t1+dt+dt+dt
2017-01-01 00:00:01

I guess the same facility exists for other programming systems MATLAB has it I 
believe. Google is your friend.

Mike

> Le 15 janv. 2019 à 15:54, jimlux  a écrit :
> 
> I'm working with a variety of things which work in UTC or GPS 
> week/millisecond, so we're doing a lot of conversion back and forth.
> (the spacecraft puts out time in week:millisecond, all the ground systems 
> processing is in UTC)
> 
> The question comes up when converting back and forth, and whether various 
> libraries handle leap seconds correctly.
> For now, I can use a hack of not computing back to 6 Jan 1980, but use an 
> epoch like 15 Dec 2018 (week 2031: 518,400.000 seconds) and hope there's no 
> leap second in the offing.
> 
> 
> For instance, in Python, if I do a datetime(2016,12,31,0,0,0) + 
> timedelta(hours=30) does it come out as 1/1/2017 6:00:00 or 5:59:59  (it 
> comes out 0600)
> 
> Similarly, does Excel's time formatting allow for some minutes having an 
> extra second, or does it just assume all minutes are 60 seconds.
> 
> I'll probably test it for the cases I'm interested in (Ruby, Python, Excel, 
> Matlab, Octave), but if someone else has already done it, then I've got 
> something to cross check against.
> 
> 
> (python does NOT know about leap seconds)
> 
> import datetime
> 
> d = datetime.datetime(2016,12,31)
> 
> dt = datetime.timedelta(hours=30)
> 
> d
> Out[4]: datetime.datetime(2016, 12, 31, 0, 0)
> 
> dt
> Out[5]: datetime.timedelta(1, 21600)
> 
> d+dt
> Out[6]: datetime.datetime(2017, 1, 1, 6, 0)
> 
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Re: [time-nuts] Trimble NetRS PPS output

[Mike Cook]

This doesn’t surprise me. Some years back I thought I could get better PPS 
resolution from a survey grade receiver but was disappointed to find on looking 
at specs of those available that PPS performance was generally worse than 
timing receivers, which of couse were much cheaper. It’s a no brainer now with 
sawtooth error correction available.

> Le 21 déc. 2018 à 05:05, Mark Sims  a écrit :
> 
> I recently got in a Trimble NetRS L1/L2/L2C survey grade receiver (Evil Uncle 
> Bob made me do it ;-)  ).   It consistently gives position error ellipses in 
> the 6mm range after post-processing 24 hours of data.
> 
> I had high hopes it would have a decent 1PPS output...  nope.  The PPS output 
> usually has a 40 nsec span (looks like a 25 MHz clock is in the device), with 
> some occasional 80 nsec or so spans.  The internal oscillator looks to be an 
> OCXO... the PPS does not show your typical wobbly PPS sawtooth error plots.  
> It is more like a pulse train with a slowly drifting duty cycle.
> 
> But the killer is the occasional (2-3 times per hour) "zingers" in the PPS 
> output.  These show up as a large negative error spike followed immediately 
> by an equal positive errors.   These "zingers" are typically in the 1-100 
> millisecond range.   I can't imagine how/why the circuitry would do this...
> 
> Lady Heather can now monitor the NetRS (and probably other receivers that can 
> output RT17 and Trimcomm data.   The NetRS does not respond to requests for 
> status and configuration commands over the RT17 ports, so a lot of 
> useful/informative stuff is not available.  It can write RINEX 
> files.___
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Re: [time-nuts] RF isolation requirements for multiple GPS receivers

[Mike Cook]

Hi,
   I am using Mini-Circuits ZN4PD1-50+. They are about 30dB in the GPS 
frequency band. I hang 4 receivers each off three of these mixing Motorola, 
Ublox, Trimble and Navspark and never had an issue. 
Mike

>  Le 27 nov. 2018 à 14:44, Dana Whitlow  a écrit :
> 
> I want to run about 4 separate GPS units of disparate
> manufacture from a single antenna.  My plan is to
> provide power for the antenna via a bias tee (power
> inserter) at the bottom end of the antenna's cable, then
> use an isolating splitter on the receiver side of the bias
> tee to split to the various receivers.
> 
> My question is: how much isolation between receivers
> is likely to be necessary?  Real life splitters are only
> so-so in isolation performance (15-25 dB), and may
> e significantly worse if the antenna's LNA's output is
> a poor match.  So I'm wondering if I'm going to need
> more amplifiers in the splitter's outputs just for the sake
> of adequate isolation between the GPS receivers.
> 
> Thanks,
> 
> DanaK8YUM
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Re: [time-nuts] Adoption of revision of the SI at CGPM #26

[Mike Cook]

Also, looks like Leap Seconds are with us for the forceable future if 
resolution B is adopted as is. 

> Le 17 nov. 2018 à 22:13, Poul-Henning Kamp  a écrit :
> 
> 
> In message <2b84b23d-b2b3-d9b6-d312-2585248cf...@rubidium.dyndns.org>, Magnus 
> Danielson writes:
> 
>> The Draft Resolution A "On the revision of the International System of
>> units (SI)" is found here:
>> https://www.bipm.org/utils/en/pdf/CGPM/Draft-Resolution-A-EN.pdf
> 
> I thought Resolution B was much more relevant for us: It defines TAI
> 
>   https://www.bipm.org/utils/en/pdf/CGPM/Convocation-2018.pdf
> 
> (page 34 forwards)
> 
> 
> -- 
> 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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Re: [time-nuts] 1PPS for the beginner

[Mike Cook]

> Le 14 août 2018 à 09:29, Mike Cook  a écrit :
> 
> Sorry about the previous blank mail. Finger jitter.
> 
> 
> 
>> Le 14 août 2018 à 04:29, Chris Caudle  a écrit :
>> 
>> On Mon, August 13, 2018 9:16 pm, Chris Burford wrote:
>>> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+ OCXO
>>> that I am using to steer a PRS10 RFS. I'm a little confused on where the
>>> 1PPS is coming from with respect to the GPSDO.
> 
> As Chris points out the 1PPS from a GPSDO will « generally » be derived from 
> the primary frequency and can show better performance than directly from a 
> GPS receiver.
> However this is becoming less and less true.
> If you look at the Oscilloquarz blurb for the Star 4+ ( I found some here 
> <http://pdf.directindustry.com/pdf/oscilloquartz-sa/star3-4/62169-330779.html#search-en-oscilloquartz-star-4>
>  ) , you will see that the phase stability (jitter) on the 1PPS output is +/- 
> 30ns when locked to GPS, an it has a timing grade GPS receiver. This is not 
> as good as other GPS modules now. 15ns is normal, with some less than half 
> that.
> The PRS10 has outstanding PLL control already. The SRS product doc gives +/- 
> 10ns accuracy with +/-1ns resolution.   
> I don’t think that you are buying much with disciplining the PRS10 with a 
> GPSDO 1PPS. Do you have any TIC measurements in this config to compare with a 
> direct GPS 1PPS feed? 
> 

I forgot to mention one other thing which may be of interest to some. The 1PPS 
wave form output from the PRS10 is pretty mediocre. I put the details in 
another post here sometime back.
The Star4 spec is +/- 10ns, something I can only get from my PRS10s with a 
74HC7001 shaper. 


> 
>> 
>> A GPS disciplined oscillator contains a GPS receiver which outputs 1PPS
>> based on receiving the GPS signals and calculating the position  + time
>> equation. That PPS signal is noisy in time, it jitters around relative to
>> the ideal 1 second period.  The GPSDO implements a long time constant PLL
>> to synchronize the output of the OCXO to the long term average frequency
>> and phase of the GPS PPS, so what you see externally is 10MHz directly
>> from the OCXO, 1 Hz (PPS) which is divided down from the 10MHz OCXO, and
>> those are controlled by a PLL so that long term the phase of the PPS
>> divided down from the OCXO follows the PPS calculated by the GPS receiver,
>> but with lower jitter.
>> 
>> -- 
>> Chris Caudle
>> 
>> 
>> 
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> are giving  power to.
> 
> 
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Re: [time-nuts] 1PPS for the beginner

[Mike Cook]

Sorry about the previous blank mail. Finger jitter.



> Le 14 août 2018 à 04:29, Chris Caudle  a écrit :
> 
> On Mon, August 13, 2018 9:16 pm, Chris Burford wrote:
>> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+ OCXO
>> that I am using to steer a PRS10 RFS. I'm a little confused on where the
>> 1PPS is coming from with respect to the GPSDO.

As Chris points out the 1PPS from a GPSDO will « generally » be derived from 
the primary frequency and can show better performance than directly from a GPS 
receiver.
However this is becoming less and less true.
If you look at the Oscilloquarz blurb for the Star 4+ ( I found some here 

 ) , you will see that the phase stability (jitter) on the 1PPS output is +/- 
30ns when locked to GPS, an it has a timing grade GPS receiver. This is not as 
good as other GPS modules now. 15ns is normal, with some less than half that.
The PRS10 has outstanding PLL control already. The SRS product doc gives +/- 
10ns accuracy with +/-1ns resolution.   
I don’t think that you are buying much with disciplining the PRS10 with a GPSDO 
1PPS. Do you have any TIC measurements in this config to compare with a direct 
GPS 1PPS feed? 


> 
> A GPS disciplined oscillator contains a GPS receiver which outputs 1PPS
> based on receiving the GPS signals and calculating the position  + time
> equation. That PPS signal is noisy in time, it jitters around relative to
> the ideal 1 second period.  The GPSDO implements a long time constant PLL
> to synchronize the output of the OCXO to the long term average frequency
> and phase of the GPS PPS, so what you see externally is 10MHz directly
> from the OCXO, 1 Hz (PPS) which is divided down from the 10MHz OCXO, and
> those are controlled by a PLL so that long term the phase of the PPS
> divided down from the OCXO follows the PPS calculated by the GPS receiver,
> but with lower jitter.
> 
> -- 
> Chris Caudle
> 
> 
> 
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Re: [time-nuts] 1PPS for the beginner

[Mike Cook]

> Le 14 août 2018 à 04:29, Chris Caudle  a écrit :
> 
> On Mon, August 13, 2018 9:16 pm, Chris Burford wrote:
>> I have a (generic?) GPSDO which contains an Oscilloquartz STAR 4+ OCXO
>> that I am using to steer a PRS10 RFS. I'm a little confused on where the
>> 1PPS is coming from with respect to the GPSDO.
> 
> A GPS disciplined oscillator contains a GPS receiver which outputs 1PPS
> based on receiving the GPS signals and calculating the position  + time
> equation. That PPS signal is noisy in time, it jitters around relative to
> the ideal 1 second period.  The GPSDO implements a long time constant PLL
> to synchronize the output of the OCXO to the long term average frequency
> and phase of the GPS PPS, so what you see externally is 10MHz directly
> from the OCXO, 1 Hz (PPS) which is divided down from the 10MHz OCXO, and
> those are controlled by a PLL so that long term the phase of the PPS
> divided down from the OCXO follows the PPS calculated by the GPS receiver,
> but with lower jitter.
> 
> -- 
> Chris Caudle
> 
> 
> 
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Re: [time-nuts] NIST

[Mike Cook]

> Le 13 août 2018 à 11:09, Dana Whitlow  a écrit :
> 
> Craig,
> 
> The original main reason for WWVB had nothing to do with syncing our
> "atomic"
> wristwatches and clocks.  It was for keeping local frequency standards
> honest, for
> which continuous coverage throughout the day and night was desirable (if not
> always achievable).  But for that application, a one-shot daily sync was
> not really
> good enough (for most users).  Stations that used WWVB for serious purposes
> used
> outdoor electrostatically-shielded loop antennas, usually up on the roof,
> to get
> enough signal enough of the time.

 This function of disseminating a frequency reference is not mentioned at 
all in the NIST request for information document, nor in  Microsemi’s response.
I expect most calibration labs have their own 5071As  but that is not quite the 
same as having a NIST traceability. My Certificate of Calibration from SRS for 
one of my PRS10 rubidium standards indicates:
«  Stanford Research Systems, Inc. certifies that this instrument has been 
calibrated to manufacturer specifications and accuracy at an ambient 
temperature of 23° +/- using instruments and standards which are traceable to 
the National Institute of Standards and Technology. «
I expect the big labs send their instruments of to Boulder for calibration, but 
there must be some smaller outfits still phase locking off WWVB. We in Europe 
have MSF, DCF and TDF for which off air frequency references are /were 
available and which are probably still being used.
How would this frequency traceability work if WWVB/WWVH pass to a private 
enterprise?   



> 
> 
> On Sun, Aug 12, 2018 at 10:40 AM, Craig Kirkpatrick 
> wrote:
> 
>> I agree with Bob that shutting down WWVB would not go over well with the
>> voters but losing WWV and WWVH will mainly be noticed only by HAMs.
>> 
>> Dana, I’m puzzled by what you wrote.  I have 8 clocks and 2 wristwatches
>> that sync with WWVB.  When band conditions are poor they miss a sync for a
>> day but still they are good quartz clocks so the time readout is still OK.
>> When the band conditions are good again they sync up once per day usually
>> around 2am (according to the manual for my wristwatch).  I can easily tell
>> the sync status on all but 4 of my clocks and they sync successfully about
>> 90% of the overnight times.  My wristwatches are Citizen models that charge
>> by solar which is nice since I have a perfectly in sync watch that never
>> needs to be opened to change a battery.
>> 
>> I do like the idea of a GPS to WWVB timecode radio transmitter.  I think
>> that would sell well to folks on the fringe of coverage for WWVB such as
>> Florida, Hawaii, and Alaska or other parts of the globe.  I’ve found the
>> real limitation to reception of WWVB is local 60kHz noise in the home.  For
>> instance if I have a fan running to cool things in my shack then my WWVB
>> clocks will not sync successfully.
>> 
>> I hope Nick Sayer is reading this and getting the idea to make a GPS to
>> WWVB timecode radio transmitter, clever gent that he is.  :-)
>> 
>> Best Wishes,
>> Craig
>> KI7CRA
>> 
>>> On Aug 11, 2018, at 7:48 PM, Dana Whitlow  wrote:
>>> 
>>> I fear the worst.  The line in the website simply stated something like
>>> "shutting down
>>> the transmitters in Colorado and Hawaii", which would seem to include the
>>> whole
>>> enchilada.
>>> 
>>> For the wall clocks, GPS should work well if people are willing to go to
>>> battery-
>>> backed AC power.  But not so good for wristwatches, where the expectation
>>> is to
>>> run at uW power levels.  I for one would be very irritated at having to
>>> take my watch
>>> off my wrist and put it on a charging stand every night.  So if this
>>> shutdown comes
>>> to pass, I'll be looking for an inexpensive GPS-to-WWVB converter, or at
>>> least
>>> plans for building one.
>>> 
>>> Dana
>>> 
>>> 
>>> On Sat, Aug 11, 2018 at 8:12 PM, Bob Albert via time-nuts <
>>> time-nuts@lists.febo.com> wrote:
>>> 
 With any luck, the current administration will successfully push the USA
 down technically.  Denying global warming, shutting off time signals,
>> and
 so on, is great stuff.
   On Saturday, August 11, 2018, 6:10:12 PM PDT, Bob kb8tq <
>> kb...@n1k.org>
 wrote:
 
 Hi
 
 One would *guess* that stopping WWVB (and killing mom and pop’s “atomic
 clocks”) would not be a reasonable thing to do.
 It gets a lot of voters mad. I doubt that very many voters (percentage
 wise) would notice WWV and WWVH going away ….
 
 Bob
 
> On Aug 11, 2018, at 9:00 PM, jimlux  wrote:
> 
> On 8/10/18 12:45 PM, Robert LaJeunesse wrote:
>> I'd say it does get more detailed, with the $49M in cuts described
 generally in groups here:
>> https://www.nist.gov/director/fy-2019-presidential-budget-
 request-summary/fundamental-measurement-quantum-science-and
>> One item: "-$6.3 million supporting fundamental measurement

Re: [time-nuts] Looking for PZT3904T1G transistors

[Mike Cook]

Newark.com  869 in stock , min 1, must 1


> Le 4 juil. 2018 à 14:25, John Ackermann N8UR  a écrit :
> 
> Dear Friends --
> 
> I need to find 150+ pieces of transistor type PZT3904T1G, SOT223 package 
> (with heatsink tab), equivalent to Digikey PZT3904T1G0SCT-ND.
> 
> These are used in the TNS-BUF buffer amplifier that we're trying to 
> manufacture, and they seem to be on worldwide shortage; none of the usual 
> sources can provide them prior to November (and that's a slip from the 
> originally-quoted August ship date).
> 
> I've found one source (Rochester Electronics) that seems to have them, but 
> they have a minimum order of 2778 pieces, which is a bit of overkill compared 
> to the 150 we need to build 50 boards.  We'll use that source if the other 
> options turn up dry.
> 
> When I mentioned this previously, a couple of folks said they might have some 
> stashed away.  I'd like to follow up on that offer -- if you can supply some 
> of these (ideally 150, but less will still help), please contact me off-list 
> at jra at febo dot com.
> 
> Thanks!
> John
> 
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