[time-nuts] mailing list moderation, STATUS, May 2018

[Tom Van Baak]

FYI -- you may have noticed that earlier this week we turned off time-nuts list 
'moderation'. This means postings now immediately go to the entire group and 
archives without review or delay [1].

So be extra careful about what you post, and also to whom, and how often. When 
the list is 'open' like this you may see an increase in posting mistakes, such 
as html mix-ups, suspect URLs, private email sent to a public list, off-topic 
postings, blank postings, duplicate postings, admin questions.

In the past year we have seen issues with how some email clients handle 
replies. Before you hit send, double check the To and Cc lines to make sure 
there is only one recipient. A public posting or reply to time-nuts should go 
to time-nuts@febo.com alone. An off-list personal reply to someone should go to 
them alone. Any other combination of To/Cc addresses is likely a mistake.

As always on time-nuts, good questions *specifically related to precise time & 
frequency* are always welcome, especially from newcomers [2]. The list works 
best when replies are based on our collective experience and actual 
experimentation, not guesses or quick off-the-cuff comments. The list breaks 
down when threads veer off-topic, or when time-nuts acts like social media, or 
when the sheer volume of postings pushes people away. Please do your part to 
keep the SNR very high on this list.

List administrative questions or comments should go directly to John 
(j...@febo.com) or Tom (t...@leapsecond.com) rather than to the entire 1800 
member list.

Thanks,
/tvb

[1] Some postings are still held for review: attachments over 1 MB (to prevent 
big mistakes) and new members (to deal with off-topic or email client issues).

[2] An introduction to time-nuts as well as many helpful links: 
http://leapsecond.com/time-nuts.htm


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Re: [time-nuts] Question about frequency counter testing

[Tom Van Baak]

Azelio, the problem with that approach is that the more stable and accurate 
your DUT & REF sources the less likely there will be transitions, even during 
millions of samples over one second.

A solution is to dither the clock, which is something many old hp frequency 
counters did. In other words, you deliberately introduce well-designed noise so 
that you cross clock edge transitions as *much* as possible. It seems 
counter-intuitive that adding noise can vastly improve your measurement, but in 
the case of oversampling counters like this, it does.

/tvb

- Original Message - 
From: "Azelio Boriani" 
To: "Discussion of precise time and frequency measurement" 
Sent: Friday, April 27, 2018 7:39 AM
Subject: Re: [time-nuts] Question about frequency counter testing


You can measure your clocks down to the ps averaged resolution you
want only if they are worse than your one-shot base resolution one WRT
the other. In a resonable time, that is how many transitions in your
2.5ns sampling interval you have in 1 second to have a n-digit/second
counter.

On Fri, Apr 27, 2018 at 4:32 PM, Azelio Boriani
 wrote:
> Yes, this is the problem when trying to enhance the resolution from a
> low one-shot resolution. Averaging 2.5ns resolution samples can give
> data only if clocks move one with respect to the other and "cross the
> boundary" of the 2.5ns sampling interval. You can measure your clocks
> down to the ps averaged resolution you want only if they are worse
> than your one-shot base resolution one WRT the other.
>
> On Fri, Apr 27, 2018 at 3:38 PM, Bob kb8tq  wrote:
>> Hi
>>
>> Consider a case where the clocks and signals are all clean and stable:
>>
>> Both are within 2.5 ppb of an integer relationship. ( let’s say one is 10
>> MHz and the other is 400 MHz ). The amount of information in your
>> data stream collapses. Over a 1 second period, you get a bit better than
>> 9 digits per second.  Put another way, the data set is the same regardless
>> of where you are in the 2.5 ppb “space”.
>>
>> Bob
>>
>>
>>
>>> On Apr 27, 2018, at 5:30 AM, Hal Murray  wrote:
>>>
>>>
>>> olegsky...@gmail.com said:
 No, it is much simpler. The hardware saves time-stamps to the memory at 
 each
 (event) rise of the input signal (let's consider we have digital logic 
 input
 signal for simplicity). So after some time we have many pairs of {event
 number, time-stamp}. We can plot those pairs with event number on X-axis 
 and
 time on Y-axis, now if we fit the line on that dataset the inverse slope of
 the line will correspond to the estimated frequency.
>>>
>>> I like it.  Thanks.
>>>
>>> If you flip the X-Y axis, then you don't have to invert the slope.
>>>
>>> That might be an interesting way to analyze TICC data.  It would work
>>> better/faster if you used a custom divider to trigger the TICC as fast as it
>>> can print rather than using the typical PPS.
>>>
>>> --
>>>
>>> Another way to look at things is that you have a fast 1 bit A/D.
>>>
>>> If you need results in a second, FFTing that might fit into memory.  (Or you
>>> could rent a big-memory cloud server.  A quick sample found 128GB for
>>> $1/hour.)  That's with 1 second of data.  I don't know how long it would 
>>> take
>>> to process.
>>>
>>> What's the clock frequency?  Handwave.  At 1 GHz, 1 second of samples fits
>>> into a 4 byte integer even if all the energy ends up in one bin.  4 bytes, 
>>> *2
>>> for complex, *2 for input and output is 16 GB.
>>>
>>>
>>> --
>>> These are my opinions.  I hate spam.
>>>
>>>
>>>
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>>
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Re: [time-nuts] Question about frequency counter testing

[Tom Van Baak]

> That might be an interesting way to analyze TICC data.  It would work 
> better/faster if you used a custom divider to trigger the TICC as fast as it 
> can print rather than using the typical PPS.

Hi Hal,

Exactly correct. For more details see this posting:
https://www.febo.com/pipermail/time-nuts/2014-December/089787.html

That's one reason for the 1/10/100/1000 Hz PIC divider chips -- to make 
measurements at 100PPS instead of 1PPS.

JohnA could have designed the TAPR/TICC to be a traditional two-input A->B Time 
Interval Counter (TIC) like any counter you see from hp. But instead, with the 
same hardware, he implemented it as a Time Stamping Counter (TSC) pair. This 
gives you A->B as time interval if you want, but it also gives you REF->A and 
REF->B as time stamps as well.

You can operate the two channels separately if you want, that is, two 
completely different DUT measurements at the same time, as if you had two TIC's 
for the price of one. Or you can run them synchronized so that you are 
effectively making three simultaneous measurements: DUTa vs. REF vs. DUTb vs.

This paper is a must read:

Modern frequency counting principles
http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf

See also:

New frequency counting principle improves resolution
http://tycho.usno.navy.mil/ptti/2005papers/paper67.pdf

Continuous Measurements with Zero Dead-Time in CNT-91
http://www.testmart.com/webdata/mfr_promo/whitepaper_cnt91.pdf

Time & Frequency Measurements for Oscillator Manufacturers using CNT-91
http://www.testmart.com/webdata/mfr_promo/whitepaper_osc%20manu_cnt91.pdf

Some comments and links to HP's early time stamping chip:
https://www.febo.com/pipermail/time-nuts/2017-November/107528.html

/tvb

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Re: [time-nuts] Cheap jitter measurements

[Tom Van Baak]

Hi Gary,

> As requested, here is my raw data: http://pi5.rellim.com/1d.log.gz

I'm having a close look. These are quite a few bad data points and that partly 
explains why your ADEV plots were off. Trim the file at, say, line 71000 and 
try again; the results will be much better.

I'll post an in-depth report later. There are interesting things in the data. 
You're going to have lots of fun with your new TICC and GPS boards...

> I'd love to use TimeLab, or Stable32.  But they seem to be closed source,

Nope, not closed source.

John Miles includes all the source in the TimeLab installation.
http://www.ke5fx.com/timelab/readme.htm
Ask him for a zip of the installation if you can't/won't run the setup exe.

Bill Riley very recently donated his Stable32 source tree to IEEE and so that 
tool joins the club too.
https://ieee-uffc.org/frequency-control/frequency-control-software/stable32/
Not sure where the source repo is but someone on the list will know, or know 
when it will be ready. Long thread here:
https://www.febo.com/pipermail/time-nuts/2018-January/108320.html

Someone who routinely uses these apps on non-Windows or non-x86 machines can 
comment on how to do it.

/tvb

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[time-nuts] nuts about position

[Tom Van Baak]

List -- I had a recent query by a researcher who would like to pinpoint the 
location of his telescope(s) within 0.3 meters. Also (he must be a true 
scientist) he wants to do this on-the-cheap. He may have timing requirements as 
well, but that's another posting.

So I toss the GPS question to the group. Surely some of you have crossed the 
line from precise time to precise location?

How easy, how cheap, how possible is it to obtain 0.3 m accuracy in 3D position?

When we run our GPSDO in survey mode how accurate a position do we get after an 
hour, or even 24 or 48 hours? And here I mean accurate, not stable. Have any of 
you compared that self-reported, self-survey result against an independently 
measured professional result or known benchmark?

Do you know if cheap ublox 5/6/7/8 series receivers are capable of 1 foot 
accuracy given enough time?

If not, what improvement would -T models and RINEX-based web-service 
post-processing provide?

It that's still not close enough to 0.3 m, is one then forced to use more 
expensive multi-frequency (L1/L2) or multi-band (GPS, GLONASS, Galileo) to 
achieve this level of precision? If so, how cheaply can one do this? Or is the 
learning curve more expensive than just hiring an survey specialist to make a 
one-time cm-level measurement for you?

Something tells me 1 foot accuracy in position is possible and actually easier 
than 1 ns accuracy in time. I'm hoping some of you can help recommend 
solution(s) to the researcher's question or shed light on this interesting 
challenge.

Thanks,
/tvb

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Re: [time-nuts] Cheap jitter measurements

[Tom Van Baak]

Hi Gary,

> A little coding later and there are nice plots.  They were compared to
> the output of tvb's adev.c program.  Results are similar.

Whoa there cowboy. That doesn't mean it's right. Comments:

> gps.png looks as expected.

1. No, it would appear something is wrong with your data. You show the ADEV for 
tau 1 s to be about 1e-2. That seems off by a factor of a million. It's 
probably not your reference, or your TICC, or the NEO-M8M, but something in how 
you are scaling the data? or glitches in your data? Hard to say without more 
info.

2. The artifacts at the end of the traces are weird. That's either too small a 
statistics sample or you have one or more bad data points that are ruining your 
data set.

3. It's best not to show ADEV or MDEV on the same plot as TDEV. They are 
different concepts and have different units. Also use ADEV as a label not OADEV.

4. At this stage of being a time-nut, it's best not make canned ADEV plots 
without first making phase and frequency plots. ADEV is just a statistic and 
you can feed it garbage and it will still happily compute numbers. By plotting 
phase (or phase residuals) and frequency (or relative frequency error) your eye 
can catch most of the bugs that occur to first-time ADEV'ers. Creating phase 
and frequency plots also makes you aware of the units, scale, and magnitude of 
your data, something you can use as a sanity check.

5. Since you are using batch tools instead of interactive tools, I suggest 
showing the first few and last few raw data lines from the TICC. Also the first 
and last few lines of the data that you input to your ADEV calculation. Or just 
post the raw data. This is helpful to debug bad plots like this.

> GPSTLXO.png shows the quality of the JL part,

1. Hmm, that just looks like some self-test data. I'm suspicious when I see 
1e-17 MDEV numbers. Something's not right. The TICC is nice, but not that good.

2. Wait, you're using the JL 10 MHz as the TICC reference and then you're 
measuring the JL 1PPS with the TICC? So that's not really a measurement of the 
"quality of the JL part"; it's more just a self-test of a TICC channel.

3. Once you get correct-looking ADEV plots for NEO-M8M and JL then we can talk 
about what effect (if any) using Rb as a TICC reference will have. Remember 
that for time interval measurements the quality of the reference is not that 
important.


I strongly, pretty please, strongly advise you to use TimeLab for a while 
before you roll your own tools and plots. That is, "learn to drive before you 
design your own car". I know you have a grumpy old man aversion to using 
Windows, but lots of people on the list seem to run TimeLab easily on their 
non-Windows systems.

If nothing else, at least look at what TimeLab does. The PDF user manual is a 
superb tutorial on working with time & frequency data.

Anyway, a good start to your NTP measurement project. Thanks for posting.

/tvb


- Original Message - 
From: "Gary E. Miller" 
To: "time-nuts" 
Sent: Tuesday, April 24, 2018 8:45 PM
Subject: Re: [time-nuts] Cheap jitter measurements


Time-nuts!

I went ahead and bought the TAPR-TICC, it is a very impressive
instrument.  For this setup it is combined with a Jackson Labs
GPSTLXO as the 10MHz reference.  The JL is a GPS disciplined temperature
compensated crystal oscillator.

The first setup uses the TAPR-TICC in Period mode, outputting the PPS
period individually for channel A and channel B.

Channel A is the PPS of a plain u-blox NEO-M8N.  Channel B is the
PPS of the JL GPSTLXO.

Simple to get the cycle times from the USB serial port.

Then I grabbed a copy of the easy to use Python Allantools.
https://github.com/aewallin/allantools

A little coding later and there are nice plots.  They were compared to
the output of tvb's adev.c program.  Results are similar.

Results are attached.  gps.png is the plain NEO-M8N.  GPSTLXO is the
JL part.

gps.png looks as expected.  GPSTLXO.png shows the quality of the JL part,
but does have some odd divots in the plot.  Maybe artifacts of using the
PPS derived from the reference 10MHz?  Or an artifact of the 10e6 divider?

There are adev's of Rb standards here: http://www.ke5fx.com/rb.htm

My guess is that the oadev at 1s would be about 50x better with
a Rubidium?  But similar at 10k seconds?

Comments?

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

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin






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Re: [time-nuts] WWVB information

[Tom Van Baak]

So Doug's Spectracom WWVB receiver shows a green lock status. I didn't believe 
it, but he sent a photo. I then tried it here and the same thing happens to me. 
It's very suspicious because we know these old carrier phase WWVB receivers 
don't work with the enhanced WWVB broadcast format.

Instead of trusting the green light I measured the 5 MHz output of the 
WWVB-disciplined receiver using a hp 53132A. Here's an example of 1 second 
readings with no antenna (no lock):
431.22296  Hz
431.22650  Hz
431.22709  Hz
431.209453 Hz
431.21235  Hz
STD DEV: 0.007968 Hz

You see a free-running undisciplined OCXO. Not very accurate but very stable.

Then I connected the WWVB antenna. Within seconds the green lock light came on. 
The readings looked like:
494.676217 Hz
514.45065  Hz
466.61447  Hz
463.27949  Hz
471.40319  Hz
STD DEV: 15.853246 Hz

You see that the OCXO has been steered closer to 5 MHz, but the stability is 
horrible.

Lastly, just to check the system was working, I applied a 60 kHz carrier near 
the antenna using a hp 3325B. The readings look like:
499.9693  Hz
500.0199  Hz
500.0202  Hz
499.9693  Hz
499.9998  Hz
STD DEV: 0.02355 Hz

In this case very accurate and quite stable.

ADEV plot of all three runs is attached.

So my conclusion is the green lock light is false. The Spectracom really isn't 
locking to the carrier. It's trying hard, but the new phase encoding keeps this 
from happening. Someone can take a look at the block diagram or schematic and 
explain why the circuit gets fooled into thinking there is lock when there 
really isn't. Look for Spectracom 8161 or 8164 on ko4bb's manual site.

The one mystery is why this false green only started a week ago for Doug. If 
any of you have Spectracom WWVB receivers, fire then up and see what happens. I 
think I'll keep mine going for a few days or months and see if the false green 
ever goes out.

/tvb
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Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

[Tom Van Baak]

Amazing news... 1.2.3.

1) Many of you know that pulsars are weird astronomical sources of periodic 
signals. Some are so accurate that they rival atomic clocks for stability! 
True, but I don't have a 100 foot antenna at home so I'll take their word for 
it. Plus, you have to account for a myriad of PhD-level corrections: from 
earth's rotation to general relativity. And, like quartz or rubidium clocks, 
pulsars drift (as they gradually slow down). Precision timing is not easy. If 
you poke around the web you can find numerous articles describing their 
detection and measurement and exploring their use as reference clocks, both 
here and potentially for deep-space timekeeping.

2) If you do a lot of clock measurement at home then you know the dark side of 
working with precision clocks. There are signal quality issues, measurement 
resolution issues, reference stability limitations, offset, drift, phase jumps, 
frequency jumps, missed or extra cycles, glitches, etc. For example, quartz 
oscillators (depending on make / model / luck) can exhibit frequency jumps; 
i.e., without warning they just change frequency without your permission. Ok, 
maybe not by a lot, but enough to notice; perhaps enough to cause trouble to 
any naive GPSDO PID algorithm that assumes steady state from the oscillator you 
thought was stable.

3) Now the exciting part! Fellow time-nut Jim Palfreyman studies pulsars. 
You've seen postings from him now and then over the years. It turns out Jim is 
the first person to catch a pulsar in the act of a frequency jump. After 3 
years of continuous searching! This is really cool. Just amazing. You can't get 
more time nutty than this. And it just got published in Nature. It's a perfect 
never-give-up, i-eat-nanoseconds-for-breakfast, time nut thing to do. I am so 
impressed.

To quote Jim:

On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched. The
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in error.

So sceptically I logged in, and ran the test again. It was genuine!
The excitement was incredible and I stayed up all night analysing the data.

What surfaced was quite surprising and not what was expected. Right
as the glitch occurred, the pulsar missed a beat. It didn't pulse.

Here is a very readable description of his discovery:

http://theconversation.com/captured-radio-telescope-records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815

And also the official Nature article with all the juicy, peer-reviewed details:

https://rdcu.be/LfP0

So congratulations to Jim. I will think of him next time my 10811A quartz 
oscillator does a frequency jump or next time my 60 Hz mains frequency monitor 
skips a cycle...

If you have comments or questions feel free to send them to Jim directly (see 
Cc: address). Perhaps he can summarize the questions and his answers in a 
posting to time-nuts soon.

/tvb

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Re: [time-nuts] WWVB information

[Tom Van Baak]

I've been talking with Doug to better understand why his Spectracom WWVB 
receiver shows the green lock indicator. This receiver should not work given 
the enhanced WWVB modulation we've had since 2012. Fortunately he has chosen 
not to touch anything while we ponder this.

Meanwhile I pulled out some Spectracom gear (8164) and was able to repro his 
green lock! But the 10 MHz output is very unstable so I'm pretty sure it is not 
locking at all. Looking at the schematic the green indicator seems primitive. 
So "lock" may not really mean it has robustly locked to the carrier. More 
details to follow.

If any of you have Spectracom WWVB 816x or 817x receivers you might want to try 
them too.

/tvb

- Original Message - 
From: "Martin VE3OAT" 
To: 
Cc: "Doug Millar" 
Sent: Thursday, April 12, 2018 5:12 PM
Subject: Re: [time-nuts] WWVB information


> Hi, Doug,
> How is your 8161 doing now?  Still synced properly?  Should I bring my 
> 8164 up from the basement?  I was so disappointed when WWVB changed 
> their modulation.  Thanks for any encouragement.
> 73,
> ... MartinVE3OAT
> 
> 
> On Wed, 11 Apr 2018 16:28:41 Doug Millar wrote :
> 
> > Hi, My Spectracom 8161 comparator and 8171A clock are chugging
> > right along in sync with the proper time. I have only looked at
> > the digital LED output and it is within one second of my other
> > WWVB  clocks.  Seems like magic. It came in synch about two
> > weeks ago and stayed there. I haven't changed anything in my
> > lab or moved the units. Antenna is still the same.
> > Pictures available. Doug K6JEY
> 
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[time-nuts] time nuts overflow / gentle reminder

[Tom Van Baak]

All -- This is a reminder that time-nuts is a technical mailing list.

Please be careful with your replies. If you read, compose and hit send within 
30 seconds, it's likely the post will sound like it belongs on social media 
instead of time-nuts.

Our list works best when postings are well thought out, technical and 
educational. With 1800 members it doesn't scale well to use the list for 
off-the-cuff comments or speculation or tangents upon tangents.

When a posting arrives that's off-topic or is missing substantial technical 
content I usually send a private email to explain why it might not be suitable. 
Be we've had so many recently that I don't have time to engage with each member 
personally. So if your post goes missing or if you get an automated rejection 
notice from the server don't take it personally; we're just trying raise the 
bar after a gradual drift in quality. As John says, time nuts is a low volume, 
high SNR list.

Send list admin questions / comments to us at time-nuts-ow...@febo.com

Thanks,
/tvb
Moderator, www.leapsecond.com/time-nuts.htm


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Re: [time-nuts] suggestions on getting 24 Mhz ?

[Tom Van Baak]

Pete,

Is your goal to make SDR frequency measurements? One solution: grab any 24 MHz 
oscillator you find but use a counter with known accurate timebase 
(Rb,Cs,GPSDO) to continuously record its actual frequency. Don't adjust the 
frequency; just record it. Then, apply those readings as corrections to your 
SDR measurements. This software (or pencil & paper) correction method should 
give equivalent results as an atomic- or GPS-disciplined 24 MHz timebase.

/tvb

- Original Message - 
From: "Pete Lancashire" 
To: "Discussion of precise time and frequency measurement" 
Sent: Wednesday, April 11, 2018 3:00 AM
Subject: [time-nuts] suggestions on getting 24 Mhz ?


> Needed for SDR project as external clock source.
> 
> -pete
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Re: [time-nuts] WWVB Time

[Tom Van Baak]

> Hi, all of a sudden my Symmetricom comparator/clock has been locking up on 
> time.
> It has been about a week so far. Did they change the code? Anyone else seeing 
> that?
> Doug K6JEY

Hi Doug,

That would be too good to be true. I asked NIST just now and they report: "We 
have not changed the code or power level. All things remain the same."

So let's debug this on your end.
- What make/model WWVB receiver are you using?
- Can you check the accuracy of the time or frequency output against GPS / 
GPSDO. Is it NIST accurate or a bad copy of 60 kHz?
- Did you power-up any new instrument in the past week, one that might cause 60 
kHz harmonics?
- Can you check with 'scope or spectrum analyzer what your environment looks 
like near 60 kHz?
- Do you have a curious neighbor who is experimenting with a WWVB simulator...

/tvb

- Original Message - 
From: "Doug Millar via time-nuts" 
To: 
Sent: Tuesday, April 10, 2018 1:23 PM
Subject: [time-nuts] WWVB Time


Hi, all of a sudden my Symmetricom comparator/clock has been locking up on 
time. It has been about a week so far. Did they change the code? Anyone else 
seeing that? Doug K6JEY
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Re: [time-nuts] Cheap jitter measurements

[Tom Van Baak]

Dan,

I wrote a PC-based time-stamping counter (TSC) tool that uses a serial port and 
QueryPerformanceCounter:

www.leapsecond.com/tools/pctsc.exe (Win32)
www.leapsecond.com/tools/pctsc.c (source)

Give it a try.

/tvb

- Original Message - 
From: "Dan Kemppainen" 
To: 
Sent: Tuesday, April 10, 2018 6:59 AM
Subject: Re: [time-nuts] Cheap jitter measurements


Hi,

Don't know how good they are, but there are two functions in the 
kernel32 lib in windows that are related to a cpu performance counter, 
QueryPerformanceCounter and QueryPerformanceFrequency. (Maybe Linux has 
similar?)

Anyway, on most systems the frequency reported is the raw cpu clock. 
(Couple of Ghz Range numbers, My current system is reporting 3,320,458 
Hz, windows7.) Supposedly these are low latency functions. It may not 
offer a perfect solution, but at least it gives you 'low latency' access 
to a high speed counter.

Maybe it's possible to timestamp incoming PPS pulses with this (assuming 
they're triggering an interrupt), and learn something neat.

Some of this is subject to change with windows versions:

https://msdn.microsoft.com/en-us/library/windows/desktop/dn553408(v=vs.85).aspx

Dan




On 4/10/2018 8:01 AM, time-nuts-requ...@febo.com wrote:
> kb...@n1k.org  said:
>> The kernel clock comes from the CPU clock. That CPU clock is phase locked to
>> a crystal. If you have a CPU that is driven by a VCXO that is a*very*
>> unusual CPU board.  The crystal runs at an arbitrary frequency. That gives
>> you edges that are unlikely to happen ���right on the second���.
> I was assuming the CPU clock was fast enough that reading a cycle-count
> register and converting to ns would be within a ns which is the resolution of
> the clock.
> 
> That's obviously not true for low end SOC type setups.  A Pi-1 runs at 700
> MHz.  The Pi 3 is up to 1.4 GHz.
> 
> 
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Re: [time-nuts] ADEV dead time w/ HP 53131A & TimeLab

[Tom Van Baak]

Dave,

> My research concerns oscillator drift on time scales of ~1ms to ~10s, so
> I'm guessing the 53131A with its 5-130ms of dead time isn't suitable for
> what I'm trying to measure.

True. Try a fancy TIA (time interval analyzer) or MDA (modulation domain 
analyzer) instead.

Or consider a high-res (tens of ps) timestamping counter capable of 1000 
samples per second. The Pendulum CNT-91 may work. Also look into the Agilent 
53230A which has a zero deadtime timestamping mode. The venerable SR620 is also 
capable of 1 kHz measurement rate, but I'm not sure if that's internal sampling 
or sustained data rate via GPIB. The TICC (designed by JohnA, distributed by 
TAPR) would also work to 1 kHz sampling if you rewrote the Arduino code.

What kind of oscillator is it that you're trying to measure? Pendulum? Tuning 
fork? TCXO? Some SiLabs thing? That may make a huge difference in the type of 
gear you need or the measurement model.

What timing resolution do you need at 1 ms sampling rates?


> But I'd still like to know how folks are
> getting around this dead time issue with the 53131A for their measurements
> in hopes it'll shed light on how I can do the same without needing to pick
> up more gear and the inevitable shipping delay that will entail.

If zero dead time is important then make single-shot time interval measurements 
instead of using frequency or period mode. I do almost all my GPS/1PPS logging 
that way, using a 53131A like yours. But, as you surmise, you don't get 
anywhere near a 1 kHz sampling rate.


> I'm still looking for the part in the manual where
> HP/Agilent/Keysight owns up to this and describe how it changes the
> measurement.

By now there's a lot of literature, both marketing and technical, that 
describes in detail how regression-based frequency counters work. The 53131A 
was designed in the 90's before that literature was written.

There's a key footnote in the manual from which you can infer all of this. For 
a summary see this posting, and the GIF:
https://www.febo.com/pipermail/time-nuts/2013-August/079647.html

Also if you look at the specifications pages (e.g., under RMS resoluion) you'll 
see a more explicit reference to the counter making 200,000 measurements per 
second. Putting all this together it's clear this counter does precise 
single-shot time measurements (compatible with ADEV) but it does 
regression-based frequency/period measurements, which may or may not be 
perfectly compatible with ADEV.

/tvb

- Original Message - 
From: "David Burnett" 
To: 
Sent: Sunday, April 08, 2018 6:29 PM
Subject: [time-nuts] ADEV dead time w/ HP 53131A & TimeLab


> Hi time-nuts,
> 
> I'm doing oscillator-related research for my PhD and found this list
> recently. It's been a great resource in trying to refine my freq
> measurement setup and in starting to understand what's really going on
> inside my lab equipment.
> 
> I've been trawling the archives and have a question about measuring ADEV
> accurately with the Agilent 53131A frequency counter I have on hand. From
> the comments on this list and elsewhere, and the fact that TimeLab will
> talk to my 53131A directly, I have the impression one can use the 53131A
> for period measurements with which to calculate ADEV. But from GPIB command
> sniffing it looks like there's a lot of dead time between measurements:
> -- In period or freq mode* measurements take an extra ~130ms longer than
> gate time to return (but this seems to produce the correct measurements for
> TimeLab);
> -- in time interval mode they take about ~20ms;
> -- in totalize mode they take about 5ms, in keeping with "200 measurements
> per second" advertised in the brochure, but of course this is a simple
> counter and one loses the resolution of a reciprocal counter or anything
> smarter added in.
> 
> Is it just generally assumed everyone is making period measurements on time
> scales long enough that any instrument dead time is ignorable? Or is
> TimeLab and everyone else silently applying the correction factor as
> described by the Barnes & Allan NIST paper (NIST technical note 1318)? Or
> is there a configuration mode I'm missing that prints measurements with
> more regularly? TimeLab's GPIB commands seem to be limited to "get current
> measurement" so I might not have the box set up right to start with.
> 
> My research concerns oscillator drift on time scales of ~1ms to ~10s, so
> I'm guessing the 53131A with its 5-130ms of dead time isn't suitable for
> what I'm trying to measure. But I'd still like to know how folks are
> getting around this dead time issue with the 53131A for their measurements
> in hopes it'll shed light on how I can do the same without needing to pick
> up more gear and the inevitable shipping delay that will entail. I suspect
> someone will recommend that I get a time-stamping/continuous measurement
> box, which is probably the best solution. But I'm hoping there's a way
> around that 

Re: [time-nuts] Cheap jitter measurements

[Tom Van Baak]

>> Similarly, the box should be able to give me a pulse at a known time.
>
> how do you set up NTP to do that?

Don't know. That's not NTP's job. Any process that can query system time and 
get/set a GPIO bit will do. The question to be answered is how close to the 
real time (as in UTC(k), atomic clocks, GPS, etc.) is the fake time running 
inside the OS / CPU. The way you determine that is to send the fake time out, 
and/or to send real time in. A low-latency or zero-jitter GPIO pin would be 
required in either case.

> In both cases (pulse in and pulse out) the first step is to ask NTP “when was 
> that?”.
> You still have a pretty big chunk of NTP in the middle of the process …. If 
> NTP only
> “knows” what is happening (or can control what is happening)  to +/- 300 ns. 
> The guts of 
> your data will be limited to the same  300 ns. 

You don't need NTP for this experiment. That's kind of the idea. You run the PC 
/ SBC / R-Pi plain. Or you run it with NTP. Or different versions of NTP or 
different configs. Or you run it with a better xtal, or you replace the xtal 
with a GPSDO and DDS. So this isn't intended to be a hack on NTP per-se; it's 
more of a scientific testbed that you can drop NTP into. You'd get a nice set 
of phase and ADEV / TDEV / MTIE plots or something. I don't know.

I don't use NTP so take this all with a grain of salt. But from the looks of 
it, people playing (or developing) NTP fall into the same trap as some GPSDO 
developers: a focus on the performance of the PLL or other fancy internal 
colorful plots instead of real measurements of rising edges of electrons at the 
input and output.

This was easy back in the peek/poke parallel port days. Took a backseat in the 
serial and USB era. But now that many systems have GPIO ports it should be 
possible again. Anyway, Gary and Leo, et al. can report eventually what they 
find. This isn't really an NTP mailing list, but I would think some of the 
basic concepts of metrology should apply to OS timing as they do to h/w timing.

/tvb

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Re: [time-nuts] Cheap jitter measurements

[Tom Van Baak]

>>> What do you mean by "jitter" and what do you really want to do?
>> I mean jitter as NTP defines jitter.  Whatever that is.
> 
> I think you need to figure out what you want to do so you don't fool yourself.
> 
> ntpd is a PLL.  There is a low pass filter in the control loop.  It will 
> track the low frequency wander of the source.

Gary, Hal, Leo,

My mental model of a black box computer running NTP is that I should be able to 
give it a pulse (e.g., via parallel, serial, GPIO) and it tells me what time it 
was. Use a GPSDO / Rb / picDIV to generate precise pulses. Compare the known 
time of the pulse with the time the box says it was. Repeat many times, collect 
data, look at the statistics; just as we would for any clock.

Similarly, the box should be able to give me a pulse at a known time. In this 
case it records the time it thinks the pulse went out, and your GPSDO / Rb / 
TIC makes the actual measurement. Again, collect data and look at the 
statistics; just as we would for any clock.

Imagine the black box has two BNC connectors; one accepts an input pulse to be 
timed; one outputs a pulse at certain times. This allows a complete analysis of 
NTP operation. Should be true for both client or server. If you get down to 
nanosecond levels make sure to use equal length cables.

To me this better than relying on NTP to tell you how NTP is doing, which as 
far as I can tell from live plots on the web, is all that most people do. 
Instead use real, external, physical measurement. The internal NTP stats are 
fine for tracking the performance of the PLL, but don't confuse that with 
actual timing.

So this is why I'm excited to hear Gary wants a Rb timebase and a sub-ns 
counter. Someone will finally measure NTP for real, not rely on the internal 
numbers of NTP measuring itself. Or at least I hope that's what Gary is up to.

/tvb

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Re: [time-nuts] Environmental sensor recommendations

[Tom Van Baak]

> Are there any recommendations for other off-the-shelf sensors worth looking 
> at?

Mark,

Check out ADT7420:
http://www.analog.com/media/en/technical-documentation/data-sheets/ADT7420.pdf

A useful white paper, including comparison of NTC RTD and IC sensors:
http://www.analog.com/media/en/technical-documentation/frequently-asked-questions/ADT7320_ADT7420_FAQs.pdf

It's also available in a variety of small eval boards, including PMOD 
compatible PCB and flex boards:
https://store.digilentinc.com/pmod-tmp2-temperature-sensor/
http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/eval-adt7420.html

/tvb

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Re: [time-nuts] Environmental sensor recommendations

[Tom Van Baak]

Peter,

Yes, that's my current favorite turn-key environmental sensor as well. Sure, 
you can home-brew a slightly cheaper solution. And the Arduino world is full of 
random sensor examples, which you are free to deploy and debug. But the 
Sparkfun unit just works; out of the box. From the first second after power-up, 
and once every second after that, it does the one thing it is designed for: 
sense and report.

Their model is serial (USB) ascii output once a second. This works: without 
API, without command / response, without tie-in to a particular operating 
system, or driver, or downloads, or app, or API, or language du jour, or login, 
or encryption, or cloud. It's how digital sensors should be designed. KISS.

This is also why so many of us like the hp 53131A / 53132A talk-only mode. It 
just measures and reports. The picPET and TAPR TICC were designed the same way.

/tvb

- Original Message - 
From: "Peter Vince" 
To: "Discussion of precise time and frequency measurement" 
Sent: Thursday, April 05, 2018 6:24 AM
Subject: Re: [time-nuts] Environmental sensor recommendations


> Hi Mark,
> 
> SparkFun have some boards that have multiple sensors.  They *used* to
> do one with a USB connection that had temperature, pressure, humidity, and
> light!  But I see that is now "retired" (
> https://www.sparkfun.com/products/retired/8311 ) and has been replaced by
> an Arduino shield:
> 
> https://www.sparkfun.com/products/13956
> 
> The previous USB model was very easy to use, and sensitive enough for
> pressure that it easily showed when I walked up a couple of flights of
> stairs!  They have a large selection of boards, including several with I2C
> connections, so maybe one of those would be suitable?
> 
> TTFN,
> 
>  Peter

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Re: [time-nuts] Harrison's birthday

[Tom Van Baak]

Jim,

The Harrison google doodle is attached for those that missed it [1].

A couple of comments:

1) One alert reader pointed out that the clocks are stopped. Google is capable 
of clever JavaScript animations, so the least they could do is have the clocks 
in motion. It would be especially interesting to see the famous "grasshopper 
escapement" in action. Well, there's youtube for that.

2) It might even be useful if the animation showed the clocks with the correct 
time. UTC at a minimum. Or local time, since google likely has a good idea what 
timezone you are in.

3) The artist followed the clock face marketing trick of using ~10 minutes 
after 10 o'clock. That creates symmetry between the hour hand about -60 degrees 
(left of center) and the minute hand about +60 degrees (right of center).

Some of you realize that the hour hand is exactly -60 degrees only at 10:00, 
but by the time the minute hand gets to +60 degrees the time is now 10:10. And 
by then, the hour hand has moved further clockwise (yes, it's the one time when 
using that adjective is redundant) to -55 degrees so you now have overshot the 
magic moment when the two hands are truly in symmetry.

You can google the math puzzle of when exactly after 10 o'clock the hands are 
in pure symmetry [2]. The magic moment occurs at +/- 55.385 degrees which is 
10:09:14 AM/PM. If you want it to the nanosecond, then 10:09:13.846153846 is 
your answer. And this happens twice a day so even if you miss it, you get more 
chances.

4) Now that you know all of this, look again at the google cartoon. Note that 
neither the hour hand nor the minute hand is correct. The hour hand is a but 
too far ahead for 10:09, and the minute hand is a bit too far behind for 10:09. 
You just can't trust the internet anymore...

/tvb

[1] Doodles:
https://www.google.com/doodles/john-harrisons-325th-birthday
https://www.google.com/doodles?hl=en-GB
https://www.theverge.com/2018/4/3/17190940/john-harrison-google-doodle-clock-sea-watch-longitude-marine-chronometer

[2] Math clock puzzles:
https://www.fq.math.ca/Scanned/21-2/monzingo.pdf
https://www.quora.com/At-what-time-are-the-hour-and-minute-hands-at-equal-distance-from-the-6-hour
https://ldlewis.com/hospital_clock/document/Timely.encounter.abr.cmplt.pdf


- Original Message - 
From: "jimlux" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, April 02, 2018 9:19 PM
Subject: [time-nuts] Harrison's birthday


> Google reminds us that 3 April is Harrison's birthday..
> 
> https://en.wikipedia.org/wiki/John_Harrison
> 
> Interesting he (depending on your calendar) was born and died on the 
> same day.  And, interesting he died in 1776, which is of some 
> significance in the US.
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Re: [time-nuts] Cheap jitter measurements

[Tom Van Baak]

Hi Gary,

One solution is to look for used hp, Fluke, or Racal time interval counters on 
eBay. 1 or 2 ns is pretty easy to find with a $100 or $200 budget. Look for 
Racal 1992 or hp 5334B as examples. If you plan to collect lots of data, you'll 
want GPIB (or RS232 / USB) connections to a PC and that will add to your net 
cost.

Another solution is to homebrew your own 1 ns counter. The downside is you will 
spend a month working out the bugs before you trust the data. Plus if you don't 
already have another counter to compare it against it makes development even 
harder.

Third solution is the TICC from TAPR. It's new and works out of the box. Lots 
of us use them. John did a very good job with the design. Highly recommended. 
It's a dual-channel *time stamping* counter so you can collect 1PPS data on two 
separate GPS receivers at the same time if you want. In that respect it's 2x as 
useful as a commercial *time interval* counter.

You mention jitter, not ADEV. I don't think you need a fancy timebase if all 
you want to measure is jitter. You can get a good feel for the jitter of a GPS 
/ 1PPS output within a few samples. Even a minute of data is usually enough to 
establish the rms jitter value. If you want a full ADEV plot, then yes, you'd 
probably want at least an Rb for your reference.

See paragraph "Timing Stability" at http://leapsecond.com/pages/MG1613S/ for an 
example of what jitter from a GPS receiver looks like; in this case it's 
primarily sawtooth.

Right, the picPET has 400 ns resolution and so it is not the right tool for 
your nanosecond needs. I do have a 10 ns version that I use, but that's still a 
bit coarse for GPS work.

I have spare FEI Rb here; I'll send it if you want it. That way you can afford 
a TICC.

/tvb


- Original Message - 
From: "Gary E. Miller" 
To: "time-nuts" 
Sent: Tuesday, April 03, 2018 10:47 AM
Subject: [time-nuts] Cheap jitter measurements


Time-nuts!

With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution.  That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel.  That is clearly not time-nuts accuracy.

What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?  

I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR?  But that would put me out around $400.

The picPET does not look accurate enough.  Maybe a clever way to use it
for more accuracy?  Is there a picPET like thing cheaper than the
TICC-TAPR?

Ideas?

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

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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[time-nuts] quartz / liquid nitrogen

[Tom Van Baak]

Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: 
-196 C (-321F, 77K)? It's probably impractical commercially, but maybe 
something of value to a time nut. Would that dramatically lower temperature 
improve phase noise & short-term performance? Is there a crystal cut that could 
be optimized for 77 K instead of ~25 C (room) or 60 C (oven)?

If not Nitrogen, how about dry ice (-109F -78C)?

/tvb

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Re: [time-nuts] timing an ITR master clock

[Tom Van Baak]

Jerry,

Most people I know who time mechanical clocks use Bryan Mumford's Microset 
timer:

  https://www.bmumford.com/microset.html

  https://www.bmumford.com/mset/model3.html

Bryan has a wide variety of sensors: optical, acoustic, magnetic, laser, etc.

Of course it is possible to home-brew a solution. Many of us have done that. 
But it's not quite as easy as it sounds to get a system that gives you reliable 
data.

Several people use PC's as the timer, but be aware that pendulum clocks can 
easily achieve ppm levels of stability in which case the data you get might 
actually be your PC being timed by a pendulum, not a pendulum being timed by a 
PC.

You might also get good advice from one of the watch & clock forums on the 
'net. We tend to stay away from generic mechanical clock topics here on 
time-nuts.

/tvb

- Original Message - 
From: "Jerry Hancock" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, April 02, 2018 8:42 AM
Subject: [time-nuts] timing an ITR master clock


>I have a new to me International Time Recorder (pre-IBM) master clock.  I has 
>second, minute and hour closures and was thinking of using the second closure 
>to check the beat and time.  If others have done this kind of thing, let me 
>know.  I have a mix of timing equipment, of course, and have to be careful 
>with DC always, so I was thinking of just using an oscillator looped through 
>the second switch to get a rough idea of the timing.
> 
> Thoughts?  Beautiful clock, a friend of mine is the current expert having 
> over 300 such clocks and affiliated secondary clocks, etc.
> 
> Regards,
> 
> Jerry
> 
> 
> Jerry Hancock
> je...@hanler.com
> (415) 215-3779
> 
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Re: [time-nuts] Ultralink

[Tom Van Baak]

> I have a 333 box with 301 antenna.  It was a gift several years ago.  The 
> display updates, but the meter never gets off 0.  At the time, I thought the 
> new modulation scheme had killed it and didn't investigate.  But tvb 
> suggested it should still work, so I took the cover off.

Hal,

I tested several old Ultralink WWVB receivers this evening and, yes, they work 
fine. The products were designed for precise timing rather than stabilized 
frequency. Thus they don't rely on the carrier and are not caught by the 
"enhanced" WWVB format that killed all the Spectracom WWVB receivers.

Model 332 has small LCD with date, time, status display.
Model 333 has larger LCD and calibrated analog signal level meter.
Both connect to a remote model 301 antenna module.
Yes, the antenna module contains a Temic U4226B.

My 333/301 signal levels idle at around +9 or +10, and bounce down each second 
as expected.

I updated http://leapsecond.com/museum/ulio/ with more manuals, and many 
exterior / interior photos of the 301 module.

Hopefully you and John can get yours working. Let me know on- or off-list if 
there's anything I can do to help.

/tvb

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Re: [time-nuts] WWV/CHU

[Tom Van Baak]

> This is an IEEE article from 1972 that looks like a good fit:
>  Nationwide Precise Time and Frequency
>  Distribution Utilizing an Active Code Within
>   Network Television Broadcasts
>DAVID A. HOWE
> https://www.researchgate.net/publication/3092613

FYI: for the original spam-free version, please use:

https://tf.nist.gov/general/pdf/469.pdf

In general, if the author or paper is related to NIST, the original 
copyright-free PDF will be available in the NIST Time and Frequency Publication 
Database. That easily searchable database, and the thousands of papers it 
contains, is probably the greatest asset we time nuts have. For those of you 
that don't know it yet, check it out:

https://tf.nist.gov/general/publications.htm

As a non-academic working from home one of the greatest frustrations is getting 
copies of old and new scientific articles. NIST seems to be the rare exception. 
Decade after decade, administration after administration, that database keeps 
working.

> These are my opinions.  I hate spam.

Me too, which is why it's so frustrating to deal with web sites that scrap free 
PDF's and then serve them to you for a price or with a side of spam. There are 
even web sites that serve all our time-nuts postings along with injected 
targeted ads.

/tvb

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Re: [time-nuts] Ultralink WWVB receiver manuals?

[Tom Van Baak]

> It would be very nice to have a direct NIST time source in the lab 
> again, complete with PPS output.

If you have a 1200/9600 baud modem and a land line, 303.494.4774 is also a 
reliable backup source of NIST time.

https://www.nist.gov/pml/time-and-frequency-division/services/automated-computer-time-service-acts

/tvb

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Re: [time-nuts] Ultralink WWVB receiver manuals?

[Tom Van Baak]

Congrats on your acquisition. The Ultralink WWVB receivers are very nice. It 
should still work -- it's an AM subcode (not carrier phase) receiver. If you 
have more questions let me know. These modules were the darling of precise time 
at the turn of the century; before mobile phones, before GPS was affordable. 
Ultralink discontinued the product line within a few years when the market for 
WWVB-based timing dried up.

Manuals here: http://leapsecond.com/museum/ulio/

Good question on the cable. If you don't see it in the manual let me know; I'll 
dig out my cable and have a look. Note the inner 4 of 6 pins are Vcc, TCO, AGC, 
gnd.

/tvb

- Original Message - 
From: "John Ackermann N8UR" 
To: "Discussion of precise time and frequency measurement" 
Sent: Thursday, March 29, 2018 8:57 AM
Subject: [time-nuts] Ultralink WWVB receiver manuals?


> I just acquired an Ultralink WWVB timecode receiver -- more 
> specifically, model 301 receiver and model 333 decoder.
> 
> I'm looking for documentation on these guys.  Anyone have a manual 
> they'd be willing to share?
> 
> The key questions are really just two:  (a) is the 6P6C modular cable 
> connecting the receiver and decoder straight, or reversed, and (b) what 
> are the four DIP switches on the back of the 333 used for?
> 
> Thanks for any info.
> 
> John
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Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver

[Tom Van Baak]

> Tom,
>
> In my TB monitor kit, I used your Julian date routines, adapted to the 8051
> (no variable greater than 32 bits since my compiler does not support them
> either) to apply the GPS offset correction. It was very helpful.
>
> Didier KO4BB

Right. There are many ways to address the 1024 week rollover. Mark uses JD and 
floating point because his program contains lots of astronomical features and 
JD is useful and popular in that context. I suspect the code you're using is 
from this demo -- http://leapsecond.com/tools/tbolt1.c -- which is based on MJD 
and integer only.

The code I mentioned today -- http://leapsecond.com/tools/gpsdn.c -- is similar 
except its based on GPSDN instead of MJD. I came up with GPSDN because it's 
easier to work with GPS cycles when the origin of GPS time is GPSDN = 0 instead 
of something like MJD = 44244, or JD = 2444244.5, or unix_time_t = 315964800, 
or Excel date 29226.

If you display GPSDN as hex or binary, GPS rollovers are a picture-worthy 
ripple-carry binary odometers:

1999-08-21 = GPSDN 7167 = 0x1BFF = 0b11011
1999-08-22 = GPSDN 7168 = 0x1C00 = 0b11100

2019-04-06 = GPSDN 14335 = 0x37FF = 0b110111
2019-04-07 = GPSDN 14336 = 0x3800 = 0b111000

2038-11-20 = GPSDN 21503 = 0x53FF = 0b1010011
2038-11-21 = GPSDN 21504 = 0x5400 = 0b1010100

2058-07-06 = GPSDN 28671 = 0x6FFF = 0b110
2058-07-07 = GPSDN 28672 = 0x7000 = 0b111

While I'm at it, and for newcomers to the group, note that GPS rollovers occur 
about every 19.6 years (1024 weeks) and occur in "GPS time", which is offset 
from "UTC time" by a particular number of leap seconds. That's why GPS 
rollovers do not occur at precisely midnight on the dates listed above. Also 
why it's not possible to list the exact time of future GPS rollovers as UTC 
date & time. Hint: stay well away from self-driving vehicles during leap 
seconds and GPS rollovers.

/tvb

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Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver

[Tom Van Baak]

Hi Mark,

> Heather keeps all times as a double precision Julian date.  Using Heather's 
> code can
> be a problem on Arduinos since their "double" precision numbers are actually 
> 32 bit
> single precision,  so you would need to do some more complicated math.

Ah, more complicated math to solve a problem vs. simpler math to avoid a 
problem in the first place.

Here's a simple "GPS Day Number" example: www.leapsecond.com/tools/gpsdn.c

To add 1024 weeks to a given date use:

gpsdn = date_to_gpsdn(year, month, day);
gpsdn += 1024 * 7;
gpsdn_to_ymd(gpsdn, , , );

That's it. It uses 32 bit integers; no floating point required; works on any 
OS, or Arduino.

/tvb

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Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver

[Tom Van Baak]

Don,

The primary purpose of a Thunderbolt GPSDO is ultra-precise time (1PPS) and 
frequency (10 MHz), locked to each other, and to UTC. The good news is these 
two BNC outputs are unaffected by the date issue that you describe. The TBolt 
is designed to run fine on its own; you typically don't need a PC or control 
program to operate it.

The bad news is that if you use the Trimble TSIP RS232 interface and if you 
want the correct date & time then the software needs to be aware of the 1024 
week (19.6 year) epoch. This "GPS 1024 week rollover" issue eventually affects 
many receivers, including the TBolt, but the good news is that simple 
work-arounds are often available to address the problem.

AFAIK, the Tboltmon.exe program has *not* been updated. I still use it (when 
you're dealing with nanoseconds, calendar dates are less important).

Mark's LH program *has* been updated. See: 
http://www.ke5fx.com/heather/readme.htm

Didier's LCD date/time display *has* been updated: 
http://www.ko4bb.com/Timing/GPSMonitor/kit.php

/tvb

- Original Message - 
From: 
To: 
Sent: Monday, March 26, 2018 2:17 PM
Subject: [time-nuts] Setting correct date on Trimble Thunderbolt receiver


> Hello all,
> I am new to the board and have just received a Trimble Thunderbolt GPS 
> receiver today.
> All is working correctly except the date shows Aug 10 1998.
> How do set the proper date on this?
> I am running TBoltMon to access the unit.
> Any help would be appreciated.
> Thanks,
> Don W9BHI
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Re: [time-nuts] Odetics Telecom CommSync - GPS Rollover Problem.

[Tom Van Baak]

Hi Rob,

I don't know if there's new firmware. For most of my GPSDO I don't actually 
need date & time so it's been less of a priority for me to deal with gps 
rollover events.

Anyone else on the list have Odetics CommSync's and can report on their status?

/tvb

- Original Message - 
From: "Rob Kimberley via time-nuts" <time-nuts@febo.com>
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts@febo.com>
Sent: Friday, March 23, 2018 1:50 PM
Subject: [time-nuts] Odetics Telecom CommSync - GPS Rollover Problem.


> I wonder if Tom Van Baak can help me on this one. 
> 
> 
> 
> Recently powered mine up for the first time in a few years. Although the
> unit survived the original GPS Rollover, it obviously can't cope with the
> subsequent one, and is currently showing June 01, 1998 as I type this..
> 
> 
> 
> Tom, as you bought one of these off me, do you know of any updated firmware?
> 
> 
> 
> Thanks and kind regards
> 
> Rob K
> 
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Re: [time-nuts] WWVB Antenna revisited/Spectracom 8182

[Tom Van Baak]

Donald,

Your Skyscan radio clock, as well as all other consumer-grade WWVB clocks & 
watches, will continue to work. The new format was designed to be compatible 
with the old format so any receiver that gets time only from the AM subcode 
will continue to work.

It's the commercial time & *frequency* receivers that don't work anymore. This 
is because the new format creates rapid phase shifts in the 60 kHz carrier 
which break the PLL design used in legacy receivers.

There's tons of time-nuts postings over the years on the subject. If you want a 
fun h/w and s/w project you can solve the problem for your receiver. Or google 
a bit and find some WWVB emulator projects which mimic the old signal well 
enough to keep receivers like Spectracom happy. Plus you won't need to hunt for 
a loop antenna for your 8182.

If you just want a home clock that's accurate at the sub-second level, consider 
a computer (NTP) or time.gov or GPS or GPSDO or smart phone or even NIST 
dial-up. Over the decades we've lost Omega, GOES, Loran-C and the carrier part 
of WWVB. But when you think of it, cell phones, the internet, and GPS (and 
GLONASS, Galileo, Beidou) are a pretty good replacement for those vintage time 
services.

/tvb

- Original Message - 
From: "D. Resor" 
To: "'Discussion of precise time and frequency measurement'" 

Sent: Thursday, March 22, 2018 12:13 PM
Subject: Re: [time-nuts] WWVB Antenna revisited/Spectracom 8182


I remember being told about this years ago, but it had not registered in my 
mind recently that it was the format which had changed.  For some reason I 
thought it was the transmission frequency.

I'm a little baffled though, I purchased both of my SkyScan clocks, prior to 
these changes.  Yet they both still set themselves (when propagation allows) 
correctly.   One would think inexpensive products would be sacrificed verses 
the more expensive equipment.

What are example(s) of the "gizmo" which will convert the new format to the old 
one?

I realized later after reading more about the antenna I am looking at that it 
has a DC blocking capacitor built in, therefore it should be fine.  This is 
what happens when I spend too much time during the wee hours of the 
night/morning with a mind which becomes even more cloudy.

Thanks

Donald Resor
N6KAW



-Original Message-
From: time-nuts  On Behalf Of Bob kb8tq
Sent: Thursday, March 22, 2018 8:13 AM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] WWVB Antenna revisited/Spectracom 8182

Hi

You should DC block the output of the 8182 if you are going to run it straight 
to an antenna. 

The bigger issue is that WWVB changed their transmit format a couple years ago. 
The signal they now send is not compatible with a lot of gear out there. 
It turns out that the 8182 is included on that list:

https://spectracom.com/support/retired-products/netclock?field_product_availability_ref_tid=94
 


There are gizmos you can build to convert the new transmit format to the old 
one, I’m not sure if you are interested in going to that extreme. 

Bob



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[time-nuts] Stephen Hawking, an honorary time-nut

[Tom Van Baak]

"Stephen Hawking dies aged 76"
http://www.bbc.com/news/uk-43396008

"Obituary: Stephen Hawking"
http://www.bbc.com/news/science-environment-1565

"Stephen Hawking, modern cosmology's brightest star, dies aged 76"
https://www.theguardian.com/science/2018/mar/14/stephen-hawking-professor-dies-aged-76

"Stephen Hawking obituary"
https://www.theguardian.com/science/2018/mar/14/stephen-hawking-obituary

/tvb
http://www.leapsecond.com/great2016a/
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Tom Van Baak]

> In short, the GPS to UTC time correction polynomial got screwed up.

Yes, that was an exciting time!



For newcomers to the list, the bizarre GPS 13 microsecond jump was a hot topic 
on time-nuts back in 26-Jan-2016. The thread starts with an observation by Paul 
Boven:

https://www.febo.com/pipermail/time-nuts/2016-January/095667.html

And includes detailed follow-up by Martin Burnicki:

https://www.febo.com/pipermail/time-nuts/2016-January/095692.html
https://www.febo.com/pipermail/time-nuts/2016-January/095756.html
https://www.febo.com/pipermail/time-nuts/2016-January/095714.html
https://www.febo.com/pipermail/time-nuts/2016-January/095753.html

If you have time, read the full "GPS jumps of -13.7 us?" thread from the 
archives:

https://www.febo.com/pipermail/time-nuts/2016-January/subject.html#95667

And also the "GPS PRN 32" thread:

https://www.febo.com/pipermail/time-nuts/2016-January/subject.html#95682



As far as monitoring mains phase -- a 13 microsecond step would be lost in the 
normal jitter and drift of power line timing. My 60 Hz logging was unaffected 
by the event because I use a cesium reference (not GPS or GPSDO).

/tvb

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Tom Van Baak]

> “Back in the day” we used WWV and the kitchen clock for that sort of thing……

Bob,

Yes, not much has changed. I use multiple methods to measure 60 Hz in order to 
gain confidence in the results. Besides the picPET, I've used a commercial 
TrueTime TFDM (Time/Frequency Deviation Meter) and also a plain old kitchen 
clock (synchronous motor, wall clock).

Example: I took photos of the kitchen clock precisely 30 seconds after each 
quarter hour. Here's the short animated GIF of that run; you can see how the 
wall clock wanders from 0 to 5 seconds ahead of the UTC reference clock (seen 
in the background):

http://leapsecond.com/pages/tec/mains-clock-ani.gif

For alert readers: the +/- 1 second jitter in the reference clock is due to 
drift and latency in the PC scripts used to trigger the photo capture. Also 
sunrise (Pacific time) can be seen in the background starting about 1300 UTC.

/tvb

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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Tom Van Baak]

> I've done some Googling and have found any number of designs.

Pat,

1) Safety. I usually use a low voltage step-down transformer. This gives 
isolation and safety. Anything from 3 VAC to 24 VAC is fine.

2) Trigger. There are dozens of schematics on the web for capturing the 
zero-crossing of a low-voltage sine wave. You can easily go overboard on this. 
Or just keep it simple and feed the signal through a resistor directly into a 
microprocessor input. The internal clamping diodes do their thing. A Schmitt 
trigger input is helpful but not necessary depending on how your software makes 
the measurement.

3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
year) you don't need an atomic timebase. If you collect data for a couple of 
days any old XO will be fine. If you plan to collect data for months you may 
want a OCXO. Most of us just use cheap GPS receivers.

4) Measurement. There are many ways to measure the signal. You can measure 
frequency directly, as with a frequency counter. You get nice data but it may 
not be perfect long-term due to dead time or gating effects in the counter.

So what most of us do is measure phase (time error) instead. One way is to make 
time interval measurements from a given mains cycle to a GPS 1PPS tick or vice 
versa, from each GPS/1PPS tick to the very next mains cycle. Either way you get 
about sample per second. If you're in search of perfection it gets a bit tricky 
when the two signals are in a coincidence zone.

The other approach is not to use a frequency or time interval counter at all. 
Instead you timestamp each cycle, or every 60th cycle. Unix-like systems have 
this capability. See Hal's posting. I use a picPET, a PIC microcontroller that 
takes snapshots of a free-running decimal counter driven by a 10 MHz timebase 
(OCXO or GPSDO).

The advantage of the timestamp method is that you don't ever miss samples, you 
can time every cycle (if you want), or throw away all but one sample per second 
or per 10 seconds or per minute, etc. And best of all, timestamping avoids the 
hassles of the coincidence zone.

5) CPU. A plain microcontroller, or Arduino, or R-Pi can be used. Or if you're 
on Windows and have a native or USB serial port try this simple tool as a demo:

http://leapsecond.com/tools/pctsc.exe
http://leapsecond.com/tools/pctsc.c

6) An assortment of mains links:

http://leapsecond.com/pages/mains/
http://leapsecond.com/pages/mains-cv/
http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html
http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png
http://leapsecond.com/pages/tec/mains-clock-ani.gif
http://leapsecond.com/pages/ac-detect/
http://leapsecond.com/pic/picpet.htm
http://leapsecond.com/pic/pp06.htm

7) Final comments.

It is tempting to worry about the design, as they are so many out there on the 
web. Which is best? What are the pitfalls? What about noise immunity? What 
about precision and accuracy? My recommendation is not to over-think this. Just 
throw something together and see what you've got. Most of the work is with 
handling the data you get, doing the math, making plots, etc. If after the 
first day you see odd-looking 16 ms jumps in your data then you know you need 
to pay more attention to trigger level or noise issues.

8) A sound idea.

We need someone to try out the sound card method. Send the isolated low voltage 
AC into the L channel and a GPS 1PPS into the R channel. "The rest is just 
software." Note that because you have access to the entire sine wave there's a 
lot you can do with this method besides making charts of time drift or 
frequency deviation from the zero-crossings.

For an even cheaper solution, forget the GPS receiver and the R channel -- 
since the PC (if running NTP) already knows the correct time. And skip the AC 
transformer too -- instead just hang a foot of wire off the L channel input. 
There's mains hum everywhere. It would be the one time in your life where the 
ever-present audio hum actually has a good use.

/tvb

- Original Message - 
From: "Patrick Murphy" 
To: 
Sent: Saturday, March 10, 2018 2:53 PM
Subject: [time-nuts] Recommendations for Mains Power Monitor / Logger


All this talk of varying mains power frequency aberrations has me
curious what is happening in my own back yard here in Tulsa in the
USA. Can some recommend a reasonable "introductory level" solution for
this? (As a fledgling Time-Nut, those two words were hard to say.)
At the least I would like to watch voltage and frequency, with a
configurable monitoring and logging interval. I can provide precise
timing as needed for synchronization and time-stamping. Expanded
ability to also monitor amperage, various power factors, etc is a plus
but not required at this point.

I've done some Googling and have found any number of designs. What I
can't tell is how well they work. I am pretty handy with my hands and
do not at all mind a DIY 

Re: [time-nuts] Ultra low power RTC

[Tom Van Baak]

> Since we don’t often *need* the smallest cell made *and* we’re probably 
> talking lifetime of the cell….. does 22 na vs 33 na matter?

It gets even more amazing ...

"A 1.5 nW, 32.768 kHz XTAL Oscillator Operational From a 0.3 V Supply"
https://web.northeastern.edu/ecl/wp-content/uploads/2016/12/xtal.pdf

/tvb
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Re: [time-nuts] ADEV data for mechanical clocks

[Tom Van Baak]

> Does anybody have any ADEV data for mechanical clocks?  (I didn't find any by 
> google, but there was a lot of noise so maybe I missed something.)

Hal,

It's often buried in out-of-print horological books or magazines / journals / 
articles that google may or may not index.

I have some ADEV examples here:

http://www.leapsecond.com/pages/m21/ -- the classic Navy chronometer
http://www.leapsecond.com/pend/shortt/  -- see Stable32 / Timelab plots
http://www.leapsecond.com/pend/clockb/  -- go to technical links
http://www.leapsecond.com/hsn2006/  -- see dream pendulum paper

> I'd expect a watch to slow down slightly as the spring unwinds.  That 
> probably doesn't apply to clocks driven by weights.

Clockmakers are clever and implement methods to keep constant power:

https://en.wikipedia.org/wiki/Fusee_(horology)
https://en.wikipedia.org/wiki/Maintaining_power

Photo:
https://www.wired.com/wp-content/uploads/archive/images/slideshow/2007/12/gallery_time_hackers/disk.jpg
via https://www.wired.com/2008/01/gallery-time-hackers/

Diagrams:
http://www.hamiltonparts.com/m21-6.jpg
http://www.hamiltonparts.com/m21-8.jpg
via  http://www.hamiltonparts.com/hamilton.htm

Additional photos:
https://chronometerbookdotcom.files.wordpress.com/2017/11/broken-chain-labelled1.jpg
via https://chronometerbook.com/2017/11/

https://chronometerbookdotcom.files.wordpress.com/2017/02/attach-to-fusee-1.jpg
via https://chronometerbook.com/2017/02/13/27-fusee-chain-substitute/

/tvb

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Re: [time-nuts] Mechanical Precision Clocks

[Tom Van Baak]

Hi Adrian,

FYI -- Bill's also a long-time member of time-nuts. And he's also one of the 
reasons there is a time-nuts group. In the mid 90's I met Bill (and also Corby) 
through classified ads in Nuts & Volts magazine. Long story, but it was then 
that I learned it was "ok" to be interested in both vintage mechanical / 
pendulum clocks and also modern quartz / atomic clocks. His pendulum clocks are 
world-class masterpieces and his home atomic time lab was the inspiration for 
mine.

>From my perspective most historical, horological, mechanical watch & clock 
>people are shy (or even dismissive) of anything electronic. Similarly, most 
>electronic timekeeping people are ignorant (or even dismissive) of the 
>wonderful world of precision mechanical timekeeping. So there's only a small 
>subset of people who bridge that gap. Bill is one of them. If you're 
>interested in modern mechanical timekeeping, please subscribe to HSN 
>(Horological Science Newsletter) via http://www.hsn161.com

If you have any questions for Bill, I'm sure he'd be happy to answer them.

/tvb


- Original Message - 
From: "rfnuts" 
To: 
Sent: Tuesday, March 06, 2018 4:23 PM
Subject: [time-nuts] Mechanical Precision Clocks


> Bill Scolnik's Clocks:
> http://www.precisionclocks.com/index.html
> 
> The (non mechanical) standards lab:
> http://www.precisionclocks.com/wpimages/wpe1967732_06.png
> 
> Adrian

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Re: [time-nuts] WWV or Net Clock controlled oscillator

[Tom Van Baak]

Adrian, et al.

An updated list of PIC dividers:
http://leapsecond.com/pic/picdiv-list.htm

Source code and hex files:
http://leapsecond.com/pic/src/

And, you guessed it, PD60 is the one that divides 10 MHz into 60 Hz (exactly). 
Documentation and source code:
http://leapsecond.com/pic/src/pd60.asm

/tvb

- Original Message - 
From: "Adrian Godwin" <artgod...@gmail.com>
To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
Sent: Sunday, March 04, 2018 2:57 PM
Subject: Re: [time-nuts] WWV or Net Clock controlled oscillator


> There is indeed a 60Hz out picdiv from Tom Van Baak -
> http://www.leapsecond.com/pic/picdiv.htm. It's not in that list but ask Tom.
> 
> I've just used one (modified for 50Hz out) to drive a 1A H-bridge circuit
> that supplies a 12V peak-peak square wave to an old LED clock, replacing
> the original wall-wart.
> It works very nicely, and is driven by the 10MHz output of a cheap surplus
> GPSDO.

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Re: [time-nuts] WWV or Net Clock controlled oscillator

[Tom Van Baak]

Donald,

Possible solutions to your 60 Hz mains problem:

1) If you don't want to open or hack the clock controller in any way consider 
using a "online" UPS. Typically the synthesized 60 Hz AC output is quartz 
controlled.

2) Make your own low-power 60 Hz AC/DC/AC power supply -- using a quartz, or 
ovenized quartz, or GPSDO or NTP-based timebase. How many watts do you need? 
How many seconds per week is your limit?

3) Open the clock controller and locate the wire that gets the 60 Hz timing; 
probably from a low voltage winding of the transformer. Then cut the wire and 
feed your own precise digital 60 Hz instead.

4) You mentioned "the 60Hz reference can be switched out". In that case what is 
the time source? What frequency? Based on a cheap quartz xtal? If so, perhaps 
it's easier to replace that instead of messing with 60 Hz.

> I was trying to locate a cost effective clock reference which can be
> synchronized from either WWV, request the correct time from a net server or
> possibly GPS.  It then needs a clock referenced output of 60Hz.

Can you be more specific about this requirement? Generating a precise 60 Hz is 
a different problem from knowing what the current local date / time is.

/tvb

- Original Message - 
From: "D. Resor" 
To: "Time Nuts List" 
Sent: Sunday, March 04, 2018 2:30 AM
Subject: [time-nuts] WWV or Net Clock controlled oscillator


> Hello,
> 
> 
> 
> My first post here. I found this group's user group page while researching a
> source for either a WWV, GPS or Network referenced oscillator.
> 
> 
> 
> The devices/equipment which I was able to find didn't  seem to fit the
> requirements.
> 
> 
> 
> What I have is a Maas-Rowe DCB1 (Digital Chronobell Series 1) clock
> controller.  
> 
> Seen here:
> http://hammondorganservice.com/downloads/images/carillon/TempleCitySDADCB1a.
> jpg
> 
> 
> 
> The system can be heard playing the Westminster Chimes and striking 12 noon
> here:
> 
> 
> 
> https://www.youtube.com/watch?v=Ij5c6RqGhn0
> 
> 
> 
> 
> 
> It can be programmed to play Westminster sequences and/or music selections
> using Maas-Rowe real struck chromatically tuned bell rods.
> 
> 
> 
> This unit is installed in Southern California Edison area.  The problem is,
> this unit receives its clock reference from the 60Hz AC line to keep it in
> sync.  Up until a few years ago this worked very well.  Now, Edison's 60Hz
> line frequency is all over the place and this clock unit now gains 30
> seconds and/or more a week which makes it difficult to keep it synchronized.
> 
> 
> 
> The 60Hz reference can be switched out by the use of dip switches, however
> that setting isn't much better.
> 
> 
> 
> I was trying to locate a cost effective clock reference which can be
> synchronized from either WWV, request the correct time from a net server or
> possibly GPS.  It then needs a clock referenced output of 60Hz.
> 
> 
> 
> Does such a thing exist?
> 
> 
> 
> Thank You
> 
> 
> 
> 
> 
> Donald R. Resor Jr. T. W. & T. C. Svc. Co.
> 
> http://hammondorganservice.com
> Hammond USA warranty service
> "Most people don't have a sense of humor. They think they do, but they
> don't." --Jonathan Winters
> 
> 
> 
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Re: [time-nuts] Z3801A OCXO manual trimming

[Tom Van Baak]

> Interesting point about the heater not working vs. the XTAL having drifted 
> too far.

Any logs you made of EFC percent over the past few months or years will help 
verify the off-the-rail theory.

Another thing to try -- turn-off the Z3801A for a couple of hours to let it 
cool. Disconnect the GPS antenna. Then power it up and monitor the frequency, 
say every 10 s or a minute, until it stabilizes. The shape of this warm-up 
curve will give you a hint if the oven(s) are working. Repeat the test with the 
outer oven disconnected to test the inner oven by itself.

/tvb

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Re: [time-nuts] FRK

[Tom Van Baak]

Bert's M100 Rb teardown photos are now here:

http://leapsecond.com/bert/m100.htm

/tvb

- Original Message - 
From: "ewkehren via time-nuts" 
To: "Discussion of precise time and frequency measurement" 
Sent: Sunday, February 25, 2018 6:05 AM
Subject: [time-nuts] FRK


We have pictures of the guts of a M100 the file is 1.8 M off list or permission 
to post

Bert Kehren 

Sent from my Galaxy Tab® A
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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

> Yet another reason to nuke the battery and the A2 board. 

Yes. Then again, the effect is very minor when you look at the PN and ADEV 
plots. It falls into the category of "look how sensitive a TimePod is" more 
than "look how bad a 5065A is". And remember it's just a warning lamp, with a 
toggle switch to reset the blink.

> a PIC-DIV pull compared to the 1 pps section of one of these old beasts (Cs 
> or Rb)? 

Right, a PIC divider is much lower power, but if you're driving a 50R load 
that's still a lot of current. I suspect this is one reason why high-end 
standards use 10 or 20 us wide pulses and not 50% duty cycle square waves for 
their 1PPS outputs. Same power but 10 us is 50,000x less energy than 0.5 s. 
I've stopped using squares waves for 1PPS around here.

BTW, a trick for blinking LED's -- use two of them out of phase: one that the 
user sees on the front panel and one that is blacked out or hidden inside. A 
flip-flop (Q and /Q) or even a set of inverters is all you need. The current 
draw thus remains constant in spite of the blinking.

/tvb

- Original Message - 
From: "Bob kb8tq" <kb...@n1k.org>
To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
Sent: Monday, February 26, 2018 11:51 AM
Subject: Re: [time-nuts] Allan variance by sine-wave fitting


Hi

Yet another reason to nuke the battery and the A2 board. 

It is amazing just how small a signal can mess things up at the levels involved 
in
a good frequency standard. The old “when in doubt, throw it out” mantra may be
a good one to keep in mind relative to a lot of add on features…. how much does
a PIC-DIV pull compared to the 1 pps section of one of these old beasts (Cs or 
Rb)? 

Lots to think about. 

Bob

> On Feb 26, 2018, at 2:20 PM, Tom Van Baak <t...@leapsecond.com> wrote:
> 
>> at telling you it was sitting on top of a power transformer. It didn’t 
>> matter a lot
> 
> I did ten runs of various standards that were within a couple of meters of 
> the bench; the TimePod did not move the entire time. Each standard had a 
> different looking PN plot, so I'm pretty sure the 120 Hz spur we see is the 
> 5065A itself, not something in the lab.
> 
> File http://leapsecond.com/tmp/2018b-Ralph-2-pn.png is attached.
> 
> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What 
> do you think that is? On a hunch I opened the front panel and reset the 
> blinking amber battery alarm lamp, and voila, that noise went away. Makes 
> sense when you think of the power variations associated with a blinking 
> incandescent lamp.
> 
> /tvb
> 
> - Original Message - 
> From: "Bob kb8tq" <kb...@n1k.org>
> To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time and 
> frequency measurement" <time-nuts@febo.com>
> Sent: Monday, February 26, 2018 7:00 AM
> Subject: Re: [time-nuts] Allan variance by sine-wave fitting
> 
> 
> Hi
> 
> One of the TimePods that I had access to in the past was particularly good
> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a lot
> which instrument the power transformer was in. For some weird reason it
> was a good magnetometer at line frequencies. I never bothered to send it
> back for analysis. Simply moving it onto the bench top (rather than stacked 
> on top of this or that) would take care of the issue.
> 
> As far as I could tell, it was just the one unit that had the issue. None of 
> the
> others in the fleet of TimePods seemed to behave this way. Given that they
> normally are very good at rejecting all sorts of crud and ground loops, it 
> was 
> somewhat odd to see. 
> 
> Bob
> 
>> On Feb 26, 2018, at 7:13 AM, Tom Van Baak <t...@leapsecond.com> wrote:
>> 
>>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
>> 
>> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
>> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
>> to run at that resolution so effects like this show up. Once that's done, 1 
>> ms resolution is overkill.
>> 
>> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
>> and TDEV plots.
>> 
>> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
>> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
>> It's best seen as a bump at ~4 ms in the TDEV plot.
>> 
>> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 
>> Hz.
>> 
>> /tvb
>> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>
> 
> <2018b-Ra

Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a lot

I did ten runs of various standards that were within a couple of meters of the 
bench; the TimePod did not move the entire time. Each standard had a different 
looking PN plot, so I'm pretty sure the 120 Hz spur we see is the 5065A itself, 
not something in the lab.

File http://leapsecond.com/tmp/2018b-Ralph-2-pn.png is attached.

Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What do 
you think that is? On a hunch I opened the front panel and reset the blinking 
amber battery alarm lamp, and voila, that noise went away. Makes sense when you 
think of the power variations associated with a blinking incandescent lamp.

/tvb

- Original Message - 
From: "Bob kb8tq" <kb...@n1k.org>
To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time and 
frequency measurement" <time-nuts@febo.com>
Sent: Monday, February 26, 2018 7:00 AM
Subject: Re: [time-nuts] Allan variance by sine-wave fitting


Hi

One of the TimePods that I had access to in the past was particularly good
at telling you it was sitting on top of a power transformer. It didn’t matter a 
lot
which instrument the power transformer was in. For some weird reason it
was a good magnetometer at line frequencies. I never bothered to send it
back for analysis. Simply moving it onto the bench top (rather than stacked 
on top of this or that) would take care of the issue.

As far as I could tell, it was just the one unit that had the issue. None of the
others in the fleet of TimePods seemed to behave this way. Given that they
normally are very good at rejecting all sorts of crud and ground loops, it was 
somewhat odd to see. 

Bob

> On Feb 26, 2018, at 7:13 AM, Tom Van Baak <t...@leapsecond.com> wrote:
> 
>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
> 
> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
> to run at that resolution so effects like this show up. Once that's done, 1 
> ms resolution is overkill.
> 
> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
> and TDEV plots.
> 
> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
> It's best seen as a bump at ~4 ms in the TDEV plot.
> 
> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 Hz.
> 
> /tvb
> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>

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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?

The ADEV wiggles aren't visible with normal tau 1 s measurements. But since the 
TimePod can go down to tau 1 ms, when I first measure a standard I like to run 
at that resolution so effects like this show up. Once that's done, 1 ms 
resolution is overkill.

In this case it appears to be power supply noise. Attached are the ADEV, PN, 
and TDEV plots.

The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing at 
60 Hz. When integrated these cause the bumps you see in the ADEV plot. It's 
best seen as a bump at ~4 ms in the TDEV plot.

Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 Hz.

/tvb
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Re: [time-nuts] Selling Time and Frequency Equipment Or "just saying"

[Tom Van Baak]

Corby,

Thanks for your informative posting. I concur. Let me add a visual that echoes 
your comments. It's the same plot that I attached in the note about Ralph's 
lab. For those of you who can't view email attachments see [1].

The plot is ADEV of 4 typical lab frequency sources:

- A 5071A in Ralph's lab, on loan from NIST.
- A 5065A Ralph owns, which has some 120 Hz noise, but excellent stability 
beyond tau 1 s.
- The 10 MHz ref out of a Agilent/Keysight 53230A counter (XO or TCXO, not 
sure).
- The 10 MHz ref out of a SRS SG348 signal generator (OCXO option).

Note the difference between the 5065A and the 5071A in the plot. You can see 
why for many experiments a 5065A is preferred. I mean, over a wide range of tau 
it's 4x better. OTOH, if you want to make short-term measurements against a 
cesium standard, by all means turn off the Cs beam and let it free-run. Both 
the 5061A and 5071A make this easy.

/tvb

[1] http://leapsecond.com/tmp/2018b-Ralph-4-adev.png


- Original Message - 
From: 
To: 
Sent: Saturday, February 24, 2018 2:14 PM
Subject: [time-nuts] Selling Time and Frequency Equipment Or "just saying"


> First, full disclosure, I have no vested or financial interest in the
> 5065A he is selling.
> 
> Now the 2816A prefix is the last series built so the most modern.
> The last one I remember on eBay went for OVER $4000.00
> 
> Comparing a 5065A to a Cesium (except maybe a working 5071A for the same
> price)\is worse than Apples and Oranges.
> 
> Ask Bert who got rid of his 5065A years ago because he had a Cesium, he
> regrets that now and just got a new one!
> 
> A 5065A buyer is looking for the best short term stability he can find
> (nominal 1.5X10-13th at 100 Sec)
> Keeping on frequency is easy via GPS comparisons.
> 
> A Cesium buyer want NIST traceable accuracy "out of the box" and never
> (practically) having to adjust the frequency. The Cesium will be worse
> when  compared to the 5065A at shorter Tau even if it has a high
> performance tube.
> 
> Another thing to consider when buying a Cesium is what is the condition
> of the tube. The tube will die, just don't know when. (probably at the
> most inconvenient time!), and lets not ask what a replacement tube costs!
> 
> There is no perceptible wear mechanisms in play for the 5065A (I have
> seen exactly one failed lamp in many years of working on them) Many of
> the first 1968 series built will still perform to specs today.
> 
> So,
> 
> Just saying!
> 
> Cheers,
> 
> Corby

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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

This note is a follow-up to Ralph Devoe's ADEV posting earlier this month.

It's a long story but last week I was in the Bay Area with a car full of 
batteries, BVA and cesium references, hp counters, and a TimePod. I was able to 
double check Ralph's Digilent-based ADEV device [1] and also to independently 
measure various frequency standards, including the actual 5065A and 5071A that 
he used in his experiment.

For the range of tau where we overlap, his ADEV measurements closely match my 
ADEV measurements. So that's very good news. His Digilent plot [2] and my 
TimePod / TimeLab plot are attached.

Note that his Digilent+Python setup isn't currently set up for continuous or 
short-tau measurement intervals -- plus I didn't have my isolation amplifiers 
-- so we didn't try a *concurrent* Digilent and TimePod measurement.

I'm sure more will come of his project over time and I hope to make additional 
measurements using a wider variety of stable / unstable sources, either down 
there in CA with another clock trip or up here in WA with a clone of his 
prototype. It would be nice to further validate this wave fitting technique, 
perhaps uncover and quantify subtle biases that depend on power law noise (or 
ADC resolution, or sample rate, or sample size, etc.), and also to explore 
environmental stability of the instrument.

I can tell Ralph put a lot of work into this project and I'm pleased he chose 
to share his results with time nuts. I mean, it's not every day that national 
lab or university level projects embrace our little community.

/tvb

[1] http://aip.scitation.org/doi/pdf/10.1063/1.5010140 (PDF)
[2] https://www.febo.com/pipermail/time-nuts/2018-February/108857.html

- Original Message - 
From: "Ralph Devoe" 
To: 
Sent: Monday, February 12, 2018 1:52 PM
Subject: [time-nuts] Allan variance by sine-wave fitting

> I've been comparing the ADEV produced by the sine-wave fitter (discussed
> last November) with that of a counter-based system. See the enclosed plot.
> We ran the test in Leo Hollberg's lab at Stanford, using a 5071a Cesium
> standard and my own 5065a Rubidium standard. Leo first measured the ADEV
> using a Keysight 53230a counter with a 100 second gate time. We then
> substituted the fitter for the counter and took 10,000 points at 20 second
> intervals. The two systems produce the same ADEV all the way down to the
> 5x10(-14) level where (presumably) temperature and pressure variations make
> the Rb wobble around a bit.
> 
> The revised paper has been published online at Rev. Sci. Instr.

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Re: [time-nuts] Teardown of Chinese made eBay GPS antenna.

[Tom Van Baak]

Let's keep this thread on topic and highly informative.

Please treat time nuts as a technical mailing list, not social media.

Thanks,
/tvb
Moderator, www.leapsecond.com/time-nuts.htm

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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

Hi Ralph,

Nice test. Two comments.

1) Your 5065A is working really well; is it one of Corby's "super" ones? What 
sort of environmental controls did you have during the run, if any. How long 
had the 5065A been powered up before you ran the test?

2) Is there a reason you didn't or couldn't make simultaneous measurements 
using both counters? That would have allowed an interesting study of the 
residuals. Plots of phase, frequency, spectrum, and ADEV of the residuals 
provides insight into how well the two counters match. This would also probably 
remove the awkward divergence of your two ADEV plots past tau 1 hour.

/tvb

- Original Message - 
From: "Ralph Devoe" 
To: 
Sent: Monday, February 12, 2018 1:52 PM
Subject: [time-nuts] Allan variance by sine-wave fitting


> I've been comparing the ADEV produced by the sine-wave fitter (discussed
> last November) with that of a counter-based system. See the enclosed plot.
> We ran the test in Leo Hollberg's lab at Stanford, using a 5071a Cesium
> standard and my own 5065a Rubidium standard. Leo first measured the ADEV
> using a Keysight 53230a counter with a 100 second gate time. We then
> substituted the fitter for the counter and took 10,000 points at 20 second
> intervals. The two systems produce the same ADEV all the way down to the
> 5x10(-14) level where (presumably) temperature and pressure variations make
> the Rb wobble around a bit.
> 
> The revised paper has been published online at Rev. Sci. Instr.


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Re: [time-nuts] Anyone have experience with this antenna?

[Tom Van Baak]

oops, sorry for the misfire.

> I couldn't figure out how to get to the insides to take a peek
> without damaging it.

For $99 I would take the risk to damage it... Or find someone with x-ray gear 
and have a peak inside. Or take it with you on your next plane flight and grab 
a photo of the TSA monitor as you pass through.

> My antenna testing abilities are pretty feeble.
> Mostly, I will just compare it to the Leica and Trimble to see how many
> satellites it sees and look at position wander of the uBlox. Is there any
> simple way to judge the quality of a GPS antenna?

That's a good question. It all depends on what you're using it for. If you're a 
mm survey kind of guy then mix that antenna with half a dozen name-brand 
antennae that you already own and trust. See how it stacks up in real-time or 
post-processing benchmarks. I'm a fan of measurement more than specs, so 
collect as much data as you can and share with us.

If you're a time-nut it's more complicated. It's possible you don't have 
anywhere near the kind of equipment that can detect sub-10 ns sort of bias or 
wander or noise. And then there are issues of orientation, elevation, 
linearity, thermal stability, etc. If it's not in the NGS database be 
suspicious. Ref:

https://www.febo.com/pipermail/time-nuts/2018-January/108519.html

/tvb

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Re: [time-nuts] Anyone have experience with this antenna?

[Tom Van Baak]

> testing. I couldn't figure out how to get to the insides to take a peek
> without damaging it. My antenna testing abilities are pretty feeble.
> Mostly, I will just compare it to the Leica and Trimble to see how many
> satellites it sees and look at position wander of the uBlox. Is there any
> simple way to judge the quality of a GPS antenna?
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Re: [time-nuts] Rakon HSO-14

[Tom Van Baak]

FYI: here's an old plot where I evaluated an Oscilloquartz 8607 BVA against a 
H-maser. It gets down to 8e-14 but is likely a bit better. On this plot, I 
suspect the short-term numbers were not the BVA oscillator or the TSC 5110A 
analyzer, but the H-maser.

/tvb
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Re: [time-nuts] CSAC Project(was CSAC purchase)

[Tom Van Baak]

> www.obsip.org/documents/Gardner_IEEE_Oceans_2016.pdf

Also see the very nice presentation:

"Challenges of precise timing underwater"
http://www.ipgp.fr/~crawford/2017_EuroOBS_workshop/Resources/Gardner_OBS_Timing_ATG_20150427.pdf

/tvb
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Re: [time-nuts] minimalist sine to square

[Tom Van Baak]

> Tom
> What's the input signal amplitude?
> What's the desired output signal (eg 5V CMOS, 3.3V CMOS etc)?
> Bruce

It's for a typical 5 or 10 MHz OCXO / Rb / Cs with sinewave output; say, 1 Vpp. 
The output should be 3.3 or 5 V depending on what the MCU needs. It doesn't 
have to have stunning performance: think breadboard, PIC, Arduino sort of 
stuff. I was looking for something in a PDIP-8 package; the same as all the 
picDIV or picPET chips I use. That's why older parts like µA9637 / DS9637 came 
to mind.

/tvb

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Re: [time-nuts] Looking for information regarding Trimble 33429-00 microcentered GPS antenna.

[Tom Van Baak]

> What's in the antenna that makes North interesting?  and/or how would a 
> receiver take advantage of it?

Hal,

The people that work at the mm level get very picky about details; antenna 
reception is not perfectly symmetrical or centered or equal at every frequency 
or angle. There is a massive database of antenna calibrations here:
https://www.ngs.noaa.gov/ANTCAL/

Click on "Browse Antenna Information by Manufacturer and Model", pick some 
vendor, and hover over Drawing, Label, Side, Top. Then see the raw data for the 
calibration. Here's a random example:
https://www.ngs.noaa.gov/ANTCAL/LoadFile?file=TRM105000.10_NONE.atx

Or view a 10 MB database: 
https://www.ngs.noaa.gov/ANTCAL/LoadFile?file=ngs14.atx

See also: https://www.ngs.noaa.gov/ANTCAL/FAQ.xhtml


Here's a couple of random links to give you an idea what this is all about:

"How to Use IGS Antenna Phase Center Corrections"
http://acc.igs.org/antennas/igs-pcvs_gpsworld10.pdf

"ANTENNA PHASE CENTER VARIATIONS CORRECTIONS IN PROCESSING OF GPS OBSERVATIONS 
WITH USE OF COMMERCIAL SOFTWARE"
http://www.uwm.edu.pl/wnt/technicalsc/tech_13/B12.PDF

"Influence of GPS antenna phase center variation on precise positioning"
https://www.sciencedirect.com/science/article/pii/S2090997713000515

"Satellite Antenna Phase Center Offsets and the Terrestrial Scale"
http://www.igs.org/assets/pdf/W2016%20-%20PY0703%20-%20Rothacher.pdf


That will keep you busy for a while.

/tvb

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[time-nuts] minimalist sine to square

[Tom Van Baak]

John's TADD-2-mini [1] uses the Wenzel sine-to-square converter. It performs 
very well but requires +10 V.

I'm looking for a solution that works at 5 V (e.g., USB powered) and also uses 
fewer parts. Wenzel also mentions using a differential line receiver [2]. That 
would be an ideal single-chip 5 V solution for me but the two parts he 
mentions, MC1489 [3] and SN55182 [4], don't appear fast enough for a 10 MHz 
input.

Can any of you circuit experts suggest some line receivers that would work? 
Maybe DS9637 [5]? This isn't for cesium work so it doesn't have to be quite as 
good as the TADD-2.

Thanks,
/tvb

[1] http://www.tapr.org/~n8ur/T2_Mini_Manual.pdf
[2] http://www.wenzel.com/documents/waveform.html
[3] https://www.onsemi.com/pub/Collateral/MC1489-D.PDF
[4] http://www.ti.com/lit/ds/slls092d/slls092d.pdf
[5] http://www.ti.com/lit/ds/symlink/ds9637a.pdf


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Re: [time-nuts] Tbolt 1pps

[Tom Van Baak]

> Has any one done a 24 hour plot of the Tbolt 1pps.

Hi Bert,

There are plots of several GPSDO at http://leapsecond.com/pages/gpsdo/ 
including a Trimble Thunderbolt. It was one of the TAPR TBolt OEM surplus units 
that I measured in 2008. I uploaded the raw data for you here:

http://leapsecond.com/pages/tbolt/log36116.dat.gz
http://leapsecond.com/pages/tbolt/log36149v.gif
http://leapsecond.com/pages/tbolt/log36150v.gif

For log36116.dat the data is phase, units are seconds, sample rate is 1/second, 
resolution is 0.1 ps, duration is just over 400k seconds (112 hours, or 4.7 
days). The data was collected with a TSC 5110A analyzer, the reference was a 
H-maser, and I think the TBolt was in factory defaults (no fancy time constant 
tuning). I removed the arbitrary phase and frequency offsets. Use Stable32 or 
TimeLab to play with the data.

Let me know if this data is what you were looking for, or maybe explain more 
what you're curious about. If you're interested in TBolt tuning, look in the 
archives for postings by Warren S.

/tvb

- Original Message - 
From: "ew via time-nuts" 
To: 
Sent: Wednesday, January 17, 2018 6:57 AM
Subject: [time-nuts] Tbolt 1pps


> Has any one done a 24 hour plot of the Tbolt 1pps.
> 
> 
> Bert Kehren Palm City F.

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Re: [time-nuts] PBS, Tue evening, The Secret of Tuxedo Park

[Tom Van Baak]

I can't stress enough how important Loomis was to the history of precise 
timekeeping in early radio, telephone, pendulum clock, quartz oscillator era. 
And for those of us who still have Loran-C receivers can thank him (Loomis 
Radio Navigation -> LRN -> Loran).

So I highly recommend the 2003 book "Tuxedo Park" by Jennet Conant:
http://www.simonandschuster.com/books/Tuxedo-Park/Jennet-Conant/9780684872889

Our kind of guy. In the "Palace of Science" chapter she writes: Loomis would 
remain a "time nut" for the rest of his life, according to Luis Alvarez, who 
recalled that Loomis always wore "two Accutrons--one on his right wrist and one 
on his left wrist." He would check them every day against WWV (the standard 
frequency broadcasting station of the National Bureau of Standards), and if one 
was gaining a half second on the other, he would wear it on the outside of his 
wrist instead of the inside, so that gravity changed the rate of the tuning 
fork and the two watches tracked each other, and WWV, "to within less than a 
second a day."



Some other Loomis links of interest:

https://en.wikipedia.org/wiki/Alfred_Lee_Loomis
https://en.wikipedia.org/wiki/LORAN
https://timeandnavigation.si.edu/navigating-air/navigation-at-war/new-era-in-time-and-navigation/alfred-loomis
http://www.ob-ultrasound.net/loomis.html
http://leapsecond.com/pages/loomis/


And the clever way to do time transfer and compare precision clocks to 1 ms in 
the 1930's...

http://leapsecond.com/pend/shortt/1931-RAS-Precise-Measurement-Time-Loomis.pdf


Also the classic "The Evolution of the Quartz Crystal Clock" by Warren A. 
Marrison:

https://ieee-uffc.org/about-us/history/uffc-s-history/the-evolution-of-the-quartz-crystal-clock/
via https://ieee-uffc.org/about-us/history/uffc-s-history/
and original at https://archive.org/details/bstj27-3-510


If someone knows how to record any time/clock/navigation parts of PBS show for 
non-US viewers let me know, off-list.

/tvb


- Original Message - 
From: "Hal Murray" 
To: 
Cc: "Hal Murray" 
Sent: Tuesday, January 16, 2018 1:42 AM
Subject: [time-nuts] PBS, Tue evening, The Secret of Tuxedo Park


> (Sorry for the clutter to those of you outside the US.)
> 
> http://www.pbs.org/wgbh/americanexperience/films/secret-tuxedo-park/
> Two of the shorts mentions time.
> 
> Many thanks for the Tuxedo Park book suggestion many years ago.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 

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Re: [time-nuts] hp 5245L counters with 10544 and 10811 OCXOs

[Tom Van Baak]

And for anyone working on the 10544 oscillator, Charles Steinmetz writes:

> The errors HP made in the 10544 schematics are grave enough that it may 
> be a good idea to post my corrected schematic wherever folks who need to 
> work on the oscillators are likely to look for service information, so 
> they might be spared the confusion that HP's original schematics can 
> cause.
>
> To this end, please feel free to post the corrected schematic
> on your 10544 page if you want.  I'm also attaching a description of the 
> schematic errors, and a document describing the differences between 
> 10544 and 10811 connections. Feel free to post these on leapsecond.com, 
> as well.

I've place Charles' PDF's at http://leapsecond.com/museum/10544/

Well worth the read. Thanks Charles.

/tvb

- Original Message - 
From: "Loney Duncan" <lon...@sbcglobal.net>
To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time and 
frequency measurement" <time-nuts@febo.com>
Sent: Tuesday, January 09, 2018 5:54 PM
Subject: Re: [time-nuts] hp 5245L counters with 10544 and 10811 OCXOs


Tom,

I'm very grateful for your immediate response, and all that you sent me. 
The last four PDFs are exactly what I need to understand and troubleshoot 
the ailing adapter board.  This is my first experience with Time Nuts, and 
I'm impressed.

Again, many thanks!
Loney

-Original Message- 
From: Tom Van Baak
Sent: Monday, January 8, 2018 11:19 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] hp 5245L counters with 10544 and 10811 OCXOs

Loney,

You'll find the schematic for the 05245-60033 adapter board at the bottom 
of:

http://leapsecond.com/museum/10544/

/tvb

- Original Message - 
From: "Loney Duncan" <lon...@sbcglobal.net>
To: <time-nuts@febo.com>
Sent: Monday, January 08, 2018 8:08 PM
Subject: [time-nuts] hp 5245L counters with 10544 and 10811 OCXOs


Gentlemen:

I have two 5245L counters which appear to have had a field mod where the 
original 1 MHz cylindrical oven standard has been replaced by the 10544 and 
10811 10 MHz ones.  Both counters have late 4-digit serial prefixes.  Both 
of the standards plug into an interface circuit board that, among other 
things, appears to have a divide by 10 circuit to produce a 1 MHz output to 
the counter’s oscillator card as the old cylindrical oven standard did. 
This card for both has an hp p/n 5245-60033.

My 10811 counter works well, but the 10544 unit has a troublesome 
intermittent problem that appears to be on the board.  I cannot find a 
schematic and parts list for this board to troubleshoot and repair it. 
These probably were on a change insert into the counter Service Manual, but 
I’ve yet to find one.  Have checked on Keysight’s website with no success.

Would anyone in this group possibly have these, or point me to an archive 
that would?  I very much would like to have the 544 unit function.  I have 
observed that after many decades of aging, a lot of the old original oven 
standards are out of adjustment range, while my 544 and 811 OCXOs can still 
be adjusted.

Thanks very much for your advice.

Loney Duncan  W0GZV


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Re: [time-nuts] hp 5245L counters with 10544 and 10811 OCXOs

[Tom Van Baak]

Loney,

You'll find the schematic for the 05245-60033 adapter board at the bottom of:

http://leapsecond.com/museum/10544/

/tvb

- Original Message - 
From: "Loney Duncan" 
To: 
Sent: Monday, January 08, 2018 8:08 PM
Subject: [time-nuts] hp 5245L counters with 10544 and 10811 OCXOs


Gentlemen:

I have two 5245L counters which appear to have had a field mod where the 
original 1 MHz cylindrical oven standard has been replaced by the 10544 and 
10811 10 MHz ones.  Both counters have late 4-digit serial prefixes.  Both of 
the standards plug into an interface circuit board that, among other things, 
appears to have a divide by 10 circuit to produce a 1 MHz output to the 
counter’s oscillator card as the old cylindrical oven standard did.  This card 
for both has an hp p/n 5245-60033.

My 10811 counter works well, but the 10544 unit has a troublesome intermittent 
problem that appears to be on the board.  I cannot find a schematic and parts 
list for this board to troubleshoot and repair it.  These probably were on a 
change insert into the counter Service Manual, but I’ve yet to find one.  Have 
checked on Keysight’s website with no success.

Would anyone in this group possibly have these, or point me to an archive that 
would?  I very much would like to have the 544 unit function.  I have observed 
that after many decades of aging, a lot of the old original oven standards are 
out of adjustment range, while my 544 and 811 OCXOs can still be adjusted.  

Thanks very much for your advice.

Loney Duncan  W0GZV


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Re: [time-nuts] HP 58503A question (EFC: Err)

[Tom Van Baak]

Mitch,

Thanks for the screen shot. That means 99% of your 58503 is working; very good 
news.

If you look at the last line if your screen shot (attached), the self-test is 
failing due to EFC (Electronic Frequency Control), the voltage that pulls the 
quartz oscillator low or high to keep it locked at 10 MHz via GPS. The manual 
suggests this means the oscillator has drifted out of range, but there may be 
additional causes like the DAC or its bipolar power supply or the oscillator 
oven or oven power supply, etc.

I've not seen this error before on my 58503's, but it narrows down your problem 
significantly. Rather than guessing what the root cause is I'll cc time-nuts 
[1] to see if anyone else has seen this error, or knows what you can do about 
it.

There's also a useful thread at: 
www.eevblog.com/forum/testgear/hp-58503a-efc-error/

/tvb

[1] I see your original email went to time-nuts-owner@, which ends up going 
privately to the couple of us who run time-nuts. But if you post to 
time-nuts@febo.com, then it goes out to the 1800 member list.

If you want to join see http://www.leapsecond.com/time-nuts.htm for details 
about the list.

If you don't want to bother joining you can read the live feed for this month 
at: www.febo.com/pipermail/time-nuts/2018-January/date.html

If you want to read anything every written about the 58503A, on time-nuts 
search google using-- site:febo.com 58503A



- Original Message - 
From: Mitch Van Ochten 
To: 'Tom Van Baak' 
Sent: Thursday, January 04, 2018 7:21 PM
Subject: RE: HP 58503A question


Hi Tom,
 
This unit has the display also.  After applying power, the LED's on the front 
do a scan from left to right, the display says "HP 58503A" then the "STATUS" 
LED starts blinking once per second.  Thirty seconds later a message appears 
saying "SLFTST ERR".  The same instant the leftmost RED LED at the left rear of 
the circuit board comes on.
 
There is a GREEN LED (rightmost) in the set of six LED's, which continuously 
blinks once per second.  The 10 MHz output is present and the RS-232 is working.
 
After clearing the alarm, the "OCXO WARMUP" message appears, then a few minutes 
later a message saying "GPS FAILED" occurs. After waiting a while another 
message says "0 SAT AQUIRD". Regardless of how long you wait, it always says "0 
SAT AQUIRD".
 
I have the unit attached to a known good active antenna.  Bought a replacement 
GPS receiver for it and installed it but the same error still appears. It seems 
as though it is not recognizing the signal from the GPS receiver, and it may be 
related to the self-test error.
 
Here is what SatStat shows:
 
 
 
 
Best regards,
 
mitch
 
From: Tom Van Baak [mailto:t...@leapsecond.com] 
Sent: Thursday, January 04, 2018 9:21 PM
To: mitch
Subject: Re: HP 58503A question
 
I opened one up here and it also has no chip in that socket. I never noticed 
that before. If you want me to dig further I will.
What test failed? Or what are the other symptoms? Do you get 10 MHz or 1PPS or 
GPS lock?
Have you tried querying it with the RS232/ SCPI interface?
 
/tvb
 
- Original Message - 
From: Mitch Van Ochten 
Sent: Thursday, January 04, 2018 5:02 AM
Subject: HP 58503A question
 
Hi John,
 
I recently acquired an older HP 58503A.  After power-up the "status" LED blinks 
for about 30 seconds, then a message comes up saying it failed self-test.  
Inside it is missing a large IC (see attached photo).  Do you have one of these 
units?  If so, is yours also missing the IC?
 
 
Best regards,
 
Mitch Van Ochten

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Re: [time-nuts] Trimble Thunderbolt Power Cable Needed

[Tom Van Baak]

> I have a dead T-Bolt that I want to trouble-shoot, but my only
> 
> Power Cable is in use, so I need another Power Cable.
> 
> Anyone have a spare that they are willing to part with ?
> 
> Thanks, Dick, W1KSZ

You can improvise using any 0.1 inch headers you have lying around. See 
"Alternative Connectors" at:
http://leapsecond.com/pages/tbolt/power.htm

If you don't want to do that, contact me off-list [1] and I'll send you a 
ready-made power cable left over from the group buy years ago.

/tvb

[1] t...@leapsecond.com

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Re: [time-nuts] Stable32 now available

[Tom Van Baak]

I asked Bill for clarification and here's some of what he shared:

> Tom:
>
> I’m glad that the word is getting out that Stable32 is now freely available.

> The Version 1.62 that is available for download from the IEEE UFFC site is
> identical to the last commercial Version 1.61 except for its UFFC labeling.
> It is a Windows installation file with the executable, ancillary files and
> documentation just like the commercial installation download or CD-ROM.
> The printed User Manual can still be bought as before.

> My donation to the IEEE UFFC included all source code, and it is up to them
> to decide whether and how to make it available.  That has not yet been done.

> My motivation was to see that it lived at least in its present form without
> my having to remain involved.  I will continue to support the commercial
> version for a year more, but not the free one.

> The IEEE UFFC Stable32 distribution is  released under a form of the “MIT
> License” which is as free as can be.  That was made possible last year by
> Scientific Endeavors Corporation who agreed to end my obligations under a
> royalty payment agreement for the GraphiC scientific plotting functions that
> Stable32 uses.  No other such issues exist for the Stable32 distribution, so
> it became possible to make it free.

> The Stable32 source code is organized into two basic parts, the top-level 
> Windows
> user interface and a DLL that contains the core analysis functionality.  It is
> likely that the latter is the more valuable for future versions and other 
> purposes.
> For example, I have ported that Windows FrequenC.dll (which is distributed 
> with
> Stable32) to Linux as a libfrequenc.so shared object library that can be used 
> by
> GCC/G++.  I have also created a wrapper function for that so it can be used 
> with
> Python.  I hope to make these (and the critical FrequenC function 
> documentation)
> available soon.

> I hope this explains things a bit.  The Stable32 distribution package is now 
> freely
> available for all to use.  The Stable32 source code is under the control of 
> the
> IEEE UFFC AdCom.  I plan to make the core Stable32  FrequenC Library 
> documentation
> and functionality available for Windows, Linux and Python.
>
> Best regards,
> Bill Riley

My comments:

1) I use both Stable32 and TimeLab equally; and now that Stable32 is free, 
everyone can now enjoy both of them too. They overlap somewhat, but each has 
its own set of strengths and target audience. Both show evolutionary bloat by 
now but for the small subset of features one typically uses the learning curve 
is not high. Each includes a comprehensive user guide. Both are native Windows 
apps, and run under emulation on Unix.

2) Bill is already working the issues of github / open source / licensing / 
tool chain / cross-platform support so we should hear further developments over 
the next year. I was especially happy to hear about his plans for Python. So 
hang on a while for the open source part; for now enjoy your free copy of 
Stable32. And for those of you not familiar with Bill's career of time & 
frequency work please make a point to browse the papers on his 
http://wriley.com (or http://stable32.com mirror).

/tvb


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Re: [time-nuts] Stable32 now available

[Tom Van Baak]

> From "Paul Alfille" :
> Is the code be available, or just the compiled binary?

I've asked Bill for clarification and will relay any information.


> From "paul swed" 
> I suspect we need a Stable32 for dummies book.

When I first started using Stable32 I tried to document each step. See examples 
like:

http://leapsecond.com/pages/ahm-phm/maser1.htm
http://leapsecond.com/pages/doug-rb/
http://leapsecond.com/pages/osa8607-dat/
http://leapsecond.com/pages/hp5065-dat/
http://leapsecond.com/pages/8607-drift/


> From "Magnus Danielson" 
> Now, the code needs to be maintained. I personally also would like to
> see it run natively on Linux, it does run on Linux under Wine.

Stable32 seems highly integrated with the "graphic/win" plotting package 
(www.sciend.com). That may be one of the problems porting the code to unix. But 
hang on, and we'll let Bill tell us for sure.


> From "Dr. David Kirkby" 
> Perhaps someone who has both the book and the software, would comment if
> the book is very out of date, or would still be useful.

The book is wonderful. The software hasn't fundamentally changed.
Bill also maintains a fantastic site at http://www.wriley.com/ where you will 
find 100+ documents worth reading.

/tvb

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Re: [time-nuts] Recently acquired 53132A

[Tom Van Baak]

Rick,

The 53132A is a "12 digit/s" counter. Unless the frequency is really close to 
10 MHz. Then it becomes a 11 digit/s counter. This is because it uses 
oversampling (IIRC, 200k samples/s) and it relies to some extent on statistics 
for its 12 digit resolution.

This technique does not do as well when DUT is too closely aligned in phase and 
frequency with REF. I mean, you can oversample all you want, but when the two 
clocks appear locked most of those samples are redundant; they offer no 
statistical advantage. Hence the reduced resolution. By a factor of 10!

The nice thing about the 53131/53132 is that this condition is recognized in 
f/w and the output resolution is pruned automatically. If you have long log 
files of an oscillator warming up you can see it quite nicely.

Note also that it's not just when DUT is 10 MHz or near 10 MHz; there are 
hundreds of magic frequencies where reduced resolution occurs: any rational 
fraction or multiple of that's within about 7 digits of 10 MHz. This is not 
undocumented. Buried in the manual is:

http://leapsecond.com/pages/53132/53132-reduced-resolution.gif

Also, the issue isn't unique to the 53132A. Any counter or software that uses 
oversampling has to face this effect [1]. That is, you can't blindly assume 
your resolution always improves by sqrt(N). As obscure as this effect is, I'm 
really impressed hp put so much thought into it. It's one reason I have a lot 
of trust in the 53132A.

Finally, at the risk of mentioning noise, measurement, and ADEV here, you can 
also guess that this clever oversampling measurement technique has 
ramifications on the fidelity of ADEV calculations made from frequency 
readings. Check previous posts, probably from Magnus, that discusses this [2].

/tvb

[1] One way to avoid or reduce the chances are to use an obscure frequency for 
REF. Another way is to deliberately apply carefully characterized jitter to DUT 
or REF during measurement. You can see the connection with DMTD systems, or 
TimePod.

[2] See papers like:

"On temporal correlations in high–resolution frequency counting", Dunker, 
Hauglin, Ole Petter Rønningen (!!!)
https://arxiv.org/pdf/1604.05076.pdf

"High resolution frequency counters", E. Rubiola
http://rubiola.org/pdf-slides/2012T-IFCS-Counters.pdf

"The Ω counter, a frequency counter based on the Linear Regression", 
Rubiola, Lenczner, Bourgeois, Vernotte
https://arxiv.org/pdf/1506.05009.pdf

"Isolating Frequency Measurement Error and Sourcing Frequency Error near 
the Reference Frequency Harmonics"
http://literature.cdn.keysight.com/litweb/pdf/5990-9189EN.pdf



- Original Message - 
From: "Richard (Rick) Karlquist" 
To: "Discussion of precise time and frequency measurement" 
; "Pete Lancashire" 
Sent: Monday, December 18, 2017 1:33 PM
Subject: Re: [time-nuts] Recently acquired 53132A


> I worked in the HP Santa Clara Division frequency counter
> section at the time of the development of the 53132A series, which had 
> the internal code name of "Major League Baseball".  IIRC, the external
> reference circuit in it was designed by a couple of
> engineers who had no background in time nuttery and
> did a mediocre job.  Someone else commented on a problem
> with it not wanting to measure 10 MHz correctly.  I
> never heard of that before, but it would not surprise
> me, because the main measurement engine was designed
> by a very excellent FPGA engineer without an extensive
> background in time nuttery.  The problem mentioned might
> have been too subtle.
> 
> The 53132 has many good points but is not perfect.
> 
> Rick


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Re: [time-nuts] Recently acquired 53132A

[Tom Van Baak]

Pete,

I don't recall that anyone complained much about the old 53132A, the counter 
that you have.

The discussions we had about external reference a while ago were about new 
53230A. There's nothing wrong with it, I mean, it's a very nice counter, but 
since it's a fancy, new design, high-end, 20 ps counter some of us had equally 
high expectations about the purity of the input or output reference, or other 
subtle details of its operation.

/tvb


- Original Message - 
From: "Pete Lancashire" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, December 18, 2017 11:23 AM
Subject: [time-nuts] Recently acquired 53132A


> Friday I acquired a 53132A
> 
> https://photos.app.goo.gl/xexnJcEmT8tEWXi73
> 
> It does not have any options.
> 
> It is from a place that sells "selected" E-waste. I was in a water damaged
> box, and was from a DHL freight insurance sale. It's been in the box until
> a couple weeks ago.
> 
> Anyway, until now I've not followed the conversation on the issues with
> using the External Reference, which I would like to do. But don't see if
> there
> were any conclusions or anything that could be done other then the issues
> where fixed in the "B" version.
> 
> Is there a problem and a 'fix' that I missed searching the archives ?
> 
> -pete
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Re: [time-nuts] Oscilloquartz 8600-3 Disassembly pictures...

[Tom Van Baak]

Ulf Kylenfall photos:
http://leapsecond.com/museum/osa8600/
http://leapsecond.com/museum/osa8600/view.htm


Ed Palmer text and photos:
http://leapsecond.com/museum/osa8601/
http://leapsecond.com/museum/osa8601/view.htm


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Re: [time-nuts] accurate 60 hz reference chips/ckts

[Tom Van Baak]

I sent a note to Vlad off-list about the bug in the MCU code, but it's worth a 
reminder to the list as well since many of you are programmers and this arcane 
issue comes up every once in a while here and on the web.

The way to compute time differences of free-running binary time counters is 
subtraction. One line of code. There is no need to special case overflow / 
rollover / wraparound. It is the very nature of unsigned or 2's compliment 
signed binary arithmetic that subtraction is sufficient. So the bug-free code 
is just this:

 uwIC2Value2 = (HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_1));
 uwDiffCapture = (uwIC2Value2 - prevtimer);
 prevtimer = uwIC2Value2;

If you'd like a simple example why this is correct and a demonstration of what 
the bug was, see:

http://leapsecond.com/tools/deltatim.c

/tvb

- Original Message - 
From: "Vlad" 
To: "Jeremy Nichols" 
Cc: "Discussion of precise time and frequency measurement" 
Sent: Friday, December 15, 2017 9:41 AM
Subject: Re: [time-nuts] accurate 60 hz reference chips/ckts



My setup is pretty simple indeed. This is 9.830400MHZ OCXO which 
clocking MCU. Then it is Zero-Cross detector which connected to capture 
timer.
The MCU counting the intervals between of each zero-cross event and 
number of events occurred.

 if (htim->Instance == TIM5 && htim->Channel == 
HAL_TIM_ACTIVE_CHANNEL_1) {
 uwIC2Value2 = (HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_1));
 if (uwIC2Value2 >= prevtimer) {
 uwDiffCapture = (uwIC2Value2 - prevtimer);
 } else {
 uwDiffCapture =((0x - prevtimer) + uwIC2Value2);
 }

 prevtimer = uwIC2Value2;

 // MAIN Time calculation
 if(++uwCapT > 59) {  // Every 60 cycles (60hz)
 if(++maintime.Seconds > 59) {
 maintime.Seconds = 0;
 if(++maintime.Minutes > 59) {
 maintime.Minutes = 0;
 if(++maintime.Hours > 23)
 maintime.Hours = 0;
 }
 }
 uwCapT = 0;
}

Once an hour the program prints its internal clock (MCU time), RTC time 
and MAIN time

# Uptime:   476 hours
# RTC time: 13:00:00
# MCU time: 13:00:00
# MAIN time:13:00:01

The graph shows the "delta" between of RTC and MAIN.


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Re: [time-nuts] accurate 60 hz reference chips/ckts

[Tom Van Baak]

Pat,

> They drift a few seconds in the course of a few days, and wander back and 
> forth.  

Yes, it's normal for AC mains to drift around by a few seconds over a day but 
it usually stays roughly on-time over weeks and months. Here's an old example 
of monitoring mains time & frequency for 45 days:

http://leapsecond.com/pages/mains/

> Does a TCXO or similar exist in a small package that provides 60 hz ticks?

If you have 10 MHz (XO, TCXO, etc.) you can convert to 60 Hz using a $1 PIC 
divider:

http://leapsecond.com/pic/src/pd60.asm
http://leapsecond.com/pic/src/pd60.hex

/tvb

- Original Message - 
From: "Patrick Barthelow" 
To: "Discussion of precise time and frequency measurement" 
Sent: Thursday, December 14, 2017 8:42 AM
Subject: [time-nuts] accurate 60 hz reference chips/ckts


> PIcked up a couple of  large size Radio Shack  63-960 LED clocks with
> Settable alarm, at local Goodwill store. $3.00 ea work great see across
> room, loud Alarm, etc...
> 
> 
> Barely missed, by seconds, getting a classic Hallicrafters General coverage
> receiver
> (not like say, S-38) but a larger light green metal box. nearly perfect
> condx.  $25.00  with the famous h logo speaker  probably late 50s Vintage.
> :-(   Dang...
> Checked LED clocks by ear and eye with WWV, They drift a few seconds in
> the course of a few days, and wander back and forth.  Thought AC mains
> frequency was tighter than that. They use  an LM 8560 Clock chip.  Uses a
> switchable AC mains frequency reference pin  50/60 hz.
> Want to provide an accurate  (relatively accurate) 60 hz reference to the
> chip.   Some room inside for custom modifications.  Does a TCXO or similar
> exist in a small package that provides 60 hz ticks?
> 
> Best, 73,   Pat Barthelow AA6EG
> apol lo...@gmail.com
> 
> 
> *"The most exciting phrase to hear in Science, the one that heraldsnew
> discoveries,  is not "Eureka, I have found it!"but:*
> "That's funny..."  Isaac Asimov

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Re: [time-nuts] Pendulum clock suspension

[Tom Van Baak]

List -- we don't normally do wrist watch or pendulum topics here on time-nuts. 
There are many publications [1] and forums [2] for that

Iovane -- but, here's a quick answer:

> This puzzled me since yesterday as I discovered how the suspension of 
> pendulum clocks is made, that is a springy plate.
> I thought that:
> -the suspension point (i.e. the point the pendulum moves about) cannot be 
> considered fixed,
> -following the above, the lenght of the pendulum varies during a swing,
> -the spring contributes to the oscillation (it cumulates and releases 
> energy), i.e. not only gravity at work..
> Ok that we can neglect the above yet having an extremely good approximation, 
> but is it conceptually right?
> Thanks for the answers.

When you get to 0.1% or ppm or ppb levels, there is a huge difference between 
pendulum motion as described in physics textbooks vs. how real or precision 
pendulum clocks operate.

Correct, it's not all gravity; the spring suspension itself has some effect on 
the motion of the pendulum. If this is a problem then you make design decisions 
about spring length, width, thickness, taper, or what metal to use. Or make the 
bob heavier, or choose a different operating amplitude. Or skip the spring 
entirely and use agate or diamond pivot suspension. All of this can be worked 
out with math or with experimentation.

Correct, the effective length of a pendulum may vary during the swing. This is 
due to the geometry of the suspension, flexure in the rod, and changes in 
buoyancy. And even if the length were constant, the pendulum is still not 
isochronous, due to "circular error". Hence the preoccupation with amplitude 
stability as well as length stability.

In general you should not neglect anything until you have modeled or measured 
it. Also don't confuse accuracy with stability. A pendulum could swing in a 
"figure 8" for all I care, but as long as it does so consistently it can be a 
good timekeeper. It's possible that some of the effects you describe affect 
accuracy more than stability.

Given your curiosity about pendulum clocks, I strongly suggest you subscribe to 
HSN and order the digital archive. These topics are covered in extreme detail 
there. You will be amazed.

/tvb

[1] Some pendulum clock resources:
AH (Antiquarian Horology), www.ahsoc.org
HJ (Horological Journal), British Horological Institute, 
bhi.co.uk/horological-journal
NAWCC (National Association of Watch & Clock Collectors), www.nawcc.org
HSN (Horological Science Newsletter), NAWCC chapter 161, www.hsn161.com

[2] There are also many clock and pendulum web sites, web forums, and mailing 
lists. Contact me off-list.


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Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[Tom Van Baak]

Mark,

> In the standards definitions that include "at sea level", the question these 
> days is "which sea level?".

Chris,

> So does that mean e.g. NIST and BIPM need to measure the acceleration at
> their respective locations to within parts in 10^17 or 10^18 in order to
> compare their frequency standards?

Yes, all national timing labs do this to one degree or another. To operate and 
compare clocks at that level of precision you need to accurately know your 
geopotential, which is sort of like knowing the acceleration of gravity, or 
elevation.

But it's not one-to-one as you suggest. A 1 meter change in elevation 
corresponds to a frequency offset of about 1e-16. So for 1e-18 levels of 
performance you "only" need to know g, or your elevation to 1 cm accuracy.

> That seems not practical.

It is practical, and necessary, and really cool!

Here are some papers that will give you an idea how much work it takes to make 
clocks at the 1e-16 and 1e-17 level. I mean, it's not like you just throw some 
cesium atoms in a bottle, rub the lamp, and out comes a genie singing 
9192.631770 MHz.

These two examples describe the complexity of a primary cesium standard:

"Accuracy evaluation of the primary frequency standard NIST-7", 2001
http://tf.nist.gov/timefreq/general/pdf/1497.pdf

"Accuracy evaluation of NIST-F1", 2002
http://tf.nist.gov/timefreq/general/pdf/1823.pdf

In the first paper, see especially tables 1, 3 and 4 for an idea of the 
corrections they must apply. You'll notice that the largest correction is 
gravitational. Therefore part of their job in making a primary standard is to 
measure gravity at the exact point where the cesium atoms operate. And yes, 
that gets you in the dirty world of what's underground, what mountains are 
nearby, where's the water table this week, what shape the earth really is, and 
the phase of the moon, etc.

These two examples describe the complexity of precisely measuring gravity in 
order to calibrate an atomic clock:

"The relativistic redshift with 3 × 10−17 uncertainty at NIST, Boulder, 
Colorado, USA", 2003
http://tf.boulder.nist.gov/general/pdf/1846.pdf

"A re-evaluation of the relativistic redshift on frequency standards at NIST, 
Boulder, Colorado, USA", 2017
http://tf.boulder.nist.gov/general/pdf/2883.pdf

Really, all four papers are worth a quick read, even if you just look at the 
tables and photos.

/tvb

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Re: [time-nuts] Trimble Mini-T Timing Glitches

[Tom Van Baak]

Leo,

About GPS and 1 ms...

1) Bob's version:

Bob's succinct description is fine. There is often a 1 ms loop in GPS receiver 
firmware (you can see this in the spec for some timing receivers). It is not 
impossible that off-by-1 errors would occur at this level.

2) Book version:

> Fundamentals of Global Positioning System Receivers: A Software Approach
>
> CHAPTER FIVE
> GPS C/A Code Signal Structure
>
> The C/A code is a bi-phase modulated signal with a chip rate of 1.023 MHz.
> Therefore, the null-to-null bandwidth of the main lobe of the spectrum is 
> 2.046
> MHz. Each chip is about 977.5 ns (1/1.023 MHz) long. The transmitting 
> bandwidth
> of the GPS satellite in the L1 frequency is approximately 20 MHz to
> accommodate the P code signal; therefore, the C/A code transmitted contains
> the main lobe and several sidelobes. The total code period contains 1,023 
> chips.
> With a chip rate of 1.023 MHz, 1,023 chips last 1 ms; therefore, the C/A code
> is 1 ms long. This code repeats itself every millisecond. The spectrum of a 
> C/A
> code is shown in Figure 5.2.
>
> In order to find the beginning of a C/A code in the received signal only a
> very limited data record is needed such as 1 ms. If there is no Doppler effect
> on the received signal, then one millisecond of data contains all the 1,023 
> chips.
> Different C/A codes are used for different satellites. The C/A code belongs to
> the family of Gold codes,(5) which will be discussed in the next section.
>
> Figure 5.3 shows the GPS data format. The first row shows a C/A code with
> 1,023 chips; the total length is 1 ms. The second row shows a navigation data
> bit that has a data rate of 50 Hz; thus, a data bit is 20 ms long and contains
> 20 C/A codes. Thirty data bits make a word that is 600 ms long as shown in
> the third row. Ten words make a subframe that is 6 seconds long as shown in
> row four. The fifth row shows a page that is 30 seconds long and contains 5
> subframes. Twenty-five pages make a complete data set that is 12.5 minutes
> long as shown in the sixth row. The 25 pages of data can be referred to as a
> superframe.

3) Tom's haiku version:

atomic clocks fly
coded signals drop from space
position is time

/tvb

- Original Message - 
From: "Bob kb8tq" 
To: "Discussion of precise time and frequency measurement" 
Sent: Thursday, November 30, 2017 2:14 PM
Subject: Re: [time-nuts] Trimble Mini-T Timing Glitches


Hi

I’d freely admit it is *very* much the “Cliff notes” version of what is 
happening.

Bob

> On Nov 30, 2017, at 4:31 PM, Leo Bodnar  wrote:
> 
> Bob, this is quite an unorthodox description of how GPS works.
> You probably want to rephrase that before it gets ripped to shreds.
> Leo
> 
> From: Bob kb8tq 
>> GPS extracts time and location by locking on to various codes in the 
>> transmissions. 
> One of them happens to run at about a 1 KHz clock rate. A slip on that part 
> of the 
> process gives you a (modulo) 1 ms clock jump. Certain types of interference 
> may
> “help” the receiver make these sorts of mistakes.
> 


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Re: [time-nuts] Input filter for data logger

[Tom Van Baak]

> I'll need to experiment with this. I think the drawback cold be for the 
> signal with long pulse width (more than one second). 
> __|~~~

I'm not sure I understand. If you're building some kind of time interval 
counter or timestamp counter the duration is only limited by how many digits or 
bits you allocate to your timestamp. Longer than one second should be very easy.


>> That's a software problem for sure. Do you use interrupts? Or some
>> library code for formatting and output?
> 
> STM32 has an internal counter which counting MCU ticks (I clocked my 
> stone by 40Mhz. So, it will be 40 mln. ticks per second). I am using 
> this ticks number to get microseconds as signal capture event has 
> occurred.

That sounds fine.


> My other timer generate interrupt each second. This is used to start 
> count the microseconds over again. So, its pretty simple.

This could be trouble. You'll have to check for timing windows in your code. 
It's usually better to let counters free-run rather than to start / stop / 
reset them all the time.


> I'll need to dig this issue deeper, since its occurred only when I was 
> using DDS generator as a signal source. I know DDS chips sometimes 
> generates some spurs. But not sure if this is related.

> If I raise the input freq. to 1Mhz, the STM32 become unresponsive, since 
> number "capture" interrupts is too high. The signal capture interrupt 
> routine doing nothing more than one assignment : "cur_tick = 
> DWT->CYCCNT"

Make sure this assignment is atomic (a single load/store pair, not multi-byte 
or multi-word instruction sequence); very timer and cpu dependent.

You don't want unresponsive. When you get an event, capture the timer, format 
your output, and do the serial transmit. Only when that's all finished then 
re-enable for the next event. This avoids lock-up. And it means your CPU 
saturates at the point where your output rate is a maximum. So it's self 
regulating. Note if you do all your event processing in the interrupt handler 
and cur_tick is not used at main level, you don't have to worry about atomic 
loads and stores either.

Another way around all of this is to use capture/compare registers. Most uC 
have this feature. This way your precise timing is not at all dependent on 
interrupt latency or what language you write in.


> has no 32bit timers. Using 40Mhz clock, I can't go low than 610Hz 
> without some tricks, like using pre-scaler or cascading the timers. I 
> tried those methods but results was not impressive. Probably because of 

One solution is to use h/w timers for the low bits and s/w overflow counters 
for the high bits. For example a 64-bit counter could be made using a 16-bit 
timer and a 48-bit overflow count. This is an overflow every 1.6 ms, which is 
easy to deal with using either interrupts or polling.


> my software implementation. I am using DMA and other timer to capture 
> 1PPS events. It works OK for me. But in that case I just need one 
> number. Which ideally should be 23040 in my case (4000 % 65536 = 
> 23040). I don't care about number of overflows and anything else in this 
> case. If I am getting something different from magic number - its time 
> to tweak DAC to control OCXO.

Right, if this is just for a GPSDO then you can consider modulus tricks like 
this. If you're making a more general purpose time interval counter or time 
stamping counter then you can't rely on that trick. I'm not sure of the context 
for this thread. It sort of seemed like you were building a counter.

Then again, even if this is a GPSDO I would not want to rely on magic number 
tricks. What happens if the user decides to change antenna length in order to 
move the 1PPS by hundreds of us? The magic trick will now cause great trouble. 
You can avoid that with a FLL instead of PLL version of GPSDO and ignore what 
look like glitches. But this is now adding hack upon hack. My advise is just 
implement a 0 to 1.x second TIC. It can't be that hard to do that in a STM32.

/tvb

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Re: [time-nuts] Input filter for data logger

[Tom Van Baak]

Hi Vlad,

> However, the logger measure it TWICE ! I think its because of that 
> signal form. Here is the output (in microseconds):

Assuming the STM32 is set to trigger on the rising edge, a 2x output will occur 
if there is bounce from a falling edge. Normally this is not desirable, but 
there are cases where measuring both rising and falling edge improves 
resolution. For example I have a version of the picPET that timestamps both 
edges (this gives you pulse width and duty cycle information). The CNT-91 
counter also does this in raw timestamp mode.

> 26.5837255
> 26.23559295
> 26.5941842

> However, it is some "spikes" in the data flow (see above the number 
> "26.23559295", which suppose to be something as "26.58..."). I can't 
> understand the reason for that.

That's a software problem for sure. Do you use interrupts? Or some library code 
for formatting and output?

> I would assume, some improvement needs to be done for the data logger 
> input. I am using 2N5485 and 74AC04 elements there. Any advises will be 
> appreciated ! Thanks !

It sounds like you have two problems: 1) h/w signal conditioning before the 
STM32, and 2) a s/w timing issue in your code or in how you use the USART. To 
separate them, try a clean square wave directly into the STM32 over a range of 
frequencies from slow to fast to faster than the STM32 can keep up.

BTW, the good news is that your time stamping output looks like the picPET -- 
http://leapsecond.com/pic -- which means that you can use TimeLab to directly 
capture and/or display all your data (phase, frequency, adev, etc.).

Note the picPET outputs a h/w event counter along with the timestamp. This can 
be ignored but the counter helps identify noisy inputs, allows one to 
distinguish between fast and too-fast inputs, and was very useful during 
development to validate the accuracy of the device.

As an example, the old PIC I'm using is limited to 125 samples per second 
(mostly due to RS232 transmit time at 19,200 baud), but with an 8-bit event 
count you can directly measure frequencies up to 256 times greater (32 kHz). 
With a 16-bit event counter that number climbs to 8 MHz. All this without a 
pre-scaler.

/tvb

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Re: [time-nuts] Interpreting and Understanding Allen DeviationResults

[Tom Van Baak]

Jerry:
> For time interval as discussed below, the unaltered GPSDO output goes to A and
> how do you create the GPSDO delay for B without a physical coax delay?

You are correct. In Randal's hp 5335A frequency counter experiment he was 
splitting a single GPSDO 10 MHz output to both the REF input and the chA input. 
As such, as you thought, no amount of GPS h/w or s/w delay would affect the 
phase difference between those two ports.

Bob:
> One “cute” thing to do when looking at GPSDO’s or GPS modules is to use the 
> “cable delay”
> setting. It will allow you to move the pps of one unit relative to the pps of 
> the other one.

Note the plural. What Bob is saying here applies to the case where you have two 
or more GPS timing receivers, or one GPS timing receiver and a local atomic 
clock. In these cases adjusting the s/w antenna delay is an easy way to adjust 
the phase of one of the signals.

I use this method when I want to introduce large delays, many us or ms. Most 
timing receivers offer a way to shift the phase of the 1PPS. For small delays 
it may not work like you expect. If it's a plain GPS/1PPS board there will be 
plenty of 1PPS jitter so changing the antenna delay by a few ns or few tens of 
ns may not be immediately visible. For a GPSDO it depends on how the firmware 
handles the antenna delay parameter. If it's a FLL-based GPSDO the antenna 
delay has no effect. If it's a PLL-based GPSDO the unit may go into holdover, 
or jam sync the 1PPS, and/or begin the slow process of slewing the output 
frequency to get the oscillator output to match the now-shifted GPS/1PPS output.

Does anyone have experience with binary programmable video delay boxes like 
http://www.allenavionics.com/V_Delay/var.htm which are found on eBay all the 
time?

/tvb


- Original Message - 
From: "Jerry" 
To: "'Discussion of precise time and frequency measurement'" 

Sent: Thursday, November 16, 2017 9:05 AM
Subject: Re: [time-nuts] Interpreting and Understanding Allen DeviationResults


Bob,

I am also a time newbie... how do you adjust this in software?  For time 
interval as discussed below, the unaltered GPSDO output goes to A and how do 
you create the GPSDO delay for B without a physical coax delay?  Any change in 
GPSDO cable delay setting will affect A and B the same.  Sorry if this is a 
stupid question

Jerry, NY2KW

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob kb8tq
Sent: Thursday, November 16, 2017 11:15 AM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] Interpreting and Understanding Allen Deviation Results

Hi

Yes, that’s exactly what I’m saying. You just use the software rather than 
dragging around a big hunk of coax. It makes it easy to get one pps into the 
“that’s way more than I need” range.
With the coax approach, is 50NS enough? Might 100NS be needed? Is there a 231NS 
case?.
I’ve spent a *lot* of time finding those cases in the middle of long data runs 
….

Bob

> On Nov 16, 2017, at 10:37 AM, Jerry  wrote:
> 
> Bob,
> 
> Do you mean then you do not need to put a physical long length of cable for 
> the delay, just do it in software or do you do both?
> 
> Jerry, NY2KW
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
> kb8tq
> Sent: Thursday, November 16, 2017 9:58 AM
> To: Discussion of precise time and frequency measurement 
> 
> Subject: Re: [time-nuts] Interpreting and Understanding Allen 
> Deviation Results
> 
> Hi
> 
> One “cute” thing to do when looking at GPSDO’s or GPS modules is to use the 
> “cable delay” setting. It will allow you to move the pps of one unit relative 
> to the pps of the other one. You then can be sure of which pps happens first. 
> That makes the A to B measurement much easier to analyze. 
> 
> Short intervals also can lessen the impact of the time base accuracy in the 
> counter ( you always are measuring a microsecond or so to a nanosecond 
> resolution). Indeed there are other issues (like jitter) that still are an 
> issue. 
> 
> Bob
> 
>> On Nov 16, 2017, at 4:10 AM, Azelio Boriani  wrote:
>> 
>> As already stated here, the best measurement mode is the 
>> time-interval mode. The 5335A is a 2ns single-shot resolution 
>> counter. Use the PPS output from the GPSDO, route it to the A (start) 
>> input and to a coaxial cable used as a delay line (10m, 50ns, should 
>> be enough). The other end of the cable into the B input (stop), 
>> select the time interval mode TIME A -> B. Let the internal reference 
>> clock the counter. Set trigger levels and the various parameter to 
>> get stable readings and collect your data.
>> 
>> On Thu, Nov 16, 2017 at 3:59 AM, Mike Garvey  wrote:
>>> Could you post some phase plots?  The data you show is not 1/tau and very 
>>> likely not white 

Re: [time-nuts] Jefferts & Campbell recent papers

[Tom Van Baak]

> These may be of interest, if the papers have not been circulated here before. 
> — Eric

Links to the cesium and optical clock papers that Eric just mentioned are:

1)
"Cesium Primary Frequency References"
by Steven R. Jefferts, Thomas P. Heavner, Elizabeth A. Donley
  http://tf.boulder.nist.gov/general/pdf/1924.pdf
also at:
  
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.527.4789=rep1=pdf

2)
"Ultracold atoms and precise time standards"
by Gretchen K. Campbell, William D. Phillips
  http://rsta.royalsocietypublishing.org/content/369/1953/4078
PDF:
  http://rsta.royalsocietypublishing.org/content/roypta/369/1953/4078.full.pdf

See also this powerpoint presentation by the same:

"Ultracold Atoms and Precise Time Standards"
by William D. Phillips and Gretchen Campbell
  https://www.bipm.org/utils/common/pdf/RoySoc/Bill_Phillips.pdf

--

And while we're at it, let me repeat these other papers mentioned recently.

3)
"A New Era for Atomic Clocks"
by Laura Ost
  https://phys.org/news/2014-02-era-atomic-clocks.html
  https://www.nist.gov/news-events/news/2014/02/new-era-atomic-clocks

4)
"When should we change the definition of the second?"
by Patrick Gill
  http://rsta.royalsocietypublishing.org/content/369/1953/4109.article-info
PDF at:
  http://rsta.royalsocietypublishing.org/content/roypta/369/1953/4109.full.pdf

5)
"Optical Atomic Clocks"
by Andrew D. Ludlow, Martin M. Boyd, Jun Ye, Ekkehard Peik, Piet O. Schmidt
  https://arxiv.org/abs/1407.3493
PDF at:
  https://arxiv.org/pdf/1407.3493.pdf

Exciting times.

/tvb


- Original Message - 
From: "Eric Scace" 
To: 
Sent: Tuesday, November 14, 2017 2:12 PM
Subject: [time-nuts] Jefferts & Campbell recent papers


These may be of interest, if the papers have not been circulated here before. — 
Eric


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Re: [time-nuts] Fwd: A talk on Atomic Clocks by Steve Jefferts NISTBoulder Wed 11/15

[Tom Van Baak]

Eric -- Thanks much for that posting.

List -- If you are interested in a summary of optical and lattice clocks, see:

"A New Era for Atomic Clocks"
https://phys.org/news/2014-02-era-atomic-clocks.html
https://www.nist.gov/news-events/news/2014/02/new-era-atomic-clocks

I also highly recommend this paper by Patrick Gill (NPL):

"When should we change the definition of the second?"
http://rsta.royalsocietypublishing.org/content/369/1953/4109.article-info
PDF at:
http://rsta.royalsocietypublishing.org/content/roypta/369/1953/4109.full.pdf

or this one by Andrew D. Ludlow, Martin M. Boyd, Jun Ye, Ekkehard Peik, Piet O. 
Schmidt:

"Optical Atomic Clocks"
https://arxiv.org/abs/1407.3493
PDF at:
https://arxiv.org/pdf/1407.3493.pdf

/tvb


- Original Message - 
From: "Eric Scace" 
To: "Discussion of precise time and frequency measurement" 
Sent: Saturday, November 11, 2017 7:50 AM
Subject: [time-nuts] Fwd: A talk on Atomic Clocks by Steve Jefferts NISTBoulder 
Wed 11/15

For time-nuts in the Washington/Baltimore area...

> 
> http://www.aps.org/units/maspg/
> November 2017 Event
> 
> Date: November 15, 2017
> Speaker: Steven R. Jefferts
> Topic: Primary Frequency References at NIST: Atomic Clocks
> Time and Location: 1:00 p.m., with Q to follow in a 1st floor conference 
> room at the American Center for Physics (www.acp.org ), 
> 1 Physics Ellipse, College Park, MD-- off River Rd., between Kenilworth Ave. 
> and Paint Branch Parkway.
> 
> Abstract: In the SI system of units a second is defined as 9,192,631,770 
> cycles (exactly) of the ground state hyperfine transition frequency of an 
> unperturbed cesium atom.  We take the atom to be at rest on the reference 
> geoid (~mean sea level) of the Earth.  Primary frequency standards (aka 
> atomic clocks) such as NIST-F1 & F2 in Boulder, Colorado attempt to realize 
> this definition with the highest possible fidelity.  Atomic clocks have 
> progressed steadily from fractional inaccuracies of df/f ~ 10-9 fifty years 
> ago to the best microwave clocks (NIST-F1) giving inaccuracies at the df / f  
> < 2 x 10-16  level, with optical clocks exhibiting even more phenomenal 
> performance at the 10-17 level and beyond.  This level of performance 
> requires an excruciating attention to detail when attempting to correct for 
> frequency biases.  For example, an uncertainty of 1 meter in the altitude of 
> the device with respect to the reference geoid causes a frequency uncertainty 
> of more than df / f  < 1 = 1
 0-16 while an uncertainty in the temperature of the radiation field to which 
the atom is exposed of 1K yields frequency shifts of several times this much.  
In this talk I will discuss some history of these devices, the current state of 
the art in laser-cooled microwave clocks and some fundamental limits to their 
attainable accuracy and briefly examine some of the current uses of this level 
of accuracy.  New and exciting laser-cooled microwave clocks for use in 
commercial applications and in space will also be examined.
> 
> Biography:  Steven Jefferts joined NIST, Boulder, Colorado in 1994 and since 
> 1998 has been designing, building and operating the NIST primary frequency 
> references.   Steve received a BS in physics from the University of 
> Washington in 1984, and a PhD in physics from JILA - University of Colorado 
> Boulder in 1992.  He served as an NRC postdoc under Dr. David Wineland 1992 - 
> 1994 and has been a member of the NIST Technical Staff in the Time and 
> Frequency Division since 1994.  He has won a Flemming Award, two Department 
> of Commerce Gold Medals, and a Condon Award.
> 
> 
>
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Re: [time-nuts] Favorite counters (current production)?

[Tom Van Baak]

Magus:
> Also, as being reported by the friends at Norwegian NMI, there is 
> something funky about. They got to borrow one from Ole Petter Rønningen.
> It was there in the York EFTF 2016 poster session, and I even made a few 
> folks aware of it as "interesting". If I had more time, it would be 
> interesting to dig deeper into that issue.

Way back in the time-nuts archives there are discussions now and then about 
some other low-level effects in these counters.

> A trouble with some of these modern counters is that sometimes their 
> processing isn't as transparent as it used to be. The trouble with that 

I agree 100%. They get "too clever" for their own good and the internal design 
is not released. This is one reason why the TAPR TICC is so welcome. Totally 
open h/w and s/w. Ok, it doesn't quite compete with 20 ps full-featured 
high-end counters, but it's also 10x cheaper.

That said, I want to point out that the latest GPSDO / counter from Stanford 
Research continues their tradition of relatively open design. If you have an 
hour, go through the very detailed user manual, which includes theory of 
operation and BOM and schematics, just like the old days:

http://www.thinksrs.com/downloads/PDFs/Manuals/FS740m.pdf
http://www.thinksrs.com/downloads/PDFs/Catalog/FS740c.pdf

It's rather understated: they call it a "GPS time and frequency system" but it 
does frequency synthesis and pulse generation, frequency counting and time 
tagging, stats including ADEV, etc. You can see how they combined pieces of 
several other products all into this one modern instrument. Perhaps there's no 
need for them to ever refresh the SR620 now that the FS740 exists.

> That said, I hope Keysight can straight it out. I'm not out to bash 
> them, but I'm not as excited about their products as I was back in the 
> HP and early Agilent days.

Right. That's also why I mentioned that if someday there's a Keysight B version 
of the 53230 I'm all in. Surely someone at Keysight is looking into this. They 
just need someone with a time nut mentality to clear up all the loose ends. 
Meanwhile the FS740 is on my Christmas list.

Scott:
> What current production freq counters do people like for general 
> time-nuttery these days? There's a chance I can get a decent counter 
> for work, so I'm looking for suggestions. Bonus points for fanless. 
> Don't need anything past 200 MHz or so. Prefer ethernet over USB or GPIB.
> 
> The SR620 looks to be pretty big and a little dated. The 53230A seems 
> to have better specs and screen than the Tek/Fluke FCA3k series. Am I 
> missing any?

So, Scott, give the FS740 a try. See if SRS will loan you one for a few weeks 
and report back to us on what you think.

Thanks,
/tvb

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Re: [time-nuts] Favorite counters (current production)?

[Tom Van Baak]

> Rank your preferences!

I echo Magnus. In almost every photo of national timing labs you will see 
SR620's in use. The interface, specs, readability, and reliability are really 
good. Also SRS seems to support their products forever. For the curious, the 
full BOM and schematics are in the service manual. Note they just added the 
FS740 (GPSDO) but there's no update for the 620 after all these years. The 
downside is that they are larger, heavier, and louder than many modern 
instruments.

For high-performance and high-throughput the CNT-91 is my choice. Quiet, 
feather-light, and it's a continuous dual-edge timestamping counter with raw 
data output capability.

That said, when I need a quick or long-term measurement I almost always grab a 
HP 53132A and run it in talk-only mode, collecting data with RS232->USB. Once 
you get used to the 5 key (arrows & enter) UI you're all set.

About the 53230 -- When it came out I got a pair on loan from Agilent; one with 
and one without OCXO. When I saw how badly they handled the external REF-in and 
how noisy the REF-out was, I figured it was a green team that designed it and 
I'd give them another product life cycle to learn about precision timing. So 
there are no 53230A in my lab. As soon as they come out with a redesigned B 
version where the ext/int REF are good to 1 ps (like you'd expect with a 12 
digit/s counter), I will be the first to buy one.

/tvb

- Original Message - 
From: "Magnus Danielson" 
To: 
Cc: 
Sent: Friday, November 10, 2017 11:50 AM
Subject: Re: [time-nuts] Favorite counters (current production)?


Hi,

I would say CNT-99/91 and SR-620.

Bob has a point about 53230, since the others is older, but on the other 
hand, it is a bit of a gamble. There are many aspects that goes into the 
longlivety of a product, such as access to components, but also strategy 
of companies.

The CNT-90/91 an 53230 both have graphical presentation, which is very 
beneficial. The SR-620 still have better performance even being older 
than everything else.

Cheers,
Magnus

On 11/10/2017 05:37 PM, Bob Camp wrote:
> Hi
> 
> There is no perfect answer. I’d go with the 53230 simply because it *might* 
> be supported
> the longest.
> 
> Bob
> 
>> On Nov 10, 2017, at 11:17 AM, Scott Newell  wrote:
>>
>> What current production freq counters do people like for general 
>> time-nuttery these days? There's a chance I can get a decent counter for 
>> work, so I'm looking for suggestions. Bonus points for fanless. Don't need 
>> anything past 200 MHz or so. Prefer ethernet over USB or GPIB.
>>
>> The SR620 looks to be pretty big and a little dated. The 53230A seems to 
>> have better specs and screen than the Tek/Fluke FCA3k series. Am I missing 
>> any?
>>
>> Rank your preferences!
>>
>> -- 
>> newell  N5TNL

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Re: [time-nuts] ublox NEO-M8T improved by insulated chamber?

[Tom Van Baak]

> How exactly do you measure offset of your GPS time output to absolute UTC 
> time?

Conceptually it's no different from measuring your favorite resister or 
thermometer: you compare your DUT against a standard REF and the difference is 
your error, a process called calibration. So the same is true for SI second 
(time interval, frequency) and UTC (time epoch). As I mentioned earlier, 
calibrating your SI second is quite simple. Calibrating your UTC is harder.

Here are couple examples:

(1) Years ago fellow time-nut Doug loaned out his and my antenna/receiver to be 
calibrated. The report will give you an idea of what's involved:

"Absolute Calibration of a Geodetic Time Transfer System"
http://xenon.colorado.edu/paperIrevise2.pdf


(2) Here's classic report from fellow time-nut Rick:

http://www.cnssys.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf
and
http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf


(3) In both cases above there is transport of equipment involved. But the 
equipment can come to you instead:

http://www.usno.navy.mil/USNO/time/twstt/calibration-services
see also
http://tycho.usno.navy.mil/twstt.html
and a nice photo of the traveling time van:
http://tycho.usno.navy.mil/gif/2waytruck.jpg


(4) NIST also offers time & frequency calibration services:

https://www.nist.gov/calibrations/calibration-areas/time-and-frequency

"A NIST Disciplined Oscillator: Delivering UTC(NIST) to the Calibration 
Laboratory"
https://www.nist.gov/sites/default/files/documents/calibrations/NCSLI.pdf

"Remote Time Calibrations via the NIST Time Measurement and Analysis Service"
https://www.nist.gov/sites/default/files/documents/calibrations/Remote-Time-Calibrations.pdf

That's enough reading to keep you busy for a few days.

/tvb

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Re: [time-nuts] UltrAtomic clock.

[Tom Van Baak]

> So, anyone notice what time their UltrAtomic clock did the dst change?
> 
> Mine didn't change last night. Time has been right since it first set itself, 
> so, I'm suspecting it's getting signal. ( We're in northern Michigan, eastern 
> time zone.)

Hi Dan,

One of the advantages of the UltrAtomic clock is that it makes use of the 
enhanced WWVB encoding format. That new format is specifically designed to 
solve DST / reception problems:

https://www.nist.gov/sites/default/files/documents/2017/05/09/NIST-Enhanced-WWVB-Broadcast-Format-1_01-2013-11-06.pdf

So your results are perplexing. When you say "time has been right since it 
first set itself" are you talking within minutes, or seconds, or fractions of a 
second? That would tell us if it has been receiving ok over the past week or 
month.

Also, can you check what your DST / Q-mode / Eco-mode switches are set to?

http://www.lacrossetechnology.com/media/catalog/product/4/0/404-1235ua-ss_manual_092316.pdf

Thanks,
/tvb

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Re: [time-nuts] HP 5335A Question

[Tom Van Baak]

> The designers very well designed two near inifinite counter chains inside the 
> 5335A..
> I got my wisdom from the hp journal 9-1980.

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1980-09.pdf


> They used a digital ASIC, called the MRC, multi-register counter, and it 
> allows counting
> of the input signal and the time base, each 20 decades long. (see page 26).

Just to be clear, the MRC itself has only 8 decades. You get additional decades 
with off-chip processing, which is to say, counting overflows. It's the same 
way we keep 64-bit time in a microcontroller: 16 bits of timer and then 48 more 
bits of overflow count.

"Another feature of the MRC lets its internal eight-decade
count chains be expanded to any number of decades with
the help of a processor. This feature is used to create a pair of
count chains, each 20 decades long. With a 100-MHz signal,
this chain would take more than 30,000 years to overflow.
Consequently, the 5335A has no overflow annunciator, so
gate times can be as short as 0 ns or as long as years."


There's more good info on the MRC starting on page 12 of an earlier HP journal:

"A High-Performance Bipolar LSI Counter Chip Using EFL and I2L circuits"
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1979-01.pdf


The heritage of the MRC shows up in my picPET (Precision Event Timer). Notice 
how hp's MRC also has an E-register (Event) and a T-register (Time). Once you 
have matched {event count, time stamp} pairs anything is possible. By 
"anything" I mean, totalizing, absolute time, time interval, frequency, period, 
mean frequency, period average, best fit frequency, sigma, sigma(tau), ADEV, 
etc.

BTW, if any hp old-timers reading this posting happen to have detailed 
information on the 40-year old proprietary MRC chip, please contact me off-list 
before it's too late. By too late I mean:

http://www.pressdemocrat.com/business/7559762-181/hewlett-packard-archives-at-keysight-destroyed

/tvb

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Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

[Tom Van Baak]

>> The DS3231 has an 8 bit register that will change its frequency in
>> increments of about 0.1ppm. Thus you could discipline it to get its pps
>> aligned with your reference.
> 
> That sounds like you just designed the worst GPSDO ever.

You could argue that the worst GPSDO ever is an operating system running NTP 
;-) A PC running NTP at +/- 10 us is a thousand times worse in time accuracy 
and a million times worse in frequency stability than a TBolt GPSDO.

But back to the DS3231. If the 0.1 ppm increment sounds too coarse to you, then 
just step between N-1 / N / N+1, similar to how PWM works. Don't laugh. Some 
microcontrollers also have programmable oscillator tuning and I tested this on 
a PIC -- microstepping 100 times a second -- as part of my "best worst GPSDO" 
project.

http://leapsecond.com/pic/src/pg41.asm

/tvb

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Re: [time-nuts] Distribution divider/amplifier for 10MHz GPSDO

[Tom Van Baak]

List -- Don is having email trouble, but here's his posting:

--

From: donaldbcol...@gmail.com
Date: Tue, Oct 24, 2017 at 1:38 AM
Subject:   Distribution divider/amplifier for 10MHz GPSDO

Hello group. I`m intending to distribute, via 50 Ohm coax, frequency
reference signals to my test equipment in my test bay [no relation to eBay,
except that most of the equipment came from there]. I`ll be using RG58/U
coax, and 50 ohm terminations, with the highest reasonable signal level
reticulated. Given that the name of the game seems to be to avoid any
severe reduction in SNR of the 10MHz signal comming out of the GPSDO, by
the logic dividers, and impedance lowering buffer amplifiers, what
considerations should be made regarding the choice of logic families, and
transistors to be used? The frequencies required by the test equipment vary
from 500kHz to 10MHz, and amplitudes from 100mV P-P sinewave, to 5V peak
squarewave. How good must the PSU be to stop the rot getting worse, and is
1/f noise in the active devices important? Your thoughts will be
appreciated.

P.S.: How accurate is the Trimble Thunderbolt for this
application?..Thankyou,Don
Collie.

--

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Re: [time-nuts] Sulzer 2.5 For Sale

[Tom Van Baak]

Hi Ruslan,

> this standard appears to be ancient 

Yes. Sulzer oscillators are among of the best quartz frequency standards ever 
made. Good reading:

"Brief History of the Development of Ultra-precise Oscillators for Ground and 
Space Applications"
https://ieee-uffc.org/about-us/history/uffc-s-history/brief-history-of-the-development-of-ultra-precise-oscillators-for-ground-and-space-applications/

"Design and Performance of Ultraprecise 2.5-mc Quartz Crystal Units. (Warner, 
A.W.)"

http://ieee-uffc.org/wp-content/uploads/2016/11/warner.pdf
https://ieee-uffc.org/about-us/history/uffc-s-history/

The Sulzer 2.5C and 5B oscillators are highly sought after by time-nuts, given 
the history, the space-era construction inside, and (if you're lucky, or need a 
project) the amazing e-13 level of performance out of these standards:

https://febo.com/pages/oscillators/sulzer/
http://leapsecond.com/museum/sul25-1/

You don't need to read Japanese to appreciate this wonderful set of teardown 
photos:

http://etoysbox.jp/1_TestEquipment/12_F_std/OCXO/OCXO.htm

/tvb

- Original Message - 
From: "Ruslan Nabioullin" 
To: "Discussion of precise time and frequency measurement" 
Sent: Sunday, October 22, 2017 12:55 PM
Subject: Re: [time-nuts] Sulzer 2.5 For Sale


That system clearly is a rudimentary (simply based on amplitude)
failover controller---e.g., a shoestring setup could have an EOL
cesium standard (relatively-accurate but -unreliable) that's not on
UPS and a UPS-backed OCXO (like this unit) (relatively-inaccurate but
-reliable) connected to ``REF IN'' and ``STBY IN'', resp.  Honestly
this standard appears to be ancient and the high-level build quality
appears to be questionable.

-Ruslan

On Sat, Oct 21, 2017 at 10:05 PM, Richard Mogford  wrote:
> Hello
>
> I am selling a Sulzer 2.5 frequency standard.It is rack mounted with a
> separate power supply and no battery.It also has an “Amplitude Fault
> System.”(I have not been able to find out what this does.) There is a PDF
> manual that I will send the buyer with the equipment.  The switch setting #4
> shows zero milliamps.
>
> I am not an expert in these devices by any means, but have been running the
> Sulzer for several days using John Miles’ excellent TimeLab software.I have
> pasted in below an Allen Deviation plot for three days of data collection.
>
> I will be selling the Sulzer on auction on eBay starting on Monday, October
> 23.The starting bid will be $200.Shipping may be around $50.
>
>
> Please contact me if you have any questions.
>
>
> Richard
> AE6XO
> rch...@earthlink.net
>


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Re: [time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

[Tom Van Baak]

> picPET -- Precision Event Timer http://www.leapsecond.com/pic/picpet.htm

Thanks for the plug. Yes -- it does sub-microsecond relative time-stamping 
simply: one Schmitt-trigger TTL input pin and one RS232 output pin. But -- it's 
a $1 chip, not a black box. And the timestamps aren't UTC either. So I think it 
misses some requirements that Rob mentioned.

Another alternative is to use UBX-TIM-TM2 messages from ublox timing receivers.

Still, as much as I like ublox or picPET or John's high-res Arduino-based TICC 
or homebrew NTP / Pi project, I suspect they are not the turn-key commercial / 
industrial black box that Rob is looking for.

/tvb

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Re: [time-nuts] current crop of GPS receivers for Rpi/Beaglebone forNTP server/etc

[Tom Van Baak]

Jim,

When I don't want to fuss with anything fancy I use these:

https://www.adafruit.com/product/746

https://www.parallax.com/product/28511
https://www.parallax.com/product/28509

https://www.sparkfun.com/products/12751

/tvb

- Original Message - 
From: "jimlux" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, October 16, 2017 6:45 AM
Subject: [time-nuts] current crop of GPS receivers for Rpi/Beaglebone forNTP 
server/etc


>I have beagles, but others have pis.
> 
> There seem to be dozens of GPS receivers out there in a variety of form 
> factors.
> 
> What's the current "best" inexpensive choice for run of the mill 
> time-setting/1pps  that's a "catalog" item
> 
> Plenty of online "how-to" from 2013 and 2014, but we here on the list 
> know that the "cheap GPS" receiver business is a very moving target - 4 
> years is a long time.


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Re: [time-nuts] Question about SA.33 Rb clock

[Tom Van Baak]

Hi Hui Zhang,

> in the paper CSAC was described that it is based on CPT technology
> My question is the SA.3x(or SA.2x) also used this method?

Yes. Here's another good read; and it also includes photos of the inside of 
your SA.33:

http://www-users.york.ac.uk/~jke1/Atomic_Clocks/Papers/Commercial%20CPT.pdf

> In my impression the SA.3x series clock is called Rubidium clock,
> and the SA.45 is a real Cesium CSAC?

Your use of the phrase "real cesium" may be the source of your confusion. The 
SA.3x uses rubidium and the SA.4x uses cesium. They are all real atoms. These 
modern MAC / CSAC atomic standards compete with high-end DOCXO quartz 
oscillators with respect to factors like temperature, stability, and drift. 
They do not compete with traditional laboratory rubidium or cesium standards.

You may be thinking that because some CPT clocks use cesium instead of rubidium 
that they are special or more accurate, but this is not the case. None of these 
compact low-power  laser / VCSEL / CPT -based frequency standards are primary 
standards.

/tvb

- Original Message - 
From: "Jar Sun via time-nuts" 
To: 
Sent: Saturday, October 07, 2017 8:27 PM
Subject: [time-nuts] Question about SA.33 Rb clock


Dear group: I have got a SA.33 Rb module from a second hand GPS clock, at first 
it works well, but soon after it was damaged that beacuse I was trying to 
install a heat sink on it, unfortunately I used screws which its size too long, 
so maybe the screws drilled into inside Rb lamp or inside circuit something? I 
don't know.
I am not expecting this Rb can be receoveyed, I am just hope there is no some 
martirial hamfully leaked out. TVB gave me some information about this Rb 
module and a papers on this website:
http://tycho.usno.navy.mil/ptti/2002papers/paper52.pdf
I have read the paper for two times, but I am confused now, the paper described 
a principle of CSAC clock in 2002, in the papger CSAC was described that it is 
based on CPT technology, and the CPT is based on a VCSEL and a very small 
Cesium Cell and other implement necessarily. My question is the SA.3x(or SA.2x) 
also used this method? In my impression the SA.3x series clock is called 
Rubidium clock, and the SA.45 is a real Cesium CSAC? So if SA.3x or SA.2x used 
the technique which mentioned in paper52, can we say there is some Cesium 
material in SA.3x? I am totally confused, do anyone can give me some advice? 
Any information will be appreciated, Thanks a lot.
Regards.
Hui Zhang
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Re: [time-nuts] NTP linked PC clock is slightly ahead of Lady Heather GPS time

[Tom Van Baak]

>> These days the speaker is almost the last usable interface for this.
>
> ….. and the mic input is one of the few inputs left to feed “events” into.

Yes, and by connecting the speaker to the mic and issuing a pulse through the 
speaker you can estimate the latency of the OS. It should act like an echo 
chamber and the number of echoes per second is your inverse latency.

The other trick is to use a TIC to compare the output pulse(s) against your 
house GPS/1PPS. You then compare the timestamp that the OS thought it was with 
the real UTC+TIC timestamp. Similarly, put a GPS/1PPS into the mic and compare 
the time the OS thinks it saw the pulse.

The results of these should give a nice pair of UTC offset and jitter plots. If 
at the same time you also measure the XO directly you can then subtract and 
pinpoint how much of the error is due to the XO and how much is due to OS 
design. For extra credit put NTP into the mix and see how badly NTP s/w 
performs compared to what a h/w solution could so.

/tvb

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Re: [time-nuts] Novatel Dual frequency GNSS receivers on ebay

[Tom Van Baak]

Christopher,

Thanks for that additional information. Can you (or Gregory) also comment on 
the external frequency input / output and the 1PPS output of this receiver?

A quick look at the om-2128.pdf and om-2129.pdf documents has words 
like "better than 250 ns accuracy" and "50 ns increments" but I didn't see 
mention of 1PPS quantization, sawtooth correction, or other words commonly used 
in GPS timing receiver specifications. I'm guessing this product is mostly 
designed for the PN part of PNT (Positioning, Navigation, Timing)?

/tvb

- Original Message - 
From: "Christopher Hoover" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, October 09, 2017 12:35 PM
Subject: Re: [time-nuts] Novatel Dual frequency GNSS receivers on ebay


>I have quite a bit of experience with Novatel hardware include OEM6, CPT
> and SPAN.
> 
> CPT is an IMU made by KVH and relabeled by Novatel.The accelerometers
> are MEMs and the roll rate sensors are FOGs.   Pretty old design.
> Performance is decent (but not auto alignment good).
> 
> http://www.kvh.com/Military-and-Government/Gyros-and-Inertial-Systems-and-Compasses/Gyros-and-IMUs-and-INS/IMUs/CG-5100.aspx
> 
> SPAN is the "solution."SPAN-CPT puts the CPT IMU and the receiver in a
> single box.   You could also get just the CPT in a box.
> 
> The feature set enabled depends on the software keys that are loaded.
> Caveat emptor.
> 
> Dual receiver (even if you have the hardware) and ALIGN feature are extra
> features.
> 
> Also worth noting is that the circular connectors used on some of the
> hardware are pricey.  Some are impossible to assemble without specialty
> tools.
> 
> -- Christopher.
> 73 de AI6KG
> 
> 
> On Sat, Oct 7, 2017 at 2:36 PM, J. L. Trantham  wrote:
> 
>> Any idea what they are selling for at this time?
>>
>> I see that some sold for the BIN price of $349.99 up until June 20.  After
>> that, 'Offer Accepted' occurred up through October 5, with a BIN price now
>> of $649.99, all plus $40 shipping.
>>
>> Joe
>>
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Gregory
>> Maxwell
>> Sent: Saturday, October 07, 2017 2:17 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] Novatel Dual frequency GNSS receivers on ebay
>>
>> There is an ebay listing for "Novatel GPS-702-GG with SPAN-CPT Single
>> Enclosure GNSS/INS Receiver + Cable" with a fairly large number available.
>>
>> This is a Novatel OEM628 dual frequency receiver (supports GPS, Glonass,
>> SBAS, apparently including L1C and L2C), plus a three fiber ring gyros
>> (with bias performance that blows away any mems gyro I've ever used) and an
>> 3-axis mems acceletrometer in an aluminum case, plus a decent dual
>> frequency antenna.  This is a generation-ish old kit.
>> The industrial casing conspires to make it look somewhat less modern than
>> it actually is.
>>
>> The receivers have external clock input (though not plumbed to the outside
>> of the case) which appears to work though I didn't try much with it yet.
>> Mine came with 2013-ish firmware but easily upgraded to current (2016)
>> firmware. There is a windows based firmware update tool which talks to it
>> over serial and is very straight forward (The firmware update OEM6631.zip
>> can be found via google).
>>
>> You can communicate with them over serial in ascii, there is extensive
>> firmware documentation that goes over every command
>> https://www.novatel.com/assets/Documents/Manuals/om-2129.pdf  some of
>> which are specific to other modules. There is also a separate manual for
>> the inertial navigation specific features (NovAtel SPAN-CPT Users
>> manual.pdf)
>>
>> The external clock should allow you to hang it off a more stable
>> oscillator which will improve the stability of the GNSS results, and _I
>> presume_ improve the quality of the PPS output-- the firmware manual and
>> operating manual are thin on details, and mostly just go into telling you
>> how to adjust the kalman filter constants for different clock types.
>>
>> These also appear to support the novatel 'align' mode where you serial
>> connect two receivers separated by a short baseline and get really accurate
>> absolute headings; I'm planning on trying that that but haven't set it up
>> yet.
>>
>> Looks like uber (last position was ubers offices in denver) had a fleet of
>> these things. The couple I got run great, including the IMU, the antennas
>> obviously spent a long time outside, but work fine. The cable they come
>> with is weird, but I had no problem chopping one end off and figuring out
>> the pinout (see bottom).
>>
>> The novatel OEM6 is well supported by rtklib and I was able to get
>> post-processed positions very easily.
>>
>> Seller takes best offers a fair amount below the $649 asking price.
>> Looks like they may have another 30 or so of them.
>>
>> May be useful 

Re: [time-nuts] Fw: Skytraq / GPS Almanac

[Tom Van Baak]

Status -- all is back to normal with GPS as of this morning. At least for now, 
the folks that run GPS appear to have reversed the change made last week that 
triggered latent bugs in some receivers. A note from Said just now:

> Hi Tom,
>
> Would you mind posting to Time nuts that this is a confirmed IODC MSB
> non-zero weird-but-legal-behavior/issue, and that this seems to have been
> corrected as of this morning?
>
> Notwithstanding that it seems the GPS system has fixed the "anomaly"
> this morning, we confirmed that the fix works (on live-sky signals last 
> evening)
> and are still implementing the fix here, and have received confirmation that
> Skytraq also fixed it moving forward.
>
> We have confirmed that other products in our library such as our Rockwell
> Collins and uBlox receivers did not find offense at the signal. I wonder how
> Trimble units faired?
>
> Thanks,
> Said

Trimble, Motorola, ublox, everyone was fine -- except for Skytraq, as far as I 
know.

Thanks again to Jay Grizzard for making this a quick & fun anomaly to observe. 
I'd like to imagine Said's quick posting to time-nuts and Jay's dramatic plots 
helped in some way to bring attention and resolution.

https://www.febo.com/pipermail/time-nuts/2017-September/107050.html
https://www.febo.com/pipermail/time-nuts/2017-September/107051.html

/tvb

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[time-nuts] Fw: Skytraq / GPS Almanac

[Tom Van Baak]

An interesting note from Said, below...
I've sent a couple of queries out to GPS professionals.
Feel free to comment if you have concrete information that would help.
Also, if during the past week any of you were logging almanacs or continuously 
recording the 50 bps raw data from any GPS/SV, please let me know.

Thanks,
/tvb

From: "Said Jackson" 
Sent: Tuesday, September 26, 2017 12:07 PM


> Tom,
> 
> Not sure if you have heard of the recent changes to the GPS Almanac causing
> issues with the Skytraq receivers. This has apparently happened around 9/20.
> We have received word from Skytraq that units operating in ROM mode (3D
> Mobile mode) are affected, but not units using the Position Hold/Auto Survey
> Flash mode, and units that are presently running will continue to run well.
> Units operating in 3D Mobile mode that are reset or power-cycled will not be
> able to achieve a GPS Fix. This is a now verified bug in the Skytraq ROM
> firmware.
> 
> Just to re-iterate the above: units operated in Auto Survey - Position Hold
> mode are not affected at all by this.
> 
> We are working on a patch for this for users that need to run the units in
> 3D Mobile mode, and hope to have one in the next few days. This patch will
> have to be applied here at JLT, so units will have to be returned here once
> the patch is available.
> 
> In the meantime units that are powered-on and operating properly should be
> left powered-on, or switched to Position Hold mode (but the switch must be
> made while power is removed from the board!)
> 
> This is very unfortunate, and we are very sorry for the inconvenience this
> might be causing users. Apparently this is likely affecting all ROM-operated
> Skytraq receivers. Not good.
> 
> In parallel we are also trying to reach the GPSOC to determine why the
> parameter switch was done, and if they can please revert back to the old
> setting which apparently had been used for decades until last week.
> 
> Please let me know if you have heard additional reports or info, and please
> feel free to post the above info on Time Nuts.
> 
> Bye,
> Said


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Re: [time-nuts] Bad TBolt Crashing LH?

[Tom Van Baak]

Everyone...

We're going to take this issue off-list for a while. Mark (LH author) and 
others will work this out with Jerry by email and report back when all is known.

Thanks,
/tvb
Moderator, http://leapsecond.com/time-nuts.htm


- Original Message - 
From: "Jerry" 
To: "'Discussion of precise time and frequency measurement'" 

Sent: Wednesday, August 30, 2017 12:03 PM
Subject: Re: [time-nuts] Bad TBolt Crashing LH?


My problem isn’t subtle... I get a Windows 7  popup that LH stopped working.  
When I look at the last log entries, there is marked corruption so ROM, OSC, 
POW are all major critical errors listed as bad.  I have both PC's running now 
so will let them run at least until something crashes.  Now both running 
fine... isn’t that the way bugs work?

Jerry, NY2KW

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob kb8tq
Sent: Wednesday, August 30, 2017 1:43 PM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] Bad TBolt Crashing LH?

Hi

I’d just set up your favorite terminal program (PUTTY or whatever ) on the 
second PC and let it do a log file to disk. Then go back and look at the 
“problem time”. If all of a sudden the lines are half as long or twice as long 
as they should be …. you found the problem. The kind of stuff that a defective 
serial port does is rarely subtle ….

Bob

> On Aug 30, 2017, at 12:26 PM, Jerry  wrote:
> 
> Hi Bob,
> 
> I have a Y 9pin serial splitter somewhere.   When you say log do you mean 
> using LH to write a raw file on both PC's simultaneously?  Is serial comm 
> between LH and PC all receive only - no handshaking that would get messed up 
> with a split Y serial cable?
> 
> Jerry, NY2KW
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
> kb8tq
> Sent: Wednesday, August 30, 2017 11:20 AM
> To: Discussion of precise time and frequency measurement 
> 
> Subject: Re: [time-nuts] Bad TBolt Crashing LH?
> 
> Hi
> 
> If you have a second PC, there’s a real quick shortcut. 
> 
> Make up a Y cable and log the output of the TBolt on the second machine. If 
> the TBolt really *is* sending junk, you’ll see it. If not, the TBolt is ok. 
> Swap the machine that is logging, if the same thing is still true, it’s not 
> the TBolt and it’s not the serial “stuff”. 
> 
> Bob
> 
>> On Aug 30, 2017, at 8:52 AM, Jerry Stern  wrote:
>> 
>> Thanks Ken,  yea that was fun until i read aboit disabling it. 
>> Unfortunately not the problem.  I swapped PC's and still happening so 
>> i am ledt with power supply, usb-serial adapter or Tbolt problems.  
>> In process of elimination now
>> 
>> Jerry
>> 
>> Sent from my iPhone
>> 
>>> On Aug 30, 2017, at 6:35 AM, Ken Winterling  wrote:
>>> 
>>> You also want to disable the "Microsoft Serial BallPoint" mouse in 
>>> Windows Device Manager.  If left enabled it causes your mouse 
>>> pointer to jump all over the screen every time the TBOLT sends data 
>>> to the computer; about once/second.  That was "fun" the first time I 
>>> encountered it.  It looks like your PC has been infected with a virus.
>>> 
>>> Ken
>>> WA2LBI
>>> 
>>> 
>>> 
>>> 
>>> On Wed, Aug 30, 2017 at 4:28 AM, Stephen Tompsett 
>>> 
>>> wrote:
>>> 
 For FTDI serial ports, in addition to ensuring that USB suspend is 
 disabled in advanced power properties, it's worth disabling Serial 
 Port Enumeration in the advanced properties for the com port. This 
 will help prevent FTDI ports with data being gratuitously sent to 
 them from being assumed to be a mouse or pointing device; 
 Unfortunately this setting gets reset following most significant 
 Windows updates, so you get used to clearing the setting every couple of 
 months...
 
 
> On 29/08/2017 19:28, Jerry wrote:
> Thanks to all. I am using a high end laptop running Windows 7 Pro, 
> power
 settings are all max'ed for performance - no sleep modes.  I 
 thought it had a direct DB-9 serial but it does not so have to use 
 an adapter.  I have 3 different manufacturers USB-Serial but all 
 use Prolific which I heard has counterfeits and driver problems.  I 
 just ordered an FTDI type recommended for my Flex radio.  Fingers crossed 
 not the TBolt.
> 
> 73
> Jerry, NY2KW
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Ken
 Winterling
> Sent: Tuesday, August 29, 2017 12:52 PM
> To: Discussion of precise time and frequency measurement <
 time-nuts@febo.com>
> Subject: Re: [time-nuts] Bad TBolt Crashing LH?
> 
> Jerry,
> 
> I agree, if you have a "real" RS-232 port available use it to 
> check if
 the TBOLT and LH communicate.  If that works, 

Re: [time-nuts] Ships fooled in GPS spoofing attack suggest Russiancyberweapon

[Tom Van Baak]

Please remember this is time nuts. This thread is straying far from timing and 
also becoming speculative instead of informative.

/tvb


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Re: [time-nuts] Trimble Thunderbolt no longer determines the correct date

[Tom Van Baak]

> The E911 installation, in the news, is just one of several. Others are 
> hospitals,
> fire stations, etc. using different dispatch systems.

Hey, at least important things like mobile phones, ISP's, Google, Amazon, FedEx 
and Starbucks aren't affected ;-)

> In a wide-area simulcast-overlap paging system, the transmitters in the same
> coverage area are carefully set to all transmit at exactly the same time.

That's fine. And very clever. But why is this "life safety" system tied to GPS, 
to a particular vendor, to a particular model of receiver (that clearly states 
in the documentation that it has a 1024 week / 19.6 year window of valid UTC 
times)?

> So to me "synchronizing transmitters” means the control system sends the
> traffic out to all the transmitters (over satellite) and tells them all to 
> hold the
> messages in a buffer until “the big hand points straight up” or whatever data
> command the system uses. (excuse the vernacular) 

Exactly. In most of the precise timing world the "big hand" is the "top of the 
second", or the so-called 1 PPS pulse. The idea is that all 1PPS agree with 
each other, whether from a cesium clock, or WWVB receiver, or NTP, or GPS (or 
any other GNSS system).

Since the paging system failed it sounds like it was synchronized to some 
"hand" other than 1PPS. The rare GPS rollover events tend not to disrupt the 
1PPS output -- it is still perfectly aligned with UTC -- which is why almost no 
one else worries about the recent TBolt episode, or any other GPS receiver for 
that matter.

> The problems being experienced right now appear to be the interface of the 
> ThunderBolt
> with the Zetron Model 620 simulcast controller over TSIP. The Zetron box is 
> also called
> a “wireless data encoder.”

Ah, ok. So do you or anyone have contact within Zetron? The easy fix would be 
for them to upgrade their firmware and send out a patch. Probably cheaper than 
supplying new receivers from Trimble. I don't know; for us, a s/w fix is easy 
compared to a h/w fix or a h/w swap-out. But in the real world, once 
technicians have driven to a remote installation, maybe there's no real 
difference between a s/w fix and a h/w swap.

> It is not our goal to blame a particular piece of equipment for this problem.

Right, no need to blame. I think many of us would just want to pinpoint the 
root cause of the problem, out of engineering curiosity. By root cause I mean 
actual schematics or lines of source code. It's always been my hope, after 
every one of these widespread infrastructure events, that the actual source 
code or design decisions be published eventually so that we can all learn from 
it.

> The facts are the 1024 roll over happened and just about nobody in the paging
> business knew it was coming.

Ok, now you know about GPS rollovers! Fun, isn't it? Leap seconds are fun too.

When the dust settles, you may want to look into the more general topic of life 
safety infrastructure vs. free-from-the-sky time & frequency. These days 
nanosecond precise time is cheaper than water -- but it's also fragile. A lot 
has been written about this. It's both a wake-up call for naive vendors of 
products based on GPS alone and also an opportunity for vendors who know how to 
design and market resilient timing products.

/tvb

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Re: [time-nuts] Trimble Thunderbolt no longer determines the correct date

[Tom Van Baak]

Brad,

Strictly speaking, there's no problem with GPS, or Trimble, or the Thunderbolt 
GPSDO: each did exactly as designed and documented. Anyone working with timing 
systems (from astronomy to calendars to watch making to operating systems) 
knows there are many subtle details. Just wait until 2038 for MOAR (the unix 
Mother of all Rollovers)!

Each GPS receiver manufacturer deals with dates and times and rollovers 
differently. Still, it sounds like the 3rd party who wrote software for the 
E911 or paging system forgot to read the manual on the GPS receiver they chose.

> The Trimble Thunderbolts are used in many Radio Paging Systems to
> synchronize their transmitters in simulcast mode.
> Systems that are using the models affected by the 1024 week epoch
> are currently off the air or functioning poorly.

If you are able, can you explain to us what exactly in the transmitters is the 
problem? All of our TBolts continue to give valid 1 PPS and 10 MHz outputs. 
What exactly do you mean by "synchronizing transmitters"?

> Trimble's only distributor, Novotech, did not know about it and had no
> inventory of the new replacement E series Thunderbolt GPS Receivers.
> Trimble says they are shipping new units from their overseas factory in
> about 2 weeks -- that's the best they can offer!

Is there no way for E911 people to manually set the clock on their system?

> I read here on the Time Nuts messages that some are considering: "some in-line
> device that re-writes the serial data as it comes out of the Thunderbolt

Right, that was an idea I mentioned. Easy to do but I don't think anyone 
bothered, because:

1) Mark had already fixed Heather.exe for his users, some NTP people added code 
to their TBolt drivers, Didier updated his LCD Monitor board -- these are all 
solutions that keep the same TBolt and just tweak the interpretation of the 
received TSIP date. Hence no need to update the TBolt or create an inline 
date-fixer gizmo.

2) Almost all of us use TBolts for their precise time & frequency outputs, not 
their TSIP packets, so rollovers don't matter.

> Does anyone plan to do this? Or does anyone have any ideas for a short-term 
> solution.
> Any suggestions would be sincerely appreciated.

Presumably the E911 system runs some kind of software or operating system? 
Surely there's a way to have the guys who wrote the s/w put a fix in? That 
should be much faster and cheaper than waiting 2 weeks for new h/w, no?

Bob,

> Next up is the comment that it took two weeks and $27,000 to fix.

Wow! At that price, I bet quite a few time-nuts will have a R-Pi or Arduino or 
PIC solution ready by the weekend. Me, I'm busy with family and eclipse and so 
will have to pass on the offer.

You'll want to continuously read serial, unpack TSIP (the DLE stuff), fix the 
0x8F-AB message, repack into TSIP and serial output. You may even get away with 
a single UART since the Rx/Tx pins are both 9600 baud and full duplex. The 
0x8F-AB date fix involves converting UTC ymd to #days, adding 1024, converting 
#days to UTC ymd, where #days is any linear day counting system that works from 
1980 to 2100. Both Mark and I posted samples a while ago. It may take some work 
to make the inline translator code asynchronous enough to avoid data loss or 
excessive packet latency, though. And it's impossible to do real-time 
byte-for-byte translation because the DLE escapes in TSIP can slightly alter 
the byte count.

Adrian,

> While it wouldn't be difficult to build such a device, manufacturing a decent
> quantity in less than 2 weeks to beat Trimble would be a tall order.

Agreed. You know as there's a customer, a weekend project can easily turn into 
a 2 week project.

/tvb

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Re: [time-nuts] interesting HP divider and clock on ebay

[Tom Van Baak]

> If the 115 has no motor (and I'm not questioning you, Bill) what moves the
> "digital" numbers? It looks like a clock drive, and the 1968 HP catalog
> makes reference to an "additional drum," which also sounds like a motor
> drive.
> 
> Jeremy

The 115 does have a motor; the digital readout works like an odometer.
Here's four of many photos of a 115BR and 115CR:

exterior:
http://www.dvq.com/oldcomp/hp/large/hp_115br_1.JPG
http://www.dvq.com/oldcomp/hp/large/hp115cr_1.JPG

interior:
http://www.dvq.com/oldcomp/hp/large/hp_115br_2.JPG
http://www.dvq.com/oldcomp/hp/large/hp_115br_5.JPG
http://www.dvq.com/oldcomp/hp/large/hp115cr_4.JPG

The last photo (hp115cr_4.JPG) is particularly nice.

Note also the NNN.NNN millisecond advance/retard feature. This is done with an 
analog phase resolver and digital turn counter.

/tvb
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Re: [time-nuts] interesting HP divider and clock on ebay

[Tom Van Baak]

> Boy I have to say the front looks great. Good pixs to look at.
> Price not exciting at all. But maybe someone has a spare kilo-buck.

Paul,

More info on the hp 115:

http://hpmemoryproject.org/wb_pages/wall_b_page_01.htm

/tvb
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Re: [time-nuts] SOPHOS discussion of GPS jamming and eLoran

[Tom Van Baak]

> My apologies for the long link.

Try this instead:

https://nakedsecurity.sophos.com/2017/08/07/cyberattacks-on-gps-leave-ships-sailing-in-dangerous-waters

Often when you see a long URL, or one full of strange numbers, it's encoded or 
encrypted personal tracking information. In this and many cases it's safe to 
delete everything that's part of the utm_source= keyword [1] and try again 
before you cut/paste the URL into a posting for time-nuts. Not only does it 
make the URL short and readable, but it also prevents your personal tracking 
information from being leaked to the mailing list and permanently to the web.

/tvb

[1] https://en.wikipedia.org/wiki/UTM_parameters


- Original Message - 
From: "Bill Hawkins" 
To: "'Discussion of precise time and frequency measurement'" 

Sent: Monday, August 07, 2017 10:48 PM
Subject: [time-nuts] SOPHOS discussion of GPS jamming and eLoran


> SOPHOS is a European anti-malware company that publishes a daily
> newsletter of oddities in the security world.
> This article on jamming of S Korean GPS by N Korea may be of some
> interest.
> 
> https://nakedsecurity.sophos.com/2017/08/07/cyberattacks-on-gps-leave-sh
> ips-sailing-in-dangerous-waters/?utm_source=Naked+Security+-+Sophos+List
> _campaign=f2c7691392-naked%252Bsecurity_medium=email_term=0_
> 31623bb782-f2c7691392-455148921
> 
> My apologies for the long link. You could try Googling the subject if
> the link is broken up by your mailer.
> 
> Bill Hawkins
> 
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Re: [time-nuts] Fwd: [hpsdr] SDR experiment for the solar eclipse

[Tom Van Baak]

> We were originally going to put a 5071A-locked beacon on three ham 
> bands, but decided WWV and CHU would be better sources, and logistics 
> were turning into a problem: I'm going to be doing my wideband recording 
> from a cottage in northern Michigan.  But I'm still a time-nut, so the 
> receiver will be GPSDO-controlled, and there will be a stratum 1 NTP 
> server in the cottage to provide timestamps. :-)
> 
> John

Hi John,

My favorite write-up about atomic clocks and eclipses (a null result) is at:

http://www2.mpq.mpg.de/~haensch/oldStuff/eclipse/eclipse.html

There you will find a good summary, thorough methodology, and many plots for 
the 1999 eclipse. Plus they posted all the raw data (H-maser, cesium, 
rubidium), a time-nuts dream. There is no model for why an eclipse should 
affect time at the atomic (quantum) level so a null result is fine. If nothing 
else, it sets an upper bound on measurement precision or a lower bound on clock 
anomalies, if they exist.

Much more dramatic is what an eclipse might do to the ionosphere, as this may 
affect both GPS and HF radio. So I'm very please to see the ham community 
milking this rare opportunity for all it's worth.

/tvb

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