Re: [time-nuts] Tektronix FCA3103 ADEV measurement tau setting problem

[Tom Knox]

Actually the CNT-91 and FCA31-3 are the same, the 300 and 400MHz are just 
claims, both are not very useful above 300MHz but de-rated can measure 400MHz.

Cheers;

Thomas Knox


From: time-nuts  on behalf of Björn 

Sent: Tuesday, May 29, 2018 2:03 PM
To: gandal...@aol.com; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Tektronix FCA3103 ADEV measurement tau setting problem

If this is a badged CNT-91...

This is from the current spec.

”The CNT-91 features a frequency range of 0.001Hz to 400 MHz standard with 
options to 3, 8, 14 and 20 GHz. ”

The counter was designed while Pendulum still did R in Stockholm - not very 
far from Magnus domains. Magnus certainly knows how to do proper ADEV with that 
counter.

—

 Björn

Sent from my iPhone

> On 29 May 2018, at 20:58, gandalfg8--- via time-nuts  
> wrote:
>
>
> I have a Tek FCA3103 300 MHz counter that measures ADEV
>
> as a built in function.  When I bring up the settings
> menu for the measurement, it has an entry window for
> "tau" (the averaging time, IE "sigma sub y of tau").
> It defaults to 200 ms.  I can enter larger values and
> ADEV gives reasonably results.  However, if I enter
> smaller values, even 199 ms, I don't get any error
> on the display, but I get clearly erroneous
> results for ADEV. I read the manual and cannot find
> anything to the effect that the instrument doesn't work
> for less than 200 ms.
>
> BTW, I asked Tek "customer no support" about it and
> they were clueless.
> ---
>
>
>
> Hi Rick,
>
>
> The Tek FCA3100 is a rebadged Pendulum CNT91 and Pendulum became part of 
> Spectracom.
> Unless I'm missing something, the FCA3103 is the FCA3100 with 3GHz input C 
> fitted.
>
>
> I've also found that Tektronix tech support seemed to know very little about 
> these but, in the past anyway, found Spectracom in the UK to be very helpful. 
> I'm not sure about the current status as Spectracom now seems to redirect to 
> Pendulum as a separate company again.
>
>
>
> Unfortunately, I can't help with your enquiry, and am also somewhat confused, 
> as I don't recall seeing a settings entry window for "tau" as a settings 
> option for the built in ADEV function. I take it you do mean the built in 
> option as in displaying results on the built in screen, or are you also using 
> some external software?
>
>
> If you are just usin the built in display I'd be interested to hear what 
> firmware version your FCA3103 is showing in the "About" screen
>
>
>
> My FCA3100 is showing the firmware version as 1.28s of 25 Aug 2010, which 
> seems to match the latest available Tektronix download but I'm wondering now 
> if there are unlisted updates.
>
>
>
> Nigel, GM8PZR
>
>
>
>
>
>
>
>
>
>
>
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[time-nuts] Some comments on GPS timing

[Tom Clark]

Perhaps it is time that I step in to point the newer members of 
Time-Nuts to some of the historical (hysterical?) info on using  GPS to 
achieve sub-microsecond global timing sync. I refer you all to the 
website http://gpstime.com   that Rick Hambly (http://cnssys.com) 
maintains to document some of our timing exploits over the past ~25 
years starting with the early Motorola PVT-6 "SIXPACK" and proceeding 
thru the later ONCORE, M12 and UBLOX  receivers.


By explanation, I was one of the principal researchers that developed 
the technique of Very Long Baseline Interferometry (VLBI) for high 
accuracy Geodesy and Astrometry. In VLBI we record raw noise from a wide 
RF bandwidth at a network of radio telescopes around the world. Most of 
the noise picked up at the stations is from the microwave receivers, the 
earth's atmosphere & the 2.7 degree  remnant background noise from the 
big bang -- the system noise resulting from all these sources at each 
station is independent and uncorrelated with noise at all the other 
telescopes.


But a small fraction of the noise originated at quasars which are 
(nearly) point sources with an angular sizes measured in fractions of 
milliseconds of arc (1 milliarcsec is about the size of George's head on 
a quarter held over over San Francisco as seen from Boston); the noise 
from these compact sources is correlated at the stations separated 
thousands of km and serve as reference points for the celestial 
reference frame. The telescopes define fixed points on the earth which 
constitute the terrestrial reference frame.


To extract the correlated signal VLBI each station uses an independent 
Hydrogen Maser clock as a time and frequency reference. The independent 
clocks need to be synchronized at nsec levels and to hold this 
synchronization for time scales up to several days. I realized that, if 
each station used a GPS-based timing system operating 24/7/365, we could 
solve the time/frequency sync needed to measure the "real-time" motions 
of the earth as the continents drift and the rotation of the earth and 
the sub-milliarcsec astrometric position and structure of the quasars.


FYI -- After 3+ decades of such measurements, we now know the few cm/yr 
(about the same speed as your fingernails grow) of relative motions of 
the continents (a.k.a. "continental drift") to uncertainties of tens of 
microns/yr. The celestial reference frame as defined by the  positions 
~1000 extragalactic radio sources is known to ~10 microarcseconds. You 
can see get a feeling for these results and the network of stations that 
produced them by browsing http://ivscc.gsfc.nasa.gov .


As you browse the material on http://gpstime.com you will see snapshots 
of our efforts at delivering low-cost GPS timing system intended for the 
VLBI station operators ("telescope drivers") updated every couple of 
years. Also you will find presentations we gave at several Precise Time 
and Time Interval (PTTI) meetings.


To answer a couple of the recent questions in more detail, take a look 
at the 2006 "Low Cost" PTTI paper :


1. For all the ONCORE and UBLOX receivers: The "sawtooth correction" is
   in the binary data message for the NEXT second. The receivers have
   an counter register that is updated based on the navigation firmware
   (typically a Kalman filter) to the integer number of clock counts
   corresponding to the next 1 PPS epoch. The sawtooth correction is
   the fractional part of the epoch that is left over after the integer
   clock count is set into the hardware.
2. In Rick's CNSCLOCK, a programmable delay line is fed from the
   fractional counter error (the "sawtooth correction" plus a small
   constant "DC" to center the correction in the delay line). The "DC"
   bias is treated as if it were a cable length correction.
3. My email address has changed from verizon.net: Now it is
   mailto:tom.k...@gmail.com

73 de Tom K3IO



---
This email has been checked for viruses by Avast antivirus software.
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[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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[time-nuts] Still looking for a maual for an Auston 2110 Disciplined Frequency Standard

[Tom Leedy via time-nuts]

Hi:
 
If anyone has a manual for an Austron 2110 Disciplined Frequency Standard, I 
would be interested in a copy.  Please feel free to contact me off-list.  This 
is a really cool instrument that locks the frequency of its internal ovenized 
crystal oscillator to an external standard having superior long-term stability. 
 
 
Many thanks
 
Tom Leedy
Clarksburg, MD 20871
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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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[time-nuts] Introduction & GPSDO Question

[Tom Koza]

Hello Everyone,

My name is Tom and my amateur callsign is WB6FYR, I'm a newcomer to this
group.

I'm mainly interested in creating a reasonable 10mHz standard for my
various pieces of test equipment here at home.  To that end I've purchased
and received an Ebay "Trimble Inside" GPSDO unit, described as model
57963.  No instructions or manual were included with the hardware.

The unit has now been powered up for the past 18 hours with the GPS antenna
connected with a favorable outside view of the southern sky.  I am however
uncertain if the hardware is GPS locked based on the two external ACT
status LEDs, the leftmost LED is solid yellow and the adjacent right LED is
rapidly flashing red.  The 1pps LED is flashing once per second as expected.

Can anyone point me to an online manual or explain the ACT status LEDs and
how to interpret those indications.

Thanks very much!
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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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[time-nuts] Looking for IEEE-488 codes and formats for Datum 9700AT Programmable Time System

[Tom Leedy via time-nuts]

Hi:
 
I am looking for the IEEE-488 codes and formats for a Datum 9700AT Programmable 
Time System.  The 9700AT is a 1U time generator and translator with slots in 
the back that can accept option cards with various functionalities such as -488 
and RS-232 interfaces, GPIO, and tape searches.  What I need is the character 
strings to output the time for the -488 interface.  The manual for the unit is 
here: 
http://www1.symmetricom.com/media/files/support/ttm/product-manual/man-9700at-9710.pdf
However, it is silent on the details of the -488 interface.
 
Any help would be appreciated and feel free to contact me offline.
 
Many thanks!
 
Tom Leedy
Clarksburg, MD
 
 
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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] New GNSS chipsets

[Tom Knox]

Hi All;

I think the real break through is using these different constellations and 
their different frequencies and looking at carrier phase verses timing 
elements. This should allow the removal of propagation delay.

Cheers;

Thomas Knox
act...@hotmail.com



From: time-nuts  on behalf of Magnus Danielson 

Sent: Sunday, April 1, 2018 2:40 PM
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] New GNSS chipsets

Joe,

I'm not sure I had much influence, but I at least try to advocate for it
to become a good market, so hopefully it will be affordable. It has
actually been affordable for quite some time, so going multifrequency
should be the next step and with that the benefits.

Cheers,
Magnus

On 04/01/2018 07:04 PM, Joseph Gray wrote:
> Magnus,
>
> When I can buy one of these new, multi-frequency receivers, I'll remember
> to thank you :-) I wonder if any of the three will be available this year.
> The Broadcom chipset in phones will be nice, but I'd also like a standalone
> module from anyone. More fun stuff to play with.
>
> Joe Gray
> W5JG
>
>
> On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson > wrote:
>
>> Hi Joe,
>>
>> On 03/31/2018 01:16 PM, Joseph Gray wrote:
>>> I've been reading announcements by Broadcom, uBlox and ST Micro for new
>>> chipsets that will use L1, L2, L5 to provide significantly more precise
>>> positioning for every day applications like cell phone, autonomous
>>> vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says
>> "centimeter
>>> level". The next few years ought to be very interesting, as these
>> chipsets
>>> become available in consumer products.
>>
>> I have advocated for receivers able to handle multiple frequencies and
>> multiple GNSS for some time, sneaking it into documents, so there should
>> be some preparations for this now.
>>
>> The benefit is naturally redundancy, but also higher precision.
>>
>> Natural I would enjoy cheap multi-frequency receivers myself, but I
>> would never admit that this would be a reason for advocating it. ;-)
>>
>> Cheers,
>> Magnus
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>>
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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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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Tom Miller]

- Original Message - 
From: "John Ackermann N8UR" 
To: "Discussion of precise time and frequency measurement" 


Sent: Sunday, March 18, 2018 4:13 PM
Subject: [time-nuts] ULN regulator with more current capability than LT3042?


Reviving the conversation about superb voltage regulators, I am looking 
for one to run the analog and PLL bits of a high performance frequency 
synthesizer chip.


The current drain looks to be about 160-180 mA at 1.8 V, which is 
uncomfortably close to the limit for the LT3042 (200 mA).  The 
manufacturer's evaluation board uses a MAX8869, which appears to be 
nowhere in the LT3042's league, but will source 1 A.


Any recommendations for a 1.8 V regulator a little beefier than the 
LT3042, but with similar noise performance?


Thanks!
John
___


Run two in parallel for twice the current and less noise?

Regards 


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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] Z3801A OCXO manual trimming

[Tom Curlee]

What is the rail to rail EFC voltage on the Z3801A?  Is it different than the 
single oven 10811?  My 10811 manual says that the EFC is -5V to +5V, while the 
EFC voltage on my ailing Z3801 is ~-2.0V with LH reporting the DAC at 
99.996902%.
Haven't had time to dig any further - been moving/installing antennas including 
one of my GPS antennas.


  From: Mark Sims 
 To: "time-nuts@febo.com"  
 Sent: Monday, March 5, 2018 7:36 PM
 Subject: [time-nuts] Z3801A OCXO manual trimming
   
Or, it you are sure it's the OCXO,  go shopping for a new one.    There is a 
reputable seller with them (the double oven version) for $100 on Ebay.

A couple of things to try...  monitor the EFC voltage, power up the unit, and 
see if it is changing as it attempts to lock.  If  it does not, you may have a 
DAC problem... I don't think the Z3801 remembers the last DAC voltage to speed 
up the initial lock, so it should be searching for the lock voltage.

Also monitor the OCXO output and see how it changes as it warms up.  It should 
start out several Hz off and converge to 10 MHz as it warms up.  



> Either tear into the OCXO or go shopping for a new(er) GPSDO.
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[time-nuts] Has anyone played with a SRS FS740?

[Tom Knox]

Hi All;

Has anyone had hands on experience with a FS740 or any thoughts in general? 
Seem like a really nice box.

Thanks;

Thomas Knox

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Re: [time-nuts] Need a Watch Recommendation

[Tom Knox]

I think what makes the IWatch unique is it has an option that makes it a 
standalone cell phone. With this new option it no longer need to be in 
proximity of you IPhone. You leave the IPhone at home and have a fully function 
cell phone on your wrist. The only hitch is they will not let you active a 
watch separately, it must be tied to you IPhone number.

Garmin also make some nice sport watches that a fully functional GPS receivers. 
Everything but a one PPS and 10MHz output.

Cheers;

Thomas Knox





From: time-nuts  on behalf of Nick Sayer via 
time-nuts 
Sent: Monday, March 5, 2018 10:13 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Need a Watch Recommendation

Lots of folks have chimed in on this thread, but I will just add that the Apple 
watch is an NTP client. I’m extremely happy with mine, but the reasons I am are 
far, far wider than its accuracy (which I can only judge by eye, which is an 
extraordinary low bar for a Time Nut).

> On Mar 4, 2018, at 10:38 PM, Don Murray via time-nuts  
> wrote:
>
> Hello Time Nuts...
>
>
>
> After 6 years of no troubles, in sync with WWV any
> hour of the day, flawless transfer between
> standard and daylight time my Stauer Titanium
> Atomic wristwatch bite the dust a year ago.
>
> Since then, Stauer has sent me three replacements,
> each with some type of problem.
>
> So it looks as if I am in need of a new wristwatch,
> which will give me some kind of time accuracy.
>
> So, Time Nuts...  any suggestions or recommendations?
>
> TNX
>
> 73
> Don
> W4WJ
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postings to ...


> and follow the instructions there.

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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] Z3801A OCXO manual trimming

[Tom Holmes]

Bob...

Interesting point about the heater not working vs the XTAL having drifted too 
far. Mine has the same symptoms as the others reported (EFC at the end of its 
rope) but have not tackled it yet, figuring I'd have to dismantle the whole 
thing. Certainly troubleshooting a non-operating heater would be much more 
pleasant.

Thanks for that insight.

Tom Holmes, N8ZM

-Original Message-
From: time-nuts <time-nuts-boun...@febo.com> On Behalf Of Bob kb8tq
Sent: Saturday, March 03, 2018 2:07 PM
To: Tom Curlee <tcur...@sbcglobal.net>; Discussion of precise time and 
frequency measurement <time-nuts@febo.com>
Subject: Re: [time-nuts] Z3801A OCXO manual trimming

Hi

First off some basics about OCXO’s.

In a single oven design, you have a heater that warms up the entire crystal and 
the guts of the oscillator. It is on all the time and 
it gets things up to a temperature that makes sense for a given crystal. It can 
be adjusted based on manufacturing data or by 
trial and error to match the characteristics of that crystal. 

In a double oven design, you have two ovens that are on all the time. One heats 
up the other one. They both work together to
achieve the end result. The gain of one adds to the gain of the other to give 
an improved result. On some double ovens, the 
entire heat range of the inner oven is only 10’s of degrees ….

In a boosted oven, you have a second heater to get things going when it is very 
cold. This is an unusual approach and rarely 
seen. Its normally easier to just design a bit more power into the main oven 
circuit. In a boosted design, the boost heat goes
away in normal operation at typical temperatures. In normal operation, the gain 
of the boost circuit does not count. 

SO ….

The oscillator in the Z3801 is a boosted 10811. It is boosted to allow them to 
hit a spec of -40C on the unit. At the time it was
designed, there was talk about mounting these things in un-heated boxes 
outdoors. After they got a bit further into all the 
details of the designs … that part went away. The spec still hung around long 
enough to apply to very early designs. 

The net result is that you can pretty much destroy the outer heater stuff and 
the oscillator will work fine. There is no need 
for it in a typical lab. There are some alarm triggers that need to be wired 
“ok” when you do so. The details are in the archives. 

But …

Best guess if your unit is at max EFC = the “real” heater on the 10811 has quit 
working. To get at that, you will need to dig 
into the guts of the unit. Given the massive EFC on the Z3801 version of the 
oscillator, it would take a crazy amount of aging
to hit limit.

Bob


> On Mar 3, 2018, at 1:37 PM, Tom Curlee <tcur...@sbcglobal.net> wrote:
> 
> Since the Z3801A is being discussed, I thought I'd ask about an issue I'm 
> having with my unit.  I use my Z3801 as my working lab standard for the usual 
> pieces of RF test equipment.  In the past year or so I've had the unit drop 
> out of lock and go into standby mode.  Resetting/cycling power would bring it 
> back into lock for a while, but it generally got worse and now stays in hold 
> over mode.  LH (thanks Mark Sims!!) reports that everything is operating 
> normally except that the it has a PLL unlock.  The one highly suspicious item 
> is that the DAC is at 99.996902% - full output.
> The unit shows it has over 94.5K hours run time, so I suspect that the OCXO 
> has aged to the point that the EFC can't pull it into lock.  I disassembled 
> the OCXO to see if it had a trimmer capacitor like the standard 10811 units.  
> After removing the outer case and foam insulation, I see that the outer 
> heater is one of the thin printed circuit serpentine heaters on what I think 
> is Kapton.  That would need to be peeled off of the case to either get to the 
> hole for the trimmer (if there is one) or to remove the cover for the inner 
> case.
> What I don't understand is the purpose of what looks like another coil or 
> heater wrapped around the Kapton printed circuit heater stuck to the inner 
> case.  This second coil/heater is 2 layers of 1/8" thick red foam wrapped 
> completely around the inner case, with fine copper wires wrapped over each 
> layer.  At least I think there are wires on each layer.  This whole second 
> heater is taped down and I don't want to dig any further until I know a bit 
> more about what I'm doing or find that there isn't a trimmer on the double 
> oven 10811 oscillators.
> Any ideas on the purpose of the outer heater (or whatever it is)?  Does the 
> double oven 10811 have a manual trimmer that I can adjust to bring the 
> oscillator back to the center of the EFC range?  Assuming that I can manually 
> adjust the OCXO back into adjustment range, will there be any issues with the 
> Z3801 performance, things like phase noise, short term stability, etc?
> An

[time-nuts] Z3801A OCXO manual trimming

[Tom Curlee]

Since the Z3801A is being discussed, I thought I'd ask about an issue I'm 
having with my unit.  I use my Z3801 as my working lab standard for the usual 
pieces of RF test equipment.  In the past year or so I've had the unit drop out 
of lock and go into standby mode.  Resetting/cycling power would bring it back 
into lock for a while, but it generally got worse and now stays in hold over 
mode.  LH (thanks Mark Sims!!) reports that everything is operating normally 
except that the it has a PLL unlock.  The one highly suspicious item is that 
the DAC is at 99.996902% - full output.
The unit shows it has over 94.5K hours run time, so I suspect that the OCXO has 
aged to the point that the EFC can't pull it into lock.  I disassembled the 
OCXO to see if it had a trimmer capacitor like the standard 10811 units.  After 
removing the outer case and foam insulation, I see that the outer heater is one 
of the thin printed circuit serpentine heaters on what I think is Kapton.  That 
would need to be peeled off of the case to either get to the hole for the 
trimmer (if there is one) or to remove the cover for the inner case.
What I don't understand is the purpose of what looks like another coil or 
heater wrapped around the Kapton printed circuit heater stuck to the inner 
case.  This second coil/heater is 2 layers of 1/8" thick red foam wrapped 
completely around the inner case, with fine copper wires wrapped over each 
layer.  At least I think there are wires on each layer.  This whole second 
heater is taped down and I don't want to dig any further until I know a bit 
more about what I'm doing or find that there isn't a trimmer on the double oven 
10811 oscillators.
Any ideas on the purpose of the outer heater (or whatever it is)?  Does the 
double oven 10811 have a manual trimmer that I can adjust to bring the 
oscillator back to the center of the EFC range?  Assuming that I can manually 
adjust the OCXO back into adjustment range, will there be any issues with the 
Z3801 performance, things like phase noise, short term stability, etc?
Any suggestions will be most appreciated.
Thanks,
Tom
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Re: [time-nuts] PRS10 Information and help needed

[Tom Knox]

Hi Arnold;

If you compare the 10MHz to another standard it will most likely show the 
quartz is in free run. Since quartz acts as a fly wheel for the rubidium the 
output would look good from all other aspects (Amplitude and Spectral Purity). 
So it appear to me you are experiencing an issue with the Rubidium Section.

I hope that helps.

Cheer;

Thomas Knox




From: time-nuts  on behalf of Arnold Tibus 

Sent: Wednesday, February 28, 2018 11:47 AM
To: time-nuts@febo.com
Subject: [time-nuts] PRS10 Information and help needed

Hello fellow timenuts,

for my old PRS10 I need some information and help with technical
informations.
I have this item bought quite some years ago and I have manufactured an
interface cable with the special connector last year. Did work fine.
Taken out of storage I do get anymore the lock and PPS signal out.
The 10 MHz output does look very good, the unloaded sine voltage is 2.8
Vpp and the frequency is very precise and stable very close to the
trimble thunderbolt GPS-out signal at abt. 10E-11.
In the annex you can see the data output with more delailed info.
Can somebody tell me more, is the life at the end and what and how can
be done to revitalize this nice time machine? How much time more is
expectable?

kind regards,

Arnold
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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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[time-nuts] An atomic clock used to measure the height of a mountain

[Tom Leedy via time-nuts]

Hi:


By comparing the tick rate of the portable atomic clock on a mountain with a 
similar clock in a lab in Torino, Italy, researchers at Germany’s National 
Metrology Institute showed that the altitude difference between the two 
locations was about 1,000 meters, or 3,280 feet. Their work was published in 
Nature Physics.  A related article here.


Best --
Tom Leedy - Clarksburg, MD




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Re: [time-nuts] Beware the Casio WaveCeptor analog watch

[Tom Knox]

Hi All;

I have has a Citizen as well and it has been bullet proof skiing, cycling and 
such well over five years. I did a quick search because when I purchased it was 
really pricey but a quick search and Zales has what appears the exact model:

Analog Citizen Eco-Drive® Skyhawk Atomic Titanium Solar 200M Flight Chronograph 
Watch (Model: JY0010-50E) $233 shipped. I know that is a bit more expensive but 
it is amazing.

Cheers;


Thomas Knox




From: time-nuts  on behalf of Bob kb8tq 

Sent: Sunday, February 25, 2018 6:30 PM
To: swith...@alum.mit.edu; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Beware the Casio WaveCeptor analog watch

Hi

I’ve had the Citizen “Atomic” analog watches for quite a few years. The solar 
powered
versions have gotten a bit better over the years. They nave never had a “hand 
slip”
problem that I have noticed.

Bob

> On Feb 25, 2018, at 6:52 PM, Skip Withrow  wrote:
>
> Hello Time-Nuts,
>
> For many years I owned a Casio WaveCeptor digital watch and like it a
> lot.  The down side was that the battery had to be replaced every few
> years.  And since I had worn it for many years, the plastic case and
> crystal had taken quite a beating.  Finally, the pin holder that
> secures the band broke - end of watch (except as a 'pocket' watch).
>
> So, I went out and bought a solar powered analog version of the
> WaveCeptor (and vowed not to take it caving).  However, several months
> ago I needed to take an action at an exact time (not ebay) which was a
> miserable fail.  I found that the watch was over a minute off.
>
> I went back and explored the watch manual and found that there is a
> procedure to sync the minute and second hands.  I did this and after
> syncing to WWVB all was good.
>
> Now, a couple of months later I needed the precise time again.
> However I checked my watch before hand and found that it was 8 seconds
> off.  Ahrg!
>
> It appears that the stepper motor position of the second and minute
> hands can be jarred out of sync with normal wear bumps and shocks.
> The trouble is you don't know when it happens (unless you check your
> watch against a trusted source often).
>
> Now I'm seriously considering buying a solar version of the digital
> watch to get rid of the problem.
>
> Regards,
> Skip Withrow
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Re: [time-nuts] HP 5065A super

[Tom McDermott]

It appears that ENIG gold is extremely thin (2 - 8 microinches),
and if so does not cause a solderability problem.

-- Tom, N5EG



On Thu, Feb 22, 2018 at 3:18 PM, Mark Goldberg <marklgoldb...@gmail.com>
wrote:

> My reading of IPC J-STD-001F Paragraph 4.5 says that the gold embrittlement
> issue does not apply to ENIG or ENEPIG. Paragraph 4.5.1 does say other gold
> shall be removed so there won't be solder embrittlement.
>
> Is that still correct?
>
> The issue with ENIG and RF is interesting. I have not heard that before but
> I can find lots of info on the subject. I do not remember seeing ENIG on
> microstrip boards.
>
> Regards,
>
> Mark
>
>
> On Thu, Feb 22, 2018 at 2:33 PM, Tom McDermott <tom.n...@gmail.com> wrote:
>
> > In general it's bad practice to gold plate SMT solder pads.  The reason
> is
> > that proper SMT soldering utilizes a very small amount of solder and the
> > gold plating
> > will partially dissolve into the molten solder. Because of the small
> amount
> > of
> > solder, the percentage of gold will be high enough to embrittle the
> solder
> > joint,
> > and it will have a high probability of failure.
> >
> > Hand soldering can apply a large enough amount of solder that the
> > percentage
> > of gold in the joint is relatively small and the problem is avoided.
> >
> > -- Tom, N5EG
> >
> >
> >
> >
> > On Thu, Feb 22, 2018 at 12:29 PM, Leo Bodnar <l...@leobodnar.com> wrote:
> >
> > > Here is ENIG fact that is not widely known at the moment but which some
> > > might find useful.
> > >
> > > I could not understand why I get better TDR and insertion loss results
> > > from solder-mask covered microstrip transmission lines than from
> > otherwise
> > > identical microstrips on the same substrate with soldermask removed
> and,
> > > therefore, covered with ENIG.
> > >
> > > Gold can't be bad, right? As it turns out, even gold coin has two sides
> > to
> > > it.
> > >
> > > I have found that Shlepnev and McMorrow conducted extensive research
> and
> > > published data, some of which is presented here
> > http://www.simberian.com/
> > > Presentations/NickelCharacterizationPresentation_emc2011.pdf
> > >
> > > In essence, it's not the "G" that is the problem - it is the "N".
> > > Immersion Gold layer is not thick enough to contain whole of the skin
> > > effect layer (even towards 100GHz) and as signal frequency increases
> most
> > > of the signal ends up travelling through Nickel.
> > > As Shlepnev commented "Nickel is the most mysterious metal in
> > > electronics."  It has significant effect on insertion loss and risetime
> > > degradation.  "Significant effect" is posh for "bad."
> > >
> > > Some mass PCB manufacturers have been known to apply ENIG before
> > > soldermasking.  This causes even more high speed/frequency problems
> > because
> > > all of the copper on the outside layers will have Nickel over it -
> > exposed
> > > or not.
> > >
> > > Probably not a problem for majority of ENIG users but could cause a
> > > headache or two for unsuspecting.
> > >
> > > Leo
> > >
> > > > Date: Thu, 22 Feb 2018 19:02:25 +
> > > > From: Mark Sims <hol...@hotmail.com>
> > > >
> > > > Yes, have the board done with ENIG gold.  It typically adds around
> $15
> > > per run of boards.  I do all my boards with ENIG gold... if for no
> other
> > > reason than the gold color makes it very easy to determine when your
> > solder
> > > paste properly covers the pads.
> > > >
> > > > And, as Charles mentioned,  the quality and thickness of the gold can
> > > vary depending upon the board house.  I have used gojgo.com for a lot
> of
> > > boards.  They do very good, quick work,  are well priced, and they seem
> > to
> > > have the best gold finish.
> > > >
> > > > Hard gold finish is VERY expensive these days.  I've been quoted
> $250+
> > > for setup charges and per-board costs of over $25.
> > >
> > > ___
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> > > mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
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> > ailman/listinfo/time-nuts
> > and follow the instructions there.
> >
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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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and follow the instructions there.

Re: [time-nuts] HP 5065A super

[Tom McDermott]

In general it's bad practice to gold plate SMT solder pads.  The reason is
that proper SMT soldering utilizes a very small amount of solder and the
gold plating
will partially dissolve into the molten solder. Because of the small amount
of
solder, the percentage of gold will be high enough to embrittle the solder
joint,
and it will have a high probability of failure.

Hand soldering can apply a large enough amount of solder that the percentage
of gold in the joint is relatively small and the problem is avoided.

-- Tom, N5EG




On Thu, Feb 22, 2018 at 12:29 PM, Leo Bodnar <l...@leobodnar.com> wrote:

> Here is ENIG fact that is not widely known at the moment but which some
> might find useful.
>
> I could not understand why I get better TDR and insertion loss results
> from solder-mask covered microstrip transmission lines than from otherwise
> identical microstrips on the same substrate with soldermask removed and,
> therefore, covered with ENIG.
>
> Gold can't be bad, right? As it turns out, even gold coin has two sides to
> it.
>
> I have found that Shlepnev and McMorrow conducted extensive research and
> published data, some of which is presented here http://www.simberian.com/
> Presentations/NickelCharacterizationPresentation_emc2011.pdf
>
> In essence, it's not the "G" that is the problem - it is the "N".
> Immersion Gold layer is not thick enough to contain whole of the skin
> effect layer (even towards 100GHz) and as signal frequency increases most
> of the signal ends up travelling through Nickel.
> As Shlepnev commented "Nickel is the most mysterious metal in
> electronics."  It has significant effect on insertion loss and risetime
> degradation.  "Significant effect" is posh for "bad."
>
> Some mass PCB manufacturers have been known to apply ENIG before
> soldermasking.  This causes even more high speed/frequency problems because
> all of the copper on the outside layers will have Nickel over it - exposed
> or not.
>
> Probably not a problem for majority of ENIG users but could cause a
> headache or two for unsuspecting.
>
> Leo
>
> > Date: Thu, 22 Feb 2018 19:02:25 +
> > From: Mark Sims <hol...@hotmail.com>
> >
> > Yes, have the board done with ENIG gold.  It typically adds around $15
> per run of boards.  I do all my boards with ENIG gold... if for no other
> reason than the gold color makes it very easy to determine when your solder
> paste properly covers the pads.
> >
> > And, as Charles mentioned,  the quality and thickness of the gold can
> vary depending upon the board house.  I have used gojgo.com for a lot of
> boards.  They do very good, quick work,  are well priced, and they seem to
> have the best gold finish.
> >
> > Hard gold finish is VERY expensive these days.  I've been quoted $250+
> for setup charges and per-board costs of over $25.
>
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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] Outdoor GPS Antenna Selection

[Tom Miller]

Good quality RG6 has less loss and the mismatch is small. You see a lot of 
GPS receivers and antennas with F connectors even though they generally are 
50 ohms. 26 dB of gain should work fine for 20 feet of RG6. Probably also 
good for good RG58.






- Original Message - 
From: "Duane Wheaton" 

To: 
Sent: Sunday, January 07, 2018 10:59 PM
Subject: [time-nuts] Outdoor GPS Antenna Selection


I'm selecting an outdoors antenna for a Jupiter Pico T Timing GPS 
(TU36-D400-020) but don't clearly understand what "dB" rating of amplified 
antenna to use. From web references, it looks like the degree of 
amplification required is dependent on 1.) The length of run of coax 
lead-in, combined with the characteristic loss of the type of coax used 2.) 
The amount of amplification needed to increase the very weak GPS signal to 
the range the receiver requires it. If I'm running 20 feet of RG-58, would a 
26dB antenna be sufficient?


The datasheet for the receiver family states, "1575.42 MHz at a level 
between –115 dBm and –133 dBm into a 50 Ω impedance." So the receiver needs 
at max a -115 dBm signal. The typical received signal power from a GPS 
satellite is −127.5 dBm. So it looks like I need to amplify the RF signal 
for the GPS receiver requirements + compensate for the high loss of the GHz 
signal traveling through ordinary RG-58 coax. Am I on track, here? 
Recommendations?


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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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[time-nuts] Tourbillon: Recalling and honoring our heritage

[Tom Knox]

Hi All;

Happy New Years - This may be common knowledge but before Quartz it was 
difficult for a watch to keep accurate time in a watch vs a pendulum clock due 
to motion and gravity.

Then several centuries ago the Tourbillon movement was design by a Time-Nut 
like ourselves. I my humble opinion it is still one of the most amazing feats 
of engineering ever. And if you are lucky enough to own one you could trade it 
for a Time-Nuts dream lab today.

https://en.wikipedia.org/wiki/Tourbillon

[https://upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Stuhrling_Tourbillon_Movement.ogv/1200px--Stuhrling_Tourbillon_Movement.ogv.jpg]<https://en.wikipedia.org/wiki/Tourbillon>

Tourbillon - Wikipedia<https://en.wikipedia.org/wiki/Tourbillon>
en.wikipedia.org
In horology, a tourbillon (/ t ʊər ˈ b ɪ l j ən /; French: [tuʁbijɔ̃] 
"whirlwind") is an addition to the mechanics of a watch escapement. Developed 
around ...

Peace;

Tom Knox





From: time-nuts <time-nuts-boun...@febo.com> on behalf of Jeremy Nichols 
<jn6...@gmail.com>
Sent: Wednesday, January 3, 2018 9:56 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Recalling and honoring our heritage

Really enjoyable, thank you for the link!

Jeremy


On Wed, Jan 3, 2018 at 7:03 AM William H. Fite <omni...@gmail.com> wrote:

> I was chided in somewhat patronizing terms by one long-time member of this
> group a while back for "wasting our time with obsolete crap that no one
> cares about."
>
> Brace yourselves, I'm going to do it again.
>
> Attached is a video (one of a series) documenting the design and
> construction of mechanical watches. My sarcastic critic notwithstanding, it
> is a mistake to disregard our horological heritage. This is from whence we
> came. In a very real way, this is who we are.
>
> Take a look at what can be accomplished with gears, wheels, and springs. It
> is a quest for perfection every bit bit as serious and dedicated as the
> quest for electronic clocks with accuracy in the attasecond range.
>
> Or just mutter under your breath and smack the delete key.
>
> https://youtu.be/hoO7PtR0ujY
[https://i.ytimg.com/vi/hoO7PtR0ujY/hqdefault.jpg]<https://youtu.be/hoO7PtR0ujY>

Watchmaking art part 1<https://youtu.be/hoO7PtR0ujY>
youtu.be
Watchmaker documentary


>
>
>
> --
> Patriotism is supporting your country all the time, and your government
> when it deserves it.
> --Mark Twain
>
> We may be surprised at the people we find in heaven. God has a soft spot
> for sinners. His standards are quite low.
> --Desmond Tutu
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> and follow the instructions there.
>
--
Sent from my iPad 4.
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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 Holmes]

Mark...
You're place really moved a foot in 48 hours? Impressive and scary!

>From Tom Holmes, N8ZM

> On Dec 9, 2017, at 8:19 PM, Mark Sims <hol...@hotmail.com> wrote:
> 
> Which gets real fun with things like solid earth tides getting involved.   
> Lady Heather can now calculate and plot solid earth tides.   Over the last 48 
> hours my place moved up/down 315 mm and gravity changed 186  microgals... and 
> that was a rather stable period.
> 
> --
> 
>> 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.
> 
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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] End-of-Range: Oscilloquartz OCXO 8600-3

[Tom Knox]

Happy Holidays Magnus!  What I was wondering was that the BVA is somewhat 
unique since other oscillators have metal directly deposited over the quartz 
resonator, where the BVA is capacitive coupled. I was wondering if that made 
the quartz age less if at all.

Cheers;

Thomas Knox




From: time-nuts <time-nuts-boun...@febo.com> on behalf of Magnus Danielson 
<mag...@rubidium.dyndns.org>
Sent: Friday, December 8, 2017 11:32 AM
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3

Hi,

There is sources of drift all over the place.

The crystal has drift in it, the oscillator core has sources of drift.

Already within a crystal there is a bunch of sources. Some can
compensate each other.

Improvements in production have reduced effects, but there is always
something that drifts, somewhat.

Cheers,
Magnus

On 12/08/2017 06:27 PM, Tom Knox wrote:
> Hi All;
>
> Is the "Aging" generally related to the quartz, or other components?
>
> Happy-Merry;
>
> Thomas Knox
>
>
>
> 
> From: time-nuts <time-nuts-boun...@febo.com> on behalf of Bob kb8tq 
> <kb...@n1k.org>
> Sent: Friday, December 8, 2017 9:58 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3
>
> Hi
>
> One risk is that the oscillator may have drifted further than one can easily 
> adjust it by
> just changing a select cap. That seems silly when we are talking about < 1 
> ppm, but
> the 8600 is an unusual OCXO. The electrodes BVA is not your run of the mill 
> crystal.
> The “air gap” (actually a gap in vacuum) puts a pretty small capacitance in 
> series with
> the normal crystal equivalent circuit. That cuts the practical tuning range 
> down quite
> a bit….
>
> Bob
>
>> On Dec 8, 2017, at 11:44 AM, Magnus Danielson <mag...@rubidium.dyndns.org> 
>> wrote:
>>
>> Hi,
>>
>> Many include a EFC offset pot, but when you go out of range on that, as I 
>> have for one of mine, here is no real option execept pop the lid and 
>> potentially find a cap or change a cap. I have not seen any as I recall, but 
>> should maybe take a look.
>>
>> However, the value for me is not to have it as sharp 5 MHz source, but very 
>> low phase noise and high stability source as reference for measurement. The 
>> offset error is less of a concern then, so that is why I have not spent 
>> quality time to fix it.
>>
>> Cheers,
>> Magnus
>>
>> On 12/08/2017 04:52 PM, paul swed wrote:
>>> I took a quick look at the spec sheet.
>>> It appears coarse adjustment is an option M and would actually be a pot.
>>> That speaks to another tuning diode for coarse? Or a pot on pot arrangement.
>>> That sounds ugly.
>>> Regards
>>> Paul
>>> WB8TSL
>>> On Fri, Dec 8, 2017 at 10:17 AM, Bob kb8tq <kb...@n1k.org> wrote:
>>>> Hi
>>>>
>>>> It is quite possible that nothing is actually broken and that the crystal
>>>> has simply drifted
>>>> outside the tuning range. It should be pretty easy to spot the coarse
>>>> tuning device once
>>>> the package is open. I would bet you will find a selected capacitor across
>>>> the coarse tune or in
>>>> series with the coarse tune. Changing the value of that cap should bring
>>>> things back on
>>>> frequency. I would avoid changing caps across the EFC tuning diode.
>>>>
>>>> Bob
>>>>
>>>>> On Dec 8, 2017, at 8:05 AM, Ulf Kylenfall via time-nuts <
>>>> time-nuts@febo.com> wrote:
>>>>>
>>>>>
>>>>> Gentlemen,
>>>>> We have an Oscilloquartz OCXO 8600-3that cannot any longer be adjusted
>>>> into 5,000,000 Hz.It is about 1 Hz out of 5 MHz and turning
>>>> coarse/fineadjustment potentiometers cannot bring the frequencyinto its
>>>> specification.
>>>>> Oven temperature is about + 80C accordingto the thermistor and the
>>>> operating voltageis at 24 VDC.
>>>>> Have Googled but the only thing that turns upis datasheets w/o any
>>>> details.
>>>>> Before I take it apart and start lookingfor obviously broken components,
>>>> isthere anyone that has a CLIP on this unit?
>>>>> 73
>>>>>
>>>>> Ulf Kylenfall - SM6GXV
>>>>> ___
>>>>> time-nuts mailing list -- ti

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

[Tom McDermott]

There's an interesting article in the December 2017 issue of IEEE Spectrum.

Researchers at Oxford U. have fabricated an atomic reference based on
a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene").
The cage of carbon isolates the nitrogen from external electric fields,
and they've developed a method to also isolate it from external magnetic
fields.

They have not incorporated the material into a working standard, but have
licensed the chemical fabrication technology to at least one manufacturer.
The idea is to make a chip-scale atomic frequency reference.

-- Tom, N5EG
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Re: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3

[Tom Knox]

Hi All;

Is the "Aging" generally related to the quartz, or other components?

Happy-Merry;

Thomas Knox




From: time-nuts  on behalf of Bob kb8tq 

Sent: Friday, December 8, 2017 9:58 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3

Hi

One risk is that the oscillator may have drifted further than one can easily 
adjust it by
just changing a select cap. That seems silly when we are talking about < 1 ppm, 
but
the 8600 is an unusual OCXO. The electrodes BVA is not your run of the mill 
crystal.
The “air gap” (actually a gap in vacuum) puts a pretty small capacitance in 
series with
the normal crystal equivalent circuit. That cuts the practical tuning range 
down quite
a bit….

Bob

> On Dec 8, 2017, at 11:44 AM, Magnus Danielson  
> wrote:
>
> Hi,
>
> Many include a EFC offset pot, but when you go out of range on that, as I 
> have for one of mine, here is no real option execept pop the lid and 
> potentially find a cap or change a cap. I have not seen any as I recall, but 
> should maybe take a look.
>
> However, the value for me is not to have it as sharp 5 MHz source, but very 
> low phase noise and high stability source as reference for measurement. The 
> offset error is less of a concern then, so that is why I have not spent 
> quality time to fix it.
>
> Cheers,
> Magnus
>
> On 12/08/2017 04:52 PM, paul swed wrote:
>> I took a quick look at the spec sheet.
>> It appears coarse adjustment is an option M and would actually be a pot.
>> That speaks to another tuning diode for coarse? Or a pot on pot arrangement.
>> That sounds ugly.
>> Regards
>> Paul
>> WB8TSL
>> On Fri, Dec 8, 2017 at 10:17 AM, Bob kb8tq  wrote:
>>> Hi
>>>
>>> It is quite possible that nothing is actually broken and that the crystal
>>> has simply drifted
>>> outside the tuning range. It should be pretty easy to spot the coarse
>>> tuning device once
>>> the package is open. I would bet you will find a selected capacitor across
>>> the coarse tune or in
>>> series with the coarse tune. Changing the value of that cap should bring
>>> things back on
>>> frequency. I would avoid changing caps across the EFC tuning diode.
>>>
>>> Bob
>>>
 On Dec 8, 2017, at 8:05 AM, Ulf Kylenfall via time-nuts <
>>> time-nuts@febo.com> wrote:


 Gentlemen,
 We have an Oscilloquartz OCXO 8600-3that cannot any longer be adjusted
>>> into 5,000,000 Hz.It is about 1 Hz out of 5 MHz and turning
>>> coarse/fineadjustment potentiometers cannot bring the frequencyinto its
>>> specification.
 Oven temperature is about + 80C accordingto the thermistor and the
>>> operating voltageis at 24 VDC.
 Have Googled but the only thing that turns upis datasheets w/o any
>>> details.
 Before I take it apart and start lookingfor obviously broken components,
>>> isthere anyone that has a CLIP on this unit?
 73

 Ulf Kylenfall - SM6GXV
 ___
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 To unsubscribe, go to https://www.febo.com/cgi-bin/
>>> mailman/listinfo/time-nuts
 and follow the instructions there.
>>>
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>>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
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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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