Re: [time-nuts] PLL performance?

[Bill Byrom]

Hi, Scott. I rarely post here, but just noticed your post. I can open
the "PLL0.pdf" file, but the other files appears to be corrupted. Adobe
Acrobat Reader thinks it's not really a PDF file or it's corrupted. I'm
not ready to comment on the expected results yet, and would like to see
the histogram. 

Are you using phase detector 1 or 2? What are the details for your loop
filter?

--
Bill Byrom N5BB

- Original message -
From: David Scott Coburn 
To: time-nuts@febo.com
Subject: [time-nuts] PLL performance?
Date: Mon, 20 Mar 2017 21:07:03 -0400

Hi All,

I have built and tested a PLL circuit that will be used to generate a 1
MHz signal locked to a 0.5 HZ signal from a pendulum.  (Details
available upon request.)

The circuit is a classic 4046 generating the 1 MHz signal which is fed
into a 2e6 digital divider which outputs 0.5 Hz which is fed back to the
4046 phase comparator (PC).

I take a 1 MHz signal from an HP 107A run through another 2e6 divider to
generate a reference 0.5 Hz signal for the other 4046 PC input.

I tested this by feeding the 0.5 Hz output of the PLL into a "time-stamp
counter" board which I built to go into an HP 3582A Data Acquisition
unit.  The TSC uses the 5 MHz signal from the HP 107A to feed a
free-running 32-bit binary counter.  The 0.5 Hz input latches the count
value (on the rising edge of the signal), which is then logged.

See the attached diagram.  The PLL under test is in the red box.  (Not
sure what the policy is here for attachments?)

If all was perfect I would get a string of values of 10,000,000 counts
each, one every 2 seconds.

Over the course of one day the average reading is, in fact, 10e6, so the
PLL looks to be working over "long" time scales.

The attached histogram plot shows the actual data for the 0.5 Hz signal,
showing the distribution of deviations from 10e6 counts.  This is almost
a full day of data, about 40,000 readings.

The standard deviation for the data is about 55 counts.

The plot looks to my eye to be a nice Gaussian shape, so I assume that
the deviations are caused mainly by (white?) noise.  There does not look
to be much other structure in the shape of the data.  (Comments
welcome.)

Sorry for the long introduction, there are some questions coming!

I have looked for information on the web about others who may have done
this kind of PLL, but did not find much.

Does anyone know of any articles related to this?

If so, do you know what kind of performance they got?

What kind of statement could I make about the 'stability' of this
circuit?  Simplistically: a 'stability' of ~50 counts in 10e6 is ~5e-7?

By the way, this performance is WAY WAY beyond what I was expecting

Cheers,

Scott
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Email had 2 attachments:
+ PLL0.pdf
  22k (application/pdf)
+ histogram-utcday21613x.pdf
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[time-nuts] PLL Digital Loop Filter

[James Peroulas]

I'm trying to understand how to design and analyze the loop filters in a
digital PLL. Specifically, because of digital processing delays, the phase
offset measured at time t will only produce a change on the VCXO input at
time t+T, where T is the sampling period of the digital loop.

I've found plenty of texts describing analog loop filters. Are there any
recommendations for digital loop filter PLL design?

Thanks,
James
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Re: [time-nuts] HP5061B Ion Current

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

I could not figure out why the A15 Ion Current monitor would not let
the cesium oven turn on with ion current under 25 uA.  At the time we
had no way of measuring the +3,500 ion pump supply.  We bought some
200 Meg resistors and made a crude HV meter to feed our 10 Meg Fluke
77.  The supply had sagged to 2000 Volts with that load.  This
prevented the ion pump current monitor from energizing the cesium
oven.

KB7APQ unsoldered the can on the 3,500 Volt supply with suggestions
from WB4BBP.  It is a horrible design and we studied it.  R4 is set at
the factory to produce 3,500 Volts with no load.  It runs at 704
pulses per second and sags badly with the slightest load.  This
prevents the ion pump from clearing the gas in the beam tube.  The pot
core transformer is plenty big that it appears that the supply can put
out 5 mA at 3,500 volts.  This allows it to replace the external
supply recommended by HP for gassy tubes.

It looks like that it can run at 10 kc with existing pot core
transformer.  The pulse width looks like it can be doubled as well.
This allows for a 30 to 1 increase in output power.  A small circuit
board will regulate the voltage as well as limit the current.
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Re: [time-nuts] PLL performance?

[Daniel Mendes]

Hi. I did a 15728640Hz signal locked to a 7680Hz reference using a 
74hct9046. It was ugly (I mean, individual trimming of the resistors... 
I assembled 20 boards). Circuit behaves more like a FLL than a PLL (if 
you look at both with an scope they never quite locks to each other), 
but it works for the mean values (so long averages are ok, and that´s 
what I was looking for). I didn´t measure stability, just tested each 
board to see if they kept locked between (60,1*128)Hz and (59,9*128)Hz. 
That was a pain. I think these 4046 and 9046 don´t work well when the 
frequencies are too apart, but I can´t tell for sure. Not enough 
experience with that.


Daniel


Em 20/03/2017 22:07, David Scott Coburn escreveu:

Hi All,

I have built and tested a PLL circuit that will be used to generate a 1 MHz 
signal locked to a 0.5 HZ signal from a pendulum.  (Details available upon 
request.)

The circuit is a classic 4046 generating the 1 MHz signal which is fed into a 
2e6 digital divider which outputs 0.5 Hz which is fed back to the 4046 phase 
comparator (PC).

I take a 1 MHz signal from an HP 107A run through another 2e6 divider to 
generate a reference 0.5 Hz signal for the other 4046 PC input.

I tested this by feeding the 0.5 Hz output of the PLL into a "time-stamp 
counter" board which I built to go into an HP 3582A Data Acquisition unit.  The TSC 
uses the 5 MHz signal from the HP 107A to feed a free-running 32-bit binary counter.  The 
0.5 Hz input latches the count value (on the rising edge of the signal), which is then 
logged.

See the attached diagram.  The PLL under test is in the red box.  (Not sure 
what the policy is here for attachments?)

If all was perfect I would get a string of values of 10,000,000 counts each, 
one every 2 seconds.

Over the course of one day the average reading is, in fact, 10e6, so the PLL looks to be 
working over "long" time scales.

The attached histogram plot shows the actual data for the 0.5 Hz signal, 
showing the distribution of deviations from 10e6 counts.  This is almost a full 
day of data, about 40,000 readings.

The standard deviation for the data is about 55 counts.

The plot looks to my eye to be a nice Gaussian shape, so I assume that the 
deviations are caused mainly by (white?) noise.  There does not look to be much 
other structure in the shape of the data.  (Comments welcome.)

Sorry for the long introduction, there are some questions coming!

I have looked for information on the web about others who may have done this 
kind of PLL, but did not find much.

Does anyone know of any articles related to this?

If so, do you know what kind of performance they got?

What kind of statement could I make about the 'stability' of this circuit?  
Simplistically: a 'stability' of ~50 counts in 10e6 is ~5e-7?

By the way, this performance is WAY WAY beyond what I was expecting

Cheers,

Scott


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[time-nuts] Time Dilation tinkering

[Hugh Blemings]

Hi,

I've been mostly lurking on the list for some time now and follow with 
interest the many discussions.  Very much at the early stages of my 
time-nut journey, but enjoying it so far :)


I'd like to have a go at re-creating the efforts of Tom (and I gather 
others) in taking a clock up a mountain for a while and seeing if I can 
measure the relativistic changes.


Being based in Australia gives me a couple of challenges, for one we 
don't really do mountains in the same sense as much of the rest of the 
world - so the highest peak I can readily get to from Melbourne is about 
1,600m ASL.  I live at 80m ASL - so a delta of around 1,500m altitude 
and several hundred km drive.


If I do the math correctly that's about 14ns difference per 24h the 
clocks are separated by that altitude. [1]


We also lack quite the same surplus market here as the US, so purchasing 
a Caesium based standard is well beyond my means.


This got me to wondering if a Rubidium based standard might do the trick 
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.


Clearly there'd need to be a bunch of extra gubbins [2] added to the 
10MHz standard to turn it into an actual clock/counter including battery 
backup and so forth.  And would need a pair of everything.


Before I delve too far into the planning, I'd be interested in feedback 
as to whether this style of Rb standard is likely to be up to the task 
of being the core of such an endeavour or not ?


Oh I should add - my plan was to build the systems such that they 
function as nice standalone time/frequency references once this 
experiment is concluded :)


Thanks in advance,

Kind Regards/73,
Hugh
VK3YYZ/AD5RV



[1] gh/c^2 x 3600 x 24  Where h is 1500, g and c the usual values :)

[2] I presume at a minimum a counter running at a 5ns or less "tick" fed 
from a frequency source locked to the 10MHz of the Rb standard.  This 
counter would need to be latched for reading from an external signal so 
that it can be compared to the second clock.  Not sure but seems the 
TAPR TICC might have role here :)

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Re: [time-nuts] HP5061B Ion Current

[Hal Murray]

trojancow...@gmail.com said:
> We will discuss our findings if there is interest. 

This is time-nuts.  Of course there is interest.


What fraction of the old/dead tubes are "gassy"?

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] HP5061B Ion Current

[paul swed]

Donald welcome to the group. If a units been off a long time and it sure
sounds like thats the case it may take quite a while like a month or so for
the unit to remove all of the "Stuff" that has out gassed. So be patient
and let the pump do its job. After it does lower and my fingers are
crossed. Then you only need to run it about every 6 months.
The fact that it actually locks and you found a simple fix is pretty good.
What was the beam current?? That gives you a hint on the quality of the
tube.

Not sure I would run the defeat on the HV supply for to long. That may
stress the supply if I had to guess.
Regards
Paul
WB8TSL

On Mon, Mar 20, 2017 at 7:44 PM, Donald E. Pauly 
wrote:

> This is my first post.  I just bought a non-working HP5061B on eBay
> for $350.  My old boss KB7APQ in Salt Lake City and I are working on
> it.  It came in from the Philipines in October of 2015 and was
> diagnosed with a bad physics package in March 2016 by AllTest in New
> Jersey.  We initially found an open R8 pot on the 5 mc oscillator
> A10A2 which was killing most of the output.
>
> Next we had ion current of about 25 uA which stayed up.  The book
> seems to indicate that this was low enough to enable the cesium oven.
> The analysis of the theoretical ion current for cesium turn on was
> very difficult.  We shorted the base emitter of Q6 on A15 board to
> override Cesium oven disable. The instrument then achieved lock with
> beam current of 20.  Ion current rose to 35 after cesium oven warm up
> and lock.
>
> We have made great progress on the +3500V power supply analysis.  We
> believe that many so called gassy tubes are perfectly functional up to
> 1 mA ion current.  Mean free path is on the order of 142 mm in that
> case or the length of the beam.  We will discuss our findings if there
> is interest.
>
> WB4BBP has been most helpful with our efforts.
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Re: [time-nuts] HP5061B Ion Current

[Pete Lancashire]

Do a search of the list and a few other sites. there is a LOT of
information on what challenges one can have.
And a lot of the information is practical.

As for as pumping a tube down, it took me pretty much a day + a whole
weekend, but it did go down to what was
scribbled on the door, and now takes less than a minute. I only turned mine
on either once every 2-3 months or when
I wanted to use it. Before the current issue of what looks like a power
supply going nuts, I got lock in no more that
203 minutes. If I was not going to use it, I would let it run for 30-45
minutes and shut it down for the next 'pump down'

-pete



On Mon, Mar 20, 2017 at 4:44 PM, Donald E. Pauly 
wrote:

> This is my first post.  I just bought a non-working HP5061B on eBay
> for $350.  My old boss KB7APQ in Salt Lake City and I are working on
> it.  It came in from the Philipines in October of 2015 and was
> diagnosed with a bad physics package in March 2016 by AllTest in New
> Jersey.  We initially found an open R8 pot on the 5 mc oscillator
> A10A2 which was killing most of the output.
>
> Next we had ion current of about 25 uA which stayed up.  The book
> seems to indicate that this was low enough to enable the cesium oven.
> The analysis of the theoretical ion current for cesium turn on was
> very difficult.  We shorted the base emitter of Q6 on A15 board to
> override Cesium oven disable. The instrument then achieved lock with
> beam current of 20.  Ion current rose to 35 after cesium oven warm up
> and lock.
>
> We have made great progress on the +3500V power supply analysis.  We
> believe that many so called gassy tubes are perfectly functional up to
> 1 mA ion current.  Mean free path is on the order of 142 mm in that
> case or the length of the beam.  We will discuss our findings if there
> is interest.
>
> WB4BBP has been most helpful with our efforts.
> ___
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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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[time-nuts] PLL performance?

[David Scott Coburn]

Hi All,

I have built and tested a PLL circuit that will be used to generate a 1 MHz 
signal locked to a 0.5 HZ signal from a pendulum.  (Details available upon 
request.)

The circuit is a classic 4046 generating the 1 MHz signal which is fed into a 
2e6 digital divider which outputs 0.5 Hz which is fed back to the 4046 phase 
comparator (PC).

I take a 1 MHz signal from an HP 107A run through another 2e6 divider to 
generate a reference 0.5 Hz signal for the other 4046 PC input.

I tested this by feeding the 0.5 Hz output of the PLL into a "time-stamp 
counter" board which I built to go into an HP 3582A Data Acquisition unit.  The 
TSC uses the 5 MHz signal from the HP 107A to feed a free-running 32-bit binary 
counter.  The 0.5 Hz input latches the count value (on the rising edge of the 
signal), which is then logged.

See the attached diagram.  The PLL under test is in the red box.  (Not sure 
what the policy is here for attachments?)

If all was perfect I would get a string of values of 10,000,000 counts each, 
one every 2 seconds.

Over the course of one day the average reading is, in fact, 10e6, so the PLL 
looks to be working over "long" time scales.

The attached histogram plot shows the actual data for the 0.5 Hz signal, 
showing the distribution of deviations from 10e6 counts.  This is almost a full 
day of data, about 40,000 readings.

The standard deviation for the data is about 55 counts.

The plot looks to my eye to be a nice Gaussian shape, so I assume that the 
deviations are caused mainly by (white?) noise.  There does not look to be much 
other structure in the shape of the data.  (Comments welcome.)

Sorry for the long introduction, there are some questions coming!

I have looked for information on the web about others who may have done this 
kind of PLL, but did not find much.

Does anyone know of any articles related to this?

If so, do you know what kind of performance they got?

What kind of statement could I make about the 'stability' of this circuit?  
Simplistically: a 'stability' of ~50 counts in 10e6 is ~5e-7?

By the way, this performance is WAY WAY beyond what I was expecting

Cheers,

Scott

PLL0.pdf
Description: Adobe PDF document


histogram-utcday21613x.pdf
Description: Adobe PDF document
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[time-nuts] HP5061B Ion Current

[Donald E. Pauly]

This is my first post.  I just bought a non-working HP5061B on eBay
for $350.  My old boss KB7APQ in Salt Lake City and I are working on
it.  It came in from the Philipines in October of 2015 and was
diagnosed with a bad physics package in March 2016 by AllTest in New
Jersey.  We initially found an open R8 pot on the 5 mc oscillator
A10A2 which was killing most of the output.

Next we had ion current of about 25 uA which stayed up.  The book
seems to indicate that this was low enough to enable the cesium oven.
The analysis of the theoretical ion current for cesium turn on was
very difficult.  We shorted the base emitter of Q6 on A15 board to
override Cesium oven disable. The instrument then achieved lock with
beam current of 20.  Ion current rose to 35 after cesium oven warm up
and lock.

We have made great progress on the +3500V power supply analysis.  We
believe that many so called gassy tubes are perfectly functional up to
1 mA ion current.  Mean free path is on the order of 142 mm in that
case or the length of the beam.  We will discuss our findings if there
is interest.

WB4BBP has been most helpful with our efforts.
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Re: [time-nuts] Four hour cycle in GPS NMEA jitter

[Gary E. Miller]

Yo Chris!

On Mon, 20 Mar 2017 15:19:25 -0700
Chris Albertson  wrote:

> I've only hear of 1 uS being broken with hardware.

A Raspberry Pi can get down to a Standard Deviation of about 350 nano seconds
using NTPsec..

https://blog.ntpsec.org/2017/02/01/heat-it-up.html


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] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[Mark Sims]

The "DAC" was PWM based, but used a separate voltage regulator for the 
"reference".  I never tried it using the USB power as the reference.

The OCXO (+board) uses less than 500 mA warming up (which it does rather 
quickly).  It's in a small hermetic package about twice the size of a standard 
DIP-14 oscillator package.  There was a Ebay seller several years ago offering 
them at $15 each or 10 for $100.

The Chinese "Arduino" board (it's not really and Arduino,  just a MEGA 328 and 
a proto area)  has a micro-USB connector for power input but does not implement 
USB data.   I used the processor serial port with a level shifter dongle.   The 
firmware was a cheap and dirty hack and I didn't implement  much in the way of 
control or monitoring... never got around to improving it.  The project was 
basically "Hey, I forgot I had those parts...  Hmmm, one could build a simple 
GPSDO... why not?

-

> Did you use the Arduino's PWM output plus a LPF for the DAC, or a separate
DAC? If PWM, did you have problems with noise or sensitivity to the
USB-provided supply voltage?
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Re: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[Attila Kinali]

Moin,

On Mon, 20 Mar 2017 17:11:36 -0400
"William H. Fite"  wrote:

> You are talking about product design, development and optimization, not the
> production of a one-off for home use. Since performance standards are
> already well established, it is only necessary for the developer to test
> the bench built instrument against published standards and determine if
> performance is good enough to suit him. Given a sound understanding of the
> role of various components in the system, it will be a great deal faster
> and easier for the builder to tinker with the one-off then to go through an
> extensive process of model development and verification.
> 
> I have spent a good deal of my career doing performance modeling,
> verification, and validation in collaboration with other scientists and
> also engineers. You describe the process correctly but I think it is
> generous overkill for the topic under discussion here. Or have I missed
> something in the discussion? Is the desired end result a device for
> manufacture and sale? If so, then your approach is right on target.

The question kind of started of from how to verify a GPSDO works correctly.
My answer to that was to use a known-good GPSDO and an vapor cell Rb standard.
Both can be had for quite cheap (<200$ each) or borrowed from a fellow
time-nut. With this and a suitable counter (e.g. PICTIC or TICC) one can
verify the homebew GPSDO quickly and quantify the result.

Chris Albertson injected, that he wanted to do the verification with stuff
he could build on his own, not relying on another GPSDO or "expensive" Rb
standard. I then showed that, while possible to do so, it takes a lot of
effort and time to verify instruments without using known-good references.

Yes, you are right that for Joe Average, this is way overkill. For most
it will be enough to check whether the GPSDO is within 10-20ns of another
GPS (without DO) receiver, and whether the EFC correlates well with the
temperature of the OCXO housing. Both checks can be done relatively quickly,
given access to a counter, a precise thermometer, and a DMM.

But then, this is time-nuts. We love to get the best out of a specific
system... even if it takes more effort than just simply buying better
equipment :-)


Attila Kinali
-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] Four hour cycle in GPS NMEA jitter

[Kiwi Geoff]

Hi Trent,

> But first things first.  I'm just grabbing the time from NMEA sentences.
> And there's quite a bit of jitter there!  Clearly using the first sentence
> output by the GPS is critical.  I've tried to account for any time delays in
> the software.  I think it's the GPS module that is creating the largest
> source of jitter.  It appears to go in four hour cycles, peaking at 0:00Z,
> 4:00Z, 8:00Z, etc.

>From my observations on various GPS receivers, the 'time" that the
NMEA data is transmitted can be highly variable.

For example, here is a (24 hour) graph from my Garmin 18x (firmware
v3.6) where a plot (thanks to Hal) shows the start time of the NMEA
sentence from the time of the GPS 1PPS edge.

http://www.satsignal.eu/ntp/Garmin-18x-3.7.png

David Taylor explains more about this Garmin firmware variation here:

http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm

Where an earlier version of the 18x, the latency could be so long
that it actually gave the timestamp for the wrong second !

So yes, beware of using the "transmit time" of NMEA sentences, many
GPS receivers appear to have a cuppa tea, a scone and solve a Sudoko
before telling us the time !

Regards, Kiwi Geoff  (Christchurch , New Zealand).
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Re: [time-nuts] Four hour cycle in GPS NMEA jitter

[Bob Camp]

Hi


NMEA sentences are not the best thing to use for timing. If you *do* decide to 
use them, configure the 
receiver so that one and only one sentence comes out. Any time you have more 
than one, you run the risk
of collision in the serial buffer on the part. Next thing to do is to pick the 
shortest useful sentence you 
can find. In some cases you only have one option. 

Next up is to be sure that your PC is set up so that there is minimal lag in 
serial processing. That may not
be as simple as you might think. All modern OS’s head off to do “interesting 
things” from time to time. The
usual approach is to kill just about anything that *might* create an issue. 

Once you have all that, you start pruning the outliers and fitting to the 
center of the data. Since you don’t have
a super duper clock on your motherboard, you are fitting both the randomness of 
the clock and the GPS. The
answer is to go slow and look at data over a lot of samples. 

The other answer to all this is to use a GPS with a PPS out. Feed that into 
some sort of capture process and 
go from there. The result is likely to improve things by at least a couple 
orders of magnitude. 

Bob

> On Mar 20, 2017, at 5:00 PM, Trent Piepho  wrote:
> 
> Hello time nuts,
> 
> I'm working on a custom embedded Linux device, with a custom inertial 
> reference unit, which contains a GPS module.   The module is a Telit JN3, 
> which is based on the SiRFSTAR IV I believe.  I'd like to use the GPS to sync 
> the Linux system clock.  Eventually I'd like to use the PPS signal, which is 
> routed to a FPGA that's part of the CPU, to implement a custom PPS hardware 
> module that I can write a kernel driver for and use the Linux hardpps system. 
>   And maybe make that feedback to the CPU's main clock source, since the FPGA 
> also controls that and could create a PLL between the TCXO that serves as the 
> master clock signal and the CPU's source clock.
> 
> But first things first.  I'm just grabbing the time from NMEA sentences.  And 
> there's quite a bit of jitter there!  Clearly using the first sentence output 
> by the GPS is critical.  I've tried to account for any time delays in the 
> software.  I think it's the GPS module that is creating the largest source of 
> jitter.  It appears to go in four hour cycles, peaking at 0:00Z, 4:00Z, 
> 8:00Z, etc.
> 
> Does this sound like something that one would expect with the NMEA output of 
> a non-timing GPS?  Is it related to satellite orbits?  Or perhaps is has 
> something to do with the design of the SiRFStar IV?
> 
> I'll attach a graph of what I'm seeing.  If the attachment doesn't come 
> though it's viewable at https://goo.gl/photos/JtYfJCpRSZb3hCnM8.
> 
> Methodology for the graph:
> System clock is left free running and not disciplined, after an initial one 
> time set based on the GPS time.
> On each NMEA GGA sentence, sent at 1 Hz, the system clock's offset from the 
> NMEA timestamp is measured.
> Each minute, the mean, std.dev, min and max are found for the last 60 offset 
> samples.  This is plotted on the graph.
> Any outlier samples, defined as more than 3 sigma from the previous mean, are 
> also plotted.
> Concurrently, the chrony NTP daemon is running and monitoring the IT dept's 
> NTP server, but NOT being used to set the local system clock.
> Once a minute, the system clock's offset to chrony's idea of the NTP server's 
> clock is also measured.  Chrony is using an algorithm based on median 
> filtering to get its idea of the NTP server's clock.
> The NTP server is just a windows domain controller synced to the internet NTP 
> pool and far from a precision source.
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Re: [time-nuts] Four hour cycle in GPS NMEA jitter

[Chris Albertson]

> Does this sound like something that one would expect with the NMEA output of 
> a non-timing GPS?  Is it related to satellite orbits?  Or perhaps is has 
> something to do with the design of the SiRFStar IV?
>

Remember the phone based time service? "At the tome time time will be
 BEEP"  With a GPS the NEMA sentence take the place of the spoken
words on the phone.   The NEMA specification allows the sentences to
up to one second "off".   That said most GPS receivers do MUCH better
than the NEMA spec but you should never count on non-specified
performance in a professional design.   The PPS is of course doing the
job of the BEEP on the old phone system.  Set you watch based on the
beep, not NEMA.

If you have an FPGA available then you could significantly improve
system time keeping.   Currently the PPS interrupts the CPU to
snapshot internal counter.   Unpredictable interrupt latency lifts NTP
timekeeping to about 1 or 2 microseconds but is the counter snap
shooting could be moved out to FPGA hardware there would be no unknown
latency and you could get NTP to break a "magic" 1uS barrier.   I've
only hear of 1 uS being broken with hardware.You would actually
not ned to write much software to make this happen, just move the
counter outside the CPU to the FPGA and you about have it.


Chris Albertson
Redondo Beach, California
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Re: [time-nuts] WTB: GPSDO

[jimlux]

On 3/20/17 2:26 PM, Mark Spencer wrote:

Hi:

Bob's comment about adjusting an oscillator from time to time aligns well with my limited 
experience in the time nuts hobby.Once I realized that in practice my better OCXO's 
were typically more than stable enough for my intended uses things became much simpler.   
I also realized that I could utilize my collection of time interval counters to compare 
my chosen reference to other references (including a GPSDO) while also comparing the 
chosen reference to the "Device Under Test."  I realize this isn't likely an 
approach that a commercial lab would use but for my hobby use it seems to work ok for me.

I've more or less shelved my plans to discipline one of my high end OCXO's via 
a home brew GPSDO scheme.



You already have a home brew GPSDO.. YOU are the control loop and the 
screwdriver is the actuator.



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Re: [time-nuts] WTB: GPSDO

[Bob Camp]

Hi

A good OCXO run continuously should get down to < 0.1 ppb / week. Doing a tweak 
every Saturday is likely enough to keep it in that range. The *big* advantage 
is that you
have the ADEV of the OCXO without any scruffy stuff from the control loop 
getting in the 
way. If your objective is to run something like a frequency counter, you 
probably are better
off with the trimmed OCXO.

Bob

> On Mar 20, 2017, at 5:26 PM, Mark Spencer  wrote:
> 
> Hi:
> 
> Bob's comment about adjusting an oscillator from time to time aligns well 
> with my limited experience in the time nuts hobby.Once I realized that in 
> practice my better OCXO's were typically more than stable enough for my 
> intended uses things became much simpler.   I also realized that I could 
> utilize my collection of time interval counters to compare my chosen 
> reference to other references (including a GPSDO) while also comparing the 
> chosen reference to the "Device Under Test."  I realize this isn't likely an 
> approach that a commercial lab would use but for my hobby use it seems to 
> work ok for me.
> 
> I've more or less shelved my plans to discipline one of my high end OCXO's 
> via a home brew GPSDO scheme.
> 
> Mark Spencer
> 
> 
>> On Mar 14, 2017, at 5:24 PM, Bob Camp  wrote:
>> 
>> Hi
>> 
>> 
>>> On Mar 14, 2017, at 6:33 PM, Tim Lister  wrote:
>>> 
>>> On Fri, Mar 10, 2017 at 2:35 PM, Chris Albertson
>>>  wrote:
 A GPSDO is not hard to make.  All you need is some way to compare the
 phase of two signals, an XOR gate can do that.  Then a small $2
 process moves the control voltage on the crystal.I tried one to
 build the simplest GPSDO that could still work.   Got the parts count
 down to about four or five and the cost well under $10 plus the OXO
 which was about $20.  The simplest dumb one I could make keeps about
 e-10.  Not great but enough for many uses.   I compared to my
 Thunderbolt and I could see the phase advance and retreat.  Just a
 little most sophistication and I likely could do much better but my
 goal was to prove to myself that a GPSDO could be build VERY simply
 with cheap parts
>>> 
>>> Hi Chris, that's good news that a GPSDO is that easy to make (at least
>>> a basic one) as that is exactly my medium term plan !
>> 
>> Actually it’s much easier. Just put a DVM on the XOR once a week and 
>> adjust your oscillator with a screwdriver. It saves *lots* of time and money.
>> 
>> Bob
>> 
>> 
>>> The issue of
>>> course is having something to test the newly built GPSDO against... I
>>> got one of the rehoused Trimble UCCM-based GPSDOs off ebay a while ago
>>> but haven't been super happy with it. It's quite a bit less sensitive
>>> than more modern GPS receivers and it often struggles to get even 1
>>> satellite with the indoor patch antenna. At one point both red alarm
>>> LEDs came on and stayed on despite power cycles - I eventually fixed
>>> that by taking it apart and finding and hitting a reset button on the
>>> board. Currently although I can talk to the unit over serial and it
>>> seems to respond, Lady Heather is not seeing any output from it.
>>> 
>>> Combined these things don't give me a great deal of confidence that
>>> this unit will act as a stable master reference. I was wondering if a
>>> second GPSDO like Russ linked to would work better (I have a ublox
>>> LEA-6T GPS already which I plan to use as the basis of the homebuilt
>>> GPSDO and it consistently sees many more satellites than the UCCM
>>> with a similar indoor antenna)  or put the money to getting an outdoor
>>> antenna mounted (don't feel happy drilling holes in the house myself)
>>> by someone. Do 2 GPSDOs tell you much more or just that each is
>>> different and you need a third to adjudicate ? (I can see a slippery
>>> slope looming from here...)
>>> 
>>> Cheers,
>>> Tim
>>> ___
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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>> 
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Re: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[Jim Harman]

On Mon, Mar 20, 2017 at 4:14 PM, Mark Sims  wrote:

> $3 for an  Arduino chip on a PCB with proto area from China (should have
> bought a lot more when they were available),$10 for a small ovenized 5V
> TTL output OCXO (also should have bought a lot more),  and $5 for misc
> parts (OK, beer money not included in the BOM).   Batteries not needed,
> powered off USB.


Hi Mark,

Did you use the Arduino's PWM output plus a LPF for the DAC, or a separate
DAC? If PWM, did you have problems with noise or sensitivity to the
USB-provided supply voltage?

Also I have found that not all computer USB ports can supply enough warm-up
current for a 5V OCXO. Or did you use a hefty USB charger and miss out on
the ability to get logging info back over the USB port?




-- 

--Jim Harman
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[time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[William H. Fite]

Attilla,

You are talking about product design, development and optimization, not the
production of a one-off for home use. Since performance standards are
already well established, it is only necessary for the developer to test
the bench built instrument against published standards and determine if
performance is good enough to suit him. Given a sound understanding of the
role of various components in the system, it will be a great deal faster
and easier for the builder to tinker with the one-off then to go through an
extensive process of model development and verification.

I have spent a good deal of my career doing performance modeling,
verification, and validation in collaboration with other scientists and
also engineers. You describe the process correctly but I think it is
generous overkill for the topic under discussion here. Or have I missed
something in the discussion? Is the desired end result a device for
manufacture and sale? If so, then your approach is right on target.

Bill


On Monday, March 20, 2017, Attila Kinali > wrote:

> On Thu, 16 Mar 2017 00:06:49 -0700
> Chris Albertson  wrote:
>
> > I actually did use your method.  I have a Rb and Thunderbolt, a pair
> > of freq. counters and so on.But still I wanted to see if I could
> > build from scratch and verify proper operation and keep the budget
> > under say $50 for everything from antenna to power cord. I think
> > it can be done but one can only verify longer term stability.
>
> Hmm.. doing verification of self-built (or aquired) equipment from
> scratch is a different game altogether. If you want to build things
> yourself, you first have to form a model of what disturbs your system,
> measure these parameters and verify the model against your measurements.
> Then you start building systems that exhibit different distortions,
> model these, measure and verify them. After you have built enough
> systems with different environmental characteristics, you verify
> them against eachother to make sure that your models faithully
> model reality and contain all parameters up to the error bound of the
> model.
>
> After a couple of decades of building and verification, you can be
> reasonably sure your GPSDO works correctly ;-)
>
>
> > (Yes you were correct a GOOD oversized XO is not sensitive to the
> > environment.  But notice the above budget.)
>
> 50$ for a complete GPSDO, batteries included, is quite a low price limit.
> A decent OCXO already costs 20-30$ on ebay. 100-200$ is a more realistic
> limit for a homebrew GPSDO with time-nuts like performance.
> A non-ovenized XO will not come close to time-nuts standards ;-)
>
>
> Attila Kinali
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>  -- Miss Matheson, The Diamond Age, Neil Stephenson
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> ailman/listinfo/time-nuts
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>


-- 
William H Fite, PhD
Independent Consultant
Statistical Analysis & Research Methods
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Re: [time-nuts] WTB: GPSDO

[Mark Spencer]

Hi:

Bob's comment about adjusting an oscillator from time to time aligns well with 
my limited experience in the time nuts hobby.Once I realized that in 
practice my better OCXO's were typically more than stable enough for my 
intended uses things became much simpler.   I also realized that I could 
utilize my collection of time interval counters to compare my chosen reference 
to other references (including a GPSDO) while also comparing the chosen 
reference to the "Device Under Test."  I realize this isn't likely an approach 
that a commercial lab would use but for my hobby use it seems to work ok for me.

I've more or less shelved my plans to discipline one of my high end OCXO's via 
a home brew GPSDO scheme.

Mark Spencer


> On Mar 14, 2017, at 5:24 PM, Bob Camp  wrote:
> 
> Hi
> 
> 
>> On Mar 14, 2017, at 6:33 PM, Tim Lister  wrote:
>> 
>> On Fri, Mar 10, 2017 at 2:35 PM, Chris Albertson
>>  wrote:
>>> A GPSDO is not hard to make.  All you need is some way to compare the
>>> phase of two signals, an XOR gate can do that.  Then a small $2
>>> process moves the control voltage on the crystal.I tried one to
>>> build the simplest GPSDO that could still work.   Got the parts count
>>> down to about four or five and the cost well under $10 plus the OXO
>>> which was about $20.  The simplest dumb one I could make keeps about
>>> e-10.  Not great but enough for many uses.   I compared to my
>>> Thunderbolt and I could see the phase advance and retreat.  Just a
>>> little most sophistication and I likely could do much better but my
>>> goal was to prove to myself that a GPSDO could be build VERY simply
>>> with cheap parts
>> 
>> Hi Chris, that's good news that a GPSDO is that easy to make (at least
>> a basic one) as that is exactly my medium term plan !
> 
> Actually it’s much easier. Just put a DVM on the XOR once a week and 
> adjust your oscillator with a screwdriver. It saves *lots* of time and money.
> 
> Bob
> 
> 
>> The issue of
>> course is having something to test the newly built GPSDO against... I
>> got one of the rehoused Trimble UCCM-based GPSDOs off ebay a while ago
>> but haven't been super happy with it. It's quite a bit less sensitive
>> than more modern GPS receivers and it often struggles to get even 1
>> satellite with the indoor patch antenna. At one point both red alarm
>> LEDs came on and stayed on despite power cycles - I eventually fixed
>> that by taking it apart and finding and hitting a reset button on the
>> board. Currently although I can talk to the unit over serial and it
>> seems to respond, Lady Heather is not seeing any output from it.
>> 
>> Combined these things don't give me a great deal of confidence that
>> this unit will act as a stable master reference. I was wondering if a
>> second GPSDO like Russ linked to would work better (I have a ublox
>> LEA-6T GPS already which I plan to use as the basis of the homebuilt
>> GPSDO and it consistently sees many more satellites than the UCCM
>> with a similar indoor antenna)  or put the money to getting an outdoor
>> antenna mounted (don't feel happy drilling holes in the house myself)
>> by someone. Do 2 GPSDOs tell you much more or just that each is
>> different and you need a third to adjudicate ? (I can see a slippery
>> slope looming from here...)
>> 
>> Cheers,
>> Tim
>> ___
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> 
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[time-nuts] Four hour cycle in GPS NMEA jitter

[Trent Piepho]

Hello time nuts,

I'm working on a custom embedded Linux device, with a custom inertial reference 
unit, which contains a GPS module.   The module is a Telit JN3, which is based 
on the SiRFSTAR IV I believe.  I'd like to use the GPS to sync the Linux system 
clock.  Eventually I'd like to use the PPS signal, which is routed to a FPGA 
that's part of the CPU, to implement a custom PPS hardware module that I can 
write a kernel driver for and use the Linux hardpps system.   And maybe make 
that feedback to the CPU's main clock source, since the FPGA also controls that 
and could create a PLL between the TCXO that serves as the master clock signal 
and the CPU's source clock.

But first things first.  I'm just grabbing the time from NMEA sentences.  And 
there's quite a bit of jitter there!  Clearly using the first sentence output 
by the GPS is critical.  I've tried to account for any time delays in the 
software.  I think it's the GPS module that is creating the largest source of 
jitter.  It appears to go in four hour cycles, peaking at 0:00Z, 4:00Z, 8:00Z, 
etc.

Does this sound like something that one would expect with the NMEA output of a 
non-timing GPS?  Is it related to satellite orbits?  Or perhaps is has 
something to do with the design of the SiRFStar IV?

I'll attach a graph of what I'm seeing.  If the attachment doesn't come though 
it's viewable at https://goo.gl/photos/JtYfJCpRSZb3hCnM8.

Methodology for the graph:
System clock is left free running and not disciplined, after an initial one 
time set based on the GPS time.
On each NMEA GGA sentence, sent at 1 Hz, the system clock's offset from the 
NMEA timestamp is measured.
Each minute, the mean, std.dev, min and max are found for the last 60 offset 
samples.  This is plotted on the graph.
Any outlier samples, defined as more than 3 sigma from the previous mean, are 
also plotted.
Concurrently, the chrony NTP daemon is running and monitoring the IT dept's NTP 
server, but NOT being used to set the local system clock.
Once a minute, the system clock's offset to chrony's idea of the NTP server's 
clock is also measured.  Chrony is using an algorithm based on median filtering 
to get its idea of the NTP server's clock.
The NTP server is just a windows domain controller synced to the internet NTP 
pool and far from a precision source.
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[time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[Mark Sims]

I did it for $25...  $7 for the GPS+antenna module,  $3 for an  Arduino chip on 
a PCB with proto area from China (should have bought a lot more when they were 
available),$10 for a small ovenized 5V TTL output OCXO (also should have 
bought a lot more),  and $5 for misc parts (OK, beer money not included in the 
BOM).   Batteries not needed, powered off USB.   It worked better than I 
expected... not Tbolt quality, but not too shabby for a thee-day weekend hack.  
   $50 (and a lot of work)  is certainly doable for a decent home-brew GPSDO.

---

> 50$ for a complete GPSDO, batteries included, is quite a low price limit.
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Re: [time-nuts] Optical Cesium or maybe Cesium "light"!

[paul swed]

Oh but thats what the marketing blurb even says.
It hit me later that the thing that runs out is still the same CS oven
Regards
Paul
WB8TSL

On Mon, Mar 20, 2017 at 3:09 PM, Attila Kinali  wrote:

> On Sat, 18 Mar 2017 19:25:28 +
> "Poul-Henning Kamp"  wrote:
>
> > >The A magnet being replaced by the A laser will for the same flow from
> > >the cesium oven produce twice as much atoms and thus improve signal to
> > >noise.
> >
> > It will generate more than twice the (usable) atoms, becuase the
> > straight path is (almost) insensitive to their velocity distribution,
> > whereas the corner-turning at the magnet is not.
>
> I am not sure if that holds true. The Ramsey cavity itself is
> velocity sensitive/selective. So not all velocities contribute
> the same to the resonance/peak. I do not know how much better/worse
> this selectivity compared to the bending magnets is, though.
>
> Attila Kinali
>
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>  -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[Bob Stewart]

I would say that the price for a home-built time-nuts quality GPSDO is going to 
be significantly greater than $200.  Yes, if you are making them for sale, 
eventually the unit cost will get down there.  But to build one single good 
GPSDO, you're going to throw away a lot of prototypes on the way to the one 
that works well enough to stand up to the scrutiny of this group.  The costs of 
those prototypes add up, and then there's your time engineering, building and 
testing.  It adds up to a lot.

Bob 




  From: Attila Kinali 
 To: Discussion of precise time and frequency measurement  
 Sent: Monday, March 20, 2017 2:01 PM
 Subject: [time-nuts] time-nuts equipment verification from scratch (was: WTB: 
GPSDO)
   
On Thu, 16 Mar 2017 00:06:49 -0700
Chris Albertson  wrote:

> I actually did use your method.  I have a Rb and Thunderbolt, a pair
> of freq. counters and so on.    But still I wanted to see if I could
> build from scratch and verify proper operation and keep the budget
> under say $50 for everything from antenna to power cord.    I think
> it can be done but one can only verify longer term stability.

Hmm.. doing verification of self-built (or aquired) equipment from
scratch is a different game altogether. If you want to build things
yourself, you first have to form a model of what disturbs your system,
measure these parameters and verify the model against your measurements.
Then you start building systems that exhibit different distortions,
model these, measure and verify them. After you have built enough
systems with different environmental characteristics, you verify
them against eachother to make sure that your models faithully
model reality and contain all parameters up to the error bound of the model.

After a couple of decades of building and verification, you can be 
reasonably sure your GPSDO works correctly ;-)


> (Yes you were correct a GOOD oversized XO is not sensitive to the
> environment.  But notice the above budget.)

50$ for a complete GPSDO, batteries included, is quite a low price limit.
A decent OCXO already costs 20-30$ on ebay. 100-200$ is a more realistic
limit for a homebrew GPSDO with time-nuts like performance.
A non-ovenized XO will not come close to time-nuts standards ;-)


                Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Optical Cesium or maybe Cesium "light"!

[Attila Kinali]

On Sat, 18 Mar 2017 19:25:28 +
"Poul-Henning Kamp"  wrote:

> >The A magnet being replaced by the A laser will for the same flow from 
> >the cesium oven produce twice as much atoms and thus improve signal to 
> >noise.
> 
> It will generate more than twice the (usable) atoms, becuase the
> straight path is (almost) insensitive to their velocity distribution,
> whereas the corner-turning at the magnet is not.

I am not sure if that holds true. The Ramsey cavity itself is
velocity sensitive/selective. So not all velocities contribute
the same to the resonance/peak. I do not know how much better/worse
this selectivity compared to the bending magnets is, though.

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)

[Attila Kinali]

On Thu, 16 Mar 2017 00:06:49 -0700
Chris Albertson  wrote:

> I actually did use your method.  I have a Rb and Thunderbolt, a pair
> of freq. counters and so on.But still I wanted to see if I could
> build from scratch and verify proper operation and keep the budget
> under say $50 for everything from antenna to power cord. I think
> it can be done but one can only verify longer term stability.

Hmm.. doing verification of self-built (or aquired) equipment from
scratch is a different game altogether. If you want to build things
yourself, you first have to form a model of what disturbs your system,
measure these parameters and verify the model against your measurements.
Then you start building systems that exhibit different distortions,
model these, measure and verify them. After you have built enough
systems with different environmental characteristics, you verify
them against eachother to make sure that your models faithully
model reality and contain all parameters up to the error bound of the model.

After a couple of decades of building and verification, you can be 
reasonably sure your GPSDO works correctly ;-)


> (Yes you were correct a GOOD oversized XO is not sensitive to the
> environment.  But notice the above budget.)

50$ for a complete GPSDO, batteries included, is quite a low price limit.
A decent OCXO already costs 20-30$ on ebay. 100-200$ is a more realistic
limit for a homebrew GPSDO with time-nuts like performance.
A non-ovenized XO will not come close to time-nuts standards ;-)


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] ADEV query Timelab and TICc

[ed briggs]

The 1 PPS signal is derived from an 81 MHz clock (12 ns) on the GPS chip 
according to the  Skytraq manual.  So that would mean n * 12ns.

From: time-nuts-requ...@febo.com
Sent: ‎3/‎20/‎2017 9:00 AM
To: time-nuts@febo.com
Subject: time-nuts Digest, Vol 152, Issue 32

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Today's Topics:

   1. Re: ADEV query Timelab and TICC (Orin Eman)
   2. ADEV query Timelab and TICC (Mark Sims)
   3. Re: ADEV query Timelab and TICC (gandal...@aol.com)
   4. Re: ADEV query Timelab and TICC (Dave Martindale)


--

Message: 1
Date: Sun, 19 Mar 2017 22:09:57 -0700
From: Orin Eman 
To: Tom Van Baak ,  Discussion of precise time and
frequency measurement 
Subject: Re: [time-nuts] ADEV query Timelab and TICC
Message-ID:

Re: [time-nuts] ADEV query Timelab and TICC

[Tom Van Baak]

Luciano,

This should not happen with the hp 5065A or 5061B frequency standards. I'm glad 
you worked around it by using a TAPR divider, but let's see if we can figure 
out the actual problem.

One thing to know is that the 1PPS output level from the 5061 and 5065 is 
*HUGE*, even up to 10 volts. If you send this to most counters it will blow the 
inputs or cause other undesirable side-effects, like the bouncing and spikes 
that you speak of. So always check your output and input signal levels and 
waveforms using a 'scope. Do this in-circuit, with all cables attached. Use 
attenuators and termination as appropriate for your counter's input specs. Set 
your DC trigger level to best match the actual waveform seen by the counter 
(not the waveform sent by the frequency standard).

Yes, the usual way you find out about this is that your ADEV measurements don't 
look right. The good news is that you can often tell within seconds that 
something is wrong. It's almost always a signal conditioning or trigger level 
issue, not a flaw in the instrument itself.

The TAPR dividers tend not to have "this problem" because they output at wimpy 
TTL/CMOS levels.

Older equipment can have powerful outputs. 10V into 50R is, what, 1/5th of an 
amp? Logarithmically, that puts a 5061A 1PPS closer to an automobile starter 
motor or heart defibrillator compared to modern logic gates.

/tvb


- Original Message - 
From: "timeok" 
To: 
Sent: Monday, March 20, 2017 12:56 AM
Subject: Re: [time-nuts] ADEV query Timelab and TICC


> 
>   All,
>   the similar problem I have verified using the HP5065A and HP5061B 1PPS 
> output, the dividers are pratically unusable for ADEV measurements. The 
> 5/10MHz output of the same instruments using the TAPR divider are ok, so 
> these dividers have some spike noise problems. It can be seen even using 
> other TIC as The HP53132A.
>   Luciano
>   www.timeok.it
> 
> 
>   Da "time-nuts" time-nuts-boun...@febo.com
>   A "Discussion of precise time and frequency measurement" time-nuts@febo.com
>   Cc
>   Data Sun, 19 Mar 2017 20:03:29 -0700
>   Oggetto Re: [time-nuts] ADEV query Timelab and TICC
>   > I have sent a couple of files to Tom. They were taken simultaneously from
>   > an LTE Lite - one from the PPS and one from a PicDiv dividing the 10MHz to
>   > 1Hz. The glitches were on the PPS trace, but not on the PicDiv trace, so
>   > I'm fairly confident the TICC was working correctly.
>   >
>   > Orin.
> 
>   Hi Orin,
> 
>   Thanks for the raw data. It's very nice (2 hours 16 minutes = 8219 points). 
> Everything looks fine with the exception of 8 glitches. These are sometimes 
> obvious jumps in phase, which cause massive spikes in frequency. Two plots 
> attached.
> 
>   Almost every data point is within a few ns of each other. This is good. The 
> standard deviation is a fraction of 1 ns. But once in a while there is a 
> relatively massive phase jump. This is bad. Interestingly these 8 phase jumps 
> all appear to be about 25 ns or a multiple of 25 ns in magnitude. The full 
> list is (ns units):
> 
>   24.575
>   24.724
>   24.831
>   25.047
>   25.087
>   25.549
>   25.589
>   49.623
> 
>   25 * N ns is not random. So I think this is not a Windows problem, not a 
> USB problem, not a TimeLab problem, not a TICC problem either.
> 
>   It makes me wonder if this is a LTE-Lite problem. If Said or Keith from 
> Jackson Labs is around -- is there anything on the LTE-Lite board that's 
> close to 20 or 40 or 80 MHz? At this point I kind of trust Orin's data and I 
> kind of trust the TICC. So when I see monster 25 ns phase jumps it makes me 
> think there's a problem with the GSPDO board itself.
> 
>   (Please realize that only on time-nuts may we can use the words "monster" 
> and "25 ns" in the same sentence; the rest of the world has larger problems)
> 
>   /tvb

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[time-nuts] ADEV query Timelab and TICC

[Mark Sims]

That doesn't make much sense if you are using the PICDIV properly... the TAPR 
dividers use the PICDIV chip to do the dividing.  The only difference between 
using a TAPR divider and a bare PICDIV is that the TAPR dividers have an input 
squarer circuit and output buffer.   If you are feeding the PICDIV with a clean 
TTL level input (and decent power) and the output from the PICDIV is not being 
abused/overloaded/improperly terminated the results should be the same.

---
>   the similar problem I have verified using the HP5065A and HP5061B 1PPS 
> output, the dividers are pratically unusable for ADEV measurements. The 
> 5/10MHz output of the same instruments using the TAPR divider are ok, so 
> these dividers have some spike noise problems. It can be seen even using 
> other TIC as The HP53132A.
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Re: [time-nuts] ADEV query Timelab and TICC

[John Ackermann N8UR]

I noticed with the TICC that the very high peak voltage on the 5061, 5065, etc. 
PPS causes trigger errors.  Putting a 50 ohm load at the TICC channel input 
helped a lot, or an attenuator might even be better.

These HP units have a very short pulse width that peaks at something like 20v 
into a high impedance.  It doesn't​ seem to hurt the TICC input circuit, but 
causes ringing that results in perceived jitter.  Knocking that down to TTL 
level solves the problem.

On Mar 20, 2017, 12:01 PM, at 12:01 PM, timeok  wrote:
>
>   All,
>the similar problem I have verified using the HP5065A and HP5061B 1PPS
>output, the dividers are pratically unusable for ADEV measurements. The
>5/10MHz output of the same instruments using the TAPR divider are ok,
>so these dividers have some spike noise problems. It can be seen even
>using other TIC as The HP53132A.
>   Luciano
>   www.timeok.it
>
>
>   Da "time-nuts" time-nuts-boun...@febo.com
>A "Discussion of precise time and frequency measurement"
>time-nuts@febo.com
>   Cc
>   Data Sun, 19 Mar 2017 20:03:29 -0700
>   Oggetto Re: [time-nuts] ADEV query Timelab and TICC
>> I have sent a couple of files to Tom. They were taken simultaneously
>from
>> an LTE Lite - one from the PPS and one from a PicDiv dividing the
>10MHz to
>> 1Hz. The glitches were on the PPS trace, but not on the PicDiv trace,
>so
>   > I'm fairly confident the TICC was working correctly.
>   >
>   > Orin.
>
>   Hi Orin,
>
>Thanks for the raw data. It's very nice (2 hours 16 minutes = 8219
>points). Everything looks fine with the exception of 8 glitches. These
>are sometimes obvious jumps in phase, which cause massive spikes in
>frequency. Two plots attached.
>
>Almost every data point is within a few ns of each other. This is good.
>The standard deviation is a fraction of 1 ns. But once in a while there
>is a relatively massive phase jump. This is bad. Interestingly these 8
>phase jumps all appear to be about 25 ns or a multiple of 25 ns in
>magnitude. The full list is (ns units):
>
>   24.575
>   24.724
>   24.831
>   25.047
>   25.087
>   25.549
>   25.589
>   49.623
>
>25 * N ns is not random. So I think this is not a Windows problem, not
>a USB problem, not a TimeLab problem, not a TICC problem either.
>
>It makes me wonder if this is a LTE-Lite problem. If Said or Keith from
>Jackson Labs is around -- is there anything on the LTE-Lite board
>that's close to 20 or 40 or 80 MHz? At this point I kind of trust
>Orin's data and I kind of trust the TICC. So when I see monster 25 ns
>phase jumps it makes me think there's a problem with the GSPDO board
>itself.
>
>(Please realize that only on time-nuts may we can use the words
>"monster" and "25 ns" in the same sentence; the rest of the world has
>larger problems)
>
>   /tvb
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Re: [time-nuts] MAINTENANCE OF HP 5071A PRIMARY FREQUENCY STANDARDS USNO

[Tom Van Baak]

> blockquote {padding-left: 1ex; margin: 0px 0px 0px 0.8ex; border-left: 
> #cc 1px solid;} p {margin: 0px;padding: 0px;} 
> Hello,
> I'm looking for good quality copy of this paper (especially plots):
> 
> 
> http://tycho.usno.navy.mil/ptti/1997papers/Vol%2029_06.pdf
> 
> 
> SD

Hi Slawek,

Welcome!  (please turn off html when you post to time-nuts)

> I'm looking for good quality copy of this paper (especially plots):
> http://tycho.usno.navy.mil/ptti/1997papers/Vol%2029_06.pdf

The text is very readable but I agree the plots are not.
If I have the hardcopy from the 1997 conference, I will scan the graphs for you.

/tvb

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Re: [time-nuts] ADEV query Timelab and TICC

[timeok]

   All,
   the similar problem I have verified using the HP5065A and HP5061B 1PPS 
output, the dividers are pratically unusable for ADEV measurements. The 5/10MHz 
output of the same instruments using the TAPR divider are ok, so these dividers 
have some spike noise problems. It can be seen even using other TIC as The 
HP53132A.
   Luciano
   www.timeok.it


   Da "time-nuts" time-nuts-boun...@febo.com
   A "Discussion of precise time and frequency measurement" time-nuts@febo.com
   Cc
   Data Sun, 19 Mar 2017 20:03:29 -0700
   Oggetto Re: [time-nuts] ADEV query Timelab and TICC
   > I have sent a couple of files to Tom. They were taken simultaneously from
   > an LTE Lite - one from the PPS and one from a PicDiv dividing the 10MHz to
   > 1Hz. The glitches were on the PPS trace, but not on the PicDiv trace, so
   > I'm fairly confident the TICC was working correctly.
   >
   > Orin.

   Hi Orin,

   Thanks for the raw data. It's very nice (2 hours 16 minutes = 8219 points). 
Everything looks fine with the exception of 8 glitches. These are sometimes 
obvious jumps in phase, which cause massive spikes in frequency. Two plots 
attached.

   Almost every data point is within a few ns of each other. This is good. The 
standard deviation is a fraction of 1 ns. But once in a while there is a 
relatively massive phase jump. This is bad. Interestingly these 8 phase jumps 
all appear to be about 25 ns or a multiple of 25 ns in magnitude. The full list 
is (ns units):

   24.575
   24.724
   24.831
   25.047
   25.087
   25.549
   25.589
   49.623

   25 * N ns is not random. So I think this is not a Windows problem, not a USB 
problem, not a TimeLab problem, not a TICC problem either.

   It makes me wonder if this is a LTE-Lite problem. If Said or Keith from 
Jackson Labs is around -- is there anything on the LTE-Lite board that's close 
to 20 or 40 or 80 MHz? At this point I kind of trust Orin's data and I kind of 
trust the TICC. So when I see monster 25 ns phase jumps it makes me think 
there's a problem with the GSPDO board itself.

   (Please realize that only on time-nuts may we can use the words "monster" 
and "25 ns" in the same sentence; the rest of the world has larger problems)

   /tvb
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[time-nuts] MAINTENANCE OF HP 5071A PRIMARY FREQUENCY STANDARDS USNO

[slawek dabrowski]

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Re: [time-nuts] ADEV query Timelab and TICC

[Dave Martindale]

The LTE-Lite User Manual (version 1.3) says:

2.3.7 1 PPS Module outputs
The LTE-Lite SMT Module provides GPS raw 1 PPS CMOS pulse on pin 15 with
sawtooth present, and a clean TCXO-generated, sawtooth-removed, UTC(GPS)
phase-locked 1PPS output on pin 4.

It is the pin 4 output that connects to the 1PPS-OUT jack on the eval
board.  So it is supposed to be cleanly divided down from the TCXO.  (But I
don't think Jackson Labs has published any of the circuitry on the LTE-Lite
module itself).

- Dave

On Mon, Mar 20, 2017 at 2:07 AM, Mark Sims  wrote:

>
> It is also interesting that the LTE GPSDO 1PPS has such a wide range of
> TIE.   A Tbolt / Z38xx GPSDO typically has a TIE in the 1PPS signal of
> around 1 nsec.   The LTE TIE spans over 40 nanoseconds (not including the
> spikes).  It seems like the LTE 1PPS may be from the GPS and not derived
> from dividing down the disciplined oscillator output.
> ___
>
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Re: [time-nuts] ADEV query Timelab and TICC

[GandalfG8--- via time-nuts]

Many thanks for the replies on this, what was initially intended as a quick 
 "Hello World" test seems to have become far more interesting:-)
 
I'll forward my results to Tom as requested and see where we go from  there.
 
Nigel
GM8PZR
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Re: [time-nuts] ADEV query Timelab and TICC

[Orin Eman]

On Sun, Mar 19, 2017 at 8:03 PM, Tom Van Baak  wrote:

>
> Thanks for the raw data. It's very nice (2 hours 16 minutes = 8219
> points). Everything looks fine with the exception of 8 glitches. These are
> sometimes obvious jumps in phase, which cause massive spikes in frequency.
> Two plots attached.
>


First, thanks to Tom for taking a look at these files.



> Almost every data point is within a few ns of each other. This is good.
> The standard deviation is a fraction of 1 ns. But once in a while there is
> a relatively massive phase jump. This is bad. Interestingly these 8 phase
> jumps all appear to be about 25 ns or a multiple of 25 ns in magnitude. The
> full list is (ns units):
>
> 24.575
> 24.724
> 24.831
> 25.047
> 25.087
> 25.549
> 25.589
> 49.623
>
> 25 * N ns is not random. So I think this is not a Windows problem, not a
> USB problem, not a TimeLab problem, not a TICC problem either.
>


Personally, I didn't think it was any of the the above either.  The PicDiv
trace showed no such glitches, so I was fairly confident that the TICC was
working well.  But just to verify that, I connected the LTE-Lite PPS to the
5370A and let it run for a few hours.  The 5370A captures similar
glitches.  I have sent the file on to Tom.

For entertainment value, I have attached the current Lady Heather
screenshot for the LTE-Lite.  It has little relationship to the .tim files
I sent to Tom since I generated those a few weeks ago.  FWIW, it shows an
off by two error writing some text, for example: "PDTDT".  This seems to
happen if you go to some other screen (I think it was help in this case)
then returning.

Orin.

[image: Inline image 3]
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[time-nuts] ADEV query Timelab and TICC

[Mark Sims]

Yes,  programs like Timelab and Stable32 are definitely the way to go for 
post-processing and analyzing your data in depth.   Lady Heather is more of a 
real-time monitoring and data acquisition program.   

The sensitivity of ADEV to data hiccups can be a good thing.  If your ADEV data 
goes to crap you know you have a problem and need to examine the data in more 
depth to find out why.   You can go in and remove / fixup the outliers to get a 
better understanding of the typical device performance  but leaving in the 
"zingers" tells you what the device is truly doing.

--

> And without preaching too much, this is why I recommend no one does 
> statistical work (e.g., ADEV) without first looking at the raw phase and 
> frequency data. A doubting Thomas attitude and the human eye are valuable 
> tools in science. Both Stable32 and TimeLab make it easy to display phase and 
> frequency, not just ADEV. This is not by accident.

Maybe we have hyped ADEV too much on this list. This rant is especially 
addressed at several LH and NTP authors who think analyzing clock data and 
making ADEV plots is just something you blindly code or script or automate, as 
if working with clock measurement data was as pure as mathematics.
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[time-nuts] ADEV query Timelab and TICC

[Mark Sims]

Orin sent me his data files and I ran them through Lady Heather.  Attached is a 
screen dump showing the Time Interval Error (TIE) plot of the 1PPS signal.  
This is the deviation of the 1PPS signal from the expected 1 second interval.   

Three of the bad points are flagged (1, 2, and 3 at the top of the plot area).  
 It is interesting that these discontinuities are not simple spikes in the 1PPS 
signal (a couple of his bad points are simple spikes) but are followed by a 
"recovery" period of 30 seconds to a minute.

It is also interesting that the LTE GPSDO 1PPS has such a wide range of TIE.   
A Tbolt / Z38xx GPSDO typically has a TIE in the 1PPS signal of around 1 nsec.  
 The LTE TIE spans over 40 nanoseconds (not including the spikes).  It seems 
like the LTE 1PPS may be from the GPS and not derived from dividing down the 
disciplined oscillator output.___
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