Re: [time-nuts] Something odd - ionosphere?

[Bob Stewart]

Thanks Graham,
That explains a lot.  I had never experienced blips that were this large before.
 Bob


  From: Graham <planoph...@aei.ca>
 To: time-nuts@febo.com 
 Sent: Sunday, January 8, 2017 4:17 PM
 Subject: Re: [time-nuts] Something odd - ionosphere?
   

*SOLAR WIND SURROUNDS EARTH:*For the fifth day in a row, Earth is 
surrounded by a fast-moving stream of solar wind flowing froma large 
hole 
<http://spaceweather.com/images2017/03jan17/ch_strip.png?PHPSESSID=qldvtt9u8qamt2b19ncupb86p2>in
 
the sun's atmosphere. NOAA forecasters say there is a 40% chance of 
G1-class geomagnetic storms on Jan. 8th asbright auroras 
<http://spaceweathergallery.com/aurora_gallery.htm>flicker around the 
Arctic Circle.

http://spaceweather.com/  for further details

cheers, Graham ve3gtc

On 2017-01-08 20:48, Bob Stewart wrote:
> This morning at about 0400 CST and again at more or less 0800CST, I noticed a 
> number of large phase excursions on one of the GPSDOs I'm testing.  It also 
> happened the day before but I didn't notice the time.  I am comparing the 
> 1PPS from two separate units on a 5370.  On the one unit I was logging, there 
> were 2 or three phase excursions of up to +/- 28ns or so at these times.  And 
> yet, the 5370 showed nothing out of the ordinary on the plot of the phase 
> difference between the two units.  So that tells me that it happened to both 
> GPSDOs.
>
> Did anyone else see anything odd in whatever units you're logging at around 
> this timeframe?  Was this likely caused by an ionospheric shift?
>
> Unfortunately, I didn't save the data for any of that, as I was only logging 
> one of the units.  Now I'm logging both units in question, as well as the 
> Timelab data, and of course it probably won't happen again.
> Bob
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] 1PPS users?

[Bob Stewart]

One thing I've never really understood is who actually uses the high-quality 
1PPS output from a GPSDO.  I have spent a lot of time, effort, and money on 
developing my GPSDO without a whole of thought to the user base.  It was just a 
quest for the best result I could obtain with a particular technology.  The 
frequency standard users was a no brainer.  Everyone who wants a frequency 
standard eventually understands they need to get a GPSDO, or an Rb, or a Cs.  
And that's all I thought I had: a good frequency standard.  And then Tom 
prodded me a bit and showed me the shortcomings of what I was doing, and I did 
something about it.  So, if an NTP user can get his time fix directly from a 
noisy receiver, who actually needs a time-accurate, low jitter 1PPS pulse?
Bob - AE6RV
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] 1PPS users?

[Bob Stewart]

Hi Jim,
Thanks Jim,

So, what I'm seeing so far, assuming I'm interpreting it correctly, is big 
budget commercial and government applications, generally clustering around 
time-controlled multiplexing, as well as the niche that is the space industry.  
Then there's the hobbyist, such as Eric who wants to control a Fedchenko clock, 
or similar type of application, such as whatever sort of spread spectrum that 
ham radio may morph into, or perhaps the low S/N EME guys.  Any others?
Bob

  From: jimlux <jim...@earthlink.net>
 To: time-nuts@febo.com 
 Sent: Sunday, December 18, 2016 6:56 PM
 Subject: Re: [time-nuts] 1PPS users?
   
On 12/18/16 3:16 PM, Bob Stewart wrote:
> One thing I've never really understood is who actually uses the high-quality 
> 1PPS output from a GPSDO.  I have spent a lot of time, effort, and money on 
> developing my GPSDO without a whole of thought to the user base.  It was just 
> a quest for the best result I could obtain with a particular technology.  The 
> frequency standard users was a no brainer.  Everyone who wants a frequency 
> standard eventually understands they need to get a GPSDO, or an Rb, or a Cs.  
> And that's all I thought I had: a good frequency standard.  And then Tom 
> prodded me a bit and showed me the shortcomings of what I was doing, and I 
> did something about it.  So, if an NTP user can get his time fix directly 
> from a noisy receiver, who actually needs a time-accurate, low jitter 1PPS 
> pulse?

Anyone who needs to trigger events at a precise time or log the 
occurrence of an event uses the 1 pps - the serial port (or other 
interface) gives you the "at the tone the time will be" message, and the 
edge of the 1pps is the "tone".


I've got several systems flying in space (or soon to fly in space) that 
use the 1pps from GPS to calibrate their internal clocks and/or to 
provide an absolute time reference (along with the aforesaid time message).

For example, one needs to have your carrier frequency within a certain 
tolerance for communications with the ground stations: you can either 
fly a precision oscillator with an oven (big, heavy, high power) or you 
can measure a not-so-precision oscillator (small, cheap, low power) 
against a 1pps, and adjust your frequency that way.

I grant you that this is really more like *building* a GPSDO than 
*using* a GPSDO.

I've used the 1pps from a GPSDO as a common trigger to synchronize 
timing and timestamping for separate systems.



___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] 1PPS users?

[Bob Stewart]

Hi Scott,
I do understand the reasons that these users want this quality of output.  It's 
who these users are, what fields, industries, etc, that I didn't quite 
understand.
Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Scott Stobbe <scott.j.sto...@gmail.com>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Sunday, December 18, 2016 8:22 PM
 Subject: Re: [time-nuts] 1PPS users?
   
Part of the reason 1PPS needs to be so clean is because you are continuously 
integrating phase noise of the LO (hopefully an OCXO). While 10 uS is pretty 
trivial off a gps receiver. Without gps, 10 us over 24 hrs with a plane jane 
AT-cut crystal subject environmental dynamics becomes ludicrous. More than 
likely the short term stability of GPSDO is cleaner than it needs to be for 
many applications, but that is so holdover over an hour or day remains 
reasonable.
On Sun, Dec 18, 2016 at 6:16 PM, Bob Stewart <b...@evoria.net> wrote:

One thing I've never really understood is who actually uses the high-quality 
1PPS output from a GPSDO.  I have spent a lot of time, effort, and money on 
developing my GPSDO without a whole of thought to the user base.  It was just a 
quest for the best result I could obtain with a particular technology.  The 
frequency standard users was a no brainer.  Everyone who wants a frequency 
standard eventually understands they need to get a GPSDO, or an Rb, or a Cs.  
And that's all I thought I had: a good frequency standard.  And then Tom 
prodded me a bit and showed me the shortcomings of what I was doing, and I did 
something about it.  So, if an NTP user can get his time fix directly from a 
noisy receiver, who actually needs a time-accurate, low jitter 1PPS pulse?
Bob - AE6RV
 - -- --
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
__ _
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts
and follow the instructions there.




   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] u-blox timing modules

[Bob Stewart]

Hi John,
Could you tell me why one would use choose an LEA-M8F over an LEA-M8T?
Bob - AE6RV
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: John Haine 
 To: time-nuts@febo.com 
 Sent: Wednesday, December 21, 2016 11:34 AM
 Subject: [time-nuts] u-blox timing modules
   
It's worth noting, in case people don't know, that u-blox have a 
specific chip & module (the latter being the LEA-M8F) for precision 
timing, developed for the LTE (4G) base station market. This disciplines 
a low phase noise 30.72 MHz reference to received satellite signals, 
GPS/GLONASS/BeiDou.  (30.72 MHz is the standard LTE sampling rate.)

John.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Timelab, GPIB-USB-B in a VM

[Bob Stewart]

I don't know how they're done in VMWare, but in VirtualBox, you have to setup 
the USB configuration for the VM before you start it.  You just click the 
machine, settings, then USB, then add a device, then select from what's 
available.  Which means you have to have it plugged in and enumerated first.

Bob 


  From: Bob Bownes 
 To: Discussion of precise time and frequency measurement  
 Sent: Monday, March 27, 2017 8:03 PM
 Subject: Re: [time-nuts] Timelab, GPIB-USB-B in a VM
   
John,

Thanks for the reply.

I'm obviously missing something as I can't see the GPIB-USB-B or the
ethernet connected GPIB-ENET.

It's really as simple as going to aquire->HP5371/5372 and the interfaces
should be in the list, correct?

Thanks,
Bob


On Mon, Mar 27, 2017 at 6:42 PM, John Miles  wrote:

> Try running the 32-bit version (timelab.exe) instead of timelab64.exe,
> even if the VM supports 64-bit execution.  That can sometimes help with
> compatibility.
>
> -- john, KE5FX
> Miles Design LLC
>
> > -Original Message-
> > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
> > Bownes
> > Sent: Monday, March 27, 2017 2:49 PM
> > To: Discussion of precise time and frequency measurement
> > Subject: [time-nuts] Timelab, GPIB-USB-B in a VM
> >
> > So I'm trying to run timelab in a windows 7 VM with a GPIB-USB-B
> interface.
> >
> > Anyone ever tried such a thing?
> >
> > The NI explorer sees the interface but nothing else does.
> >
> > Pointers welcome!
> >
> > Data on a bunch of oscillators as soon as I get it to work...:)
> >
> > Thanks,
> > Bob
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-
> > bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

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

[Bob Stewart]

These look a lot like the 25ns pops I was getting when I first started 
generating the 1PPS output from the PIC.  In my case, the PIC uses a PLL to 
multiply the external clock from 10MHz to 80MHz, which is then  divided to 
40MHz and used as an instruction clock.  This gave an occasional early or late 
pulse, which was off by 25ns.  I wound up fixing my problem by arranging it so 
that the timer used to generate the 1PPS was offset by 2 instructions  (so that 
the timer fired between two successive 100ns pulses from the OCXO) and then 
gating the generated pulse with the OCXO so that the OCXO was the thing 
generating the actual 1PPS output.  Of course, this could be something entirely 
different:  For example, the quantization error on the 1PPS from the GPSDO as 
Tom mentions.  But, in that case, it seems like there should be a lot more of 
them.
Bob 

  From: Tom Van Baak 
 To: Discussion of precise time and frequency measurement  
 Sent: Sunday, March 19, 2017 10:04 PM
 Subject: 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___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

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
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Timelab file wanted

[Bob Stewart]

Hi Guys,
Does anyone have a multi-day (at least 5 days) timelab file comparing the 1PPS 
from a GPSDO to a Cesium standard, with a run of the mill rooftop antenna using 
at least an HP 5370A quality TIC?  I'm running a 7 day test like this, and I'd 
like to have something to compare to.  If you have one, could you send me a 
copy off-list?

thanks,
Bob Stewart ---   bob at evoria dot net
 
-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Timelab file needed

[Bob Stewart]

Does anyone have a timelab file for a KS-24361?  My KS has a much worse 1s ADEV 
(and on down the line) than I would have expected, and I'd like to see what 
others are getting.
Bob

AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

It was mentioned that Timelab can do a three-cornered hat.  I can't find it.  
Is this something that can only be done with multiple Timepods connected, or is 
there an option that I'm missing?  Or is there some other tool that needs to be 
used?  For the record, I want to create the 3c-hat from data that was run at 
different times, and I understand (at least somewhat) the shortcomings of doing 
that.  But, it would be interesting to see what would result.  And, not having 
three 5370s in good condition, it's the best I can do.

Bob 

-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
OK, I give up.  Try as I might, I can't fudge things enough to make any sense.  
I did run a set of 1 hour tests that seemed to confirm what I can infer from 
the phase plots in timelab, but anything longer than that and the curves either 
contradict the phase plots, or there are large gaps in at least one trace, or a 
trace is even missing entirely.  Oh well.  I seem to remember reading that the 
3c-hat was only useful in comparing similar devices.  The KS just isn't close 
enough to what I'm trying to compare it to, I guess.

If you or anyone else has an ADEV plot of the KS against some local standard 
(for any length of time, any standard, even just a bare OCXO that is not a 
Trimble 34310-T) could you please share it with me?  I'm looking for relative 
peformance, not a definitive test.  Of course if you also have one of a 34310-T 
against the same standard, that would be great!

Bob 

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: John Miles <j...@miles.io>
 Sent: Thursday, April 13, 2017 7:19 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi

There are a number of papers from the 70’s and 80’s digging into three corner 
hat data. The net result often
would turn out to be “less than zero” noise on one of the DUT’s. Since that’s 
physically impossible the technique
got a bit of “attention”.  The Cliff Notes version of the results is that 
simultaneous measurements were the key
to getting decent results. The closer to “same time” (as in microseconds or 
nanoseconds) the better. Even with very careful 
data collection, odd things can still happen. Phase noise pops up at crazy low 
levels or ADEV goes to bizarre
numbers. In many ways a TimePod (or other ADC based setup) is ideal for getting 
the data synchronized. Running
all three devices on one is by far the best way I have seen to make the 
technique work. It still can have problems, 
but less so that other ways of doing it. 

Bob



> On Apr 13, 2017, at 7:16 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi John,
> I had a chance to think about this some more after I pressed the send key.  
> The ionospheric effects are certainly going to be different if the distance 
> in time between tests is large.  And, of course, there is the fact that the 
> KS has a pretty old receiver compared the Ublox I use, so that even the 
> reaction to the ionosphere is likely to be different.  So, I thought I'd 
> experiment with some runs with both GPSDOs in holdover to see if that would 
> even the score, so to speak.  Of course then I have the temperature variable, 
> so it's never going to be perfect.
> Anyway, thanks for the help.  If I get anything that seems useful out of 
> this, I'll post links to the data.
> Bob 
> 
>      From: John Miles <j...@miles.io>
> To: 'Discussion of precise time and frequency measurement' 
> <time-nuts@febo.com> 
> Sent: Thursday, April 13, 2017 6:01 PM
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
> 
> Longer runs would be better to the extent that they give you smaller error 
> bars in your tau range of interest, certainly.  But any effects that 
> influence one of your runs but not the others will render the 3-cornered hat 
> solution questionable, if not outright invalid.  Only through many repeated 
> runs can you learn to tell the bogus data from the good stuff.  So I'd make 
> shorter runs at first, until you're sure you know what you're looking at.
> 
> 
> 
> It doesn't matter which source is applied to the start versus stop channel, 
> as long as the assignments are consistent with the source labels you apply.  
> I would use frequency-count mode to simplify things, at least at first.  This 
> is already a very challenging measurement for all the reasons mentioned. 
> 
> 
> 
> -- john, KE5FX
> 
> Miles Design LLC
> 
> 
> 
> 
> 
> From: Bob Stewart [mailto:b...@evoria.net] 
> Sent: Thursday, April 13, 2017 8:41 AM
> To: Discussion of precise time and frequency measurement; John Miles
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
> 
> 
> 
> Hi John,
> 
> 
> 
> Thanks!  With lesser equipment, such as the 5370A, would longer runs be 
> better?  I used a set of 1 hr runs and the result wasn't quite what I had 
> expected.  However, it may be that I had mislabeled the files, and thus got 
> the sources confused.  Of course, it may be that the ionospheric effect was 
> grossly different between the three tests.  So, with a 5370, Source A would 
> be the START input and Source B would be the STOP input, right?  For my 
> testing, the sources are all 10MHz signals, and I'm driving the EXT input 
> with 1PPS from a GPSD

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
Oh, I had completely forgotten about the many runs you gifted us with back 
then.  Fortunately, I kept all of them in my email archive.  I can't compare 
like for like, of course, but I think I can work up something that compares at 
the larger taus where the 5370 doesn't dominate.
I'm going to run another long term test of my GFS unit against my PRS-45A.  The 
problem, the issue that made me ask for data is that everything from phase 
plots to ADEV plots of my unit are just so much better than the KS.  In 
addition, I don't see the large ionospheric swings on my GFS unit that you and 
Bruce and others have spoken about.  This bothers me a lot.  Could it be my 
location here in Houston?  Could it be the Ublox LEA-6T compared to the much 
older Motorola in the KS?

Bob 

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Monday, April 17, 2017 7:55 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi
The data I have on the KS boxes was posted to the list back when they were.a 
hot topic. I’m sure it is still in the archives.I’m guessing it’s not quite 
what you are after. 

The closer the devices are to each other the better the technique works. A 
simple way to look at it is as an attenuation. If it knocks noise down 10:1, 
the worst unit should be no more than 10X noise than the best unit. How much 
things are knockeddown is a function of the length of the runs compared to the 
longest tau. For a 10:1 ratio of tau to run, attenuation of noise by 10:1 is 
very optimistic. You usually  need something beyond 100:1 to get that sort of 
performance. A lot depends on the noise involved. Some types of behavior simply 
don’t work well with the technique. 
The KS box goes from “better than” to “worse than” and back to “better than” 
most atomic standards you would compare it to overa range of tau from 0.1 S to 
1,000,000 seconds. To get the 1,000,000 second data accurately, you would need 
a 100,000,000 secondrun. The simple answer there is that nobody has that kind 
of time or that reliable a setup. Even the three month run to get good100,000 
second data is a challenge. None of that relates to three corner hat stuff, 
it’s just the confidence bars on ADEV. It givesyou another (say) 100:1 wait on 
top of the three corner stuff. 
Now toss in the basics of GPS. Depending on the day, you will get <10 ns to  
>100 ns swing over a  24 hour period. Today may or may not be the same as 
tomorrow. That’s with a “perfect” L1 setup. The variation comes from the 
ionosphere and the fact thatthe GPS data does not allow you to fully correct 
for it.  In addition, you will get some interesting bumps related to 
constellations and your local antenna setup. Any GPSDO that is quartz based 
will happily follow the 24 hour swing in the GPS from the ionosphere. At 
100,000 seconds, a 100 ns swing is 1x10^-12. That’s a lot of disruption. It 
most certainly is not the sort of thing that ADEV expects to pop up in the 
middle of a run. 
The simple answer to all this is “don’t go there”. Three corner hat is fine for 
short term stuff. It’s a mess for long term runs. Getting datathat is good 
enough for a long term ADEV run out of a three corner setup is a major 
struggle. The time for the correlation to knock downthe noise on top of the 
time to get good ADEV data gets you into impractically long runs. 
Bob




On Apr 16, 2017, at 10:16 PM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
OK, I give up.  Try as I might, I can't fudge things enough to make any sense.  
I did run a set of 1 hour tests that seemed to confirm what I can infer from 
the phase plots in timelab, but anything longer than that and the curves either 
contradict the phase plots, or there are large gaps in at least one trace, or a 
trace is even missing entirely.  Oh well.  I seem to remember reading that the 
3c-hat was only useful in comparing similar devices.  The KS just isn't close 
enough to what I'm trying to compare it to, I guess.

If you or anyone else has an ADEV plot of the KS against some local standard 
(for any length of time, any standard, even just a bare OCXO that is not a 
Trimble 34310-T) could you please share it with me?  I'm looking for relative 
peformance, not a definitive test.  Of course if you also have one of a 34310-T 
against the same standard, that would be great!

Bob 

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: John Miles <j...@miles.io>
 Sent: Thursday, April 13, 2017 7:19 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi

There are a number of papers from the 70’s and 80’s digging into three corner 
hat data. The net result often
would turn out to be “less than zero” noise on one of the DUT’s. Since that’s 
physically impossi

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi John,
I had a chance to think about this some more after I pressed the send key.  The 
ionospheric effects are certainly going to be different if the distance in time 
between tests is large.  And, of course, there is the fact that the KS has a 
pretty old receiver compared the Ublox I use, so that even the reaction to the 
ionosphere is likely to be different.  So, I thought I'd experiment with some 
runs with both GPSDOs in holdover to see if that would even the score, so to 
speak.  Of course then I have the temperature variable, so it's never going to 
be perfect.
Anyway, thanks for the help.  If I get anything that seems useful out of this, 
I'll post links to the data.
Bob 

  From: John Miles <j...@miles.io>
 To: 'Discussion of precise time and frequency measurement' 
<time-nuts@febo.com> 
 Sent: Thursday, April 13, 2017 6:01 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Longer runs would be better to the extent that they give you smaller error bars 
in your tau range of interest, certainly.  But any effects that influence one 
of your runs but not the others will render the 3-cornered hat solution 
questionable, if not outright invalid.  Only through many repeated runs can you 
learn to tell the bogus data from the good stuff.  So I'd make shorter runs at 
first, until you're sure you know what you're looking at.

 

It doesn't matter which source is applied to the start versus stop channel, as 
long as the assignments are consistent with the source labels you apply.  I 
would use frequency-count mode to simplify things, at least at first.  This is 
already a very challenging measurement for all the reasons mentioned. 

 

-- john, KE5FX

Miles Design LLC

 

 

From: Bob Stewart [mailto:b...@evoria.net] 
Sent: Thursday, April 13, 2017 8:41 AM
To: Discussion of precise time and frequency measurement; John Miles
Subject: Re: [time-nuts] Three-cornered hat on timelab?

 

Hi John,

 

Thanks!  With lesser equipment, such as the 5370A, would longer runs be better? 
 I used a set of 1 hr runs and the result wasn't quite what I had expected.  
However, it may be that I had mislabeled the files, and thus got the sources 
confused.  Of course, it may be that the ionospheric effect was grossly 
different between the three tests.  So, with a 5370, Source A would be the 
START input and Source B would be the STOP input, right?  For my testing, the 
sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a 
GPSDO.



 

Bob 

___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi John,
Thanks!  With lesser equipment, such as the 5370A, would longer runs be better? 
 I used a set of 1 hr runs and the result wasn't quite what I had expected.  
However, it may be that I had mislabeled the files, and thus got the sources 
confused.  Of course, it may be that the ionospheric effect was grossly 
different between the three tests.  So, with a 5370, Source A would be the 
START input and Source B would be the STOP input, right?  For my testing, the 
sources are all 10MHz signals, and I'm driving the EXT input with 1PPS from a 
GPSDO.

Bob 


  From: John Miles 
 To: 'Discussion of precise time and frequency measurement' 
 
 Sent: Thursday, April 13, 2017 1:07 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
> It was mentioned that Timelab can do a three-cornered hat.  I can't find it.  
> Is
> this something that can only be done with multiple Timepods connected, or
> is there an option that I'm missing?  Or is there some other tool that needs
> to be used?  For the record, I want to create the 3c-hat from data that was
> run at different times, and I understand (at least somewhat) the
> shortcomings of doing that.  But, it would be interesting to see what would
> result.  And, not having three 5370s in good condition, it's the best I can 
> do.

Hi, Bob --

N-cornered hat measurement is a beta feature, not in the docs yet.  A single 
TimePod can generate the required three plots simultaneously, but you can use 
individual plots from TICs and frequency counters as long as you start with 
highly-reproducible measurements and are careful with your interpretation of 
the results.  If your setup returns inconsistent results from one run to the 
next, then any attempt at a separated-variance plot will be GIGO.

You can see some examples at http://www.ke5fx.com/gpscomp.htm .  Various 
finicky conditions need to be met before the 3-cornered hat display will become 
available; check out 
https://www.febo.com/pipermail/time-nuts/2015-September/094039.html for some 
tips.  

-- john, KE5FX
Miles Design LLC


___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Magnus,
Today I started a long run against my PRS-45A.  Maybe this time I won't have a 
power outage.  I'll see what it tells me in a few days.
Bob 

  From: Magnus Danielson <mag...@rubidium.dyndns.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: mag...@rubidium.se
 Sent: Monday, April 17, 2017 5:28 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Bob,

First of all, there is a first degree of compensation from the GPS 
transmitted Klobuchar ionspheric model. There is a limit to how well 
those would match the actual values at the time and behavior for your 
spot on the globe. The GPS models this to a fair fit for the globe.
Use of WAAS/EGNOS or even DGPS would allow for a better correction.

Second, these changes is slow, so you better measure them compared to a 
cesium or maybe rubidium rather than the GPS itself or another GPS. A 
GPS tracks in these deviations, so it will only be visible when compared 
to an independent source. The frequency error and drift of the reference 
clock can be compensated, but the remainder will dominantly be remaining 
delay variations.

You can fair better if you have a double-frequency GPS setup, as it can 
first-degree measure and compensate the ionospheric shifts, which allows 
for a benefit over L1 CA only receiver.

Cheers,
Magnus

On 04/17/2017 10:38 PM, Bob Stewart wrote:
> Hi Tom,
> The reason I express so much confusion over this is because I don't see the 
> wild phase excursions on my GFS units that people insist will happen due to 
> ionospheric effects.  Is this because they are rare events, and I just 
> haven't been saving data during a bad time?  I notice in your example page, 
> you aren't seeing them, either during your 8+ day capture of the Tbolt.
>
> Bob
>
>
>      From: Tom Van Baak <t...@leapsecond.com>
>  To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
>  Sent: Monday, April 17, 2017 3:05 PM
>  Subject: Re: [time-nuts] Three-cornered hat on timelab?
>
> Bob S,
>
> Here's an example of a one week GPSDO run:
>
> http://leapsecond.com/pages/tbolt-8d/
>
> IIRC, this was a default, untuned, self-surveyed TBolt. You can see some 
> level of daily variations -- probably a mix of sky view, survey error, 
> ionosphere, multi-path, sidereal effects [1], temperature (antenna, cable, 
> GPSDO, reference), etc. It takes some time and equipment to sort out which is 
> which, but even a simple test like this can give you an upper bound.
>
> /tvb
>
> [1] Fun GPS orbit stuff here:
> http://leapsecond.com/pages/sidereal/index.htm
> http://leapsecond.com/pages/sidereal/14years.htm
> http://leapsecond.com/pages/sidereal/sv.htm
> http://leapsecond.com/pages/gps-orbit/
>
>
> - Original Message -
> From: "Bob Stewart" <b...@evoria.net>
> To: "Bob kb8tq" <kb...@n1k.org>; "Discussion of Precise Time and Frequency 
> Measurement" <time-nuts@febo.com>
> Sent: Monday, April 17, 2017 9:33 AM
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
>
>
> Hi Bob,
> OK, thanks. I've kicked off a 7 day run of a GFS against the PRS-45A. That 
> should be long enough to separate out the GFS from the PRS' drift direction 
> from the ionosphere.
>
> Bob
>
>
>
>      From: Bob kb8tq <kb...@n1k.org>
>  To: Bob Stewart <b...@evoria.net>
> Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
>  Sent: Monday, April 17, 2017 11:28 AM
>  Subject: Re: [time-nuts] Three-cornered hat on timelab?
>
> Hi
> The ionosphere is the culprit in terms of the daily swing. The swing is a 
> function of the goodness of fit between the GPS broadcast dataand the 
> ionosphere as it impacts the satellites you are using. There is no rime or 
> reason to it beyond that. If you get “lucky” things don’t move much. If you 
> live in exciting times, things move quite a bit. Unless you go to something 
> like an L1/L2 receiver, the GPS module you use has little to do with it 
> (unless it’s broke ….). Yes there are some fiddly little qualifiers relating 
> to being at the north or south pole and GPS coverage (along with space 
> weather impacts). Very few of us do our runs at either location :) Just for 
> reference, the area of concern also hasat least one day each year where the 
> sun sets for < 1 hours.
> Bob
>
>
>
>
> On Apr 17, 2017, at 11:33 AM, Bob Stewart <b...@evoria.net> wrote:
> Hi Bob,
> Oh, I had completely forgotten about the many runs you gifted us with back 
> then. Fortunately, I kept all of them in my email archive. I can't compare 
> like for like, of course, but I think I can work up something 

[time-nuts] Cs standard stability

[Bob Stewart]

I hooked up my PRS-45A yesterday, just to do some ADEV comparisons with my 
GPSDO.  Unfortunately, the GPSDO seems to be better by almost two points at all 
tau as measured on my HP 5370A and plotted by Timelab.  So, can I infer from 
that that the OCXO in the PRS has a problem, or could it be something as stupid 
as a bad cap?  Or do I just not understand the specs and the PRS isn't up to my 
expectations?  The PRS docs show the unit as 3E-11 at 1s tau, and I'm seeing 
about 4.25E-11 at 1s, so maybe it's the latter.

NOTE: The test setup for this is 1PPS from a well-aged GPSDO to the 5370's 
start input, and 10MHz from either a different GPSDO or the PRS to the stop 
input.

 As best as I can tell looking through the holes in the case (still running the 
tests), the PRS has an MTI 250-0827 5MHz OCXO.  I've got one of the Lucent KS 
units that I don't care much about, so maybe the MTI 260-0624 5MHz in that will 
work?  Both are 5MHz, but I don't know whether both are 12V at this point.  
And, of course, I don't know whether making the swap to an MTI 260 OXCO will 
benefit the PRS.
Any comments or educated speculations are welcomed.

Bob - AE6RV
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Cs standard stability

[Bob Stewart]

Hi Bruce,
To me, it seems that the reasoning must be circular.  If I measure three units 
against each other with one piece of test equipment, then the one that has the 
best noise performance is the one that is not being measured when the ADEV plot 
is the worst.  At least that's the way I see it.
I've attached a screenshot of the Timelab plot for the GPSDO and the Cs.  What 
I consider the reference plot for my GPSDO is here on page 2: 
http://ae6rv.com/GFS/Documents/Brochure.pdf .  Note that that link downloads a 
pdf file from my website.  The unit under test there was a pre-production unit. 
 However, nothing of substance changed to the hardware, other than a different 
OCXO.  That unit did not output a proper 1PPS.  The changes to the production 
units takes a 1PPS pulse generated in the PIC and gates that with the OCXO to 
generate a proper 1PPS signal.  The tests on the 5370 use one GPSDO to generate 
both the 1PPS reference and the 10MHz that clocks the 5370.  I don't see any 
particular difference in the results when a different GPSDO drives the tests.  
I do see a pretty noisy plot up to about 80s when using the 10811 in the 5370 
to drive the clock. "An inexpensive replacement for the 5370A/B with an rms 
measurement noise for short time intervals of around 10ps or better would 
probably be useful for such measurements."
What would such an "inexpensive" device be?  What's inexpensive for you would 
probably be way out of my reach.

Bob



  From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 4:28 PM
 Subject: Re: [time-nuts] Cs standard stability
   
Bob

Your reasoning appears somewhat circular.
A typical 5370A may have around 35ps or so rms noise when measuring short time 
intervals. This translates to an equivalent ADEV of around 4.3E-11 for Tau = 1s 
due to the 5370A noise alone. The 5370A in particular may have issues with DNL 
errors of the order of 100ps or so.

The actual noise of a particular 5370A depends on how well the 200MHz 
multiplier chain is aligned, whether a couple of changes to the original 
circuit were implemented and the noise of its 10MHz frequency reference. 

Your setup is probably too noisy to be confident that the PRS45A doesn't meet 
spec at Tau= 1s.

For Tau > 100s or so the noise level of your setup should be small enough that 
detection of deviations of the PRS -45A from its spec can be reliably detected. 

Attaching plots of your GPDSO ADEV and the performance of your particular 5370A 
would be helpful.

An inexpensive replacement for the 5370A/B with an rms measurement noise for 
short time intervals of around 10ps or better would probably be useful for such 
measurements.

Bruce
> On 05 March 2017 at 05:58 Bob Stewart <b...@evoria.net> wrote:
> 
> 
> Hi Bruce,
> I'm aware that the GPSDO is better at low tau than the 5370.  This is born 
> out by its low tau ADEV being right at the specs for the 5370, as well as by 
> measurements done some time ago on a Timepod.  Unfortunately, I don't have a 
> Timepod, so I have to make some guesses based on what I can see; limited as 
> that is by the 5370.  But, given that the GPSDO tests validate the 5370, when 
> I see an ADEV that is worse than the 5370's specs (i.e. worse than the result 
> of the GPSDO test), I take that as an indication that the additional noise is 
> from the DUT.  Of course, I don't know anything more than that.  Correct?
> 
> Bob
> 
> 
>      From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
>  To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>measurement <time-nuts@febo.com> 
>  Sent: Saturday, March 4, 2017 3:44 AM
>  Subject: Re: [time-nuts] Cs standard stability
>    
> Bob
> 
> That doesn't seem inconsistent with the specs given the contribution of the 
> 5370A to the measured ADEV is likely to be of the same order as the PRS45A 
> spec. The ADEV of the GPSDO also needs to be taken into account. The 
> contribution of the 5370A to ADEV will gradually become insignificant 
> compared to the PRS45A specs as Tau increases. To achieve an accurate 
> measurement of ADEV for Tau=1s you will need something better than the 5370A 
> together with a low ADEV source (for Tau = 1s).
> 
> Bruce
> > On 04 March 2017 at 18:26 Bob Stewart <b...@evoria.net> wrote:
> > 
> > 
> > I hooked up my PRS-45A yesterday, just to do some ADEV comparisons with my 
> > GPSDO.  Unfortunately, the GPSDO seems to be better by almost two points at 
> > all tau as measured on my HP 5370A and plotted by Timelab.  So, can I infer 
> > from that that the OCXO in the PRS has a problem, or could it be something 
> > as stupid as a bad c

Re: [time-nuts] Cs standard stability

[Bob Stewart]

Hi Bruce,
I'm aware that the GPSDO is better at low tau than the 5370.  This is born out 
by its low tau ADEV being right at the specs for the 5370, as well as by 
measurements done some time ago on a Timepod.  Unfortunately, I don't have a 
Timepod, so I have to make some guesses based on what I can see; limited as 
that is by the 5370.  But, given that the GPSDO tests validate the 5370, when I 
see an ADEV that is worse than the 5370's specs (i.e. worse than the result of 
the GPSDO test), I take that as an indication that the additional noise is from 
the DUT.  Of course, I don't know anything more than that.  Correct?

Bob


  From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 3:44 AM
 Subject: Re: [time-nuts] Cs standard stability
   
Bob

That doesn't seem inconsistent with the specs given the contribution of the 
5370A to the measured ADEV is likely to be of the same order as the PRS45A 
spec. The ADEV of the GPSDO also needs to be taken into account. The 
contribution of the 5370A to ADEV will gradually become insignificant compared 
to the PRS45A specs as Tau increases. To achieve an accurate measurement of 
ADEV for Tau=1s you will need something better than the 5370A together with a 
low ADEV source (for Tau = 1s).

Bruce
> On 04 March 2017 at 18:26 Bob Stewart <b...@evoria.net> wrote:
> 
> 
> I hooked up my PRS-45A yesterday, just to do some ADEV comparisons with my 
> GPSDO.  Unfortunately, the GPSDO seems to be better by almost two points at 
> all tau as measured on my HP 5370A and plotted by Timelab.  So, can I infer 
> from that that the OCXO in the PRS has a problem, or could it be something as 
> stupid as a bad cap?  Or do I just not understand the specs and the PRS isn't 
> up to my expectations?  The PRS docs show the unit as 3E-11 at 1s tau, and 
> I'm seeing about 4.25E-11 at 1s, so maybe it's the latter.
> 
> NOTE: The test setup for this is 1PPS from a well-aged GPSDO to the 5370's 
> start input, and 10MHz from either a different GPSDO or the PRS to the stop 
> input.
> 
>  As best as I can tell looking through the holes in the case (still running 
>the tests), the PRS has an MTI 250-0827 5MHz OCXO.  I've got one of the Lucent 
>KS units that I don't care much about, so maybe the MTI 260-0624 5MHz in that 
>will work?  Both are 5MHz, but I don't know whether both are 12V at this 
>point.  And, of course, I don't know whether making the swap to an MTI 260 
>OXCO will benefit the PRS.
> Any comments or educated speculations are welcomed.
> 
> Bob - AE6RV
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Cs standard stability

[Bob Stewart]

Bruce,
Are we getting a bit off track?  The question I asked is in regards to the Cs, 
not the purity of the output of the GPSDO.  The two ADEVs were done under the 
same conditions, yet the ADEV of the Cs is obviously not as good as that of the 
GPSDO.  Also, the ADEV of the GPSDO pretty much tracks what is to be expected 
when run on a good 5370, isn't it?

Bob 


  From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 5:22 PM
 Subject: Re: [time-nuts] Cs standard stability
   
BobThe Phase noise of that GPDSO seems quite high and some form of filtering 
(bandpass or low pass) of its output may be necessary to reduce the resultant 
jitter when connected to the 5370A input.There are commercial TDCs that claim 
that sort of performance (~10ps) but a comprehensive test of their actual 
performance appears as yet unavailable.HP used to sell a TDC with 5ps 
resolution but detailed specs are unavailable.Higher resolution and lower noise 
should be achievable but would require a lot of number crunching for each 
measurement. Bruce

   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Cs standard stability

[Bob Stewart]

OK, but how does the phase noise of the GPSDO make the ADEV for the Cs worse 
than that for the GPSDO?  I find it hard to believe that the phase noise from 
two separate units would cancel out for two GPSDOs but add for the Cs.

Bob 

  From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 6:03 PM
 Subject: Re: [time-nuts] Cs standard stability
   
BobWe are certainly not off track.The phase noise of the GPSDO affects the 
trigger jitter of both the 5370A and the jitter of the GPSDO PPS output and 
consequently the ADEV measured by your setup. NB ADEV depends on the 
measurement bandwidth which is relatively small when using a Timepod. Bruce
On 05 March 2017 at 12:31 Bob Stewart <b...@evoria.net> wrote:

Bruce,
Are we getting a bit off track?  The question I asked is in regards to the Cs, 
not the purity of the output of the GPSDO.  The two ADEVs were done under the 
same conditions, yet the ADEV of the Cs is obviously not as good as that of the 
GPSDO.  Also, the ADEV of the GPSDO pretty much tracks what is to be expected 
when run on a good 5370, isn't it?

Bob 


From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 5:22 PM
 Subject: Re: [time-nuts] Cs standard stability
 
BobThe Phase noise of that GPDSO seems quite high and some form of filtering 
(bandpass or low pass) of its output may be necessary to reduce the resultant 
jitter when connected to the 5370A input.There are commercial TDCs that claim 
that sort of performance (~10ps) but a comprehensive test of their actual 
performance appears as yet unavailable.HP used to sell a TDC with 5ps 
resolution but detailed specs are unavailable.Higher resolution and lower noise 
should be achievable but would require a lot of number crunching for each 
measurement. Bruce




   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Cs standard stability

[Bob Stewart]

Bruce,
For the moment, let's forget about the Timepod plot and just concentrate on the 
screenshot of the two Timelab runs on the 5370: one on GPSDO Unit 2, and one on 
the Cs.  Given that the test conditions were identical, down to the the clock 
source for the 5370, how can the phase noise on the GPSDO supplying the clock 
and 1PPS signals (Unit 1) benefit the ADEV of the GPSDO under test (Unit 2) 
while making the ADEV of the Cs worse?  I would expect that two units with 
similar phase noise would cause a worse measurement, rather than a better one.

Bob 

  From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 7:14 PM
 Subject: Re: [time-nuts] Cs standard stability
   
BobYou should to use the same measurement bandwidth when comparing ADEV 
measures.The measurement bandwidth of a Timepod is usually less than 1kHz 
whereas the 5370A has a trigger system bandwidth of 100MHz or so. If the high 
phase noise of your GPDSO isnt attenuated by a filter it may cause significant 
measurement noise.Bruce
On 05 March 2017 at 14:03 Bob Stewart <b...@evoria.net> wrote:

OK, but how does the phase noise of the GPSDO make the ADEV for the Cs worse 
than that for the GPSDO?  I find it hard to believe that the phase noise from 
two separate units would cancel out for two GPSDOs but add for the Cs.

Bob 

From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 6:03 PM
 Subject: Re: [time-nuts] Cs standard stability
 
BobWe are certainly not off track.The phase noise of the GPSDO affects the 
trigger jitter of both the 5370A and the jitter of the GPSDO PPS output and 
consequently the ADEV measured by your setup.NB ADEV depends on the measurement 
bandwidth which is relatively small when using a Timepod. Bruce
On 05 March 2017 at 12:31 Bob Stewart <b...@evoria.net> wrote:

Bruce,
Are we getting a bit off track?  The question I asked is in regards to the Cs, 
not the purity of the output of the GPSDO.  The two ADEVs were done under the 
same conditions, yet the ADEV of the Cs is obviously not as good as that of the 
GPSDO.  Also, the ADEV of the GPSDO pretty much tracks what is to be expected 
when run on a good 5370, isn't it?

Bob 


From: Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, March 4, 2017 5:22 PM
 Subject: Re: [time-nuts] Cs standard stability
 
BobThe Phase noise of that GPDSO seems quite high and some form of filtering 
(bandpass or low pass) of its output may be necessary to reduce the resultant 
jitter when connected to the 5370A input.There are commercial TDCs that claim 
that sort of performance (~10ps) but a comprehensive test of their actual 
performance appears as yet unavailable.HP used to sell a TDC with 5ps 
resolution but detailed specs are unavailable.Higher resolution and lower noise 
should be achievable but would require a lot of number crunching for each 
measurement. Bruce







   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
OK, thanks.  I've kicked off a 7 day run of a GFS against the PRS-45A.  That 
should be long enough to separate out the GFS from the PRS' drift direction 
from the ionosphere.

Bob 



  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Monday, April 17, 2017 11:28 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi
The ionosphere is the culprit in terms of the daily swing. The swing is a 
function of the goodness of fit between the GPS broadcast dataand the 
ionosphere as it impacts the satellites you are using. There is no rime or 
reason to it beyond that. If you get “lucky” things don’t move much. If you 
live in exciting times, things move quite a bit. Unless you go to something 
like an L1/L2 receiver, the GPS module you use has little to do with it (unless 
it’s broke ….). Yes there are some fiddly little qualifiers relating to being 
at the north or south pole and GPS coverage (along with space weather impacts). 
Very few of us do our runs at either location :) Just for reference, the area 
of concern also hasat least one day each year where the sun sets for < 1 hours. 
Bob




On Apr 17, 2017, at 11:33 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
Oh, I had completely forgotten about the many runs you gifted us with back 
then.  Fortunately, I kept all of them in my email archive.  I can't compare 
like for like, of course, but I think I can work up something that compares at 
the larger taus where the 5370 doesn't dominate.
I'm going to run another long term test of my GFS unit against my PRS-45A.  The 
problem, the issue that made me ask for data is that everything from phase 
plots to ADEV plots of my unit are just so much better than the KS.  In 
addition, I don't see the large ionospheric swings on my GFS unit that you and 
Bruce and others have spoken about.  This bothers me a lot.  Could it be my 
location here in Houston?  Could it be the Ublox LEA-6T compared to the much 
older Motorola in the KS?

Bob 

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Monday, April 17, 2017 7:55 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi
The data I have on the KS boxes was posted to the list back when they were.a 
hot topic. I’m sure it is still in the archives.I’m guessing it’s not quite 
what you are after. 

The closer the devices are to each other the better the technique works. A 
simple way to look at it is as an attenuation. If it knocks noise down 10:1, 
the worst unit should be no more than 10X noise than the best unit. How much 
things are knockeddown is a function of the length of the runs compared to the 
longest tau. For a 10:1 ratio of tau to run, attenuation of noise by 10:1 is 
very optimistic. You usually  need something beyond 100:1 to get that sort of 
performance. A lot depends on the noise involved. Some types of behavior simply 
don’t work well with the technique. 
The KS box goes from “better than” to “worse than” and back to “better than” 
most atomic standards you would compare it to overa range of tau from 0.1 S to 
1,000,000 seconds. To get the 1,000,000 second data accurately, you would need 
a 100,000,000 secondrun. The simple answer there is that nobody has that kind 
of time or that reliable a setup. Even the three month run to get good100,000 
second data is a challenge. None of that relates to three corner hat stuff, 
it’s just the confidence bars on ADEV. It givesyou another (say) 100:1 wait on 
top of the three corner stuff. 
Now toss in the basics of GPS. Depending on the day, you will get <10 ns to  
>100 ns swing over a  24 hour period. Today may or may not be the same as 
tomorrow. That’s with a “perfect” L1 setup. The variation comes from the 
ionosphere and the fact thatthe GPS data does not allow you to fully correct 
for it.  In addition, you will get some interesting bumps related to 
constellations and your local antenna setup. Any GPSDO that is quartz based 
will happily follow the 24 hour swing in the GPS from the ionosphere. At 
100,000 seconds, a 100 ns swing is 1x10^-12. That’s a lot of disruption. It 
most certainly is not the sort of thing that ADEV expects to pop up in the 
middle of a run. 
The simple answer to all this is “don’t go there”. Three corner hat is fine for 
short term stuff. It’s a mess for long term runs. Getting datathat is good 
enough for a long term ADEV run out of a three corner setup is a major 
struggle. The time for the correlation to knock downthe noise on top of the 
time to get good ADEV data gets you into impractically long runs. 
Bob




On Apr 16, 2017, at 10:16 PM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
OK, I give up.  Try as I might, I can't fudge things enough to make any sense.  
I did run a se

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Tom,
The reason I express so much confusion over this is because I don't see the 
wild phase excursions on my GFS units that people insist will happen due to 
ionospheric effects.  Is this because they are rare events, and I just haven't 
been saving data during a bad time?  I notice in your example page, you aren't 
seeing them, either during your 8+ day capture of the Tbolt.

Bob 


  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Monday, April 17, 2017 3:05 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Bob S,

Here's an example of a one week GPSDO run:

http://leapsecond.com/pages/tbolt-8d/

IIRC, this was a default, untuned, self-surveyed TBolt. You can see some level 
of daily variations -- probably a mix of sky view, survey error, ionosphere, 
multi-path, sidereal effects [1], temperature (antenna, cable, GPSDO, 
reference), etc. It takes some time and equipment to sort out which is which, 
but even a simple test like this can give you an upper bound.

/tvb

[1] Fun GPS orbit stuff here:
http://leapsecond.com/pages/sidereal/index.htm
http://leapsecond.com/pages/sidereal/14years.htm
http://leapsecond.com/pages/sidereal/sv.htm
http://leapsecond.com/pages/gps-orbit/


- Original Message ----- 
From: "Bob Stewart" <b...@evoria.net>
To: "Bob kb8tq" <kb...@n1k.org>; "Discussion of Precise Time and Frequency 
Measurement" <time-nuts@febo.com>
Sent: Monday, April 17, 2017 9:33 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?


Hi Bob,
OK, thanks. I've kicked off a 7 day run of a GFS against the PRS-45A. That 
should be long enough to separate out the GFS from the PRS' drift direction 
from the ionosphere.

Bob 



      From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Monday, April 17, 2017 11:28 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi
The ionosphere is the culprit in terms of the daily swing. The swing is a 
function of the goodness of fit between the GPS broadcast dataand the 
ionosphere as it impacts the satellites you are using. There is no rime or 
reason to it beyond that. If you get “lucky” things don’t move much. If you 
live in exciting times, things move quite a bit. Unless you go to something 
like an L1/L2 receiver, the GPS module you use has little to do with it (unless 
it’s broke ….). Yes there are some fiddly little qualifiers relating to being 
at the north or south pole and GPS coverage (along with space weather impacts). 
Very few of us do our runs at either location :) Just for reference, the area 
of concern also hasat least one day each year where the sun sets for < 1 hours. 
Bob




On Apr 17, 2017, at 11:33 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
Oh, I had completely forgotten about the many runs you gifted us with back 
then. Fortunately, I kept all of them in my email archive. I can't compare like 
for like, of course, but I think I can work up something that compares at the 
larger taus where the 5370 doesn't dominate.
I'm going to run another long term test of my GFS unit against my PRS-45A. The 
problem, the issue that made me ask for data is that everything from phase 
plots to ADEV plots of my unit are just so much better than the KS. In 
addition, I don't see the large ionospheric swings on my GFS unit that you and 
Bruce and others have spoken about. This bothers me a lot. Could it be my 
location here in Houston? Could it be the Ublox LEA-6T compared to the much 
older Motorola in the KS?

Bob 

      From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Monday, April 17, 2017 7:55 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi
The data I have on the KS boxes was posted to the list back when they were.a 
hot topic. I’m sure it is still in the archives.I’m guessing it’s not quite 
what you are after. 

The closer the devices are to each other the better the technique works. A 
simple way to look at it is as an attenuation. If it knocks noise down 10:1, 
the worst unit should be no more than 10X noise than the best unit. How much 
things are knockeddown is a function of the length of the runs compared to the 
longest tau. For a 10:1 ratio of tau to run, attenuation of noise by 10:1 is 
very optimistic. You usually need something beyond 100:1 to get that sort of 
performance. A lot depends on the noise involved. Some types of behavior simply 
don’t work well with the technique. 
The KS box goes from “better than” to “worse than” and back to “better than” 
most atomic standards you would compare it to overa range of tau from 0.1 S to 
1,000,000 seconds. To get the 1,000,000 second data accuratel

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
said:
"You have roughly 25 ns p-p in the data you show."
OK, here's a misunderstanding on my part right off the bat.  You see the swing 
as a p-p value, when I've been looking at it as only +/- 12.5ns from the 
trendline.

said some time ago:
"Now toss in the basics of GPS. Depending on the day, you will get <10 ns to  
>100 ns swing over a  24 hour period. Today may or may not be the same as 
tomorrow."
So maybe I'm thinking too much about the >100ns figure, and not so much about 
the <10ns figure you mentioned.  The average doesn't seem to do much for me, 
either.  So, is the probability curve between 10ns and 100ns, where 100ns is 
least probable, of the type  y=2^-x?  IOW, in a year, I might see one 100ns 
swing, I would probably see at least one or two 50ns swings, and will probably 
see anything less than that multiple times, with the probably increasing as the 
value gets lower.

Not trying to crucify you with your own words, Bob.  Like many of the time-nuts 
who don't post, I'm just trying to make some sense of this in terms I can deal 
with.

Bob

 From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: Magnus Danielson <mag...@rubidium.se>
 Sent: Thursday, April 27, 2017 1:18 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi


You have roughly 25 ns p-p in the data you show. There are a number of 10 ns 
“cycles” in the data. 
Any of this *may* be due to ionosphere. They also could be due to other issues. 
 With ~4.4 days of noisy
data, it may be tough to spot a trend. Since the ionosphere is a bit random, 
there is no guarantee that
you *will* always see a pretty sinusoidal trend line through the data. It’s a 
good bet that things quiet down
around midnight. There is no guarantee that they always go nuts (or go nuts to 
the same degree) around noon. 

Bob


> On Apr 27, 2017, at 12:48 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Magnus,
> Try as I might, the weather and the local power company had other ideas about 
> my long term capture.  I'm running everything but the 5370 from a UPS.  I 
> guess I'm going to have to get batteries for my other UPS and run the 5370 
> from that.  A one second power loss was all it took to stop the test.
> 
> Anyway, I did manage to get 376,238 points of data.  The data is captured on 
> a 5370A.  The external clock input and the STOP channel are fed by the 10MHz 
> from my PRS-45A.  The START channel is fed by the 10MHz from one of my 
> GPSDOs.  The EXT channel is fed by the 1PPS from another of my GPSDO units.  
> "EXT ARM" is enabled.  So, essentially, at every 1PPS pulse, the phase 
> difference between the two 10MHz feeds is captured.
> 
> I've attached a screenshot of the phase plot which can also be found 
> here:http://evoria.net/AE6RV/Timelab/Screenshot.png
> I've also made the timelab file (compressed by 7z) available here:
> http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z
> 
> So, back to my question:  Where are the large ionospheric phase moves?  This 
> question has been causing me doubt since I started on this project.  Or don't 
> I still have enough data collected for this to happen?
> 
> Bob
> 
> -----
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Magnus Danielson <mag...@rubidium.dyndns.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Cc: mag...@rubidium.se
> Sent: Tuesday, April 18, 2017 1:09 AM
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
> 
> Hi Bob,
> 
> That is a good solution indeed. Good luck with that measurement run!
> 
> One of the fun stuff with Timelab is that you can walk by and check the 
> developments. I've found that very useful for long measurements (as in 
> hours and days).
> 
> I prepared a cesium for one vendor, and initially they did not care so 
> much, but then they saw more deviations between the receivers, so they 
> wanted to sort it out, but discovered that they could not cancel out the 
> common mode of GPS signals (and its shifts), so then firing up that 
> cesium was the right thing. I remember writing support emails while 
> waiting for the airplane in Madrid airport, happy that they was doing a 
> first run for the right measurement reason. :)
> 
> Cheers,
> Magnus
> 
> On 04/18/2017 04:25 AM, Bob Stewart wrote:
>> Hi Magnus,
>> Today I started a long run against my PRS-45A.  Maybe this time I won't have 
>> a power outage.  I'll see what it tells me in a few days.
>> Bob
> 
> _

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Magnus,
Try as I might, the weather and the local power company had other ideas about 
my long term capture.  I'm running everything but the 5370 from a UPS.  I guess 
I'm going to have to get batteries for my other UPS and run the 5370 from that. 
 A one second power loss was all it took to stop the test.

Anyway, I did manage to get 376,238 points of data.  The data is captured on a 
5370A.  The external clock input and the STOP channel are fed by the 10MHz from 
my PRS-45A.  The START channel is fed by the 10MHz from one of my GPSDOs.  The 
EXT channel is fed by the 1PPS from another of my GPSDO units.  "EXT ARM" is 
enabled.  So, essentially, at every 1PPS pulse, the phase difference between 
the two 10MHz feeds is captured.

I've attached a screenshot of the phase plot which can also be found 
here:http://evoria.net/AE6RV/Timelab/Screenshot.png
I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z

So, back to my question:  Where are the large ionospheric phase moves?  This 
question has been causing me doubt since I started on this project.  Or don't I 
still have enough data collected for this to happen?

Bob

-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Magnus Danielson <mag...@rubidium.dyndns.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: mag...@rubidium.se
 Sent: Tuesday, April 18, 2017 1:09 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi Bob,

That is a good solution indeed. Good luck with that measurement run!

One of the fun stuff with Timelab is that you can walk by and check the 
developments. I've found that very useful for long measurements (as in 
hours and days).

I prepared a cesium for one vendor, and initially they did not care so 
much, but then they saw more deviations between the receivers, so they 
wanted to sort it out, but discovered that they could not cancel out the 
common mode of GPS signals (and its shifts), so then firing up that 
cesium was the right thing. I remember writing support emails while 
waiting for the airplane in Madrid airport, happy that they was doing a 
first run for the right measurement reason. :)

Cheers,
Magnus

On 04/18/2017 04:25 AM, Bob Stewart wrote:
> Hi Magnus,
> Today I started a long run against my PRS-45A.  Maybe this time I won't have 
> a power outage.  I'll see what it tells me in a few days.
> Bob

   ___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] TAPR Oncore M12+ kit

[Bob Stewart]

Hi Bob,
It may be because the process of cutting the boards apart is not part of the 
board milling process.  Yes, cutting holes in boards for through-hole parts is 
part of the business - round holes.  The fab house for OSHPark won't make oval 
holes.  They won't overlap two holes, either, nor make square notches.  This is 
only a guess, but I'd say that this is because they use actual drill bits to 
make those holes, rather than a laser.  Drill bits are expensive, and it takes 
a lot of time to change a drill bit when you've got hundreds of boards to mill. 
 It's not something I would want to do, either, without a serious penalty for 
the customer for a broken bit due to odd shaped holes and missed deadlines.

And OSHPark seems to use different fab houses for the small runs vs the large 
(10+) runs.  With the small runs, the boards are connected to each other by 
small tabs.  Often small boards arrive still tabbed together.  I don't know 
whether they route the distance between these tabs, or use a laser.  On the 
larger runs, there are no tabs, and the board edges are smooth, as if they were 
cut apart in one single operation not part of the milling process.

NB, I don't work for a fab house, nor have I ever toured one.

Bob 



  From: Bob kb8tq 
 To: Discussion of precise time and frequency measurement  
 Sent: Friday, April 28, 2017 1:06 PM
 Subject: Re: [time-nuts] TAPR Oncore M12+ kit
   
Hi

If you go with the PCB approach, the nice thing is getting stuff like
the slot for the D connector done at the PCB fab. That way you 
have something that drops right in and works. The downside is that 
not every pcb house is happy doing that sort of “CNC work”.  I 
have absolutely no idea why. They all have to run some sort of gear
to cut the boards apart. Cutting slots or weird holes with it is pretty
trivial. 

Bob

   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
OK, since we are in a low sunspot cycle, then it would follow that the 100ns 
movements would be rare.  Also, since I'm at about 29.8 degrees north, with few 
obstructions or reflectors to cause a problem, that improves what I'm capable 
of seeing out of what's available.  As to what problems are buried in my data 
due to equipment limitations, you're welcome to give me a long term loan of a 
nice H Maser and Timepod.  I promise I'll treat them well!  =)

Anyway, thanks for the explications.  As mentioned, I see figures bandied about 
on timenuts, but no explanation of the variables that cause those figures to be 
true or not true.  When I don't see them happening in my "lab", then I get 
confused.  I'm pretty certain I'm not the only one this happens to.  Several of 
you have been adamant about ionospheric effects north of 60ns.  I just haven't 
seen them.

Bob 

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Thursday, April 27, 2017 4:17 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi
Dig into space weather if you want to get into the details of the why and how 
often. It’s all out thereGoogle is your friend. Things like sun spot cycles are 
one of many drivers. The more perturbed the space weather is day to day, the 
more likely you are to see changes in the GPS.  Monitor the spaceweather sites 
on a regular basis and you will be able to make some guesses about what’s 
likely to happen. It’s only going to be a guess, no better than the 10 day 
weather forecast :) One of manysites: http://www.swpc.noaa.gov . A bit about 
what to watch for: 
http://www.swpc.noaa.gov/impacts/space-weather-and-gps-systemsThis one is a bit 
HF oriented: http://www.sws.bom.gov.au/HF_Systems/6/5
That’s only the first part.
The second part is that the delta ionosphere *is* fit by GPS data. What you are 
concerned with is not just a "bump' of space weather. You are concerned with 
one that does not fit well. That’s a normalthing when the weather is rough, but 
not an always thing.  A peak solar flux event that ramps upslow and decays 
slowly is very different than one with faster changes. You do get both. 
Patchydisruptions in the ionosphere are worse than a uniform high. They are 
hard to fit.
Next up …
The goodness of fit depends a lot on the sat’s you are using for your 
processing and where they arelocated in the sky. If you happen to have a sat 
that sends a signal across a big long patch of poorly fitionosphere,  you have 
a problem. If every single sat you are using is straight over head and your 
house is well fit, there is no problem.  Longer paths by their nature are more 
likely to be an issue.Bad fit only matters if you are depending to some extent 
on that part of the sky.  How much longer vs shorter contributes to your 
solution right now is always a “that depends” sort of thing. 
Is that all there is?
No, not hardly, that’s just the easy part. The troposphere also gets into the 
act and it flies around a bit. Last time I checked, they just use a static 
model there so it’s not a broadcast vs reality issue.You also get into things 
like location and sat angle from your location. If you are in northern 
Greenlandthings will be a bit different than in Ceylon. There are a few other 
issues I could probably dive into with a bit of research. 
So no, it’s not simple. How often do you see > 100 ns? Best data I’ve seen is 
that you hit that range a few times a year on average. More so at solar maxima 
and less so at solar minima. It’s no different than propagation on 10 meters. 
If you are looking for 100 ns every day, day in and day out, that’s not going 
to happen. 
You *are* looking for a peak to peak sort of swing. If you already have 20 ns 
wander in the data, you are going to have a hard time seeing anything much 
below 20 ns. What you are looking for is most likely to have a 86,000 second 
period (= day - night cycle). My guess is that you don’t see it because it’s 
buried in the noise of your data.
Not at all easy….
Bob


On Apr 27, 2017, at 3:10 PM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
said:
"You have roughly 25 ns p-p in the data you show."
OK, here's a misunderstanding on my part right off the bat.  You see the swing 
as a p-p value, when I've been looking at it as only +/- 12.5ns from the 
trendline.

said some time ago:
"Now toss in the basics of GPS. Depending on the day, you will get <10 ns to  
>100 ns swing over a  24 hour period. Today may or may not be the same as 
tomorrow."
So maybe I'm thinking too much about the >100ns figure, and not so much about 
the <10ns figure you mentioned.  The average doesn't seem to do much for me, 
either.  So, is the probability curve between 10ns and 100ns, where 100ns is 
least probable, of the type  y=2^-x?  IOW, in a year, I might see one 100ns 
swin

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Jim,
said:"Ionosphere is one - if you're near a ionosonde you might be able to get a 
data set to correlate against.  It's not necessarily a "worst at noon, best at 
midnight" thing - some of the satellites contributing to your fix will be on 
slant paths, so the solar ionization is not uniform." Are the Ublox timing 
receivers a lot better at getting rid of ionospheric phase shifts because they 
can see more sats than the older Motorola receivers?
And as a point of reference, the dataset I linked begins at ~9:21AM CST on 
4/22/2017.  I'm in west Houston, TX.

Bob

  From: jimlux <jim...@earthlink.net>
 To: time-nuts@febo.com 
 Sent: Thursday, April 27, 2017 5:03 PM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
On 4/27/17 12:10 PM, Bob Stewart wrote:
> Hi Bob,
> said:
> "You have roughly 25 ns p-p in the data you show."
> OK, here's a misunderstanding on my part right off the bat.  You see the 
> swing as a p-p value, when I've been looking at it as only +/- 12.5ns from 
> the trendline.
>
> said some time ago:
> "Now toss in the basics of GPS. Depending on the day, you will get <10 ns to  
> >100 ns swing over a  24 hour period. Today may or may not be the same as 
> tomorrow."
> So maybe I'm thinking too much about the >100ns figure, and not so much about 
> the <10ns figure you mentioned.  The average doesn't seem to do much for me, 
> either.  So, is the probability curve between 10ns and 100ns, where 100ns is 
> least probable, of the type  y=2^-x?  IOW, in a year, I might see one 100ns 
> swing, I would probably see at least one or two 50ns swings, and will 
> probably see anything less than that multiple times, with the probably 
> increasing as the value gets lower.
>
> Not trying to crucify you with your own words, Bob.  Like many of the 
> time-nuts who don't post, I'm just trying to make some sense of this in terms 
> I can deal with.
>
> Bob
>
>      From: Bob kb8tq <kb...@n1k.org>
>  To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>measurement <time-nuts@febo.com>
> Cc: Magnus Danielson <mag...@rubidium.se>
>  Sent: Thursday, April 27, 2017 1:18 PM
>  Subject: Re: [time-nuts] Three-cornered hat on timelab?
>
> Hi
>
>
> You have roughly 25 ns p-p in the data you show. There are a number of 10 ns 
> “cycles” in the data.
> Any of this *may* be due to ionosphere. They also could be due to other 
> issues.  With ~4.4 days of noisy
> data, it may be tough to spot a trend. Since the ionosphere is a bit random, 
> there is no guarantee that
> you *will* always see a pretty sinusoidal trend line through the data. It’s a 
> good bet that things quiet down
> around midnight. There is no guarantee that they always go nuts (or go nuts 
> to the same degree) around noon.
>
> Bob
>


I don't think it necessarily has a nice distribution.  precise phase 
measurement with GPS has lots of effects that are in the "about a meter" 
range.

Ionosphere is one - if you're near a ionosonde you might be able to get 
a data set to correlate against.  It's not necessarily a "worst at noon, 
best at midnight" thing - some of the satellites contributing to your 
fix will be on slant paths, so the solar ionization is not uniform.

Solid earth tides are another effect in that general magnitude (10s of 
cm) - see Wikipedia or:
https://www.unavco.org/education/professional-development/short-courses/course-materials/strainmeter/2005-strainmeter-course-materials/tidenote.pdf


Thermal expansion and contraction of a variety of things:
1) the structure supporting your antenna
2) the earth's surface
3) the coax from antenna to receiver
4) any filters
5) the antenna

For most of these, they *are* periodic in some sense: solid earth tides 
are affected by moon and sun, which have reasonably well known periods. 
Thermal effects typically have a strong 24 hour cycle (although I've 
seen some weird ones caused by shadows intermittently falling on stuff, 
but still, it has a 24 hour periodicity)


Then there's various geometry/multipath things - choke rings help if 
you're in a wide open area.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Magnus,
OK, a couple of things about my location.  I'm in West Houston, and it's not 
summer yet, so there's a lot of variation in temperature from day to day.  Some 
nights it's in the 40sF and some nights it's in the high 70s or low 80sF.  Lots 
of variation in the days, as well.  My antenna is not optimal, at all.  The 
best I could do was to remove the dish from an unused DishTV antenna and 
install my GPS antenna on top of the little mast they use.  It's about the best 
I can do.  In fact, it's better than I expected.
The receiver is a LEA-6T that was put through a 24 hour survey and the position 
was saved in flash memory.  However, there have been lots of power cycles since 
that survey.  Whether or not that affects the result, I don't know.

Still, the point of the test was to understand why I'm not getting these large 
phase swings.  And I think Bob Camp's explanation was good.  Maybe in another 5 
years the sunspots will be back up and I can see the comparison to now. Bob

  From: Magnus Danielson <mag...@rubidium.se>
 To: Bob Stewart <b...@evoria.net>; Discussion of Precise Time and Frequency 
Measurement <time-nuts@febo.com> 
Cc: mag...@rubidium.se
 Sent: Saturday, April 29, 2017 6:45 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi Bob,

On 04/27/2017 06:48 PM, Bob Stewart wrote:
> Hi Magnus,
>
> Try as I might, the weather and the local power company had other ideas
> about my long term capture.  I'm running everything but the 5370 from a
> UPS.  I guess I'm going to have to get batteries for my other UPS and
> run the 5370 from that.  A one second power loss was all it took to stop
> the test.

Annoying, but you got some good values never the less.

> Anyway, I did manage to get 376,238 points of data.  The data is
> captured on a 5370A.  The external clock input and the STOP channel are
> fed by the 10MHz from my PRS-45A.  The START channel is fed by the 10MHz
> from one of my GPSDOs.  The EXT channel is fed by the 1PPS from another
> of my GPSDO units.  "EXT ARM" is enabled.  So, essentially, at every
> 1PPS pulse, the phase difference between the two 10MHz feeds is captured.

OK, this seems like a good setup.

> I've attached a screenshot of the phase plot which can also be found here:
> http://evoria.net/AE6RV/Timelab/Screenshot.png
>
> I've also made the timelab file (compressed by 7z) available here:
> http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z

Thank you for providing the data, I downloaded it so I can play around 
with it, which I naturally did. :)

> So, back to my question:  Where are the large ionospheric phase moves?
> This question has been causing me doubt since I started on this
> project.  Or don't I still have enough data collected for this to happen?

Your data seems to be more affected by constellation shifts, as the 
period of about 43080 s seems to be a period of the constellation.
You either have averaged out to a somewhat incorrect position of your 
antenna or you have sub-optimal position of your antenna.

It gives you a peak-to-peak amplitude of about 10 ns or so.

The ionospheric errors has a period of 86400s, so to get a clear 
separation of these would take more data. However, playing around with 
the data in TimeLab allowed me to filter out some of the other systematics.

The day-to-day variations is noticeable. I wonder how much of that is 
thermal though. The building variations was filtered out in the process.

One has to identify a number of these potential disturbances, estimate 
their size in order to more clearly see other things. TimeLab has a 
notch filter to notch out a particular frequency. It would be nice if an 
alternative approach would be to give the notch a period.

One has to recall that even and odd harmonics to a disturbance frequency 
can be there, as it is not always a pure sine disturbance.

Cheers,
Magnus


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

[time-nuts] 5370 problems, was Re: Three-cornered hat on timelab?

[Bob Stewart]

Hi Tom et al,
It looks like I've got a problem with my 5370 when collecting 10MHz data using 
an external arming signal.  I did some tests today, sending 10MHz through a 
~10ft delay line (about 8.26ns) between the START and STOP inputs.  It's a 
mess, with some interval deltas being as high as 13 ns.  I tested with both an 
external clock and the internal 10811 clock with essentially the same result.
I'm running a test right now using a 1PPS signal and the delay line with no 
external arming signal, and, so far, there's no problem.
So, back to the drawing board.

Bob 

-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Wednesday, May 3, 2017 12:02 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi BobS,

> I've also made the timelab file (compressed by 7z) available here:
> http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z

Thanks for sharing that. To follow-up on recent emails...

When you start to push the limits of your own test equipment it's good to 
employ tricks such as 3-corner hat in order to get a few dB better measurement. 
But there's a limit to that. And you probably don't want me to suggest that you 
run 3 GPSDO, 3 counters and 3 cesiums all simultaneously.

I've attached two plots showing 4+ days of your GPSDO data and 4+ days of a 
TBolt (factory defaults, *untuned*)

bob-gpsdo-3.gif -- Notice how much your GPSDO (blue trace) wanders all over the 
place.

bob-gpsdo-5.gif -- ADEV comparison. See below for comments.

1)
When I look at the ADEV for your data set it's pretty clear that the limiting 
factor on the left (short tau) is the resolution of your 5370A counter. That's 
why the TBolt looks better. Don't worry about that.

2)
In the middle of the ADEV plot it would appear that both your 5370A counter and 
your PRS-45A cesium reference are sufficiently good to properly measure your 
GPSDO. That's good. The TBolt looks bad in the middle but that's simply because 
it was using a way-too-short default time constant. With proper tuning the red 
trace would be mostly flat out to 1000 seconds.

3)
>From the look of the phase plot and the ADEV plot it almost seems to me like 
>your PRS-45A is the limiting factor on the right (long tau). If so, it would 
>explain the lack of diurnal and sidereal effects in your data. If you look at:
http://leapsecond.com/pages/tbolt-8d/sigma1.gif from 
http://www.leapsecond.com/pages/tbolt-8d/
you'll note the sidereal "blip" is below 4e-14. Your ADEV doesn't get near that 
level.


I say this because a rule-of-thumb is that a good M12+T timing receiver should 
get you down to 3 ns per day RMS. And a good ublox-6T can get you to 3 or 2 ns 
per day RMS. Your data shows something more like 5 ns -- which for a GPSDO is 
worse than no GPSDO at all. So something's wrong. What set of experiments can 
you perform to locate the problem? Or, what experiments can you perform that 
don't require buying expensive gear?

My first suggestion is for you run a standalone GPS timing receiver like a 
M12+T or ublox-6. Put all your GPSDO away. Just use that OEM board, and your 
TIC, and your PRS-45A. Collect sawtooth data too. You should get down to 2 or 3 
ns RMS.

/tvb

----- Original Message - 
From: "Bob Stewart" <b...@evoria.net>
To: "Discussion of Precise Time and Frequency Measurement" 
<time-nuts@febo.com>; "Magnus Danielson" <mag...@rubidium.se>
Sent: Thursday, April 27, 2017 9:48 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?


Hi Magnus,
Try as I might, the weather and the local power company had other ideas about 
my long term capture. I'm running everything but the 5370 from a UPS. I guess 
I'm going to have to get batteries for my other UPS and run the 5370 from that. 
A one second power loss was all it took to stop the test.

Anyway, I did manage to get 376,238 points of data. The data is captured on a 
5370A. The external clock input and the STOP channel are fed by the 10MHz from 
my PRS-45A. The START channel is fed by the 10MHz from one of my GPSDOs. The 
EXT channel is fed by the 1PPS from another of my GPSDO units. "EXT ARM" is 
enabled. So, essentially, at every 1PPS pulse, the phase difference between the 
two 10MHz feeds is captured.

I've attached a screenshot of the phase plot which can also be found 
here:http://evoria.net/AE6RV/Timelab/Screenshot.png
I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z

So, back to my question: Where are the large ionospheric phase moves? This 
question has been causing me doubt since I started on this project. Or don't I 
still have enough data collected for this to happen?

Bob

-

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
Won't I have a problem with the phase wrap unless I convert the data to a range 
of +50ns to -50ns?  Or am I still looking at this incorrectly?
 Bob
-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Wednesday, May 3, 2017 10:48 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi
Dump it to a csv file and do it in Excel would be one way. You want to be 
ableto control the process a bit so that would give you the ability to tweak 
the measurement.
Bob

On May 3, 2017, at 11:01 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
What I should have asked is this: "how do I get that from a Timelab dataset?"   
Bob


  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: Tom Van Baak <t...@leapsecond.com>
 Sent: Wednesday, May 3, 2017 7:20 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi
RMS:
https://en.wikipedia.org/wiki/Root_mean_square
When we talk about things like “6 sigma” in QA, the sigma is the RMS. 
Bob

On May 3, 2017, at 1:44 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Tom,
Could you clarify the term RMS?  Is there some sort of calculation I need to do 
on the raw data to get the RMS value?
I'm going to begin by doing a fresh 8 hour test of GPSDO Unit 1 vs GPSDO Unit 
2, with the same conditions as the tests involving the PRS.  IOW, the 5370 is 
being clocked by GPSDO Unit 2, and the trigger for the EXT input to the 5370 is 
from GPSDO Unit 2.  START is from GSPDO Unit 1 and STOP is from GPSDO Unit 2.  
The ones I have on hand show about 4E-11 at 1s tau.  

After that, I'll run an 8 hour test of raw 1PPS from a LEA-6T against the PRS.  
Since I don't really trust the PRS, I'll use GPSDO Unit 2 to clock the 5370.  
If you really don't want the GSPDO to clock the 5370, I'll run the same test 
using the internal 10811 as the clock, to compare the difference.

I also ran into an old test of the 5370 where START (10MHz) was fed by a GPSDO 
and STOP (10MHz) was fed by the same GPSDO but with (I think) a 20 ft cable 
from START to STOP.  I'll probably want to rerun that, as well, but it was an 
almost straight line from 2E-11 at 1s tau in that dataset.  Still, that test 
will verify that the 5370 hasn't degraded. Bob

  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Wednesday, May 3, 2017 12:02 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?

Hi BobS,


I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z


Thanks for sharing that. To follow-up on recent emails...

When you start to push the limits of your own test equipment it's good to 
employ tricks such as 3-corner hat in order to get a few dB better measurement. 
But there's a limit to that. And you probably don't want me to suggest that you 
run 3 GPSDO, 3 counters and 3 cesiums all simultaneously.

I've attached two plots showing 4+ days of your GPSDO data and 4+ days of a 
TBolt (factory defaults, *untuned*)

bob-gpsdo-3.gif -- Notice how much your GPSDO (blue trace) wanders all over the 
place.

bob-gpsdo-5.gif -- ADEV comparison. See below for comments.

1)
When I look at the ADEV for your data set it's pretty clear that the limiting 
factor on the left (short tau) is the resolution of your 5370A counter. That's 
why the TBolt looks better. Don't worry about that.

2)
In the middle of the ADEV plot it would appear that both your 5370A counter and 
your PRS-45A cesium reference are sufficiently good to properly measure your 
GPSDO. That's good. The TBolt looks bad in the middle but that's simply because 
it was using a way-too-short default time constant. With proper tuning the red 
trace would be mostly flat out to 1000 seconds.

3)
>From the look of the phase plot and the ADEV plot it almost seems to me like 
>your PRS-45A is the limiting factor on the right (long tau). If so, it would 
>explain the lack of diurnal and sidereal effects in your data. If you look at:
http://leapsecond.com/pages/tbolt-8d/sigma1.gif from 
http://www.leapsecond.com/pages/tbolt-8d/
you'll note the sidereal "blip" is below 4e-14. Your ADEV doesn't get near that 
level.


I say this because a rule-of-thumb is that a good M12+T timing receiver should 
get you down to 3 ns per day RMS. And a good ublox-6T can get you to 3 or 2 ns 
per day RMS. Your data shows something more like 5 ns -- which for a GPSDO is 
worse than no GPSDO at all. So something's wrong. What set of experiments can 
you perform to locate the problem? Or, what experiments

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
OK, I think I see my error.  I need to create a file of the successive phase 
differences in the timelab capture, right?  I haven't done this before, so...

Bob 

-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Wednesday, May 3, 2017 11:11 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi
If you convert the data to +/- 50 ns, you will have a problem at the edges. 
Much easier to deal with unwrapped data. The same CSV approach works for taking 
the pps data from a module, logging the sawtooth info and combining them. 
There’s no practical way to get the “real” RMS of the module without doing 
that. 
Bob

On May 3, 2017, at 11:56 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
Won't I have a problem with the phase wrap unless I convert the data to a range 
of +50ns to -50ns?  Or am I still looking at this incorrectly?
 Bob
-
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net> 
Cc: Discussion of precise time and frequency measurement <time-nuts@febo.com>
 Sent: Wednesday, May 3, 2017 10:48 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi
Dump it to a csv file and do it in Excel would be one way. You want to be 
ableto control the process a bit so that would give you the ability to tweak 
the measurement.
Bob

On May 3, 2017, at 11:01 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Bob,
What I should have asked is this: "how do I get that from a Timelab dataset?"   
Bob


  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: Tom Van Baak <t...@leapsecond.com>
 Sent: Wednesday, May 3, 2017 7:20 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
  
Hi
RMS:
https://en.wikipedia.org/wiki/Root_mean_square
When we talk about things like “6 sigma” in QA, the sigma is the RMS. 
Bob

On May 3, 2017, at 1:44 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Tom,
Could you clarify the term RMS?  Is there some sort of calculation I need to do 
on the raw data to get the RMS value?
I'm going to begin by doing a fresh 8 hour test of GPSDO Unit 1 vs GPSDO Unit 
2, with the same conditions as the tests involving the PRS.  IOW, the 5370 is 
being clocked by GPSDO Unit 2, and the trigger for the EXT input to the 5370 is 
from GPSDO Unit 2.  START is from GSPDO Unit 1 and STOP is from GPSDO Unit 2.  
The ones I have on hand show about 4E-11 at 1s tau.  

After that, I'll run an 8 hour test of raw 1PPS from a LEA-6T against the PRS.  
Since I don't really trust the PRS, I'll use GPSDO Unit 2 to clock the 5370.  
If you really don't want the GSPDO to clock the 5370, I'll run the same test 
using the internal 10811 as the clock, to compare the difference.

I also ran into an old test of the 5370 where START (10MHz) was fed by a GPSDO 
and STOP (10MHz) was fed by the same GPSDO but with (I think) a 20 ft cable 
from START to STOP.  I'll probably want to rerun that, as well, but it was an 
almost straight line from 2E-11 at 1s tau in that dataset.  Still, that test 
will verify that the 5370 hasn't degraded. Bob

  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Wednesday, May 3, 2017 12:02 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?

Hi BobS,


I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z


Thanks for sharing that. To follow-up on recent emails...

When you start to push the limits of your own test equipment it's good to 
employ tricks such as 3-corner hat in order to get a few dB better measurement. 
But there's a limit to that. And you probably don't want me to suggest that you 
run 3 GPSDO, 3 counters and 3 cesiums all simultaneously.

I've attached two plots showing 4+ days of your GPSDO data and 4+ days of a 
TBolt (factory defaults, *untuned*)

bob-gpsdo-3.gif -- Notice how much your GPSDO (blue trace) wanders all over the 
place.

bob-gpsdo-5.gif -- ADEV comparison. See below for comments.

1)
When I look at the ADEV for your data set it's pretty clear that the limiting 
factor on the left (short tau) is the resolution of your 5370A counter. That's 
why the TBolt looks better. Don't worry about that.

2)
In the middle of the ADEV plot it would appear that both your 5370A counter and 
your PRS-45A cesium reference are sufficiently good to properly measure your 
GPSDO. That's good. The TBolt looks bad in the middle but t

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Bob,
What I should have asked is this: "how do I get that from a Timelab dataset?"   
Bob


  From: Bob kb8tq <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
Cc: Tom Van Baak <t...@leapsecond.com>
 Sent: Wednesday, May 3, 2017 7:20 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi
RMS:
https://en.wikipedia.org/wiki/Root_mean_square
When we talk about things like “6 sigma” in QA, the sigma is the RMS. 
Bob

On May 3, 2017, at 1:44 AM, Bob Stewart <b...@evoria.net> wrote:
Hi Tom,
Could you clarify the term RMS?  Is there some sort of calculation I need to do 
on the raw data to get the RMS value?
I'm going to begin by doing a fresh 8 hour test of GPSDO Unit 1 vs GPSDO Unit 
2, with the same conditions as the tests involving the PRS.  IOW, the 5370 is 
being clocked by GPSDO Unit 2, and the trigger for the EXT input to the 5370 is 
from GPSDO Unit 2.  START is from GSPDO Unit 1 and STOP is from GPSDO Unit 2.  
The ones I have on hand show about 4E-11 at 1s tau.  

After that, I'll run an 8 hour test of raw 1PPS from a LEA-6T against the PRS.  
Since I don't really trust the PRS, I'll use GPSDO Unit 2 to clock the 5370.  
If you really don't want the GSPDO to clock the 5370, I'll run the same test 
using the internal 10811 as the clock, to compare the difference.

I also ran into an old test of the 5370 where START (10MHz) was fed by a GPSDO 
and STOP (10MHz) was fed by the same GPSDO but with (I think) a 20 ft cable 
from START to STOP.  I'll probably want to rerun that, as well, but it was an 
almost straight line from 2E-11 at 1s tau in that dataset.  Still, that test 
will verify that the 5370 hasn't degraded. Bob

  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Wednesday, May 3, 2017 12:02 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?

Hi BobS,


I've also made the timelab file (compressed by 7z) available here:
http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z


Thanks for sharing that. To follow-up on recent emails...

When you start to push the limits of your own test equipment it's good to 
employ tricks such as 3-corner hat in order to get a few dB better measurement. 
But there's a limit to that. And you probably don't want me to suggest that you 
run 3 GPSDO, 3 counters and 3 cesiums all simultaneously.

I've attached two plots showing 4+ days of your GPSDO data and 4+ days of a 
TBolt (factory defaults, *untuned*)

bob-gpsdo-3.gif -- Notice how much your GPSDO (blue trace) wanders all over the 
place.

bob-gpsdo-5.gif -- ADEV comparison. See below for comments.

1)
When I look at the ADEV for your data set it's pretty clear that the limiting 
factor on the left (short tau) is the resolution of your 5370A counter. That's 
why the TBolt looks better. Don't worry about that.

2)
In the middle of the ADEV plot it would appear that both your 5370A counter and 
your PRS-45A cesium reference are sufficiently good to properly measure your 
GPSDO. That's good. The TBolt looks bad in the middle but that's simply because 
it was using a way-too-short default time constant. With proper tuning the red 
trace would be mostly flat out to 1000 seconds.

3)
>From the look of the phase plot and the ADEV plot it almost seems to me like 
>your PRS-45A is the limiting factor on the right (long tau). If so, it would 
>explain the lack of diurnal and sidereal effects in your data. If you look at:
http://leapsecond.com/pages/tbolt-8d/sigma1.gif from 
http://www.leapsecond.com/pages/tbolt-8d/
you'll note the sidereal "blip" is below 4e-14. Your ADEV doesn't get near that 
level.


I say this because a rule-of-thumb is that a good M12+T timing receiver should 
get you down to 3 ns per day RMS. And a good ublox-6T can get you to 3 or 2 ns 
per day RMS. Your data shows something more like 5 ns -- which for a GPSDO is 
worse than no GPSDO at all. So something's wrong. What set of experiments can 
you perform to locate the problem? Or, what experiments can you perform that 
don't require buying expensive gear?

My first suggestion is for you run a standalone GPS timing receiver like a 
M12+T or ublox-6. Put all your GPSDO away. Just use that OEM board, and your 
TIC, and your PRS-45A. Collect sawtooth data too. You should get down to 2 or 3 
ns RMS.

/tvb

- Original Message - 
From: "Bob Stewart" <b...@evoria.net>
To: "Discussion of Precise Time and Frequency Measurement" 
<time-nuts@febo.com>; "Magnus Danielson" <mag...@rubidium.se>
Sent: Thursday, April 27, 2017 9:48 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?


Hi Magnus,
Try as I might, the weather and the local power company had other ideas about 
my long term capture. I'm running everything but the 5370 from a UPS. I guess 
I

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Jim,
I'm not sure you're plotting what you think you are, but perhaps I 
misunderstood.  The phase error data contains both the position uncertainty of 
the Adafruit (constellation, ionosphere, etc) and an error caused by correcting 
the OCXO using that phase error.  IOW, the fact that the phase error puts the 
OCXO back in phase is problematic.

You might think about disconnecting the EFC from the OCXO and feeding the OCXO 
directly with a fixed voltage derived from the VRef output of the OCXO, 
assuming it has one.  Then, carefully adjust the VRef voltage so that the phase 
error changes very slowly.  Let it cook for a few days and restabilize, then 
start logging your phase error.  Feed that to Timelab and see what the plot 
looks like.  Timelab should be able to remove the aging, so that you wind up 
with a plot that's mostly the Adafruit.  Of course, that depends on which OCXO 
you're using.  I've had good luck with the Trimble 34310-Ts that are about $20 
each depending on the vendor.

Bob 

  From: Jim Harman <j99har...@gmail.com>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Saturday, April 29, 2017 9:15 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   

On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart <b...@evoria.net> wrote:

So, back to my question:  Where are the large ionospheric phase moves?  This 
question has been causing me doubt since I started on this project.  Or don't I 
still have enough data collected for this to happen?

Bob

Bob, my test setup is a good deal simpler than yours, but attached is a plot 
that I think shows the variations you are looking for quite clearly. This is 
data from my homebrew GPSDO, which uses an Adafruit non-timing GPS module and a 
run-of-the-mill surplus OCXO. The plot records the phase comparator output over 
a period of about 1 week. The time constant of the PLL is 1024 seconds and it 
is plotting the 5-minute average TIC values. 
The full horizontal scale is 24 hours.
The vertical scale shows the data from several days with the traces for 
successive days offset upwards by the equivalent of 40 nsec.
As you can see there is pretty good correlation of the phase error from day to 
day and the wiggles migrate to the left a little, corresponding to the 23:56:04 
siderial repeat time of the GPS constellation.This is with a pretty good 
antenna location, under a shingle roof in the attic. I calculate the day-to-day 
correlation at about 0.8.
Making the time constant larger increases the variations somewhat, because the 
loop does not adjust as much, and they definitely get worse if I use a less 
optimal antenna location.



-- 

--Jim Harman


   
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Re: [time-nuts] Three-cornered hat on timelab?

[Bob Stewart]

Hi Tom,
Could you clarify the term RMS?  Is there some sort of calculation I need to do 
on the raw data to get the RMS value?
I'm going to begin by doing a fresh 8 hour test of GPSDO Unit 1 vs GPSDO Unit 
2, with the same conditions as the tests involving the PRS.  IOW, the 5370 is 
being clocked by GPSDO Unit 2, and the trigger for the EXT input to the 5370 is 
from GPSDO Unit 2.  START is from GSPDO Unit 1 and STOP is from GPSDO Unit 2.  
The ones I have on hand show about 4E-11 at 1s tau.  

After that, I'll run an 8 hour test of raw 1PPS from a LEA-6T against the PRS.  
Since I don't really trust the PRS, I'll use GPSDO Unit 2 to clock the 5370.  
If you really don't want the GSPDO to clock the 5370, I'll run the same test 
using the internal 10811 as the clock, to compare the difference.

I also ran into an old test of the 5370 where START (10MHz) was fed by a GPSDO 
and STOP (10MHz) was fed by the same GPSDO but with (I think) a 20 ft cable 
from START to STOP.  I'll probably want to rerun that, as well, but it was an 
almost straight line from 2E-11 at 1s tau in that dataset.  Still, that test 
will verify that the 5370 hasn't degraded. Bob

  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Wednesday, May 3, 2017 12:02 AM
 Subject: Re: [time-nuts] Three-cornered hat on timelab?
   
Hi BobS,

> I've also made the timelab file (compressed by 7z) available here:
> http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z

Thanks for sharing that. To follow-up on recent emails...

When you start to push the limits of your own test equipment it's good to 
employ tricks such as 3-corner hat in order to get a few dB better measurement. 
But there's a limit to that. And you probably don't want me to suggest that you 
run 3 GPSDO, 3 counters and 3 cesiums all simultaneously.

I've attached two plots showing 4+ days of your GPSDO data and 4+ days of a 
TBolt (factory defaults, *untuned*)

bob-gpsdo-3.gif -- Notice how much your GPSDO (blue trace) wanders all over the 
place.

bob-gpsdo-5.gif -- ADEV comparison. See below for comments.

1)
When I look at the ADEV for your data set it's pretty clear that the limiting 
factor on the left (short tau) is the resolution of your 5370A counter. That's 
why the TBolt looks better. Don't worry about that.

2)
In the middle of the ADEV plot it would appear that both your 5370A counter and 
your PRS-45A cesium reference are sufficiently good to properly measure your 
GPSDO. That's good. The TBolt looks bad in the middle but that's simply because 
it was using a way-too-short default time constant. With proper tuning the red 
trace would be mostly flat out to 1000 seconds.

3)
>From the look of the phase plot and the ADEV plot it almost seems to me like 
>your PRS-45A is the limiting factor on the right (long tau). If so, it would 
>explain the lack of diurnal and sidereal effects in your data. If you look at:
http://leapsecond.com/pages/tbolt-8d/sigma1.gif from 
http://www.leapsecond.com/pages/tbolt-8d/
you'll note the sidereal "blip" is below 4e-14. Your ADEV doesn't get near that 
level.


I say this because a rule-of-thumb is that a good M12+T timing receiver should 
get you down to 3 ns per day RMS. And a good ublox-6T can get you to 3 or 2 ns 
per day RMS. Your data shows something more like 5 ns -- which for a GPSDO is 
worse than no GPSDO at all. So something's wrong. What set of experiments can 
you perform to locate the problem? Or, what experiments can you perform that 
don't require buying expensive gear?

My first suggestion is for you run a standalone GPS timing receiver like a 
M12+T or ublox-6. Put all your GPSDO away. Just use that OEM board, and your 
TIC, and your PRS-45A. Collect sawtooth data too. You should get down to 2 or 3 
ns RMS.

/tvb

----- Original Message - 
From: "Bob Stewart" <b...@evoria.net>
To: "Discussion of Precise Time and Frequency Measurement" 
<time-nuts@febo.com>; "Magnus Danielson" <mag...@rubidium.se>
Sent: Thursday, April 27, 2017 9:48 AM
Subject: Re: [time-nuts] Three-cornered hat on timelab?


Hi Magnus,
Try as I might, the weather and the local power company had other ideas about 
my long term capture. I'm running everything but the 5370 from a UPS. I guess 
I'm going to have to get batteries for my other UPS and run the 5370 from that. 
A one second power loss was all it took to stop the test.

Anyway, I did manage to get 376,238 points of data. The data is captured on a 
5370A. The external clock input and the STOP channel are fed by the 10MHz from 
my PRS-45A. The START channel is fed by the 10MHz from one of my GPSDOs. The 
EXT channel is fed by the 1PPS from another of my GPSDO units. "EXT ARM" is 
enabled. So, essentially, at every 1PPS pulse, the phase difference between the 
two 10MHz feeds is captured.

I've attached a screenshot of the ph