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

[Tom Van Baak]

Hi Orin,

More info... If you try to manually remove the 25 ns glitches you get a data 
set that looks much better. Attached are the ADEV plots for (1) your raw data 
and (2) your data minus those 8 glitches. You can see the dramatic difference 
that just 8 points make. Blue is raw data, red is data without those 8 glitches.

Now, this is not likely your fault. Also, I'm not saying we know yet what 
causes the glitches. This posting is merely to show how 8 bad points out of 
8,000 points can totally mess up an ADEV plot.

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

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

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

[Tom Van Baak]

> I have sent a couple of files to Tom.  They were taken simultaneously from
> an LTE Lite - one from the PPS and one from a PicDiv dividing the 10MHz to
> 1Hz.  The glitches were on the PPS trace, but not on the PicDiv trace, so
> I'm fairly confident the TICC was working correctly.
> 
> Orin.

Hi Orin,

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

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

24.575
24.724
24.831
25.047
25.087
25.549
25.589
49.623

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

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

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

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

[DaveH]

USB is not tied to anything specific so that could well be the case.

Another interest of mine is CNC machining (mill conversion and looking at a
Chinese laser) using MACH3 software. People have tried everything to get the
motors to run from a USB connection as machines with parallel ports are
getting rare. No success at all. A couple of companies are using an Ethernet
connection from the host computer to their own CPU board
(https://www.poscope.com/) - this works great. USB no.

Dave

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf 
> Of Tom McDermott
> Sent: Sunday, March 19, 2017 15:00
> To: Discussion of precise time and frequency measurement
> Cc: gandal...@aol.com
> Subject: Re: [time-nuts] ADEV query Timelab and TICC
> 
> I had this happen this morning. (Running Windows 10). Had 7 
> hours of good
> data
> running overnight, (good ADEV, Freq Diff plots).
> 
> Then There was a big pop' in the frequency difference trace. 
> ADEV messed up
> suddenly.
> 
> It happened coincident with starting up Microsoft Edge (which 
> had not been
> run
> since the start of the data run).  My guess is that perhaps 
> Windows got too
> busy
> and USB samples were dropped.
> 
> -- Tom, N5EG
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Re: [time-nuts] ADEV query Timelab and TICC

[John Ackermann N8UR]

I saw a similar higher-than-expected ADEV from another user who was measuring 
GPSDO PPS vs. 10 MHz from the same GPSDO.  Using a T2-Mini  from the 10 MHz 
yields the expected results.

I suspect that the GPSDO PPS in that unit is derived from GPS PPS rather than 
the OCXO, and thus is noisier in the short term than might otherwise be 
expected.

John

PS -- we just got into our new house and still don't have internet access, so 
I've not been on line as much as usual.  another few days and things should!D 
be getting back to normal.



On Mar 19, 2017, 8:01 PM, at 8:01 PM, Orin Eman  wrote:
>On Sun, Mar 19, 2017 at 3:00 PM, Tom Van Baak 
>wrote:
>
>> > I've seen similar with my TICC when observing a PPS - can't
>remember
>> > whether the PPS was from the Thunderbolt or LTE Lite.
>> >
>> > There was a distinct glitch on the frequency plot when it happened
>and it
>> > was pretty easy in timelab to expand the trace around the glitch to
>take
>> a
>> > better look.
>>
>> Orin -- Thanks for that report. If you still have the TIM file, can
>you
>> send it to me?
>>
>
>
>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.
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Re: [time-nuts] ADEV query Timelab and TICC

[Orin Eman]

On Sun, Mar 19, 2017 at 3:00 PM, Tom Van Baak  wrote:

> > I've seen similar with my TICC when observing a PPS - can't remember
> > whether the PPS was from the Thunderbolt or LTE Lite.
> >
> > There was a distinct glitch on the frequency plot when it happened and it
> > was pretty easy in timelab to expand the trace around the glitch to take
> a
> > better look.
>
> Orin -- Thanks for that report. If you still have the TIM file, can you
> send it to me?
>


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.
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Re: [time-nuts] Smart Phone time display accuracy...?

[Paul]

On Sun, Mar 19, 2017 at 11:03 AM, Jeremy Nichols  wrote:

> Now, with the right app, my iPad shows -.001 and
> my iPod Touch shows +0.216.
>

It's marginally interesting (or time nutty) to listen to the per second
ticks that can be enabled.  If you have (at least) two devices you can
listen to remote (bluetooth, airplay) audio delay.
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Re: [time-nuts] ADEV query Timelab and TICC

[Tom McDermott]

I had this happen this morning. (Running Windows 10). Had 7 hours of good
data
running overnight, (good ADEV, Freq Diff plots).

Then There was a big pop' in the frequency difference trace. ADEV messed up
suddenly.

It happened coincident with starting up Microsoft Edge (which had not been
run
since the start of the data run).  My guess is that perhaps Windows got too
busy
and USB samples were dropped.

-- Tom, N5EG
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Re: [time-nuts] ADEV query Timelab and TICC

[Tom Van Baak]

> I've seen similar with my TICC when observing a PPS - can't remember
> whether the PPS was from the Thunderbolt or LTE Lite.
> 
> There was a distinct glitch on the frequency plot when it happened and it
> was pretty easy in timelab to expand the trace around the glitch to take a
> better look.

Orin -- Thanks for that report. If you still have the TIM file, can you send it 
to me?

Everyone -- If you do see any anomalies with the new TICC please let me know, 
on- or off-list. A copy of the TIM file (if you use TimeLab) would be useful to 
me. Or if you're just logging the raw ascii output that's fine too. Once we 
collect enough examples we can update the user manual, or FAQ or even the 
firmware.

Anytime you work with an instrument that can measure down to 60 ps 
(single-shot) or down to 1 ps (with sufficient over-sampling or averaging) you 
may see things you normally don't see. This includes walking, closing doors, 
sneezing, touching cables or connectors. HVAC, FedEx trucks, sunlight, kids, 
pets, wife are also known to affect measurements at the ps level.

I'm currently running a TICC in TI (Time Interval) mode, in parallel with a hp 
53132 counter in TI mode, in parallel with a TimePod. So it's really easy to 
see when one or the other or both have an issue. For use as a headless time 
interval counter, John's TICC is living up to its goal of an inexpensive 
alternative to a 53131A/53132A.

/tvb
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Re: [time-nuts] Smart Phone time display accuracy...?

[Jeremy Nichols]

Ahh, I got the wrong app. Now, with the right app, my iPad shows -.001 and
my iPod Touch shows +0.216. Thank you!

Jeremy


On Sun, Mar 19, 2017 at 7:01 AM David J Taylor <
david-tay...@blueyonder.co.uk> wrote:

> From: Jeremy Nichols
>
> I have that app but don't see an option to display "the offset between
> NTP time and the device's internal clock." Please guide me.
>
> Jeremy
> =
>
> Jeremy,
>
> Top right corner of the display.  My iPad Pro 9.7 shows +0.003 at the
> moment.
>
> See:
>   https://itunes.apple.com/gb/app/emerald-time/id290384375?mt=8
>
> where it's -0.001
>
> Cheers,
> David
> --
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-tay...@blueyonder.co.uk
> Twitter: @gm8arv
>
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-- 
Sent from Gmail Mobile
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Re: [time-nuts] Smart Phone time display accuracy...?

[Denny Page]

As noted, the device clock’s offset from the current best estimate of correct 
time is on the second line at the far right. The line that begins with “24”, 
“AM” or “PM.”

If you tap on the offset, it will trigger a re-sync of NTP time. The offset can 
be based on a single NTP server, so it may bounce around by several ms each 
time you re-sync.

-Denny

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

[Bob kb8tq]

Hi

It’s a pretty good bet that the “upper” trace has a noise pop in it. One of the 
wonderful things about ADEV is that a single 
noise event can impact the whole curve. That is a bit non-intuitive. It is 
indeed how the math works and how the testing
comes out in the real world.

Bob



> On Mar 19, 2017, at 12:08 PM, GandalfG8--- via time-nuts  
> wrote:
> 
> Yesterday I used one of John's excellent TICC modules for the first  time 
> and initially set up a quick test using the 10MHz output from a  Thunderbolt 
> as the frequency reference to measure the 1PPS from an  Oscilloquartz Star4 
> GPSDO, with the TICC output feeding a USB3 port on a Windows  10 PC running 
> the 64 bit version of Timelab 1.29.
> 
> I'll attach a copy of the test plots I'm referring to but just in  case 
> this doesn't get through I've also uploaded it to
> 
> https://www.mediafire.com/?9bue90yp1e8ueu6
> 
> Using the basic settings as described in the TICC manual the first  run was 
> for 1 hour and seemed fine so I decided to extend the run time to 6  hours. 
> The first 6 hour test started to follow the 1 hour plot as expected and I  
> watched this on and off and can confirm it did so up to somewhere between  
> the 100s and 1000s points on the x-axis, but some time after that the 
> complete  plot shifted upwards and then continued to completion to produce 
> the 
> magenta  trace.
> 
> I wasn't watching when it shifted so don't know if it was a jump or a  
> gradual shift but did see it continue until completion. When I repeated the 6 
>  
> hour test, again without changing anything, and hoping to observe the  effect 
> as it happened, it produced the green trace which was what I'd been  
> expecting to start with. Since then I've made other test runs and again all  
> seems 
> to be as expected.
> 
> I'm probably missing something obvious but don't understand what's  
> happened here so any suggestions would be welcome.
> 
> Throughout the tests I have been simultaneously streaming data  from the 
> Star4 to Lady Heather via a "proper" serial port on the same PC so did  
> wonder 
> if there might be some form of data conflict but it doesn't seem to  have 
> shown up as any obvious form of corruption and hasn't repeated  itself.
> 
> Nigel,  GM8PZR  170318.png>___
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Re: [time-nuts] ADEV query Timelab and TICC

[Orin Eman]

I've seen similar with my TICC when observing a PPS - can't remember
whether the PPS was from the Thunderbolt or LTE Lite.

There was a distinct glitch on the frequency plot when it happened and it
was pretty easy in timelab to expand the trace around the glitch to take a
better look.

I did not see any such problem when dividing the 10MHz to 1PPS with a
PICDIV so I figured it was due to the GPSDO steering the PPS signal as
satellites appear/disappear - my antenna location is far from optimal.

On Sun, Mar 19, 2017 at 12:57 PM, Tom Van Baak  wrote:

> > I'm probably missing something obvious but don't understand what's
> > happened here so any suggestions would be welcome.
>
> Hi Nigel,
>
> Your setup sounds fine. Off-list, send me the TIM files and I'll see what
> happened.
>
> I know we all love ADEV but in general always look at the phase, phase
> residual, and frequency plots first before you bother with ADEV. These
> strip chart plots better show your raw data and measurement. Even a single
> glitch will be visible. Only if these plots are "clean" should you go ahead
> and use ADEV. Another trick is using the TimeLab "Trace" feature which
> splits the data into N segments and computes ADEV for each one
> independently.
>
> But in this particular case where you are comparing two GPSDO a phase
> difference plot will likely be more informative than an ADEV plot anyway.
> You may also want to play around with the averaging value (command 'g').
>
> /tvb
>
> - Original Message -
> From: "GandalfG8--- via time-nuts" 
> To: 
> Sent: Sunday, March 19, 2017 9:08 AM
> Subject: [time-nuts] ADEV query Timelab and TICC
>
>
> > Yesterday I used one of John's excellent TICC modules for the first  time
> > and initially set up a quick test using the 10MHz output from a
> Thunderbolt
> > as the frequency reference to measure the 1PPS from an  Oscilloquartz
> Star4
> > GPSDO, with the TICC output feeding a USB3 port on a Windows  10 PC
> running
> > the 64 bit version of Timelab 1.29.
> >
> > I'll attach a copy of the test plots I'm referring to but just in  case
> > this doesn't get through I've also uploaded it to
> >
> > https://www.mediafire.com/?9bue90yp1e8ueu6
> >
> > Using the basic settings as described in the TICC manual the first  run
> was
> > for 1 hour and seemed fine so I decided to extend the run time to 6
> hours.
> > The first 6 hour test started to follow the 1 hour plot as expected and I
> > watched this on and off and can confirm it did so up to somewhere between
> > the 100s and 1000s points on the x-axis, but some time after that the
> > complete  plot shifted upwards and then continued to completion to
> produce the
> > magenta  trace.
> >
> > I wasn't watching when it shifted so don't know if it was a jump or a
> > gradual shift but did see it continue until completion. When I repeated
> the 6
> > hour test, again without changing anything, and hoping to observe the
> effect
> > as it happened, it produced the green trace which was what I'd been
> > expecting to start with. Since then I've made other test runs and again
> all  seems
> > to be as expected.
> >
> >
> > Throughout the tests I have been simultaneously streaming data  from the
> > Star4 to Lady Heather via a "proper" serial port on the same PC so did
> wonder
> > if there might be some form of data conflict but it doesn't seem to  have
> > shown up as any obvious form of corruption and hasn't repeated  itself.
> >
> > Nigel,  GM8PZR
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Re: [time-nuts] ADEV query Timelab and TICC

[Tom Van Baak]

> I'm probably missing something obvious but don't understand what's  
> happened here so any suggestions would be welcome.

Hi Nigel,

Your setup sounds fine. Off-list, send me the TIM files and I'll see what 
happened.

I know we all love ADEV but in general always look at the phase, phase 
residual, and frequency plots first before you bother with ADEV. These strip 
chart plots better show your raw data and measurement. Even a single glitch 
will be visible. Only if these plots are "clean" should you go ahead and use 
ADEV. Another trick is using the TimeLab "Trace" feature which splits the data 
into N segments and computes ADEV for each one independently.

But in this particular case where you are comparing two GPSDO a phase 
difference plot will likely be more informative than an ADEV plot anyway. You 
may also want to play around with the averaging value (command 'g').

/tvb

- Original Message - 
From: "GandalfG8--- via time-nuts" 
To: 
Sent: Sunday, March 19, 2017 9:08 AM
Subject: [time-nuts] ADEV query Timelab and TICC


> Yesterday I used one of John's excellent TICC modules for the first  time 
> and initially set up a quick test using the 10MHz output from a  Thunderbolt 
> as the frequency reference to measure the 1PPS from an  Oscilloquartz Star4 
> GPSDO, with the TICC output feeding a USB3 port on a Windows  10 PC running 
> the 64 bit version of Timelab 1.29.
> 
> I'll attach a copy of the test plots I'm referring to but just in  case 
> this doesn't get through I've also uploaded it to
> 
> https://www.mediafire.com/?9bue90yp1e8ueu6
> 
> Using the basic settings as described in the TICC manual the first  run was 
> for 1 hour and seemed fine so I decided to extend the run time to 6  hours. 
> The first 6 hour test started to follow the 1 hour plot as expected and I  
> watched this on and off and can confirm it did so up to somewhere between  
> the 100s and 1000s points on the x-axis, but some time after that the 
> complete  plot shifted upwards and then continued to completion to produce 
> the 
> magenta  trace.
> 
> I wasn't watching when it shifted so don't know if it was a jump or a  
> gradual shift but did see it continue until completion. When I repeated the 6 
>  
> hour test, again without changing anything, and hoping to observe the  effect 
> as it happened, it produced the green trace which was what I'd been  
> expecting to start with. Since then I've made other test runs and again all  
> seems 
> to be as expected.
> 
> 
> Throughout the tests I have been simultaneously streaming data  from the 
> Star4 to Lady Heather via a "proper" serial port on the same PC so did  
> wonder 
> if there might be some form of data conflict but it doesn't seem to  have 
> shown up as any obvious form of corruption and hasn't repeated  itself.
> 
> Nigel,  GM8PZR
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[time-nuts] ADEV query Timelab and TICC

[GandalfG8--- via time-nuts]

Yesterday I used one of John's excellent TICC modules for the first  time 
and initially set up a quick test using the 10MHz output from a  Thunderbolt 
as the frequency reference to measure the 1PPS from an  Oscilloquartz Star4 
GPSDO, with the TICC output feeding a USB3 port on a Windows  10 PC running 
the 64 bit version of Timelab 1.29.
 
I'll attach a copy of the test plots I'm referring to but just in  case 
this doesn't get through I've also uploaded it to
 
https://www.mediafire.com/?9bue90yp1e8ueu6
 
Using the basic settings as described in the TICC manual the first  run was 
for 1 hour and seemed fine so I decided to extend the run time to 6  hours. 
The first 6 hour test started to follow the 1 hour plot as expected and I  
watched this on and off and can confirm it did so up to somewhere between  
the 100s and 1000s points on the x-axis, but some time after that the 
complete  plot shifted upwards and then continued to completion to produce the 
magenta  trace.
 
I wasn't watching when it shifted so don't know if it was a jump or a  
gradual shift but did see it continue until completion. When I repeated the 6  
hour test, again without changing anything, and hoping to observe the  effect 
as it happened, it produced the green trace which was what I'd been  
expecting to start with. Since then I've made other test runs and again all  
seems 
to be as expected.
 
I'm probably missing something obvious but don't understand what's  
happened here so any suggestions would be welcome.
 
Throughout the tests I have been simultaneously streaming data  from the 
Star4 to Lady Heather via a "proper" serial port on the same PC so did  wonder 
if there might be some form of data conflict but it doesn't seem to  have 
shown up as any obvious form of corruption and hasn't repeated  itself.
 
Nigel,  GM8PZR 

Star4+ 170318.png
Description: Binary data
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Re: [time-nuts] Best Chance GPS module

[Nick Sayer via time-nuts]

Ok. It wasn’t totally clear from your earlier message what you were looking at, 
but just be aware that the LED pin is just a “blinkenlichten” pin that means 
almost nothing. You have to actually separately look at the PPS pin to see what 
it’s doing. There’s (almost) no connection between the activity on the two pins.


> On Mar 19, 2017, at 2:13 AM, David J Taylor  
> wrote:
> 
>> On Dec 1, 2016, at 7:44 AM, David J Taylor  
>> wrote:
>> 
>> 
>> Venus838LPX-T.   Seems to go into a non-locked state for a proportion of the 
>> time but still emits a PPS signal, which increasingly deviates from true 
>> UTC.  That's using a 25 mm square 28 dB active patch antenna, similar to the 
>> antennas on other similarly located GPS receivers.  This was indoors, on the 
>> top floor of a two-storey building, with just the power fed to it, watching 
>> the LED flash.
>> 
>> Maybe I was unlucky?  I wonder what experience others have?
> 
> From: Nick Sayer via time-nuts
> 
> Was the LED on the PPS pin or on the FIX pin?
> 
> The FIX pin is nothing like the PPS output. Frankly, I’m not 100% sure what 
> the rules are for it. When things are working properly, it blinks at 0.5 Hz, 
> but the leading and trailing edges are something like 120-150 msec after the 
> second. It’s very, very loose. My own interpretation is that the controller 
> flips the bit when it’s got nothing better to do.
> 
> I’ve not witnessed the actual PPS pin being toggled when GPS isn’t available, 
> but it’s not a failure mode I’ve expended a lot of effort to examine.
> ===
> 
> Nick,
> 
> I had to dig out the module to check, but as far as I can tell the LED is 
> connected to pin 7 on the chip, listed as GPIO0/LED on the data sheet. 
> Nominally, navigation status.
> 
> The PPS output which I was monitoring comes from the PPS pin (40) on the chip 
> - GPIO3/P1PPS1
> 
> Cheers,
> David
> -- 
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-tay...@blueyonder.co.uk
> Twitter: @gm8arv 

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Re: [time-nuts] Smart Phone time display accuracy...?

[Glen Hoag]

Look at the line below the live time display. The data elements are the AM/PM 
indicator, a colored dot indicating the quality of the phone's time vs NTP 
time, the local time zone, followed by the offset. It's explained on the 
instructions that come up when you click the info button in the lower right 
corner of the screen. 

Sent from my iPhone

> On Mar 18, 2017, at 16:43, Jeremy Nichols  wrote:
> 
> I have that app but don't see an option to display "the offset between NTP 
> time and the device's internal clock." Please guide me.
> 
> Jeremy
> 
> 
>> On 3/18/2017 9:37 AM, Glen Hoag wrote:
>> On my iPhone, I run an NTP client, Emerald Time, that displays the offset 
>> between NTP time and the device's internal clock.
>> 
>> I'm on T-Mobile US and the offset is typically in the low tens of 
>> milliseconds or better.
>> 
>> It's certainly accurate enough as a clock where all I'm looking at is one 
>> minute resolution.
>> 
>> Glen Hoag
>> h...@hiwaay.net
>> Sent from my iPhone
>> 
>>> On Mar 18, 2017, at 09:52, John Hawkinson  wrote:
>>> 
>>> Chris Albertson  wrote on Fri, 17 Mar 2017
>>> at 14:38:17 -0700 in 
>>> 

Re: [time-nuts] Best Chance GPS module

[David J Taylor]

On Dec 1, 2016, at 7:44 AM, David J Taylor  
wrote:



Venus838LPX-T.   Seems to go into a non-locked state for a proportion of 
the time but still emits a PPS signal, which increasingly deviates from 
true UTC.  That's using a 25 mm square 28 dB active patch antenna, similar 
to the antennas on other similarly located GPS receivers.  This was 
indoors, on the top floor of a two-storey building, with just the power 
fed to it, watching the LED flash.


Maybe I was unlucky?  I wonder what experience others have?


From: Nick Sayer via time-nuts

Was the LED on the PPS pin or on the FIX pin?

The FIX pin is nothing like the PPS output. Frankly, I’m not 100% sure what 
the rules are for it. When things are working properly, it blinks at 0.5 Hz, 
but the leading and trailing edges are something like 120-150 msec after the 
second. It’s very, very loose. My own interpretation is that the controller 
flips the bit when it’s got nothing better to do.


I’ve not witnessed the actual PPS pin being toggled when GPS isn’t 
available, but it’s not a failure mode I’ve expended a lot of effort to 
examine.

===

Nick,

I had to dig out the module to check, but as far as I can tell the LED is 
connected to pin 7 on the chip, listed as GPIO0/LED on the data sheet. 
Nominally, navigation status.


The PPS output which I was monitoring comes from the PPS pin (40) on the 
chip - GPIO3/P1PPS1


Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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Re: [time-nuts] Smart Phone time display accuracy...?

[David J Taylor]

From: Jeremy Nichols

I have that app but don't see an option to display "the offset between
NTP time and the device's internal clock." Please guide me.

Jeremy
=

Jeremy,

Top right corner of the display.  My iPad Pro 9.7 shows +0.003 at the 
moment.


See:
 https://itunes.apple.com/gb/app/emerald-time/id290384375?mt=8

where it's -0.001

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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Re: [time-nuts] Best Chance GPS module

[Nick Sayer via time-nuts]

Was the LED on the PPS pin or on the FIX pin?

The FIX pin is nothing like the PPS output. Frankly, I’m not 100% sure what the 
rules are for it. When things are working properly, it blinks at 0.5 Hz, but 
the leading and trailing edges are something like 120-150 msec after the 
second. It’s very, very loose. My own interpretation is that the controller 
flips the bit when it’s got nothing better to do.

I’ve not witnessed the actual PPS pin being toggled when GPS isn’t available, 
but it’s not a failure mode I’ve expended a lot of effort to examine.

> On Dec 1, 2016, at 7:44 AM, David J Taylor  
> wrote:
> 
> 
> Venus838LPX-T.   Seems to go into a non-locked state for a proportion of the 
> time but still emits a PPS signal, which increasingly deviates from true UTC. 
>  That's using a 25 mm square 28 dB active patch antenna, similar to the 
> antennas on other similarly located GPS receivers.  This was indoors, on the 
> top floor of a two-storey building, with just the power fed to it, watching 
> the LED flash.
> 
> Maybe I was unlucky?  I wonder what experience others have?


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