Re: [time-nuts] Weird GPSDO behavior - update

[Lars Walenius]

Hello,

If I look on the one hour plot it look like it goes in hold mode due to zero 
used satellites. If my assumption that the light blue graph in the bottom is 
satellites it sees no satellites during about a minute and after that it 
selects a fast time constant. From the TIC offset and DAC changes, a time 
constant of 10-20 secs seems reasonable if it is a PI-loop with a low pass 
filter on the TIC value.

So nothing strange except the jump of the DAC value in hold mode. As always you 
really want to know what the firmware does.

As the satellite constellation is the same every 23h56min I guess it could be 
zero usable satellites every day at about 8am for several days.

Lars


Från: Skip Withrow<mailto:skip.with...@gmail.com>
Skickat: den 4 oktober 2017 03:17
Till: time-nuts<mailto:time-nuts@febo.com>
Ämne: [time-nuts] Weird GPSDO behavior - update

Hello Time-Nuts,

Well, I think I know a little more about my GPSDO problem, but
probably have more questions now than before.  Thanks for all the
replies to the first post with thoughts and suggestions.

I first tried restarting Lady Heather and doing a cold boot on the
NTGS50AA (then entering the same disciplining values). Same behavior.

I let it run over the weekend and the same behavior happened on
Saturday and Sunday morning.

So, yesterday (Monday morning) I changed the gain to the gain of the
oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s.  On
the attached PRS10-2 plot you can see that it quickly settled.  This
morning, it looks like all is well from the plot (about an hour before
the furnace kicks in at the right of the plot).  HOWEVER, when the
plot is expanded there is still funny business going on with the DAC
control voltage at the same time of day.  I just think the changed
parameters limit the disturbance.  The expanded plot is the attached
PRS10-1.

At this point I'm beginning to think that the NTGS50AA is the issue,
but there are lots of questions left.

1. There are various version of the NTBW50AA/NTGS50AA GPS/operating
firmware.  Mine is 10.3 and I notice that it has the LH 'ro'
designation (as does the 10.4 version).  The 10.5 version does not
give the LH ro notice.  Maybe it behaves better with the disciplining?
 I will have to give a 10.5 a try.

2. Why does the glitch occur at 8am in the morning?  Will have to try
powering the NTGS50AA up at different times and see it the glitch
moves around.

3. Which disciplining parameters are affected by this glitch and which are not?

4. Have other people seen this same behavior?  Does it happen on
Thunderbolts too?

I'll update again when I have more data.

Regards,
Skip Withrow

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[time-nuts] Weird GPSDO behavior - update

[Mark Sims]

There is apparently a way to update the Tbolt firmware.  Several years ago a 
Chinese seller of Tbolts was selling units that he upgraded the firmware from 
v2.xx to v3.xx He may have pulled a new firmware chip and dumped the image 
and re-programmed the older ones externally or used JTAG,  but that seems like 
a lot of work for minimal gain.

-

> I'm aware (until now) that there is no firmware around and no firmware 
> flashing tool for
these GPSes. Maybe the flashing tool(s) is(are) suitable for the
Thunderbolt too.
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Re: [time-nuts] Weird GPSDO behavior - update

[Tim Shoppa]

Is there a way you can force your currently disciplined oscillator to
free-run, and log the phase difference between oscillator and GPS over a
couple of days?

Tim N3QE

On Tue, Oct 3, 2017 at 2:15 PM, Skip Withrow  wrote:

> Hello Time-Nuts,
>
> Well, I think I know a little more about my GPSDO problem, but
> probably have more questions now than before.  Thanks for all the
> replies to the first post with thoughts and suggestions.
>
> I first tried restarting Lady Heather and doing a cold boot on the
> NTGS50AA (then entering the same disciplining values). Same behavior.
>
> I let it run over the weekend and the same behavior happened on
> Saturday and Sunday morning.
>
> So, yesterday (Monday morning) I changed the gain to the gain of the
> oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s.  On
> the attached PRS10-2 plot you can see that it quickly settled.  This
> morning, it looks like all is well from the plot (about an hour before
> the furnace kicks in at the right of the plot).  HOWEVER, when the
> plot is expanded there is still funny business going on with the DAC
> control voltage at the same time of day.  I just think the changed
> parameters limit the disturbance.  The expanded plot is the attached
> PRS10-1.
>
> At this point I'm beginning to think that the NTGS50AA is the issue,
> but there are lots of questions left.
>
> 1. There are various version of the NTBW50AA/NTGS50AA GPS/operating
> firmware.  Mine is 10.3 and I notice that it has the LH 'ro'
> designation (as does the 10.4 version).  The 10.5 version does not
> give the LH ro notice.  Maybe it behaves better with the disciplining?
>  I will have to give a 10.5 a try.
>
> 2. Why does the glitch occur at 8am in the morning?  Will have to try
> powering the NTGS50AA up at different times and see it the glitch
> moves around.
>
> 3. Which disciplining parameters are affected by this glitch and which are
> not?
>
> 4. Have other people seen this same behavior?  Does it happen on
> Thunderbolts too?
>
> I'll update again when I have more data.
>
> Regards,
> Skip Withrow
>
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Re: [time-nuts] Weird GPSDO behavior - update

[Azelio Boriani]

Very interesting: can you flash the firmware? I'm aware (until now)
that there is no firmware around and no firmware flashing tool for
these GPSes. Maybe the flashing tool(s) is(are) suitable for the
Thunderbolt too.

On Wed, Oct 4, 2017 at 10:58 AM, robkimberley
<robkimber...@btinternet.com> wrote:
> Is there any way you can run it on batteries? The 8AM glitch still makes me 
> think it is power line problem.Rob
>
>
> Sent from my Samsung Galaxy smartphone.
>  Original message From: Skip Withrow <skip.with...@gmail.com> 
> Date: 03/10/2017  19:15  (GMT+00:00) To: time-nuts <time-nuts@febo.com> 
> Subject: [time-nuts] Weird GPSDO behavior - update
> Hello Time-Nuts,
>
> Well, I think I know a little more about my GPSDO problem, but
> probably have more questions now than before.  Thanks for all the
> replies to the first post with thoughts and suggestions.
>
> I first tried restarting Lady Heather and doing a cold boot on the
> NTGS50AA (then entering the same disciplining values). Same behavior.
>
> I let it run over the weekend and the same behavior happened on
> Saturday and Sunday morning.
>
> So, yesterday (Monday morning) I changed the gain to the gain of the
> oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s.  On
> the attached PRS10-2 plot you can see that it quickly settled.  This
> morning, it looks like all is well from the plot (about an hour before
> the furnace kicks in at the right of the plot).  HOWEVER, when the
> plot is expanded there is still funny business going on with the DAC
> control voltage at the same time of day.  I just think the changed
> parameters limit the disturbance.  The expanded plot is the attached
> PRS10-1.
>
> At this point I'm beginning to think that the NTGS50AA is the issue,
> but there are lots of questions left.
>
> 1. There are various version of the NTBW50AA/NTGS50AA GPS/operating
> firmware.  Mine is 10.3 and I notice that it has the LH 'ro'
> designation (as does the 10.4 version).  The 10.5 version does not
> give the LH ro notice.  Maybe it behaves better with the disciplining?
>  I will have to give a 10.5 a try.
>
> 2. Why does the glitch occur at 8am in the morning?  Will have to try
> powering the NTGS50AA up at different times and see it the glitch
> moves around.
>
> 3. Which disciplining parameters are affected by this glitch and which are 
> not?
>
> 4. Have other people seen this same behavior?  Does it happen on
> Thunderbolts too?
>
> I'll update again when I have more data.
>
> Regards,
> Skip Withrow
>
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Re: [time-nuts] Weird GPSDO behavior - update

[robkimberley]

Is there any way you can run it on batteries? The 8AM glitch still makes me 
think it is power line problem.Rob


Sent from my Samsung Galaxy smartphone.
 Original message From: Skip Withrow <skip.with...@gmail.com> 
Date: 03/10/2017  19:15  (GMT+00:00) To: time-nuts <time-nuts@febo.com> 
Subject: [time-nuts] Weird GPSDO behavior - update 
Hello Time-Nuts,

Well, I think I know a little more about my GPSDO problem, but
probably have more questions now than before.  Thanks for all the
replies to the first post with thoughts and suggestions.

I first tried restarting Lady Heather and doing a cold boot on the
NTGS50AA (then entering the same disciplining values). Same behavior.

I let it run over the weekend and the same behavior happened on
Saturday and Sunday morning.

So, yesterday (Monday morning) I changed the gain to the gain of the
oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s.  On
the attached PRS10-2 plot you can see that it quickly settled.  This
morning, it looks like all is well from the plot (about an hour before
the furnace kicks in at the right of the plot).  HOWEVER, when the
plot is expanded there is still funny business going on with the DAC
control voltage at the same time of day.  I just think the changed
parameters limit the disturbance.  The expanded plot is the attached
PRS10-1.

At this point I'm beginning to think that the NTGS50AA is the issue,
but there are lots of questions left.

1. There are various version of the NTBW50AA/NTGS50AA GPS/operating
firmware.  Mine is 10.3 and I notice that it has the LH 'ro'
designation (as does the 10.4 version).  The 10.5 version does not
give the LH ro notice.  Maybe it behaves better with the disciplining?
 I will have to give a 10.5 a try.

2. Why does the glitch occur at 8am in the morning?  Will have to try
powering the NTGS50AA up at different times and see it the glitch
moves around.

3. Which disciplining parameters are affected by this glitch and which are not?

4. Have other people seen this same behavior?  Does it happen on
Thunderbolts too?

I'll update again when I have more data.

Regards,
Skip Withrow

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[time-nuts] Weird GPSDO behavior - update

[Skip Withrow]

Hello Time-Nuts,

Well, I think I know a little more about my GPSDO problem, but
probably have more questions now than before.  Thanks for all the
replies to the first post with thoughts and suggestions.

I first tried restarting Lady Heather and doing a cold boot on the
NTGS50AA (then entering the same disciplining values). Same behavior.

I let it run over the weekend and the same behavior happened on
Saturday and Sunday morning.

So, yesterday (Monday morning) I changed the gain to the gain of the
oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s.  On
the attached PRS10-2 plot you can see that it quickly settled.  This
morning, it looks like all is well from the plot (about an hour before
the furnace kicks in at the right of the plot).  HOWEVER, when the
plot is expanded there is still funny business going on with the DAC
control voltage at the same time of day.  I just think the changed
parameters limit the disturbance.  The expanded plot is the attached
PRS10-1.

At this point I'm beginning to think that the NTGS50AA is the issue,
but there are lots of questions left.

1. There are various version of the NTBW50AA/NTGS50AA GPS/operating
firmware.  Mine is 10.3 and I notice that it has the LH 'ro'
designation (as does the 10.4 version).  The 10.5 version does not
give the LH ro notice.  Maybe it behaves better with the disciplining?
 I will have to give a 10.5 a try.

2. Why does the glitch occur at 8am in the morning?  Will have to try
powering the NTGS50AA up at different times and see it the glitch
moves around.

3. Which disciplining parameters are affected by this glitch and which are not?

4. Have other people seen this same behavior?  Does it happen on
Thunderbolts too?

I'll update again when I have more data.

Regards,
Skip Withrow
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Re: [time-nuts] Weird GPSDO behavior

[Lars Walenius]

If I look on the TIC graph it looks like something happen at about + or - 
500ns. Could it be that the software change algoritm? Like a ”Jam Sync”. Seems 
like it tries to get the TIC to zero quick by changing the DAC. Maybe it thinks 
it gets enough close in frequency and stops and goes back to the PI-loop with 
2 secs time constant? As the frequency seems to be off 0.7ppb the excursion 
to about 6-7 us with a 2sec PI-loop make sense and it takes about a day to 
get back in phase (to + or - 500 ns and a new cycle begins).

If the above is correct the parameters for the PI-loop work but not for the 
other ”algoritm” that has a factor of 100 wrong oscillator sensitivity.

Changing to another time constant might give another cycle different from a 
day?? But will not solve the problem I guess.

Best Regards
Lars


From: Skip Withrow<mailto:skip.with...@gmail.com>
Sent: den 28 september 2017 22:25
To: time-nuts<mailto:time-nuts@febo.com>
Subject: [time-nuts] Weird GPSDO behavior

Hello Time-Nuts,

I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
with the OCXO removed and a SRS PRS-10 rubidium oscillator in its
place.  I have been running Lady Heather 5.0 and have changed the
damping, gain, and time constant to give me a 20,000 second time
constant with a damping of .6.  I have attached a Lady Heather screen
shot of the weird behavior.  You can see that my GPS antenna is in a
very none ideal location (window on the west side of the building).

Once per day (about 8am) something disturbs the system.  So, the GPSDO
spends much of its time recovering and never gives me anywhere near
the performance that this system is capable of.  I would think that it
is not the PRS-10 as it has no knowledge of time.  I would also think
that it is not the GPS system or receiver, since the GPS constellation
repeats twice per day.

Kind of the two things that I am left with are a glitch by the power
company every morning (there is some large industrial machinery across
the street (but then I would kind of expect glitches at 8am and 5pm),
and perhaps Lady Heather doing something funny.  This system has been
running for quite some time, I have not tried restarting Lady Heather
yet.

Anybody seen anything like this, or have any good ideas?

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[time-nuts] Weird GPSDO behavior

[Mark Sims]

A couple of things to try...

Turn on the OSC plot (G O) and see what that looks like... usually like a lot 
of noise.   Try with the display filter turned on (like F D 60).

The "&" menu lets you set the disciplining parameters.  It will also bring up a 
display of all the parameters.  You can see what the jamsync threshold id set 
to.  ESC or space should get out of param display mode.
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Re: [time-nuts] Weird GPSDO behavior

[Lars Walenius]

If I look on the TIC graph it looks like something happen at about + or - 
500ns. Could it be that the software change algoritm? Like a ”Jam Sync”. Seems 
like it tries to get the TIC to zero quick by changing the DAC. Maybe it thinks 
it gets enough close in frequency and stops and goes back to the PI-loop with 
2 secs time constant? As the frequency seems to be off 0.7ppb the excursion 
to about 6-7 us with a 2sec PI-loop make sense and it takes about a day to 
get back in phase (to + or - 500 ns and a new cycle begins).

If the above is correct the parameters for the PI-loop work but not for the 
other ”algoritm” that has a factor of 100 wrong oscillator sensitivity.

Changing to another time constant might give another cycle different from a 
day?? But will not solve the problem I guess.

Best Regards
Lars


Från: Skip Withrow<mailto:skip.with...@gmail.com>
Skickat: den 28 september 2017 22:25
Till: time-nuts<mailto:time-nuts@febo.com>
Ämne: [time-nuts] Weird GPSDO behavior

Hello Time-Nuts,

I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
with the OCXO removed and a SRS PRS-10 rubidium oscillator in its
place.  I have been running Lady Heather 5.0 and have changed the
damping, gain, and time constant to give me a 20,000 second time
constant with a damping of .6.  I have attached a Lady Heather screen
shot of the weird behavior.  You can see that my GPS antenna is in a
very none ideal location (window on the west side of the building).

Once per day (about 8am) something disturbs the system.  So, the GPSDO
spends much of its time recovering and never gives me anywhere near
the performance that this system is capable of.  I would think that it
is not the PRS-10 as it has no knowledge of time.  I would also think
that it is not the GPS system or receiver, since the GPS constellation
repeats twice per day.

Kind of the two things that I am left with are a glitch by the power
company every morning (there is some large industrial machinery across
the street (but then I would kind of expect glitches at 8am and 5pm),
and perhaps Lady Heather doing something funny.  This system has been
running for quite some time, I have not tried restarting Lady Heather
yet.

Anybody seen anything like this, or have any good ideas?

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Re: [time-nuts] Weird GPSDO behavior

[Charles Steinmetz]

Skip wrote:


I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
with the OCXO removed and a SRS PRS-10 rubidium oscillator in its place.

Once per day (about 8am) something disturbs the system.  So, the GPSDO
spends much of its time recovering and never gives me anywhere near
the performance that this system is capable of.  I would think that it
is not the PRS-10 as it has no knowledge of time.  I would also think
that it is not the GPS system or receiver, since the GPS constellation
repeats twice per day.


I'm interested in the temperature trace.  If I'm reading the plot 
correctly, it appears that it starts oscillating up and down about 0.5C 
6 or 7 hours from the beginning of the plot, then around the same time 
as the DAC voltage steps it shoots up 5C in 6 or 7 hours with a peak up 
to +6.5C, then falls back to near where it started over ~15 hours, at 
which point the cycle repeats.  According to what we can see, it appears 
that this may be a two-day cycle, with an amplitude of 2 or 3C on "odd" 
days and ~6C on "even" days, but there isn't enough data here to say 
conclusively.


Is this an environmental effect, or self-heating within the '50AA?  6.5C 
seems like an awfully big temperature shift for something indoors, 
unless it is in direct sun. I'm not sure how it relates to the DAC and 
PPS changes, but it seems to be on the same schedule so it appears to be 
related somehow.


In my experience with Tbolts, I have found that damping of 0.6 is WAY 
too low for good performance generally, and *especially* at time 
constants >500s.  I suggest you try damping of 10 or 20.  I'm not 
suggesting that this will fix your problem, but it may, and if not, even 
after you fix what's wrong I'd advise at least trying it.  You can 
always go back.


Finally, you may get better results by putting the OCXO back into the 
GPSDO and then feeding the GPSDO PPS into the PPS synch input of the 
PRS10, rather than having LH try to discipline the PRS10 directly.  I 
have had superb results that way, after playing around with the PRS10's 
internal disciplining routines.  The PRS10 manual gives the relevant 
details.


Best regards,

Charles


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Re: [time-nuts] Weird GPSDO behavior

[John Hawkinson]

I would have thought the easy test is to run the GPSDO on battery power 
(perhaps with a UPS). Maybe that's not so easy?

--jh...@mit.edu
  John Hawkinson
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[time-nuts] Weird GPSDO behavior

[Mark Sims]

It's not anything causing a GPS / tracking outage... the sat count plot does 
not drop to 0.  
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Re: [time-nuts] Weird GPSDO behavior

[Bob kb8tq]

Hi

If a simple GPS outage makes the GPSDO go bonkers, there is something 
else involved. Noise jamming or flying saucers over the antenna should just shut
down the receiver. When it locks back up again, the disciplining should 
resume. If it goes into a death spiral that pretty strongly suggests that the
math isn’t handling things very well. Indeed the math may never have been 
tested for this case so it becomes “that’s the way it is”…..

20,000 seconds is errr …. 5.55 hours. A normal loop could take 10 tau to settle 
to a reasonable level. That would put “bump recovery out around two days. The
sort of checks and tweaks that make sense on a 10 minute tau likely are not the
same for a 5 hour loop … It could indeed be a timeout timer saying “not settled 
in a day? -  reset …”. 

Bob 

> On Sep 29, 2017, at 11:42 AM, jimlux  wrote:
> 
> On 9/29/17 6:13 AM, Rob Kimberley wrote:
>> I'd go with a power surge as it's so regular at 8AM.
>> Rob
> 
> Delivery truck with Jammer, as suggested by Graham also.
> 
> There could be a RFI burst from something like a streetlight or storefront 
> display turning on/off.
> 
> 
> Have you analyzed the timing of the outages?  What sort of distribution do 
> they have? (I hesitate, but this is time-nuts... what is the ADEV of the 
> outage times)
> 
> If the timing is *very* regular - that implies its controlled by a clock
> If the timing slowly drifts later (if you're in the northern hemisphere) then 
> it might be tied to an astronomical timer (e.g. sunrise) or an actual light 
> detector.
> If the timing is sort of random, but around a median, that implies some sort 
> of human scheduled activity.
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Re: [time-nuts] Weird GPSDO behavior

[jimlux]

On 9/29/17 6:13 AM, Rob Kimberley wrote:

I'd go with a power surge as it's so regular at 8AM.
Rob



Delivery truck with Jammer, as suggested by Graham also.

There could be a RFI burst from something like a streetlight or 
storefront display turning on/off.



Have you analyzed the timing of the outages?  What sort of distribution 
do they have? (I hesitate, but this is time-nuts... what is the ADEV of 
the outage times)


If the timing is *very* regular - that implies its controlled by a clock
If the timing slowly drifts later (if you're in the northern hemisphere) 
then it might be tied to an astronomical timer (e.g. sunrise) or an 
actual light detector.
If the timing is sort of random, but around a median, that implies some 
sort of human scheduled activity.

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Re: [time-nuts] Weird GPSDO behavior

[Didier Juges]

Where I work, we had a high power system tripping and occasionally blowing
up at 7:00 AM. It turned out that it was when the power company switched
big capacitors across the lines as businesses got started to keep the power
factor within their target range. It was creating just the kind of
transient that drove the controller loop of the power factor corrector in
our power supply to go bezerk (62kW converter running off 480VAC 3 phase).
The system had been tested to MIL-STD-704 transients and passed, but that
capacitor switching just killed it.

On Sep 29, 2017 8:15 AM, "Rob Kimberley" <robkimber...@btinternet.com>
wrote:

> I'd go with a power surge as it's so regular at 8AM.
> Rob
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Skip
> Withrow
> Sent: 28 September 2017 21:18
> To: time-nuts
> Subject: [time-nuts] Weird GPSDO behavior
>
> Hello Time-Nuts,
>
> I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
> with the OCXO removed and a SRS PRS-10 rubidium oscillator in its place.  I
> have been running Lady Heather 5.0 and have changed the damping, gain, and
> time constant to give me a 20,000 second time constant with a damping of
> .6.  I have attached a Lady Heather screen shot of the weird behavior.  You
> can see that my GPS antenna is in a very none ideal location (window on the
> west side of the building).
>
> Once per day (about 8am) something disturbs the system.  So, the GPSDO
> spends much of its time recovering and never gives me anywhere near the
> performance that this system is capable of.  I would think that it is not
> the PRS-10 as it has no knowledge of time.  I would also think that it is
> not the GPS system or receiver, since the GPS constellation repeats twice
> per day.
>
> Kind of the two things that I am left with are a glitch by the power
> company every morning (there is some large industrial machinery across the
> street (but then I would kind of expect glitches at 8am and 5pm), and
> perhaps Lady Heather doing something funny.  This system has been running
> for quite some time, I have not tried restarting Lady Heather yet.
>
> Anybody seen anything like this, or have any good ideas?
>
> Thanks in advance,
> Skip Withrow  style="border-top: 1px solid #D3D4DE;">
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Re: [time-nuts] Weird GPSDO behavior

[Bob Bownes]

How much jitter is there in the 8am number?

If industrial, I could easily see the first shift coming in and all
starting up at about the same time and shutting things off one by one as
the jobs finish. But I would also expect it to not show up on weekends
and/or holidays, etc. Same applies for the theoretical UPS truck w GPS
jammer. And there could be several minutes of jitter.

If it's very precise, that would be more along the lines of a software
error.

More data! :)





On Fri, Sep 29, 2017 at 9:13 AM, Rob Kimberley <robkimber...@btinternet.com>
wrote:

> I'd go with a power surge as it's so regular at 8AM.
> Rob
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Skip
> Withrow
> Sent: 28 September 2017 21:18
> To: time-nuts
> Subject: [time-nuts] Weird GPSDO behavior
>
> Hello Time-Nuts,
>
> I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
> with the OCXO removed and a SRS PRS-10 rubidium oscillator in its place.  I
> have been running Lady Heather 5.0 and have changed the damping, gain, and
> time constant to give me a 20,000 second time constant with a damping of
> .6.  I have attached a Lady Heather screen shot of the weird behavior.  You
> can see that my GPS antenna is in a very none ideal location (window on the
> west side of the building).
>
> Once per day (about 8am) something disturbs the system.  So, the GPSDO
> spends much of its time recovering and never gives me anywhere near the
> performance that this system is capable of.  I would think that it is not
> the PRS-10 as it has no knowledge of time.  I would also think that it is
> not the GPS system or receiver, since the GPS constellation repeats twice
> per day.
>
> Kind of the two things that I am left with are a glitch by the power
> company every morning (there is some large industrial machinery across the
> street (but then I would kind of expect glitches at 8am and 5pm), and
> perhaps Lady Heather doing something funny.  This system has been running
> for quite some time, I have not tried restarting Lady Heather yet.
>
> Anybody seen anything like this, or have any good ideas?
>
> Thanks in advance,
> Skip Withrow  style="border-top: 1px solid #D3D4DE;">
> 
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Re: [time-nuts] Weird GPSDO behavior

[Didier Juges]

It makes me feel better (not good, just better) to know it's not just me...

On Sep 29, 2017 7:19 AM, "Bob kb8tq"  wrote:

> Hi
>
>
> > On Sep 28, 2017, at 6:59 PM, Mark Sims  wrote:
> >
> > I suspect that it is either temperature related (the funkiness starts
> around when the temperature reaches a minimum) or related to the way the
> disciplining parameters are hacked to get the extended time constant.
>
> Like it or not, most of these devices were made back a while ago.
> The CPU’s used were not the ones we have today. the code was tested
> over the “expected range” of values. Most (but not all) of the control loop
> code was done as integer math. With limited RAM, tossing everything into
> 64 or 128 bit integers was not an option. In some cases 32 bit int’s were
> at
> a premium. Multiply this by that, that, and that. Then divide by
> something, and
> something else. … hmmm…. a few bits just went missing. Could you reorder
> and fiddle to fix some of this? Sure, that’s where we get back to the
> expected
> range stuff.
>
> Even if it’s not in the “main loop”, GPSDO code is full of checks for this
> or that.
> Like the main math, they are scaled and tested for the normal range of
> parameters.
> Not all of them spurt error messages when they get involved. Some just
> bump this
> or that and move on.
>
> Lots of possibilities ….
>
> Bob
>
>
>
> > Try setting up for say a 10,000 second time constant and see how things
> change.
> > ___
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> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
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Re: [time-nuts] Weird GPSDO behavior

[Rob Kimberley]

I'd go with a power surge as it's so regular at 8AM.
Rob

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Skip Withrow
Sent: 28 September 2017 21:18
To: time-nuts
Subject: [time-nuts] Weird GPSDO behavior

Hello Time-Nuts,

I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt) with the 
OCXO removed and a SRS PRS-10 rubidium oscillator in its place.  I have been 
running Lady Heather 5.0 and have changed the damping, gain, and time constant 
to give me a 20,000 second time constant with a damping of .6.  I have attached 
a Lady Heather screen shot of the weird behavior.  You can see that my GPS 
antenna is in a very none ideal location (window on the west side of the 
building).

Once per day (about 8am) something disturbs the system.  So, the GPSDO spends 
much of its time recovering and never gives me anywhere near the performance 
that this system is capable of.  I would think that it is not the PRS-10 as it 
has no knowledge of time.  I would also think that it is not the GPS system or 
receiver, since the GPS constellation repeats twice per day.

Kind of the two things that I am left with are a glitch by the power company 
every morning (there is some large industrial machinery across the street (but 
then I would kind of expect glitches at 8am and 5pm), and perhaps Lady Heather 
doing something funny.  This system has been running for quite some time, I 
have not tried restarting Lady Heather yet.

Anybody seen anything like this, or have any good ideas?

Thanks in advance,
Skip Withrow 

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Re: [time-nuts] Weird GPSDO behavior

[Graham / KE9H]

Could be a delivery truck with a GPS jammer on it, that passes your
location every morning at the same time.

--- Graham

==

On Fri, Sep 29, 2017 at 7:18 AM, Bob kb8tq  wrote:

> Hi
>
>
> > On Sep 28, 2017, at 6:59 PM, Mark Sims  wrote:
> >
> > I suspect that it is either temperature related (the funkiness starts
> around when the temperature reaches a minimum) or related to the way the
> disciplining parameters are hacked to get the extended time constant.
>
> Like it or not, most of these devices were made back a while ago.
> The CPU’s used were not the ones we have today. the code was tested
> over the “expected range” of values. Most (but not all) of the control loop
> code was done as integer math. With limited RAM, tossing everything into
> 64 or 128 bit integers was not an option. In some cases 32 bit int’s were
> at
> a premium. Multiply this by that, that, and that. Then divide by
> something, and
> something else. … hmmm…. a few bits just went missing. Could you reorder
> and fiddle to fix some of this? Sure, that’s where we get back to the
> expected
> range stuff.
>
> Even if it’s not in the “main loop”, GPSDO code is full of checks for this
> or that.
> Like the main math, they are scaled and tested for the normal range of
> parameters.
> Not all of them spurt error messages when they get involved. Some just
> bump this
> or that and move on.
>
> Lots of possibilities ….
>
> Bob
>
>
>
> > Try setting up for say a 10,000 second time constant and see how things
> change.
> > ___
> > 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.
>
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Re: [time-nuts] Weird GPSDO behavior

[Bob kb8tq]

Hi


> On Sep 28, 2017, at 6:59 PM, Mark Sims  wrote:
> 
> I suspect that it is either temperature related (the funkiness starts around 
> when the temperature reaches a minimum) or related to the way the 
> disciplining parameters are hacked to get the extended time constant.  

Like it or not, most of these devices were made back a while ago. 
The CPU’s used were not the ones we have today. the code was tested
over the “expected range” of values. Most (but not all) of the control loop
code was done as integer math. With limited RAM, tossing everything into 
64 or 128 bit integers was not an option. In some cases 32 bit int’s were at
a premium. Multiply this by that, that, and that. Then divide by something, and 
something else. … hmmm…. a few bits just went missing. Could you reorder 
and fiddle to fix some of this? Sure, that’s where we get back to the expected
range stuff. 

Even if it’s not in the “main loop”, GPSDO code is full of checks for this or 
that.
Like the main math, they are scaled and tested for the normal range of 
parameters.
Not all of them spurt error messages when they get involved. Some just bump 
this 
or that and move on. 

Lots of possibilities ….

Bob



> Try setting up for say a 10,000 second time constant and see how things 
> change.
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[time-nuts] Weird GPSDO behavior

[Mark Sims]

I suspect that it is either temperature related (the funkiness starts around 
when the temperature reaches a minimum) or related to the way the disciplining 
parameters are hacked to get the extended time constant.  Try setting up for 
say a 10,000 second time constant and see how things change.
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[time-nuts] Weird GPSDO behavior

[Skip Withrow]

Hello Time-Nuts,

I have a NTGS50AA GPSDO (close cousin to the NTBW50AA and Thunderbolt)
with the OCXO removed and a SRS PRS-10 rubidium oscillator in its
place.  I have been running Lady Heather 5.0 and have changed the
damping, gain, and time constant to give me a 20,000 second time
constant with a damping of .6.  I have attached a Lady Heather screen
shot of the weird behavior.  You can see that my GPS antenna is in a
very none ideal location (window on the west side of the building).

Once per day (about 8am) something disturbs the system.  So, the GPSDO
spends much of its time recovering and never gives me anywhere near
the performance that this system is capable of.  I would think that it
is not the PRS-10 as it has no knowledge of time.  I would also think
that it is not the GPS system or receiver, since the GPS constellation
repeats twice per day.

Kind of the two things that I am left with are a glitch by the power
company every morning (there is some large industrial machinery across
the street (but then I would kind of expect glitches at 8am and 5pm),
and perhaps Lady Heather doing something funny.  This system has been
running for quite some time, I have not tried restarting Lady Heather
yet.

Anybody seen anything like this, or have any good ideas?

Thanks in advance,
Skip Withrow


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