SW
Skip Withrow
Thu, Sep 28, 2017 8:18 PM
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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br />
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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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br />
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RK
Rob Kimberley
Fri, Sep 29, 2017 1:13 PM
I'd go with a power surge as it's so regular at 8AM.
Rob
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table style="border-top: 1px solid #D3D4DE;">
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I'd go with a power surge as it's so regular at 8AM.
Rob
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table style="border-top: 1px solid #D3D4DE;">
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Didier Juges
Fri, Sep 29, 2017 1:53 PM
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" robkimberley@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-bounces@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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table
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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" <robkimberley@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-bounces@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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table
> style="border-top: 1px solid #D3D4DE;">
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BB
Bob Bownes
Fri, Sep 29, 2017 1:54 PM
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 robkimberley@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-bounces@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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table
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and follow the instructions there.
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 <robkimberley@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-bounces@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<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br /> <table
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J
jimlux
Fri, Sep 29, 2017 3:42 PM
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<grin>)
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.
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<grin>)
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.
BK
Bob kb8tq
Fri, Sep 29, 2017 3:50 PM
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 jimlux@earthlink.net 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<grin>)
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.
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.
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 <jimlux@earthlink.net> 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<grin>)
>
> 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.
> _______________________________________________
> 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.
LW
Lars Walenius
Fri, Sep 29, 2017 9:20 PM
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 20000 secs time constant? As the frequency seems to be off 0.7ppb the excursion to about 6-7 us with a 20000sec 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 Withrowmailto:skip.withrow@gmail.com
Skickat: den 28 september 2017 22:25
Till: time-nutsmailto: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?
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 20000 secs time constant? As the frequency seems to be off 0.7ppb the excursion to about 6-7 us with a 20000sec 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.withrow@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?
CS
Charles Steinmetz
Sat, Sep 30, 2017 6:29 AM
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
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
JH
John Hawkinson
Sat, Sep 30, 2017 6:35 AM
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?
--jhawk@mit.edu
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?
--jhawk@mit.edu
John Hawkinson
LW
Lars Walenius
Sat, Sep 30, 2017 6:43 AM
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 20000 secs time constant? As the frequency seems to be off 0.7ppb the excursion to about 6-7 us with a 20000sec 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 Withrowmailto:skip.withrow@gmail.com
Sent: den 28 september 2017 22:25
To: time-nutsmailto: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?
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 20000 secs time constant? As the frequency seems to be off 0.7ppb the excursion to about 6-7 us with a 20000sec 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.withrow@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?
