HM
Hal Murray
Sat, Nov 5, 2016 5:55 PM
At 12 hours of holdover...
I think I'll need a lot more understanding of the impact of aging vs temperature
At that timescale, I'd expect aging to be lost in the noise.
How are you calibrating things?
--
These are my opinions. I hate spam.
> At 12 hours of holdover...
> I think I'll need a lot more understanding of the impact of aging vs temperature
At that timescale, I'd expect aging to be lost in the noise.
How are you calibrating things?
--
These are my opinions. I hate spam.
BS
Bob Stewart
Sat, Nov 5, 2016 6:36 PM
Hi Hal,
I don't think I understand your question. So, I've attached a plot and you can tell me if that gives you anything to work with. This uses my standard plotting script, so there are things you aren't interested in. But, this is a plot of one unit from startup on the night of 10/29 through right now.
The blue band is the plot of the TIC in my GPSDO. The TIC is affected by noise, which is filtered by the PID software, as well as an LPF in the EFC line. So, the OCXO output is much more stable than the blue band would indicate. The red trace (the DAC voltage in hex as read on the left) is what's important for this discussion. Notice the steady decrease in the DAC voltage over time. The orange trace is the temperature. For scaling, use the right side numbers divided by 10 to get delta degrees F. IOW, from 0 to 10 would be a 1 degree Fahrenheit temperature change. Other items of interest on the plot are TDOP, number of sats seen, and number of sats used.
So, looking at the plot, it seems clear that time dominates the change in the DAC voltage. But, there is a noticeable impact from temperature change. That impact is not linear, except that small changes do seem to affect it in a linear manner.
As to how I'm calibrating this: I've got several GPSDOs running. One is being used as the 10MHz reference for the 5370A. Another is being used as the 1PPS reference for the one I'm testing. Since these are essentially identical units, though with different firmware, the impact of ionospheric change on the results is muted. So, what the testing boils down to is bringing up a unit with the firmware to be tested, and allowing it to be well locked before disconnecting the antenna. Generally I leave it overnight and reconnect the antenna some time in the morning. So, this gives me two figures: One is how far the unit drifts over some time period, as well as the rate of recovery once the antenna is restored.
I'd include a Timelab plot except that I don't have the two units skewed enough in time to allow for 1uS of drift. So, the time reported on Timelab would be misleading due to the 5370 slipping into "one sample every two seconds" mode as the phase difference exceeds the time skew. For the next test I think I'll skew the DUT by 2uS so that I can get a clean plot.
Anyway, does any of this answer your question? If not, let me know what's missing.
Bob -----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Hal Murray <hmurray@megapathdsl.net>
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Cc: hmurray@megapathdsl.net
Sent: Saturday, November 5, 2016 12:55 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
At 12 hours of holdover...
I think I'll need a lot more understanding of the impact of aging vs temperature
At that timescale, I'd expect aging to be lost in the noise.
How are you calibrating things?
--
These are my opinions. I hate spam.
Hi Hal,
I don't think I understand your question. So, I've attached a plot and you can tell me if that gives you anything to work with. This uses my standard plotting script, so there are things you aren't interested in. But, this is a plot of one unit from startup on the night of 10/29 through right now.
The blue band is the plot of the TIC in my GPSDO. The TIC is affected by noise, which is filtered by the PID software, as well as an LPF in the EFC line. So, the OCXO output is much more stable than the blue band would indicate. The red trace (the DAC voltage in hex as read on the left) is what's important for this discussion. Notice the steady decrease in the DAC voltage over time. The orange trace is the temperature. For scaling, use the right side numbers divided by 10 to get delta degrees F. IOW, from 0 to 10 would be a 1 degree Fahrenheit temperature change. Other items of interest on the plot are TDOP, number of sats seen, and number of sats used.
So, looking at the plot, it seems clear that time dominates the change in the DAC voltage. But, there is a noticeable impact from temperature change. That impact is not linear, except that small changes do seem to affect it in a linear manner.
As to how I'm calibrating this: I've got several GPSDOs running. One is being used as the 10MHz reference for the 5370A. Another is being used as the 1PPS reference for the one I'm testing. Since these are essentially identical units, though with different firmware, the impact of ionospheric change on the results is muted. So, what the testing boils down to is bringing up a unit with the firmware to be tested, and allowing it to be well locked before disconnecting the antenna. Generally I leave it overnight and reconnect the antenna some time in the morning. So, this gives me two figures: One is how far the unit drifts over some time period, as well as the rate of recovery once the antenna is restored.
I'd include a Timelab plot except that I don't have the two units skewed enough in time to allow for 1uS of drift. So, the time reported on Timelab would be misleading due to the 5370 slipping into "one sample every two seconds" mode as the phase difference exceeds the time skew. For the next test I think I'll skew the DUT by 2uS so that I can get a clean plot.
Anyway, does any of this answer your question? If not, let me know what's missing.
Bob -----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Hal Murray <hmurray@megapathdsl.net>
To: Bob Stewart <bob@evoria.net>; Discussion of precise time and frequency measurement <time-nuts@febo.com>
Cc: hmurray@megapathdsl.net
Sent: Saturday, November 5, 2016 12:55 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
> At 12 hours of holdover...
> I think I'll need a lot more understanding of the impact of aging vs temperature
At that timescale, I'd expect aging to be lost in the noise.
How are you calibrating things?
--
These are my opinions. I hate spam.
BS
Bob Stewart
Sat, Nov 5, 2016 6:47 PM
Oh dear. I attached the wrong file. Here's the correct one.
-----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
Oh dear. I attached the wrong file. Here's the correct one.
-----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
SS
Scott Stobbe
Sun, Nov 6, 2016 1:38 AM
I think that's a nice plot, it looks like you have stepped 160 LSB over 7
days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart bob@evoria.net wrote:
Oh dear. I attached the wrong file. Here's the correct one.
AE6RV.com
GFS GPSDO list:
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and follow the instructions there.
I think that's a nice plot, it looks like you have stepped 160 LSB over 7
days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
> Oh dear. I attached the wrong file. Here's the correct one.
> -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
BS
Bob Stewart
Sun, Nov 6, 2016 1:57 AM
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
Bob -----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart bob@evoria.net wrote:
Oh dear. I attached the wrong file. Here's the correct one.
----------------------------- ------------------------------ ------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts
and follow the instructions there.
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
Bob -----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Bob Stewart <bob@evoria.net>; Discussion of precise time and frequency measurement <time-nuts@febo.com>
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
Oh dear. I attached the wrong file. Here's the correct one.
----------------------------- ------------------------------ ------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
______________________________ _________________
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To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts
and follow the instructions there.
SS
Scott Stobbe
Sun, Nov 6, 2016 2:19 AM
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC
range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is
~1PPT. So, if everything else is stable the DAC code reflects
changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz).
I don't do these calculations every day, but that's about 4.5PPT?
Bob
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net; Discussion of precise time and
frequency measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7
days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart bob@evoria.net wrote:
Oh dear. I attached the wrong file. Here's the correct one.
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC
range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is
~1PPT. So, if everything else is stable the DAC code reflects
changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <bob@evoria.net> wrote:
> Hi Scott,
>
> The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz).
> I don't do these calculations every day, but that's about 4.5PPT?
>
> Bob
>
> -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
>
>
> ------------------------------
> *From:* Scott Stobbe <scott.j.stobbe@gmail.com>
> *To:* Bob Stewart <bob@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
> *Sent:* Saturday, November 5, 2016 8:38 PM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> I think that's a nice plot, it looks like you have stepped 160 LSB over 7
> days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
>
> On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
>
> Oh dear. I attached the wrong file. Here's the correct one.
> ----------------------------- ------------------------------ ------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma>
>
>
>
>
> ______________________________ _________________
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>
>
>
>
>
BS
Bob Stewart
Sun, Nov 6, 2016 2:43 AM
Hi Scott,
D'oh. Thanks for the correction! Like I said, I don't do these calculations often.
If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit stumped. I do have an op-amp in the EFC string with a voltage divider for gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says they're temperature stable to 25PPM/C, but of course they don't mention an aging rate. I don't really see anything else, other than the OCXO, that is likely to be prone to a linear type of aging. The aging rate appears to be stable from unit to unit, so naturally I considered the OCXO first.
There is one other bit in the EFC string that might be controversial, but I don't see that it would be a candidate for the symptoms of aging.
Bob
-----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Bob Stewart bob@evoria.net
Cc: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 9:19 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is ~1PPT. So, if everything else is stable the DAC code reflects changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
Bob ------------------------------ ------------------------------ -----
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart bob@evoria.net wrote:
Oh dear. I attached the wrong file. Here's the correct one.
----------------------------- ------------------------------ ------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts
and follow the instructions there.
Hi Scott,
D'oh. Thanks for the correction! Like I said, I don't do these calculations often.
If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit stumped. I do have an op-amp in the EFC string with a voltage divider for gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says they're temperature stable to 25PPM/C, but of course they don't mention an aging rate. I don't really see anything else, other than the OCXO, that is likely to be prone to a linear type of aging. The aging rate appears to be stable from unit to unit, so naturally I considered the OCXO first.
There is one other bit in the EFC string that might be controversial, but I don't see that it would be a candidate for the symptoms of aging.
Bob
-----------------------------------------------------------------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Bob Stewart <bob@evoria.net>
Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
Sent: Saturday, November 5, 2016 9:19 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is ~1PPT. So, if everything else is stable the DAC code reflects changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <bob@evoria.net> wrote:
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
Bob ------------------------------ ------------------------------ -----
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Bob Stewart <bob@evoria.net>; Discussion of precise time and frequency measurement <time-nuts@febo.com>
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
Oh dear. I attached the wrong file. Here's the correct one.
----------------------------- ------------------------------ ------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
______________________________ _________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts
and follow the instructions there.
SS
Scott Stobbe
Sun, Nov 6, 2016 4:01 AM
Well bob's comments & caution are accurate, everything drifts. In your
case, if the OCXO is rock solid then you would see a 160 PPM change on the
EFC line over 7 days which is a 1mV change on your 6 V full scale, which is
fairly easy to measure if you have a 6 1/2 digit DMM.
On Sat, Nov 5, 2016 at 10:43 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
D'oh. Thanks for the correction! Like I said, I don't do these
calculations often.
If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
stumped. I do have an op-amp in the EFC string with a voltage divider for
gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says
they're temperature stable to 25PPM/C, but of course they don't mention an
aging rate. I don't really see anything else, other than the OCXO, that is
likely to be prone to a linear type of aging. The aging rate appears to be
stable from unit to unit, so naturally I considered the OCXO first.
There is one other bit in the EFC string that might be controversial, but
I don't see that it would be a candidate for the symptoms of aging.
Bob
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net
Cc: Discussion of Precise Time and Frequency Measurement <
time-nuts@febo.com>
Sent: Saturday, November 5, 2016 9:19 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
is ~1PPT. So, if everything else is stable the DAC code reflects
changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz).
I don't do these calculations every day, but that's about 4.5PPT?
Bob
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net; Discussion of precise time and
frequency measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7
days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart bob@evoria.net wrote:
Oh dear. I attached the wrong file. Here's the correct one.
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Well bob's comments & caution are accurate, everything drifts. In your
case, if the OCXO is rock solid then you would see a 160 PPM change on the
EFC line over 7 days which is a 1mV change on your 6 V full scale, which is
fairly easy to measure if you have a 6 1/2 digit DMM.
On Sat, Nov 5, 2016 at 10:43 PM, Bob Stewart <bob@evoria.net> wrote:
> Hi Scott,
>
> D'oh. Thanks for the correction! Like I said, I don't do these
> calculations often.
>
> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
> stumped. I do have an op-amp in the EFC string with a voltage divider for
> gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says
> they're temperature stable to 25PPM/C, but of course they don't mention an
> aging rate. I don't really see anything else, other than the OCXO, that is
> likely to be prone to a linear type of aging. The aging rate appears to be
> stable from unit to unit, so naturally I considered the OCXO first.
>
> There is one other bit in the EFC string that might be controversial, but
> I don't see that it would be a candidate for the symptoms of aging.
>
> Bob
>
>
> -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>
> ------------------------------
> *From:* Scott Stobbe <scott.j.stobbe@gmail.com>
> *To:* Bob Stewart <bob@evoria.net>
> *Cc:* Discussion of Precise Time and Frequency Measurement <
> time-nuts@febo.com>
> *Sent:* Saturday, November 5, 2016 9:19 PM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
> EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
> is ~1PPT. So, if everything else is stable the DAC code reflects
> changes solely due to the OCXO, which would be an aging of 24 PPT/day.
>
> On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <bob@evoria.net> wrote:
>
> Hi Scott,
>
> The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz).
> I don't do these calculations every day, but that's about 4.5PPT?
>
> Bob
>
> ------------------------------ ------------------------------ -----
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma>
>
>
>
>
> ------------------------------
> *From:* Scott Stobbe <scott.j.stobbe@gmail.com>
> *To:* Bob Stewart <bob@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
> *Sent:* Saturday, November 5, 2016 8:38 PM
> *Subject:* Re: [time-nuts] Thermal impact on OCXO
>
> I think that's a nice plot, it looks like you have stepped 160 LSB over 7
> days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
>
> On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
>
> Oh dear. I attached the wrong file. Here's the correct one.
> ----------------------------- ------------------------------ ------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma>
>
>
>
>
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> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>
>
>
>
>
>
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>
BC
Bob Camp
Mon, Nov 7, 2016 12:08 PM
On Nov 5, 2016, at 10:43 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
D'oh. Thanks for the correction! Like I said, I don't do these calculations often.
If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit stumped. I do have an op-amp in the EFC string with a voltage divider for gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says they're temperature stable to 25PPM/C, but of course they don't mention an aging rate. I don't really see anything else, other than the OCXO, that is likely to be prone to a linear type of aging.
OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig into the FCS papers there are various
curves proposed as models. Mil-O-55310 has one of them as the “official” approach. All of them have the basic
issue of mistakenly fitting to to short a time constraint.
Bob
The aging rate appears to be stable from unit to unit, so naturally I considered the OCXO first.
There is one other bit in the EFC string that might be controversial, but I don't see that it would be a candidate for the symptoms of aging.
Bob
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Bob Stewart bob@evoria.net
Cc: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 9:19 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is ~1PPT. So, if everything else is stable the DAC code reflects changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
Bob ------------------------------ ------------------------------ -----
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart bob@evoria.net wrote:
Oh dear. I attached the wrong file. Here's the correct one.
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
> On Nov 5, 2016, at 10:43 PM, Bob Stewart <bob@evoria.net> wrote:
>
> Hi Scott,
> D'oh. Thanks for the correction! Like I said, I don't do these calculations often.
>
> If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit stumped. I do have an op-amp in the EFC string with a voltage divider for gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says they're temperature stable to 25PPM/C, but of course they don't mention an aging rate. I don't really see anything else, other than the OCXO, that is likely to be prone to a linear type of aging.
OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you dig into the FCS papers there are various
curves proposed as models. Mil-O-55310 has one of them as the “official” approach. All of them have the basic
issue of mistakenly fitting to to short a time constraint.
Bob
> The aging rate appears to be stable from unit to unit, so naturally I considered the OCXO first.
>
> There is one other bit in the EFC string that might be controversial, but I don't see that it would be a candidate for the symptoms of aging.
>
> Bob
> -----------------------------------------------------------------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> From: Scott Stobbe <scott.j.stobbe@gmail.com>
> To: Bob Stewart <bob@evoria.net>
> Cc: Discussion of Precise Time and Frequency Measurement <time-nuts@febo.com>
> Sent: Saturday, November 5, 2016 9:19 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
>
> If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is ~1PPT. So, if everything else is stable the DAC code reflects changes solely due to the OCXO, which would be an aging of 24 PPT/day.
> On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <bob@evoria.net> wrote:
>
> Hi Scott,
> The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
> Bob ------------------------------ ------------------------------ -----
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
>
>
>
> From: Scott Stobbe <scott.j.stobbe@gmail.com>
> To: Bob Stewart <bob@evoria.net>; Discussion of precise time and frequency measurement <time-nuts@febo.com>
> Sent: Saturday, November 5, 2016 8:38 PM
> Subject: Re: [time-nuts] Thermal impact on OCXO
>
> I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
> On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
>
> Oh dear. I attached the wrong file. Here's the correct one.
> ----------------------------- ------------------------------ ------
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
>
>
>
> ______________________________ _________________
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
>
>
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
SS
Scott Stobbe
Mon, Nov 7, 2016 3:34 PM
Here is a sample data point taken from
http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf; the first that
showed up on a google search.
Year Aging [PPM] dF/dt [PPT/Day]
1 180.51 63.884
2 196.65 31.93
5 218 12.769
9 231.69 7.0934
10 234.15 6.384
25 255.5 2.5535
If you have a set of coefficients you believe to be representative of your
OCXO, we can give those a go.
On Mon, Nov 7, 2016 at 7:08 AM, Bob Camp kb8tq@n1k.org wrote:
On Nov 5, 2016, at 10:43 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
D'oh. Thanks for the correction! Like I said, I don't do these
If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
stumped. I do have an op-amp in the EFC string with a voltage divider for
gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says
they're temperature stable to 25PPM/C, but of course they don't mention an
aging rate. I don't really see anything else, other than the OCXO, that is
likely to be prone to a linear type of aging.
OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you
dig into the FCS papers there are various
curves proposed as models. Mil-O-55310 has one of them as the “official”
approach. All of them have the basic
issue of mistakenly fitting to to short a time constraint.
Bob
The aging rate appears to be stable from unit to unit, so naturally I
considered the OCXO first.
There is one other bit in the EFC string that might be controversial,
but I don't see that it would be a candidate for the symptoms of aging.
Bob
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Bob Stewart bob@evoria.net
Cc: Discussion of Precise Time and Frequency Measurement <
Sent: Saturday, November 5, 2016 9:19 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
is ~1PPT. So, if everything else is stable the DAC code reflects changes
solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott,
The 20 bits span about 6 volts. The EFC range spans about 8Hz
(+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
Bob ------------------------------ ------------------------------ -----
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
From: Scott Stobbe scott.j.stobbe@gmail.com
To: Bob Stewart bob@evoria.net; Discussion of precise time and
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over
7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
mailman/listinfo/time-nuts
mailman/listinfo/time-nuts
and follow the instructions there.
Here is a sample data point taken from
http://tycho.usno.navy.mil/ptti/1987papers/Vol%2019_16.pdf; the first that
showed up on a google search.
Year Aging [PPM] dF/dt [PPT/Day]
1 180.51 63.884
2 196.65 31.93
5 218 12.769
9 231.69 7.0934
10 234.15 6.384
25 255.5 2.5535
If you have a set of coefficients you believe to be representative of your
OCXO, we can give those a go.
On Mon, Nov 7, 2016 at 7:08 AM, Bob Camp <kb8tq@n1k.org> wrote:
> Hi
>
>
> > On Nov 5, 2016, at 10:43 PM, Bob Stewart <bob@evoria.net> wrote:
> >
> > Hi Scott,
> > D'oh. Thanks for the correction! Like I said, I don't do these
> calculations often.
> >
> > If as Bob Camp implies, the aging isn't from the OXCO, then I'm a bit
> stumped. I do have an op-amp in the EFC string with a voltage divider for
> gain. The resistors are Panasonic ERA-6AEDxxxV resistors. Mouser says
> they're temperature stable to 25PPM/C, but of course they don't mention an
> aging rate. I don't really see anything else, other than the OCXO, that is
> likely to be prone to a linear type of aging.
>
> OCXO’s don’t age in a linear fashion. At least 90% of them don’t. If you
> dig into the FCS papers there are various
> curves proposed as models. Mil-O-55310 has one of them as the “official”
> approach. All of them have the basic
> issue of mistakenly fitting to to short a time constraint.
>
> Bob
>
> > The aging rate appears to be stable from unit to unit, so naturally I
> considered the OCXO first.
> >
> > There is one other bit in the EFC string that might be controversial,
> but I don't see that it would be a candidate for the symptoms of aging.
> >
> > Bob
> > -----------------------------------------------------------------
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> >
> > From: Scott Stobbe <scott.j.stobbe@gmail.com>
> > To: Bob Stewart <bob@evoria.net>
> > Cc: Discussion of Precise Time and Frequency Measurement <
> time-nuts@febo.com>
> > Sent: Saturday, November 5, 2016 9:19 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> >
> > If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the
> EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB
> is ~1PPT. So, if everything else is stable the DAC code reflects changes
> solely due to the OCXO, which would be an aging of 24 PPT/day.
> > On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <bob@evoria.net> wrote:
> >
> > Hi Scott,
> > The 20 bits span about 6 volts. The EFC range spans about 8Hz
> (+/-4Hz). I don't do these calculations every day, but that's about 4.5PPT?
> > Bob ------------------------------ ------------------------------ -----
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> >
> >
> >
> > From: Scott Stobbe <scott.j.stobbe@gmail.com>
> > To: Bob Stewart <bob@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
> > Sent: Saturday, November 5, 2016 8:38 PM
> > Subject: Re: [time-nuts] Thermal impact on OCXO
> >
> > I think that's a nice plot, it looks like you have stepped 160 LSB over
> 7 days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1
> ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely
> due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of
> 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable.
> > On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <bob@evoria.net> wrote:
> >
> > Oh dear. I attached the wrong file. Here's the correct one.
> > ----------------------------- ------------------------------ ------
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
> >
> >
> >
> > ______________________________ _________________
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
>
