Thermal impact on OCXO
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
Bob - AE6RV
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OK, never mind. I see the obvious. Phase changes faster at a higher frequency than it does at a lower frequency.
Bob
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From: Bob Stewart <bob@evoria.net>
To: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Sent: Friday, November 4, 2016 8:56 PM
Subject: [time-nuts] Thermal impact on OCXO
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
Bob - AE6RV
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On 11/4/16 6:56 PM, Bob Stewart wrote:
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
most oscillators exhibit some degree of hysteresis - the mechanical
mounting puts stresses on the crystal, if nothing else.
Hi
You have a first order, second order and third order coefficient to the temperature rate dependance
on a crystal. Since the second order term is a square, it does not care about the sign of the
rate.
Bob
On Nov 4, 2016, at 9:56 PM, Bob Stewart bob@evoria.net wrote:
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
Bob - AE6RV
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Sounds like you already realized this. Phase is the integral of frequency
and the derivative of phase (phase rate) is frequency. So if you go from
nominal frequency - slow - nominal or equivalently nominal frequency - fast
- nominal the phase integrates up/down.
It would be a little more complicated for an ocxo since it is servoing the
xo temperature, you would need to know the disturbance rejection (gain,
time constant for a simple Pi controller) to try and feedfoward correct the
phase error.
On Friday, 4 November 2016, Bob Stewart bob@evoria.net wrote:
OK, never mind. I see the obvious. Phase changes faster at a higher
frequency than it does at a lower frequency.
Bob
AE6RV.com
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From: Bob Stewart <bob@evoria.net <javascript:;>>
To: Discussion of Precise Time and Frequency Measurement <
time-nuts@febo.com javascript:;>
Sent: Friday, November 4, 2016 8:56 PM
Subject: [time-nuts] Thermal impact on OCXO
In the general case, is the impact of changing the ambient temperature
around an OCXO from, say, 40C to 41C the same as changing it from 41C to
40C all else being equal? IOW, if I somehow have the same temperature ramp
over the same time period in both directions, will I wind up with the same
frequency and phase, or will the frequency revert but at some phase
difference?
Bob - AE6RV
AE6RV.com
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Hi Scott and Bob and others,
I keep telling myself that I won't get involved with the temperature problem, and yet for some reason I keep going down that rabbit hole. It seems to me that it's one thing to correct well enough to stay on frequency within some degree of accuracy, and yet another to try to also correct for phase. The reality is that what I have is good enough for now. At 12 hours of holdover, I'm usually a bit over 1uS out of phase. Maybe I could better that, but I think I'll need a lot more understanding of the impact of aging vs temperature before I can get there.
Bob -----------------------------------------------------------------
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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 10:54 AM
Subject: Re: [time-nuts] Thermal impact on OCXO
Sounds like you already realized this. Phase is the integral of frequency and the derivative of phase (phase rate) is frequency. So if you go from nominal frequency - slow - nominal or equivalently nominal frequency - fast - nominal the phase integrates up/down.
It would be a little more complicated for an ocxo since it is servoing the xo temperature, you would need to know the disturbance rejection (gain, time constant for a simple Pi controller) to try and feedfoward correct the phase error.
On Friday, 4 November 2016, Bob Stewart bob@evoria.net wrote:
OK, never mind. I see the obvious. Phase changes faster at a higher frequency than it does at a lower frequency.
Bob
----------------------------- ------------------------------ ------
AE6RV.com
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From: Bob Stewart bob@evoria.net
To: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Sent: Friday, November 4, 2016 8:56 PM
Subject: [time-nuts] Thermal impact on OCXO
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
Bob - AE6RV
----------------------------- ------------------------------ ------
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Hi
Remember - most holdover specs also include a delta temperature (like 40 to 70C) during the
holdover period ….
Bob
On Nov 5, 2016, at 12:15 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott and Bob and others,
I keep telling myself that I won't get involved with the temperature problem, and yet for some reason I keep going down that rabbit hole. It seems to me that it's one thing to correct well enough to stay on frequency within some degree of accuracy, and yet another to try to also correct for phase. The reality is that what I have is good enough for now. At 12 hours of holdover, I'm usually a bit over 1uS out of phase. Maybe I could better that, but I think I'll need a lot more understanding of the impact of aging vs temperature before I can get there.
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 10:54 AM
Subject: Re: [time-nuts] Thermal impact on OCXO
Sounds like you already realized this. Phase is the integral of frequency and the derivative of phase (phase rate) is frequency. So if you go from nominal frequency - slow - nominal or equivalently nominal frequency - fast - nominal the phase integrates up/down.
It would be a little more complicated for an ocxo since it is servoing the xo temperature, you would need to know the disturbance rejection (gain, time constant for a simple Pi controller) to try and feedfoward correct the phase error.
On Friday, 4 November 2016, Bob Stewart bob@evoria.net wrote:
OK, never mind. I see the obvious. Phase changes faster at a higher frequency than it does at a lower frequency.
Bob
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
From: Bob Stewart <bob@evoria.net>
To: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Sent: Friday, November 4, 2016 8:56 PM
Subject: [time-nuts] Thermal impact on OCXO
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
Bob - AE6RV
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Hi Bob,
Ugh! 40C to 70C is not something I plan to deal with. If I were selling to a commercial market, that would be a different story. But at my price point, not gonna happen. But it does bring up the point that I need to have some sort of idea of what I'm willing to manage.
Bob -----------------------------------------------------------------
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From: Bob Camp <kb8tq@n1k.org>
To: Bob Stewart bob@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Saturday, November 5, 2016 11:54 AM
Subject: Re: [time-nuts] Thermal impact on OCXO
Hi
Remember - most holdover specs also include a delta temperature (like 40 to 70C) during the
holdover period ….
Bob
On Nov 5, 2016, at 12:15 PM, Bob Stewart bob@evoria.net wrote:
Hi Scott and Bob and others,
I keep telling myself that I won't get involved with the temperature problem, and yet for some reason I keep going down that rabbit hole. It seems to me that it's one thing to correct well enough to stay on frequency within some degree of accuracy, and yet another to try to also correct for phase. The reality is that what I have is good enough for now. At 12 hours of holdover, I'm usually a bit over 1uS out of phase. Maybe I could better that, but I think I'll need a lot more understanding of the impact of aging vs temperature before I can get there.
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 10:54 AM
Subject: Re: [time-nuts] Thermal impact on OCXO
Sounds like you already realized this. Phase is the integral of frequency and the derivative of phase (phase rate) is frequency. So if you go from nominal frequency - slow - nominal or equivalently nominal frequency - fast - nominal the phase integrates up/down.
It would be a little more complicated for an ocxo since it is servoing the xo temperature, you would need to know the disturbance rejection (gain, time constant for a simple Pi controller) to try and feedfoward correct the phase error.
On Friday, 4 November 2016, Bob Stewart bob@evoria.net wrote:
OK, never mind. I see the obvious. Phase changes faster at a higher frequency than it does at a lower frequency.
Bob
----------------------------- ------------------------------ ------
AE6RV.com
GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info
From: Bob Stewart bob@evoria.net
To: Discussion of Precise Time and Frequency Measurement time-nuts@febo.com
Sent: Friday, November 4, 2016 8:56 PM
Subject: [time-nuts] Thermal impact on OCXO
In the general case, is the impact of changing the ambient temperature around an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else being equal? IOW, if I somehow have the same temperature ramp over the same time period in both directions, will I wind up with the same frequency and phase, or will the frequency revert but at some phase difference?
Bob - AE6RV
----------------------------- ------------------------------ ------
AE6RV.com
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