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 -----------------------------------------------------------------
AE6RV.com
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From: Bob Camp <[email protected]>
To: Bob Stewart <[email protected]>; Discussion of precise time and frequency
measurement <[email protected]>
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 <[email protected]> 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:
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>
> From: Scott Stobbe <[email protected]>
> To: Bob Stewart <[email protected]>; Discussion of precise time and frequency
> measurement <[email protected]>
> 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 <[email protected]> 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 <[email protected]>
> To: Discussion of Precise Time and Frequency Measurement <[email protected]>
> 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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