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 <[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
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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
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