Thanks Bob. That makes sense.
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From: Bob Camp <[email protected]>
To: Bob Stewart <[email protected]>; Discussion of precise time and frequency
measurement <[email protected]>
Sent: Monday, June 27, 2016 7:06 PM
Subject: Re: [time-nuts] OCXO noise as they retrace
Hi
For most OCXO’s most certainly not. The typical OCXO improves on ADEV as it
runs. That said, a good OCXO should have a 1 second ADEV
of at least parts in 10^-12 rather than 10^-11. A 5370 should have a floor at 1
second of around 2x10^-11. You may be measuring your counter
doing something stupid ( = needs alignment) rather than the OCXO or Cs.
Bob
> On Jun 27, 2016, at 5:55 PM, Bob Stewart <[email protected]> wrote:
>
> I've had a specific GPSDO running for some time now, and I notice that the
> noise at tau 1s has gotten worse as the retrace flattens out. In this case,
> the ADEV was about 3.6E-11 a month or so ago, and has now gone up to about
> 8.5E-11. (Measurements performed by a 5370A against a PRS-45A Cs standard.)
> Is this normal as the startup drift settles out? It's been on the same power
> supply module during this time, but I have been using it to test new code, so
> the DAC has been cycled from midpoint to lock numerous times. Another unit
> that's been running for some time has done essentially the same thing.
> Weather? Environment? GPS demons?
>
> Bob - AE6RV
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