[time-nuts] OCXO noise as they retrace

Bob Camp kb8tq at n1k.org
Mon Jun 27 20:06:45 EDT 2016


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.


> On Jun 27, 2016, at 5:55 PM, Bob Stewart <bob at evoria.net> 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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