[time-nuts] My GPSDO project: OCXO Thermal Oscillation?

[Bob Camp]

Hi

To answer your OCXO question:

The so called 34310-T is a double oven. It should be stable over some range (say 0 to 70 or -20 to 70) to about 0.1 to 0.5 ppb p-p. Trimble seems to like +12 on it so one would guess that +12 +/- 5% stable to +/- 0.5% should be fine. They seem to use it in open air / moving air. 

Assuming you are inside that sort of temperature and voltage range, then no, it should not oscillate thermally. Anything can be broken and if it is you should see the oven current going nuts. 

Bob

On Aug 16, 2013, at 11:09 AM, Bob Stewart <bob at evoria.net> wrote:

> I'm converting the code for the VE2ZAZ FLL to a PLL.  I'm seeing the phase correction change the EFC up and down about .02V to .03V over a period of 5 minutes or so (it varies).  The full range on the OCXO is about +/- 4Hz varied by 0 to +6V, so at least this is a tiny value.  I feel pretty confident with my code at this point.  I'm using a Trimble 34310-T OCXO for which I've been able to find almost no information.  Could this oscillating phase correction be some sort of thermal oscillation?  I've tried two separate 34310s and both act more or less the same.  My GPS device is normally a UT+, but I just now swapped in an "Adafruit Ultimate GPS Breakout" to the same effect.  Is this good, bad, or indifferent for a GPSDO?  I started this project not knowing what to expect, and I still don't.  Experienced help, speculation, or even just kind words at this point would be appreciated!  =)  I don't have a known good/stable reference to compare this
> to.
> 
> Bob - AE6RV
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