[time-nuts] EFC info on Trimble 34310-T OXCO
Bob Camp
kb8tq at n1k.org
Mon Aug 25 00:48:26 UTC 2014
Hi
Keep in mind that the OCXO is likely (if it’s a modern part) optimized for TC at it’s normal thermal gain. The gain and set point are adjusted for a flat curve. If you bump either the gain or the set point you rotate the curve.
Bob
On Aug 24, 2014, at 8:36 PM, EWKehren at aol.com wrote:
> Charles
> I use double bobble pack inside the Alu channel and I always start out by
> monitoring the OCXO and make sure it is at least 10 C below the spec range.
> The tbolt is center located and I use a combination of rubber mounts but
> suspended that they sell for hard drives and squares of double bubble pack.
> Vibration and thermal.
> Bert Kehren
>
>
> In a message dated 8/24/2014 8:26:02 P.M. Eastern Daylight Time,
> csteinmetz at yandex.com writes:
>
> Bert wrote:
>
>> As I said before am waiting for the small spheres and will see what
> happens.
>
> Monitor carefully, as I suspect the spheres will pack too tightly
> leaving too little airspace. You could easily burn down an OCXO if
> this proves to be the case and the oven control loop goes
> unstable. I'd put a thermal sensor on the OCXO itself for testing.
>
> Even if it doesn't burn down, you could find that the oven
> performance is degraded by (i) instability or quasi-instability of
> the oven controller, or (ii) too much thermal resistance (remember,
> you want to add as little thermal resistance as possible).
>
> On the other hand, mounting the OCXO as centrally as possible inside
> the outer enclosure on thermally non-conducting standoffs (teflon or
> nylon), with at least an inch of air on all six sides, has proven to
> work extremely well.
>
> When I described using packing peanuts (or similar) to break up the
> airflow, it was in the context of having already mounted the OCXO as
> centrally as possible inside the outer enclosure on thermally
> non-conducting standoffs with at least an inch of air on all six
> sides. And as I said, I have not found the additional step necessary
> once you have done this. It may even be counterproductive.
>
> Best regards,
>
> Charles
>
>
>
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