[time-nuts] Z3805A cooling requirements?
ailer2 at t-online.de
Fri Dec 21 13:42:58 UTC 2012
(oh, I've got to split the posting)
> The picture enclosed can give you a first impression. What we see is
> the difference time between the GPS signal and the OCXO (blue)
> ("PPS-TI"), which is an HP 10811. In red we can see the EFC. The total
> span is 24 h.
> Before I applied the fan, the noise was at a maximum of about +/- 20 ns.
> Some hours after starting the fan the noise is much greater. That should
> have a significant impact on the ADEV.
> I don't put the ADEV curves here, I make up for it when the EFC
> compensation is completely out of the scope, that will be in about 12
> hours. I don't have the ADEV at 1 s, but the ADEV at 10 s has been
> almost constant. The ADEV at about 1000 s has a nasty bump now.
> IMHO that fits to the physical facts: the airflow will surely not affect
> the 10 s ADEV since the OCXO tries its best to isolate the oscillator
> from short time temperature influences. However, the turbulent air flow
> that I applied will influence the longer time ADEV.
> Have a nice solstice
> Am 21.12.2012 12:44, schrieb Volker Esper:
>> Yes, I made such a setup, it's now running 22 hours. I'll post the
>> results in two hours or so (if nothing evil happens to the earth,
>> Am 21.12.2012 03:35, schrieb SAIDJACK at aol.com:
>>> Wish I had more time to play with this setup.
>>> How about fellow time nuts spend some time and present similar test
>>> data on
>>> their OCXO's to compare?
>>> I was interested in the 1s to 100s ADEV, and my runs were from 8
>>> minutes to
>>> 20 minutes, certainly enough time to capture data for 1s to 100s ADEV
>>> In a message dated 12/20/2012 14:17:59 Pacific Standard Time,
>>> magnus at rubidium.dyndns.org writes:
>>> On 12/20/2012 01:34 PM, Bob Camp wrote:
>>>> Temperature transients are not a good thing for an OCXO. If you
>>> deliberately use the fan to create a transient, then yes the OCXO will
>>> not be
>>> happy. The question it - what happens after the transient has settled
>>> out? The
>>> plot you have still looks a lot like a step function.
>>> I agree. Temperature steps stresses the OCXO oven loop and easily
>>> creates a gradient over the crystal. As the oven loop tracks in, the
>>> frequency returns to around normal. The trouble with forced air over a
>>> crystal is that the metal shield couples very well and acts like a heat
>>> sink. A think plastic cover over it and forced convection doesn't have
>>> the same effect. There is even being used by at least one vendor. Works
>>> very well for the extra cents of manufacturing cost.
>>> The HP10811 is recommended to be put in a airflow-quiet corner of the
>>> world. Look at it's mounting in the HP5370A/B for instance.
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