[time-nuts] time-nuts Digest, Vol 101, Issue 152

Said Jackson saidjack at aol.com
Fri Dec 21 17:53:51 UTC 2012


Mark,

Your plot still shows excursions of +/-1E-010, about 100x higher base noise than the Z3801A/Z3805A are capable of achieving. Wonder where that noise is coming from? This noise is probably much higher than the thermal effects.

The original post was the question "does my Z380xA have reduced stability if I add a fan" or similar, I think the answer is shown to be "yes".

Volker, I wonder if you also see fan-induced spurs in the phase noise from 1Hz to 100Hz. I would not be surprised if the fan vibration adds significant spurs to the 10811A crystal.

Bye,
Said

Sent from my iPad

On Dec 21, 2012, at 9:42 AM, Mark Spencer <mspencer12345 at yahoo.ca> wrote:

> This plot should show the frequency change more clearly.   (Same data just presented differently.)
> 
> It seems to me that the noise goes may be going down a bit for a minute or so just after the fan is turned on but I don't believe these plots provide conclusive evidence of this.
> 
> 
> Regards
> Mark Spencer 
>> Message: 7
>> Date: Fri, 21 Dec 2012 09:27:29 -0800
>> From: Said Jackson <saidjack at aol.com>
>> To: Discussion of precise time and frequency measurement
>>     <time-nuts at febo.com>
>> Cc: Discussion of precise time and frequency measurement
>>     <time-nuts at febo.com>
>> Subject: Re: [time-nuts] Z3805A cooling requirements?
>> Message-ID: <83CE0384-2996-4155-B51B-9D79910B29AA at aol.com>
>> Content-Type: text/plain;   
>> charset=us-ascii
>> 
>> Great plots guys!
>> 
>> Looking at these results I think my original claim still
>> holds: ADEV goes up when a fan is involved versus no fan,
>> even on a double oven 10811..
>> 
>> Clearly visible on the 10811, maybe not so much on the MV89
>> but that unit seems to have frequency moves into the xE-010
>> region on Marks plot so maybe the effect is just a bit
>> hidden?
>> 
>> Bye,
>> Said
>> 
>> Sent from my iPad
>> 
>> On Dec 21, 2012, at 5:44 AM, Volker Esper <ailer2 at t-online.de>
>> wrote:
>> 
>>> ...and the picture of the experiment...
>>> 
>>> 
>>>> 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
>>>> 
>>>> Volker
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 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,
>>>>> meanwhile).
>>>>> 
>>>>> Volker
>>>>> 
>>>>> 
>>>>> 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
>>>>>> measurements..
>>>>>> 
>>>>>> bye,
>>>>>> Said
>>>>>> 
>>>>>> 
>>>>>> 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:
>>>>>>> Hi
>>>>>>> 
>>>>>>> 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.
>>>>>> 
>>>>>> Cheers,
>>>>>> Magnus
>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>>> To unsubscribe, go to
>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>>> and follow the instructions there.
>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to
>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>> 
>>> <DSCF1758_bb.jpg>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> 
>> 
>> ------------------------------
>> 
>> _______________________________________________
>> time-nuts mailing list
>> time-nuts at febo.com
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> 
>> End of time-nuts Digest, Vol 101, Issue 152
>> *******************************************
> <MV89A Fan turned on at 460 seconds v2.png>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list