[time-nuts] Cs stability

Magnus Danielson magnus at rubidium.dyndns.org
Tue Jul 17 01:25:40 EDT 2007

From: SAIDJACK at aol.com
Subject: Re: [time-nuts] Cs stability
Date: Tue, 17 Jul 2007 01:13:58 EDT
Message-ID: <c6f.13bfd55f.33cdaa16 at aol.com>

> Hi guys,

Hi Said,

> I did tilt my 4050 when I first installed the unit, that number is from my  
> memory. Notice that Magnus is right of course, the Cs will compensate the tilt, 
>  given enough time to do so. I did not mean that the 1E-09 error will stay  
> permanent of course, as I said in the follow-on sentence.

Ah. The it was certainly a crystal detuning which took some time to overcome by
a sluggish control-loop.

On the other hand, few Cesium beams should be required to handle quick 90
degrees tilts during operation. They should sit firmly in the rack.

Touring cesiums is a different buissness, but they should rarely have to handle
quick tilts during operation too.

> Also the 4050 is not very well temperature compensated compared to modern  
> units, I was not impressed when I saw the FTS tempco specifications. A good  
> GPSDO can outperform the 4050.

Several developments have occured since the 4050.

> I have a military OCXO sample (new product) that is supposed to be  
> "g-insensitive" and even that one has about E-09 frequency shift per 90 degrees  tilt.

... and you have not put a GPS diciplining on it yeat??? 

> One of the only ways to get around that is to use three crystals in  series, 
> with the three crystals oriented in the the XYZ axis, so their  errors 
> compensate out.

As I recall it, both gravity force and magnetic fields will contribute to
crystal detuning.

> Vibration is also a big enemy of crystal oscillators of course.

As always.


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