[time-nuts] Reference oscillator requirements when measuring ADEV ?

Bob Camp lists at rtty.us
Fri Jul 15 01:05:06 UTC 2011


Hi

You can be quite sure it's no worse than 2x10^-12. It is pretty common to scale by square root of two based on a "they could be equal" assumption. 

Bob



On Jul 14, 2011, at 8:32 PM, Mark Spencer <mspencer12345 at yahoo.ca> wrote:

> 
> 
> I'm curious in knowing if there are any rules of thumb as to how much better a 
> reference oscillator needs to be than the device under test when measuring ADEV 
> ?
>  
> To provide a bit of context to my question I'm using a HP 5370B to repeatedly 
> measure the time interval between the 10 Mhz signals from a FTS 1050 and 
> rubidium oscillator.   
> 
>  
> Having compared the FTS 1050 to another OCXO in the past I'm confident that it 
> is meeting or exceeding it's spec of an ADEV of 1X10-12 or better at tau's of 
> say 100 thru 1000 seconds.   I'm also confident that at tau's of 100 seconds or 
> more the noise introduced by the 5370B is less than 1x10-12.   
>  
> The underlying question that I have is how much confidence could I put in 
> measurements that show the rubidium of having an ADEV of say less than 2.0X10-12 
> at a tau of 100 sec ?   
> 
> 
> This is just for a hobby (: and I'm not looking for any degree of certainty but 
> I'm curious in understanding how accurate the measurements might be and if 
> changes in the measurements might not be caused by changes in the device under 
> test.  
>  
> Thanks in advance for any replies.
>  
> Regards
> Mark Spencer
> 
> 
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