[time-nuts] GPS 1 PPS accuracy limits

SAIDJACK at aol.com SAIDJACK at aol.com
Tue Apr 20 21:59:59 UTC 2010

Hi Magnus, Life speed,
what does accuracy mean? Average (rms, 1-Sigma) frequency accuracy? If yes, 
 over what time frame is the average?
Or is this the peak to peak allowable deviation? Over what temperature  
range, and after how long of a warmup?
To give you an example, a typical Fury desktop unit with DOCXO is  capable 
of better than 2us holdover drift per day after 3 to 5 days of constant  
That equates to an average frequency accuracy over one day without GPS of  
<2.3 x 10^-11.
With GPS the accuracy on average is better than 2E-012 after about an  hour 
or so averaging.
In a message dated 4/20/2010 13:07:53 Pacific Daylight Time,  
magnus at rubidium.dyndns.org writes:

life  speed wrote:
> Time Nuts;
> I have a customer request for  a microwave frequency synthesizer with 
extreme accuracy requirements;
>  4 X 10^-11, or 0.04 PPB.  Obviously this is way out of quartz oscillator 
> Is GPS 1 pulse-per-second useable, or do they need an  atomic clock?
> Maybe they don't realize what they are  spec'ing.

I really think you should ask them to motivate themselves on  that spec, 
the intended use etc. They can certainly get a spec like that,  but is it 
what they need?

You certainly want something like a GPS  clock to feed that thing if they 
really need that level of accuracy. Or do  they only need that level of  


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