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[time-freq] Re: Atomic Oscillators & Rubidium Phase Noise

Kelley, Paul F LTC RET paul.kelley at us.army.mil
Sun Feb 10 03:57:41 UTC 2008

I am not going to propose any hard solutions to your quandary. BUT If you use two or more Z3801A and phase compare with very long period averaging and characterize the corrections to an Rb Standard. You should get very high standard and very low phase noise. The added benefit of not needing to send it anywhere to be calibrated. You can if you wish get the world time comparison data from the BIPM archives, run a comparison to your log data to refine your corrections. This may help.

----- Original Message -----
From: K&J Aggett 
Date: Sunday, February 10, 2008 6:45
Subject: [time-freq] Re: Atomic Oscillators & Rubidium Phase Noise
To: time-freq at lists.tapr.org

> Hi,
> Surely what is being talked about here is essentially the quality 
> of the 
> design (and how much money you are prepared to spend)? Eric wrote:
> ..... I have some experience using Z3801 GPS-disciplined 
> oscillators, 
> and I can state that they are quite stable and accurate. However, 
> they 
> use an oven-stabilized crystal oscillator ........
> And Ron wrote:
> ... Yep, but what about phase noise ..... ?? .... I think your 
> would not even come close .....
> Don't all atomic standards incorporate oven stabilized crystal 
> oscillators and isn't phase noise largely dependent upon that 
> crystal 
> oscillator? My understanding is that the frequency control system 
> can/does contribute to /total/ noise on the output. I also 
> appreciate 
> that at 1PPS it is a long time between drinks for a GPS control 
> system, 
> and that if GPSDO's were better than rubidiums then there would be 
> no 
> new rubidiums on the market, but what are the numbers for phase 
> noise 
> and accuracy for /good/ GPSDO's? Are they being made to be a 
> cheap 
> reference rather than as a realistic rubidium replacement?
> Now I am supposing that Brooks Shera is not the technical 
> equivalent of 
> a HP design team nor has he the resources such a team would have 
> had, 
> but if the crystal oscillator in a cesium or rubidium standard was 
> controlled in situ by his controller, does anyone know what 
> degradation, 
> if any, in phase noise output would be achieved?
> Regards,
> Keith.
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