[time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ?

Bob Q quenbob5 at pacbell.net
Mon Dec 22 00:13:26 UTC 2008


Patrick,
I don't know of an analog approach using the 1 pps divided to 0.5 Hz (for 
50% duty cycle) as input to a phase detector.  1 Hz ripple frequency from 
the phase detector is probably not practical to filter.  You would need a 
low pass filter time constant of at least 1000 seconds and I think 
capacitors that will work for the long time constant will have poor 
temperature properties, leading to excess drift.  Digital approaches using 
the 1 pps signal compared to a divided OCXO signal are used by most modern 
designs.
Bob Q.
----- Original Message ----- 
From: "Patrick Reynaert" <preynaert at yahoo.com>
To: "time-nuts" <time-nuts at febo.com>
Sent: Sunday, December 21, 2008 2:13 PM
Subject: [time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ?


> Hello,
>
>
> Using the 10kHz output to lock an OCXO is common practice and seems to 
> give good results.
>
> Has anyone tried to use the 1pps output? One? could first make a simple 
> divider to create a 0.5Hz reference with 50% duty cycle, and then use this 
> signal to lock an OCXO. This would also allow the use of other OEM GPS 
> modules that don't have the 10kHz but only the 1pps signal.
>
> Of course, as the 0.5Hz signal is much lower in frequency than 10kHz, the 
> short-term stability is pushed more to the OCXO, making the requirements 
> of the OCXO even harder.
>
> But maybe the 1pps signal has better stability than the 10kHz signal? Or 
> is this the same since these signals will only influence the long-term 
> stability of the oscillator and have the same accuracy?
>
> Any thoughts are highly appreciated.
>
> Thanks,
> Patrick.
>
>
>
>
>
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