[time-nuts] Is my Cs C-Field set OK or do I need to take more data?

[Brooke Clarke]

Hi Poul:

I don't understand that.  The manual says the 256 reading filter is 
automatically set when LM is set to 1, i.e. when locking to an external 
1 PPS input.
My Motorola 8 channel GPS receiver does not have a clean 1 PPS.  Are you 
referring to the phase lock time constant (PT command, now set to 8)?

Thanks,

Brooke

Poul-Henning Kamp wrote:

>In message <41E22178.4020103 at pacific.net>, Brooke Clarke writes:
>  
>
>>Hi Poul:
>>
>>Ha    ha    ha   you give me a chuckle.  Probably because that's the 
>>problem, when to stop and change something.
>>I'm thinking I might be able to keep this test going and at the same 
>>time get a GPS direct 1 PPS for comparison.  I think the PRS10 is adding 
>>a variable that actually makes the test harder than it needs to be.  I 
>>was hoping that the PRS10 would act as a flywheel to smooth out the GPS, 
>>but I think it's more like a roller coaster.  After posting the plot and 
>>watching a movie the data went back down to the 32 ns area and so the 
>>data has taken on a completely new flavor.
>>    
>>
>
>Running the PRS10 off a GPS is not as trivial as it could sound.  If your
>GPS has significant jitter (they all do) you need to run with the 256
>sample averaging filter ON in the PRS10.  If you do that, the entire PLL
>changes dynamics significantly and at least I have found that a relatively
>short timeconstant is necessary (I'm using a UT+ and PT=8)
>
>Poul-Henning
>
>  
>

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