Hi Lars.   I own a G3RUH (Miller) GPSDO.

>From what I can recall....  While testing mine with  my collection of 
>HP5370B's and my assortment of references the performance of mine while locked 
>was generally comparable to the one in the link you provided.   I never tested 
>it "un locked."  

I couldn't measure phase noise and the performance of my test setup at taus of 
less than 100 seconds or so was probably a limitation as well.   My references 
(BVA OCXO, PRS10 rb and a cherry picked Z3805 GPSDO) probably weren't really 
good enough either.

It is a nice unit that I have currently loaned out to a local amateur radio 
operator.   Acquiring it lead to me spending a sizeable amount of time and 
money on time nuts pursuits over the years.

Sent from my iPhone

> On Sep 16, 2016, at 1:13 PM, Lars Walenius <lars.walen...@hotmail.com> wrote:
> 
> Hi Nick,
> 
> Jim Millers design is very clever and as I see can give results as good as a 
> digital approach but it has the same limitations:
> The GPS jitter and the oscillator jitter in combination with the loop 
> bandwidth.
> 
> The only ADEV I have seen for the Miller GPSDO is this one  
> http://www.leapsecond.com/pages/gpsdo/  .
> Can anyone point me to other tests?
> 
> The ADEV I see on leapsecond.com indicates for me a time constant of around 
> 200seconds. That is what you get with a OCXO range of 0.25ppm. You don´t need 
> to have a large RC-filter. The original R1-C1 time constant with 16 seconds 
> time constant will work as long as the internal oscillator in the Jupiter-T 
> is at least some Hz away from a multiple of 10kHz. If that is true the 
> sawtooth out of the Jupiter will have enough high frequency to be easily 
> filtered by the RC. This is of course a risk. See for example: 
> https://www.febo.com/pipermail/time-nuts/2005-August/019106.html . If you get 
> a hanging bridge you have at least as much trouble as a non sawtooth 
> corrected GPSDO and probably much worse as the RC filter is only 16s. In the 
> digital approach the prefilter may filter away the hanging bridge (in best 
> case).
> 
> As I understand the Miller GPSDO with a OCXO with a 0.25ppm range and 10kHz 
> into an XOR phase detector and 16s RC will be very similar to a digital 
> approach with a TIC (Time interval counter ) with +-25us range followed by a 
> prefilter with time constant 16s and a loop with just the P-term with a time 
> constant of 200secs. As it has no I-term it will have slightly less noise but 
> the output phase will drift as soon as the OCXO drifts (as a FLL). The 
> resolution of the XOR phase detector (TIC) will be limited by the noise but 
> as 0.1mV is 1ns the resolution can be seen as better than 1ns is my 
> conclusion. A problem might be that the output of the XOR drifts with the 5V 
> supply but this can be seen as the same problem as the DAC drift in a digital 
> approach.
> 
> My conclusion (without testing) is that the Jupiter-T 10kHz is very good but 
> not better than the sawtooth corrected outputs from M12 or LEA6T receivers. 
> That is the ADEV can be approximated by 1E-9/Tau (1E-12 at 1000s) in good 
> conditions.
> 
> My experience with the Venus838-T is only 2 weeks but disappointing. This can 
> also be guessed from the datasheet ADEV curve, that I guess is sawtooth 
> corrected values as it starts at 3E-9 at 1s, but is only 1E-11 at 1000s a 
> factor 10 worse than I get with the LEA-6T with the same antenna and setup. 
> If anyone have ADEV-MDEV curves to share I would be glad to see what can be 
> achieved with the venus838-T. My conclusion is also that sawtooth correction 
> is useless on my 838-T.
> 
> Lars
> 
> 
>> Nick wrote:
> 
>> Jim Miller's 10 kHz GPSDO that’s been referenced here has either solved this 
>> problem, or the 10 kHz output of the >Jupiter is substantially better than 
>> the Venus’ 10 MHz output, or the design doesn’t give the results time-nuts 
>> expect >from a GPSDO. Which of those applies?
> 
> 
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