[time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit

Magnus Danielson cfmd at bredband.net
Tue Dec 19 23:06:55 UTC 2006


From: Dr Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
Date: Wed, 20 Dec 2006 11:24:42 +1300
Message-ID: <458866AA.3000209 at xtra.co.nz>

> Magnus Danielson wrote:
> > From: Brooke Clarke <brooke at pacific.net>
> > Subject: Re: [time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit
> > Date: Tue, 19 Dec 2006 13:42:28 -0800
> > Message-ID: <45885CC4.30007 at pacific.net>
> >
> >   
> >> Hi Brendan:
> >>
> >> It's interesting that the PRS10 can time stamp the 1 PPS input with a 
> >> resolution of 10 ns.  I wonder how they do that.
> >> http://www.thinksrs.com/downloads/PDFs/Catalog/PRS10c.pdf
> >>     
> >
> > It actually says it does it with 1 ns resolution. A x100 analog interpolator
> > circuit for 1 ns to 100 ns (10 MHz) isn't rocket science. See the HP 5335A
> > operations and service manual. Getting 10 ns accuracy isn't supprising.
> >
> >   
> >> When I picked up my PRS10 at the factory during the tour I learned that 
> >> the 10 MHz oscillator in the PRS10 was an improved version of the SC10.  
> >> There's an Allan plot for the PRS10 at:
> >> http://www.thinksrs.com/products/PRS10.htm <- overall PRS10 page
> >> http://www.thinksrs.com/assets/instr/PRS10/PRS10diag2.htm  <- Just the plot
> >>     
> >
> > Do the PRS10 comes with the 5 dollar tour ticket or is it the other way around?
> > :D
> >
> > The PRS10 seems like a good device.
> >
> > Cheers,
> > Magnus
> >
> > _______________________________________________
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> >
> >   
> The PRS10 is somewhat marginal for VLBI although it has been used for 
> short integration times to observe the L band hydroxyl line at around 
> 1600 MHz.
> Fortunately all stations but one used hydrogen maser clocks/frequency 
> standards. Some of the better crystal oscillators (Oscilloquartz 8607 
> BVA, FTS1200 etc) have better performance for integration times up to 
> 100s or so. The PRS10 OCXO DAC has a fractional frequency resolution of 
> around 1E-12. This limits its performance for VLBI with long integration 
> times where it is necessary to have phase synchronisation between all 
> stations to within 10 degrees or so over the integration time.

If you consider telecom and many instrument applications the PRS10 has
sufficient performance. I've actually sat at meetings and had the PRS10
behaviours as a reference frame.

VLBI has quite a different requirement on performance. Actually, I'd like to
hear what frequencies and performances you actually use and have.

Cheers,
Magnus




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