[time-nuts] I've been thinking about a GPS receiver experiment

Bob kb8tq kb8tq at n1k.org
Wed Oct 25 15:26:10 EDT 2017


Hi

Everybody I have ever talked to about the internal disciplining on Rb’s comes 
up with “it’s not for a GPSDO” somewhere in the first minute of the conversation.
The objective seems to be to tune the unit to a perfect source to speed up the
calibration process. The idea never appears to include noise on the reference
signal or odd perturbations in the reference. 

Bob

> On Oct 24, 2017, at 6:42 PM, Mark Sims <holrum at hotmail.com> wrote:
> 
> I did a quick silly experiment where I took a PRS-10 disciplined by an X72 which was disciplined by the PRS-10.  The result seemed to have created a rupture in the space-time continuum.  Nobody was happy...  they didn't seem to agree on who was in charge.    I need to try it again now that I have my X72 interface boards back from China and can properly connect to the X72.
> 
> BTW, the firmware based disciplining on the X72 seems to be rather crappy.  It has lots of trouble locking to less than perfect 1PPS inputs.   For instance it goes into holdover mode over half the time when driven by a Ublox LEA-5T (which seems to have like +/- 60 ns jitter on the 1PPS.   It does lock fine with a Tbolt...  but needing a GPSDO to discipline a rubidium sort of defeats the purpose of disciplining a rubidium.
> 
> Lady Heather now has an X72/SA22 disciplining routine built in that works fairly well using the LEA-5T.  Adevs are in the mid E-13 range at 10,000 seconds and the 1PPS output is in the +/- 50 ns range.  
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