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

[Pete]

I'm sure Brooks Shera can describe the nuances of his GPS locking circuit 
far better than I can; but that said, the 24MHz oscillator is not used to 
directly count the 1PPS signals. It is used over a 30 second measurement 
interval, yielding a precision of about 1.4nS per count. Also the digital 
filter designed into the PIC software yields very long time constants once 
you've moved away from the set-up mode; 2000 to 8000 second range comes to 
mind. Brooks' QST article shows 1E-11 performance & that was measured when 
SA was still turned on! This maybe mediocre by comparison to current 
commercial offerings, but it's not too shabby for something that is easily 
homebuilt.

Regards,
Pete Rawson