[time-nuts] Advise on building a DIY GPSDO?

[Hal Murray]

albertson.chris at gmail.com said:
>  I may never get around tooth's as the Rb is very good all by itself to the
> limit of my ability to measure it.

Wait longer.  :)

If your Rb doesn't have a PPS, make one.  One of tvb's divider chips is 
probably the simplest approach.  You can probably do it with an Arduino if 
you have one handy and like writing that sort of code.

Compare the PPS from the Rb with the one from your GPS.  It's probably 
simplest if your Rb PPS is offset a bit from the GPS PPS.  The idea is to 
make the difference always have the same sign.

Feed both PPS pulses to some equipment that can measure the time difference.  
Collect data.

If you have a typical low cost (non GPSDO) GPS device, you should be able to 
make graphs like the ones that show a hanging bridge.  Look at a sawtooth 
region, not a bridge.  Pick the top or the bottom or the middle or whatever 
you can remember.  Call that the offset.  Wait an hour collect more data.  
Has your offset shifted?  If not wait longer...

You are measuring the average frequency of the Rb.  It might be temperature 
sensitive.  Can you see the offset change over a day?  (That assumes you turn 
the heat down at night...)  Or maybe you are seeing the GPS night/day shift.


-- 
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