[time-nuts] KD2BD WWVB receiver/decoder in QEX

Charles Steinmetz csteinmetz at yandex.com
Sun Nov 22 19:24:25 EST 2015

Hal wrote:

>It would be interesting to measure the propagation delay over a day 
>or week, and watch the PLL error voltage over a scale of seconds or minutes.

Somewhere I probably still have miles and miles of paper tape that 
came out of a WWVB phase comparator for many years BGE (before the 
GNSS era).  In addition to the slow tracks, which were recorded 24/7, 
there were also fast tracks taken periodically.  At the time, it was 
the only practical way to maintain NIST traceability of time and 
frequency measurements.

The take-home points from this data (at least for those of us who are 
a half-continent or more distant from Ft. Collins) are (i) that the 
propagation delay varies quite a lot -- 10s of ppm normally, more 
during periods of unsettled space weather; (ii) that phenomena too 
numerous to count contribute to the variability, so the resultant 
error is a complex epicyclic function of phenomena with periods from 
hours to years overlaid with random noise that can be much greater 
than the cyclic variations; and (iii) that the amplitudes of many of 
the lesser cyclic errors do not fall off rapidly compared to the 
amplitudes of the stronger ones, so simple approximations of the 
epicyclic features do not allow predicting the propagation delay more 
closely than about tenths of a ppm (parts in e-7).

Been there, done that -- for many years -- and I'm very glad we're 
rid of the need for it.  Sometimes, progress is ... well ... progress.

Best regards,


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