[time-nuts] WWVB Disciplined Oscillator

[Peter Monta]

>
> Does NIST publish the transmitter bandwidth?  I've never seen it, but I
> haven't done a serious search.
>
> Maybe somebody near enough to get a clean signal could measure it.  What
> does a spectrogram look like?
>

Some of the KiwiSDR receivers are close enough to get an excellent signal.
Coincidentally I gave this very experiment a try some weeks back; give me a
few days to find the recordings and analysis scripts.  But the bottom line
is that 100 microseconds seems possible.  The antenna bandwidth is some
hundreds of Hz, if I remember right, but the high resolution would come
from tracking a specific point on the amplitude trailing edge (say, the 90%
point).

Another interesting aspect of the WWVB recordings is that the constellation
diagram shows some brief, large phase excursions during amplitude changes.
Phase accuracy is pretty good steady-state, but near the edges it goes kind
of wild.  Transmitter nonlinearity no doubt.  It could be predistorted out
(even adaptively if desired), but it's probably not worth the trouble.

Cheers,
Peter