"Jim Lesurf" wrote

From the published results I've seen in JAES and the accompanying comments
it seems clear it may be able to do far more that that. The key point is
that the pattern of small but measurable changes in frequency isn't the
same every day.

I've just tried as an experiment displaying a broadcast TV waveform with the
'scope timebase locked to the mains frequency. This gives a much more
immediate indication of mains frequency stability than a frequency meter
does.

What was noticeable was just how fast mains frequency variations can occur.
Frequency variations of the order of 0.1% can occur in a matter of seconds,
an 0.5% variation within a minute or two. I'm sure that the pattern of this
sort of variation does not conform to a pattern, but is unique on each
occasion.

David.