[time-nuts] H-Maser, but not on ebait...

[Tom Van Baak]

> This may be a dumb question but I'm going to ask anyway.  With so many factors
> affecting the hydrogen's masing (is that the correct term) frequency - temperature,
> pressure, magnetic field, etc), how can a maser be a primary standard?  I understand
> that it can be an incredibly stable transfer standard but how can it be considered a
> constant?

Good question -- and that's exactly why masers are not
primary standards.

Instead, they have superb short- and mid-term stability so
are useful as frequency (not time) standards for things like
VLBI, or as "fly-wheels" for ensembles of cesium standards.

In timing laboratories maser(s) and cesium(s) are often
configured in essentially the same way as quartz and GPS
are in a GPSDO: one provides stable short-term frequency
and the other accurate long-term steering.

/tvb