[time-nuts] Noise types and Allan Deviation

[Tom Van Baak]

> The tau range for which ADEV etc are sensibly independent of measurement
> system bandwidth should differ significantly when comparing a pair of
> hydrogen masers or a pair of low noise OCXOs (OSA8607, FTS1200 etc).

I'm not sure what "significantly" is, but as you suggested,
I do see more of a difference at low tau with two ultra low
noise references than with two normal OCXO. The effect
is zero to a couple of dB. See plots below.

> The lower limit for an 8607 or a good FTS1200 is probably in the 1 to
> 10s range.
> That is around the value of tau for which ADEV vs tau first approximates
> a horizontal straight line or reaches a minimum.
> 
> Bruce

Right you are. It's 2 seconds for the pair of 8607's and near 10
seconds for a 8607 vs. active H-maser. Compare these:
http://www.leapsecond.com/pages/adev-bw/tbolt-tbolt-bw.gif
http://www.leapsecond.com/pages/adev-bw/8607-8607-bw.gif
http://www.leapsecond.com/pages/adev-bw/8607-hm75-bw.gif

I'll add a maser-maser plot if I have it.

/tvb