[time-nuts] OCXO with ADEV of 1E-13 on Pluto Mission

[Attila Kinali]

On Thu, 16 Jul 2015 15:24:08 -0400
"Brian, WA1ZMS" <wa1zms at att.net> wrote:

> The crystal in the ref osv. came from Bliley. The part number is BG-61.  I 
> have no idea what the current cost is, but like most very good oscillators 
> the crystals were hand sorted and graded.

I had a short chat with Gregory Weaver (the guy behind the USO) two years ago.
Basically, they start with a lot of crystal slabs, select the best ones
after each processing step. In the end, they have maybe a dozen (or less)
crystals that are then fit into oscillators, which again are tuned by hand
and selected. The best oscillators are then send onto the mission.

A fun fact here is, that the oscillators are not tuned for maximum
Q of the resonator. Instead they are slightly damped and some Q is
traded for lower noise of the sustaining amplifier.

Another fun fact is, that the glass housing acts like a getter
when put in vacuum. Thus the stability increases increases over
time, when the whole system is in space.


			Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson