[time-nuts] Racal-Dana 1991 w. Option 4C - what is that ?

Tom Van Baak tvb at LeapSecond.com
Tue Jan 31 00:41:27 EST 2012


> What makes 5 MHz more stable than 10 MHz?
> 
> Why not 2.5 MHz and double twice?  Or 1.25 MHz and three doublers?

Apparently 2.5 MHz is the most stable of all for reasons not
fully understood, but accepted. That's why the early Sulzer
oscillators were 2.5 Mc. They doubled them to get 5 MHz.

I don't have a reference handy but there are charts and
curves in old papers on quartz technology that show a peak
in performance (Q?) around 2.5 MHz. Doubling, tripling, or
quadupling works too but you get noise at every stage so
this is not always a solution.

The 2.5 MHz blanks are very large and expensive; I heard
that's why the industry moved to 5 and then 10 MHz crystals.
Perhaps one of the xtal experts on the list can clarify this for us.

See also:

Brief History of the Development of Ultra-Precise Oscillators
http://www.ieee-uffc.org/main/history.asp?file=norton

Fifty Years of Progress in Quartz Crystal Frequency Standards
http://www.ieee-uffc.org/main/history.asp?file=frerking

/tvb






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