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

[Bob Camp]

Hi

It's not all smoke and mirrors. The Q of quartz goes up as frequency goes down. Nobody really debates that. As frequency goes down blank diameter would need to grow to keep everything same / same. Again not much debate.

What does get a lot of debate is  just how small you can get blank diameter and still get reasonable performance.

If people just liked 3" diameter crystal packages.....

Bob



On Jan 31, 2012, at 12:41 AM, "Tom Van Baak" <tvb at LeapSecond.com> wrote:

>> 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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