[time-nuts] Mechanical 1PPS Oscillator Disciplining

[Bob Camp]

Hi

The speed of sound in quartz varies by axis, but only by about 2:1. The same basic physics that gets you a fundamental 5 MHz crystal that is at thickness Z gives you some dimension on a 5 KHz crystal that’s close to 1000 * Z.  Very low frequency crystals pretty much have to be designed so they resonate on a “long” axis of the blank. If they don’t then the blank / enclosure / price  gets crazy big. 

If you want to calculate just how long this or that resonance might be:

http://www.mt-berlin.com/frames_ao/descriptions/sio2.htm

Has all the numbers you would need.

Bob

> On Jan 10, 2015, at 2:06 AM, David J Taylor <david-taylor at blueyonder.co.uk> wrote:
> 
> Hi Tom dividing down wasn't always necessary I have sample from the UK  GPO
> Crystal Factory of NT-cut bars, quartz tuning fork, and Gapped Ring
> crystals, the latter marked 400cps (pre Hertz :-))  )  I think these are
> post WWII because they are mounted in IO base GT style tube envelopes.
> Dividers were achieved with neons and locked multivibrators, where
> necessary, I believe.
> []
> Alan
> G3NYK
> ================================
> 
> I have one "500 c/s" GEC crystal in an octal base which is thinner than a "60 Kc/s" one, so a different mode.  Never had it working, though.
> 
> 73,
> David GM8ARV
> -- 
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-taylor at blueyonder.co.uk 
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