[time-nuts] oscillators

Jim Lux jimlux at earthlink.net
Thu Aug 30 08:57:49 EDT 2012


On 8/29/12 9:22 PM, Hal Murray wrote:
>
> richard at karlquist.com said:
>> No it doesn't use a cheap crystal.  It uses a *special* SC cut crystal. This
>> crystal could very easily cost more than an OCXO crystal.

http://www.q-tech.com/mcxo.html

>
> What's special about it?
Has to support the overtones properly. Not only does it have to be a 
good oscillator crystal, it also has to be a good thermometer

>
> I assume the cost-more aspect would be to allow an overall goodness factor competitive with an OCXO in the low power corner of the marketplace.  It might be cheaper overall to use a good crystal and a uP to correct for temperature than provide the power to run the oven.
>

Power consumption, size, etc.  Also, faster startup time (no waiting for 
an oven to stabilize)

> --------
>
> The other area where a uP is useful is in an environment with high vibration.  It can correct for acceleration as well as temperature.  There were several good URLs mention on this list in the past year or two.  The context was radar on helicopters.  Helicopters are full of vibrations/accelerations.  The numbers work out such that the frequency broadening due to vibration is interesting if your radar is looking for slowly moving things like people.
>
> ----------
>
> Crazy question dept:
>
> What do low cost rubidium oscillators do when vibrating?  Is it dominated by the cleanup crystal?
>
>
>





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