On 8/29/12 9:22 PM, Hal Murray wrote:
rich...@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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