[time-nuts] Question on crystal jumps

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Oct 23 23:01:31 UTC 2008

Steve Rooke wrote:
> Hi,
> I believe it was pointed out earlier that the output of a LPRO uses
> some form of xtal oscillator as the output of the rubidium stage is
> quite noisy. Considering the general consensus is that xtal
> oscillators have these jumps, I wonder if the output of the rubidium
> stage could be just passed directly through a multi-stage xtal lattice
> filter to clean it up and use that directly and that may circumvent
> the xtal jumps people are seeing.
> 73 - steve

The rubidium standard is passive it doesnt oscillate, it merely acts as
a high Q filter whose resonance can be probed with an external source.
Thus you need to replace the crystal oscillator with another low noise
source to interrogate the rubidium resonance.

To be useful the bandpass filter would need a bandwidth of a few
milliHertz or less.
The crystals in the lattice filter will also experience similar jumps.


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