[time-nuts] nubie querie

[Bob Camp]

Hi

Then there's the phase noise of the pulsar "oscillator"  ....

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For a simple crystal oscillator the two word answer might be "Leeson's model".  That of course is a cop out since it clearly defines multiple things that contribute to phase noise. 

Bob


On Mar 5, 2010, at 9:39 AM, Richard (Rick) Karlquist wrote:

> Don Collie jnr wrote:
>> I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind.
> 
> I vaguely remember reading that pulsars have some fantastic
> stability like 1E-20.  I don't remember how they established
> this.
> 
>> 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please]
> 
> Thermal (Johnson) noise in the resonator and thermal and shot noise in the active device.
> 
>> If this is known, then it becomes easier to design low phase noise oscillators.
> 
> Perhaps, but just knowing the mechanism doesn't tell you that the
> phase noise is inversely proportional to loaded Q, which you would
> also need to know to optimize phase noise.
> 
> 
>> I hope you enjoy these questions,.................................Don.
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