[time-nuts] nubie querie

AL1 alain2.bouchet at wanadoo.fr
Sat Mar 6 16:18:16 UTC 2010


Hi Richard,

the frequency of pulsars has a slow deccay, so they can't be  good 
standards, in reality they are worse than our terrestrial atomic 
clocks...and we are not able to mesure better as 10E-17 s.
Cordiales 73
Alain F4GBC

----- Original Message ----- 
From: "Richard (Rick) Karlquist" <richard at karlquist.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Friday, March 05, 2010 3:39 PM
Subject: Re: [time-nuts] nubie querie


>
> 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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