[time-nuts] Phase noise confusion II

[Bob kb8tq]

Hi

It is not at all uncommon to …. errr …. make that decision, regardless
of what the customer might think about it :)

Even with that sort of decision, the whole process of measuring a one
sigma and multiplying by 6 depends very much on the underlying 
processes (noise or maybe something else ….) being well behaved /
Gaussian sort of things. One can at least on paper construct situations
that do not meat that “well behaved” constraint …..

Lots and lots of issues. 

If you turn back the clock, this whole thing is very similar to the 1960’s
frequency stability measurement fun and games. That’s what ultimately
gave us ADEV. 

Bob

> On Apr 10, 2020, at 8:05 AM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> 
> I once got into that "p-p" business and it was like pulling teeth to get
> the customer
> even semi-reasonable.  He finally agreed to stipulate that the p-p value
> could be
> construed as 6 X the rms value.
> 
> Dana
> 
> 
> On Fri, Apr 10, 2020 at 6:57 AM Bob kb8tq <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> Which of the multitude of definitions are we talking about?
>> 
>> One very common definition looks at peak to peak jitter and does
>> not care about the center. Another looks at +/- peak to edge and
>> then uses the greater of the two numbers. Other definitions look
>> at RMS jitter and generally don’t care about the edge.
>> 
>> At least to me, the biggest problem is that any time “peak” or “peak
>> to peak” comes in to a calculation that involves random noise,
>> things go sideways fast. People pretty much never want to
>> define a confidence level (how any sigma?). They want an
>> absolute number.
>> 
>> Lots of fun
>> 
>> Bob
>> 
>>> On Apr 10, 2020, at 6:05 AM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
>>> 
>>> Question about definition of jitter:   Is it the variation in
>>> pulse-to-pulse spacing, or is it
>>> the variation in pulse positions with respect to a jitter-free waveform?
>>> 
>>> Dana
>>> 
>>> 
>>> On Thu, Apr 9, 2020 at 11:21 PM Hal Murray <hmurray at megapathdsl.net>
>> wrote:
>>> 
>>>> 
>>>> richard at karlquist.com said:
>>>>> There is always an implied clock recovery loop that the the jitter is
>>>>> measured against. The loop may itself affect the jitter measurement
>>>> either by
>>>>> cleaning up jitter or contributing to it.
>>>> 
>>>> Interesting.  I hadn't thought about it that way.
>>>> 
>>>> Suppose I measure the edge to edge times and make a histogram.  Can I
>> get
>>>> jitter out of that?  Where is the clock recovery loop?
>>>> 
>>>> --
>>>> These are my opinions.  I hate spam.
>>>> 
>>>> 
>>>> 
>>>> 
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