[time-nuts] Phase, One edge or two? (was Digital mixing with a D Flip Flop)

Bob Camp kb8tq at n1k.org
Wed Oct 22 20:38:47 EDT 2014


> On Oct 22, 2014, at 5:57 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> tvb at LeapSecond.com said:
>> 2) For long-term analysis, even 1 PPS is overkill. Having more data may not
>> improve your oscillator drift plot at all. This is because the frequency is
>> a moving target. Ever more precise measurements of a moving target are
>> wasted; they don't add any clarity to the overall trend. Consider measuring
>> a 10811 for a year. Do you need to follow its phase or frequency every 100
>> ns? Or second? Or minute? Maybe as little as one data point per day is more
>> than enough to make a perfectly accurate long-term frequency drift plot. 
> You need more than 1 sample per day for ADEV plots left of 100,000 K seconds.
> Suppose you have lots and lots of data at, say, 1 second samples.  You can 
> turn that into an ADEV plot.  Does anybody scan the data in clumps, say a 
> day, to see if the short-tau picture changes over time?

ADEV most certainly does change with time, even for short tau’s. 


> -- 
> These are my opinions.  I hate spam.
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