[time-nuts] Doppler and FMT

[Bob Camp]

Hi

As with most complex questions the real answer is "that depends" …

Blind averaging will indeed get you in trouble. Curve fitting (a straight line is a simple one) often is the better approach to phase data. You can get an "averaging like" improvement (square root of the number of samples). You need to use a technique that fits the data and the noise you have on the data. 

Bob

On Sep 19, 2013, at 8:17 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:

>> So it's just a matter of averaging what you can measure
>> and assuming that the average will be close?
> 
> Two quick comments.
> 
> 1) A gradual phase drift over time is identical (by definition) to a frequency offset.
> 
> 2) In general, "averaging" a moving target gets you *less* accuracy, not more.
> 
> We learned in school that averaging enhances accuracy. This is true in textbook cases where the mean is constant and where the distribution of error about the mean is symmetrical.
> 
> But when working with clocks (time, frequency, stability measurements) this assumption often not true and it's helpful to think of averaging more as a disease than a cure.
> 
> /tvb
> 
> 
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