[time-nuts] HP 5730 data polling technique?

[Bob Camp]

Hi

The basic input to ADEV is phase. That’s nice, but it’s not how a lot of people think about “frequency” sources. We 
get taught that phase modulation and frequency modulation are two different things. After they finish with that there is 
a little footnote somewhere that says “but the really are the same thing”. The gotcha is that most people burn out before
they get to the footnote. 

The frequency plot will show you what you “expect” to see when looking at a frequency source. Big frequency jumps are
bad, straight level lines are good. Because it’s what you are expecting, it’s probably the best place to start. Flip back and 
forth between the phase and frequency plots. After a bit it will be a lot more apparent how they relate. 

Once you get to the point that the phase plot is “user friendly” - that’s the one to watch. 

Bob

> On Sep 7, 2015, at 7:38 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> 
> Hi,
> 
> On 09/07/2015 02:23 AM, Tom Van Baak wrote:
>>>> Finally analyzing the data with Tom Van Baak's adev1 (
>>>> http://www.leapsecond.com/tools/adev1.htm)
>>>> 
>>>> [paul at localhost Documents] $ ./adev1 1 < ../datafile.txt
>> 
>> Hi Paul,
>> 
>> There's also the adev4 and adev5 tools too. But my main suggestion is to use John's TimeLab instead of a command line tool. Go to http://www.ke5fx.com/timelab/readme.htm to download.
>> 
>> It turns out your raw data is very corrupted. If you view the phase and frequency data graphically it will be apparent. This is why a self-contained graphical tool like TimeLab is ideal. Until you get a clean phase difference series, the ADEV numbers produced by a command line tool (or any tool for that matter) are sort of meaningless.
>> 
>> I've sent you a bunch of sample plots off-list.
> 
> Crash-and-burn a number of times with TimeLab is really a good way to learn a number of things. Eventually you get a good clue already on the ADEV and when you see the phase/freq plot you just go "ah, I knew it!".
> 
> Sometimes swapping between wrapped (w) and unwrapped (p) phase provides a good clue, but once you unwrap your phase correctly, swapping between phase (p) and frequency (f) views helps. Allan deviation (a) and time deviation (t) should be useful. Sometimes a modified allan (m) or Hadamard (h) deviation helps.
> 
> Experiment and measure!
> 
> Cheers,
> Magnus
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