[time-nuts] The Nature of Noise

Bob Stewart bob at evoria.net
Thu Jun 30 21:43:32 EDT 2016


Thanks Bob and Attila,
This problem with the Cs kind of brought the whole question of noise and what ADEVs mean into focus for me.  Like most newbies, I had read about the ever increasing stability of time standards and wondered how they could actually know that they were better.  I've seen the term 3-cornered hat bandied about, but I didn't really grock it until now.
Bob -----------------------------------------------------------------------------------
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      From: Bob Camp <kb8tq at n1k.org>
 To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Thursday, June 30, 2016 4:27 PM
 Subject: Re: [time-nuts] The Nature of Noise
   
Hi

If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is 
possible that you are getting bad information. This is a classic argument about comparing devices from the 
same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient. 

Bob

> On Jun 30, 2016, at 2:30 PM, Bob Stewart <bob at evoria.net> wrote:
> 
> With my recent Cs problems, I've been wondering about the subject of noise generation and measurement.  Specifically, my question is this:  Let's say that I have 3 disciplined oscillators: A, B, and C.  So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high.  Can I then say that both A and B are low noise devices?  Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
> 
> Bob - AE6RV -----------------------------------------------------------------------------------
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