[time-nuts] 53230A noise floor

[Bob Camp]

Hi

You may want to take a look at some of Bill Riley’s (and others) papers on how pre-filtering
can lead to errors in an ADEV calculation. 

Simply put - the frequency mode is a filter and it is not the right one to have in front of an ADEV
calculation. 

Bob

> On Apr 3, 2015, at 5:49 AM, Anders Wallin <anders.e.e.wallin at gmail.com> wrote:
> 
> Hi all,
> 
> I ran some tests on a new 53230A counter that just arrived:
> http://www.anderswallin.net/2015/04/keysight-53230a-noise-floor-test/
> 
> The time-interval single-shot noise and resulting ADEV seems easy enough to
> explain.
> 
> I didn't yet have time to look closely at Enrico Rubiola's notes over here:
> http://rubiola.org/pdf-slides/2012T-IFCS-Counters.pdf
> There is probably a good explanation for the ADEV-level in standard
> (pi-counting?) reciprocal frequency counter mode as well as the roughly
> 1/sqrt(10) enhancement in ADEV when increasing the gate-time 10-fold.
> 
> on another note:
> The discussion on phase-noise <-> ADEV calculations earlier was
> interesting. Datasets (synthetic or real) with known correct ADEVs and
> phase-noise-spectra would be a good addition to allantools and a motivation
> to add code for the phase-noise <-> ADEV conversion.
> 
> cheers,
> Anders
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