[time-nuts] Measuring ADEV using TBolt-Tic tester

Azelio Boriani azelio.boriani at screen.it
Fri Oct 7 18:59:58 UTC 2011

I know that few of the GPS constellation satellites carry a Cs clock instead
of the Rb one: is it possible to take advantage from this? I think not
because Cs and Rb satellites are equally well steered but using the masking
options of GPS receivers maybe that Cs clocks can help.

On Fri, Oct 7, 2011 at 8:34 PM, Magnus Danielson <magnus at rubidium.dyndns.org
> wrote:

> On 07/10/11 19:00, WarrenS wrote:
>> Use the (J J) command to rezero the Phase plot (plus the cable delay if
>> desired)
>> and then read or adjust the Osc freq on the ppt plot.
>> With LadyHeather's filter off (F D 0) useful resolution is about 1e-10
>> in one second,
>> With the filter set to 10 sec (F D 10) useful resolution is near 1e-11
>> in well under one minute
>> With the filter set to 100 sec, resolution is around 1e-11 in a few
>> minutes. adding a trend line helps (G O L)
> Be a little careful here. Pre-filtering will scale white-noise ADEV
> linearly, please see the Power noise table I put in the ADEV wiki article:
> http://en.wikipedia.org/wiki/**Allan_variance#Power-law_noise<http://en.wikipedia.org/wiki/Allan_variance#Power-law_noise>
> f_H is the system bandwidth and changing the pre-filtering you do change
> this property. The end result is that your h_2 amount of white phase noise
> is the same but only gives different ADEV values, and is not the result of
> improved noise floor.
> However, you can use various settings to separate between WPM and FPM noise
> levels.
> Cheers,
> Magnus
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