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

[Magnus Danielson]

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

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