[time-nuts] Re: Repeatability of stability measurements

[Magnus Danielson]

Hi Hans-Georg,

Does the E1740A also has the STP2945 as timing reference?

First of all, you have nice illustrations of the white phase modulation 
noise slopes, of tau^1.5 as expected in the MDEV. Trouble is, it's not 
pure WPM noise, but a mixture of the noise and the quantization effect. 
So, it would be good if the E1740A is known to either free-float or 
locked to one of the references.

By using MDEV you utilize the averaging benefits over the ADEV, giving a 
sqrt(1E7) benefit as you hit 1 s. However, while your slope will roughly 
coincide with the single-shot resolution, it's exact position is more 
complex. The relative frequency may cause the resolution to go up and 
down due to systematic nature, and the noise in addition to the signal 
will intermodulate with the systematics.

If you have both these long-term locked to a stable source, it should 
stabilize. Also, since you have a slow beating pattern of the 
systematics, exactly when you measure may decide if it is high or low on 
that valey.

You very clearly see systematic noise in the phase noise. These are for 
sure fighing against you.

Do more of these phase noise analysis and see if any of the systematics 
there coinside with high or low noise, or if indeed the noise floor 
moves up and down.

This slope is more tricky than it get credit for.

Cheers,
Magnus

On 2022-06-23 22:56, Hans-Georg Lehnard via time-nuts wrote:
> I am trying to find out the limits of my measuring devices and
> oscillators. Therefore I made 2 series of measurements with the same
> conditions. In the first series I got 1 out of 10 and in the second 2
> out of 10 results with much less noise. I looked at the results in
> Timelab and then exported one good and one not so good result (recorded
> 4 minutes earlier) to stable32 for further analysis. Is this a problem
> of my measurement setup or an artifact in the measurements. My
> measurement device is a HP E1740A Time interval analyzer with about 50ps
> (4.8828124999999998046875e-11) resolution. A Samsung STP2945LF (free
> running) from my GPSDO as reference and the reference output of my
> BG7TBL FA2 as measurement object. Attached are the results from the 2
> series and the 2 further analyzed from the first series.
>
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