[time-nuts] PRS10 MDEV

Tom Van Baak tvb at LeapSecond.com
Mon Oct 15 00:23:26 EDT 2018


> This is just a free running PRS10 wired to a TAPR TICC, I thought that I would
> run some stand alone tests before I brought my GPSDO in line too.

Ok, good idea to do a stand alone test. The plateau, though, is interesting and I wouldn't quite have expected that in a 1PPS vs 10 MHz self-test. Let's look into that.

> The PRS10 is the source for the 10MHz as well as reading the 1PPS output from it.

Ah, ok, that would explain the unusually low MDEV beyond tau 1000. Since you're essentially comparing the oscillator with itself you would expect the MDEV numbers to be [far] lower than the performance of an actual frequency standard.

Once you fire up your GPSDO and use that as a reference, your PRS10 ADEV/MDEV numbers will look more appropriate.

/tvb

----- Original Message ----- 
From: Chris Burford 
To: 'Tom Van Baak' ; 'Discussion of precise time and frequency measurement' ; 'Discussion of precise time and frequency measurement' 
Sent: Sunday, October 14, 2018 8:07 PM
Subject: Re: [time-nuts] PRS10 MDEV


Tom,


This is just a free running PRS10 wired to a TAPR TICC, I thought that I would run some stand alone tests before I brought my GPSDO in line too. The PRS10 is the source for the 10MHz as well as reading the 1PPS output from it.


Chris


-----------------------------------------
From: "Tom Van Baak" 
To: "Discussion of precise time and frequency measurement"
Cc: 
Sent: Sunday October 14 2018 9:45:46PM
Subject: Re: [time-nuts] PRS10 MDEV

Chris,

Thanks for sharing the plot.

What instrument are you using to make the measurements? And what frequency reference is being used? Is this a free-running PRS10, or is it locked to GPSDO with some time constant?

Is that same GPSDO being used as a reference for your measurements? The plateau looks very much like GPSDO behavior and the slide into e-14 and e-15 territory looks like you're measuring a PLL.

/tvb

----- Original Message ----- 
From: "Chris Burford" <CBURFORD1 at austin.rr.com>
To: <time-nuts at lists.febo.com>
Sent: Sunday, October 14, 2018 7:07 PM
Subject: [time-nuts] PRS10 MDEV


> Hello All,
> I've collected several data sets over the last few days from my RFS
> and I'm puzzled by what I'm seeing. A link to the plot is here:
> https://drive.google.com/open?id=10Kk8Cqx7es0SXf2H5AldiQkBo8nIfNMT
/> > I'm looking at the averaging periods from about 100 thru 400 tau and
> noticed a "plateau" or a brief level off period and then it proceeds
> down and right again. Is this flat area a function of the averaging
> algorithms for the MDEV or is it something else?
> I have spent considerable time in reading "Techniques for Frequency
> Stability Analysis" by W.J. Riley and a host of other publications
> (NIST, etc) in preparation for this. I would enjoy hearing from any
> readers that may have some insight as to what I'm seeing and or
> possible causes.
> Thanks for reading.
> Chris
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> time-nuts mailing list -- time-nuts at lists.febo.com
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