[time-nuts] Re: Question about ADEV for tau < 1000s

[Erik Kaashoek]

Jim,

For accurate phase comparison without much effort and cost you may have 
a look at the tinyPFA : 
https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.HomePage
An example of the expected performance when connected to Timelab: 
https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.TimeLab
Some measurements use the name tinyDMTD instead of tinyPFA but its the 
same device.
Here is are some examples measuring OCXO/DOCXO and Rb: 
https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.Examples
You can search this list for more info

Erik.


On 16-8-2024 23:00, James Spottiswoode via time-nuts wrote:
> Hi Time-nuts Experts,
>
> I’ve found the time-nuts archive to be incredibly useful over the last year - thank you all!  I have an unusual question.
>
> I’m interested in getting the lowest possible ADEV at tau’s ~< 1000s and am not concerned about longer term drifts.  The protocol I’m using is based on comparing phase or frequency between two 10 MHz frequency standards a few meters apart in the lab.   Currently I am comparing a pair of OSC5A2BO2 OXCOs using an Agilent 53230A running with a 1 sec gate time and using the undocumented RCON command.  I am seeing a short term ADEV of 3e-11 at tau = 100s. I would like to get an order of magnitude or more better than this if possible without breaking the bank!
>
>  From the research I’ve done it looks like high end OCXOs are the best bet for lowest ADEV but many are designed for high acceleration environments, which I do not need for static references. The best I’ve found so far is the Connor-Winfield OH320-LA.  Does anyone here have a better suggestion? Are double oven controlled oscillators a better way to go?
>
> For frequency or phase comparisons between the pair of OCXOs an SDR looks like a better option than the 53230. This paper: "High-Precision Measurement of Sine and Pulse Reference Signals using Software-Defined Radio” which can be found here: https://arxiv.org/pdf/1803.01438 states in the abstract:   “… The measurement system is implemented and verified using the Universal Software Radio Peripheral (USRP) N210 by Ettus Research LLC. Applying standard 10MHz and 1PPS reference signals for testing, a measurement precision (standard deviation) of 0.36ps and 16.6 ps is obtained, respectively.”  This is considerably better than is achievable with the 53230A.
>
> So I have two asks:  Advice on the lowest ADEV OCXO for tau < 1000s and your thoughts on the SDR based method described above for high precision phase measurements.
>
> With many thanks in advance,
>
> James
>
> James Spottiswoode  KG6SMH
>
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