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

[Brian Flynn]

Dear James,

I am new to this list but have been taking an interest in accurate 
frequency standards for my ham radio interests. I have just bought a 
Hugen NanoVNA-H4 from Zeenko on Aliexpress, for conversion to a TinyPFA. 
I was doing it on a Windoze system but the process went very smoothly 
for me. I hope that was of use.  I followed the instructions on:

https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.FW

and all went well.

I have various linux systems around the place but have a fairly catholic 
taste in operating systems but also understand your caution. ;-)

73s

Brian GM8BJF

On 18/08/2024 18:00, James Spottiswoode via time-nuts wrote:
> Erik,
>
> Many thanks indeed for your comments.  I note that in the last link you sent:  https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.Examples the instrument used is listed in the results is a tinyDMTD - is this the same device as the tinyPFA?   I happen to already have a nanoVNA-H4 so it looks like I can load the SW and convert it to a tinyPFA.  Are there any gotchas in this process?  I try to maintain a Windows free zone here :-) but it looks like dfu-util will run under BSD on a Mac which is my preferred OS. This may a quick and cheap way to get a Dual Mixer Time Difference going but I suspect that for publication purposes I’ll eventually have to get a N210.
>
> Many thanks - James
>
>
>> On Aug 16, 2024, at 10:36 PM, Erik Kaashoek via time-nuts <time-nuts at lists.febo.com> wrote:
>>
>> 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
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
> James Spottiswoode
> Applied Mathematics & Statistics
> 310-270-6220
> James.spottiswoode at gmail.com
> Zoom:  https://us06web.zoom.us/j/5657505742?pwd=d1hQUzR5SE8yMXo3ZUliRGwva2RvQT09
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com
-- 
Brian Flynn, 22A Biggiesknowe, Peebles, EH45 8HS. +44 (0)7969668147