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

Tue Aug 20 07:00:18 UTC 2024

Unwrapped phase is in seconds.

I'm a happy user of the tinyPFA for my clock tinkering. I always use the
unwrapped phase USB output, logged to a file on a raspberry pi, then copied
away for analysis. No trouble logging like this for a week.
With USB logging the terminal must be open before you turn on logging,
otherwise some buffer fills up and the device freezes. Shutting down is the
reverse.

73, Thomas VE7TOA

On Mon, 19 Aug 2024 at 19:55, James Spottiswoode via time-nuts <
time-nuts at lists.febo.com> wrote:

> Dear Brian,
>
> As it turned out converting the nanoVNA to a tinyPFA was almost
> effortless.  The only slight hiccup was installing UNIX utility for loading
> the inlay correctly.  So I have recorded the noise floor of the system and
> am starting to compare phase of OXCOs.
>
> One question to the group: When you output wrapped phase (logged) from the
> tinyPFA what are the Units?  Radians, degreesâ€¦?  Neither look right when I
> unlog the numbers. This matters for me as I have written all my own code
> (in R) for getting ADEV and MADEV and for logging the phase data.  As I
> mentioned have a very bad relationship with Windows particularly when it
> comes to using a cheap Windows 10 box for data logging.  I also want to log
> the phase data continuously as control data and a machine which reboots
> every few nights for updates is a PITA.  I have spent several hours
> googling and modifying Windoze settings to no avail.  Basically it behaves
> like a corporate machine which one can't control.  Off hobbyhorse :-)
>
> 73s James
>
> > On Aug 19, 2024, at 2:19â€¯PM, Brian Flynn via time-nuts <
> time-nuts at lists.febo.com> wrote:
> >
> > 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 Iâ€™ll eventually have to get a
> N210.
> >>
> >> Many thanks - James
> >>
> >>
> >>> On Aug 16, 2024, at 10:36â€¯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,
> >>>>
> >>>> Iâ€™ve found the time-nuts archive to be incredibly useful over the
> last year - thank you all!  I have an unusual question.
> >>>>
> >>>> Iâ€™m interested in getting the lowest possible ADEV at tauâ€™s ~< 1000s
> and am not concerned about longer term drifts.  The protocol Iâ€™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 Iâ€™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 Iâ€™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
> Radioâ€ which can be found here: https://arxiv.org/pdf/1803.01438 states
> in the abstract:   â€œâ€¦ 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.â€  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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> >>> _______________________________________________
> >>> 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
> >>
> >>
> >>
> >> _______________________________________________
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> > --
> > Brian Flynn, 22A Biggiesknowe, Peebles, EH45 8HS. +44 (0)7969668147
> > _______________________________________________
> > 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
>
>
>
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