Time nuttery in space
here's a (lengthy) paper by Todd Ely, Zaid Towfic, and Dana Sorensen about the experiments with one-way ranging on CAPSTONE (heading to the Moon).
The Iris radio had an added CSAC, and so they were able to compare performance with the raw TCXO against the CSAC against DSN's clocks, etc.
https://navi.ion.org/content/71/1/navi.633
"The Iris software radio has been updated to collect one-way Doppler and range data for potential use with deep space autonomous navigation. One-way radiometric data have found limited use because a typical radio oscillator is not sufficiently stable for use in navigation. However, Iris has been paired with a chip-scale atomic clock (CSAC) via an input signal of one pulse per second. With superior stability relative to a typical oscillator, the CSAC has the potential to provide onboard tracking data with sufficient accuracy to support a small satellite mission with modest navigation requirements. In this paper, we develop models of the Iris radio one-way Doppler and range data and analyze their performance in lab testing prior to a future inflight test on NASA’s CAPSTONE mission to the Moon. The test results confirm theoretical predictions for range precision measured between 0.38 m and 2.21 m with a range rate of 11 mm/s at 60 s."
There's a lot of discussion about where the transition from TCXO limited to CSAC limited performance is.
Disclosure: I worked on Iris and the transition from JPL design to manufacture at SDL and had discussions early on about how to do this experiment - since I had used CSACs in another space experiment. So I'm not exactly an unbiased observer, because it's one of my babies.
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
HI
Keep in mind that a “good” OCXO likely costs > $1K when new. Shopping on eBay at pennies on the dollar spoils all of us.
A low ADEV at 1 second would be below 2x10^-13. That "very good" OCXO probably would cost you $5K or more, even on eBay. You might spend a couple years shopping for something like that. It probably would involve buying multiple candidates that don’t quite make the cut.
Measurement wise, you would want something that comes in well below 1x10^-13 ADEV at 1 second. Something in the < 2x10^-14 would be the target. There are devices out there that do that sort of thing. I’d budget $20K for one of them.
This is all based on your “lowest possible” criteria. If something less than best of the best is acceptable, then the budget changes. Buying a hundred $50 10811’s and sorting them all out should get you multiple candidates below 5x10^-13. The trick is to only buy ones that have not already been sorted by somebody else …
Fun !!!
Bob
On Aug 16, 2024, at 5:00 PM, James Spottiswoode via time-nuts time-nuts@lists.febo.com 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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Hi
Heading off into the weeds a bit. The previous post was based on an OCXO approach.
Taking things a step further, a passive hydrogen maser will do significantly better than an OCXO at anything past 10 seconds. Best guess is you are looking at $100K for one of them. An active maser will do better. Figure something in the $300K to $500K range.
We still are not up to “the best”. That would get you into much more exotic devices. As you go up each order of magnitude in cost, things get better. I’m guessing that $30M is not part of the budget for this project. If it is, then there are things to look at.
Bob
On Aug 16, 2024, at 5:00 PM, James Spottiswoode via time-nuts time-nuts@lists.febo.com 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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Hi James,
author of the referenced paper here. Back then, I needed to compare time
sources and I opted for SDRs for two reasons: I already had experience
with SDRs and such devices available. Admittedly, the resulting
measurement performance surprised me, so I ended up writing multiple
papers about it. We're still using the measurement setup today to
torture GNSSDOs: https://arxiv.org/abs/2406.16037
If you're looking for a cheap and simple solution, the tinyPFA may be
your best good choice (disclaimer: I have never used the tinyPFA;
judging purely on published information). Its performance is within less
than an order of magnitude of my USRP N210 setup. It also comes as a
ready-to-use product, whereas with the SDR approach – depending on your
level of expertise – you're probably looking at several months of
software development before you have a usable and reliable measurement
setup. Back in 2016 I had to resort to hand-written vector code [1] to
get the complex-valued sample processing to run in real-time on now
ancient CPUs. Compilers' auto-vectorization and libraries have come a
long way since then, but I'd still expect it to be an uphill battle today.
Best regards,
Carsten
[1] https://gist.github.com/carstenandrich/facd709aa409cae4053b2b8d6848fc98
On 17.08.24 07:36, Erik Kaashoek via time-nuts 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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
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@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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
James Spottiswoode
Applied Mathematics & Statistics
310-270-6220
James.spottiswoode@gmail.com
Zoom: https://us06web.zoom.us/j/5657505742?pwd=d1hQUzR5SE8yMXo3ZUliRGwva2RvQT09
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@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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
James Spottiswoode
Applied Mathematics & Statistics
310-270-6220
James.spottiswoode@gmail.com
Zoom: https://us06web.zoom.us/j/5657505742?pwd=d1hQUzR5SE8yMXo3ZUliRGwva2RvQT09
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
--
Brian Flynn, 22A Biggiesknowe, Peebles, EH45 8HS. +44 (0)7969668147
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, degrees…? 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 2:19 PM, Brian Flynn via time-nuts time-nuts@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 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@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@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
James Spottiswoode
Applied Mathematics & Statistics
310-270-6220
James.spottiswoode@gmail.com
Zoom: https://us06web.zoom.us/j/5657505742?pwd=d1hQUzR5SE8yMXo3ZUliRGwva2RvQT09
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
--
Brian Flynn, 22A Biggiesknowe, Peebles, EH45 8HS. +44 (0)7969668147
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
James Spottiswoode
Applied Mathematics & Statistics
310-270-6220
James.spottiswoode@gmail.com
Zoom: https://us06web.zoom.us/j/5657505742?pwd=d1hQUzR5SE8yMXo3ZUliRGwva2RvQT09
James,
See the menu tree in the wiki:
https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.MenuTree
Can I suggest to take further support questions about the tinyPFA to the
tinyPFA support group?
https://tinydevices.org/forum/
Erik.
On 20-8-2024 4:44, James Spottiswoode via time-nuts 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, degrees…? 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