CTI OSC5A2B02 OXCO testing
Hi,
I've tried to avoid time-nutting for a long time, but I have lost the battle.
I bought 10 bare CTI modules on ebay for $2.93 each which I wish to test over a long period of time. I can set up 2-4 GHz SMA relay switching, GPSDO reference etc. Question is, what to read the frequency with. My 5386A with a GPSDO isn't precise enough.
I don't know anything about it yet, but nanoPFA FW on a nanoVNA H4 looks attractive. Are there other instruments/methods to consider? I have a crazy mid 90's lab, so a bit more is not an issue other than where to put it.
All I'm looking for is a pebble tossed in the right direction. Current plan is an LM399 reference with emitter followers driving Vref on the OXCOs, very stiff PSU and a fairly stable temperature.
Thanks,
Reg
The way I would approach it as a beginner is with a 10mhz to 1hz picdiv and
a timestamping counter like a tapr ticc. Both of
Feed the ticc's reference clock with your 10mhz reference. Then run the
10mhz out of the ocxo into the picdiv which will result in 1hz output.
Then run this 1hz into one of the ticc channels.
That way you'll get a high accuracy timestamp of each 10,000,000th pulse.
If they are exactly 1 second apart you're right on 10mhz. This last
statement is oversimplified and ignores all sorts of potential errors such
as accuracy of the clock source and other sources of measurement noise but
is good enough to get you started down the time nuts path.
Note that by logging each timestamp you can then feed that into timelab or
another other similar tool and get some detailed statistical analysis of
the ocxo over various time periods.
One other method which may use hardware you already have is to feed your 10
mhz reference clock into one channel on a 2 or more channel oscilloscope
and the ocxo output into the second channel. Trigger off of the first
channel and watch how much the signal on the second channel drifts. If
they are both on the same frequency there will be no relative drift. If
they are different they will drift and the rate will increase the further
apart they are. There is math you can do to determine how off if you can
time how long it takes a single cycle to drift. Note that it doesn't take
much of a difference for this method to not be usable as you quickly get
drift rates which exceed what a human can interpret on the screen.
Note that all of the above is just to get you started. Like I implied
there is a lot of details I left out or oversimplified, but that should get
you started.
On Fri, Jun 2, 2023, 9:55 PM Reginald Beardsley via time-nuts <
time-nuts@lists.febo.com> wrote:
Hi,
I've tried to avoid time-nutting for a long time, but I have lost the
battle.
I bought 10 bare CTI modules on ebay for $2.93 each which I wish to test
over a long period of time. I can set up 2-4 GHz SMA relay switching,
GPSDO reference etc. Question is, what to read the frequency with. My
5386A with a GPSDO isn't precise enough.
I don't know anything about it yet, but nanoPFA FW on a nanoVNA H4 looks
attractive. Are there other instruments/methods to consider? I have a
crazy mid 90's lab, so a bit more is not an issue other than where to put
it.
All I'm looking for is a pebble tossed in the right direction. Current
plan is an LM399 reference with emitter followers driving Vref on the
OXCOs, very stiff PSU and a fairly stable temperature.
Thanks,
Reg
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A bit of background. I've got an absurd amount of HPAK kit. I bought a pair of used OXCOs on new PCBs via ebay or Amazon, I forget which. I set up a pair of splitters and fed the GPSDO to the 5386A counter and a DSO, did the same with one OXCO output and fed the input to the 5386A and the DSO along with a second OXCO just feeding the DSO.
I was able to set both units to the 0.1 ppb limit of the 5386A and made them up in SMA-F and BNC-F versions in small plastic cases.
The OXCOs have a 0.02 ppb/s stability spec which is presumably what you could expect from it in a GPSDO setting. The 10 year aging rate is stated as 0.4 ppb/yr.
I bought 10 bare OXCOs for $29.30 delivered.
General plan:
Wire up all 10 to use a common PSU
Feed an LM399 reference voltage to voltage followers that drive a separate divider for each OXCO
Place a thermistor and resistor on each OXCO for use as a heating element and sensor to warm each unit above the threshold of the internal heater so the latter does not turn on and there are no temperature gradients across the device.
Set up a 10 port SMA relay tree to allow switching a phase comparator fed by a GPSDO and the switch output. *** The nature of this phase comparator is what I want to determine **
Place in a thermally controlled chamber and log the references for an extended period.
At the moment my best option appears to be a nanoVNA H4 with the tinyPFA FW loaded. However, an HP equivalent would be very desirable. I'm an analog, RF oriented guy with a bit of a metrology bent and have no idea what HP made to measure such things. I've got 4 racks of HP and Tek gear. I would hardly notice more. That is my preferred solution. I have one of Leo Bodnar's dual channel GPSDOs.
Some years ago I got mixed up in basis pursuit to solve the heat equation. The answer is an infinite sum of exponentials. When I realized I was solving problems with 50,000 unknowns and fewer than 100 equations I became really fascinated as to how this could be possible. Which led to Donoho and Candes work in 2004-2008 and 3 years of reading math papers.
The aging behavior of crystals is well documented. Numerical experiment has shown that given measured curves I can predict aging to within a few percent for as long as I have history.
The aim of project is to characterize these OXCOs for 6-12 months. Then incorporate N of them in a single unit with an MCU that applies a voltage change to adjust for the ~0.001 ppb/day aging. And which periodically resynchronizes all N OXCOs along with applying any ambient temperature corrections required. Success is 0.1 ppb/yr for a 4 OXCO system. Possibly not achievable, but a worthy goal.
Why? Well, because I can and I've never seen any mention of doing it. Will I do exactly what I described? I hope not. I joined the list to get advice on how to do better.
Reg
On Saturday, June 3, 2023 at 12:41:33 AM CDT, Forrest Christian (List Account) <lists@packetflux.com> wrote:
The way I would approach it as a beginner is with a 10mhz to 1hz picdiv and a timestamping counter like a tapr ticc. Both of
Feed the ticc's reference clock with your 10mhz reference. Then run the 10mhz out of the ocxo into the picdiv which will result in 1hz output. Then run this 1hz into one of the ticc channels.
That way you'll get a high accuracy timestamp of each 10,000,000th pulse. If they are exactly 1 second apart you're right on 10mhz. This last statement is oversimplified and ignores all sorts of potential errors such as accuracy of the clock source and other sources of measurement noise but is good enough to get you started down the time nuts path.
Note that by logging each timestamp you can then feed that into timelab or another other similar tool and get some detailed statistical analysis of the ocxo over various time periods.
One other method which may use hardware you already have is to feed your 10 mhz reference clock into one channel on a 2 or more channel oscilloscope and the ocxo output into the second channel. Trigger off of the first channel and watch how much the signal on the second channel drifts. If they are both on the same frequency there will be no relative drift. If they are different they will drift and the rate will increase the further apart they are. There is math you can do to determine how off if you can time how long it takes a single cycle to drift. Note that it doesn't take much of a difference for this method to not be usable as you quickly get drift rates which exceed what a human can interpret on the screen.
Note that all of the above is just to get you started. Like I implied there is a lot of details I left out or oversimplified, but that should get you started.
On Fri, Jun 2, 2023, 9:55 PM Reginald Beardsley via time-nuts time-nuts@lists.febo.com wrote:
Hi,
I've tried to avoid time-nutting for a long time, but I have lost the battle.
I bought 10 bare CTI modules on ebay for $2.93 each which I wish to test over a long period of time. I can set up 2-4 GHz SMA relay switching, GPSDO reference etc. Question is, what to read the frequency with. My 5386A with a GPSDO isn't precise enough.
I don't know anything about it yet, but nanoPFA FW on a nanoVNA H4 looks attractive. Are there other instruments/methods to consider? I have a crazy mid 90's lab, so a bit more is not an issue other than where to put it.
All I'm looking for is a pebble tossed in the right direction. Current plan is an LM399 reference with emitter followers driving Vref on the OXCOs, very stiff PSU and a fairly stable temperature.
Thanks,
Reg
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Or use a picPET and feed the ocxo output to the ref input and the 1pps pulse from a GPS into the pulse input. I've done this with a pp07 to check my CTI ocxo frequency.Sent from my Galaxy
-------- Original message --------From: "Forrest Christian (List Account) via time-nuts" time-nuts@lists.febo.com Date: 03/06/2023 07:43 (GMT+00:00) To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com Cc: Reginald Beardsley pulaskite@yahoo.com, "Forrest Christian (List Account)" lists@packetflux.com Subject: [time-nuts] Re: CTI OSC5A2B02 OXCO testing The way I would approach it as a beginner is with a 10mhz to 1hz picdiv anda timestamping counter like a tapr ticc. Both ofFeed the ticc's reference clock with your 10mhz reference. Then run the10mhz out of the ocxo into the picdiv which will result in 1hz output. Then run this 1hz into one of the ticc channels.That way you'll get a high accuracy timestamp of each 10,000,000th pulse. If they are exactly 1 second apart you're right on 10mhz. This laststatement is oversimplified and ignores all sorts of potential errors suchas accuracy of the clock source and other sources of measurement noise butis good enough to get you started down the time nuts path.Note that by logging each timestamp you can then feed that into timelab oranother other similar tool and get some detailed statistical analysis ofthe ocxo over various time periods.One other method which may use hardware you already have is to feed your 10mhz reference clock into one channel on a 2 or more channel oscilloscopeand the ocxo output into the second channel. Trigger off of the firstchannel and watch how much the signal on the second channel drifts. Ifthey are both on the same frequency there will be no relative drift. Ifthey are different they will drift and the rate will increase the furtherapart they are. There is math you can do to determine how off if you cantime how long it takes a single cycle to drift. Note that it doesn't takemuch of a difference for this method to not be usable as you quickly getdrift rates which exceed what a human can interpret on the screen.Note that all of the above is just to get you started. Like I impliedthere is a lot of details I left out or oversimplified, but that should getyou started.On Fri, Jun 2, 2023, 9:55 PM Reginald Beardsley via time-nuts time-nuts@lists.febo.com wrote:> Hi,>> I've tried to avoid time-nutting for a long time, but I have lost the> battle.>> I bought 10 bare CTI modules on ebay for $2.93 each which I wish to test> over a long period of time. I can set up 2-4 GHz SMA relay switching,> GPSDO reference etc. Question is, what to read the frequency with. My> 5386A with a GPSDO isn't precise enough.>> I don't know anything about it yet, but nanoPFA FW on a nanoVNA H4 looks> attractive. Are there other instruments/methods to consider? I have a> crazy mid 90's lab, so a bit more is not an issue other than where to put> it.>> All I'm looking for is a pebble tossed in the right direction. Current> plan is an LM399 reference with emitter followers driving Vref on the> OXCOs, very stiff PSU and a fairly stable temperature.>> Thanks,> Reg> _______________________________________________> 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.comTo unsubscribe send an email to time-nuts-leave@lists.febo.com
The CTI modules may be different in short term stability ( below 100
seconds ) but for longer periods they all will drift more then any gpsdo or
rubidium.
So simplest is to use the tinyPFA to compare them in pairs till you have
found the most stable pair. This would take less then 1 hour per pair due
to the excellent resolution of the tinyPFA.
Then you compare one of the best CTI against your gpsdo without antenna
attached so the OCXO is free running. This will tell you if the short term
stability of your gpsdo is better or worse then the CTI.
And once this is known you can start to look at the long term using all the
CTI versus your gpsdo, again using the tinyPFA as the long term stability
of the CTI modules is guaranteed to be worse then the long term phase
stability of the tinyPFA
Erik
Using the tinyPFA to measure each of th
On Sat, Jun 3, 2023, 08:43 Forrest Christian (List Account) via time-nuts <
time-nuts@lists.febo.com> wrote:
The way I would approach it as a beginner is with a 10mhz to 1hz picdiv and
a timestamping counter like a tapr ticc. Both of
Feed the ticc's reference clock with your 10mhz reference. Then run the
10mhz out of the ocxo into the picdiv which will result in 1hz output.
Then run this 1hz into one of the ticc channels.
That way you'll get a high accuracy timestamp of each 10,000,000th pulse.
If they are exactly 1 second apart you're right on 10mhz. This last
statement is oversimplified and ignores all sorts of potential errors such
as accuracy of the clock source and other sources of measurement noise but
is good enough to get you started down the time nuts path.
Note that by logging each timestamp you can then feed that into timelab or
another other similar tool and get some detailed statistical analysis of
the ocxo over various time periods.
One other method which may use hardware you already have is to feed your 10
mhz reference clock into one channel on a 2 or more channel oscilloscope
and the ocxo output into the second channel. Trigger off of the first
channel and watch how much the signal on the second channel drifts. If
they are both on the same frequency there will be no relative drift. If
they are different they will drift and the rate will increase the further
apart they are. There is math you can do to determine how off if you can
time how long it takes a single cycle to drift. Note that it doesn't take
much of a difference for this method to not be usable as you quickly get
drift rates which exceed what a human can interpret on the screen.
Note that all of the above is just to get you started. Like I implied
there is a lot of details I left out or oversimplified, but that should get
you started.
On Fri, Jun 2, 2023, 9:55 PM Reginald Beardsley via time-nuts <
time-nuts@lists.febo.com> wrote:
Hi,
I've tried to avoid time-nutting for a long time, but I have lost the
battle.
I bought 10 bare CTI modules on ebay for $2.93 each which I wish to test
over a long period of time. I can set up 2-4 GHz SMA relay switching,
GPSDO reference etc. Question is, what to read the frequency with. My
5386A with a GPSDO isn't precise enough.
I don't know anything about it yet, but nanoPFA FW on a nanoVNA H4
looks
attractive. Are there other instruments/methods to consider? I have a
crazy mid 90's lab, so a bit more is not an issue other than where to put
it.
All I'm looking for is a pebble tossed in the right direction. Current
plan is an LM399 reference with emitter followers driving Vref on the
OXCOs, very stiff PSU and a fairly stable temperature.
Thanks,
Reg
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
Hi
By far the biggest issue with any small OCXO is the “stable temperature”
part of things. Any sort of draft is going to be a really big deal. HVAC cuts
in … problem. Door to the lab opens and closes ….problem. Folks move around
in the lab … problem. Dog wags tail ..
I would spend some time coming up with some sort of enclosure that at the
very least keeps the drafts at bay. You don’t want things buried under a big
blanket, the OCXO’s will overheat. Enclosures build of water bottles are indeed
an option. Monitoring the temperature inside the enclosure is a very good idea.
Simply shorting the EFC to ground is a quick and simple way to handle that side
of things. They will be off frequency. The long term data still should be representative
of the part. Having them at a range of frequencies just might help with various cross
talk issues.
Keeping any of this stable while plugging the parts into some sort of board is a
challenge. Soldering them into a board is great, un-soldering them may well
damage them. How this impacts things depends a lot on a whole lot of details.
Switching wise, kill the signal at the oscillator. Don’t let it head over to a switch. It’s
a CMOS output device. A gate will do that pretty well. You need some sort of
buffer anyway. These parts will not drive a chunk of coax cable.
If you are looking for aging, a reading an hour should be adequate. If you are trying
for ADEV, then you only want to look at one device at a time. One part in the fixture,
all the rest on the other side of the room …..
As noted in other messages, a cute way to do this is to divide all the OCXO’s to 1 pps
and then look at time drift. Log the time offset once an hour. Anything that gives you
a nanosecond-ish reading is plenty good enough.
Fun !!!
Bob
On Jun 2, 2023, at 7:14 PM, Reginald Beardsley via time-nuts time-nuts@lists.febo.com wrote:
Hi,
I've tried to avoid time-nutting for a long time, but I have lost the battle.
I bought 10 bare CTI modules on ebay for $2.93 each which I wish to test over a long period of time. I can set up 2-4 GHz SMA relay switching, GPSDO reference etc. Question is, what to read the frequency with. My 5386A with a GPSDO isn't precise enough.
I don't know anything about it yet, but nanoPFA FW on a nanoVNA H4 looks attractive. Are there other instruments/methods to consider? I have a crazy mid 90's lab, so a bit more is not an issue other than where to put it.
All I'm looking for is a pebble tossed in the right direction. Current plan is an LM399 reference with emitter followers driving Vref on the OXCOs, very stiff PSU and a fairly stable temperature.
Thanks,
Reg
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com