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RP

Ross P

Wed, Jun 8, 2022 2:04 AM

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of reference time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of reference time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

BK

Bob kb8tq

Wed, Jun 8, 2022 4:27 AM

Hi

Simple answer is: no.

More complete answer is: no

There is a lot more to stability than just the crystal cut. Having this or that cut is
in no way a guarantee that the result is “better” than some other cut. Indeed there
are more exotic cuts than the SC that improve on this or that. There are also mounting
/ fabrication techniques that improve on this or that, regardless of cut.

All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut
alternative. Various improvements here or there are likely to make it a bit better than
the other examples …. ( but not always )

Bob

On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts time-nuts@lists.febo.com wrote:

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer
ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

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Hi Simple answer is: no. More complete answer is: no There is a lot more to stability than just the crystal cut. Having this or that cut is in no way a guarantee that the result is “better” than some other cut. Indeed there are more exotic cuts than the SC that improve on this or that. There are also mounting / fabrication techniques that improve on this or that, regardless of cut. All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut alternative. Various improvements here or there are likely to make it a bit better than the other examples …. ( but not always ) Bob > On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote: > > Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. > Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer > ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. > Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

MD

Magnus Danielson

Wed, Jun 8, 2022 11:27 AM

Hi,

I agree in general. However, I do see that other work to get good
resulst have been done when SC-cut is considered, so rather than SC-cut
as a cut is better, it becomes somewhat of a tell-tale of that other
work being done properly. I.e. it is meaningless to take the step to
SC-cut when other defects dominate so the SC-cut properties only makes
things more expensive than the AT-cut.

As far as I remember and know, you can achieve about the same
phase-noise properties as you hit about the same bandwidth from the Q,
and noise contribution is about the same. So, it boils down to do the
supporting amplifier well.

Cheers,
Magnus

On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote:

Hi

Simple answer is: no.

More complete answer is: no

There is a lot more to stability than just the crystal cut. Having this or that cut is
in no way a guarantee that the result is “better” than some other cut. Indeed there
are more exotic cuts than the SC that improve on this or that. There are also mounting
/ fabrication techniques that improve on this or that, regardless of cut.

All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut
alternative. Various improvements here or there are likely to make it a bit better than
the other examples …. ( but not always )

Bob

On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts time-nuts@lists.febo.com wrote:

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer
ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hi, I agree in general. However, I do see that other work to get good resulst have been done when SC-cut is considered, so rather than SC-cut as a cut is better, it becomes somewhat of a tell-tale of that other work being done properly. I.e. it is meaningless to take the step to SC-cut when other defects dominate so the SC-cut properties only makes things more expensive than the AT-cut. As far as I remember and know, you can achieve about the same phase-noise properties as you hit about the same bandwidth from the Q, and noise contribution is about the same. So, it boils down to do the supporting amplifier well. Cheers, Magnus On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote: > Hi > > Simple answer is: no. > > More complete answer is: no > > There is a lot more to stability than just the crystal cut. Having this or that cut is > in no way a guarantee that the result is “better” than some other cut. Indeed there > are more exotic cuts than the SC that improve on this or that. There are also mounting > / fabrication techniques that improve on this or that, regardless of cut. > > All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut > alternative. Various improvements here or there are likely to make it a bit better than > the other examples …. ( but not always ) > > Bob > >> On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote: >> >> Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. >> Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer >> ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. >> Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp >> >> _______________________________________________ >> 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

RP

Ross P

Wed, Jun 8, 2022 6:01 PM

Hi,So, highest short term stability depends on the Q of the crystal and quality of the feedback circuit. In that case, an AT-cut with a low noise feedback amplifier will be as good as an SC-cut with the same amp. Does pulling the oscillator affect the short term walk?rp

On Wednesday, June 8, 2022 at 10:44:24 AM PDT, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote:

Hi,

I agree in general. However, I do see that other work to get good
resulst have been done when SC-cut is considered, so rather than SC-cut
as a cut is better, it becomes somewhat of a tell-tale of that other
work being done properly. I.e. it is meaningless to take the step to
SC-cut when other defects dominate so the SC-cut properties only makes
things more expensive than the AT-cut.

As far as I remember and know, you can achieve about the same
phase-noise properties as you hit about the same bandwidth from the Q,
and noise contribution is about the same. So, it boils down to do the
supporting amplifier well.

Cheers,
Magnus

On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote:

Hi

Simple answer is: no.

More complete answer is: no

There is a lot more to stability than just the crystal cut. Having this or that cut is
in no way a guarantee that the result is “better” than some other cut. Indeed there
are more exotic cuts than the SC that improve on this or that. There are also mounting
/ fabrication techniques that improve on this or that, regardless of cut.

All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut
alternative. Various improvements here or there are likely to make it a bit better than
the other examples …. ( but not always )

Bob

On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts time-nuts@lists.febo.com wrote:

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer
ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com

Hi,So, highest short term stability depends on the Q of the crystal and quality of the feedback circuit. In that case, an AT-cut with a low noise feedback amplifier will be as good as an SC-cut with the same amp. Does pulling the oscillator affect the short term walk?rp On Wednesday, June 8, 2022 at 10:44:24 AM PDT, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote: Hi, I agree in general. However, I do see that other work to get good resulst have been done when SC-cut is considered, so rather than SC-cut as a cut is better, it becomes somewhat of a tell-tale of that other work being done properly. I.e. it is meaningless to take the step to SC-cut when other defects dominate so the SC-cut properties only makes things more expensive than the AT-cut. As far as I remember and know, you can achieve about the same phase-noise properties as you hit about the same bandwidth from the Q, and noise contribution is about the same. So, it boils down to do the supporting amplifier well. Cheers, Magnus On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote: > Hi > > Simple answer is: no. > > More complete answer is: no > > There is a lot more to stability than just the crystal cut. Having this or that cut is > in no way a guarantee that the result is “better” than some other cut. Indeed there > are more exotic cuts than the SC that improve on this or that. There are also mounting > / fabrication techniques that improve on this or that, regardless of cut. > > All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut > alternative. Various improvements here or there are likely to make it a bit better than > the other examples …. ( but not always ) > > Bob > >> On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote: >> >> Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. >> Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer >> ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. >> Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp >> >> _______________________________________________ >> 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 _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com

G

ghf@hoffmann-hochfrequenz.de

Wed, Jun 8, 2022 6:42 PM

Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts:

As far as I remember and know, you can achieve about the same
phase-noise properties as you hit about the same bandwidth from the Q,
and noise contribution is about the same. So, it boils down to do the
supporting amplifier well.

But SC can tolerate more power, so you may get more distance to the
thermal noise floor.

cheers, Gerhard

Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts: > As far as I remember and know, you can achieve about the same > phase-noise properties as you hit about the same bandwidth from the Q, > and noise contribution is about the same. So, it boils down to do the > supporting amplifier well. But SC can tolerate more power, so you may get more distance to the thermal noise floor. cheers, Gerhard

HG

hans-georg@lehnard.de

Wed, Jun 8, 2022 7:00 PM

Hi,

read this paper from Connor-Winfield about differences AT/SC cuts.

http://www.conwin.com/pdfs/at_or_sc_for_ocxo.pdf

Am 2022-06-08 04:04, schrieb Ross P via time-nuts:

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of

refer

ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

time-nuts mailing list -- time-nuts@lists.febo.com
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Hi, read this paper from Connor-Winfield about differences AT/SC cuts. http://www.conwin.com/pdfs/at_or_sc_for_ocxo.pdf Am 2022-06-08 04:04, schrieb Ross P via time-nuts: > Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. > Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer > ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. > Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

MD

Magnus Danielson

Wed, Jun 8, 2022 7:17 PM

Hi Gerhard,

On 2022-06-08 20:42, ghf@hoffmann-hochfrequenz.de wrote:

Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts:

As far as I remember and know, you can achieve about the same
phase-noise properties as you hit about the same bandwidth from the Q,
and noise contribution is about the same. So, it boils down to do the
supporting amplifier well.

But SC can tolerate more power, so you may get more distance to the
thermal noise floor.

Good point. It shifts the drive-level issue compared to AT-cut.

Cheers,
Magnus

Hi Gerhard, On 2022-06-08 20:42, ghf@hoffmann-hochfrequenz.de wrote: > Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts: > >> As far as I remember and know, you can achieve about the same >> phase-noise properties as you hit about the same bandwidth from the Q, >> and noise contribution is about the same. So, it boils down to do the >> supporting amplifier well. > > But SC can tolerate more power, so you may get more distance to the > thermal noise floor. Good point. It shifts the drive-level issue compared to AT-cut. Cheers, Magnus

BK

Bob kb8tq

Wed, Jun 8, 2022 9:17 PM

Hi

The stability depends on a long list of things. Since you can get higher
Q with an AT than you can with an SC, if Q was all that mattered, the AT
would be the king of the hill.

The oscillator circuit matters, but different parts of it matter in different ways.
The things you might do for low phase noise at a 100KHz offset might be
a bad idea if very good ADEV at 100 seconds was the target.

Tuning any high Q circuit very far off frequency probably is not a great idea.
Keeping all of the “optimizations” on target over a wide pull range is not at
all simple.

If you are designing an OCXO from scratch, there is a lot to learn and hundreds
of papers out there to get you started. If you are buying one, things are a bit
more simple. You look at the spec sheet and decide if it’s going to do the job
or not. Worst case, you buy a couple and test them.

Bob

On Jun 8, 2022, at 10:01 AM, Ross P via time-nuts time-nuts@lists.febo.com wrote:

Hi,So, highest short term stability depends on the Q of the crystal and quality of the feedback circuit. In that case, an AT-cut with a low noise feedback amplifier will be as good as an SC-cut with the same amp. Does pulling the oscillator affect the short term walk?rp

On Wednesday, June 8, 2022 at 10:44:24 AM PDT, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote:

Hi,

I agree in general. However, I do see that other work to get good
resulst have been done when SC-cut is considered, so rather than SC-cut
as a cut is better, it becomes somewhat of a tell-tale of that other
work being done properly. I.e. it is meaningless to take the step to
SC-cut when other defects dominate so the SC-cut properties only makes
things more expensive than the AT-cut.

As far as I remember and know, you can achieve about the same
phase-noise properties as you hit about the same bandwidth from the Q,
and noise contribution is about the same. So, it boils down to do the
supporting amplifier well.

Cheers,
Magnus

On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote:

Hi

Simple answer is: no.

More complete answer is: no

There is a lot more to stability than just the crystal cut. Having this or that cut is
in no way a guarantee that the result is “better” than some other cut. Indeed there
are more exotic cuts than the SC that improve on this or that. There are also mounting
/ fabrication techniques that improve on this or that, regardless of cut.

All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut
alternative. Various improvements here or there are likely to make it a bit better than
the other examples …. ( but not always )

Bob

On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts time-nuts@lists.febo.com wrote:

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer
ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

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Hi The stability depends on a long list of things. Since you can get higher Q with an AT than you can with an SC, if Q was all that mattered, the AT would be the king of the hill. The oscillator circuit matters, but different parts of it matter in different ways. The things you might do for low phase noise at a 100KHz offset might be a bad idea if very good ADEV at 100 seconds was the target. Tuning any high Q circuit very far off frequency probably is not a great idea. Keeping all of the “optimizations” on target over a wide pull range is not at all simple. If you are designing an OCXO from scratch, there is a lot to learn and hundreds of papers out there to get you started. If you are buying one, things are a bit more simple. You look at the spec sheet and decide if it’s going to do the job or not. Worst case, you buy a couple and test them. Bob > On Jun 8, 2022, at 10:01 AM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote: > > Hi,So, highest short term stability depends on the Q of the crystal and quality of the feedback circuit. In that case, an AT-cut with a low noise feedback amplifier will be as good as an SC-cut with the same amp. Does pulling the oscillator affect the short term walk?rp > > On Wednesday, June 8, 2022 at 10:44:24 AM PDT, Magnus Danielson via time-nuts <time-nuts@lists.febo.com> wrote: > > Hi, > > I agree in general. However, I do see that other work to get good > resulst have been done when SC-cut is considered, so rather than SC-cut > as a cut is better, it becomes somewhat of a tell-tale of that other > work being done properly. I.e. it is meaningless to take the step to > SC-cut when other defects dominate so the SC-cut properties only makes > things more expensive than the AT-cut. > > As far as I remember and know, you can achieve about the same > phase-noise properties as you hit about the same bandwidth from the Q, > and noise contribution is about the same. So, it boils down to do the > supporting amplifier well. > > Cheers, > Magnus > > On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote: >> Hi >> >> Simple answer is: no. >> >> More complete answer is: no >> >> There is a lot more to stability than just the crystal cut. Having this or that cut is >> in no way a guarantee that the result is “better” than some other cut. Indeed there >> are more exotic cuts than the SC that improve on this or that. There are also mounting >> / fabrication techniques that improve on this or that, regardless of cut. >> >> All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut >> alternative. Various improvements here or there are likely to make it a bit better than >> the other examples …. ( but not always ) >> >> Bob >> >>> On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts <time-nuts@lists.febo.com> wrote: >>> >>> Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. >>> Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer >>> ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. >>> Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp >>> >>> _______________________________________________ >>> 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 > _______________________________________________ > 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

BK

Bob kb8tq

Wed, Jun 8, 2022 9:20 PM

Hi

Well …..

You can bash both AT’s and SC’s a lot harder than you might think. Both
will suffer quite a bit in terms of ADEV when you do.

Since the AT likely has a lower resistance (by quite a bit) than the SC, the loop
current ( and thus the drive into the buffer) may not be as far different on the
two as you would guess.

Bob

On Jun 8, 2022, at 10:42 AM, Gerhard Hoffmann via time-nuts time-nuts@lists.febo.com wrote:

Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts:

As far as I remember and know, you can achieve about the same
phase-noise properties as you hit about the same bandwidth from the Q,
and noise contribution is about the same. So, it boils down to do the
supporting amplifier well.

But SC can tolerate more power, so you may get more distance to the
thermal noise floor.

cheers, Gerhard

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Hi Well ….. You can bash both AT’s and SC’s a *lot* harder than you might think. Both will suffer quite a bit in terms of ADEV when you do. Since the AT likely has a lower resistance (by quite a bit) than the SC, the loop current ( and thus the drive into the buffer) may not be as far different on the two as you would guess. Bob > On Jun 8, 2022, at 10:42 AM, Gerhard Hoffmann via time-nuts <time-nuts@lists.febo.com> wrote: > > Am 2022-06-08 13:27, schrieb Magnus Danielson via time-nuts: > >> As far as I remember and know, you can achieve about the same >> phase-noise properties as you hit about the same bandwidth from the Q, >> and noise contribution is about the same. So, it boils down to do the >> supporting amplifier well. > > But SC can tolerate more power, so you may get more distance to the > thermal noise floor. > > cheers, Gerhard > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

RP

Ross P

Wed, Jun 8, 2022 9:22 PM

Hi,Thank you very much, this paper answered some questions.

On Wednesday, June 8, 2022 at 12:38:04 PM PDT, Hans-Georg Lehnard via time-nuts <time-nuts@lists.febo.com> wrote:

Hi,

read this paper from Connor-Winfield about differences AT/SC cuts.

http://www.conwin.com/pdfs/at_or_sc_for_ocxo.pdf

Am 2022-06-08 04:04, schrieb Ross P via time-nuts:

Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point.
Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of

refer

ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz.
Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp

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Hi,Thank you very much, this paper answered some questions. On Wednesday, June 8, 2022 at 12:38:04 PM PDT, Hans-Georg Lehnard via time-nuts <time-nuts@lists.febo.com> wrote: Hi, read this paper from Connor-Winfield about differences AT/SC cuts. http://www.conwin.com/pdfs/at_or_sc_for_ocxo.pdf Am 2022-06-08 04:04, schrieb Ross P via time-nuts: > Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. > Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of refer > ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. > Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp > > _______________________________________________ > 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

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Is SC the most stable cut for lowest phase noise?