[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi, So, one of my hydrogen masers have a tiny leak. The outer vacuum does not pump down as it should, and it has consumed the ion pump. This have massive effect on the thermal balance and causes heat to leak out much faster from the outer heaters to surrounding wall. This prohibits its controllers of reaching the temperature but also prohibits next layer to achieve it and finally inside that the actual resonator temperature stabilization. That is in itself 5 temperature control-loops in 3 layers. There is also passive heat-shields in it. So, it is crazy efficient heat transfer. It is so efficient method, that it's the basis for pressure gauges, such as the Pirani gauge. Now, while it is annoying it does not work, I can say that it has significantly increased my knowledge about temperature stabilitzation of hydrogen masers and workings of vacuum systems. Not to say I am fully skilled, but at least not as ignorant as before, so there is a good start. I also learned how to write some Python to log the serial port, toss it into a InfluxDB and plots it with Graphana. So the effect is real, very real. We are looking into bringing a masspectrometer over, pump it down and then do helium leakage tests to see if we can locate the joint that is leaking. While there is many possible joints in the vacuum system, my testing have helped to narrow it down to three. Of those, in particular one could be suspect as it could potentially take more hit than the others upon transport. Yes, I need a turbopump setup and spare parts. Cheers, Magnus On 2022-06-13 03:30, Bob kb8tq via time-nuts wrote: Hi Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For bonus points, open up the crystal package. If you have the gear to test it, take a look at what the gas *is* inside the package. ( Good luck with that :) :) :) ) If you had the gear and the willingness to scrap out OCXO’s you would find that a number of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive (thermal wise) than a *perfect* vacuum …… Bob On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts wrote: I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts wrote: I have been of the impression for years now that most "better" crystals are in a vacuum. And the electrical and mechanical connections to the quartz itself place as little mechanical load on the crystal as possible. Thermal conductivity from the oven to the crystal itself would be both hard to model and hard to speed up. IR transmission of energy to the crystal also seems problematic considering the IR transmission of quartz and the IR reflectivity of gold contact plating. Is any of this an issue? - Louis On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < time-nuts@lists.febo.com> wrote: Hi On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts < time-nuts@lists.febo.com> wrote: On 6/10/22 1:57 PM, Dr. David Kirkby wrote: On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < time-nuts@lists.febo.com> wrote: On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. Is that not likely to damage a crystal? Different parts of the crystal and likely to be at significantly different temperatures at the same time, putting a lot of stress on the crystal due to a thermal gradient. It's probably a bit academic, as nobody is going to make an oven that heats up in fractions of a second, but if one did, I suspect it might not do the crystal a lot of good. This is only an educated guess - I don't have anything to back it up. Oh, it would be disastrous, although quartz is pretty strong, all the rest of the mounting components might not be. Indeed, breaking a quartz blank via thermal stress would be very hard to do. The “rest of the parts” actually are pretty durable as well. Most of it is metal and it is quite able to handle thermal issues. The big issue in a fast warm up AT turned out to be designing the heater and the mount to get the energy to the blank quickly….. If you use a small enough package and blank, the amount of power turns out to be surprisingly small. If you want to go bonkers, you mount the heaters *inside* the crystal package. This does indeed create some issues in various areas. Bob At the other extreme, would there be any advantage in actually heating the crystal very slowly, over
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi Like it or not, modern crystal packages are mad of metal ( as opposed to glass). The gotcha with metal is that getting rid of *all* of the He is darn hard. That makes a “perfect vacuum” more than a bit tough. Bob > On Jun 12, 2022, at 7:38 PM, Lux, Jim via time-nuts > wrote: > > On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote: >> Hi >> >> Tear into some of your SC cut based OCXO’s. Take a look at the crystal >> package. For >> bonus points, open up the crystal package. If you have the gear to test it, >> take a look >> at what the gas *is* inside the package. ( Good luck with that :) :) :) ) >> >> If you had the gear and the willingness to scrap out OCXO’s you would find >> that a number >> of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring >> this would >> be tough ( it’s that small). Go through the thermal modeling and it’s *way* >> more conductive >> (thermal wise) than a *perfect* vacuum …… >> >> Bob > > > And the worst thing is that if your vacuum sealed widget is in an atmosphere > with more He around (like waiting for a launch, in a place that does more He > leak tests, etc.), the He will diffuse into your package and it doesn't work > like expected. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote: Hi Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For bonus points, open up the crystal package. If you have the gear to test it, take a look at what the gas *is* inside the package. ( Good luck with that :) :) :) ) If you had the gear and the willingness to scrap out OCXO’s you would find that a number of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive (thermal wise) than a *perfect* vacuum …… Bob And the worst thing is that if your vacuum sealed widget is in an atmosphere with more He around (like waiting for a launch, in a place that does more He leak tests, etc.), the He will diffuse into your package and it doesn't work like expected. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi Tear into some of your SC cut based OCXO’s. Take a look at the crystal package. For bonus points, open up the crystal package. If you have the gear to test it, take a look at what the gas *is* inside the package. ( Good luck with that :) :) :) ) If you had the gear and the willingness to scrap out OCXO’s you would find that a number of fast warmup OCXO’s have a *tiny* amount of He in the package. Measuring this would be tough ( it’s that small). Go through the thermal modeling and it’s *way* more conductive (thermal wise) than a *perfect* vacuum …… Bob > On Jun 12, 2022, at 9:18 AM, Ross P via time-nuts > wrote: > > I have seen that manufacturers seal their crystals in a vacuum, maybe air > interaction affects Q. The point that vacuum inhibits heat flow is something > I have never considered in ovenized units. My ovenized crystals take about an > hour to settle. I have some WW2 surplus crystals in non-sealed packages that > I have not tested... something to do.rp > >On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts > wrote: > > I have been of the impression for years now that most "better" crystals are > in a vacuum. And the electrical and mechanical connections to the quartz > itself place as little mechanical load on the crystal as possible. > Thermal conductivity from the oven to the crystal itself would be both > hard to model and hard to speed up. > > IR transmission of energy to the crystal also seems problematic considering > the IR transmission of quartz and the IR reflectivity of gold > contact plating. > > Is any of this an issue? > > - Louis > > On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < > time-nuts@lists.febo.com> wrote: > >> Hi >> >>> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts < >> time-nuts@lists.febo.com> wrote: >>> >>> On 6/10/22 1:57 PM, Dr. David Kirkby wrote: On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < >> time-nuts@lists.febo.com> wrote: On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. Is that not likely to damage a crystal? Different parts of the crystal >> and likely to be at significantly different temperatures at the same time, >> putting a lot of stress on the crystal due to a thermal gradient. It's >> probably a bit academic, as nobody is going to make an oven that heats up >> in fractions of a second, but if one did, I suspect it might not do the >> crystal a lot of good. This is only an educated guess - I don't have >> anything to back it up. >>> Oh, it would be disastrous, although quartz is pretty strong, all the >> rest of the mounting components might not be. >> >> Indeed, breaking a quartz blank via thermal stress would be very hard to >> do. >> The “rest of the parts” actually are pretty durable as well. Most of it is >> metal and >> it is quite able to handle thermal issues. >> >> The big issue in a fast warm up AT turned out to be designing the heater >> and the >> mount to get the energy to the blank quickly….. If you use a small enough >> package >> and blank, the amount of power turns out to be surprisingly small. >> >> If you want to go bonkers, you mount the heaters *inside* the crystal >> package. This >> does indeed create some issues in various areas. >> >> Bob >> At the other extreme, would there be any advantage in actually heating >> the crystal very slowly, over the course of an hour/day/week, so the >> temperature gradient across the crystal is very small? Of course, if an >> oven took ages to reach the correct temperature, it would be inconvenient >> for most applications, but for some applications, the advantages might >> outweigh the disadvantages. Of course, if one does this, I suspect one >> would have to cool the crystal slowly too to prevent a significant thermal >> gradient across the crystal. I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. >> I was told that Nikon cools the front element over a period of 6 months to >> reduce stresses in the glass. >>> >>> Big glass mirrors for telescopes do the same. >>> >>> >>> Dave >>> >>> ___ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe send an email to time-nuts-le...@lists.febo.com >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
I have seen that manufacturers seal their crystals in a vacuum, maybe air interaction affects Q. The point that vacuum inhibits heat flow is something I have never considered in ovenized units. My ovenized crystals take about an hour to settle. I have some WW2 surplus crystals in non-sealed packages that I have not tested... something to do.rp On Sunday, June 12, 2022 at 07:26:19 AM PDT, Louis Taber via time-nuts wrote: I have been of the impression for years now that most "better" crystals are in a vacuum. And the electrical and mechanical connections to the quartz itself place as little mechanical load on the crystal as possible. Thermal conductivity from the oven to the crystal itself would be both hard to model and hard to speed up. IR transmission of energy to the crystal also seems problematic considering the IR transmission of quartz and the IR reflectivity of gold contact plating. Is any of this an issue? - Louis On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < time-nuts@lists.febo.com> wrote: > Hi > > > On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts < > time-nuts@lists.febo.com> wrote: > > > > On 6/10/22 1:57 PM, Dr. David Kirkby wrote: > >> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < > time-nuts@lists.febo.com> wrote: > >> > >> On the subject of rapid warm up. I suppose if you had a need, one > >> could > >> dump as much power as you need into the heater. Turn on oscillator, > >> lights in room dim for a few moments. > >> > >> > >> Is that not likely to damage a crystal? Different parts of the crystal > and likely to be at significantly different temperatures at the same time, > putting a lot of stress on the crystal due to a thermal gradient. It's > probably a bit academic, as nobody is going to make an oven that heats up > in fractions of a second, but if one did, I suspect it might not do the > crystal a lot of good. This is only an educated guess - I don't have > anything to back it up. > > Oh, it would be disastrous, although quartz is pretty strong, all the > rest of the mounting components might not be. > > Indeed, breaking a quartz blank via thermal stress would be very hard to > do. > The “rest of the parts” actually are pretty durable as well. Most of it is > metal and > it is quite able to handle thermal issues. > > The big issue in a fast warm up AT turned out to be designing the heater > and the > mount to get the energy to the blank quickly….. If you use a small enough > package > and blank, the amount of power turns out to be surprisingly small. > > If you want to go bonkers, you mount the heaters *inside* the crystal > package. This > does indeed create some issues in various areas. > > Bob > > >> > >> At the other extreme, would there be any advantage in actually heating > the crystal very slowly, over the course of an hour/day/week, so the > temperature gradient across the crystal is very small? Of course, if an > oven took ages to reach the correct temperature, it would be inconvenient > for most applications, but for some applications, the advantages might > outweigh the disadvantages. Of course, if one does this, I suspect one > would have to cool the crystal slowly too to prevent a significant thermal > gradient across the crystal. > >> > >> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. > I was told that Nikon cools the front element over a period of 6 months to > reduce stresses in the glass. > > > > Big glass mirrors for telescopes do the same. > > > > > > > >> > >> Dave > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi Well ….. The question becomes “how much of a vacuum? I surprisingly small amount of He will have a substantial impact on heat flow. Since there will always be some leakage / outgassing in any package design, it just *might* improve aging. The days of “spring wire” mounts are long gone for precision crystals. The mounts are short fat metal “bands” that will move heat pretty well. On the typical “TO” style package (HC-40 etc…) the thermal path isn’t all that bad. The location of the heaters *is* under the control of the OCXO designer. You can improve the thermal path (speed wise) by moving things around. Yes, this has other impacts that may or may not be an improvement in other areas. Bob > On Jun 12, 2022, at 5:34 AM, Louis Taber via time-nuts > wrote: > > I have been of the impression for years now that most "better" crystals are > in a vacuum. And the electrical and mechanical connections to the quartz > itself place as little mechanical load on the crystal as possible. > Thermal conductivity from the oven to the crystal itself would be both > hard to model and hard to speed up. > > IR transmission of energy to the crystal also seems problematic considering > the IR transmission of quartz and the IR reflectivity of gold > contact plating. > > Is any of this an issue? > > - Louis > > On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < > time-nuts@lists.febo.com> wrote: > >> Hi >> >>> On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts < >> time-nuts@lists.febo.com> wrote: >>> >>> On 6/10/22 1:57 PM, Dr. David Kirkby wrote: On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < >> time-nuts@lists.febo.com> wrote: On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. Is that not likely to damage a crystal? Different parts of the crystal >> and likely to be at significantly different temperatures at the same time, >> putting a lot of stress on the crystal due to a thermal gradient. It's >> probably a bit academic, as nobody is going to make an oven that heats up >> in fractions of a second, but if one did, I suspect it might not do the >> crystal a lot of good. This is only an educated guess - I don't have >> anything to back it up. >>> Oh, it would be disastrous, although quartz is pretty strong, all the >> rest of the mounting components might not be. >> >> Indeed, breaking a quartz blank via thermal stress would be very hard to >> do. >> The “rest of the parts” actually are pretty durable as well. Most of it is >> metal and >> it is quite able to handle thermal issues. >> >> The big issue in a fast warm up AT turned out to be designing the heater >> and the >> mount to get the energy to the blank quickly….. If you use a small enough >> package >> and blank, the amount of power turns out to be surprisingly small. >> >> If you want to go bonkers, you mount the heaters *inside* the crystal >> package. This >> does indeed create some issues in various areas. >> >> Bob >> At the other extreme, would there be any advantage in actually heating >> the crystal very slowly, over the course of an hour/day/week, so the >> temperature gradient across the crystal is very small? Of course, if an >> oven took ages to reach the correct temperature, it would be inconvenient >> for most applications, but for some applications, the advantages might >> outweigh the disadvantages. Of course, if one does this, I suspect one >> would have to cool the crystal slowly too to prevent a significant thermal >> gradient across the crystal. I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. >> I was told that Nikon cools the front element over a period of 6 months to >> reduce stresses in the glass. >>> >>> Big glass mirrors for telescopes do the same. >>> >>> >>> Dave >>> >>> ___ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe send an email to time-nuts-le...@lists.febo.com >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
I have been of the impression for years now that most "better" crystals are in a vacuum. And the electrical and mechanical connections to the quartz itself place as little mechanical load on the crystal as possible. Thermal conductivity from the oven to the crystal itself would be both hard to model and hard to speed up. IR transmission of energy to the crystal also seems problematic considering the IR transmission of quartz and the IR reflectivity of gold contact plating. Is any of this an issue? - Louis On Fri, Jun 10, 2022 at 9:53 PM Bob kb8tq via time-nuts < time-nuts@lists.febo.com> wrote: > Hi > > > On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts < > time-nuts@lists.febo.com> wrote: > > > > On 6/10/22 1:57 PM, Dr. David Kirkby wrote: > >> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < > time-nuts@lists.febo.com> wrote: > >> > >>On the subject of rapid warm up. I suppose if you had a need, one > >>could > >>dump as much power as you need into the heater. Turn on oscillator, > >>lights in room dim for a few moments. > >> > >> > >> Is that not likely to damage a crystal? Different parts of the crystal > and likely to be at significantly different temperatures at the same time, > putting a lot of stress on the crystal due to a thermal gradient. It's > probably a bit academic, as nobody is going to make an oven that heats up > in fractions of a second, but if one did, I suspect it might not do the > crystal a lot of good. This is only an educated guess - I don't have > anything to back it up. > > Oh, it would be disastrous, although quartz is pretty strong, all the > rest of the mounting components might not be. > > Indeed, breaking a quartz blank via thermal stress would be very hard to > do. > The “rest of the parts” actually are pretty durable as well. Most of it is > metal and > it is quite able to handle thermal issues. > > The big issue in a fast warm up AT turned out to be designing the heater > and the > mount to get the energy to the blank quickly….. If you use a small enough > package > and blank, the amount of power turns out to be surprisingly small. > > If you want to go bonkers, you mount the heaters *inside* the crystal > package. This > does indeed create some issues in various areas. > > Bob > > >> > >> At the other extreme, would there be any advantage in actually heating > the crystal very slowly, over the course of an hour/day/week, so the > temperature gradient across the crystal is very small? Of course, if an > oven took ages to reach the correct temperature, it would be inconvenient > for most applications, but for some applications, the advantages might > outweigh the disadvantages. Of course, if one does this, I suspect one > would have to cool the crystal slowly too to prevent a significant thermal > gradient across the crystal. > >> > >> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. > I was told that Nikon cools the front element over a period of 6 months to > reduce stresses in the glass. > > > > Big glass mirrors for telescopes do the same. > > > > > > > >> > >> Dave > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi > On Jun 10, 2022, at 2:38 PM, Lux, Jim via time-nuts > wrote: > > On 6/10/22 1:57 PM, Dr. David Kirkby wrote: >> On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts >> wrote: >> >>On the subject of rapid warm up. I suppose if you had a need, one >>could >>dump as much power as you need into the heater. Turn on oscillator, >>lights in room dim for a few moments. >> >> >> Is that not likely to damage a crystal? Different parts of the crystal and >> likely to be at significantly different temperatures at the same time, >> putting a lot of stress on the crystal due to a thermal gradient. It's >> probably a bit academic, as nobody is going to make an oven that heats up in >> fractions of a second, but if one did, I suspect it might not do the crystal >> a lot of good. This is only an educated guess - I don't have anything to >> back it up. > Oh, it would be disastrous, although quartz is pretty strong, all the rest of > the mounting components might not be. Indeed, breaking a quartz blank via thermal stress would be very hard to do. The “rest of the parts” actually are pretty durable as well. Most of it is metal and it is quite able to handle thermal issues. The big issue in a fast warm up AT turned out to be designing the heater and the mount to get the energy to the blank quickly….. If you use a small enough package and blank, the amount of power turns out to be surprisingly small. If you want to go bonkers, you mount the heaters *inside* the crystal package. This does indeed create some issues in various areas. Bob >> >> At the other extreme, would there be any advantage in actually heating the >> crystal very slowly, over the course of an hour/day/week, so the temperature >> gradient across the crystal is very small? Of course, if an oven took ages >> to reach the correct temperature, it would be inconvenient for most >> applications, but for some applications, the advantages might outweigh the >> disadvantages. Of course, if one does this, I suspect one would have to cool >> the crystal slowly too to prevent a significant thermal gradient across the >> crystal. >> >> I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I was >> told that Nikon cools the front element over a period of 6 months to reduce >> stresses in the glass. > > Big glass mirrors for telescopes do the same. > > > >> >> Dave > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Its far more likely that the glass blank from which the front element is machined is annealed over six months rather than the element itself as precision optical element fabrication doesn't add strain to the element. Some low dispersion glasses have relatively high TCE and are very sensitive to thermal shock. Elements made from such glasses are rarely used as front elements particularly in larger sizes to avoid element fracture due to thermal shock. Bruce > On 11/06/2022 10:38 Lux, Jim via time-nuts wrote: > > > On 6/10/22 1:57 PM, Dr. David Kirkby wrote: > > On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts > > wrote: > > > > On the subject of rapid warm up. I suppose if you had a need, one > > could > > dump as much power as you need into the heater. Turn on oscillator, > > lights in room dim for a few moments. > > > > > > Is that not likely to damage a crystal? Different parts of the crystal > > and likely to be at significantly different temperatures at the same > > time, putting a lot of stress on the crystal due to a thermal > > gradient. It's probably a bit academic, as nobody is going to make an > > oven that heats up in fractions of a second, but if one did, I suspect > > it might not do the crystal a lot of good. This is only an educated > > guess - I don't have anything to back it up. > Oh, it would be disastrous, although quartz is pretty strong, all the > rest of the mounting components might not be. > > > > At the other extreme, would there be any advantage in actually > > heating the crystal very slowly, over the course of an hour/day/week, > > so the temperature gradient across the crystal is very small? Of > > course, if an oven took ages to reach the correct temperature, it > > would be inconvenient for most applications, but for some > > applications, the advantages might outweigh the disadvantages. Of > > course, if one does this, I suspect one would have to cool the crystal > > slowly too to prevent a significant thermal gradient across the crystal. > > > > I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. > > I was told that Nikon cools the front element over a period of 6 > > months to reduce stresses in the glass. > > Big glass mirrors for telescopes do the same. > > > > > > > Dave > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
On 6/10/22 1:57 PM, Dr. David Kirkby wrote: On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts wrote: On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. Is that not likely to damage a crystal? Different parts of the crystal and likely to be at significantly different temperatures at the same time, putting a lot of stress on the crystal due to a thermal gradient. It's probably a bit academic, as nobody is going to make an oven that heats up in fractions of a second, but if one did, I suspect it might not do the crystal a lot of good. This is only an educated guess - I don't have anything to back it up. Oh, it would be disastrous, although quartz is pretty strong, all the rest of the mounting components might not be. At the other extreme, would there be any advantage in actually heating the crystal very slowly, over the course of an hour/day/week, so the temperature gradient across the crystal is very small? Of course, if an oven took ages to reach the correct temperature, it would be inconvenient for most applications, but for some applications, the advantages might outweigh the disadvantages. Of course, if one does this, I suspect one would have to cool the crystal slowly too to prevent a significant thermal gradient across the crystal. I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I was told that Nikon cools the front element over a period of 6 months to reduce stresses in the glass. Big glass mirrors for telescopes do the same. Dave ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
On 6/10/22 12:13 PM, Richard (Rick) Karlquist wrote: I think there is a severe misunderstanding of this issue. First of all, "rapid warmup" is a red herring. The real issue is "rapid frequency stabilization". Indeed. But to a certain extent, that's why oscillators don't have 5 second warm up times - it wouldn't help. So the "few minutes" is a good compromise between design simplicity and waiting for the internals to equilibrate. I suspect that those fancy USOs in vacuum bottles take a long, long time to come to equilibrium. And that is one of the claims to fame of the CSAC - from power on to "on frequency" is quite short. The time it takes for the oven to cut back (typically only a minute or two) is a very minor part of the time budget to get to frequency stabilization. You could have an AT cut oscillator that reached "oven warmup" in 1 second, but then you would have something like a 1 hour wait to get frequency stability, due to the thermal stresses. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi, It is in this context one should look at the CSAC, as the low power consumption can enable it to be powered on much earlier. It's not that it's performance is stellar, but when you consider power consumption and what that can enable, it becomes impressive and another approach to solve things. Cheers, Magnus On 2022-06-11 00:00, Bob kb8tq via time-nuts wrote: Hi Well …. folks have made AT based OCXO’s that heat up in “seconds” ( as in under a minute ). Back in the 1980’s they stabilized to < 1x10^-7 at least as fast as the then typical SC based OCXO’s did …. ( < 6 minutes ). Collins bought quite a few of them over the years. Bob On Jun 10, 2022, at 1:25 PM, Dr. David Kirkby via time-nuts wrote: On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < time-nuts@lists.febo.com> wrote: On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. Is that not likely to damage a crystal? Different parts of the crystal and likely to be at significantly different temperatures at the same time, putting a lot of stress on the crystal due to a thermal gradient. It's probably a bit academic, as nobody is going to make an oven that heats up in fractions of a second, but if one did, I suspect it might not do the crystal a lot of good. This is only an educated guess - I don't have anything to back it up. At the other extreme, would there be any advantage in actually heating the crystal very slowly, over the course of an hour/day/week, so the temperature gradient across the crystal is very small? Of course, if an oven took ages to reach the correct temperature, it would be inconvenient for most applications, but for some applications, the advantages might outweigh the disadvantages. Of course, if one does this, I suspect one would have to cool the crystal slowly too to prevent a significant thermal gradient across the crystal. I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I was told that Nikon cools the front element over a period of 6 months to reduce stresses in the glass. Dave ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi Well …. folks have made AT based OCXO’s that heat up in “seconds” ( as in under a minute ). Back in the 1980’s they stabilized to < 1x10^-7 at least as fast as the then typical SC based OCXO’s did …. ( < 6 minutes ). Collins bought quite a few of them over the years. Bob > On Jun 10, 2022, at 1:25 PM, Dr. David Kirkby via time-nuts > wrote: > > On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < > time-nuts@lists.febo.com> wrote: > >> >> On the subject of rapid warm up. I suppose if you had a need, one could >> dump as much power as you need into the heater. Turn on oscillator, >> lights in room dim for a few moments. >> > > Is that not likely to damage a crystal? Different parts of the crystal and > likely to be at significantly different temperatures at the same time, > putting a lot of stress on the crystal due to a thermal gradient. It's > probably a bit academic, as nobody is going to make an oven that heats up > in fractions of a second, but if one did, I suspect it might not do the > crystal a lot of good. This is only an educated guess - I don't have > anything to back it up. > > At the other extreme, would there be any advantage in actually heating the > crystal very slowly, over the course of an hour/day/week, so the > temperature gradient across the crystal is very small? Of course, if an > oven took ages to reach the correct temperature, it would be inconvenient > for most applications, but for some applications, the advantages might > outweigh the disadvantages. Of course, if one does this, I suspect one > would have to cool the crystal slowly too to prevent a significant thermal > gradient across the crystal. > > I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I > was told that Nikon cools the front element over a period of 6 months to > reduce stresses in the glass. > > Dave > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts < time-nuts@lists.febo.com> wrote: > > On the subject of rapid warm up. I suppose if you had a need, one could > dump as much power as you need into the heater. Turn on oscillator, > lights in room dim for a few moments. > Is that not likely to damage a crystal? Different parts of the crystal and likely to be at significantly different temperatures at the same time, putting a lot of stress on the crystal due to a thermal gradient. It's probably a bit academic, as nobody is going to make an oven that heats up in fractions of a second, but if one did, I suspect it might not do the crystal a lot of good. This is only an educated guess - I don't have anything to back it up. At the other extreme, would there be any advantage in actually heating the crystal very slowly, over the course of an hour/day/week, so the temperature gradient across the crystal is very small? Of course, if an oven took ages to reach the correct temperature, it would be inconvenient for most applications, but for some applications, the advantages might outweigh the disadvantages. Of course, if one does this, I suspect one would have to cool the crystal slowly too to prevent a significant thermal gradient across the crystal. I know it's a bit different, but I have a 600 mm f4 Nikon camera lens. I was told that Nikon cools the front element over a period of 6 months to reduce stresses in the glass. Dave ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
I think there is a severe misunderstanding of this issue. First of all, "rapid warmup" is a red herring. The real issue is "rapid frequency stabilization". The time it takes for the oven to cut back (typically only a minute or two) is a very minor part of the time budget to get to frequency stabilization. You could have an AT cut oscillator that reached "oven warmup" in 1 second, but then you would have something like a 1 hour wait to get frequency stability, due to the thermal stresses. Part of the reason for the misunderstanding is that the problem I have described is basically orthogonal to the proverbial time nut with his master OCXO in an underground bunker running on an uninterruptible power supply, that has been powered up continuously for umpteen years. Rick N6RK On 6/10/2022 6:47 AM, Lux, Jim via time-nuts wrote: On 6/9/22 8:53 PM, Bob kb8tq via time-nuts wrote: Hi There happen to be *some* AT cut based OCXO’s that beat the typical SC cut on warmup … just saying …. :) Bob On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. But everything is a tradeoff, and I suspect that over time "standard designs" sort of migrate to particular ratios of things like peak vs average heater current, etc. Especially in applications driven by design rules for things like "maximum current per connector pin" or "component derating" - I suspect that drives things more than the fundamental physics, in most cases. Why are diodes rated at 1 or 3 Amps? And not 2? ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
On 6/9/22 8:53 PM, Bob kb8tq via time-nuts wrote: Hi There happen to be *some* AT cut based OCXO’s that beat the typical SC cut on warmup … just saying …. :) Bob On the subject of rapid warm up. I suppose if you had a need, one could dump as much power as you need into the heater. Turn on oscillator, lights in room dim for a few moments. But everything is a tradeoff, and I suspect that over time "standard designs" sort of migrate to particular ratios of things like peak vs average heater current, etc. Especially in applications driven by design rules for things like "maximum current per connector pin" or "component derating" - I suspect that drives things more than the fundamental physics, in most cases. Why are diodes rated at 1 or 3 Amps? And not 2? ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi There happen to be *some* AT cut based OCXO’s that beat the typical SC cut on warmup … just saying …. :) Bob > On Jun 9, 2022, at 9:03 AM, Bruce Hunter via time-nuts > wrote: > > My only experience with SC-cut crystals is that time base oscillators in > later EIP/Phase-Matrix counters with SC-cut crystal oscillators seem to > warm-up from a cold start and stabilize more quickly than earlier AT-cut > versions. I was surprised to see from Jeff Cartwright's paper that SC-cut > crystals operate at higher temperatures. Could this rapid warm up > characteristic be attributable to oven design rather than crystal cut? > Bruce > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
On 6/9/2022 10:03 AM, Bruce Hunter via time-nuts wrote: My only experience with SC-cut crystals is that time base oscillators in later EIP/Phase-Matrix counters with SC-cut crystal oscillators seem to warm-up from a cold start and stabilize more quickly than earlier AT-cut versions. I was surprised to see from Jeff Cartwright's paper that SC-cut crystals operate at higher temperatures. Could this rapid warm up characteristic be attributable to oven design rather than crystal cut? Bruce Absolutely not. It is strictly due to thermal stress compensation. Rick N6RK ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Yet another interesting time nuts conversation. A few comments: 1 A number of comments stated as a "fact" that higher unloaded Q for the resonator corresponds to lower phase noise. This idea evidentially comes from looking at analysis of a so-called free running oscillator with a simple LC tank or microwave resonator, as published by Edson, Kurakawa, and Cutler/Leeson. However, even in this case, what matters is the LOADED Q, and the drive level to the sustaining amplifier. A given drive level will have a particular phase noise and flicker noise floor associated with it. Incidentally, the resonator should be critically coupled, in which case Ql = 1/2 Qu, for optimum phase noise., 2. With a piezo electric resonator, the intrinsic flicker noise of the resonator dominates, and it isn't related to Q (unloaded to loaded). The sustaining amplifier ordinarily is not a factor. 3. I personally measured the intrinsic phase noise of a free-standing 10811 crystal and compared it to the phase noise of a 10811 oscillator with that same crystal installed. The conclusion was that the oscillator phase noise was basically the same as the intrinsic crystal noise, except at large frequency offsets. 4. The only possible scenario I can see for why an SC cut might have better phase noise is if you don't have a very good oven. Then ADEV at long averaging times starts to go up. In that case, an SC cut might help because of improving tempco. 5. Phase noise at large offsets (>1kHz) depends on the buffer amplifier design. The grounded base design in the 10811 is the optimum first stage. Unfortunately, the 2nd and 3rd stages in the 10811 degrade its phase noise. This has little or nothing to do with the cut of the crystal or anything else about it. (The idea for this was published by U. Rhode and later patented by Burgoon of HP). 6. The primary motivation for the SC cut at the HP Santa Clara division (where I worked) was to be able to put it into a frequency counter used for field maintenance. The idea was that the technician could carry it from his truck into the worksite and plug it, starting from a cold oven. Then, in only 15 minutes, the counter met some accuracy spec. With a 10544, it would take many times longer to get to the same accuracy. Jack Kusters used to say that "SC" actually stood for "Santa Clara" :-) Rick N6RK ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi, The ability to stabilize at that temperature is indeed an issue. While the resonators Q shift, the loaded Q I would not expect to shift as much. Futher, the noise of the supporting amplifier also needs to be reduced. Naturally, the design could be adjusted to the different condition. I've seen people taking "the best" oscillator (SC-cut) and go cryogenic, and then have severe temperature issues, because they did not understand that the benefit of the cut really manifest itself at some specific temperature. Luckily that they was able to get that feedback as the benefit of presenting to their peers at a conference. Cryogenic provides an oppertunity, but as with any such condition, it takes a number of considerations to be able to harvest the benefits. Cheers, Magnus On 2022-06-09 02:12, Bob kb8tq via time-nuts wrote: Hi Lower turning point has been done, both with AT’s (back in ~ the 1950’s) and with SC’s. Neither one showed any significant benefit. Taking a crystal down to sub 20K sort of temps does ramp up the Q. The gotcha is that the frequency vs temp curve is so steep that very minor temperature variations utterly trash the stability of the device. Bob On Jun 8, 2022, at 1:49 PM, Gerhard Hoffmann via time-nuts wrote: Am 2022-06-08 21:53, schrieb Tom Van Baak: Would it be advantageous, then, to run a high-performance laboratory oscillator at its lower turnover point? Or at -78 C (CO2) or 77 K (liquid Nitrogen)? I have no idea about the crystal itself. Maybe Bernd or the SC (SantaClara) veterans can help? When I measured the Q of the recovered SC crystal from that Morion MV89A, there was not much of a difference in the wanted resonance between room temperature and +89°C. I think I have published the data here a year ago. My deep freezer in the basement can do -36°C, but the VNA is so heavy... Infineon boasted that their SIGET transistors work nicely at a few Kelvin, so it would probably not fail for semiconductor availability (BFP640 & friends). OTOH, Ulrich Rohde wrote that the noise figure of the sustaining amplifier would take a hit under large signal conditions, but I don't know hard numbers. That would not disappear. But then, in a Driscoll for example, you can give the 2 transistors enough current so they run class A and do the little bit of limiting on the output side with Schottkys. For the amplifier, that is not large signal. That might be different for an amplifier in Lee-Hajimiri style. This is Dirac pulse excitation at the peak of the cycle to avoid phase modulation, that is optimized for mixing up 1/f noise. :-) Anyway, with a noise figure of the sustaining amplifier of a dB or even a few, there is no game changer to be expected from cooling. Whispering gallery saphire, anyone? I was at the precious stones museum in Idar-Oberstein here in the 'hood and saw all these huge saphires. I left with the head full of ideas... Cheers, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi Lower turning point has been done, both with AT’s (back in ~ the 1950’s) and with SC’s. Neither one showed any significant benefit. Taking a crystal down to sub 20K sort of temps does ramp up the Q. The gotcha is that the frequency vs temp curve is so steep that very minor temperature variations utterly trash the stability of the device. Bob > On Jun 8, 2022, at 1:49 PM, Gerhard Hoffmann via time-nuts > wrote: > > Am 2022-06-08 21:53, schrieb Tom Van Baak: >> Would it be advantageous, then, to run a high-performance laboratory >> oscillator at its lower turnover point? Or at -78 C (CO2) or 77 K >> (liquid Nitrogen)? > > I have no idea about the crystal itself. Maybe Bernd or the SC (SantaClara) > veterans can help? > > When I measured the Q of the recovered SC crystal from that Morion MV89A, > there was not much of a difference in the wanted resonance between room > temperature and +89°C. I think I have published the data here a year ago. > My deep freezer in the basement can do -36°C, but the VNA is so heavy... > > Infineon boasted that their SIGET transistors work nicely at a few Kelvin, > so it would probably not fail for semiconductor availability (BFP640 & > friends). > OTOH, Ulrich Rohde wrote that the noise figure of the sustaining amplifier > would > take a hit under large signal conditions, but I don't know hard numbers. > That would not disappear. > > But then, in a Driscoll for example, you can give the 2 transistors enough > current so they run class A and do the little bit of limiting on the output > side > with Schottkys. For the amplifier, that is not large signal. > > That might be different for an amplifier in Lee-Hajimiri style. > This is Dirac pulse excitation at the peak of the cycle to avoid phase > modulation, > that is optimized for mixing up 1/f noise. :-) > > Anyway, with a noise figure of the sustaining amplifier of a dB or even a few, > there is no game changer to be expected from cooling. > > Whispering gallery saphire, anyone? I was at the precious stones museum > in Idar-Oberstein here in the 'hood and saw all these huge saphires. > I left with the head full of ideas... > > Cheers, Gerhard > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Am 2022-06-08 21:53, schrieb Tom Van Baak: Would it be advantageous, then, to run a high-performance laboratory oscillator at its lower turnover point? Or at -78 C (CO2) or 77 K (liquid Nitrogen)? I have no idea about the crystal itself. Maybe Bernd or the SC (SantaClara) veterans can help? When I measured the Q of the recovered SC crystal from that Morion MV89A, there was not much of a difference in the wanted resonance between room temperature and +89°C. I think I have published the data here a year ago. My deep freezer in the basement can do -36°C, but the VNA is so heavy... Infineon boasted that their SIGET transistors work nicely at a few Kelvin, so it would probably not fail for semiconductor availability (BFP640 & friends). OTOH, Ulrich Rohde wrote that the noise figure of the sustaining amplifier would take a hit under large signal conditions, but I don't know hard numbers. That would not disappear. But then, in a Driscoll for example, you can give the 2 transistors enough current so they run class A and do the little bit of limiting on the output side with Schottkys. For the amplifier, that is not large signal. That might be different for an amplifier in Lee-Hajimiri style. This is Dirac pulse excitation at the peak of the cycle to avoid phase modulation, that is optimized for mixing up 1/f noise. :-) Anyway, with a noise figure of the sustaining amplifier of a dB or even a few, there is no game changer to be expected from cooling. Whispering gallery saphire, anyone? I was at the precious stones museum in Idar-Oberstein here in the 'hood and saw all these huge saphires. I left with the head full of ideas... Cheers, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi I would be careful with that paper since part of what it says is not (in general) correct. Bob > On Jun 8, 2022, at 1:22 PM, Ross P via time-nuts > wrote: > > 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 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-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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 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-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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 > 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-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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 > 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 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 >>> 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-le...@lists.febo.com >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list --
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
Hi Gerhard, On 2022-06-08 20:42, g...@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 ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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 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 >> 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-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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 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-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Is SC the most stable cut for lowest phase noise?
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 > 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-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
