[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: Home Brew GSPDO
On Wed, June 8, 2022 12:59 pm, paul swed via time-nuts wrote: > Well the easiest thing is to use two level comparators on the filtered DC. > One for high and the other for the low trip point. That only tells you if the PLL is locked to the PPS output, it does not tell you if the PPS output is valid. > On Wed, Jun 8, 2022 at 1:44 PM W Private via time-nuts < >> Is there an easy way to put an indicator on this thing so I know when it >> is locked, rather than using a computer or hooking up my scope? You will need to check the output messages from the GPS receiver to see if the GPS is receiving enough satellite. That is 9600 baud serial text, so a microcontroller can do it. Paul's recommendation for checking whether the PLL is locked is really only useful after you know that the signal you are tracking is actually valid. -- Chris Caudle ___ 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-nut
[time-nuts] Re: Home Brew GSPDO
That particular approach about monitoring the control voltage may have to wait until I get the thing all buttoned up and insulated because the control voltage changes even with the temp in the room. The oven is insulated, but apparently not perfectly. I did put the heatsink for voltage control in contact with the oven osc and did notice a big change in control voltage. Maybe 1/2 volt. It might drop another half volt. Trying to conserve the heat and use less power and hopefully get more stability, even though I cannot measure it . I figure that a little insulation is free anyway. Thanks, Wally On Wednesday, June 8, 2022, 2:04:08 PM EDT, paul swed via time-nuts wrote: Congratulations on the fun project. Well the easiest thing is to use two level comparators on the filtered DC. One for high and the other for the low trip point. Then feed a LED or a set reset flip flop so you have a memory. Unlocks are a challenge in that everything may work just fine but then a slip occurs. It relocks and you never know it. Just keeping inline with the approach you have used so far. You can absolutely create more advanced solutions. Just dislike a detector more complicated than the system. Good luck Paul WB8TSL On Wed, Jun 8, 2022 at 1:44 PM W Private via time-nuts < time-nuts@lists.febo.com> wrote: > Hello all, Thanks for letting me join. I just built a GPSDO from some junk > I had lying aroundI used a Navman GPS Jupiter 12 and an Isotemp 118-12 > which can be controlled by the NavmanThe Isotemp is controlled by the > heater in it which can be controlled by external DC signal. > The Navman puts out a 10 KHz square wave and I compared this to the > divided 10 MHz OXCO output thru a XOR. The XOR output is rectified to DC > and used to control the Isotemp. > I divided the 10 MHz with three 74LS90 DIPsI think this is pretty old > stuff.I believe the thing works, my 10 KHz square waves line up nicely at a > stable distance after a while and the output seems stable. It seems stable > at 500 MHz harmonic. I cannot see even a one Hz change at 500 MHz on any of > my equipment, such as it is. > Is there an easy way to put an indicator on this thing so I know when it > is locked, rather than using a computer or hooking up my scope?Any > suggestions on how to get more information from the GPS unit without using > a computer? Like designing a readout for time or whatever?Just looking for > ideas before I button the thing up in it's new case. > Wally KC9INK > ___ > 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 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: Home Brew GSPDO
Congratulations on the fun project. Well the easiest thing is to use two level comparators on the filtered DC. One for high and the other for the low trip point. Then feed a LED or a set reset flip flop so you have a memory. Unlocks are a challenge in that everything may work just fine but then a slip occurs. It relocks and you never know it. Just keeping inline with the approach you have used so far. You can absolutely create more advanced solutions. Just dislike a detector more complicated than the system. Good luck Paul WB8TSL On Wed, Jun 8, 2022 at 1:44 PM W Private via time-nuts < time-nuts@lists.febo.com> wrote: > Hello all, Thanks for letting me join. I just built a GPSDO from some junk > I had lying aroundI used a Navman GPS Jupiter 12 and an Isotemp 118-12 > which can be controlled by the NavmanThe Isotemp is controlled by the > heater in it which can be controlled by external DC signal. > The Navman puts out a 10 KHz square wave and I compared this to the > divided 10 MHz OXCO output thru a XOR. The XOR output is rectified to DC > and used to control the Isotemp. > I divided the 10 MHz with three 74LS90 DIPsI think this is pretty old > stuff.I believe the thing works, my 10 KHz square waves line up nicely at a > stable distance after a while and the output seems stable. It seems stable > at 500 MHz harmonic. I cannot see even a one Hz change at 500 MHz on any of > my equipment, such as it is. > Is there an easy way to put an indicator on this thing so I know when it > is locked, rather than using a computer or hooking up my scope?Any > suggestions on how to get more information from the GPS unit without using > a computer? Like designing a readout for time or whatever?Just looking for > ideas before I button the thing up in it's new case. > Wally KC9INK > ___ > 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] Home Brew GSPDO
Hello all, Thanks for letting me join. I just built a GPSDO from some junk I had lying aroundI used a Navman GPS Jupiter 12 and an Isotemp 118-12 which can be controlled by the NavmanThe Isotemp is controlled by the heater in it which can be controlled by external DC signal. The Navman puts out a 10 KHz square wave and I compared this to the divided 10 MHz OXCO output thru a XOR. The XOR output is rectified to DC and used to control the Isotemp. I divided the 10 MHz with three 74LS90 DIPsI think this is pretty old stuff.I believe the thing works, my 10 KHz square waves line up nicely at a stable distance after a while and the output seems stable. It seems stable at 500 MHz harmonic. I cannot see even a one Hz change at 500 MHz on any of my equipment, such as it is. Is there an easy way to put an indicator on this thing so I know when it is locked, rather than using a computer or hooking up my scope?Any suggestions on how to get more information from the GPS unit without using a computer? Like designing a readout for time or whatever?Just looking for ideas before I button the thing up in it's new case. Wally KC9INK ___ 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
