Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Always locate your DUTs physically orthogonal to each other. Unless you have 3 clocks. (and everybody knows what happens if you only have 2) From an old time-nuts message (Mar, 2009) Allied to this discussion is the Loomis effect, discovered by the American millionaire who had three Shortt clocks running in his basement. They synchronised unless aligned at 120 degrees to each other. I wonder weather they were shaking the bedrock, or maybe the gravitational attraction between the 10 kg pendulums may have synchronised them. (See Tuxedo Park by Jennet Conant) He qualified as the first time nut. It's on page 67-68. Google for Tuxedo-Park Shortt gets a hit in books.google.com at page 65 which is the start of the coverage of Shortt clocks. That was long before eBay. :) -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
John, On 05/30/2014 10:31 PM, John Miles wrote: I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Well, it will reflect the true stability if they're not exposed to the same drift stimuli, right? Neglecting shared long-term aging trends, they should both end up in random-walk territory over the long run. Otherwise, if you run the two oscillators in open air in the same room or even the same building, then they will respond similarly to HVAC cycles, diurnal cycles, and whatever other environmental changes are common to both. That will make their ADEV look better than reality when you measure them against each other. Indeed. Another way to view it is that you can that way consider it as a cancellation of those factors so you know how the noise performance behaves, which is what ADEV is all about. That may not be the best choice for other measures. It doesn't mean the long-term ADEV is necessarily invalid as a statistic, just that you probably haven't eliminated all of the common-mode influences. To the extent the two oscillators drift independently, the ADEV measurement is valid. For that matter, the isolation amps in your DMTD are also exposed to the same environment. Their residual phase tempco should be much better than any quartz oscillator, but if they're worse for some reason, they may dominate the long-term measurement. And of course, if you don't have enough isolation, you could be injection-locking the OCXOs in a really low bandwidth (days, perhaps). Shared power supply leads can also induce entrainment -- or even separate power supplies, if you run the leads right next to each other. Some of the Wenzel ULNs seem to be susceptible to this if you don't add bypassing at their power terminals. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. True, because they aren't as sensitive to environmental effects. But if you benchmark two nearby 5065As or masers carefully enough, their long-term ADEV will also look better than it really is, and for the same reasons. (Some people have even reported similar behavior with cesium standards, although I don't see how that could happen. There aren't supposed to be any first-order temperature effects in a CBT, and I'd think that any lower-order effects would be way beneath the tube's flicker floor...) Cesiums and rubidiums is indirectly sensitive as it takes time for the loop to track in changes in the OCXOs frequency. This process isn't phase accurate, so it could creep in phase as a result of environmental changes. Depending on the clock, different amount of work have been made to handle this. However, the differences in ADEV here is due to environmental effects, and they should not be measured in the ADEV context at all. ADEV is about to measure the random noise forms. Systematic effects such as environmental sensitivity is noise to that measurement. There are other measurements better aimed at such deviations. So, when you have cancellation of long term systematic effects you are in fact measuring a trued ADEV. Systematic effects affecting the phase (or frequency) should be separated and presented separately to the ADEV. They should then be canceled out of the measurement data that you make an ADEV plot on. In the end of the day, there is an overbelief of what works well in an ADEV plot. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
On 05/31/2014 12:24 AM, Poul-Henning Kamp wrote: In message 013401cf7c46$31ac3cc0$9504b640$@miles.io, John Miles writes: (Some people have even reported similar behavior with cesium standards, although I don't see how that could happen. There aren't supposed to be any first-order temperature effects in a CBT, and I'd think that any lower-order effects would be way beneath the tube's flicker floor...) One important trick in this area: Always locate your DUTs physically orthogonal to each other. Almost none of our DUTs have 3 axis of symmetry, and therefore most environmental effects are not symmetric with respect to orientation. I noticed this by accident comparing three identical OCXO's because I had put one of them in a different orientation than the other two: The environmental noise were much larger between that one and the two other, than between the two co-aligned DUTs. I'm not entirely sure this is relevant for Rb/Cs/H, their environmentals should be attenuated enough for it to not matter. Their physical packages do have a sensitivity to magnetic fields. The mymetal shield should handle most of it. Preferably you should let it stay in the same orientation not to see any shift. Hydrogen masers have a sensitivity to barometric pressure and temperature, as it will deform and thus detune the resonant cavity. This shifts with design, so some is sensitive and others is less sensitive. Rubidium and Cesiums is passive clocks, in that you need to insert a frequency generated from a fly-wheel crystal oscillator. Hydrogen masers exist in both passive and active form. In the active maser it actually outputs a signal. I believe that many of the active masers still use a crystal oscillator for the mix-down and locking. Regardless, while *most* of the environmental effects of that crystal oscillator is being canceled by the loop to the atomic reference, for all passive masers it's traditionally a frequency comparison and phase stability depends on how accurate phase deviation is being captured. Most time it is a bit crude detection which works better for frequency than phase. Cesium was selected because it had the second best insensitivity to magnetic fields, but was believed to be easier to work with and thus easier to reproduce. If the choice would have been different we would all be comparing our Thallium-beams and then some of us would be poor enough only to have cesium beams. The basis of selection has shifted, because since we have invented C-field servo to reduce the C-field effect. The means of detection now include lasers, which allows good efficiency. We can also do selective laser pumping which means we don't have to dump half the beam, increasing the signal to noise right there. We can do laser cooling and significantly remove a whole bunch of shifts due to temperature, doppler etc. We can then bounce a ball of atoms up and down a tube, removing the two-cavity systematic shift as well as making the observation time much longer. By cooling down the tube we can then remove the black body temperature shift of frequency. Yeah, there is a whole bunch of environmental effects there. I haven't mentioned the Stark effect, which is the electrostatic field effect. See, the list grows longer. The closer you look, the more effects you will find. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
In message 5389a141.7050...@rubidium.dyndns.org, Magnus Danielson writes: Yeah, there is a whole bunch of environmental effects there. I haven't mentioned the Stark effect, which is the electrostatic field effect. See, the list grows longer. The closer you look, the more effects you will find. Once you get to turtles it kind of settles down :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
will also look better than it really is, and for the same reasons. (Some people have even reported similar behavior with cesium standards, although I don't see how that could happen. There aren't supposed to be any first-order temperature effects in a CBT, and I'd think that any lower-order effects would be way beneath the tube's flicker floor...) The 5061 had problems with microwave field leakage known as the top cover effect (see papers by DeMarchi.) This is at least a possible mechanism for injection locking 5061's. The 5071A has a completely different microwave assembly without leakage problems. The 5071A outputs have very high reverse isolation. Tests showed that there are no detectable systematic environmental effects in the 5071A (whatever ones there are fall below the noise). Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
On Fri, May 30, 2014 at 3:24 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: Always locate your DUTs physically orthogonal to each other. Good point. Of course, if you have more than three in an ensemble then the ensuing hyperdimensional vortex may also cause unexpected cross-coupling. Henry ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Hi, I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. Cheers, Corby ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
What did NIST do with its Rubidium ensemble before they got the cesium fountain? Did they break one of the rubidiums off the ensemble, maybe in a different room with different HVAC, and look at the one vs many? Would that be useful for OCXO's, measuring one OCXO against an ensemble? Tim N3QE On 5/30/14, cdel...@juno.com cdel...@juno.com wrote: Hi, I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. Cheers, Corby ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Hi Rubidium ensemble? That would have been quite a while back. They have been running on long tube Cs standards for quite a while. Bob On May 30, 2014, at 2:03 PM, Tim Shoppa tsho...@gmail.com wrote: What did NIST do with its Rubidium ensemble before they got the cesium fountain? Did they break one of the rubidiums off the ensemble, maybe in a different room with different HVAC, and look at the one vs many? Would that be useful for OCXO's, measuring one OCXO against an ensemble? Tim N3QE On 5/30/14, cdel...@juno.com cdel...@juno.com wrote: Hi, I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. Cheers, Corby ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Well, it will reflect the true stability if they're not exposed to the same drift stimuli, right? Neglecting shared long-term aging trends, they should both end up in random-walk territory over the long run. Otherwise, if you run the two oscillators in open air in the same room or even the same building, then they will respond similarly to HVAC cycles, diurnal cycles, and whatever other environmental changes are common to both. That will make their ADEV look better than reality when you measure them against each other. It doesn't mean the long-term ADEV is necessarily invalid as a statistic, just that you probably haven't eliminated all of the common-mode influences. To the extent the two oscillators drift independently, the ADEV measurement is valid. For that matter, the isolation amps in your DMTD are also exposed to the same environment. Their residual phase tempco should be much better than any quartz oscillator, but if they're worse for some reason, they may dominate the long-term measurement. And of course, if you don't have enough isolation, you could be injection-locking the OCXOs in a really low bandwidth (days, perhaps). Shared power supply leads can also induce entrainment -- or even separate power supplies, if you run the leads right next to each other. Some of the Wenzel ULNs seem to be susceptible to this if you don't add bypassing at their power terminals. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. True, because they aren't as sensitive to environmental effects. But if you benchmark two nearby 5065As or masers carefully enough, their long-term ADEV will also look better than it really is, and for the same reasons. (Some people have even reported similar behavior with cesium standards, although I don't see how that could happen. There aren't supposed to be any first-order temperature effects in a CBT, and I'd think that any lower-order effects would be way beneath the tube's flicker floor...) -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
In message 013401cf7c46$31ac3cc0$9504b640$@miles.io, John Miles writes: (Some people have even reported similar behavior with cesium standards, although I don't see how that could happen. There aren't supposed to be any first-order temperature effects in a CBT, and I'd think that any lower-order effects would be way beneath the tube's flicker floor...) One important trick in this area: Always locate your DUTs physically orthogonal to each other. Almost none of our DUTs have 3 axis of symmetry, and therefore most environmental effects are not symmetric with respect to orientation. I noticed this by accident comparing three identical OCXO's because I had put one of them in a different orientation than the other two: The environmental noise were much larger between that one and the two other, than between the two co-aligned DUTs. I'm not entirely sure this is relevant for Rb/Cs/H, their environmentals should be attenuated enough for it to not matter. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Hi Corby, On 05/30/2014 07:26 PM, cdel...@juno.com wrote: Hi, I usually don't use drift removal as I want to see the effects of drift! Yes, but the drift effect is not best represented in the ADEV, but phase or frequency plots however. The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! Good to hear. My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. Would you care to give example plots to illustrate what difference you mean? Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Bob, The long tube Cs standard (NIST 7) is parked in the entrance. Too noisy to contribute much value. They have a bunch of 5071As and hydrogen masers. They live in individually temperature stabilized compartments. One typically is selected as the reference and then you measures differences. With these differences they then run the ensemble program on a pair of redundant PCs every 12 min. Cheers, Magnus On 05/30/2014 09:24 PM, Bob Camp wrote: Hi Rubidium ensemble? That would have been quite a while back. They have been running on long tube Cs standards for quite a while. Bob On May 30, 2014, at 2:03 PM, Tim Shoppa tsho...@gmail.com wrote: What did NIST do with its Rubidium ensemble before they got the cesium fountain? Did they break one of the rubidiums off the ensemble, maybe in a different room with different HVAC, and look at the one vs many? Would that be useful for OCXO's, measuring one OCXO against an ensemble? Tim N3QE On 5/30/14, cdel...@juno.com cdel...@juno.com wrote: Hi, I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. Cheers, Corby ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Hi The question was “Rb ensemble” …. AFIK you would have to go back quite a way to find NIST running one…. Bob On May 30, 2014, at 7:52 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Bob, The long tube Cs standard (NIST 7) is parked in the entrance. Too noisy to contribute much value. They have a bunch of 5071As and hydrogen masers. They live in individually temperature stabilized compartments. One typically is selected as the reference and then you measures differences. With these differences they then run the ensemble program on a pair of redundant PCs every 12 min. Cheers, Magnus On 05/30/2014 09:24 PM, Bob Camp wrote: Hi Rubidium ensemble? That would have been quite a while back. They have been running on long tube Cs standards for quite a while. Bob On May 30, 2014, at 2:03 PM, Tim Shoppa tsho...@gmail.com wrote: What did NIST do with its Rubidium ensemble before they got the cesium fountain? Did they break one of the rubidiums off the ensemble, maybe in a different room with different HVAC, and look at the one vs many? Would that be useful for OCXO's, measuring one OCXO against an ensemble? Tim N3QE On 5/30/14, cdel...@juno.com cdel...@juno.com wrote: Hi, I usually don't use drift removal as I want to see the effects of drift! The effects of oscillators locking together are very apparent on both the phase and AD plots when using a DMTD system. There was no indications of such locking! My point was that if you are measuring ultrastable Quartz oscillators against each other the AD at the higher Tau will not reflect the true stability of the oscillators. Only a Maser or high performance Rubidium (HP5065A) will reveal the true behavior. Cheers, Corby ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Recently I have been testing some Quartz oscillators with exceptional stability. (low parts in 10-13th) I've noticed something that jumped out at these performance levels! Normally I test oscillators on a DMTD system with either an ultra stable Quartz or a Hydrogen Maser reference. On these latest oscillators at the longer Tau (100sec.) the Quartz versus Quartz data shows much better performance than the Quartz versus Maser! What is happening (I think) in this case is that both Quartz units have exceptionally low and similar ageing. This similar ageing rate masks the true stability performance at longer Tau. The Maser data (with no effective ageing in this case) reveals the true stability at the longer Tau! Cheers! Corby Dawson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Corby, On 05/29/2014 06:15 PM, cdel...@juno.com wrote: Recently I have been testing some Quartz oscillators with exceptional stability. (low parts in 10-13th) I've noticed something that jumped out at these performance levels! Normally I test oscillators on a DMTD system with either an ultra stable Quartz or a Hydrogen Maser reference. On these latest oscillators at the longer Tau (100sec.) the Quartz versus Quartz data shows much better performance than the Quartz versus Maser! What is happening (I think) in this case is that both Quartz units have exceptionally low and similar ageing. This similar ageing rate masks the true stability performance at longer Tau. The Maser data (with no effective ageing in this case) reveals the true stability at the longer Tau! Do you have plots to share? What you describe sounds like you do not remove the drift from your data, which means that you run into the drift limitation. The linear drift shows up as a ADEV(tau) = D*tau/sqrt(2) curve. Have you tried to use the Hadamard deviation instead? Hadamard removes first degree frequency drift. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
On 5/29/2014 9:15 AM, cdel...@juno.com wrote: On these latest oscillators at the longer Tau (100sec.) the Quartz versus Quartz data shows much better performance than the Quartz versus Maser! What is happening (I think) in this case is that both Quartz units have exceptionally low and similar ageing. Or alternately, the quartz units are injection locking to each other. Rick ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Am 29.05.2014 18:15, schrieb cdel...@juno.com: On these latest oscillators at the longer Tau (100sec.) the Quartz versus Quartz data shows much better performance than the Quartz versus Maser! Could it be that they try to lock to each other, given enough time? regards, Gerhard What is happening (I think) in this case is that both Quartz units have exceptionally low and similar ageing. This similar ageing rate masks the true stability performance at longer Tau. The Maser data (with no effective ageing in this case) reveals the true stability at the longer Tau! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Caveats on Allan Deviation with ultra stable oscillators
Hi, On 05/29/2014 06:47 PM, Richard (Rick) Karlquist wrote: On 5/29/2014 9:15 AM, cdel...@juno.com wrote: On these latest oscillators at the longer Tau (100sec.) the Quartz versus Quartz data shows much better performance than the Quartz versus Maser! What is happening (I think) in this case is that both Quartz units have exceptionally low and similar ageing. Or alternately, the quartz units are injection locking to each other. When they do, they drift together, so the delta-drift is zero and thus do not polute the measurement. Injection locking would also cancel some of the noise naturally, depends if one oscillator locks to the other or if both locks to each other. Running one of them off frequency would reduce the noise cancellation due to injection locking. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
