Re: [time-nuts] How long do ovens take to cool to ambient after power is removed?
On 10/02/2014 06:03 AM, Richard (Rick) Karlquist wrote: On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. Just putting a card-board box around the oscillator does indeed make short term deviation (breath, hand-waving, walking around and pushing air) reduce significantly. What is needed to get anything decent out of crap oscillators. Doesn't do as much for longer term shifts (AC, day-variations etc) Your cool-off numbers is about where I would guess for better ovens. Naturally, a fan can speed the process up, but let it sit there for some time without the fan to have less temperature gradients. 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] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on
David, The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen one on the brink of oscillation. TCXO will not have the same wide range, as it compensate for the temperature. Cheers, Magnus On 10/01/2014 10:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: Further to my question the other day about what type of oscillator was used in the HP 8720D VNA, fitted with the high stability oscillator option (1D5), here is the frequency as the instrument is switched on, after being powered off for 2-3 hours. The oscillator appears to start too high in frequency, overshoots downwards, then settles down. It would be a somewhat useless exercise collecting data for much loonger and looking at in detail, since I don't know the accuracy of the HP spectrum analyzer. But that had been on for at least 24 hours. The measurement system was an HP 7 system spectrum analyzer, fitted with the 70310A precision frequency reference. This has not been calibrated in years. I will get one of those Jackson labs GPS frequency references, then I will know what the frequency is!! Assuming the crystal frequency is only a function of temperature, (and I know that not to be the case), it looks as if the oven is under damped to me. Is this behavior typical of a TCXO, OCXO or whatever ?? Any comments??? Dave ___ 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] Clock level conversion 5V - 3.3V
Would it not be better for phase noise to use a logic gate with a fast transition than a resistive divider that would be slower due to the load capacitance? David On 10/1/14 7:09 AM, Bob Camp wrote: Hi Ok, so it’s not a super duper low phase noise OCXO. It’s also at a reasonably high frequency. I’d just drive it into a 5V tolerant input and move on. There are lots of logic gate chips out there that will run from 3.3 and accept 5V inputs. Use something reasonably fast and it will do a pretty good job. Bob On Sep 30, 2014, at 10:11 PM, Mark A. Haun hau...@keteu.org wrote: Hi Bob, The OCXO is one of those 26-MHz ebay Pletronics from a couple years back. I would like to not degrade its close-in phase noise (quoted as -100 dBc @ 10 Hz, -130 dBc @ 100 Hz). Thinking about Said's suggestion to phase lock a higher-frequency sampling clock to this, with a loop BW somewhere in the 10-100 Hz range. I have seen a resistive divider used in a similar application, but wondered if I could save the couple dozen mA they were spending. Mark On Tue, 30 Sep 2014 20:18:56 -0400 Bob Camp kb...@n1k.org wrote: Hi How quiet does it need to be? Put another way - how good is the OCXO? What frequency are we talking about? What is the phase noise “need” after you get to 3.3V (is there a system spec)? Bob On Sep 30, 2014, at 5:46 PM, Mark Haun hau...@keteu.org wrote: Is there a best way to do this without adding phase noise? For example, a 5V OCXO into an ADF4002, or a 3.3V or even 1.8V logic input. Is a resistive divider the way to go? Mark ___ 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.
Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on
On 2 Oct 2014 07:10, Magnus Danielson mag...@rubidium.dyndns.org wrote: David, The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen one on the brink of oscillation. Thank you. Do you know the likely cause of the somewhat odd behaviour between about 150 and 220 s? This eBay auction, which someone posted http://m.ebay.com/itm/151256172424 says it's the high stability oscillator for an HP 8753D or 8753ES. I checked the part number at parts.keysight.comand it would appear it is the same as used in my VNA and several other microwave VNAs. That said, I have noticed a few errors on parts.agilent.com, one of which resulted in me buying the wrong part. I was later warned by Agilent not to trust the accuracy too much, especially on older equipment. It is better to check with them before making purchases. But they have a very helpful parts service that does make every effort to sort out what parts are. They spent quite some time finding out what connectors were on am obsolete cable for me. TCXO will not have the same wide range, as it compensate for the temperature. This answers my original curiosity now - did I have an OCXO or TCXO. Although I am not going to bother, as it will be easier and more accurate to feed the VNA from a rubidium or GPS locked TCXO/OCXO, it would probably be possible to buy one of those off of eBay and replace the OCXO with a better one. Then stick it in my VNA - I would not want to modify the original one. There have some rather small double oven OCXOs on eBay recently for very little money. From the earlier comments about this oscillator, it would appear its specification is quite poor for an OCXO. Cheers, Magnus Thank you. Dave ___ 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] Clock level conversion 5V - 3.3V
Hi It will indeed be better for phase noise to do away with the resistive divider and get faster edges. Of course there are indeed resistive dividers that don’t slow things down. It’s unlikely that a divider with a 10 ohm output impedance is going to tack on to the output of an OCXO. The real point is that (in this case) you can get the job done for less than 10 cents with a single gate chip. They are available in many packages from many people. There are indeed chips that have a bit less noise than others. With the OCXO that we’re talking about here, it’s not worth going crazy to find this or that. This being Time Nuts, if you do decide to go crazy - as long as it’s saturated silicon, faster is more quiet than slower. Bob On Oct 1, 2014, at 9:21 AM, David McGaw n1...@dartmouth.edu wrote: Would it not be better for phase noise to use a logic gate with a fast transition than a resistive divider that would be slower due to the load capacitance? David On 10/1/14 7:09 AM, Bob Camp wrote: Hi Ok, so it’s not a super duper low phase noise OCXO. It’s also at a reasonably high frequency. I’d just drive it into a 5V tolerant input and move on. There are lots of logic gate chips out there that will run from 3.3 and accept 5V inputs. Use something reasonably fast and it will do a pretty good job. Bob On Sep 30, 2014, at 10:11 PM, Mark A. Haun hau...@keteu.org wrote: Hi Bob, The OCXO is one of those 26-MHz ebay Pletronics from a couple years back. I would like to not degrade its close-in phase noise (quoted as -100 dBc @ 10 Hz, -130 dBc @ 100 Hz). Thinking about Said's suggestion to phase lock a higher-frequency sampling clock to this, with a loop BW somewhere in the 10-100 Hz range. I have seen a resistive divider used in a similar application, but wondered if I could save the couple dozen mA they were spending. Mark On Tue, 30 Sep 2014 20:18:56 -0400 Bob Camp kb...@n1k.org wrote: Hi How quiet does it need to be? Put another way - how good is the OCXO? What frequency are we talking about? What is the phase noise “need” after you get to 3.3V (is there a system spec)? Bob On Sep 30, 2014, at 5:46 PM, Mark Haun hau...@keteu.org wrote: Is there a best way to do this without adding phase noise? For example, a 5V OCXO into an ADF4002, or a 3.3V or even 1.8V logic input. Is a resistive divider the way to go? Mark ___ 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 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] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on
The overshoot behavior from 150 to 220 seconds is exactly what you expect for slightly less than critical damping which is where many closed loops end up when rapid lock or warmup is a criteria. Most rapid warmup is almost always the design point of an OCXO oven. Tim N3QE On Thu, Oct 2, 2014 at 3:21 AM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: On 2 Oct 2014 07:10, Magnus Danielson mag...@rubidium.dyndns.org wrote: David, The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen one on the brink of oscillation. Thank you. Do you know the likely cause of the somewhat odd behaviour between about 150 and 220 s? This eBay auction, which someone posted http://m.ebay.com/itm/151256172424 says it's the high stability oscillator for an HP 8753D or 8753ES. I checked the part number at parts.keysight.comand it would appear it is the same as used in my VNA and several other microwave VNAs. That said, I have noticed a few errors on parts.agilent.com, one of which resulted in me buying the wrong part. I was later warned by Agilent not to trust the accuracy too much, especially on older equipment. It is better to check with them before making purchases. But they have a very helpful parts service that does make every effort to sort out what parts are. They spent quite some time finding out what connectors were on am obsolete cable for me. TCXO will not have the same wide range, as it compensate for the temperature. This answers my original curiosity now - did I have an OCXO or TCXO. Although I am not going to bother, as it will be easier and more accurate to feed the VNA from a rubidium or GPS locked TCXO/OCXO, it would probably be possible to buy one of those off of eBay and replace the OCXO with a better one. Then stick it in my VNA - I would not want to modify the original one. There have some rather small double oven OCXOs on eBay recently for very little money. From the earlier comments about this oscillator, it would appear its specification is quite poor for an OCXO. Cheers, Magnus Thank you. Dave ___ 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] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on
As to oscillation: most older octal style crystal ovens have no proportional control at all, they are simply a bimetallic click-on-click-off thermostatic switch that is on or off, and after initial warmup they cycle up and down every few minutes. A tiny fraction of the better octal crystal ovens have some proportional heater control. Tim N3QE On Thu, Oct 2, 2014 at 2:10 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: David, The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen one on the brink of oscillation. TCXO will not have the same wide range, as it compensate for the temperature. Cheers, Magnus On 10/01/2014 10:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: Further to my question the other day about what type of oscillator was used in the HP 8720D VNA, fitted with the high stability oscillator option (1D5), here is the frequency as the instrument is switched on, after being powered off for 2-3 hours. The oscillator appears to start too high in frequency, overshoots downwards, then settles down. It would be a somewhat useless exercise collecting data for much loonger and looking at in detail, since I don't know the accuracy of the HP spectrum analyzer. But that had been on for at least 24 hours. The measurement system was an HP 7 system spectrum analyzer, fitted with the 70310A precision frequency reference. This has not been calibrated in years. I will get one of those Jackson labs GPS frequency references, then I will know what the frequency is!! Assuming the crystal frequency is only a function of temperature, (and I know that not to be the case), it looks as if the oven is under damped to me. Is this behavior typical of a TCXO, OCXO or whatever ?? Any comments??? Dave ___ 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] How long do ovens take to cool to ambient after power is removed?
The most extreme example of slow ovenized oscillator warm-up I've seen is the vintage hp106. These mid-1960's oscillators were designed as the ultimate, hp way, pre-atomic, frequency standard -- expected to be powered up, uninterrupted, for years and decades. So there was no hurry in the (perhaps once-in-a-lifetime) initial warm-up. Here's a plot/photo of one I recently tested: http://leapsecond.com/museum/hp106a/ These HP-106 oscillators are among the best I have ever measured: stability and daily drift rates in the very low -13's. Like the SR-71, these were designed by gut and slide rule. And yet achieved extreme performance, even by today's standards. The amazing thing -- as you know from your enviable career at HP -- is that an instrument produced in 1964 can still work 50 years later in 2014. No blown fuses, no electrolytics, no filaments, no f/w upgrades, no Y2K, no decaying EEPROM, no batteries, not even any IC's. No user s/w, no USB, no drivers, no OS. Not even an on/off switch! Just a 5-pin 24VDC backup or 2-prong AC cord in and a pure 5 MHz BNC out, that's all. How many of the instruments we use today will still work out-of-the-box in 2064? /tvb - Original Message - From: Richard (Rick) Karlquist rich...@karlquist.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Wednesday, October 01, 2014 9:03 PM Subject: Re: [time-nuts] How long do ovens take to cool to ambient after power is removed? On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. 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] How long do ovens take to cool to ambient after power is removed?
Tom, Nice performance. Wish we could get that today! My fairly modern BVA is nowhere near that stability. If you open up a brand new DOCXO you will see a crystal designed in the 70's and an oscillator circuit designed sometime in the 30's or 40's, maybe updated to a more or less modern transistor.. Once you have the recipe, there is no need to change it really.. Bye, Said Sent From iPhone On Oct 2, 2014, at 11:58, Tom Van Baak t...@leapsecond.com wrote: The most extreme example of slow ovenized oscillator warm-up I've seen is the vintage hp106. These mid-1960's oscillators were designed as the ultimate, hp way, pre-atomic, frequency standard -- expected to be powered up, uninterrupted, for years and decades. So there was no hurry in the (perhaps once-in-a-lifetime) initial warm-up. Here's a plot/photo of one I recently tested: http://leapsecond.com/museum/hp106a/ These HP-106 oscillators are among the best I have ever measured: stability and daily drift rates in the very low -13's. Like the SR-71, these were designed by gut and slide rule. And yet achieved extreme performance, even by today's standards. The amazing thing -- as you know from your enviable career at HP -- is that an instrument produced in 1964 can still work 50 years later in 2014. No blown fuses, no electrolytics, no filaments, no f/w upgrades, no Y2K, no decaying EEPROM, no batteries, not even any IC's. No user s/w, no USB, no drivers, no OS. Not even an on/off switch! Just a 5-pin 24VDC backup or 2-prong AC cord in and a pure 5 MHz BNC out, that's all. How many of the instruments we use today will still work out-of-the-box in 2064? /tvb - Original Message - From: Richard (Rick) Karlquist rich...@karlquist.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Wednesday, October 01, 2014 9:03 PM Subject: Re: [time-nuts] How long do ovens take to cool to ambient after power is removed? On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. 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. ___ 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] How long do ovens take to cool to ambient after power is removed?
Len Cutler was pretty much allowed to do whatever he wanted on the HP106 and he produced the proverbial doomsday machine. I think the SR-71 analogy is good here, except that Kelly Johnson had a lot more support from his management. Len always wanted to make an optically pumped cesium as his ultimate doomsday machine, but management never funded it. He proudly had a 106 on display in his office. I wish I had asked him how he got such low aging crystals. 10811 crystals never got much lower than about 1 part in 10^-10 per day. Rick Karlquist N6RK On 10/2/2014 11:58 AM, Tom Van Baak wrote: The most extreme example of slow ovenized oscillator warm-up I've seen is the vintage hp106. These mid-1960's oscillators were designed as the ultimate, hp way, pre-atomic, frequency standard -- expected to be powered up, uninterrupted, for years and decades. So there was no hurry in the (perhaps once-in-a-lifetime) initial warm-up. Here's a plot/photo of one I recently tested: http://leapsecond.com/museum/hp106a/ These HP-106 oscillators are among the best I have ever measured: stability and daily drift rates in the very low -13's. Like the SR-71, these were designed by gut and slide rule. And yet achieved extreme performance, even by today's standards. The amazing thing -- as you know from your enviable career at HP -- is that an instrument produced in 1964 can still work 50 years later in 2014. No blown fuses, no electrolytics, no filaments, no f/w upgrades, no Y2K, no decaying EEPROM, no batteries, not even any IC's. No user s/w, no USB, no drivers, no OS. Not even an on/off switch! Just a 5-pin 24VDC backup or 2-prong AC cord in and a pure 5 MHz BNC out, that's all. How many of the instruments we use today will still work out-of-the-box in 2064? /tvb - Original Message - From: Richard (Rick) Karlquist rich...@karlquist.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Wednesday, October 01, 2014 9:03 PM Subject: Re: [time-nuts] How long do ovens take to cool to ambient after power is removed? On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. 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. ___ 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] How long do ovens take to cool to ambient after power is removed?
Hi That 106 comes up *fast*. Take a look at the GR equivalent if you want to see slow….. Bob On Oct 2, 2014, at 2:58 PM, Tom Van Baak t...@leapsecond.com wrote: The most extreme example of slow ovenized oscillator warm-up I've seen is the vintage hp106. These mid-1960's oscillators were designed as the ultimate, hp way, pre-atomic, frequency standard -- expected to be powered up, uninterrupted, for years and decades. So there was no hurry in the (perhaps once-in-a-lifetime) initial warm-up. Here's a plot/photo of one I recently tested: http://leapsecond.com/museum/hp106a/ These HP-106 oscillators are among the best I have ever measured: stability and daily drift rates in the very low -13's. Like the SR-71, these were designed by gut and slide rule. And yet achieved extreme performance, even by today's standards. The amazing thing -- as you know from your enviable career at HP -- is that an instrument produced in 1964 can still work 50 years later in 2014. No blown fuses, no electrolytics, no filaments, no f/w upgrades, no Y2K, no decaying EEPROM, no batteries, not even any IC's. No user s/w, no USB, no drivers, no OS. Not even an on/off switch! Just a 5-pin 24VDC backup or 2-prong AC cord in and a pure 5 MHz BNC out, that's all. How many of the instruments we use today will still work out-of-the-box in 2064? /tvb - Original Message - From: Richard (Rick) Karlquist rich...@karlquist.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Wednesday, October 01, 2014 9:03 PM Subject: Re: [time-nuts] How long do ovens take to cool to ambient after power is removed? On 10/1/2014 1:04 PM, Hal Murray wrote: drkir...@kirkbymicrowave.co.uk said: Anyway, later today (tomorrow ??) I will post a plot of frequency vs time. The question is though, how long is thing thing likely to take too cool? I'd expect an exponential decay so you need to specify how close to ambient you want to get. I'd guess a ballpark of 10x the warm up rate. You can probably measure it if you have the warmup graph. Turn it off, wait a while, turn it on, measure the freq, consult warmup graph. When I was still with Agilent, I did some experiments with unpowered 10811's. Both the oven and oscillator were unpowered and I measured the temperature by looking at the B mode resonance of the crystal. I wanted to get rid of any linear frequency drift. As a rough rule of thumb, 1 hour of cool down is pretty good for most purposes. For extreme measurements, I would allow 10 hours. This reduced any exponential tail to below the ability to measure temperature and/or below the effects of the ambient. I had to put a box over it to reduce the effects of air currents. If I did not do that, then 1 hour was all I needed. 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. ___ 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.
