Re: [time-nuts] Morion MV89A position
Dave wrote: What I'm interested in achieving is the lowest posible energy requirement for a set of quartz frequency stds. It seems to me that using the close to iso-thermal 'hole in the ground' arrangement is a useful step in that direction as it should minimise the power necessary for environmental control. Very interesting. I think the answer is, maybe, and maybe not. Assuming that the average ground temperature is lower than the average air temperature wherever they would be located if they were not underground, the ovens would have to run harder (on average) in the underground location. On the other hand, if you were able to reduce the crystal temperature because of much greater subterranean temperature stability, you might make it a wash or even lower the heater power consumption. However, crystals work best at their design temperature, so obtaining good performance at a lower crystal temperature might require a complete oscillator redesign with crystals made specifically for the lower temperature. So, the "oscillator in a box" could end up being the most efficient choice if you aren't going to redesign the oscillators and do not want to sacrifice the specified frequency stability of your off-the-shelf oscillator. Decisions, decisions. Would it be practical to install solar/wind/geothermal/etc. power generating equipment sufficient to support the standards in an emergency? (I'd think solar would be the least likely to be interrupted by natural disasters, but as soon as you go that way your next disaster would surely be a volcanic eruption that blots out the sun for months) Best regards, Charles ___ 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] Looking for high reverse isolation amplifier
Can anyone direct me to an amplifier with: 1. High reverse isolation (over 40 dB). Note: the spec of interest is *reverse* isolation, not port to port isolation in a distribution amplifier. 2. Low phase noise (less than -100 dBc/Hz at 1 Hz offset) 3. Works at 200 MHz The Q-Bit QBH-1401PM seems promising...if I can get one. If necessary I will build the amplifier if I can get a known good schematic to follow, but prefer to buy one. Thanks in advance. 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] Ovenair OSC 49-38B
I have one of these oscilators and wanted to test it. I saw your post on time-nuts, do you still have the connection information and did you find a schematic? Thanks for any help you can give. Dave T ___ 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] GR 1115-C from the E
Some bad news The unit on the E looked very clean, hardly a scratch. Explained to the seller how things like rack mount equipment can take a hit where the ears stick out (front panel in this case), handles etc. I paid and extra $20 to have it double boxed and it arrived with the outer box in pretty good shape. The seller did not respond to my query if it could go some other shipper such as FedEx Ground. When I took it out of the box one could hear a faint rattle inside, first thought typical GR, a screw came loose. Typical in that GR in many cases did not use lock washers on some screws/nuts for some reason. The next day, I pulled off the cover and one could see little bits of glass .. hmm ...some were silvered. Well off came the snap cover to the end of the oven assenbly and I'll let the pictures do the talking http://goo.gl/1XZnkI I've asked the seller if s/he heard any rattle noises when s/he packed it up -pete BTW goo.gl is Google's URL shortener ___ 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] Interesting oscillator set up...Symmetricom
Hey All, I recently came into a few CO clock modules made by Symmetricom, Austron, etc. These were Stratum 3E level clocks. One of the modules can be seen here pictures 2,3,4 http://rescueelectronics.com/timeplot The module ran in the position where the heatsink fins were vertical. The heatsinks had nothing to do in this module as there no active component connected to it If you look closely you can see that the actual oscillator is electrically isolated from the alum. holder. There were really no power components on the module that needed cooling. Then I thought, could this be an example of thermal capacitance in play here. Three is a lot of thermal mass not directly connected to the oscillator, What do you guys think? BTW if anyone could help me with me pin outs for this unit I would be much obliged Thank you PauLC W1VLF ___ 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] Morion MV89A position
Thanks- What I'm interested in achieving is the lowest posible energy requirement for a set of quartz frequency stds. It seems to me that using the close to iso-thermal 'hole in the ground' arrangement is a useful step in that direction as it should minimise the power necessary for environmental control. When we had the bad quakes here back in 2010/2011 I lost all power to the gear for several days and the backup batteries only held it running for about 36 hours. This, after the oscillators had been running continuously for 7 years. So, rather than invest heavily in a higher capacity battery bank, I'm looking to get the lowest energy requirement for the essential things like reference oscillators and a minor amount of logging eqpt. Inconvenience re access etc is a minor issue in the overall scheme of things from my point of view. I guess I may have to just try it. Regards Dave Brown Christchurch, NZ - Original Message - From: "Charles Steinmetz" To: "Discussion of precise time and frequency measurement" Sent: Thursday, January 30, 2014 2:44 PM Subject: Re: [time-nuts] Morion MV89A position Dave wrote: what about replacing your aluminium box with a, say 2 foot piece of 6 inch pvc pipe (ocxo suspended inside it clear of the wall and sealed off ends) and burying that a few feet in the ground? I share Poul-Henning's lack of enthusiasm for burying electronics. But if you try it, I'd be interested in hearing how it works. Depending on your climate, you may need to go deeper than a few feet to achieve a reasonable approximation to isothermy. Of course, even a few feet should get you to where the rate of change of temperature is quite slow and the peak-to-peak swing is lower than the outside air temperature. (But is that the standard? Aren't most time-nuts labs in climate-controlled living spaces?). If you really want to go nuts, it's pretty simple to put the cast aluminum box into a larger enclosure with a small, thermostatically controlled fan. If you bond a temperature sensor to the inside wall of the cast box, it's easy to hold the temperature of the cast box to well within 0.1C. Best regards, Charles ___ 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] Morion MV89A position
In the 70's I did a 4 inch pipe 20 feet in the ground in Dallas. Temperature was better than 0.1 C. Got canvas coin bags from my local bank filled them with sand and lowered them one at a time with line each one a subsequent number. Used it for 18 years. Bert Kehren In a message dated 1/29/2014 8:46:29 P.M. Eastern Standard Time, csteinm...@yandex.com writes: Dave wrote: >what about replacing your aluminium box with a, say 2 foot piece >of 6 inch pvc pipe (ocxo suspended inside it clear of the wall and >sealed off ends) and burying that a few feet in the ground? I share Poul-Henning's lack of enthusiasm for burying electronics. But if you try it, I'd be interested in hearing how it works. Depending on your climate, you may need to go deeper than a few feet to achieve a reasonable approximation to isothermy. Of course, even a few feet should get you to where the rate of change of temperature is quite slow and the peak-to-peak swing is lower than the outside air temperature. (But is that the standard? Aren't most time-nuts labs in climate-controlled living spaces?). If you really want to go nuts, it's pretty simple to put the cast aluminum box into a larger enclosure with a small, thermostatically controlled fan. If you bond a temperature sensor to the inside wall of the cast box, it's easy to hold the temperature of the cast box to well within 0.1C. Best regards, Charles ___ 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] help me understand AM noise
Thanks for the link. My current lineup is: 13 dBm source -> variable attenuator -> amp -> variable attenuator -> amp -> filter -> pad -> amp -> filter -> 20 dBm output I think I already paid attention to interleaving gain and loss, as well as not reducing the signal to very low levels so as to gain up the noise floor too much. At the moment I am also not much concerned with ALC behavior or stability as the AM noise measurements do not show much issue with this. Mostly I am concerned with additive noise from the somewhat complex opamp circuits driving (and linearizing) the series/shunt topology microwave FET voltage-variable attenuators. I would like to understand what changes in noise floor are just a result of attenuating the RF chain over it's amplitude control range, and what noise I am adding by my imperfect (noisy) attenuator driver circuitry. I have already made some improvements in this area by bandwidth-limiting the opamps (I need about 1 MHz 3 dB corner for ALC stability and AM modulation) and switching to some lower noise opamps. So clearly it was not perfect. Just trying to figure out how much is added AM noise by my circuit and how much is laws of physics by increasing the attenuation. Lifespeed On Wed, 1/29/14, John Miles wrote: Subject: Re: [time-nuts] help me understand AM noise To: "'Discussion of precise time and frequency measurement'" Date: Wednesday, January 29, 2014, 4:46 PM If you're just using a single attenuator at the input of your PA, it makes sense that the additive noise in dBc terms is worse at lower output levels. Disregarding saturation for the moment, the PA is adding just as much noise to a low-level input signal as it does to a high-level signal. ALC-controlled amps need to be designed with multiple alternating stages of attenuation and gain. Whatever drives the PIN diodes or other attenuators also needs to be quiet and well-filtered, of course -- which also means keeping an eye on feedback stability. My (least) favorite counterexample is the IF amp in the HP 11729C noise test set. It's not even an ALC amplifier, but a true limiting amplifier. It was implemented by cascading several high-gain MMICs with clamp diodes between each stage. Makes a nice comb generator. They were driving a mixer so they would have reasoned that odd harmonics were acceptable, but because there was no interstage attenuation for low-level noise, the amplifier's additive AM and PM levels were awful. You'll see similar performance if you measure the additive noise of a comparator or other limiting amp. Several limiting amps were used in the HP 8662A/8663A synthesizer as well, which is why they have good close-in noise but a relatively poor white noise floor. As long as you avoid these mistakes you'll be ahead of 90% of the crowd. As far as further reading goes, check out http://rubiola.org/index.html . -- john, KE5FX Miles Design LLC > -Original Message- > From: time-nuts-boun...@febo.com [mailto:time-nuts- > boun...@febo.com] On Behalf Of life speed > Sent: Wednesday, January 29, 2014 10:32 AM > To: time-nuts@febo.com > Subject: [time-nuts] help me understand AM noise > > Hi Guys. It has been a while since I posted, hope you can help with a slightly > time-related topic. Can't have frequency without amplitude . . . > > I recently designed an Automatic Level Control circuit consisting of dual- > slope detector logger, open and closed loop references with AM > modulation, and a linearizer (volts/dB) driver for series/shunt microwave > attenuators. This is part of a DC - 20 GHz microwave synthesizer. I measured > the AM noise at 3 GHz, both open and closed loop, and find the noise level > is higher at the output of the attenuator/amplifier chain at similar power > levels to the input (13 dBm). The input RF chain saturates at about 17 dBm, > while the output amp following the attenuators saturates at about 20 dBm. > > I understand that an amplifier in compression will suppress AM noise. What > I wonder is are my measurements of increased AM noise (red trace) at the > output of the attenuator/amp lineup to be expected based on the higher > available saturated power? Is it possible to attenuate the signal using the > power control (open loop in this example, ALC is not used) without > degrading AM noise performance? Does anybody have any suggested > reading on this subject? I am trying to understand how well my circuit > performs, in general. I do observe that control the power to a lower level > increases the AM noise. But it is a relative measurement to begin with, so > what is "good"? I have been reading the Agilent E5500 user guide on AM > noise measurements, but don't find a great deal of information there > regarding AM noise performance of a Device Under Test. >
Re: [time-nuts] Morion MV89A position
Dave wrote: what about replacing your aluminium box with a, say 2 foot piece of 6 inch pvc pipe (ocxo suspended inside it clear of the wall and sealed off ends) and burying that a few feet in the ground? I share Poul-Henning's lack of enthusiasm for burying electronics. But if you try it, I'd be interested in hearing how it works. Depending on your climate, you may need to go deeper than a few feet to achieve a reasonable approximation to isothermy. Of course, even a few feet should get you to where the rate of change of temperature is quite slow and the peak-to-peak swing is lower than the outside air temperature. (But is that the standard? Aren't most time-nuts labs in climate-controlled living spaces?). If you really want to go nuts, it's pretty simple to put the cast aluminum box into a larger enclosure with a small, thermostatically controlled fan. If you bond a temperature sensor to the inside wall of the cast box, it's easy to hold the temperature of the cast box to well within 0.1C. Best regards, Charles ___ 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] help me understand AM noise
If you're just using a single attenuator at the input of your PA, it makes sense that the additive noise in dBc terms is worse at lower output levels. Disregarding saturation for the moment, the PA is adding just as much noise to a low-level input signal as it does to a high-level signal. ALC-controlled amps need to be designed with multiple alternating stages of attenuation and gain. Whatever drives the PIN diodes or other attenuators also needs to be quiet and well-filtered, of course -- which also means keeping an eye on feedback stability. My (least) favorite counterexample is the IF amp in the HP 11729C noise test set. It's not even an ALC amplifier, but a true limiting amplifier. It was implemented by cascading several high-gain MMICs with clamp diodes between each stage. Makes a nice comb generator. They were driving a mixer so they would have reasoned that odd harmonics were acceptable, but because there was no interstage attenuation for low-level noise, the amplifier's additive AM and PM levels were awful. You'll see similar performance if you measure the additive noise of a comparator or other limiting amp. Several limiting amps were used in the HP 8662A/8663A synthesizer as well, which is why they have good close-in noise but a relatively poor white noise floor. As long as you avoid these mistakes you'll be ahead of 90% of the crowd. As far as further reading goes, check out http://rubiola.org/index.html . -- john, KE5FX Miles Design LLC > -Original Message- > From: time-nuts-boun...@febo.com [mailto:time-nuts- > boun...@febo.com] On Behalf Of life speed > Sent: Wednesday, January 29, 2014 10:32 AM > To: time-nuts@febo.com > Subject: [time-nuts] help me understand AM noise > > Hi Guys. It has been a while since I posted, hope you can help with a slightly > time-related topic. Can't have frequency without amplitude . . . > > I recently designed an Automatic Level Control circuit consisting of dual- > slope detector logger, open and closed loop references with AM > modulation, and a linearizer (volts/dB) driver for series/shunt microwave > attenuators. This is part of a DC - 20 GHz microwave synthesizer. I measured > the AM noise at 3 GHz, both open and closed loop, and find the noise level > is higher at the output of the attenuator/amplifier chain at similar power > levels to the input (13 dBm). The input RF chain saturates at about 17 dBm, > while the output amp following the attenuators saturates at about 20 dBm. > > I understand that an amplifier in compression will suppress AM noise. What > I wonder is are my measurements of increased AM noise (red trace) at the > output of the attenuator/amp lineup to be expected based on the higher > available saturated power? Is it possible to attenuate the signal using the > power control (open loop in this example, ALC is not used) without > degrading AM noise performance? Does anybody have any suggested > reading on this subject? I am trying to understand how well my circuit > performs, in general. I do observe that control the power to a lower level > increases the AM noise. But it is a relative measurement to begin with, so > what is "good"? I have been reading the Agilent E5500 user guide on AM > noise measurements, but don't find a great deal of information there > regarding AM noise performance of a Device Under Test. > > Thanks, > > Lifespeed > > http://home.comcast.net/~claybu/pics/electronics/am_noise_1.png > ___ 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] RE(1): shack
YOu have been hacked On Wed, Jan 29, 2014 at 12:58 PM, B Riches wrote: > http://conseilavie.fr/labofit/for.u.info.bro.html > > > ---=-=-=-=-=-=-=-=-=-=-=-=-=-- > > From: B Riches 1/29/2014 9:58:05 PM > ___ > 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] Morion MV89A position
In message <49FC2443D640492C93DD9E1FE20F705D@athlon3200>, "Dave Brown" writes: >It's not practicable for many people but - what about replacing your >aluminium box with a, say 2 foot piece of 6 inch pvc pipe (ocxo suspended >inside it clear of the wall and sealed off ends) and burying that a few feet >in the ground? In general burying things is much more trouble than it's worth. -- 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] Morion MV89A position
Charles It's not practicable for many people but - what about replacing your aluminium box with a, say 2 foot piece of 6 inch pvc pipe (ocxo suspended inside it clear of the wall and sealed off ends) and burying that a few feet in the ground? I expect the thermal mass of the pvc is not as high as the aluminium but the external ground temperature will be lower than air ambient as well as having much less variation. Overall, I'm not sure what the result might be. DaveB, NZ - Original Message - From: "Charles Steinmetz" To: "Discussion of precise time and frequency measurement" Sent: Thursday, January 30, 2014 9:28 AM Subject: Re: [time-nuts] Morion MV89A position /tvb wrote: I tried something like that and ended up frying the oscillator! The problem was that I used too much insulation. That was good to keep ambient temperature transients out but it also kept internal heat generation in. * * * My question is, how does one design an enclosure to prevent this mistake? Or is it trial and error. Perhaps put a thermistor on the OCXO and if the case temperature rises beyond what is normal case temperature in free air, then the enclosure has too much insulation? That is the point of distinguishing thermal capacitance (= thermal mass) from thermal resistance. Generally, OCXOs are thermally designed to be "naked" in some abient environment that is close to room temperature (usually somewhat above, anticipating they will be installed in warm instruments and not be sitting naked on a desktop). They will work acceptably in an ambient environment ranging some tens of degrees C above and below this, as long as the ambient temperature does not change too fast for the oven controller to keep up (for example, the HP 10811 is rated for -55C to 71C, with degraded temperature stability below 0C). Adding additional thermal resistance (your insulation, or Paul's Dewar) unbalances the heat flow to ambient. In theory, the oscillator should respond by backing down the heater current to match heater power to the new thermal resistance. However, raising the thermal resistance can destabilize the thermal control loops in some OCXOs. When that happens, you get poor thermal regulation at best and you burn down the oscillator at worst. (And even if the control loop does not destabilize, it won't be running at the design center "sweet spot" foreseen by the designers, so thermal stability will likely be degraded.) What you want to do is keep the net thermal *resistance* similar to what it is with the oscillator in its target environment, and add thermal *capacitance* to slow down the changes in the oscillator's immediate environment (i.e., just outside the oscillator can). The metal box does just that. The thermally resistive path is essentially still all air, just as it is with the oscillator sitting on a desktop -- from the oscillator through the air surrounding it to the inside wall of the cast box, then from the outside wall of the cast box through the air to ambient (to a first approximation, the temperature of the inside wall of the box is the same as the temperature of the outside wall). This way, the average thermal resistance from the OCXO to ambient is still similar to what the thermal designers contemplated. However, the cast box averages (integrates) the outside temperature as seen by the OCXO with a time constant measured in tens of minutes. The net result is that the oscillator is in (or very close to) its design environment with respect to the average heat loss, so the oven controller is working at (or very near) its design sweet spot -- but at the same time, the rate of temperature change seen by the OCXO (i.e., its immediate environment inside the cast box) is integrated over tens of minutes. If the ambient temperature did not change at all, the OCXO's immediate environment inside the box would be exactly the same as if it were not in the box but, rather, sitting naked on a desktop. When the ambient temperature changes fast, the OCXO's immediate environment follows it -- but much more slowly, giving the oven control loop time to adjust to the change without introducing a transient error. As long as you end up with sufficient thermal capacitance to slow all expected thermal transients down to the point that the oven control loop has no trouble keeping the quartz crystal in an isothermal state, you have done all you need to do. There is nothing to calculate, and no complicated design procedure. If the oscillator still exhibits some transient thermal error, just increase the mass of the box by mounting aluminum plates to the outside walls of the cast box until it doesn't. The one exception to this would be if the oven controller simply has too little gain to keep the crystal isothermal, in which case there would be a DC (not transient) error (each ambient temperature would be associated with a unique crystal temp
[time-nuts] WARNING: MALWARE LINK Re: RE(1): shack
MALWARE LINK. -John > http://conseilax.u.info.bro.html > > ---=-=-=-=-=-=-=-=-=-=-=-=-=-- > > From: B Riches 1/29/2014 9:58:05 PM > ___ > 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] Morion MV89A position
In message <20140130002839.scaeu...@smtp9.mail.yandex.net>, Charles Steinmetz w rites: >That is the point of distinguishing thermal capacitance (= thermal >mass) from thermal resistance. ...and to nobodys surprise, the professionals work in "thermal impedance" which manages to work just the way you expect :-) -- 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] Morion MV89A position
> > My question is, how does one design an enclosure to prevent this > mistake? Or is it trial and error. Perhaps put a thermistor on the OCXO > and if the case temperature rises beyond what is normal case temperature > in free air, then the enclosure has too much insulation? I suggest a thorough reading of Schaum's summary book on heat transfer, or get a secondhand copy of Incropera & DeWitt (?sp). It's pretty simple to build models for the planned enclosures. For example, the enclosures with insulation are mostly conduction transfer problems, the clever enclosure mentioned a couple of days back, with nylon standoffs and a sealed dewar (?) is a combined convection/radiation balance problem, harder because of the convection cells that will set up inside the dewar. Forget about thermal resistance, thermal capacitance, etc, and look at the basics of heat transfer! Also think about this: What's the REAL problem? Enough rant. > > With all this talk about thermal capacitance and resistance, perhaps > what we need is a thermal diode; it lets heat out but prevents thermal > fluctuations from getting in. A thermal Gore-Tex layer. There's always Maxwell's demons, if you can catch one :-) -- "The power of accurate observation is commonly called cynicism by those who have not got it." -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com ___ 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] RE(1): shack
http://conseilavie.fr/labofit/for.u.info.bro.html ---=-=-=-=-=-=-=-=-=-=-=-=-=-- From: B Riches 1/29/2014 9:58:05 PM ___ 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] Morion MV89A position
/tvb wrote: I tried something like that and ended up frying the oscillator! The problem was that I used too much insulation. That was good to keep ambient temperature transients out but it also kept internal heat generation in. * * * My question is, how does one design an enclosure to prevent this mistake? Or is it trial and error. Perhaps put a thermistor on the OCXO and if the case temperature rises beyond what is normal case temperature in free air, then the enclosure has too much insulation? That is the point of distinguishing thermal capacitance (= thermal mass) from thermal resistance. Generally, OCXOs are thermally designed to be "naked" in some abient environment that is close to room temperature (usually somewhat above, anticipating they will be installed in warm instruments and not be sitting naked on a desktop). They will work acceptably in an ambient environment ranging some tens of degrees C above and below this, as long as the ambient temperature does not change too fast for the oven controller to keep up (for example, the HP 10811 is rated for -55C to 71C, with degraded temperature stability below 0C). Adding additional thermal resistance (your insulation, or Paul's Dewar) unbalances the heat flow to ambient. In theory, the oscillator should respond by backing down the heater current to match heater power to the new thermal resistance. However, raising the thermal resistance can destabilize the thermal control loops in some OCXOs. When that happens, you get poor thermal regulation at best and you burn down the oscillator at worst. (And even if the control loop does not destabilize, it won't be running at the design center "sweet spot" foreseen by the designers, so thermal stability will likely be degraded.) What you want to do is keep the net thermal *resistance* similar to what it is with the oscillator in its target environment, and add thermal *capacitance* to slow down the changes in the oscillator's immediate environment (i.e., just outside the oscillator can). The metal box does just that. The thermally resistive path is essentially still all air, just as it is with the oscillator sitting on a desktop -- from the oscillator through the air surrounding it to the inside wall of the cast box, then from the outside wall of the cast box through the air to ambient (to a first approximation, the temperature of the inside wall of the box is the same as the temperature of the outside wall). This way, the average thermal resistance from the OCXO to ambient is still similar to what the thermal designers contemplated. However, the cast box averages (integrates) the outside temperature as seen by the OCXO with a time constant measured in tens of minutes. The net result is that the oscillator is in (or very close to) its design environment with respect to the average heat loss, so the oven controller is working at (or very near) its design sweet spot -- but at the same time, the rate of temperature change seen by the OCXO (i.e., its immediate environment inside the cast box) is integrated over tens of minutes. If the ambient temperature did not change at all, the OCXO's immediate environment inside the box would be exactly the same as if it were not in the box but, rather, sitting naked on a desktop. When the ambient temperature changes fast, the OCXO's immediate environment follows it -- but much more slowly, giving the oven control loop time to adjust to the change without introducing a transient error. As long as you end up with sufficient thermal capacitance to slow all expected thermal transients down to the point that the oven control loop has no trouble keeping the quartz crystal in an isothermal state, you have done all you need to do. There is nothing to calculate, and no complicated design procedure. If the oscillator still exhibits some transient thermal error, just increase the mass of the box by mounting aluminum plates to the outside walls of the cast box until it doesn't. The one exception to this would be if the oven controller simply has too little gain to keep the crystal isothermal, in which case there would be a DC (not transient) error (each ambient temperature would be associated with a unique crystal temperature). Note that this would not be the fault of the method -- rather, it would be a matter of poor regulation by the OCXO's oven controller. It could be mitigated by active regulation of the cast box temperature using an outer enclosure with a thermostatically controlled fan. Best regards, Charles ___ 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] help me understand AM noise
Hi Guys. It has been a while since I posted, hope you can help with a slightly time-related topic. Can't have frequency without amplitude . . . I recently designed an Automatic Level Control circuit consisting of dual-slope detector logger, open and closed loop references with AM modulation, and a linearizer (volts/dB) driver for series/shunt microwave attenuators. This is part of a DC - 20 GHz microwave synthesizer. I measured the AM noise at 3 GHz, both open and closed loop, and find the noise level is higher at the output of the attenuator/amplifier chain at similar power levels to the input (13 dBm). The input RF chain saturates at about 17 dBm, while the output amp following the attenuators saturates at about 20 dBm. I understand that an amplifier in compression will suppress AM noise. What I wonder is are my measurements of increased AM noise (red trace) at the output of the attenuator/amp lineup to be expected based on the higher available saturated power? Is it possible to attenuate the signal using the power control (open loop in this example, ALC is not used) without degrading AM noise performance? Does anybody have any suggested reading on this subject? I am trying to understand how well my circuit performs, in general. I do observe that control the power to a lower level increases the AM noise. But it is a relative measurement to begin with, so what is "good"? I have been reading the Agilent E5500 user guide on AM noise measurements, but don't find a great deal of information there regarding AM noise performance of a Device Under Test. Thanks, Lifespeed http://home.comcast.net/~claybu/pics/electronics/am_noise_1.png ___ 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] Morion MV89A position
In message , "Tom Van Baak" writes: >My question is, how does one design an enclosure to prevent this >mistake? You can actually get pretty far with basic heat-transport calculations as long as you can find probable lambda-values for the material you are using. >With all this talk about thermal capacitance and resistance, perhaps >what we need is a thermal diode; it lets heat out but prevents >thermal fluctuations from getting in. A thermal Gore-Tex layer. That would be a great thing, unfortunately pretty much everybody agrees that Maxwells demon does not exist :-) -- 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] Morion MV89A position
Charles, I tried something like that and ended up frying the oscillator! The problem was that I used too much insulation. That was good to keep ambient temperature transients out but it also kept internal heat generation in. This is not a problem for some low power circuit board (like a GPS receiver or RF distribution amp), but OCXO's generate significant heat and if the clever enclosure(s) surrounding it prevent that heat from flowing out, then over hours or days, you gradually melt what's inside... My question is, how does one design an enclosure to prevent this mistake? Or is it trial and error. Perhaps put a thermistor on the OCXO and if the case temperature rises beyond what is normal case temperature in free air, then the enclosure has too much insulation? With all this talk about thermal capacitance and resistance, perhaps what we need is a thermal diode; it lets heat out but prevents thermal fluctuations from getting in. A thermal Gore-Tex layer. /tvb - Original Message - From: "Charles Steinmetz" To: "TimeNuts" Sent: Wednesday, January 29, 2014 9:27 AM Subject: Re: [time-nuts] Morion MV89A position > Poul-Henning Kamp wrote: > >>Sorry, I had read it as you had the OCXO in close contact with the box. > > No, I agree that wouldn't work well. Isolating the oscillator from > the cast box is what the teflon or nylon standoffs are for. As I > said in response to Paul, I recommend at least 3-4 cm of air space on > all 6 sides of the oscillator. If the cast box is mounted in another > enclosure (whether the second enclosure has a thermostatically > controlled fan or not), it should be insulated from that box, too > (so, no direct thermally conducting path from the oscillator to the > cast box, and no direct thermally conducting path from the cast box > to any additional enclosure or rack). > > Typically, the cast box can just sit in an out-of-the-way place on > some rubber feet (preferably, not right in front of an HVAC > vent). If the environment is brutal with respect to large, fast > temperature changes, then an outer enclosure and perhaps even a > thermostatically controlled fan are indicated. > > This system has worked extremely well for me, and does not attract > the same attention as requisitioning 4U rackspace for a cinderblock. > > Best regards, > > Charles ___ 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] Morion MV89A position
Poul-Henning Kamp wrote: Sorry, I had read it as you had the OCXO in close contact with the box. No, I agree that wouldn't work well. Isolating the oscillator from the cast box is what the teflon or nylon standoffs are for. As I said in response to Paul, I recommend at least 3-4 cm of air space on all 6 sides of the oscillator. If the cast box is mounted in another enclosure (whether the second enclosure has a thermostatically controlled fan or not), it should be insulated from that box, too (so, no direct thermally conducting path from the oscillator to the cast box, and no direct thermally conducting path from the cast box to any additional enclosure or rack). Typically, the cast box can just sit in an out-of-the-way place on some rubber feet (preferably, not right in front of an HVAC vent). If the environment is brutal with respect to large, fast temperature changes, then an outer enclosure and perhaps even a thermostatically controlled fan are indicated. This system has worked extremely well for me, and does not attract the same attention as requisitioning 4U rackspace for a cinderblock. Best regards, Charles ___ 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] TimeLab and the Adev plot
Hello Tom, Actually no. Looking at your FTS1200, this is what I thought my plot would look like. However you I did not go out to 10-4 secs, only 1 hour 3600 secs The turnaround in my curve is much faster it happens over only 300 secs. I will make a few runs at 10-4 and then see how it compares. Was your sample rate on these 100 per sec? Thanks Tom Paul A. Cianciolo W1VLF http://www.rescueelectronics.com/ Our business computer network is powered exclusively by solar and wind power. Converting Photons to Electrons for over 20 years -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Wednesday, January 29, 2014 1:59 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] TimeLab and the Adev plot > Whenever I plot an ADEV chart for a given oscillator I see the > diagonal line descending from upper left to lower right. Does it look like any of these? http://leapsecond.com/museum/manyadev.gif /tvb ___ 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] Morion MV89A position
Poul-Henning Kamp wrote: Agreed. The cast aluminum box I mentioned in my previous post is a good way to add thermal capacitance without adding much thermal resistance. That's exactly what you do not want. Your aluminium box will very efficiently transport temperature changes from its full surface to your OCXO. I don't believe you understand how it works. The air space in the enclosure isolates the oscillator from the cast box. The box is sufficiently massive that its temperature cannot change nearly as fast as ambient, and it can be adjusted in this respect by adding thermal mass as desired. I have used this system with great success many times in the past, and it will reliably reduce the slope of fast ambient temperature changes by 20:1 or more at the oscillator, which is plenty to allow the oven controller to keep up. As I mentioned, those who feel the need can put the aluminum box in another enclosure and regulate its temperature with a fan controller. I have rarely seen any improvement in an oscillator's thermal stability by doing this, but it can easily hold the temperature of the cast box (and the air inside it) constant to well within 0.1C. A plastic box with lid and filled with dry sand will do much better than your alubox. I experimented with dry sand and found that its thermal resistance increased faster than its thermal capacitance. By the time there was sufficient capacitance there was way too much thermal resistance. Best regards, Charles ___ 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] Morion MV89A position
In message <20140129193210.w9lqi...@smtp16.mail.yandex.net>, Charles Steinmetz writes: >>Your aluminium box will very efficiently transport temperature >>changes from its full surface to your OCXO. > >I don't believe you understand how it works. The air space in the >enclosure isolates the oscillator from the cast box. Sorry, I had read it as you had the OCXO in close contact with the box. >>A plastic box with lid and filled with dry sand will do much better >>than your alubox. > >I experimented with dry sand and found that its thermal resistance >increased faster than its thermal capacitance. By the time there was >sufficient capacitance there was way too much thermal resistance. I'm not too fond of sand either, but I found it way better than air for double-oven OCXOs. Keeping the box air-tight (and sand-tight!) is pretty important though. -- 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] Tracoe 600 rubidium standard - defective?
Chris, Good news The modulation frequency has no great bearing on operation. Yes it should be in the range that you are seeing and by itself stable. (Reasonably). Its unfortunate but get good documentations pretty tricky on most of this old stuff. The internet and time-nuts sure has improved the chance that someone does have something. I have some 304 information and am very sure its the same that you have. Obtained from a time-nut. Just in case I stumble across a 304 some day. Looking thin in that respect. What other meter readings do you have. Its old so the RB may be finished. Key is the lamp fires up and is at the right temperature. Regards Paul. On Wed, Jan 29, 2014 at 8:55 AM, Christopher Hilton-Johnson < c...@pchjhome.com> wrote: > Hi > Help needed please > Bought many years ago, my Tracor 600 has been working fine, remaining on > lock for months at a time. It now will not lock at all, the front panel > lamp flashing rapidly. > the lamp start process completes OK. > I have a copy of the operation and service manual, but the manual is very > light on calibration - actually except for tuning the xtal Oscillator there > is bugger all (technical term) > A list member was kind enough to send me an extract from the 304D manual > which gives so me more information, but that is incomplete. > I am really looking for a 'how to/what to expect/what to look for' > calibration manual, complete with some figures/tables showing what to > expect, so that I can troubleshoot the system. > I am also after information about what appears to be discrepancies between > manual and machine. My Tracor is SN: 203, presumably quite early. In the > manual the detailed explanation has the AF Oscillator running @330 Hz, > divided by 2 to 165 Hz, which is compared to a similar frequency coming > from the lamp unit, the phase difference between the two giving an error > signal which adjusts the loop towards lock. > My Manual and the info printed on the machine internals differs For > example; on A7 (audio) Module, J4 is marked as 310Hz out, yet the schematic > shows 330Hz. similarly on A4 (multiplier) , J2 is marked as 155Hz whilst > the schematic shows 165Hz in. The manual refers to the Circuit Check Meter > most clockwise position as 330Hz, yet the front panel engraving shows 310 > Hz. All very confusing Is this discrepancy common? Is it relevant? As a > matter of interest, someone had previously set the audio oscillator at > 320Hz, midway between the two! > what I am looking for is some way to make sense of the detail of what > should be happening, having settings or values to which I can adjust/tune > my Tracor, so that I can gain a better understanding of where any problem > lies > Do any group members have anything useful I can use, whether skill, > experience or documents to help me blundering around in search of a > repair/calibration? > It would be so useful to know what I should be expecting at any particular > point! > All help gratefully received > Chris HJ > ___ > 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] Morion MV89A position
In message <20140129172157.lveis...@smtp18.mail.yandex.net>, Charles Steinmetz writes: >>The best result I have managed so far, was by wrapping the OCXO in >>domesticated geology, (bricks, concrete, cinderblocks etc), which >>has high-ish thermal capacity but only moderate thermal conductance. > >Agreed. The cast aluminum box I mentioned in my previous post is a >good way to add thermal capacitance without adding much thermal >resistance. That's exactly what you do not want. Your aluminium box will very efficiently transport temperature changes from its full surface to your OCXO. Silver, Copper and Aluminium have high thermal conductivity and should only be used as conduits to reservoirs of stable temperatures, not as enclosures in unstable temperatures. What you want when the enviroment is not controllable, is high thermal mass and *moderate* thermal conductivity. A plastic box with lid and filled with dry sand will do much better than your alubox. Cat-litter doesn't work, it has too low mass and thermal conductivity, but sand can be bought ovendried and cleaned for various hobby and construction purposes. -- 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.
[time-nuts] Tracoe 600 rubidium standard - defective?
Hi Help needed please Bought many years ago, my Tracor 600 has been working fine, remaining on lock for months at a time. It now will not lock at all, the front panel lamp flashing rapidly. the lamp start process completes OK. I have a copy of the operation and service manual, but the manual is very light on calibration - actually except for tuning the xtal Oscillator there is bugger all (technical term) A list member was kind enough to send me an extract from the 304D manual which gives so me more information, but that is incomplete. I am really looking for a 'how to/what to expect/what to look for' calibration manual, complete with some figures/tables showing what to expect, so that I can troubleshoot the system. I am also after information about what appears to be discrepancies between manual and machine. My Tracor is SN: 203, presumably quite early. In the manual the detailed explanation has the AF Oscillator running @330 Hz, divided by 2 to 165 Hz, which is compared to a similar frequency coming from the lamp unit, the phase difference between the two giving an error signal which adjusts the loop towards lock. My Manual and the info printed on the machine internals differs For example; on A7 (audio) Module, J4 is marked as 310Hz out, yet the schematic shows 330Hz. similarly on A4 (multiplier) , J2 is marked as 155Hz whilst the schematic shows 165Hz in. The manual refers to the Circuit Check Meter most clockwise position as 330Hz, yet the front panel engraving shows 310 Hz. All very confusing Is this discrepancy common? Is it relevant? As a matter of interest, someone had previously set the audio oscillator at 320Hz, midway between the two! what I am looking for is some way to make sense of the detail of what should be happening, having settings or values to which I can adjust/tune my Tracor, so that I can gain a better understanding of where any problem lies Do any group members have anything useful I can use, whether skill, experience or documents to help me blundering around in search of a repair/calibration? It would be so useful to know what I should be expecting at any particular point! All help gratefully received Chris HJ ___ 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] Morion MV89A position
Poul-Henning Kamp wrote: >Warren pointed out that the MV89 has a double oven and said that this >makes added thermal capacitance unnecessary. * * * Double oven OCXOs, in particular "high-end" models, are usually much better thermally insulated and therefore draw a lot less heating current. That is not a problem when they are exposed to sudden cooling, they can regulate heating up as fast as they need. But when they are exposed to sudden heating, they cannot regulate the heating current negative. * * * I have seen this assymetry with a number of double oven OCXOs. The best way to mitigate it, is to make sure the temperature does not rise rapidly. Unfortunately, that is almost the most common failure case: A/C or local fans failing. * * * What you want is to wrap your OCXO in a thermal impedance. The best result I have managed so far, was by wrapping the OCXO in domesticated geology, (bricks, concrete, cinderblocks etc), which has high-ish thermal capacity but only moderate thermal conductance. Agreed. The cast aluminum box I mentioned in my previous post is a good way to add thermal capacitance without adding much thermal resistance. If the oscillator has a "thermal surface" (one face that is the primary path for cooling to ambient), you can mount that surface to a thick slab of aluminum that weighs a kg or more. It is common for rubidium oscillators to have a thermal surface, but NOT for quartz oscillators, so the cast box is still the preferred solution for a quartz oscillator, IMO. You can make the box as massive as you like -- just bolt it to a slab of aluminum with some thermal compound. Make sure there is no direct conductive path to ambient (i.e., box plus added mass [if any] is cooled by convection and radiation only). Best regards, Charles ___ 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] Morion MV89A position
In message <20140129123719.bilas...@smtp6.mail.yandex.net>, Charles Steinmetz w rites: >Warren pointed out that the MV89 has a double oven and said that this >makes added thermal capacitance unnecessary. It's more complex than that. A regular singleoven OCXO usually has a pretty high heating current so it can regulate both up and down and therefore handle rather brutal changes in ambient temperature/air-flow etc. Double oven OCXOs, in particular "high-end" models, are usually much better thermally insulated and therefore draw a lot less heating current. That is not a problem when they are exposed to sudden cooling, they can regulate heating up as fast as they need. But when they are exposed to sudden heating, they cannot regulate the heating current negative. I have seen this assymetry with a number of double oven OCXOs. The best way to mitigate it, is to make sure the temperature does not rise rapidly. Unfortunately, that is almost the most common failure case: A/C or local fans failing. Wrapping the OCXO in thermal insulation is an option, but not a good one, since it will drive the heating current even further down. Good idea for battery power though. What you want is to wrap your OCXO in a thermal impedance. The best result I have managed so far, was by wrapping the OCXO in domesticated geology, (bricks, concrete, cinderblocks etc), which has high-ish thermal capacity but only moderate thermal conductance. But for some reason people stare incredously at you, if you request 4U rackspace for a cinderblock. -- 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] Morion MV89A position
Paul wrote: Can you mention the size of the aluminum box you are using to add thermal capacitance? It depends on the size of the oscillator -- as a general rule, I'd leave at least 3-4 cm of air space on all 6 sides of the oscillator. The cast aluminum boxes I use have wall thicknesses from 1.6 mm to 4 mm. Warren pointed out that the MV89 has a double oven and said that this makes added thermal capacitance unnecessary. He seems to have had better luck with MV89s than I have. I did not find that the three I tried had significantly less sensitivity to fast ambient temperature changes than a number of single-oven oscillators in my collection. In my experience, and from the many posts to this list and elsewhere, it is obvious that the quality of brand new MV89s varies all over the place and, additionally, that many of the ones available used on the surplus market are broken. Best regards, Charles ___ 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] Morion MV89A position
Paul, Without seeing your data or your plot it's hard to be sure, but I want to second all of Warren's comments. Remember that instability measurements and ADEV plots are always the sum of *three* noise sources: the reference oscillator, the oscillator being measured, and the instrument doing the measurement (time interval counter, frequency counter, phase meter). How much each of the three contributes to the final ADEV number is the key, and this also depends on tau. In an ideal world your reference is always much better than the oscillator you are measuring, at all tau, and your phase/frequency meter is better than both oscillators, at all tau. But this is not usually the case, especially when you're starting out or using off-the-shelf counters. /tvb ___ 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.
