Re: [time-nuts] Thunderbolt stability and ambient temperature
Hi Tom, I do have such temperature chambers. I wil do the test with a 10544 and a 10811 over teh comming wekeend probably. Regards Bernd Neubig (DK1AG) __ AXTAL GmbH Co. KG www.axtal.com Tom Van Baak wrote: Does anyone on the list have access to a low temperature test chamber? It would be interesting to see how slowly a 10544 or 10811 warms up from that cold environment as compared to a more modern and compact E1938 or MTI or TBolt-style OCXO. ___ 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] What type of Crystal?
For an OCXO you can determine whether it is an AT, BT or SC cut crystal by looking at the frequency difference between warm-up and after. Jim wrote earlier, that his 10544 osc is sitting about 1.5KHz LOW at room temp and then increases in freq at warmup (OVEN temp rising). 1.5 kHz = 150 ppm @ 10 MHz. 1. A BT cut crystal has a second order tempco of approx. -4*10^-8 per K^2 with reference to the turn-over temperature. Assuming an oven temperature of around 85°C, makes a temp difference to room temp of abt. 60K: (60K)^2*(0.04ppm/K^2) = 144 ppm = 1.44 kHz. This matches closely to Jims measurement. 2. An AT cut crystal has a frequency vs. temperature response described by a 3rd order parabola with its symmetry point around 25°C~35°C. Without going into the math in detail: A cut angle with a UTP of 85°C has an offset at 85°C compared to 25°C of about -45 ppm. This is much less than Jim's observation, and the direction of the frequeency change is opposite to the observed one. 3. An SC-cut crystal also has a frequency vs. temperature response described by a 3rd order parabola with an inflection (symmetry) temperature of around 95°C. But the SC-cut f(T) response has a much flatter curvature than an AT-cut (see the HP magazine article cited earlier). An OCXO with an SC-cut crytal operating at 85°C shows about -18ppm offset at room temperature compared to the frequency at assumed TOP of 85°C. This is a much smaller amount than Jim's measurement. Therefore it is easy to conclude, that Jim's 10544 uses a BT-cut crystal. Best regards Bernd Neubig DK1AG __ AXTAL GmbH Co. KG www.axtal.com Ed Palmer schrieb: The recent discussion regarding the type of crystal in the HP 10544A brought this question to mind. We're always coming across unknown oscillators. Usually we can figure out the pinouts and voltages. Then we can measure stability, aging, etc. But are there any tricks to figure out what type of crystal is in the oscillator? How can you detect the differences between AT, BT, SC, etc? I think that AT crystals have a broader tuning range than SC and that when warming up AT crystals tend to overshoot the final frequency and fall back. Are these generalizations correct? Are there other tricks to help differentiate the crystal types? Ed ___ 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] What type of Crystal?
I am wondering why my post did not go through yesterday. Here it is again: For an OCXO you can determine whether it is an AT, BT or SC cut crystal by looking at the frequency difference between warm-up and after. Jim wrote earlier, that his 10544 osc is sitting about 1.5KHz LOW at room temp and then increases in freq at warmup (OVEN temp rising). 1.5 kHz = 150 ppm @ 10 MHz. 1. A BT cut crystal has a second order tempco of approx. -4*10^-8 per K^2 with reference to the turn-over temperature. Assuming an oven temperature of around 85°C, makes a temp difference to room temp of abt. 60K: (60K)^2*(0.04ppm/K^2) = 144 ppm = 1.44 kHz. This matches closely to Jims measurement. 2. An AT cut crystal has a frequency vs. temperature response described by a 3rd order parabola with its symmetry point around 25°C~35°C. Without going into the math in detail: A cut angle with a UTP of 85°C has an offset at 85°C compared to 25°C of about -45 ppm. This is much less than Jim's observation, and the direction of the frequeency change is opposite to the observed one. 3. An SC-cut crystal also has a frequency vs. temperature response described by a 3rd order parabola with an inflection (symmetry) temperature of around 95°C. But the SC-cut f(T) response has a much flatter curvature than an AT-cut (see the HP magazine article cited earlier). An OCXO with an SC-cut crytal operating at 85°C shows about -18ppm offset at room temperature compared to the frequency at assumed TOP of 85°C. This is a much smaller amount than Jim's measurement. Therefore it is easy to conclude, that Jim's 10544 uses a BT-cut crystal. Best regards Bernd Neubig DK1AG __ AXTAL GmbH Co. KG www.axtal.com Ed Palmer wrote: The recent discussion regarding the type of crystal in the HP 10544A brought this question to mind. We're always coming across unknown oscillators. Usually we can figure out the pinouts and voltages. Then we can measure stability, aging, etc. But are there any tricks to figure out what type of crystal is in the oscillator? How can you detect the differences between AT, BT, SC, etc? I think that AT crystals have a broader tuning range than SC and that when warming up AT crystals tend to overshoot the final frequency and fall back. Are these generalizations correct? Are there other tricks to help differentiate the crystal types? Ed ___ 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] Low frequency crystal
Robert Atkinson wrote: What's the lowest frequency crystal made? Anyone have any suggestions for an oscillator circuit? Hello Robert, you can find a suitable circuit in my 1979 publication in the VHF Communication magazine Design of crystal oscillator circuits. A free download of the paper is available on the AXTAL website www.axtal.com under Technical Notes / Technical Articles and Publications. The paper is lsited at the bottom of the table. Best regards Bernd DK1AG ___ 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] Close-in phase noise measurements
Shane wrote: Do you know much about the RS FSUP50? http://www2.rohde-schwarz.com/en/products/test_and_measurement/product_categ ories/spectrum_analysis/FSUP-%7C-Key_Facts-%7C-4-%7C-966.html This is a nice but expensive equipment. Nice: can do PN measurement by phase quadrature(where you need to oscillators) _and_ can doe cross-correlation measuremnts (where you need only one external oscillator). Expensive: depending on options abt US-$ 100,000 to $150,000 If you are ready to spend so much money, consider the Agilent Signal Source Analyser 5052B, who does use the cross-correlation method and has a lot of other features. But both of them are no ham gear yet... Regards Bernd Neubig __ AXTAL GmbH Co. KG Facility MOS Wasemweg 5 D-74821 Mosbach / Germany fon: +49 (6261) 939834 fax: +49 (6261) 939836 www.axtal.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.
Re: [time-nuts] HP10811 problem - wrong frequency
[EMAIL PROTECTED] wrote: i have a problem with my HP10811 ocxo. I connected it properly to 24V, 12V and to my counter to measure its frequency. The measured frequency is 10.887 MHz, but it should be 10MHz (also noted on the 10811). The oscillator has obviously jumped to the so-called B-mode of the SC-cut crystal. The C-Mode operation (3rd overtone) is enforced by a circuit consisting of two inductors and two capacitors which is connected between base and emitter of the oscillator transistor. Unfortunately I do not have the shematic in hands here, so I cannot tell you the element IDs. Maybe one of the elements suffered of excessive aging. I can give you more specific help tomorrow, when I am in my office. Best regards Bernd DK1AG _ AXTAL GmbH Co. KG Facility MOS Wasemweg 5 D-74821 Mosbach / Germany fon: +49 (6261) 939834 fax: +49 (6261) 939836 www.axtal.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.
Re: [time-nuts] Super stable BVA Quartz resonators... BVA??
Jeff Mock wrote: How does crystal aging look on a graph of temp versus frequency What does this graph look like as a crystal ages? Does the optimal operating temperature change over time, that is, does the graph tend to move left and right, or does aging tend to move the graph vertically (the optimal freq stays the same, but the optimal operating temperature changes as a result of aging). I can confirm Rick's statement, that there is no noticable effect of aging on the turnover temperature (TOT). Looking at it from physics standpoint, frequncy aging is mainly caused by minor changes of vibrating mass and/or by changes in elastic properties (both due to various mechanisms). See my earlier thrad on aging mechanisms. On the other hand, the turn-over temperature is primarily governed by the cut angle (in connection with the resonator shape etc.). Mass loading, i.e. changes of electrode mass, has also an infuence, but this is much weaker. Roughly stated: a change of the TOT by one degC may be caused by a variation of the mass loading by an amount eqivalent to a frequency change of n*1000 ppm or so. This means that usual long term aging of precision crystals of a few 100 ppb or even one or two ppm may cause changes of TOT in the range of mK or less, which is - much smaller than the accuracy of the determination of TOT - neglictable compared to the impact of the aging of thermistors and of the frequency determining capacitors and inductors of the sustaining oscillator stage Regards Bernd DK1AG ___ 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] Super stable BVA Quartz resonators... BVA??
Poul-Henning Kamp wrote: You got me wondering: How is the TOT determined ? Is it per unit or is it per batch ? How precisely does an OCXO hold the temperature on the TOT ? For crystals used in precision OCXO the TOT is measured and recorded per unit. There are two main methods: passive and active In the passive method the crystal is inserted in a test fixture and its frequency and other parameters are measured using a network analyzer (state of the art). The crystals with its test fixture is in a precision temperature chamber, whose temperature is varied in fine steps in the vicinity of the expected TOT. The TOT is then calculated by curve fitting of the f(T) data by using a 2nd or 3rd order curve fitting algorithm, depending on the temperature span. Accuracy and repeatability are in the range of a (few) tenth of a degC. In the active method the crystal is operating in its oven, whose temperature is varied over a certain interval. Evaluation of the TOT by similar curve fitting as above. Accuracy and reproducibility is about 1/100 degC or slightly better. The temperature accuracy and stability of an oven dpends strongly on its construction, and there are several orders of magnitude difference betewen a simple low-cost DIL14 size OCXO and a high-end OCXO with sub-ppb stability. THe electronic part of the temperature control is not the difficult task, the main issue is to have a UNIFORM temperature over all frequency determining components, which is accurate and stable - and uniformity needs physical size. Regarding stability over time, the most critical components are the temperature sensors, mostly thermistors. Regards Bernd DK1AG ___ 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] Super stable BVA Quartz resonators... BVA??
Tim Shoppa wrote: For a while, didn't HP sell temperature probes which were in fact quartz crystals? Oscillation frequency was converted by some simple electronics to a temperature, and at the time (60's?) they were exquisitely convenient for measuring way better than a tenth of a degree. Either the frequency drift was negligible or it was so slow that I don't remember any manual removal of frequency drift effects. I'm guessing the probe crystals were some special cut (don't know which!) which was fairly linear or at least monotonic over the measurement temperatures. I'm guessing that HP chose a cut which had a very large tempco such that tempco dominated over any frequency drift. They did indeed. This was the HP2801A, later followed by the HP2804A. It uses a so-called LC-cut (Linear Coefficient) quartz crystal sensor, which is a doubly rotated cut with ultra-linear frequency vs. temperature characteristic with a slope of 35.4 ppm/K. For more information see http://hparchive.com/Journals/HPJ-1965-03.pdf BTW: I proudly own a HP2801A plus two crystal sensor elements. However I cannot connect them to the instrument, because the 2801A has a special connector for it. It looks like a smaller version of a BNC connector, but the bayonet has three nipples instead of two. Does anyone on the list know what kind of connector that is and where to get the counterpart (plug)? Regards Bernd DK1AG ___ 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] Super stable BVA Quartz resonators... BVA??
Javier wrote: Anyway, a 10544 oscillator has a cold offset that can easily be of 1000Hz, so if at 80 deg. C the offset is zero, and at 25 deg. C the offset is 1000Hz, you easily have a rough 15Hz/deg C average tempco in that range - and the aging drift for this oscillator is quite less than that. The 10544A incorporates an AT cut crystal. The tempco is far away from being linear. From room temp to the oven temperature it follows a 3rd order parabola, which has its minimum at the oven temperature. This trun-over tempearture varies from unit to unit, which means that the slope of f(T) also changes form unit to unit. Not the best approach for measuring temperatures ;-) At the other hand, the current consumption of the 10544A decreases fairly linear with temperature, so this is a better (but rather slow) temperature sensor, which would even work without the quartz... Regards Bernd DK1AG ___ 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] Super stable BVA Quartz resonators... BVA??
Marco IK1ODO wrote: may you send me a picture of the connector? Direct email ik1odo at spin-it.com Thanks, Marco. I have the unit in my QRL lab, so I can take a photo only by tomorrow. Regards Bernd DK1AG ___ 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] Super stable BVA Quartz resonators... BVA??
Hal Murray wrote: Why is the top domed? I assume flat would be easier to manufacture. Why is it not symmetrical? If the top is domed, why not the bottom too? For a plano-parallel qaurtz resonator the diameter must be at least 60 times larger than the thickness, otherwise the vibration amplitude would be too high at the edges, and the suspension would damp teh vibration hence the Q would be lowered. For a 10 MHz 3rd overtone SC-cut you would need a crystal of 40 to 50 mm diameter! By making a convex contour, the vibration is trapped in the center of the plate, and therefore the Q keeps high (and other parameters improve also). Bi-convex contours are more difficult to manufacture, as it is required that the symmetry axis of the upper and lower contour must coincide. Also other parameters become worse. For the BVA the manufacturability would also be much worse as it already is. Regards Bernd DK1AG ___ 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] 53131A or 5370B
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Tom, Tom Clark, K3IO wrote: I have been a strong advocate for the 53131/2 counter since I first encountered in in 1993. Most of my applications are for a time-interval counter (TIC) measuring the time interval between an atomic clock and GPS (see my Timing for VLBI papers at [1]http://gpstime.com). The two reasons are 1. It is simple and cheap and reliable, especially for the casual user. 2. It has a simple RS-232 printer interface that is really easy to use. Rick Hambly used the 53131/2 simple interface to make his Tac32Plus (and Multi) software packages into an integrated TIC logging utility My question: is there a penalty in timing, if the GPIB bus is used for time interval measurement as compared to the RS-232 bus. This question may sound stupid, as I am do not write the test software in our lab by myself, but get it done. Best regards Bernd Neubig DK1AG __ AXTAL GmbH Co. KG Facility MOS Wasemweg 5 D-74821 Mosbach / Germany fon: +49 (6261) 939834 fax: +49 (6261) 939836 www.axtal.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.
Re: [time-nuts] Fury Interface Board: 5MHz needed?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi all, being more than 30 years in the Frequency Control business, I want to comment on what Hal Murray wrote: My first guess is that it's a backwards compatibility mess. Ages ago somebody made a part with a single ground pin and somebody used it in some telco gear and everybody has been using the same footprint ever since. If that's the case, I'd expect there would also be a variation with a second ground pin to get better performance. Look for example to the very popular Eurocase package CO 08, as used in the MTI 260 (and many OCXO from other manufaturers - like the AXIOM40 45 series of AXTAL). This package originated from a TCXO package, and was first used to make OCXO (as TCXO replacements) in the early seventies. The connection scheme for the 5 pins was given and included only one ground pin. Next generation in OCXO miniaturization (in Europe) was the 20x20 mm package CO15 (as AXIOM30 35), which has the similar legacy, i.e. the 5 pins were defined for TCXO, i.e. with one ground pin, and later (in the late 80's) used for OCXO. The next smaller THD OCXO was in the 4-pin DIL14 package (AXIOM20 25), and it's clear that the 4 pins do not allow 2 GND pins. Any additional pin means more cost - and as such special versions would run in much smaller quantities - the cost are even higher. And - the accuracy and stability requirements for those small OCXO was (and is) less stringent in most applications such as for telecomms. The cost situation changes, when it comes to SMD packages (like the 22x25 mm package CO 28 - AXIOM10). For those packages you can indeed find a few specs on the market, which have two separate ground terminals for oscillator and heater circuit. Such specs are written by people who know about the effects of ground loops. However I do not know any modern catalog or standard parts on the market with two ground terminals. In fact the impact on stability is mostly neglectable under stationary operation conditions with rather constant environmental temperature. For applications where temperature changes are an issue _and_ highest stability is required, there is no other way than having two separate grounds. Are they running temperature tests with the EFC pin open so they don't see any problem as the heater current changes? (or something like that) Indeed, many (if not most) OCXO manufacturers run OCXO temp tests (and aging tests with the EFC pin grounded. The undesired ground loop effect can be reduced if the connection is made very close to the pin, and if the inside connection to the PCB ground has low impedance. Regards Bernd DK1AG __ AXTAL GmbH Co. KG Facility MOS Wasemweg 5 D-74821 Mosbach / Germany fon: +49 (6261) 939834 fax: +49 (6261) 939836 www.axtal.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.
Re: [time-nuts] time-nuts Digest, Vol 40, Issue 8
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi, Burt I. Weiner wrote: Everything will multiply. Error, phase shift/jitter. to be precise: absolute error (in Hz) will multiply, relative error or deviation (in ppb or any 10^-xx) will remain constant. Regards Bernd DK1AG ___ 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] QCM
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi John, Neon John wrote: A somewhat related question. Can a quartz crystal be used as a pressure (actually medium to high vacuum) sensor? Specifically, over the range of perhaps 1 Torr to 1e-6 Torr. IOW, over about the same range as a thermocouple gauge. At first blush it would seem a natural application. Not knowing what the second blush is :-) First of all there would not be much frequency change compared to the undesired effects from temperature, aging, and probably hysteresis for a one Torr pressure difference, and the scale would not be logarithmic as desired by a vacuum meter. In principle such a sensor would work only, if you put the crystal into a box, which is sealed at a reference pressure, and a mechanical force proportional to the pressure difference is suitably applied to the crystal through a membrane. So such a sensor would be rather complex and would have very low sensitivity with a linear scale from 0 Torr to 1 Torr - which is probably not what you wanted to consider. Regards Bernd DK1AG www.qsl.net/dk1ag ___ 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] QCM
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Ulrich, Ulrich Bangert wrote: Has anyone of you personal experience with QCMs (Quarz Crystal Microbalances) and give me a recommendation on a) what surface coating is suggested if the aim is to measure small amounts of humidity in clean air You should use gold coated QCM b) where such crystals may be supplied from in small quantities through my company (AXTAL - www.axtal.com) c) or if anyone is aware of a ready to go humidity sensor based on QCM technology There are several test systems on the market, but none of them is really low cost. Best regards Bernd Neubig __ AXTAL GmbH Co. KG Facility MOS Wasemweg 5 D-74821 Mosbach / Germany fon: +49 (6261) 939834 fax: +49 (6261) 939836 www.axtal.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.
Re: [time-nuts] Crystal Ageing
Jeffrey Pawlan wrote: It was Rick who wrote about crystal aging. It is not predictable whether the crystal will go higher or go lower in frequency and there is no guarantee that it will age at a linear rate. The worst-case is when a crystal erratically jumps. Indeed, the observed crystal aging is a sum of a larger number of physical processes. - Some of them are stronger than others - some of them decay faster or slower than other others - many of them show a logarithmic frequency change over time - a few of them have the shape of an exponential decay. The usual approximation used to predict frequency aging - as used in MIL-PRF55310 - is df/f = f0 + a1*log(a2*t+1), where a1 can be understood as a measure of the strenght of aging, and 1/a2 is a kind of time constant, i.e. small a2 values stand for slowly aging processes and large ones for fast agers. A better approach to describe frequency aging would thus be a mathematical sum of several logarithmic terms as in the above equation. As nicely shown in John Vig's tutorial, you can easily get a reversal of the aging rate (i.e. a change from positive to negative aging or vice versa), if you simply superimpose a fast and weaker (positive) aging process with a slower but stronger negative aging process - see attached copy. O.K. you now can say: why not make aging prediction by mathematical fitting of a sum of logarithmic terms through the observed frequency data over time? Basically this would/could improve the degree of fitting, correct. BUT: There is a big leveraging effect, if you make a mathematical prediction over a long period of time from data taken over a relatively small time period. In other words: If you just vary one or a few data points by a very small amount (i.e. to eliminate jumps), the effect on the extrapolated curve is enormous. Just try it using EXCEL's solver ... I had published an example for that 10 years ago - see a copy of my paper Correlation of predicted and real aging behaviour on our website www.axtal.com. In that paper I used data from about 9 months of aging, and compared the predictions made from different time periods with the real aging. From my standpoint the MIL-PRF55310 method of prediction is just a standardized method to define how the aging numbers in a spec are verified in a reasonable time of 4 weeks, It does not say: This is how the crystal will age over decades There is much more to say, but I will stop here, hoping that this contribution gave some time nuts a better understanding - and may kill their firm believe into aging predictions ;-) Best regards Bernd Neubig DK1AG inline: aging_Vig.gif___ 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.
