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??
In message [EMAIL PROTECTED], Bernd T-Online writes: Jeff Mock wrote: I can confirm Rick's statement, that there is no noticable effect of aging on the turnover temperature (TOT). 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 ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | 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] 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??
Bernd T-Online [EMAIL PROTECTED] wrote: 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 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. Tim. ___ 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 escribió: 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. At least one model is the 2804A. Not much info about it in the Agilent web site, but according to the 1986 catalog 'the temperature sensor is a quartz crystal whose precise angle of cut gives an stable and repeatable relationship between the resonant frequency and temperature'. But also is mentioned there that 'The only adjustment necessary to remove effects of thermal history on the sensor is a simple ice point or triple point calibration adjustment using the front panel thumbwheel switches'. Since the ice-point calibration would only be able to remove an offset, I understand that this is the manual removal of frequency drift effects. Of course, I suppose that the dritft would be small compared with the quartz temperature coefficient. 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. Best regards, Javier, EA1CRB ___ 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 [EMAIL PROTECTED] wrote: Tim Shoppa escribi?: 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. At least one model is the 2804A. Not much info about it in the Agilent web site, but according to the 1986 catalog 'the temperature sensor is a quartz crystal whose precise angle of cut gives an stable and repeatable relationship between the resonant frequency and temperature'. But also is mentioned there that 'The only adjustment necessary to remove effects of thermal history on the sensor is a simple ice point or triple point calibration adjustment using the front panel thumbwheel switches'. Since the ice-point calibration would only be able to remove an offset, I understand that this is the manual removal of frequency drift effects. Of course, I suppose that the dritft would be small compared with the quartz temperature coefficient. 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. Very interesting, Javier. I'm guessing the 2804A was a 70's implementation if it had thumbwheels. Thanks for posting the details you found! The unit I remember was not digital in the readout sense - it worked like a Fluke differential voltmeter, where you dial in some big rotary switches until you get a null on an analog meter. I may be confusing a 60's era Fluke temperature probe with the HP probes though! Who else would've been building quartz temperature probes in the 60's? Fluke, Beckman, ??? And what cut crystal matches the need for a huge and mostly linear tempco? Tim. ___ 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??
DK1AG wrote: ... 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 Bernd, may you send me a picture of the connector? Direct email ik1odo at spin-it.com 73 - Marco IK1ODO / AI4YF ___ 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??
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bernd T-Online Sent: Sunday, December 09, 2007 8:44 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Super stable BVA Quartz resonators... BVA?? 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... See what current versus temperature looks like: http://www.ko4bb.com/Test_Equipment/HP10811-Current.png Didier KO4BB ___ 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??
Berndt I believe you are describing a Triax connector I found them through Trompeter but I believe they are sold by Farnell and RS Components in the UK. The same connector was used I think on some of the HP system digital voltmeters. Cheers de Alan G3NYK - Original Message - From: Bernd T-Online [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, December 09, 2007 2:21 PM Subject: 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. ___ 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??
Yes, but that doesn't account for this part of his request (emphasis added): It looks like a *smaller* version of a BNC connector, but the bayonet has three nipples instead of two. -Chuck Harris Alan Melia wrote: Berndt I believe you are describing a Triax connector I found them through Trompeter but I believe they are sold by Farnell and RS Components in the UK. The same connector was used I think on some of the HP system digital voltmeters. Cheers de Alan G3NYK ___ 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??
Yes, I know... I was only exposing it as an example of how the temperature coefficient can be quite higher compared with the aging effect even if the quartz crystal is not intended to be used as a temperature sensor :) Regards, Javier Bernd T-Online escribió: 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. ___ 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??
At 17.58 09/12/2007, Bernd wrote: Thanks, Marco. I have the unit in my QRL lab, so I can take a photo only by tomorrow. Ok, good. There are triax connectors with three and two bayonets around - ask Keithley... they have used both types. Or it may be something else, HI. 73 - Marco IK1ODO / AI4YF ___ 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] Little 3-bayonet connector
At 3:21 PM +0100 12/9/07, Bernd T-Online wrote: 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 Bernd, That is a real oddball connector. I encountered one inside a surplus trunk-mount Motorola car telephone made in the 1970s. The only submini bayonet connectors I find mentioned with Google are the Kings KM which is like the BSM which Tektronix used, and Google gives a photograph. It has two bayonet pins. Unfortunately, if no one makes it anymore, data will be hard to find, much less the actual connectors. -- --David Forbes, Tucson, AZ http://www.cathodecorner.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] BVA resonators
In the BVA device, it's not so much that the 'top is domed', but that the resonator is plano-convex. I stand to be corrected, but I believe plano-convex crystals are used in high quality oscillators because the shape leads to a lower level of spurious responses, hence fewer 'dips'. BVA (and QAS, which is a similar technology) devices have very low ageing, very high Q etc, partly because of the construction, and partly because of the processing skill of the manufacturer (a lot of the processing techniques are closely guarded secrets). The main applications for these devices lead from the very high Q properties of the construction, which gives the devices low ageing (handy for a spacecraft application), but also extremely good short-term stability. The 1s tau AV can be better than 1e-13. There are plenty of devices with low ageing and good long-term stability (Rb oscillators, for example), but short term stability is a very rare commodity. Some of the newer atomic sources (the Hydrogen Maser is a good example) exhibit very good short term stability, but if you don't have $200k to spare, you look for something else. A BVA or QAS device can be phase locked to a Cs source etc for long term correction, but the best short-term performance is still going to be as a stand-alone device, where it out-performs most other technologies. So who needs high short-term stability performance? Anyone making high performance OCXOs, that's who! If you are intending to measure the frequency vs temperature performance of a 1e-11 level OCXO, you won't know if the perturbations are temperature related or reference related without high short-term stability. Similarly, measuring ageing of a device with ageing spec better than 1e-9/year will be impossible on any time scaler shorter than months unless your reference is short-term stable to 1e-13. Murray ZL1BPU ___ 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.
[time-nuts] Triaxial Connectors
At one time I was really hot after getting some triaxial connectors, to use with an Austron 5 MHz distribution amplifier. Well, as with most of my projects, I managed to buy a whole bunch of connectors (found some on ebay and a bunch at a hamfest) and, as usual, never did anything with them. So, if you still need a triaxial connector I am sure I can help you out. 73 - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Arnold Tibus Sent: Sunday, December 09, 2007 4:16 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Super stable BVA Quartz resonators... BVA?? On Sun, 09 Dec 2007 15:21:46 +0100, Bernd T-Online wrote: 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 Bernd and the group, the system voltmeter hp 3437A does have this mentioned connector as I see on my old work horse, sure you mean the same. This connector is for double shielded separate isolated or twinax sym. cable as used for very low voltage signals (thus avoiding unwanted gnd loops). The inner coaxial connector is in fact of lower diameter, but the outside shell has the same size as the std. BNC, but instead having 3 guide pins/slots. Trompeter is one manufacturer, unfortunately I have to dig to find my spare connector in the bag with the manuf. type no on. HP does have a cable for RF-equipment Model 11172B with male on both sides. I add some pictures showing plug and connector. I hope it can help clarifying a bit. Kind regards, Arnold, DK2WT ___ 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??
Bernd T-Online wrote: 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. That problem was solved over a century ago in optical lens manufacture. If the two surfaces are spherical, then such decentering is equivalent to adding a wedge, which is easily removed by optical centering and edging techniques. Also other parameters become worse. For the BVA the manufacturability would also be much worse as it already is. Regards Bernd DK1AG Bruce ___ 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] HP662xA power supply calibration with prologix USB-GPIB
Slightly off topic: In case any of you have a HP662xA power supply, I have a C program that performs the calibration using the Prologix USB-GPIB adapter. Mail me if interested. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | 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] Super stable BVA Quartz resonators... BVA??
From: Bernd T-Online [EMAIL PROTECTED] Subject: Re: [time-nuts] Super stable BVA Quartz resonators... BVA?? Date: Sat, 08 Dec 2007 09:27:28 +0100 Message-ID: [EMAIL PROTECTED] 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. While I higly enjoy reading this thread and learning things as I read on, I notice that several fellow time-nuts have designer skills at advanced SC-level OCXOs. For those of you, what reading material is there to get better into depths with these issues? The only sufficiently indepth book I have is Gerber, Ballato Precision Frequency Control, Volume 1; Acoustic Resonators and Filters (I also got Volume II). 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] Super stable BVA Quartz resonators... BVA??
Bernd T-Online wrote: 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 Bernd Whilst traditional optical edging techniques can easily remove any wedge when both surfaces are convex, maintaining alignment of the lens axis with respect to the crystal axes is another matter, at least when using traditional surfacing techniques, with computer controlled surfacing techniques even this can be done. With a planoconvex lens bias polishing or an equivalent technique can be used to adjust the inclination of the plano surface with respect to the crystal axes and this alignment is maintained during edging leaving only axial thickness adjustments to be made. The etching process used to remove cracks and defects after mechanical polishing is anisotropic which may introduce further complications in maintaining alignment and shape. Bruce ___ 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.
