[time-nuts] Question: would this antenna work with the Austron 2200 series?
Question: would this antenna work with the Austron 2200 series? Symmetricom TrueTime GPS Antenna 140-615 Downconverter Datum 140-6150 Outdoor Ebay item number 281109470283 -marki ___ 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] Answers to regulator choices comments
At higher (load) currents, thermal, and parasitic resistance effects are getting more prevalent, to the limits of monolithic IC technology. Why don't consider a more classical approach with external pass transistor (a much larger selection available), if a linear regulator is really necessary? Also look up the old Unitrode UCx83y family, for example... A mixed bag of IC regulator technologies were mentioned... the LDOs (usually with series p-device for positive voltage ones) are much more picky about load conditions, and tougher to stabilize, let alone working in parallel configurations. To equally share the load current, the paralleled regulators should tightly track each other over load, and ambient conditions... don't consider it to be guaranteed over all operating conditions. The 3 terminal regulators were designed for convenience, not highest performance. note: LM338 is not a LDO like LT1084 (as TI proudly classifies it) On 6/30/2013 7:19 AM, Perry Sandeen wrote: Wrote: If you are in the US (maybe elsewhere) you can request two free samples. That might work for projects on and two, but what about projects three and onward? Wrote: I suppose that the same philosophy [paralleled regulators] would apply to getting more power with a 7805 farm. It does however with the general output rating of 1 to 1.5 amps for each regulator it wouldn’t be very practical. It’s much cheaper and simpler to use ones in the 3 amp plus range. Wrote: A regulator needs to be specifically designed for parallel operation. If it's not designed that way you will have a very hard time with it. I’ve never heard of any three terminal regulator designed for parallel operation. I believe that all three terminal regulators use a pass transistor. When one uses them in parallel they need a slight resistance added to each pass transistor to prevent current hogging just as one had to do when paralleling power transistors in other high amperage circuits. Wrote: It may be a bit more complicated than that. You need some way to share the load and you also need to make sure things are stable. The TI/National data sheet doesn't show anything about paralleling regulators. The AD data sheet shows 2 ft of #18 wire between each regulator and the load. I'm not enough of an analog guru to reverse engineer that setup and figure out the stability constraints and transfer them to 78xx type devices. I stand corrected about the LM 1084 showing paralleled regulators. However the data sheet says it is pin compatible with the LM 317. So we get to the paralleled regulator circuits by a bit of a circuitous route. If we go to National Semiconductor Linear Brief 51 March 1981 titled “Add Kelvin Sensing and Parallel Capability To 3-Terminal Regulators” it shows how to parallel two or more three terminal LM 338 regulators. The stability problem is solved for us by the Nation Semiconductor engineers. The 2 ft. of #18 wire for each regulator provides the load balancing resistance needed. One could use an ordinary resistor instead if it had the value of 30 mili-ohms. The operation of all 3 terminal regulators are the same. The internal circuitry looks at the relationship between the output voltage and the *ground* terminal. As the data sheets show, if we change that relationship with resistor combinations we can manipulate the output voltage to our needs. For most low voltage applications one can usually find a three terminal regulator that will fit the current needs, My original point was that the LM 1084 [$14] IMNSHO is very expensive for what it does. By paralleling two far cheaper of the LM 338 family one gets a larger ampacity of 10 amps instead of 7.5 amps for $3 to $5 instead depending on one’s scrounging abilities. In the end you pays your money and you make your choices. Regards, Perrier ___ 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] wwvb 60 khz tuning fork crystals Some insights
I presume you used the regular 74HC04 or 74HCU04 inverter, not the 74HC14 Schmitt trigger input type?? If the '14 is actually used, that may explain the problems around setting the feedback biasing resistor value - you may be overriding the built-in hysteresis to get it in the linear region. Usually that R isn't very critical with regular crystals, but maybe tuning fork types need more gain, or, if it's actually a '14, the input impedance is probably lower than a regular gate, so it's loading the resonator. 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] looking for low-power system for gps ntp timekeeping
On Fri, 28 Jun 2013 11:28:44 +0200 folkert folk...@vanheusden.com wrote: It must be a system 5 watt, so probably an ARM system. It will only run ntpd so not much ram is required. It will have 10 (ntp-)clients so a very powerfull processor is not required. Get a board with a modern uC that has an ethernet interface and 32bit capture/compare unit, and a cheap, low power gps module and you get to 1W including all losses. eg: https://www.olimex.com/Products/ARM/ST/STM32-E407/ plus http://www.ebay.com/itm/Ublox-NEO-6M-GPS-Module-w-Antenna-For-Arduino-MWC-IMU-Multi-Rabbit-Flight-A100-/261165592580 As OS i would suggest using nuttx or similar to get all the ground work. I've also seen some uC ntp implementations, but i cannot find them currently. Oh.. and if you want to go the linux way and use a Raspberry Pi.. just dont! Use a Beaglebone black instead. It uses less power and is easier to deal with. Not to mention that you dont have all those USB related problems. There has been some discussion about using the BBB as an NTP server in the past weeks on this list. Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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] Answers to regulator choices comments
Hi If you want the regulators to share the load equally when paralleled, they need to be a bit different than a +/-5% LM317 Bob On Jun 30, 2013, at 12:19 AM, Perry Sandeen sandee...@yahoo.com wrote: Wrote: If you are in the US (maybe elsewhere) you can request two free samples. That might work for projects on and two, but what about projects three and onward? Wrote: I suppose that the same philosophy [paralleled regulators] would apply to getting more power with a 7805 farm. It does however with the general output rating of 1 to 1.5 amps for each regulator it wouldn’t be very practical. It’s much cheaper and simpler to use ones in the 3 amp plus range. Wrote: A regulator needs to be specifically designed for parallel operation. If it's not designed that way you will have a very hard time with it. I’ve never heard of any three terminal regulator designed for parallel operation. I believe that all three terminal regulators use a pass transistor. When one uses them in parallel they need a slight resistance added to each pass transistor to prevent current hogging just as one had to do when paralleling power transistors in other high amperage circuits. Wrote: It may be a bit more complicated than that. You need some way to share the load and you also need to make sure things are stable. The TI/National data sheet doesn't show anything about paralleling regulators. The AD data sheet shows 2 ft of #18 wire between each regulator and the load. I'm not enough of an analog guru to reverse engineer that setup and figure out the stability constraints and transfer them to 78xx type devices. I stand corrected about the LM 1084 showing paralleled regulators. However the data sheet says it is pin compatible with the LM 317. So we get to the paralleled regulator circuits by a bit of a circuitous route. If we go to National Semiconductor Linear Brief 51 March 1981 titled “Add Kelvin Sensing and Parallel Capability To 3-Terminal Regulators” it shows how to parallel two or more three terminal LM 338 regulators. The stability problem is solved for us by the Nation Semiconductor engineers. The 2 ft. of #18 wire for each regulator provides the load balancing resistance needed. One could use an ordinary resistor instead if it had the value of 30 mili-ohms. The operation of all 3 terminal regulators are the same. The internal circuitry looks at the relationship between the output voltage and the *ground* terminal. As the data sheets show, if we change that relationship with resistor combinations we can manipulate the output voltage to our needs. For most low voltage applications one can usually find a three terminal regulator that will fit the current needs, My original point was that the LM 1084 [$14] IMNSHO is very expensive for what it does. By paralleling two far cheaper of the LM 338 family one gets a larger ampacity of 10 amps instead of 7.5 amps for $3 to $5 instead depending on one’s scrounging abilities. In the end you pays your money and you make your choices. Regards, Perrier ___ 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] Regulator choices
On 6/30/13 7:43 AM, Charles P. Steinmetz wrote: A three-terminal regulator (3TR) comprises (i) a voltage reference, (ii) an error amp, and (iii) a current amplifier. There is no need to duplicate the voltage reference or the error amp just because you need more current. In fact, they can only lead to problems with current sharing and/or oscillation. If the need is simply more current, add an external pass device. It may not be quite as easy as piling on more 3TRs (i.e., it takes a little thought), but at the several-ampere level it will almost certainly be cheaper. In many cases, the design is already done -- there are hundreds, if not thousands, of example circuits in manufacturers' app notes, which are easily found on the Web. Unless you're looking for high efficiency or low dropout, an easy way is to use a 3 terminal (like LM317) driving an emitter follower of appropriate rating (finally, something to use those old 2n3055s you have laying around). If you're looking for high efficiency, you might look at the Cui 78V00 series. They're DC/DC switchers in 3 terminal configuration with a variety of current ratings. ___ 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] Quartz crystal aging and applied voltage
Moin, While looking at various crystal oscillator circuits and a paper on stability of quartz oscillators i stumbled over a small detail that doesn't seem to be mentioned anywhere, at least i couldnt find anything: All quartz crystals contain some amount of ions that move within the lattice over time. Good crystals are swept using an high electric field prior to sawing the crystal slabs. Most of the oscillator circuits out there place a small, but constant DC voltage on the crystal, which has the same effect on the ions as sweeping does, albeit much slower. But i couldn't find any resource on how this DC voltage affects aging of quartz crystals. Does anyone know any paper/book/webpage that has a discussion of this topic? Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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] Regulator choices
Maybe I read the original posting wrong but I think this thread has departed greatly from the original posting. What I thought the posting said: 1) The already present transformer can produce ~20 V DC unregulated at sufficient current. 2) The desire was to have a 12 V regulated at somewhat greater than 1 amp. Though it wasn't raised in the first posting. A clean, non-switching supply was desirable for the poster. Thus, it isn't a case of attaching one regulator in series with another Regards Brian On 6/30/2013 14:43, Charles P. Steinmetz wrote: A three-terminal regulator (3TR) comprises (i) a voltage reference, (ii) an error amp, and (iii) a current amplifier. There is no need to duplicate the voltage reference or the error amp just because you need more current. In fact, they can only lead to problems with current sharing and/or oscillation. If the need is simply more current, add an external pass device. It may not be quite as easy as piling on more 3TRs (i.e., it takes a little thought), but at the several-ampere level it will almost certainly be cheaper. In many cases, the design is already done -- there are hundreds, if not thousands, of example circuits in manufacturers' app notes, which are easily found on the Web. 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. - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5950 - Release Date: 06/29/13 - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5950 - Release Date: 06/29/13 ___ 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] looking for low-power system for gps ntp timekeeping
From: Attila Kinali [] Oh.. and if you want to go the linux way and use a Raspberry Pi.. just dont! Use a Beaglebone black instead. It uses less power and is easier to deal with. Not to mention that you dont have all those USB related problems. [] Attila Kinali === I've built three Raspberry Pi stratum-1 NTP servers: http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html one of which has both a Wi-Fi dongle and a DVB TV receiver stick attached, and on none of these have I seen any USB problems. I'm using a 5.25 V 2A power supply from ModMyPi.com. You can view the timekeeping accuracy here: http://www.satsignal.eu/mrtg/performance_ntp.php Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Regulator choices
On 6/30/13 8:48 AM, Brian Alsop wrote: Maybe I read the original posting wrong but I think this thread has departed greatly from the original posting. What I thought the posting said: 1) The already present transformer can produce ~20 V DC unregulated at sufficient current. 2) The desire was to have a 12 V regulated at somewhat greater than 1 amp. Though it wasn't raised in the first posting. A clean, non-switching supply was desirable for the poster. Thus, it isn't a case of attaching one regulator in series with another Then it comes back to how clean ___ 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] wwvb 60 khz tuning fork crystals Some insights
Ed strange no body and you sent it 3 days ago. On Thu, Jun 27, 2013 at 12:13 AM, ed breya e...@telight.com wrote: I presume you used the regular 74HC04 or 74HCU04 inverter, not the 74HC14 Schmitt trigger input type?? If the '14 is actually used, that may explain the problems around setting the feedback biasing resistor value - you may be overriding the built-in hysteresis to get it in the linear region. Usually that R isn't very critical with regular crystals, but maybe tuning fork types need more gain, or, if it's actually a '14, the input impedance is probably lower than a regular gate, so it's loading the resonator. Ed __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Regulator choices
Hi Brian, I also wanted to reduce the amount of power wasted through passive devices. As it turned out, though, I had more tolerance for heat waste than I had thought. But, the general discussion this has become is also good. Bob - AE6RV - Original Message - From: Brian Alsop als...@nc.rr.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: Sent: Sunday, June 30, 2013 10:48 AM Subject: Re: [time-nuts] Regulator choices Maybe I read the original posting wrong but I think this thread has departed greatly from the original posting. What I thought the posting said: 1) The already present transformer can produce ~20 V DC unregulated at sufficient current. 2) The desire was to have a 12 V regulated at somewhat greater than 1 amp. Though it wasn't raised in the first posting. A clean, non-switching supply was desirable for the poster. Thus, it isn't a case of attaching one regulator in series with another Regards Brian ___ 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] Quartz crystal aging and applied voltage
Hi Ummm…. e…. not so much. Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. There have been a series of papers on various influences on crystals. If the blank is an SC, it can be tuned by an applied DC voltage. Many precision parts have a DC short across the resonator for this reason. In that case, you would not see anything to drive an ion anyway. If you have electrodes on the crystal, diffusion of plating into the quartz will move far more material around than trapped ions. How much more depends a lot on the exact plating materials and plating process. Bob On Jun 30, 2013, at 11:47 AM, Attila Kinali att...@kinali.ch wrote: Moin, While looking at various crystal oscillator circuits and a paper on stability of quartz oscillators i stumbled over a small detail that doesn't seem to be mentioned anywhere, at least i couldnt find anything: All quartz crystals contain some amount of ions that move within the lattice over time. Good crystals are swept using an high electric field prior to sawing the crystal slabs. Most of the oscillator circuits out there place a small, but constant DC voltage on the crystal, which has the same effect on the ions as sweeping does, albeit much slower. But i couldn't find any resource on how this DC voltage affects aging of quartz crystals. Does anyone know any paper/book/webpage that has a discussion of this topic? Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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] Question: would this antenna work with the Austron 2200 series?
There is really no clue. You need spec details. Maybe I overlooked it but did not see them. The need is for a complete downconverter preamp and antenna. The down converter must produce a 75.42 IF for the 2200. Regards Paul WB8TSL On Sun, Jun 30, 2013 at 5:06 AM, Mark C. Stephens ma...@non-stop.com.auwrote: Question: would this antenna work with the Austron 2200 series? Symmetricom TrueTime GPS Antenna 140-615 Downconverter Datum 140-6150 Outdoor Ebay item number 281109470283 -marki ___ 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] looking for low-power system for gps ntp timekeeping
david-tay...@blueyonder.co.uk said: I've built three Raspberry Pi stratum-1 NTP servers: ... and on none of these have I seen any USB problems ... As I understand it, the problem with USB on the Raspberry Pi is that the new/second version left out the current limiting on the power to the USB connectors. So when you plug in a device, there will be a glitch on the 5V power rail as the empty filter caps get charged up. So if you don't plug things in, it should work OK. You might also get lucky if the caps on your devices are small or you have long USB cables or you have a solid power supply for your Raspberry Pi or ... -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Quartz crystal aging and applied voltage
On 6/30/2013 8:47 AM, Attila Kinali wrote: Most of the oscillator circuits out there place a small, but constant DC voltage on the crystal, which has the same effect on the ions as FWIW, the HP 10811 definitely does not do this (according to its designers) since the crystal is capacitively coupled. Furthermore, they added a 1 megohm resistor across the crystal to make sure it has no DC on it. I would be surprised if any precision oscillator applied DC to the crystal. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Quartz crystal aging and applied voltage
Hi Bob, On 06/30/2013 06:30 PM, Bob Camp wrote: Hi Ummm…. e…. not so much. Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. There have been a series of papers on various influences on crystals. If the blank is an SC, it can be tuned by an applied DC voltage. Many precision parts have a DC short across the resonator for this reason. In that case, you would not see anything to drive an ion anyway. NIST have been using this effect for precision phase modulations. I don't agree that swept crystal has not been talked about. It is mentioned all over the precision crystal papers, it's there if you look for it. It however does not make much sense to discuss it for us, since we usually deal with complete oscillators and only rarely work with single crystals, and in that case very rarely of the quality where swept crystals occurs. There is definitely more to it than sweeping the crystal. Thanks Bob for the extra insight. The way sweeping works, won't a number of additional runs help to re-melt the crystal and help ironing out the dislocations in the crystal? 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] Regulator choices
I believe the original problem was that the raw unregulated voltage may be marginally too high for a conventional three-terminal to take safely. I have often encountered this problem, which is due to the wide input range possible considering the worst-case line voltage tolerance, transformer regulation, transformer selection limits, and possible surge voltages. If you drop the voltage with extra stages or series devices, you may run out of headroom, but if you don't, then it may run dangerously close to the maximum input rating of the regulator. If adding to, or reusing existing power circuits, there's often already some degree of protection from MOVs or gas-tubes, but these are very coarse, so are unlikely to be effective. Whenever I run a three-terminal regulator from raw DC, I put in a series fuse or PTC, and an over-voltage clamp ahead of it to assure that the input rating will never be exceeded. Also, the load may need to be protected - it depends on its characteristics. If the raw voltage is too high, the first step is to add some series diodes that can drop it some - you just have to make sure there's enough remaining headroom at lowest line and maximum load, etc conditions. Be sure to bypass the regulator input with as much extra C as possible to stabilize it, and provide more filtering. In the other extreme, when high-line occurs, there should be a comfortable distance from the raw voltage to the input rating. Then, only transient protection should be needed - heavy zeners or transorb type devices should be enough. If facilities are available, it's best to do this design part empirically, with actual parts, variac, and curve tracer - you can put real conditions on the real stuff. I also always add the usual reverse-protection diode across (O-I) the regulator, even if this fault seems unlikely - I can't count the number of times I've accidentally shorted out the regulator input nodes during design and construction - this would normally take out the regulator if it has lots of output C (almost always). If the peak at high-line is too close to the input rating, then I use an amplified zener clamp, with a big bipolar transistor driven by a big zener of the proper voltage. Alternatively, a traditional SCR crowbar circuit could be used, but I prefer a more transparent, self-resetting solution. Depending on the particular application, my favorite, and the most durable version is the substrate style, where the supply is referenced to a chassis ground or board ground plane. For example, to protect a positive supply, a large PNP transistor is anchored directly to the chassis - I'm talking about using only power devices, like TO-220 and larger - with no isolation, to provide maximum cooling from the collector tab into the substrate (the collector lead should go to the supply common too). The emitter then goes to the +supply, and the zener (typically 1W size) goes from the base (K) to ground (A). A small resistance around a couple of hundred ohms from B-E will make sure it doesn't turn on unless needed. For a negative supply, an NPN would be used, etc. If the supply common is not the substrate, then the same circuit topology can be used, except that galvanic isolation from the transistor tab to the substrate will be needed. Cooling won't be quite as good, but since the circuit floats, either type transistor can be used for any polarity. This same type of circuit can of course be used to protect the load side - this is even easier since the voltage is usually fixed, and the regulator (even if failed) adds to the series impedance limiting the fault current. I also put a large reverse-protection clamp diode on any supply that is exposed to the outside world, or is within a multiple-supply environment, where a fault between any two is possible - during design or testing too, as above, even if unlikely in operation. The transistor SOA rating should be sufficient to trim the peaks during possible high-line and transient conditions, and clear the series fuse if necessary, depending on the situation. Bigger is better for this purpose. The degree of protection and complexity, of course, depend on the criticality of failure, and value of the load. Not much is needed for routine or low power circuits, but for very important stuff, these things can make it nearly indestructible from the powering perspective. Ed Bob Stewart wrote: I also wanted to reduce the amount of power wasted through passive devices. As it turned out, though, I had more tolerance for heat waste than I had thought. But, the general discussion this has become is also good. ___ 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] looking for low-power system for gps ntp timekeeping
From: Hal Murray [] As I understand it, the problem with USB on the Raspberry Pi is that the new/second version left out the current limiting on the power to the USB connectors. So when you plug in a device, there will be a glitch on the 5V power rail as the empty filter caps get charged up. So if you don't plug things in, it should work OK. You might also get lucky if the caps on your devices are small or you have long USB cables or you have a solid power supply for your Raspberry Pi or ... === I've heard that as well. The majority of my own usage has been with devices which are permanently attached, although the Wi-Fi dongle and TV receiver dongle I mentioned have been unplugged and re-plugged without issue. My PSU is well over the minimum spec. I wouldn't expect an NTP server to be having devices continually added and removed, either Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] wwvb 60 khz tuning fork crystals Some insights
If you're talking about the email processing, I think something's going on. It sometimes take two or even three tries to get one through, while the most recent one I just sent (about regulators) went OK the first time. Let's see if this one does. B BTW how do you guys get the thread to continue on from the current message? I have only been able to copy and paste parts into the new email, and that loses some of the links and formatting in some way. I don't think this is the cause of the email problem above, since it seems uncorrelated with any editing or whether I send a brand new topic. I'm using an old version of Eudora (7.1.0.9), if that matters. Ed Ed strange no body and you sent it 3 days ago. On Thu, Jun 27, 2013 at 12:13 AM, ed breya https://www.febo.com/cgi-bin/mailman/listinfo/time-nutseb at telight.com wrote: I presume you used the regular 74HC04 or 74HCU04 inverter, not the 74HC14 Schmitt trigger input type?? If the '14 is actually used, that may explain the problems around setting the feedback biasing resistor value - you may be overriding the built-in hysteresis to get it in the linear region. Usually that R isn't very critical with regular crystals, but maybe tuning fork types need more gain, or, if it's actually a '14, the input impedance is probably lower than a regular gate, so it's loading the resonator. 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] wwvb 60 khz tuning fork crystals Some insights
It's probably a software bug in the NSA monitoring system that keeps dropping some of the message content. :) - Original Message - From: ed breya e...@telight.com To: time-nuts@febo.com Sent: Sunday, June 30, 2013 3:05 PM Subject: Re: [time-nuts] wwvb 60 khz tuning fork crystals Some insights If you're talking about the email processing, I think something's going on. It sometimes take two or even three tries to get one through, while the most recent one I just sent (about regulators) went OK the first time. Let's see if this one does. B BTW how do you guys get the thread to continue on from the current message? I have only been able to copy and paste parts into the new email, and that loses some of the links and formatting in some way. I don't think this is the cause of the email problem above, since it seems uncorrelated with any editing or whether I send a brand new topic. I'm using an old version of Eudora (7.1.0.9), if that matters. Ed Ed strange no body and you sent it 3 days ago. On Thu, Jun 27, 2013 at 12:13 AM, ed breya https://www.febo.com/cgi-bin/mailman/listinfo/time-nutseb at telight.com wrote: I presume you used the regular 74HC04 or 74HCU04 inverter, not the 74HC14 Schmitt trigger input type?? If the '14 is actually used, that may explain the problems around setting the feedback biasing resistor value - you may be overriding the built-in hysteresis to get it in the linear region. Usually that R isn't very critical with regular crystals, but maybe tuning fork types need more gain, or, if it's actually a '14, the input impedance is probably lower than a regular gate, so it's loading the resonator. 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.
Re: [time-nuts] Regulator choices
I believe the original problem was that the raw unregulated voltage may be marginally too high for a conventional three-terminal to take safely Hi Ed, Not really. The voltage is in line with the product specs for a 7812 (35V max), as is the current I had projected (a bit over 1A). However, the voltage difference (20-12) times the current (assumed to be 1A) is not within the dissipation ability of a small free-air heat sink. When I hooked things up for a test, the 7812 immediately went into overheat and started reducing the output voltage to compensate. It would be OK (according to the datasheet) if I bolted it to the chassis, but at my original post, I had not worked out the actual current load through the device. And it turned out that the datasheet I was using for the OCXO had overstated the current draw by some 30%. After working out what my actual needs were, I compared that to what HP was heat-wasting in the 37203A PSU, and realized that my needs were smaller. The collective quickly convinced me that a switching/bucking device would be too noisy, so I've decided to use a 78S12CT, which is a TO-3 cased 12V regulator, to pull down the 20V I have available to me. So, essentially, I didn't know what I was doing, as I have never done this before. After understanding how to do this, I decided to get a TO-3 cased device, which will fit the heat sink available to me in the 37203A case I'm putting it in. For me, this has all been a good discussion. The one thing that is missing is how to quantify the heat sink needs for a linear regulator. Any thoughts? IOW, is there some way to project how many square inches of heat sink needed for X watts to dissipate? Bob - AE6RV - Original Message - From: ed breya e...@telight.com To: time-nuts@febo.com Cc: Sent: Sunday, June 30, 2013 1:47 PM Subject: Re: [time-nuts] Regulator choices I believe the original problem was that the raw unregulated voltage may be marginally too high for a conventional three-terminal to take safely. I have often encountered this problem, which is due to the wide input range possible considering the worst-case line voltage tolerance, transformer regulation, transformer selection limits, and possible surge voltages. If you drop the voltage with extra stages or series devices, you may run out of headroom, but if you don't, then it may run dangerously close to the maximum input rating of the regulator. If adding to, or reusing existing power circuits, there's often already some degree of protection from MOVs or gas-tubes, but these are very coarse, so are unlikely to be effective. ___ 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] Quartz crystal aging and applied voltage
On Sun, 30 Jun 2013 20:44:36 +0200 Magnus Danielson mag...@rubidium.dyndns.org wrote: Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. That would make the aging even more severe. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. Ok. From what i've read sofar, i thought that sweeping was mostly to improve aging. I don't agree that swept crystal has not been talked about. It is mentioned all over the precision crystal papers, it's there if you look for it. Yes, sweeping is meantioned a lot, but i have so far not found any mention of aging due to DC voltage on a crystal. It however does not make much sense to discuss it for us, since we usually deal with complete oscillators and only rarely work with single crystals, and in that case very rarely of the quality where swept crystals occurs. Well, i'd like to understand how crystal oscillators work, what their limits are and what has been done to push those limits. And sometimes weird questions pop into my mind :-) Bob, Rick, thanks for the insights. Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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] Regulator choices
On 6/30/13 12:35 PM, Bob Stewart wrote: I believe the original problem was that the raw unregulated voltage may be marginally too high for a conventional three-terminal to take safely Hi Ed, Not really. The voltage is in line with the product specs for a 7812 (35V max), as is the current I had projected (a bit over 1A). However, the voltage difference (20-12) times the current (assumed to be 1A) is not within the dissipation ability of a small free-air heat sink. When I hooked things up for a test, the 7812 immediately went into overheat and started reducing the output voltage to compensate. It would be OK (according to the datasheet) if I bolted it to the chassis, but at my original post, I had not worked out the actual current load through the device. And it turned out that the datasheet I was using for the OCXO had overstated the current draw by some 30%. After working out what my actual needs were, I compared that to what HP was heat-wasting in the 37203A PSU, and realized that my needs were smaller. The collective quickly convinced me that a switching/bucking device would be too noisy, so I've decided to use a 78S12CT, which is a TO-3 cased 12V regulator, to pull down the 20V I have available to me. So, essentially, I didn't know what I was doing, as I have never done this before. After understanding how to do this, I decided to get a TO-3 cased device, which will fit the heat sink available to me in the 37203A case I'm putting it in. For me, this has all been a good discussion. The one thing that is missing is how to quantify the heat sink needs for a linear regulator. Any thoughts? IOW, is there some way to project how many square inches of heat sink needed for X watts to dissipate? This is a tricky area. It depends (a lot) on the airflow over the surface. Check out the applications notes from heat sink manufacturers like Aavid Thermalloy (http://www.aavid.com) or Wakefield (http://www.wakefield-vette.com). You can probably find something that replicates your plain flat surface to work with. ___ 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] Regulator choices
b...@evoria.net said: The one thing that is missing is how to quantify the heat sink needs for a linear regulator. Any thoughts? IOW, is there some way to project how many square inches of heat sink needed for X watts to dissipate? In the simple minded case, you can add up the (series) resistance. The units are degrees/watt. Chips and heat sinks will have a parameter in the data sheet: often Theta something-or-other. Mumble, round up for the connection between the chip and heat sink. With fins-to-air, it depends on the velocity of air. With a fan, that might be a constant. If you are depending upon convection, it gets messy, aka nonlinear. (I think, but don't have a good URL.) If you are using the PC board rather than a heat sink, the key factor is the size of the copper plane that the chip is soldered to. National had several app-notes with numbers for various chunks of copper. With typical (digital) multilayer boards, you can also help a lot by using many vias to connect the small surface copper planelet to the ground plane(s) internal to the PCB. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping
On 30 Jun, 2013, at 08:50 , David J Taylor david-tay...@blueyonder.co.uk wrote: From: Attila Kinali [] Oh.. and if you want to go the linux way and use a Raspberry Pi.. just dont! Use a Beaglebone black instead. It uses less power and is easier to deal with. Not to mention that you dont have all those USB related problems. [] Attila Kinali === I've built three Raspberry Pi stratum-1 NTP servers: http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html one of which has both a Wi-Fi dongle and a DVB TV receiver stick attached, and on none of these have I seen any USB problems. I'm using a 5.25 V 2A power supply from ModMyPi.com. You can view the timekeeping accuracy here: http://www.satsignal.eu/mrtg/performance_ntp.php You aren't necessarily showing the part where the Raspberry Pi is a bit weak, though. How well do clients which receive their time via the USB ethernet interface do? The Beaglebone Black has about three advantages going for it in this application: - The ARM CPU is about twice as fast as the Raspberry Pi's for about the same power consumption (I'm not sure this is a particular advantage for NTP, however, so I won't count it). - The Ethernet MAC core is built into the SOIC, and tightly coupled to it, so packet traffic doesn't have to sit waiting for the USB scheduler to get around to doing something with it. - The Ethernet MAC core also provides fairly good, complete IEEE1588 support. This is not of direct use to NTP but does provide a way to calibrate the software timestamps which NTP produces and consumes to better match when the packets arrive from and are transmitted by the actual hardware. I.e. you can measure the typical difference between hardware and software inbound timestamps (measuring interrupt latency), and hardware and software outbound timestamps (measuring the processing time spent in the outbound network stack) for PTP UDP packets, and then use these results to improve the symmetry of software timestamps for NTP UDP packets. There is no way I know of to measure this without the IEEE 1588 support (and the outbound number in particular is often big enough to deserve correction). - The TI SOIC also has a hardware timestamp capture peripheral (look for eCap in the documentation) which can capture PPS edge times with single-digit-nanosecond accuracy. That's a couple of orders of magnitude better than interrupt sampling and eliminates the jitter of the latter measurements. For a $5-$10 difference in price for the board I think these are worth it. The RPI makes a fine, low-power replacement for Intel hardware for this, but the Beaglebone Black has the raw material to do significantly better at this than either of them. The only problem with the Beaglebone is that it is not as popular as the Raspberry Pi, so making use of the former is going to require one to do more work on one's own to take advantage of it. Dennis Ferguson ___ 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] Quartz crystal aging and applied voltage
Hi On Jun 30, 2013, at 2:44 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Hi Bob, On 06/30/2013 06:30 PM, Bob Camp wrote: Hi Ummm…. e…. not so much. Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. There have been a series of papers on various influences on crystals. If the blank is an SC, it can be tuned by an applied DC voltage. Many precision parts have a DC short across the resonator for this reason. In that case, you would not see anything to drive an ion anyway. NIST have been using this effect for precision phase modulations. I don't agree that swept crystal has not been talked about. It is mentioned all over the precision crystal papers, it's there if you look for it. It however does not make much sense to discuss it for us, since we usually deal with complete oscillators and only rarely work with single crystals, and in that case very rarely of the quality where swept crystals occurs. There is definitely more to it than sweeping the crystal. Thanks Bob for the extra insight. The way sweeping works, won't a number of additional runs help to re-melt the crystal and help ironing out the dislocations in the crystal? That's not the way it's done. One pass under bias, pull the ions to the edges. Cut off the edges. If you re-melt and re-grow the crystal you get a whole new batch of ions from the growing process. Bob 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. ___ 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] Quartz crystal aging and applied voltage
Hi On Jun 30, 2013, at 3:41 PM, Attila Kinali att...@kinali.ch wrote: On Sun, 30 Jun 2013 20:44:36 +0200 Magnus Danielson mag...@rubidium.dyndns.org wrote: Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. That would make the aging even more severe. Yes, swept quartz resonators tend to age more than an equivalent normal part. That assumes the normal part is made from high grade quartz. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. Ok. From what i've read sofar, i thought that sweeping was mostly to improve aging. I have never seen it used to improve aging. I don't agree that swept crystal has not been talked about. It is mentioned all over the precision crystal papers, it's there if you look for it. Yes, sweeping is meantioned a lot, but i have so far not found any mention of aging due to DC voltage on a crystal. It's not aging if it's a fixed bias. The easy way to have a fixed bias is to have zero volts on the resonator. Given that the effect is *very* small, any regulated bias in an oscillator should be fine. It however does not make much sense to discuss it for us, since we usually deal with complete oscillators and only rarely work with single crystals, and in that case very rarely of the quality where swept crystals occurs. Well, i'd like to understand how crystal oscillators work, what their limits are and what has been done to push those limits. And sometimes weird questions pop into my mind :-) Very little of what has been done or that could be done will be found in published papers …. Bob Bob, Rick, thanks for the insights. Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown ___ 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] Quartz crystal aging and applied voltage
Remember when WWII arrived, crystals were of poor quality and not in great supply. The quartz crystal materials were all imported from South America and contained impurities. They had the nasty habit of abruptly changing frequency or drifting. They also stopped oscillating when humidity got high. Imagine yourself in the jungle calling for support during WWII and the transmitter goes dead due to the crystal. Something had to be done. This was solved quickly by growing pure crystals and developing the manufacturing process to do so. We've come a long way baby. Regards Brian On 6/30/2013 23:04, Bob Camp wrote: Hi On Jun 30, 2013, at 2:44 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Hi Bob, On 06/30/2013 06:30 PM, Bob Camp wrote: Hi Ummm…. e…. not so much. Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. There have been a series of papers on various influences on crystals. If the blank is an SC, it can be tuned by an applied DC voltage. Many precision parts have a DC short across the resonator for this reason. In that case, you would not see anything to drive an ion anyway. NIST have been using this effect for precision phase modulations. I don't agree that swept crystal has not been talked about. It is mentioned all over the precision crystal papers, it's there if you look for it. It however does not make much sense to discuss it for us, since we usually deal with complete oscillators and only rarely work with single crystals, and in that case very rarely of the quality where swept crystals occurs. There is definitely more to it than sweeping the crystal. Thanks Bob for the extra insight. The way sweeping works, won't a number of additional runs help to re-melt the crystal and help ironing out the dislocations in the crystal? That's not the way it's done. One pass under bias, pull the ions to the edges. Cut off the edges. If you re-melt and re-grow the crystal you get a whole new batch of ions from the growing process. Bob 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. ___ 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. - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5951 - Release Date: 06/30/13 - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5951 - Release Date: 06/30/13 ___ 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] Quartz crystal aging and applied voltage
Hi U….. eer….. Natural quartz is great stuff for making resonators. In many ways it's better than synthetic quartz. About the only thing natural is worse for is radiation. Natural quartz comes from all over the world. Most of the US supply comes from / came from Arkansas. If anything natural quartz with it's thousands of years growing process is lower stress and lower aging stuff. The whole synthetic quartz industry grew up simply to supplement the limited supply natural quartz. Remember - the only natural you can use is going to be entirely either right handed or left handed. That limits the amount you can find. That's not a purity thing, it's simply the crystallography of the lump you happen to have. The fact that it's not pre-oriented makes it slightly more difficult to work with. The number of blanks per pound will always be higher with synthetic. The whole issue with good stuff like humidity and crystals stopping dead was related to a precess that did not etch the crystals adequately after they were lapped. There were a few other issues, but that was the main one. Any quartz that will work as a resonator isn't going to be chemicaly affected by much of anything short of hydrofluoric acid. Bob On Jun 30, 2013, at 7:14 PM, Brian Alsop als...@nc.rr.com wrote: Remember when WWII arrived, crystals were of poor quality and not in great supply. The quartz crystal materials were all imported from South America and contained impurities. They had the nasty habit of abruptly changing frequency or drifting. They also stopped oscillating when humidity got high. Imagine yourself in the jungle calling for support during WWII and the transmitter goes dead due to the crystal. Something had to be done. This was solved quickly by growing pure crystals and developing the manufacturing process to do so. We've come a long way baby. Regards Brian On 6/30/2013 23:04, Bob Camp wrote: Hi On Jun 30, 2013, at 2:44 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Hi Bob, On 06/30/2013 06:30 PM, Bob Camp wrote: Hi Ummm…. e…. not so much. Ions in the lattice are part of the crystal structure. When you move them by sweeping you put stress on the quartz. That stress may take a *long* time to relax out. Since there is now a defect in the lattice (where the ion was) the stress may be relieved by an ion moving back to that location. Quartz is swept to reduce it's radiation sensitivity. That's a big deal if you are going to put the oscillator in outer space or if you expect to need to use it when unexpected bright lights appear in the sky. Neither one is likely to be of interest in a typical basement lab. The levels involved also would drive you to radiation harden the rest of the oscillator circuit, not just the crystal. There have been a series of papers on various influences on crystals. If the blank is an SC, it can be tuned by an applied DC voltage. Many precision parts have a DC short across the resonator for this reason. In that case, you would not see anything to drive an ion anyway. NIST have been using this effect for precision phase modulations. I don't agree that swept crystal has not been talked about. It is mentioned all over the precision crystal papers, it's there if you look for it. It however does not make much sense to discuss it for us, since we usually deal with complete oscillators and only rarely work with single crystals, and in that case very rarely of the quality where swept crystals occurs. There is definitely more to it than sweeping the crystal. Thanks Bob for the extra insight. The way sweeping works, won't a number of additional runs help to re-melt the crystal and help ironing out the dislocations in the crystal? That's not the way it's done. One pass under bias, pull the ions to the edges. Cut off the edges. If you re-melt and re-grow the crystal you get a whole new batch of ions from the growing process. Bob 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. ___ 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. - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5951 - Release Date: 06/30/13 - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5951 - Release Date: 06/30/13 ___ 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
[time-nuts] [OT] a different sort of time-nut
http://www.lawoftime.org The 13 Moon / 28-day calendar (synchronometer) is the key that allows us access to the vast realm of the synchronic order ... This is a Galactic timing program that also serves as a master synchronization matrix that any other calendar or numerical system can be plugged into. Hmm. What are the pinouts on those plugs? Do they use leap seconds to synchronize galaxies, or do they have a more elegant method? When you think about it, though, many of us are doing our best to synchronize the vibrations of carefully prepared quartz crystals to beams of pure light attuned to the energy levels of specially selected atoms flung from the hearts of dying stars. That's like, cosmic, man. So maybe those 13-moon guys would fit right in, after all. Cheers! --Stu ___ 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] looking for low-power system for gps ntp timekeeping
So yu are getting the Beaglebone Black for about $45. Do you have a link to a supplier. I thought they were at least twice that price. On Sun, Jun 30, 2013 at 1:43 PM, Dennis Ferguson dennis.c.fergu...@gmail.com wrote: For a $5-$10 difference in price for the board I think these are worth it. Chris Albertson Redondo Beach, California ___ 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 low-power system for gps ntp timekeeping
Chris Albertson albertson.chris at gmail.com Sun Jun 30 23:12:23 EDT 2013 So yu are getting the Beaglebone Black for about $45. Do you have a link to a supplier. The Beagle Bone Black is about half the cost of the Beagle Bone (White) and the pricing is reasonably consistent across vendors. ___ 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] [OT] a different sort of time-nut
And I thought the synchronometer is the fancy 1000 Hz motor clock I have made by General Radio! Who'da thought . . . I gotta meditate on this. my head hurts. Don Stewart Cobb http://www.lawoftime.org The 13 Moon / 28-day calendar (synchronometer) is the key that allows us access to the vast realm of the synchronic order ... This is a Galactic timing program that also serves as a master synchronization matrix that any other calendar or numerical system can be plugged into. Hmm. What are the pinouts on those plugs? Do they use leap seconds to synchronize galaxies, or do they have a more elegant method? When you think about it, though, many of us are doing our best to synchronize the vibrations of carefully prepared quartz crystals to beams of pure light attuned to the energy levels of specially selected atoms flung from the hearts of dying stars. That's like, cosmic, man. So maybe those 13-moon guys would fit right in, after all. Cheers! --Stu ___ 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 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.
Re: [time-nuts] looking for low-power system for gps ntp timekeeping
From: Dennis Ferguson [] You aren't necessarily showing the part where the Raspberry Pi is a bit weak, though. How well do clients which receive their time via the USB ethernet interface do? The Beaglebone Black has about three advantages going for it in this application: [] For a $5-$10 difference in price for the board I think these are worth it. The RPI makes a fine, low-power replacement for Intel hardware for this, but the Beaglebone Black has the raw material to do significantly better at this than either of them. The only problem with the Beaglebone is that it is not as popular as the Raspberry Pi, so making use of the former is going to require one to do more work on one's own to take advantage of it. Dennis Ferguson == Dennis, I've tested with 75 clients (simulated load) and not seen any problems with the Raspberry Pi's own time keeping. I'll set my FreeBSD PC to look at the the three Raspberry Pi cards and report back A first report is that the offset is shown as 0.091 ms from one RPi and 0.065 ms from the second, and 0.056 ms on the third RPi which is operating over Wi-Fi. This is far better than I see from any Internet servers on my Cable Modem ISP service. Jitter is 0.022 and 0.027 ms for the LAN connected devices, again much better than the best Internet device which shows 0.110 ms (at what is the middle of the night for many - 06:00 clock time here). Here the two units are similarly priced, so you can take your choice. There is one write-up here: https://groups.google.com/forum/#!topic/beagleboard/bU_xZ9tWoiA for using the BeagleBone Black as an NTP server, but he seems to have an offset of -0.281 ms from his PPS source, which is rather high. Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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.
