Re: [time-nuts] Ublox neo-7M GPS
Hal, Except for a few magic target frequencies, the output will have occasional (or frequent) missing or extra cycles. The output will be clean if you are dividing by a power of 2. (By switching from 10 MHz to 8 MHz, you have changed from frequent to occasional.) Not true that dividing by two cleans it up. If you change the cycle time from time to time as you would have to do even at 8MHz since the TCXO is free-running to GPS and then divide this by two you still get the non-standard cycle times, but these will now simply be twice as long on average. The divider will not magically remove the huge cycle to cycle jitter whenever the unit does a phase adjustment. Only a PLL with a very long time constant compared to the cycle time (e.g. 100ms versus 100ns) can clean up the phase jitter. Also, the number of adjustment cycles at 8MHz now depends on the frequency error of the TCXO versus UTC. Taking a heat gun and cold spray to the unit would show that easily. However at 8MHz with a 48MHz crystal you only need to add/shorten the cycle time to compensate for the error of the crystal versus UTC. This is similar to the sawtooth error we are all familiar with. At 10MHz you have to add cycle adjustments to both compensate for the frequency error of the TCXO as well as the N/M divider to generate 10MHz out of 48MHz. Wether you have 10,000's of phase adjustments per second or just a few doesn't change the fact that you are changing the cycle to cycle time by massive degrees/percentages/nanoseconds. The question is: does the hardware/software that calculates when to increase/shorten the cycle work with error-diffusion that keeps track of the overall phase error accrued, or does it simply try to get close enough by statistical averaging. In the former case, the 10MHz phase over long periods of measurement would stay in phase with the UTC 1PPS phase. In the later case the 10MHz phase would drift over time versus UTC which is really bad of course. Which way does the uBlox hardware compute the error? I don't know, and the documentation I have seen does not add any insight. bye, Said ___ 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] Ublox neo-7M GPS
Hi Tony, that's consistent with what I remember. Do you have the capability to count the number of 10MHz pulses per second to see if it is phase-coherent with the UTC 1PPS pulse? I am thinking that the software may be using statistics to approximate 10 million cycles per second, which would mean they may or may not be exactly 10 million cycles.. thanks, Said In a message dated 8/20/2014 11:07:59 Pacific Daylight Time, tn...@toneh.demon.co.uk writes: On 19/08/2014 16:11, Ed Palmer wrote: Does anyone have a neo-7M and an HP 5371A or a 5372A Analyzer? Use the Histogram Time Interval function to measure a block of samples. That will show the length of the samples with a resolution of 200 ps. That's what I did a couple of years ago when I analyzed the Navsync CW-12 with the old and new firmware. FWIW, I just had a look at the timepulse on a NEO-7M. I configured it to 10MHz, 50:50 duty cycle when locked, disabled when out of lock. I don't have any of those Analyzers so I used an HP 54615B digital scope. The period of the majority of cycles was 104ns with 'random' cycles being 84ns. I did not observe any other cycle periods. I don't know how accurate the time measurements are on the scope, but it looks like the timing is derived from an approx 48MHz clock, and the timing phase/frequency adjusted by periodically deleting 48MHz clock cycles. Although I said random, I couldn't make any observations as to the statistics of the short and long cycles or their distribution - I guess I'll have to write some software for my STM32F4 discovery board for that. If I get time, I'll do the same with a Reyax RYN25AI receiver which has a UBLOX MAX-7C module. Tony ___ 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] Ublox neo-7M GPS
Hi Graham, its not a GPSDO though, not even a simple one :) It does not discipline an oscillator. It generates the output by mathematically calculating how many phases it has to add/drop in a second, then digitally adds/drops/extends/retards the phase of the output clock to achieve an average of number of desired clock cycles. This causes huge cycle-to-cycle phase jumps. One cycle maybe 100ns long, and the next adjacent cycle could only be 87ns long! Without filtering, I doubt the output is useful for much because it has phase jumps from cycle to cycle of 10's of nanoseconds or more. A true GPSDO (even the cheapest one) has cycle to cycle phase jumps of femtoseconds only due to oscillator jitter. You can easily make a GPSDO out of it though through a simple EXOR gate (74AC86), feeding a TCXO/VCXO through a low-pass filter, and designing a phase loop low-pass filter with less than say 10Hz bandwidth.. That approach has been discussed here in the past a couple of times and is very cost-effective. That is essentially what the Conner Winfield units do. The drawback is that you have very large phase and frequency jumps when going into and coming out of holdover on these units, because the unit does not have a holdover oscillator with any type of reasonable stability, and whatever high ADEV stability your filter oscillator has is lost due to the analog loop bandwidth of typically 10Hz meaning the internal $1 crystal of the GPS receiver itself determines ADEV. Bye, Said In a message dated 8/19/2014 10:03:27 Pacific Daylight Time, coll...@navcanada.ca writes: Said, Agreed, hence my reference as a very simple self-contained GPSDO. Even after a very quick first glance at the documentation it didn't seem like it would be much of threat to more traditional GPSDO's. It will be interesting to play around with and see what it can do. Cheers, Graham ve3gtc -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Said Jackson Sent: August-19-14 12:44 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Ublox neo-7M GPS Graham, Those are not GPSDO's by definition. They are based on NCO technology. The difference being many orders of magnitude higher phase noise and ADEV noise. We tried to measure their phase noise and our TSC5125A could not even lock on to the 10MHz - they were so noisy. You can make a GPSDO out of them if you use a post filter oscillator loop locked with sufficient time constant (10s).. Sent From iPhone On Aug 19, 2014, at 9:20, Collins, Graham coll...@navcanada.ca wrote: Good day all, On another list to which I subscribe, there has been chatter about the Ublox neo-7M GPS receiver. It seems that the device's configurable timepulse output is configurable from 0.25hz to 10 MHz as well as it's duty cycle and can also be set to be one condition when the GPS is not locked and a different condition when locked (i.e. 1 PPS if not locked, 10KHz when locked). This seems all too good to be true. Sounds like a very simple self-contained GPSDO. I don't know anything more about the device. I have just downloaded the documents and will be spending some time reading them. I am curious if any other list members were aware of this feature of this device and have had any first hand experiences with it. There is another model, the 7N. the 7M uses a simple crystal clock, the 7N a TXCO. Cheers, Graham ve3gtc This electronic message, as well as any transmitted files included in the electronic message, may contain privileged or confidential information and is intended solely for the use of the individual(s) or entity to which it is addressed. If you have received this electronic message in error please notify the sender immediately and delete the electronic message. Any unauthorized copying, disclosure or distribution of the electronic message is strictly forbidden. NAV CANADA accepts no liability for any damage caused by any virus and/or other malicious code transmitted by this electronic communication. Le présent message électronique et tout fichier qui peut y être joint peuvent contenir des renseignements privilégiés ou confidentiels destinés à l’ usage exclusif des personnes ou des organismes à qui ils s’adressent. Si vous avez reçu ce message électronique par erreur, veuillez en informer l’ expéditeur immédiatement et supprimez le. Toute reproduction, divulgation ou distribution du présent message électronique est strictement interdite. NAV CANADA n’assume aucune responsabilité en cas de dommage causé par tout virus ou autre programme malveillant transmis par ce message électronique. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow
Re: [time-nuts] Ublox neo-7M GPS
Hal, I guess that depends on your definition of disciplined. The products that I am familiar with don't consider adjusting phase length of an asynchronously running oscillator on a cycle-to-cycle basis thousands of times per second to try to fit 10 million of them (or whatever your desired frequency is) disciplining. Best case you could call it phase/frequency hopping to try to achieve some sort of frequency average in my opinion. However if you used a DDS to adjust the frequency of an asynchronous clock digitally and control that frequency by digital adjustment that would be true disciplining of your frequency source. So analog versus digital has nothing to do with it. If your DAC had only a few bits you still would have many orders of magnitude less phase errors than the NCO approach; you can do the simple math: Let's say your VCXO had only 4 bits and a +/-20Hz frequency adjustment range. Pretty nasty considering any low-ball GPSDO these days has at least 21 bits EFC resolution. Now changing one LSB on our 4 bit DAC would thus result in a massive frequency change of +/-2.5Hz. This would result in a phase drift of 2.5E-07 or 250ns drift over ONE ENTIRE SECOND. That means 250ns divided by 10 Million (!!) cycles or a cycle to cycle change of only 25 femtoseconds when the DAC changes state. Theoretically that cycle length change would only happen ONCE if the system was a digital DDS type system. How does a single 25 femtoseconds cycle length change on our hypothetical 4 bit EFC DAC compare to a 10ns cycle to cycle change that happens thousands of times or more per second on typical NCO's? My point is we are talking performance differences of 5 or 6 orders of magnitude between a GPSDO (digital or analog) and an NCO. We are not comparing apples to apples. These are not even apples to oranges in my opinion. bye, Said In a message dated 8/19/2014 12:32:02 Pacific Daylight Time, hmur...@megapathdsl.net writes: saidj...@aol.com said: its not a GPSDO though, not even a simple one :) It does not discipline an oscillator. It generates the output by mathematically calculating how many phases it has to add/drop in a second, then digitally adds/drops/extends/retards the phase of the output clock to achieve an average of number of desired clock cycles. Is there something about the term GPSDO that says I have to do the D in the analog domain rather than the digital domain? I agree that current technology doesn't give results that are useful for many applications that currently use GPSDOs. What if the clock ran at a GHz? 10 GHz? Sure, it would have spurs, but would it be useful for some applications? Is a GPSDO still a GPSDO if the D/A driving the VCXO only has a few bits? How many bits does it need to be a real GPSDO? Is a battery powered wall clock listening to WWVB at 2 AM a WWVDO? It's got a pretty good ADEV if you go out far enough. ___ 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] Ublox neo-7M GPS
Hi Tom, last time I looked at these I tried figuring out what they were doing. It is very hard to get measurement data, our TSC did not converge on their signal, and looking at the output on a scope revealed only a bunch of crazy random phase jumps. I guess one could use a counter to measure how many time pulses are being sent in x seconds with x being a large number, or divide the output by 10 million and see how the pulse moves back and forth compared to the 1PPS UTC output.. Since I don't know the exact algorithm being used, I said adds/drops/extends/retards in my previous email. I did not mean to imply that the unit is doing all or any of those items. But that is exactly part of the problem isn't it, there is no clear description of what exactly is happening in the uBlox documents or the CW docs for that matter that I could find. I for one would not use that output to drive a processor or other digital device directly, who knows what happens if the processor sees a 100ns, then a 110ns, and then an 70ns pulse if it is only rated at 10MHz and 100ns pulse-width +/- a couple percent for example.. Without knowing the exact minimum phase time period specification that could come out of one of these NCO's, one should not properly use that signal in a digital design. My initial concern was that this is time-nuts, and we should call a GPSDO a GPSDO, and an NCO an NCO in my opinion. Nothing wrong with one or the other, but they sure are not the same thing - by 6 or more orders of magnitude in phase stability. We usually are concerned here about parts per trillion stability and accuracy, and now we are mixing things up that are millions of times worse than one another.. bye, Said In a message dated 8/19/2014 13:08:52 Pacific Daylight Time, t...@leapsecond.com writes: Hal, as long as you maintain long-term phase lock it's a disciplined oscillator. So, yes, a carrier tracking WWVB receiver with sufficiently stable flywheel LO is a WWVBDO. Said, too-short or too-long 100 ns cycles is one thing. Still ok for many applications. But tell me more about extra or missing pulses in the ublox-7. That sounds like a show stopper to me. /tvb (i5s) On Aug 19, 2014, at 2:05 PM, Hal Murray hmur...@megapathdsl.net wrote: saidj...@aol.com said: its not a GPSDO though, not even a simple one :) It does not discipline an oscillator. It generates the output by mathematically calculating how many phases it has to add/drop in a second, then digitally adds/drops/extends/retards the phase of the output clock to achieve an average of number of desired clock cycles. Is there something about the term GPSDO that says I have to do the D in the analog domain rather than the digital domain? I agree that current technology doesn't give results that are useful for many applications that currently use GPSDOs. What if the clock ran at a GHz? 10 GHz? Sure, it would have spurs, but would it be useful for some applications? Is a GPSDO still a GPSDO if the D/A driving the VCXO only has a few bits? How many bits does it need to be a real GPSDO? Is a battery powered wall clock listening to WWVB at 2 AM a WWVDO? It's got a pretty good ADEV if you go out far enough. -- 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. ___ 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] CW12-TIM
Good point. I am a sucker for great surplus equipment too, in fact I have two rooms full of stuff most of which is used from time to time.. I envy Tom's collection. I think we need to have a Time Nuts For Dummies article written that takes J. Vig's writing and puts it into much less of a technically rigorous 3 to 10 page article that makes timing accessible to the average product manager or systems engineer, and adds a hole bunch of GPS Disciplining explanation as well. This should be non-academic (who cares about Leesson's formulas digested to the N'th degree when simply looking for a lab reference) and should be fun and easy to read, but still get all the important points across. bye, Said In a message dated 7/12/2014 15:01:33 Pacific Daylight Time, mag...@rubidium.dyndns.org writes: Said, ... and deprive us from cheap surplus oscillators of good performance? What where you thinking? :) But I agree fully with your point, people don't understand how their poorly speced requirements translate into cost and design-time. Accurate time to the fs for no budget is what you can expect if they push their wishlist, but they have seen the E-18 numbers in some fancy article, so as is now possible. I think not (mixing time and frequency numbers is just what you can expect among other things). Also, ADEV numbers isn't everything, it can be a splendid answer to the incomplete and incorrect asked question. Cheers, Magnus On 07/12/2014 10:44 PM, saidj...@aol.com wrote: Graham, I think that is the real challenge here: most folks don't know what precise means for them. Timing is such a novel technology that most folks are amazed that we are trying to get parts per trillion (or better) accuracy and stability! We get customers all the time that want very precise timing, very good phase noise, and overall very good performance but are only used to TCXO's with maybe 10ppm frequency accuracy and cannot specify anything beyond that. The challenge is to explain the cost-benefit to them, like: 1ppm == $1 0.01ppm = $300 10ppt == $1500 0.1ppt == $$$ etc. Once dollars are mentioned, desired specifications usually are attained at fairly quickly :) We recently had an inquiry that we forwarded to a major atomic oscillator vendor, and the estimated $10 Million design cost and 10 year design time quickly shut that idea down.. bye, Said In a message dated 7/12/2014 08:54:09 Pacific Daylight Time, gh78...@gmail.com writes: Shane: The question I think that is being asked is ... What does precise mean to you? To the nearest order of magnitude, what kind of accuracy are you looking for on your three signals. This defines the kind of system you will need. This group normally aspires to the more accurate end of the scale. If you are doing simple time logging of some process, then you are probably at the other end of the possible accuracy scale, and can do things much more simply and cheaply. So ... 1 PPS: +/- 1 ns? 10 ns? 100 ns? 1 us? 10 us ? NTP: +/-10 ms? 100 ms? 1 second? 10 MHz: +/- 10E-6?10E-9? 10E-12? 10E-14? --- Graham == On Sat, Jul 12, 2014 at 3:57 AM, Shane Morris edgecombe...@gmail.com wrote: Hal, As much as I'd like to explain the big picture in list, it would make God awful noise - if you wish to know any details, I encourage you to respond to me off list. Given the fact that the robotics is so totally off topic, I'm not willing to discuss them here. Thats only out of respect to the topic of the list. The only real stipulations at this design part of the project is 10MHz out, 1PPS out, and NTP out. Please don't think I'm being narqy, I'm really not going to pollute the list with off topic chatter. I am more than happy to discuss off list, as and when. David, I was planning to use RaspberryPis in some part of the network, and of course, I must be silly, they have ethernet, and can run Real Time Linux (the LinuxCNC distros that have been made for control of CNC machines). By the way, the whole network uses heterogeneous CPU types, I'm pretty agnostic to CPU type, as long as it does the job I need it to. The actual ethernet interface won't be as deterministic as we'd like, being chained to the USB bus, but if one was not to put any other USB devices on, nor attach anything that draws power, the USB performance would be good enough for second accuracy NTP frames. This is without any real analysis of any spec sheets, although I have this link: http://www.synclab.org/?tag=raspberry%20pi Thats an interesting read in and of itself. An additional link is: http://www.geekroo.com/products/795 Which is a Mini ITX motherboard for RaspberryPi, which can then go nicely into a 1RU case. Add LCDs and other bits and bobs as needed (I saw a nice little LCD
Re: [time-nuts] CW12-TIM
Graham, I think that is the real challenge here: most folks don't know what precise means for them. Timing is such a novel technology that most folks are amazed that we are trying to get parts per trillion (or better) accuracy and stability! We get customers all the time that want very precise timing, very good phase noise, and overall very good performance but are only used to TCXO's with maybe 10ppm frequency accuracy and cannot specify anything beyond that. The challenge is to explain the cost-benefit to them, like: 1ppm == $1 0.01ppm = $300 10ppt == $1500 0.1ppt == $$$ etc. Once dollars are mentioned, desired specifications usually are attained at fairly quickly :) We recently had an inquiry that we forwarded to a major atomic oscillator vendor, and the estimated $10 Million design cost and 10 year design time quickly shut that idea down.. bye, Said In a message dated 7/12/2014 08:54:09 Pacific Daylight Time, gh78...@gmail.com writes: Shane: The question I think that is being asked is ... What does precise mean to you? To the nearest order of magnitude, what kind of accuracy are you looking for on your three signals. This defines the kind of system you will need. This group normally aspires to the more accurate end of the scale. If you are doing simple time logging of some process, then you are probably at the other end of the possible accuracy scale, and can do things much more simply and cheaply. So ... 1 PPS:+/- 1 ns? 10 ns? 100 ns? 1 us? 10 us ? NTP: +/-10 ms? 100 ms? 1 second? 10 MHz: +/- 10E-6? 10E-9? 10E-12? 10E-14? --- Graham == On Sat, Jul 12, 2014 at 3:57 AM, Shane Morris edgecombe...@gmail.com wrote: Hal, As much as I'd like to explain the big picture in list, it would make God awful noise - if you wish to know any details, I encourage you to respond to me off list. Given the fact that the robotics is so totally off topic, I'm not willing to discuss them here. Thats only out of respect to the topic of the list. The only real stipulations at this design part of the project is 10MHz out, 1PPS out, and NTP out. Please don't think I'm being narqy, I'm really not going to pollute the list with off topic chatter. I am more than happy to discuss off list, as and when. David, I was planning to use RaspberryPis in some part of the network, and of course, I must be silly, they have ethernet, and can run Real Time Linux (the LinuxCNC distros that have been made for control of CNC machines). By the way, the whole network uses heterogeneous CPU types, I'm pretty agnostic to CPU type, as long as it does the job I need it to. The actual ethernet interface won't be as deterministic as we'd like, being chained to the USB bus, but if one was not to put any other USB devices on, nor attach anything that draws power, the USB performance would be good enough for second accuracy NTP frames. This is without any real analysis of any spec sheets, although I have this link: http://www.synclab.org/?tag=raspberry%20pi Thats an interesting read in and of itself. An additional link is: http://www.geekroo.com/products/795 Which is a Mini ITX motherboard for RaspberryPi, which can then go nicely into a 1RU case. Add LCDs and other bits and bobs as needed (I saw a nice little LCD with an ATMega driver taking TTY strings in the ODROID Magazine earlier today - it was meant for an ODROID, but it will work with anything that'll output VT100 codes). Once in an 1RU case, it looks neat, and would work just as well as a $500 NTP ethernet time source second hand off eBay, if not much more configurable and hackable. Many thanks for the thoughts! Shane. On Sat, Jul 12, 2014 at 5:50 PM, Hal Murray hmur...@megapathdsl.net wrote: edgecombe...@gmail.com said: I am needing a GPS source of precise time, in three flavours - 10MHz (or so), 1PPS, and ethernet NTP. In the beginning, the NTP will be most important, and as time goes on, I'll need the 1PPS signal. ... If a static CW12-TIM ethernet clock could be made, I would be willing to try my hand at mounting them to mobile robots, again, for synchronised timing of events. I'm missing the big picture. Are the robots the end target? What are you going to do before that? Do the robots have a network connection? (maybe only WiFi to a local PC controlling them) How accurately do the robots have to be synchronized? -- 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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Sad news Ulrich Bangert
So does anyone know how/why he died? Does anyone have the actual sources for his tools? All I know is that he told me he used a very old database program to write them under Borland or something like that.. Bye, Said In a message dated 6/26/2014 12:16:18 Pacific Daylight Time, shali...@gmail.com writes: I have downloaded his tools as currently available on his web site. I intend to make them available on my web site unless I hear otherwise from someone authorized to talk on the behalf of his estate. Didier KO4BB On June 26, 2014 2:38:57 AM CDT, Stefan Heinzmann stefan_heinzm...@gmx.de wrote: A great loss and a sad story, indeed. That leaves me wondering what will happen to his software tools, which we have grown accustomed to using. I'm not aware that he disclosed the sources. Has anybody got access to them and can take care of them? Or will all this good work fade away? Cheers Stefan On 24.06.2014 23:17, Didier Juges wrote: Thank you Bruce. Like others, I was saddened to hear of Ulrich's passing. His contributions and the good spirit under which he contributed were notable. He will be missed. Didier KO4BB On June 23, 2014 4:58:24 PM CDT, br...@ko4bb.com br...@ko4bb.com wrote: Sadly Ina was terminally ill and died in May 2012. Ulrich kept this to himself until about six months later in an email explaining why he had been out of touch. In respect for Ulrich's wishes I kept this news off the list. Ulrich's Obituary indicates that one parent, his in-laws and siblings as well as his nieces/nephews survive him. If requested I'll post the URL for his obituary which includes a contact address. Bruce On June 22, 2014 at 1:16 PM ewkeh...@aol.com wrote: It is a shock and a loss not just to time nuts but many others that where touched and benefited from him. Like in the case of Brooks I know what I will do and I urge those of you that knew him through any type of contact make the old fashioned proper thing by sending his wife a letter or card Frau Ina Bangert, Ortholzer Weg 1, 27243 Gross Ippener Germany Bert Kehren In a message dated 6/22/2014 12:36:22 P.M. Eastern Daylight Time, ail...@t-online.de writes: I am shocked to hear that. Urich was a very helpful friend, I've learned a lot from him. I'm so sorry to hear that. Please allow me to say some words in Ulrichs (and my) native language. Die Nachricht vom Tode Urich's hat mich sehr getroffen. Ich habe ihn als einen hilfsbereiten und offenen Menschen kennen gelernt, aber leider nie persönlich kennen lernen können. Bitte, lieber Hartmut, falls Du Kontakt hast, richte der Familie mein herzliches Beileid aus. Thank you very much. Volker - DF9PL Am 20.06.2014 22:52, schrieb Hartmut Paesler: Dear group, unfortunately I have to deliver the sad news that Ulrich Bangert, DF6JB passed away on 11/06, aged 59. Best regards, Hartmut DL1YDD ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Sent from my Motorola Droid Razr HD 4G LTE wireless tracker while I do other things. ___ 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] GPSDO standard interface?
I dislike TSIP quite a bit. It's a disaster in my opinion if you are not intimately familiar already with the Trimble binary commands, and exists in a number of inconsistent and non-compatible dialects as far as I know. No way for a human to enter a simple command in a simple text terminal, you have to have everything translated by some application. I know the software folks like binary better than ASCII, because parsing binary commands can theoretically be done with less effort. I think effort == results. There is SatStat, GPSCon, and Ulrich's great Z38xx control program for human readable SCPI commands besides the good old ASCII terminals. HP leads the way with GPIB/SCPI in my opinion. But it's like religion, everyone thinks theirs is the right one, and everyone else is on the wrong path. bye, Said In a message dated 6/26/2014 14:01:35 Pacific Daylight Time, hol...@hotmail.com writes: There are TSIP commands for doing all those things. It should be fairly easy to adapt them to control your hardware and whatever GPS receiver you are using. The nice thing about implementing a TSIP interface is being able to use existing programs like Tboltmon and Lady Heather (over 30,000 lines of code) to monitor and control it. Also NTP knows how to talk TSIP. I am planning on the output of at least position, corrected phase error, DAC value, ambient temperature, and a few other things. I also see a need to read and write the PID gain and damping factors, but that may just have to be a custom tty interface. It may be that I need to have a pass-through mode to give direct access to the receiver for triggering site survey, etc. ___ 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] FE5680 GPS Disciplined Controller Update
Tom, airflow, or changes in airflow are typically much worse for ADEV than actual ambient temperature changes in still air. In still air for example a typical Eurocan DOCXO will have a case temp of about 55C to 60C at 25C ambient. Turn on any kind of significant airflow over that part and the air temperature will be nearly the same as before, but the case of the DOCXO is now very quickly cooled to 30C to 40C by the airflow. This affects mostly TCXO and single-oven units (including Rb's etc), it does very little to DOCXO units typically because the outer oven takes the brunt of the temp change and insulates the inner oven. There are other components on the PCB though next to the DOCXO that will be affected such as the DAC, DAC reference, EFC filters, current ground loops due to changing heater-current on the ground pin, etc. This even affects TCXO's because they are typically heated by themselves and other components on the PCB, and any kind of airflow change will cause an instant temp change on the TCXO due to cooling. So in my opinion a bang-bang controlled fan near any kind of oscillator is about the worst thing one can do for short term stability. bye, Said In a message dated 6/24/2014 13:35:21 Pacific Daylight Time, t...@leapsecond.com writes: However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. Can you clarify the two orders of magnitude claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report. I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 1 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover. Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference? /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sad news Ulrich Bangert
Wow, that's a shock. He was such a nice guy, always supporting requests for changes etc. Very sad. He was quite young as well! Our condolences to his wife and family. Said In a message dated 6/20/2014 13:58:36 Pacific Daylight Time, timen...@paesler.de writes: Dear group, unfortunately I have to deliver the sad news that Ulrich Bangert, DF6JB passed away on 11/06, aged 59. Best regards, Hartmut DL1YDD ___ 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] Fwd: CGSIC: Known Problem With Certain GPS Devices
It would be good to understand which receivers are adversely affected by this.. the USCG did not list affected vendors/devices.. In a message dated 5/15/2014 15:19:51 Pacific Daylight Time, mag...@rubidium.dyndns.org writes: Hi fellow time-nuts, I think this message is interesting. It shows that some receiver vendors have been cheating on an important detail, ignoring the health status and being confused as a result. Cheers, Magnus Original Message Subject: CGSIC: Known Problem With Certain GPS Devices Date: Thu, 15 May 2014 21:20:23 + From: Civil Global Positioning System Service Interface Committee (CGSIC) cg...@cgls.uscg.mil Reply-To: cg...@cgls.uscg.mil To: cg...@cgls.uscg.mil cg...@cgls.uscg.mil All CGSIC: May 15, 2014 Recently, many GPS users have reported intermittent GPS outages in their devices. After investigating, the U.S. government has linked the problem to flawed processing of GPS satellite data within certain GPS receiver chipsets. The GPS satellite service continues to function as designed and is fully operational and available worldwide. The problem affects only user equipment that erroneously ignores the satellite health status information broadcast from every GPS satellite. The problem is not related to the April 28, 2014, activation of civil navigation messages on the GPS L2C and L5 signals. Since March 15, 2014, the Air Force has been conducting functional checkout on a GPS satellite, designated Space Vehicle Number (SVN) 64. SVN 64 broadcasts a data message that clearly indicates SVN 64 is unusable for navigation. Nevertheless, the U.S. government has confirmed that certain GPS receivers are using data from SVN 64, in violation of GPS interface specifications, resulting in outages or corrupted, inaccurate position calculations. The Air Force testing is scheduled to end in mid-May 2014 at which time SVN 64 will begin normal operation. At that point, these problems may stop occurring. Meanwhile, the U.S. government urges all GPS device makers to review their products for compliance with the GPS interface specifications, and if necessary, to issue software/firmware updates to users as soon as possible. View specifications http://www.gps.gov/technical/icwg/ Users experiencing GPS outages should check with their device manufacturers for available software/firmware updates. In addition, any civil user seeing unusual behavior in GPS user equipment should report it to the U.S. Coast Guard Navigation Center (NAVCEN). Aviation users should file reports consistent with FAA-approved procedures. Military users seeing unusual behavior should report it the GPS Operations Center (GPSOC). Please direct any civil user questions to NAVCEN at (703) 313-5900, http://www.navcen.uscg.gov Please direct any military user questions to the GPSOC at (719) 567-2541, DSN: 560-2541, gpsoperationscen...@us.af.mil https://gps.afspc.af.mil Military alternate: Joint Space Operations Center, (805) 606-3514, DSN: 276-3514, jspoccombat...@vandenberg.af.mil See also: Technical explanation for device makers (PDF) http://www.navcen.uscg.gov/pdf/gps/GPSOC_PRN 30_Notice.pdf V/R Rick Hamilton CGSIC Executive Secretariat GPS Information Analysis Team Lead USCG Navigation Center 703-313-5930 ___ CGSIC one-way mailing list Unsubscribe: http://cgls.uscg.mil/mailman/listinfo/cgsic If you would like to report abuse of the CGLS listserv please send an email to: cglsad...@uscg.mil ___ 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] Rb vs.Crystal OCXO
Hi Hans, in order not to chase the tempco and aging algorithm (it will reset the values by itself every 10 minutes while locked to GPS as you have noted) you may simply turn tempco and aging compensation off manually during your test period. This can be done by the serv:tas x, yy... command. The first parameter is the mode; 0 being both off, 1 being aging compensation only, and 2 being both aging and temperature compensation. So the commands would be: serv:tas? to query the current settings, then issuing the command: serv: tas 0, xx, xx ... where xx, xx.. are the same values that were shown with the query command. To re-enable the aging and tempco compensation when you are done with your measurement, simply send the serv: tas 2, xx, xx ... command using the same settings again as the query command had returned. Hope that helps, Said In a message dated 4/28/2014 05:32:41 Pacific Daylight Time, hans.holz...@gmail.com writes: said, if i understand correctly, while in holdover, activated by sync:hold:init, temperature and aging compensation are still active (as it should be). however, to measure drift, i have to somehow disable these compensations, haven't i? yesterday, i wrote down the values of temperature and aging compensation, then set both to 0. in holdover the software does not seem to recalculate the values, at least not during the hour or two i had the oscillator unlocked. on uli's Z38XX the EFC curve was flat, unlike when temperature and aging compensation are active (or not 0) during holdover. one hour or so after sync:hold:rec:init i checked the values again, and they were very close to the values before i reset them to 0. my question is: would this be the correct procedure to have a truely unlocked oscillator: start holdover and then set tempco and aging to 0? thank you, hans Bill, There is an easier method that does not jiggle the board mechanically: The command: sync:hold:init Disables the disciplining. sync:hold:rec:init Re-enables disciplining. The sync:tint? command can be used to check the drift while in holdover.. Bye, Said ___ 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] Symmetricom chip scale atomic clock
Hello everyone, let me address the below claims and commentary which was posted without first consulting with us. Microsemi has recently seen a slightly higher failure rate of the CSAC oscillators than expected. A small percentage of our customers have been adversely affected by this issue. We have been, and will continue to take care of this issue when it happens to units we sold by doing a warranty exchange of the CSAC for the affected customer unit, even if it should fall out of its normal warranty period. We believe in supporting our customers to the maximum extent possible, and of course want to deliver a product that has the highest level of quality possible. That said, we must remember that the CSAC technology is a ground breaking, never-before-done in commercial quantities, absolutely new type of oscillator technology, and being at the forefront of such a technology sometimes means there is a bit of a learning curve to deal with. This is one of the main reasons why no one else in the world besides Microsemi makes CSAC type products for commercial sale. So all in all, if a customer unit should get affected by this problem then the issue will be addressed by us and Microsemi with a quick turn around and a no questions asked approach, and we hope that this approach sets us positively apart from the competition. Lastly, we received the below comments/explanation from Microsemi about this issue which we have permission to share with you, and this should help alleviate the problem for new orders. Sincerely, Said Some Symmetricom (now Microsemi) Chip Scale Atomic Clocks have shown a failure mode that will manifest itself as an inability of the clock to achieve atomic lock. If the CSAC’s telemetry string is monitored, the failure mode will show up as a Status Level 8. Microsemi’s investigation into the problem uncovered three distinct root causes, although the symptom the user observes is always a Status Level 8, regardless of which root cause is the underlying issue. It is important to note that all three root causes are process issues, not design issues. All three root causes have been addressed, and Microsemi is currently producing CSAC’s with all three fixes implemented. A full re-qualification of the CSAC is also being done, to ensure that the fixes are effective. CSAC’ s already in the field that exhibit this failure mode have been, and will continue to be, replaced under warranty. In a message dated 4/24/2014 10:16:25 Pacific Daylight Time, les...@veenstras.com writes: Affected Products: Jackson Labs or Symmetricom time/frequency reference boards based on Symmetricom chip scale atomic clock ___ 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] new GPSDO kit
Hello everyone, sorry for the plug, but we just announced a new $568 complete GPSDO reference kit. This unit is a tiny desktop unit with 10m antenna, power supply, cables, CD, and other accessories. It is a low cost addition to our Fury GPSDO line, and contains a really good TCXO, a uBlox GPS receiver, and various power options. I believe this is the lowest-cost real GPSDO in mass production available on the market right now, and being a true GPSDO it has some fairly good phase noise and stability specs. http://www.jackson-labs.com/assets/uploads/main/LC-XO-Plus_PressRelease.pdf bye, Said ___ 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] comparing two clocks
Jim, when I did the test on the 53132A, I did the test with the two signals on top of each other with a very small cable offset of 400ps, then I added a 10ns delay line to the B signal just to see if the counter would behave differently. Here are the results, pretty much looks identical with 0.4ns offset or 10ns offset. bye, Said In a message dated 2/22/2014 10:06:30 Pacific Standard Time, ail...@t-online.de writes: Jim, If I get you right, you want to compare the 10MHz outputs (not the 1PPS). As Jim and Bob told us so far, the thing is to provide, that input A _always_ starts before input B (or the other way around). Connect the signals to an oscilloscope, and check, how much the phase differs - if the rising slopes occur close together, put some meters/yards of coaxial cable into one of the two signal paths. 1 meter is roughly worth 5ns - while the period of 10MHz is 100ns, 1m cable will phase shift about 18 degrees. I didn't verify, if the coax cable (with it's microphonic effect) affects the ADEV - does anybody have experience with this? Otherwise I'd have to fire up my counter and have a measurement on the run... Of course, inverting one signal will do as well. If you do it with extra electronics that definitely will affect the ADEV. I find it much easier to use some meters of cable. Ok, my counter is heating up by now... Volker Am 22.02.2014 14:17, schrieb Jimmy Burrell: I need some help with a 'noob' question regarding some practical examples in some of the NIST literature. When attempting to compare two clocks, I'm a bit confused on the subject of exactly how to use my counter to compare a delayed clock relative to another. Or perhaps I should just say 'comparing two clocks'. Let's take some concrete examples. Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the counter's input 'A'. Obviously, I can feed in a second, external reference clock at 10MHz into input 'B'. Suppose, however, I didn't have an external reference clock. Can I compare against the counter's internal time base by hooking a line from the rear jack time base output to channel 'B' input? Or am I making it too complicated? Do I simply plug into input 'A' and go? In a somewhat related question, in this article (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf) where two clocks, both divided to 1PPS, were compared, W.Riley makes the following statement, The two 1 PPS outputs were connected to a Racal Dana 1992 time internal counter having 1 nanosecond resolution, and the start and stop signals were separated sufficiently in time for the counter to function properly. I wonder what exactly is meant by separated sufficiently in time for the counter to function properly and how one would go about doing this? For example, is inverting one of the signals sufficient separation? If not, how is this typically done? Delay line? Thank you, Jim... N5SPE ___ 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. 1PPS_jitter.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS Antenna - was receivers in the same box.
Guys, on this subject, we put together and qualified a convenient and complete (fairly) low-cost timing-compatible GPS antenna kit that includes all the mounting materials, 150 feet of cable, all the connectors, and down to the last screw, nut, and bolt everything one would need to mount the antenna. Only standard tools are required for the installation. Compatible to any L1 GPS receiver, works from 2.5V to 5V. We get up to 52dB C/No with 150 feet of cable on our uBlox GPS receivers with this antenna, and the antenna cable length can be easily extended with F-connectors on both sides. This was done because so many people had problems getting all the parts to put an antenna together and called us for pointers to antenna kits (which we could not find), and we went out and bought all the different pieces needed to do so and put these together as a kit. Check out the _www.jackson-labs.com_ (http://www.jackson-labs.com) website if interested. 10% Time-Nuts discount (one unit per person) - $241.20 per kit w/o the lightning arrestor. A bit more pricey when the antenna lightning surge protector is included which is mandatory for any outdoor installation. I know this is more than what you would pay for a used antenna on Ebay, but we are not really making any money on this, we are pretty much selling it as a convenience to our customers. Please contact us off-this-list if interested. bye, Said In a message dated 2/5/2014 09:46:27 Pacific Standard Time, n1...@dartmouth.edu writes: As has been discussed before, a splitter intended for home satellite systems is a cheap solution as they have the bandwidth and the DC pass required. I have one between a couple of Thunderbolts. It powers the antenna and shows antenna OK on both. Using a splitter is better than just a T as it does lend some isolation between the receivers. David On 2/4/14 4:50 PM, mike cook wrote: Le 4 févr. 2014 à 22:35, Volker Esper a écrit : http://www.ebay.de/itm/HP-58516A-GPS-1-4-signal-Distribution-Amplifier-Splitter-N-type-/300997787447?pt=US_Ham_Radio_Receivershash=item4614ddbf37 I think I should have said that my box is only 25mm high. So any splitter will have to be less. A Mini Circuits splitter will just about do it , but I would prefer a smaller solution. Am 04.02.2014 14:08, schrieb mike cook: Hi, Till now I have been putting receivers in individual boxes. So to limit the growing number of boxes, I want to put two Resolution-T SMT receivers in one box, sharing power and antenna inputs. My question is How best can I share the antenna input, minimizing any interference between the receivers? . Will any interference matter? For example, I can easily connect three bits of shielded coax in a Y , but will probably get reflections from each receiver. As the cables will only be about 15cm long, would it matter? How about the DC antenna supply? The antenna DC will NOT be powering an antenna as it passes through a DC blocked splitter used to share an antenna between most of my receivers. I might be able squeeze a Mini-Circuits splitter in the box and DC-block both outputs but that may be overkill. What discrete circuitry might be a replacement? Will the Y do it? Someone must have already succeeded with this type of config. Thanks in advance for your input. Regards, Mike ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] housing multiple GPS timing receivers in the same box.
Michael, use a simple BNC T-splitter. Works perfectly for me as long as both GPS carry the same antenna voltage. No loss in signal quality evident from the C/No readings, and dirt-cheap. No need to over-complicate this. bye, Said In a message dated 2/4/2014 14:41:40 Pacific Standard Time, michael.c...@sfr.fr writes: ___ 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] Local Solar Time Clock
I hope this thread dies here. In a message dated 1/19/2014 13:22:10 Pacific Standard Time, a...@comcast.net writes: On 14-01-19 03:20 PM, Chris Albertson wrote: My feverish brain now cranks out that all we need is a electromechanical WWVB receiver, thus no active electronic parts. That would be a nice little challenge. That could work. I remember seeing an only World War II vintage teletype machine. It would print test from an HF receiver. Given the technology of the day it had no software inside The way it would work is you spin a disk at a nominal one rev per second and disk has electrical contacts on it that make a bit stream. Phase lock that with WWVB. So you control the motor speed. Actually I think you'd be better off using the 60KHz carrier. Again limiting yourself to only 1940's technology, I think you could build a local oscillator that would phase lock to WWVB's carrier, and from there you control the motor speed and and then you use the spinning disk to decom the bits. My first home personal computer (1964) was the Digi-Comp, no electricity, but definitely had software. Stored program, clock, display, conditionals... In the 1930s the Norden bomb-sight had software. The Jacquard loom had software. Perhaps the no software requirement should be refined. ___ 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] WAAS.....
The latest receivers are surprisingly resilient to GPS jamming. We tried jamming effects on all sorts of different GPS units ourselves, and the M12's go out right away for example, while the uBlox units are tough to jam. The new generation 7 ublox with Glonass etc should be even harder to jam if programmed properly. Attached is a sample plot showing GPS number of sats over a 1173 hours time frame (49 days) of a FireFly-IIA unit sitting in our lab with an older (and more jamming-sensitive) uBlox-5 in it. The antenna is simply a small cheap magnetic puck sitting on top of the two-story roof, and the roof is facing a highway. There was not a single instance of complete GPS Sat loss of lock during that time frame, even though the antenna sits only a couple 100 feet away from from Highway 17 which has jammers on it that we can see pass by on other GPS units. Please note that this version of GPSCon was updated to be able to show 16 sats in the SatCount by dividing the indicated number of sats by 2 rather than just showing a total of only 8 sats, but the indicator still says 8 sats max. So the variations in sats tracked are actually going from about 11 to 16 during the test. We had requested this change to GPSCon so it could support our 16 channel status output. It may be worth a try to get an eval kit of the latest uBlox chipset available to see how that handles typical known nuisance jamming scenarios. Bye, Said In a message dated 1/9/2014 11:00:20 Pacific Standard Time, br...@lloyd.com writes: On Thu, Jan 9, 2014 at 12:21 PM, Hal Murray hmur...@megapathdsl.net wrote: br...@lloyd.com said: navigation system that is going up. For that matter, is anyone running one of the new multi-system receivers? I notice that Garmin is selling them as a matter of course now. The prevalence of jamming might be the reason why. Aren't the alternatives using frequencies that are very close? Close enough so one the same receiver can pick up all the satellites. How much wider is the total bandwidth? Does the filter on a typical L1 antenna reject, or maybe just weaken, any of the other systems? GLONASS works on 1602.0 MHz (+/- ~4MHz). GPS works on 1575.42 MHz. There is only about 20 MHz difference at 1.6GHz so it is entirely possible that a wideband (noise-based) jammer would take out both, but be quite limited in range. A narrow-band jammer would probably take out GPS but GLONASS uses FDMA and separates each satellite in frequency by 0.5625 MHz. That means that a narrow-band jammer might get one, two, or three birds but probably not all of them. It does seem to me that a combined GPS/GLONASS receiver is going to be more resistant to jamming than a GPS-only receiver. And I make no claims to being an expert. I am just mostly thinking aloud here. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ 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. unitA_long_term_lock.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Trimble Thunderbolt 1pps
Hi Hal, still pretty impressive results, thanks for sharing the data. bye, Said In a message dated 1/3/2014 17:10:13 Pacific Standard Time, hmur...@megapathdsl.net writes: saidj...@aol.com said: Your plots don't show the wave being reflected by the cable end, and bouncing back and forth.. Until settling down. Yes. I'll put up some nasty pictures if anybody wants an ugly example. For that set of graphs, I tried to get rid of that sort of junk. I was working on the bench, using connectors and clipleads rather than PCBs or soldering whatever so things could be (much?) cleaner. For the coax, there was a short chunk of coax from the TBolt to a Tee at the scope, then the long chunk of coax under test, then a 50 ohm terminator at the other scope input. You can see some ringing due to the coax not really matching the terminator. For the twisted pairs, I used clipleads. The first/simple try wasn't good enough. The non-twisted cliplead wires were long enough to cause visible cruft. I ended up with a BNC to cliplead adapter with wires that were only 6 inches long. At the far end, I had a resistor merged into the clipleads, and adjusted it for best results. For the Cat-5 and Cat-6, I used a pair of RJ-45 to DB-9 adapters without the DB-9 connector. The wires coming out of the adapers are about 2 inches long. I forget what I did for the RG-6 which is 75 ohms. I have a pair of 50-75 adapters, but I don't remember doing any scaling to get the graphs to come out right and I don't see anything in the gnuplot commands to make the graphs. So I probably use a cliplead setup like for the twisted pairs. -- 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. ___ 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] video of CSAC GPSDO
Hello, fyi KF5OBS did a nice video review of the CSAC GPSDO (and Lecroy high end scope) that's posted on Youtube now: http://www.youtube.com/watch?v=CogN630jUSsfeature=c4-overviewlist=UU_XdpUc sSigyf4JrrPtI5eA bye, Said ___ 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] video of CSAC GPSDO
Hi John, well, I think he must have meant a new car back in 1971 :) That would be about right. It's not quite THAT expensive. Symmetricom seized to exist as an independent company a couple of days ago, they were bought out by MicroSemi.. They do make great products, for sure. Please note that I do not think that the NIST CSAC effort had much to do with the commercialized Symmetricom product. Same funding, but competing groups I think. NIST never took it to commercial grade. bye, Said In a message dated 11/4/2013 18:20:24 Pacific Standard Time, j...@westmorelandengineering.com writes: Said, Yes - Ha! In the video, KF5OBS does say something like the price of a new car. I have a very wide variance for what that could be - a Scion xB, Viper, Rolls Royce Bentley..., Ha! Great video - and thanks for letting us know about it. I actually went to the NIST chip scale site the other day - very interesting stuff. And, I am glad you guys are taking on such a technically ambitious project. It would appear Symmetricon is a great company to work with. Best Regards, John W. On Mon, Nov 4, 2013 at 6:06 PM, Said Jackson saidj...@aol.com wrote: John, Too much to post here publicly :) About one tenth of the price of the next higher available Cesium reference though, and not much more than some used decades-old functional FTS Cesiums selling on Ebay. Please call the office for quotes on CSAC units. Thanks, Said On Nov 4, 2013, at 17:27, John C. Westmoreland, P.E. j...@westmorelandengineering.com wrote: Said, How much do the CSAC's run? Thanks, John Westmoreland On Mon, Nov 4, 2013 at 5:14 PM, saidj...@aol.com wrote: Hello, fyi KF5OBS did a nice video review of the CSAC GPSDO (and Lecroy high end scope) that's posted on Youtube now: http://www.youtube.com/watch?v=CogN630jUSsfeature=c4-overviewlist=UU_XdpUc sSigyf4JrrPtI5eA bye, Said ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The 5MHz Sweet Spot
Forgot one comment: the good parts' plot also shows a very nice crystal retrace stabilization in the red EFC trace over about the first 6 days or so. After that the crystal goes into it's long term crystal aging mode. Retrace is one big reason why its best to let crystals run continuously.. In a message dated 11/3/2013 12:27:18 Pacific Standard Time, saidj...@aol.com writes: Hi guys, here are two plots of the same DOCXO product, one being jump-free over the 31 days test interval, another that had about 20 jumps in just ~4 days. Needless to say the later OCXO went back to the vendor to be opened up, and the crystal replaced. I have plots of units that were perfect for two+ days, then jumped like crazy, and units that jumped for days, then stabilized and worked perfectly. It's all random when failures do happen. Warren, frequency jumps are indicated by constant changes in EFC voltage (red trace) after the jump happened. Most of these in the attached plot are frequency jumps, that cause an offset in phase (sometimes just some 10's of nanoseconds over minutes). Sometimes the frequency will recover and that can be seen by the EFC voltage going back to the initial voltage before the jump happened. Phase jumps would just cause a small hop in EFC voltage, sometimes so small that it cannot be perceived. Also, note that most of these jumps have 1mV to 2mV changes in EFC, which for these oscillators would equal a frequency change of about 0.1 to 0.2 parts per billion frequency change. Very small, but on a GPSDO it leaves a huge footprint in the EFC voltage plot and the phase plot. I wish every crystal we get would work as well as the one in this 31 day test plot.. Bye, Said In a message dated 11/3/2013 11:57:50 Pacific Standard Time, warrensjmail-...@yahoo.com writes: Said Jackson posted: Crystal jumps are the biggest menace facing users of crystals/oscillators today. Are you including both phase jumps and frequency jumps together? Is one more or likely to happen than the other? Is it mostly a jump that effects just the phase or freq, or is there everything in-between, jumps that effects both phase and freq at the same instant in time also just as likely? We all know each effects the other, but that is only over time, instantaneously and over short time spans phase and freq jumps are separate things and maybe from different causes. A true phase jump causes only a one cycle freq error and a true freq offset jump does not cause an instantaneous phase jump. If the main causes of random freq jumps and random phase jumps are from different things, then with a high speed, high resolution detector, I wonder if knowing which event has really occurred, that then some correction compensation could be applied that does not effect the other. An Oversimplified example; A Phase lock loop does not care what the instantaneous freq is, and a true Freq Lock loop does not care what the phase difference is. With a DDS, one can change the freq without causing a phase step or it can cause a phase step, without causing a freq offset. With two variables (instantaneous phase and freq offset control) and two unknowns (instantaneous jumps in either), couldn't one apply a correction to the right place for any random step error that occurred? It would depend if the errors are caused by true independent random fast jumps or just slowly drifting interacting changes. ws *** Bob, et. al., Lots of opinions in this discussion, but none of it discusses the elephant in the room affecting todays' vendors: Random crystal instability versus manufacturing techniques. I can buy oscillators from multiple vendors that have -115dBc at 1Hz or better and noise floors of -182dBc. That technology is well understood and has been mature for a very long time and to me its boring. Recently Ulrich Rhode even had a great article in the Microwave Journal detailing how exactly to build one of those units. But what does it help me to have -115dBc if the darn thing jumps 50ppt every two to three days?? Crystal jumps are the biggest menace facing users of crystals/oscillators today and so far I have never been given a reasonable explanation from any of the vendors out there what causes it and how to avoid it or how they plan to address it. In fact no vendor we know tests for it to levels of sub-ppt over days which is what is necessary for any disciplined application as disciplining will clearly show even the smallest crystal jumps. Almost every vendor will do a frequency test only, where a phase test would be needed. Users of crystals/oscillators are left with doing an exhaustive yield test during burn-in to find bad crystals. We test our boards for 3 days and more to weed out jumpy crystals, and its a pain and very expensive
Re: [time-nuts] GPS time module
Sorry in advance guys, I could not resist doing a short comparison between our LC_XO module and this new Selig/RF-Suisse 1x1 module. Please excuse this blatantly biased comparison: The Selig module is slightly larger, and consumes about the same amount of power as the LC_XO (TCXO version), and basically provides a similar set of signals. It is however about twice as expensive, has an 8-week lead-time versus from-stock delivery, and there are other differences: * 20 channel GPS without WAAS/SBAS (Selig) versus 50 channels with WAAS/SBAS (LC_XO) * 1us time pulse accuracy (Selig) versus +/-25ns time pulse accuracy typ. (LC_XO) * Washing not approved (Selig) versus washing approved (LC_XO) * Selig requires an antenna cable to be plugged into the bottom of the PCB, then the module is soldered onto a customer PCB. Thus if the antenna cable becomes loose, it cannot be plugged back into the connector. LC_XO: antenna feed via the solder pins from carrier PCB * Selig I/O: Status LED and requirement to program for an I2C slave register, no NMEA or control command interface for GPSCon, GPSD, or Z38xx etc versus LC_XO: two NMEA outputs (RAW NMEA and Binary from uBlox GPS), JLT NMEA commands with custom commands, and SCPI control interface for third-party software * Selig 60,000 feet altitude limit versus 164,000 feet for LC_XO * Power requirement: Selig: 5V versus LC_XO 3.3V (LC_XO will provide 5V from internal DC switcher that can be used externally on carrier PCB) * Phase Noise: about the same between both units * ADEV: Selig slightly better at around 20s, LC_XO better above 1000s (LC_XO short-term ADEV can be significantly improved in stable environments by setting the time-constant of the loop to longer time frames) * Selig module options: GPS or no GPS versus LC_XO module options: TCXO, OCXO, and external 1PPS input with auto-switchover to internal GPS receiver * Firmware updates: Selig does not provide customer update mechanism versus LC_XO can be easily updated with various firmware versions available for customer download from the website without any website log-in etc. * Selig TCXO stability: +/-100ppb from -20C to +70C versus +/-75ppb from 0C to 60C or +/-25ppb from 0C to +60C (OCXO version) Selig/RF-Suisse offering this form factor is a welcome event as it validates the form factor in itself. I am however not seeing too many advantages for the Selig part in comparison especially at about twice the cost, am I missing something? bye, Said In a message dated 10/29/2013 14:54:51 Pacific Daylight Time, lstosk...@cox.net writes: Sorry if already posted: http://www.saelig.com/COMCR/COMCR002.htm ___ 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] Trimble Mini-T
John, have you taken a look at the Mini-JLT? Its compatible, just supports SCPI/NMEA instead of TSIP. bye, Said In a message dated 10/29/2013 17:14:22 Pacific Daylight Time, j...@westmorelandengineering.com writes: Hello Bob, Guess that is a shame - looked like a nice product and didn't take up a lot of space either. I was just curious. Thanks, John On Tue, Oct 29, 2013 at 4:55 PM, Bob Camp li...@rtty.us wrote: Hi I believe they were not making enough of them to make it worth continuing production. Bob On Oct 29, 2013, at 7:30 PM, John C. Westmoreland, P.E. j...@westmorelandengineering.com wrote: Hello, I was talking to a distributor here in San Jose and they told me the Trimble Mini-T is no longer available. Does anyone on this list know why Trimble decided to stop making it? The distributor doesn't know. Thanks, John Westmoreland ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Splitter for GPS antenna suggestions?
HP/Agilent/Symmetricom 58535A splitter/amplifier works great. Just unfortunate that they always come in N connector variant. Sometimes available dirt-cheap on Ebay.. They have 1-to-2 all the way up to 1-to-8 variants. In a message dated 10/25/2013 15:34:59 Pacific Daylight Time, hp_cisco...@yahoo.com writes: Hi, I want to see if it is possible to feed both the Trimble TB and the Jackson Labs Fury from the existing antenna. It appears both the TB and the Fury are 5vdc antenna power. Checked the auction site for splitters, but before I randomly buy anything, could someone please suggest what they use that works? Thanks, and 73 Frank KJ4OLL ___ 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] HP 4193A 4815A probe compatibility?
Hi Rick, Tom, one little bit of knowledge I learned: I like the HP 54701A FET probes for frequency-domain stuff. Available for $300 on Ebay sometimes. I built a small power supply for one of mine, and use it as a probe for my Spectrum analyzer and scopes. Almost indestructable. It works really well up to about 3GHz and beyond, especially for relative measurements. The only disadvantage is that it has 100K resistance to ground which may affect sensitive capacitive circuits, and that it has 20dB attenuation. Otherwise it works really well for Spectrum analyzer and Network analyzer applications. bye, Said In a message dated 10/16/2013 11:33:11 Pacific Daylight Time, rich...@karlquist.com writes: The 4815A used P channel FETs which were available 50 years ago and are now unobtainium. The 4193A used N channel FETs which were available 10 to 30 years ago and may even be currently available. They are DEFINITELY NOT INTERCHANGEABLE. This is according to ex-HP'er George Standford, who used to support vector impedance meters with HP's blessing. He held the worlds remaining supply of P channel FETs for fixing probes. He was in New Jersey, but my contact info for him is no longer valid. I don't know how to identify them, but in principle an ohmmeter might be able to identify the polarity of the FETs. While we are on the topic, it turns out that the market is such that a 4193A with probe might sell for $5000, but if you break up the set, the probe is worth $4999 and the instrument is worth $1. Well, maybe I exaggerated that a little, but not much :-) I actually know someone who paid $5000 for just a 4193 probe. He made the mistake of purchasing an instrument without a probe, and paid way too much. It is also worth noting that now you can buy a very nice vector impedance meter from Tomco in Austrailia for only $3000 new. I A/B'ed one of these with an HP one, and I will have to admit that the Tomco is the real deal, not a cheap knockoff. Rick Karlquist N6RK On 2013-10-16 09:15, Tom Knox wrote: I hope this is not to far off topic. Does any one know if the 4193A and 4815A probe are physically interchangeable and electronically compatible? If not does anyone know the differences and how to identify which is which? If you feel this is to far off topic please contact me directly. Thanks very much. Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] NTP REFCLOCK for a Jackson Fury??
Frank, try GPSD on Linux: http://gpsd.berlios.de/hardware.html Bye, Said In a message dated 10/16/2013 14:50:19 Pacific Daylight Time, hp_cisco...@yahoo.com writes: Hi, What NTP REFCLOCK can be used for a Jackson Fury? I know that the Jackson Fury docs suggest using: http://www.realhamradio.com/gpscon-info.htm But that means I would have to put up a windows server to replace the FreeBSD ntpd server I built for use w/ the Trimble TB. Looking for open source options, if possible. Thanks, Frank KJ4OLL ___ ___ 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] GPSDO choices
Paul, try the Jackson Labs GPSTCXO eval kit. Comes with GPS antenna, USB comm/power cable, and board. You can get a Hammond enclosure for it for less than $20, and have a complete desktop system for less than $400 new. Probably the lowest-cost new way to go other than Ebay-used or homemade. bye, Said In a message dated 10/3/2013 20:30:55 Pacific Daylight Time, tic-...@bodosom.net writes: I'm looking for a new, ready to go, inexpensive desktop GPSDO. So far I've only found the Fury and Thunderbolt E. Are there other reasonable choices e.g. the J R Miller (although I'm not sure there's a source of new TU-30 parts). Thanks. -- Paul *Say $2k ___ 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] A readl atomic wristwatch
Guys, there is only one problem: there is just no way they can claim only 1 second error in a 1000 years unless they also have a GPS receiver for calibration in there, which kind of mutes the point as that has been done using wwvb etc. Let's do the math: 1/ (1000 * 365 * 24 *3600) = 3.171E-011 average error required over 1000 years. The CSAC has a thermal spec of +/-0.5ppb for -20C to +70C, meaning 5.6E-012 per Degree C sensitivity. So the temperature would have to stay stable within a couple degrees C, hardly possible in a wrist watch. Also, initial CSAC aging is 0.3ppb per month, about 100x worse than they claimed 1000 year per second accuracy. It gets better over time, but still around a ppb per year or so of aging is expected, far off from the 0.032ppb claim. They did a great job integrating that together, and its novel, but the marketing department is off by many orders in magnitude in their accuracy claims. I know CSAC applications that would be very happy to get around 0.1 second error per year consistently without external re-calibration in a stable environment. bye, Said In a message dated 10/1/2013 15:32:27 Pacific Daylight Time, ma...@non-stop.com.au writes: That's the first time I have seen a practical explanation and working example of a CASC in operation. Can I say Awesome? --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] Clock Driver Design
Hi Tom, yes, the GPSTCXO has a pretty good typical phase noise above 100Hz or so for being just a TCXO, competitive to or even a bit better than some good SC-cut OCXO's. Compare that to the Trimble Mini-T for example which has a noise floor spec of only -145dBc/Hz according to the Trimble datasheet.. But there is a big difference between -73dBc/Hz at 1Hz, and -100dBc/Hz at 1Hz. These are certainly not similar numbers, not remotely.. That's what makes the difference between a low cost TCXO and a high-performance SC-cut double oven OCXO. In fact you can probably expect an OCXO that is specified at -105dBc/Hz at 1Hz to cost twice as much as one specified at only -100dBc/Hz at 10MHz.. There is also some specmanship here, because of the difference between max noise and typical noise. Max noise means all of the units shipped must be at or better than x, typical means the 1-Sigma noise numbers of a number of production units should be at or better than x. Some may be way better, some may be worse. There will be a cost difference between the two for the same number. In terms of signal buffering, I think this thread is sometimes slightly over-complicating the issue, take a handful of fast single CMOS gates especially if you already have a CMOS source, then run them at 5V, and then do some more or less complicated low pass filtering to generate 50 Ohms 10MHz sine waves. You can probably even get some low-cost Mini Circuits BNC type low pass filters of-the-shelf to do the job for you. But layout and power supply design is of critical importance to achieve the best noise performance, I would not use a simple LM78M05 regulator, I would use a low noise LT or Analog Devices unit because any low-frequency 1/f type power supply noise is going to be modulated right onto your signal unless you do a true differential design (way too complicated). With the above mentioned design you can assume to achieve better than -130dBc/Hz noise at 1Hz, and a floor of about -162 to -165dBc/Hz for the amp. That matches the Crystek VCXO performance you will get pretty well. All that said, in my experience there are really few applications where you truly need a -100dBc/Hz at 1Hz noise performance in a radio transceiver, other than for maybe Radar type applications that analyze data down to a 1Hz offset from the carrier.. But this is time nuts after all, so every dB matters. Bye, Said In a message dated 9/26/2013 23:15:16 Pacific Daylight Time, tom_min...@att.net writes: Thanks for all your thoughts on the subject. Let me play back what I have learned and how it may apply to my challenge. One of my first applications is to use a 10MHz output to phaselock a VCXO master clock in a radio transceiver. The VCXO is the Christek CVHD-950 which has a noise floor of -164dBc and is -86dBc at 10Hz. The source I want to use is the Jackson Labs GPSTCXO which has a noise floor of -155dBc and is -73dBc at 1Hz and 103dBc at 10Hz. i did a quick survey of the phase noise specs on various Jackson products that claim to be ultra low phase noise and found similar numbers. One was -100dBc at 1Hz but only -145dBc at 100KHz. Another was down -90dBc at 1Hz and -160dBc at 100KHz. It would appear that even the best parts I could find quickly would not merit the fancy analog gizmo and that a good stiff logic buffer would work. Next I went to IDT to find the best logic buffer I could find. I am looking at the IDT 74FCT38072 2 channel clock driver for PPS. It can drive about 50mA if needed with 1nS rise and fall times. The one I am looking at for 10MHz is the ICS553 4 channel clock driver. This one is good for 25mA drive and they actually give a typical output impedance spec of 20 Ohms. With a 3.3V supply, it has 1nS rise and fall times and a little faster with a 5V supply, 0.7nS and 35mA drive. To make a sine wave should I use one of the 4 ports on the 4 port driver to input to the filter or should I try to hook the filter input directly to the clock driver input? Are there tried and true 10MHz filter circuits or is that a non issue? After the filter would come the video amp set up for a 50 Ohm drive and into a splitter. That sound simple enough. What am I missing? Tom ___ 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] Trimble Resolution T - PPS offset and stability
Hi Bob, it's not +/-100ns on all receivers. Our Fury GPSDO that uses Motorola designed M12M receivers allow +/-1ns antenna delay phase adjustment resolution. No effect on timing stability. Almost all of our other products using uBlox GPS also allow +/-1ns antenna delay phase adjustment resolution. It may take many minutes to track the new phase since typical GPSDO time constants are set for 10's of minutes typically, but once settled, the stability will not be affected by this phase offset. Bye, Said In a message dated 9/2/2013 15:24:01 Pacific Daylight Time, li...@rtty.us writes: Hi On all the GPS's I have tried it on, shifting the PPS has no real impact on stability. A few things to consider: Normally the shift is a few hundred ns either way The shift process is always in steps of the main clock (100 ns for 10 MHz) GPS by it's self bounces around a bit. If you are talking about a shift of a big fraction of a second (and it sounds like you are) then the stability of the GPS's local clock could come into play. On something like a TBolt that's not going to matter. On a TCXO based gizmo that is only corrected to 1.0x10^-7 you could get an extra 50 ns of error at a half second offset. Weather you see that on this or that GPS depends a lot on who wrote the firmware and what they worried about when they did. The better alternative is to use a counter with a reasonable time base to look at the difference between pps signals. If the counter has an OCXO time base and it's properly calibrated you are about 10 to 100X better off than the 50 ns in the example above. Bob On Sep 2, 2013, at 6:05 PM, Lachlan Gunn lach...@twopif.net wrote: Hello. Has anyone here tried varying the PPS offset on a ResT (or UT+ or any other GPS receiver for that matter) and measuring the resulting stability? I ask because my Rb has only a 1PPS output, and while I have been able to get at one of its internal HF signals, would like to see what I can do with just 1PPS. The obvious problem with doing this is that I will need to align the PPS outputs together to get reasonable accuracy, but I worry that a large offset in the GPS receiver will degrade stability as the pulse moves away from the relevant packet in the GPS signal. Am I being over-cautious? Thanks, Lachlan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] B.V.A. 8600 for sale
Here is my experience with trying to get one of these for very low noise ADEV measurements: * waited for some years for one to pop up on Ebay/Time-Nuts/Craigslist etc. I even sent a couple of BVA WANTED emails to time-nuts in the past, no response from anyone. * called the factory, they quoted $10K prices if I remember correctly, out of my budget. * emailed some known BVA owners and asked if they wanted to part with one. No. * asked the factory for demo units, used units, etc. None available. * based on an old email, found one used for similar price, bought it, and happy now I agree, it's much cheaper to get a ULN oscillator from Wenzel for phase noise measurements. Those tend to have not quite as good ADEV though (we have a number of these) and because they drive the crystal with massive power they age like crazy, but they do have very good phase noise. For ADEV measurements, these BVA are great, much better than any Wenzel we have. Potentially better to way better than the 10811. Not many 10811 will perform in the xE-13 level close-in. 10811 also sometimes suffer from crystal jumps, BVA's don't as far as I know due to the nature of the crystal design. If you need great phase noise, simply buy a used Wenzel ULN for a couple of 100 $$ and phase-lock it to the BVA. That way you can get excellent phase noise, and ADEV at the same time. Likely one would do two measurements anyway, one for phase noise and one for ADEV, that way there is no need to phase lock a Wenzel to a BVA. That's the way we do it here - just use different references for different measurements. Those folks that need these and have large budgets (NIST, etc) probably don't care if it costs $300, $3000, or $25K and the factory needs to pay its employees and rent so their asking price is justified versus the small volume they sell. For us other folks having a seller offer these at $3000 is a nice opportunity - if you happen to want exactly this unit. I just wish the seller would rent a Rhode and Schwarz, Symmetricom or other ADEV/PN meter for a week and specify the performance of these units. Bye, Said In a message dated 8/29/2013 10:21:52 Pacific Daylight Time, act...@hotmail.com writes: I could be wrong but I thought when I priced these for work the BVA 8600 AT cut was substantially cheaper then that. I think the $11,000 is more in line with a BVA 8607 SC cut with an option. But from my point of view the close in Phase Noise on this particular oscillator is what dictates it's value. These BVA 8600's typically range from 110 to better then 120 dB @ 1Hz which is a big difference. If this BVA is at the low phase noise end of the range it could be a real bargain at $3000. Another option in the $3000 range is the Wenzel Blue Top ULPN oscillators. It may not match a good BVA inside 1Hz but will have at least a 20dB better noise floor from about 10KHz out. The other plus with a BVA is the the Quartz is capacitive coupled where most other oscillators have metal deposited directly on the Quartz which will interact over time and potentially diminish performance. As Tom and other explained prices go up exponentially for ULPN oscillators. Thomas Knox Date: Thu, 29 Aug 2013 12:53:47 -0400 From: paulsw...@gmail.com To: time-nuts@febo.com Subject: Re: [time-nuts] B.V.A. 8600 for sale OK but like a new car the value drops 50% off the lot. Anyway you slice it as nice as this might be I will stick with the $100 and less 10544/1081s 105s and sulzers. I may be a time-nut. But I am not time-Nutz. Perhaps for the lab that need it that is a darned good price. Regards Paul WB8TSL/1 On Thu, Aug 29, 2013 at 11:39 AM, Said Jackson saidj...@aol.com wrote: Yup, I heard price goes up from there... Sent From iPhone On Aug 29, 2013, at 8:37, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 572a741b-0213-4f1c-ba59-c2d396a03...@aol.com, Said Jackson writes: These are about $11,000 or so new if I am not mistaken. Depends what options it has... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts 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
Re: [time-nuts] Neat little cesium box
Greg, the only power source I am aware off that can provide the ~5W power required by that Novus box for 10-12 years with 20lbs weight limit without any external power sources or maintenance is a radioisotope thermoelectric generator (RTG) such as those used on Spacecraft. The Russians used to use those also in light houses. Maybe the atomic decay could be counted and used for improving timing some how?! That said the radiation would probably have a very negative effect on any electronics near it for long-term stability. I would also not call that solution disposable anywhere on earth. Definitely not hobby level stuff.. bye, Said In a message dated 6/13/2013 17:15:45 Pacific Daylight Time, engineer...@mt.net writes: Tom, Thank you for your concern. I unfortunately cannot disclose many details about the proposed project only to say that the application transcends much of the typical Time-Nuts areas of normality. At present we are evaluating typical frequency references to see if they will fit into this project. What I can say is that phase noise is of little interest but log-term frequency drift is. The completed unit will unfortunately not see GPS signals during most of its lifetime, be constrained to a weight not exceeding 20 lbs, be considered non-recoverable (disposable) due to areas of deployment thereby require a relatively cost-conscious design, have no access to a source of power let alone any natural power-producing resources and have an expected lifetime of 10-12 years without maintenance access. Most of the problems have been solved including the power source. This is not your typical kitchen table project. And, as new frequency references are developed and the design feasibility phase is still open, small and minimal power-consuming products such as the Novus unit will garner our attention. Thanks for your offer, Greg ___ 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] HP53132A vs SR625
Ed, the calculation is the same, however the numbers are 100ps for 53132A versus 350ps, and I have not seen an average systemic offset being displayed on any of the 3x 53132A units I use, and I see one on the SR-620. That's why I sent it into SRS for calibration, paid the $$$ and got it back with the same exact offset and a statement that it is operating within specifications so no adjustment is necessary. HP manages to show zero error on average, with the digits bouncing back and forth. The SRS unit manages to show a hard frequency offset. If I remember correctly the SR-620 even shows this offset with it's own reference connected to the inputs, the HP does not. bye, Said In a message dated 3/17/2013 11:26:16 Pacific Daylight Time, ed_pal...@sasktel.net writes: Hi Said, That equation looks similar in form to the specs for any counter. What are the comparable equations for the 53132A or the 5370(A or B)? 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] HP53132A vs SR625
Hi Volker, there are some issues here, first the worst case frequency systematic uncertainty is 100ps for the 53132A, not 350ps as on the SRS unit or 500ps as you stated. So they are not the same, they are 3.5x different. From the Agilent manual: Systematic Uncertainty: Agilent 53131A Agilent 53132A tacc tacc typical 100 ps 10 ps worst case 300 ps 100 ps Notice the 10ps typical error, and 100ps worst case error. That compares to a 100ps typical error for the SR-620 or 10x worse typically than the 53132A. So we get 10x worse typically, and 3.5x less for the worst case - in my opinion these units are not even in the same class. Now for practical matters, I just measured the SR-620 we have with a randomly selected 53132A. Both connected to their own reference input. 2-second samples on both, and here are the results: The SR-620 shows a frequency error of -0.00203Hz consistently.That's 2.03E-010. Within its specifications but making the unit useless to me. The 53132A showed an error of only 2E-012 to 8E-012. So about 25x better accuracy! And the 53132A is showing 12 digits on the front panel as well for 2 second gate times at 10MHz. Nor does it require time-consuming and error prone and annoying internal adjustments to achieve this. What's even more damming for the SRS unit: as I increased the sample size (1s gate time is the max front panel selection, so I had to increase sample size instead of gate time) the error stayed persistent independent of sample size or thus measurement length. On the HP unit however, increasing the gate time made the error get smaller and smaller, and at 10+ seconds gate time I got 13 digits of resolution out of the unit, and an error of only 1E-012 at that point. So in summary, the SR-620 requires careful user adjustment of internal adjustment points. I don't have time to do that, so sent it in and paid the $600+ or so (if I remember correctly) for the standard calibration fee they charge. I got a unit back with the error unchanged, which was the original reason I sent it in to them in the first place. An error of 2E-010 makes the unit useless as we are in need of measuring xE-011 accurately. If I had time to learn how to calibrate the unit myself, I may do so, but even then you showed a 2E-011 error on your carefully adjusted unit, whereas I measured a 2 to 8E-012 error on a random non-adjusted 53132A unit here. Still about 3x to 10x difference in performance. If someone is interested in a swap of a working 53132A with input-c option for our SR-620 I would like to talk to you offline. I would even throw-in an FEI Rubidium reference in that swap, even though the SRS' sell for about $2300, and the 53132A'a go for about $1400. bye, Said In a message dated 3/17/2013 13:02:46 Pacific Daylight Time, ail...@t-online.de writes: I just powered on my SR and looked for the offset, when the 10 MHz reference is connected to the input (at a gate time of 1s without further averaging). It shows an offset of 0 to 400uHz which should represent a mean error of 2E-11, while the manual predicts an error of about 1E-10 (as Said told us, and as my manual tells me). That's within the spec. Unfortunately I don't have a 53132, but the manual of the HP predicts an error of E-10 - just the same value as with the SR. ___ 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] Z3805A/58503A time receiver : 2 questions
Hello Claude, that gap is a classic crystal jump. It could be caused by the crystal changing frequency by itself, or by being hit with e.g. gamma particles etc. Could also have been instigated by vibration or shock to the unit. You should be seeing 6+ sats at all times though, your plot shows you sometimes seem to see 2 or 3 sats only? Maybe a better antenna position would help the stability of that unit. Nothing to worry about if it doesn't happen regularly. Enjoy, bye, Said In a message dated 2/27/2013 15:18:51 Pacific Standard Time, lab...@yahoo.fr writes: Hello, This is my first message here although I read this list for a few weeks. I bought a Z3805A/58503A frequency receiver and I didn't notice on the pictures that the model number was not written on the front panel. It's not important but is there a reason for that, if you know ? The item : http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItemitem=251226027893 I log some parameters of the receiver and today I notice a gap in the frequency. Picture : http://uppix.net/e/2/4/cf39ac772e5a69fc616f5cf30f208.png I have a Rubidium and I measure it's frequency with a 5334B counter locked to the GPS, and I can see the gap too : http://uppix.net/f/b/a/d86c2737ad135264e4a2b78e503d5.png measurements are with Gate Time of 10s, 60s and 100s, Do you know why this happens and how to prevent this behaviour ? Thanks for yours advices Claude ___ 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] HP53132A vs SR625
Hui, rent one of each if you can before you make your choice. I have both, and the HP unit is much easier to use once you know which button sequence to push to get more than just Frequency/Time-Interval type measurements - these can be single-button events on the HP unit. Even offsetting and normalizing frequencies becomes very easy after a couple of days of using the unit, there is no setting that takes me longer than about 5 seconds to set up, so while not perfect, the user interface can be learned easily. I find the SR620 to have too many buttons(!) I always find myself searching for just that one button. Anyways, more buttons are just more things that can fail. If you are a pilot, and have used a Garmin 430W GPS in your life, then the HP user interface is no challenge whatsoever and seems very easy to use.. The SR-620 has it's advantages, especially when you just do one single type of measurement, but for me it has a huge number of disadvantages, and I mostly use the 53132A for that reason: 1) I paid quite a bit of money and I had it calibrated and fixed by SRS, and it still exhibits a significant frequency offset with a perfect reference and perfect DUT!!! SRS says a small frequency error is normal, well that prevents me from using the unit as a frequency counter, for me it's only useful as a relative display frequency counter. HP doesn't have such a frequency error, so no worries there. 2) The SRS unit is s loud that it's totally annoying and unacceptable for long measurements. Many folks reported this here before. It's just bad. Whining like crazy. 3) The SRS unit is 19 wide, huge, heavy, and clunky. I need my counter portable, only the HP unit will do 4) The SRS unit has a much lower MTBF because of all the parts inside, and it needs finicky adjustments, see item 1) above. The HP unit either works, or is just dead. Not much to adjust. Different technology generation. And the coolness factor: a nice florescent tube display is so much more modern looking than those clunky old 7-segment LED's.. 5) The SRS unit is usually $1000 more than the HP unit, and you don't know how good the unit is you are buying because of all of the calibration stuff. Usually there is no hit-or-miss issue with the HP units, they either work, or are dead. That said, the HP unit doesn't measure well at 10MHz, so I mostly use a divide-by-two to get one more digit of resolution out of it, and it's time interval resolution is not as good as the SR620. But for time interval measurements I use a Wavecrest DTS unit that blows the SR620 and the HP out of the water anyways.. Bye, Said In a message dated 2/7/2013 16:39:04 Pacific Standard Time, ba...@163.com writes: Hello Dear Group: I am very glad to see so many replies in the morning, and I am very grateful to every time nuts gave me useful information, your proposal has strengthened my determination, in fact, I am also very like SR625, So I will to find and buy a good shape SR625 for my new time interval measure instrument. Thanks again for everyone's advice, which is very useful to make a choice for me. Sorry for not reply everyone's mail. Best Regards! Hui Zhang ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Low noise power supplies?
Not sure if anyone posted this here yet, but Abracom has a very low noise (7nV/RtHz at 1KHz) power source for VCO's etc, with various outputs. It's sold on DIgikey or Mouser I think. Here is a review of that unit: _http://jaunty-electronics.com/blog/category/reviews/_ (http://jaunty-electronics.com/blog/category/reviews/) Co-incidentally he also has a review of one of our units on the same page. This is a very handy and reasonably priced power supply for many low-noise type of experiments. bye, Said In a message dated 1/30/2013 21:36:50 Pacific Standard Time, bruce.griffi...@xtra.co.nz writes: Lester Veenstra wrote: The typical test supply on a bench for clean VCO testing is a small gel cell battery. For a regulated power supply, make one using a 723. The 723 has far lower noise out than the monolithic regulators. Depends on the variety of 723 some are noisier than others. Some use an internal zener reference, some use a bandgap reference. The original used a zener reference. Bruce Lester B Veenstra MØYCM K1YCM W8YCM les...@veenstras.com US Postal Address: 5 Shrine Club Drive HC84 Box 89C Keyser WV 26726 GPS: 39.33675 N 78.9823527 W Telephones: Home:+1-304-289-6057 US cell +1-304-790-9192 UK cell +44-(0)7849-248-749 Guam Cell: +1-671-929-8141 Jamaica: +1-876-456-8898 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard (Rick) Karlquist Sent: Wednesday, January 30, 2013 9:17 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Low noise power supplies? I know this topic has been discussed in the past on the list, but a colleague is asking if there are any off the shelf low noise power supplies for testing oscillators. Something a cut above an HP brick lab power supply etc. They are hoping to avoid having to homebrew a power conditioning circuit. Did we ever arrive at a concensus as to the state of the art in homebrew power conditioning circuits? Any help would be appreciated. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] GPS at 60,000 feet
I think it's supposed to work up there. Cocom limits used to be 50,000 feet and 1000 knots if I am not mistaken. Most GPS will likely support those Cocom limits even if they state something like 2000 meters max altitude etc. A commercial flight should certainly work, besides the problem of only seeing one side of the sky on the plane.. bye, Said In a message dated 1/31/2013 05:31:39 Pacific Standard Time, d...@irtelemetrics.com writes: I know for sure my handheld Garmin works at 27000 feet, at 530mph... ...I was actually surprised it worked up there. It made me wonder what the actual limits are. On 1/30/2013 12:00 PM, time-nuts-requ...@febo.com wrote: How to check if a GPS works at 60,000 feet: send up a balloon: ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Low noise power supplies?
Or a good battery as a source for the regulators as discussed in this thread already. It's quite nice to have all the different Voltages available at the same time, with up to 200mA. bye, Said In a message dated 1/31/2013 13:12:33 Pacific Standard Time, li...@rtty.us writes: Hi For $393.75 does it come with a wall wart? If not I would definitely go for a medical ground isolated / low leakage version to power the beast. The added cost over a plain jane wall wart won't add much to the purchase price percentage wise. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of saidj...@aol.com Sent: Thursday, January 31, 2013 3:58 PM To: time-nuts@febo.com; les...@veenstras.com Subject: Re: [time-nuts] Low noise power supplies? Not sure if anyone posted this here yet, but Abracom has a very low noise (7nV/RtHz at 1KHz) power source for VCO's etc, with various outputs. It's sold on DIgikey or Mouser I think. Here is a review of that unit: _http://jaunty-electronics.com/blog/category/reviews/_ (http://jaunty-electronics.com/blog/category/reviews/) Co-incidentally he also has a review of one of our units on the same page. This is a very handy and reasonably priced power supply for many low-noise type of experiments. bye, Said In a message dated 1/30/2013 21:36:50 Pacific Standard Time, bruce.griffi...@xtra.co.nz writes: Lester Veenstra wrote: The typical test supply on a bench for clean VCO testing is a small gel cell battery. For a regulated power supply, make one using a 723. The 723 has far lower noise out than the monolithic regulators. Depends on the variety of 723 some are noisier than others. Some use an internal zener reference, some use a bandgap reference. The original used a zener reference. Bruce Lester B Veenstra MØYCM K1YCM W8YCM les...@veenstras.com US Postal Address: 5 Shrine Club Drive HC84 Box 89C Keyser WV 26726 GPS: 39.33675 N 78.9823527 W Telephones: Home:+1-304-289-6057 US cell +1-304-790-9192 UK cell +44-(0)7849-248-749 Guam Cell: +1-671-929-8141 Jamaica: +1-876-456-8898 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard (Rick) Karlquist Sent: Wednesday, January 30, 2013 9:17 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Low noise power supplies? I know this topic has been discussed in the past on the list, but a colleague is asking if there are any off the shelf low noise power supplies for testing oscillators. Something a cut above an HP brick lab power supply etc. They are hoping to avoid having to homebrew a power conditioning circuit. Did we ever arrive at a concensus as to the state of the art in homebrew power conditioning circuits? Any help would be appreciated. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS at 60,000 feet
How to check if a GPS works at 60,000 feet: send up a balloon: The good folks at Duke University sent a uBlox based GPSTCXO up there, and it worked at max balloon altitude which was about 60,000 feet. The ambient temperature must have been around -50C up there, and maybe down to -67C during the ascent, but probably higher inside the electronics box due to insulation and self heating etc: _http://lightningballoon.blogspot.com/_ (http://lightningballoon.blogspot.com/) Note that this is higher than the older GPS would support, due to the new Wassenaar speed/altitude limits. bye, Said ___ 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] NMEA Software
Not sure if these were properly answered yet, but the ublox Windows application is a great way to dissect most any NMEA sentence into all it's components, check for consistency, graph stuff, and check for PVT info. We use it with anything that generates NMEA sentences, it works great. Of course it also has a bunch of uBlox specific features, but it is a nice generic NMEA cruncher as well. bye, Said In a message dated 12/20/2012 14:06:13 Pacific Standard Time, rich...@karlquist.com writes: I have an Outback S-Lite tractor GPS with a serial port with NMEA. Is there ready-to-use software to read out in lat/long from this port? Maybe I can talk to it with hyperterminal and make it just keep sending lat/long once per second or something. Is there a command set? I'd like to use this for laying out antennas, etc. (ie surveying). Rick Karlquist N6RK Martyn Smith wrote: Hi, Apologies if this has been asked 1000 times before. Is there any good software for reading the NMEA or Motorola binary code out of a M12M. I have winoncore, but wondered if there was anything a bit more modern. Regards Martyn ___ 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] Z3805A cooling requirements?
Wish I had more time to play with this setup. How about fellow time nuts spend some time and present similar test data on their OCXO's to compare? I was interested in the 1s to 100s ADEV, and my runs were from 8 minutes to 20 minutes, certainly enough time to capture data for 1s to 100s ADEV measurements.. bye, Said In a message dated 12/20/2012 14:17:59 Pacific Standard Time, mag...@rubidium.dyndns.org writes: On 12/20/2012 01:34 PM, Bob Camp wrote: Hi Temperature transients are not a good thing for an OCXO. If you deliberately use the fan to create a transient, then yes the OCXO will not be happy. The question it - what happens after the transient has settled out? The plot you have still looks a lot like a step function. I agree. Temperature steps stresses the OCXO oven loop and easily creates a gradient over the crystal. As the oven loop tracks in, the frequency returns to around normal. The trouble with forced air over a crystal is that the metal shield couples very well and acts like a heat sink. A think plastic cover over it and forced convection doesn't have the same effect. There is even being used by at least one vendor. Works very well for the extra cents of manufacturing cost. The HP10811 is recommended to be put in a airflow-quiet corner of the world. Look at it's mounting in the HP5370A/B for instance. 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] Z3805A cooling requirements?
Not sure about that, if you look at the frequency plot after ~20 minutes in moving air the frequency was still extremely close to 10.00MHz.. to within 1E-011 of 10MHz. This is a free-running 10811. Compare that to the plot of the OCXO I had sent out some hours ago when it was running stable inside the foil - there was almost no average frequency change between the two tests. If the heaters had an issue keeping average crystal temperature stable, then the frequency would have changed from the first plot to the last plot I would think. In my opinion the airflow is just adding a huge bunch of heater control loop noise to the output stability, or there are components on the PCB which are very sensitive to the airlfow. Consider that this unit and it's PCB was designed to live inside the 53132A (very close to the fan) that I am now using as an air source. One thing this tells me: the fan in the counter could be disabled and it would improve the units stability, if one keeps an eye on internal counter temperature. bye, Said In a message dated 12/19/2012 18:42:08 Pacific Standard Time, act...@hotmail.com writes: I think the data shows that the heaters were losing ground, which would explain the steadily falling temp of the SC cut quartz. Thomas Knox ___ 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] Comparing PPS from 2 GPS units
Hi Tom, but they could have achieved the same exact result by using scientific notation such as: 2.3E-010 or: 2.30E-010 or: 23E-011 to note the higher internal resolution in the later case. I realize that one can easily parse these raw outputs, if one can write python or C etc quickly, but I always find myself doing search and replace: '* u' with '0E-06 in Word etc.. Also I don't happen to have a 1us long and accurate delay line, and I have to measure two pulses very close to each other, so I have no real choice in the matter at this time. The jitter can be up to +/-1us, so I need that 1us delay to keep the values positive. It would be good if the programmers would have added options to select the output format, and how to count time intervals close to zero when going negative. This should have been very easy to add in the counter's software. Maybe there is a Windows executable out there that can parse raw 53132A counter log files, recognize what the data is, and turn them into proper scientific notation as well as handling the 0.999,999,999 second issue, that can then be directly read by programs such as Excel, Plotter, etc? Time-Nuts, anyone willing to write this for the benefit of all? bye, Said In a message dated 12/13/2012 22:55:42 Pacific Standard Time, t...@leapsecond.com writes: Absolutely horrible to parse, these guys should have heard of scientific notation. Not sure who programmed that unit, or if there is a firmware upgrade that gives proper numbers. They are more proper than you think. Do you remember one of the first lessons in high-school science class: scientific measurements have both value and precision. Thus 2.3 is not the same as 2.30 which is not the same as 2.300. Precision is important. When the 53132A adds * it conveys to the user that precision is missing. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Comparing PPS from 2 GPS units
Hi anonymous, the 53132A only does that for a couple of nanoseconds. Then it jumps to a stupid value such as: 0.004 us -0.002 us 0.999,999,993 s It get's even better when the counter decides it doesn't have enough resolution in frequency mode: 2,3** u Absolutely horrible to parse, these guys should have heard of scientific notation. Not sure who programmed that unit, or if there is a firmware upgrade that gives proper numbers. bye, Said In a message dated 12/13/2012 15:07:50 Pacific Standard Time, timen...@triplespark.net writes: Counters like the Agilent 53230 actually WILL output negative delays in this case as long as the delta is still small. This is a quite useful feature in such cases... ___ 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] Z3805A cooling requirements?
Stu, a fan is about the worst thing you can do for your Z3805 it will significantly worsen the stability of the output frequency. The oven inside does get warm, that's why it is an oven :) The power consumption will go down once it heats itself up, the unit is designed to work without a fan sitting on a desk etc. Just make sure the vent holes are not clogged. Sounds like your Z3816 had a failure that caused the units power supply to overheat. bye, Said In a message dated 12/11/2012 16:22:10 Pacific Standard Time, stewart.c...@gmail.com writes: This may be a newbie question, but I'm a newbie, so: Do the HP telecom GPSDOs (Z38xx) require external airflow for cooling? They don't have built-in fans, but they sorta look like they depend on a rack-level cooling fan, which a telecom rack would almost certainly have. I ask because I bought a Z3816 awhile back which worked for about a week and then failed. I traced the failure to an internal power supply brick, which had a big finned heat-sink attached but nevertheless smelled overheated and was shorted internally. I never found a replacement power brick, and I don't have time to mess with it right now, so I recently bought a Z3805A. It, too, looks like it's working, but it started to feel awfully warm after a few hours, so I unplugged it for now. It probably wouldn't take much of a fan to bring the internal temperature down close to ambient, and the fan could be powered easily enough from the supply rails. But that might create a temperature gradient where the designers didn't intend one. Or it might cause problems I don't even know about yet. At the moment, the Z3805A is in a fan-less 19-inch rack with a bunch of other equipment, in a lab environment. Should it have its own fan? 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] Thunderbolt oven / non-stable operating temperature
Hello Tom, the GPS noise dominates for typical double oven OCXO's where the tempcos are very small (say below 5E-012 per degree C). On single oven units, the tempcos are typically 50 to 200 times larger, and thus the required EFC change over temperature is also that much larger. If I am not mistaken Thunderbolts have double oven units, and Mini-T's have single oven units? That EFC change can only be done through either prediction (sensing temperature and applying a correction factor) or through generating a phase error that feeds through the loop system. Crystal aging also typically requires a constant phase error which will in turn create a constant change in EFC voltage to correct for aging until active aging compensation can measure and apply this change in EFC. The magnitude of this phase error typically depends on the loop gain and the rate of change of the crystal frequency over time. In summary, we see fairly significant improvements in single oven systems with active compensation even during GPS reception, and we don't see much improvement in double oven units for temperature, but similar improvements for double oven units on aging. Now double oven units typically have SC-cut crystals, and single oven units typically have AT-cut crystals where the AT cuts typically have larger aging and retrace than SC cut crystals, so that can skew the performance in favor of double oven units as well. Bye, Said In a message dated 12/11/2012 19:41:58 Pacific Standard Time, warrensjmail-...@yahoo.com writes: I agree this is true in theory (where epsilon != zero), but it's hard for me to believe true in practice. I would guess the error term is totally dominated by short-term GPS noise, and anything else, like tempco or frequency drift, is secondary. That's why it makes sense to apply these 2nd or 3rd order corrections during hold-over mode (where there is no GPS noise) but not for normal operation. So what does this mean for the average Nut's Tbolt? Mostly nothing. The only time the temperature sensor has any effect is during holdover. Thanks for stating both these facts so clearly. I cringe every time I hear someone replacing a 1C DS1620 sensor in their TBolt. The TAPR TBolts I tested years ago worked equally well regardless if they were 1C TBolts or ten milli-C TBolts. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO Alternatives
David, The NXP LPC932 processor series are very cheap and small, and we got very excited to see timers running at up to 32MHz internally if I remember correctly. Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. DAA. So all that fast timer resolution goes out the door by gating the input pin instead of using non-gated inputs for the timer functions. It does work however, in the end we made that processor do the chores in our quite old and discontinued FireFox GPSDO circuit. TVB has some plots on his website for that unit I think, and its quite surprising what type of stability we achieved with that little 8 bit bugger back then. bye, Said In a message dated 12/6/2012 16:00:27 Pacific Standard Time, davidwh...@gmail.com writes: You can use the ATmega328 16 bit timer/counter in input capture mode to count the number of 10 MHz OCXO cycles per pulse per second period to a resolution of 100ns but there are some problems: The ATmega328 16 bit timer/counter external clock is limited to 1/4 of the CPU frequency with an asynchronous source so the 10 MHz OCXO would need to be divided down which would further limit performance and require an external divider. Modifying the Aruino board to use the 10 MHz OCXO in place of the CPU clock solves that problem. Then operating the counter/timer in input capture mode with the GPS pulse per second signal connected to the input capture pin would allow almost Shera like performance. The timing resolution would be 2.4 times lower (and not asynchronous) limiting performance over short time spans. ___ 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] GPSDO Alternatives
Hello, metastability is not an issue in this type of application, nor can it be avoided since we have two different clock domains. It would only shift the capture point by one counter clock cycle back or forth if the edge happens right on the transition point. At that point we have 50% uncertainty where it should fall anyway's, so the best one could do is switch back and forth between the two counter values creating an average of half way between these two counter points! Also the GPS sawtooth will create enough jitter on the capture pin to avoid staying in metastability for more than one pulse. Metastability is an issue for applications that need to be bit-accurate, such as trying to capture a serial datastream etc. A 1PPS capture application in a GPSDO is not a bit-accurate affair, it is a heavily averaged (low pass filtered) system so statistics kick in. The real problem of the LPC932 capture system is that the resolution goes from 33ns on the counter to something around 200ns because of the pin clocking the input FF at 5MHz... its a waste of possible resolution on that chip. 200ns is quite a low resolution for a GPSDO, but there are ways to improve this resolution through dithering for example. bye, Said In a message dated 12/6/2012 20:35:35 Pacific Standard Time, hmur...@megapathdsl.net writes: saidj...@aol.com said: Then setting up a test system we noted that the timer can capture with 32MHz resolution which is good enough for a low-cost GPSDO implementation, but that they gated the input pin through a flip-flop running at CPU core speed, which was around 6MHz if I remember correctly. davidwh...@gmail.com said: The ATmega328 apparently has something similar going on since the datasheet says that the maximum external asynchronous clock frequency is 1/4 of the CPU frequency. That is why I suggested synchronously clocking the CPU directly from the OCXO. Atmel's datasheet is annoyingly vague about some matters and I assume the capture input works like it should. You have to do something appropriate when multiple clocks are involved or you get metastability issues. I think the 1/4 limit is to allow the external pin to be used to clock the counter. If you run the external signal through the standard pair of FFs to get a signal that is synchronous to your clock, 1/4 guarantees that you will see all transitions. At 1/2, with the duty cycle slightly off 50-50, you might end up with hanging-bridge type cases where the output of the synchronizer always sees the same level. Actually, metastability is hard to hit. Most metastability issues are really just setup/hold bugs. ___ 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] GPSDO Alternatives
Good list Bob, many people underestimate what it takes to make a working, commercial GPSDO, especially one that has to perform in volume and beyond a single well taken care of unit in a Ham shack. Once you have taken care of items 1) and 2), the real work begins. This is where our customers get confused some times, they think items 1) and 2) are easy to do, and all that needs to be done to make a working product, and they try themselves. We just had someone try connecting the CSAC to a GPS receiver themselves, and in their setup they spent two months trying to get it to work before they gave up. The GPS behaved such that the CSAC could not lock onto it reliably. This happens quite often because at first sight it looks simple to do, and folks like Shera have come up with solutions that are simple and work well, but don't have any bells or whistles. One item often overlooked for example is that every OCXO during a production run behaves very differently from the OCXO next to it. The retrace time is different. The tempco is different. The EFC sensitivity is specified in large ranges such as 1ppm to 10ppm, one crystal may jump, another may have EFC hysterisis etc, and the software/hardware has to be able to handle all of these variations without requiring every unit to be fine-tuned by hand during production. And then the OCXO will actually change it's behavior over time due to aging and deminishing retrace error as the unit is operated etc. It's surprising that we still find room to make major improvements to our software 5 years after we sold the first Fury, for example we recently added things like leapsecond prediction/compensation without having an almanac loaded yet, with the help of a time-nut we found a very obscure bug in the NXP ARM processor that was supposed to be fixed years ago but wasn't, and we continuously keep improving and fine-tuning our algorithms and adding more commands/features to it. If there is one thing I learned, it is that one is never finished improving the software. That is why we are time-nuts I guess. bye, Said In a message dated 12/5/2012 09:29:14 Pacific Standard Time, li...@rtty.us writes: Hi If the intent is to come up with something in the same league as the TBolt there are a few other things you will need: 1) Something to compare the two pps signals to within 0.1 ns. 2) A large amount of code on the control processor (there are a multitude of special cases ...) 3) A large amount of code on a PC to monitor it and control it (like Lady Heather) 4) A set of standards to compare it to while you train and debug it 5) The test gear to collect and analyze the comparison and debug data with (you will have many months of data) 6) Some sort of control over the feature list. The complexity of 2-5 will go up significantly each time a nice to have thing is added. Once you get past step one, the rest of that list dwarf's anything like which D/A to use. I'm not at all saying it can't be done. Only that the bulk of the effort starts after you have the hardware. Bob ___ 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] Very challenging phase noise measurement, does anyone have an...
Hans, would mixing your 125KHz with a 2.5MHz or 5MHz low noise reference to get it into a range that the analyzer can read work? You could use a system like the Miles timepod phase noise analyzer, a mixer, a 5MHz low-noise reference, and a low-pass filter to make use of the 500KHz lower range of the timepod. You could divide your 5MHz reference by 2 to get 2.5MHz +/-125KHz, with a 2.5MHz carrier being easier to filter out one of the two side-bands with a high/low-pass or notch filter? Maybe the FSUP itself could be used to remove one of the sidebands and the 2,5MHz carrier, and analyzer the remaining side-band? bye, Said In a message dated 12/5/2012 13:27:28 Pacific Standard Time, azelio.bori...@screen.it writes: Isn't the FSUP a 110K euros equipment 20Hz-50GHz capable? 125KHz shouldn't be a problem. I had an FSUP for 25 seconds to play with... really impressive but too limited test time to appreciate fully. On Wed, Dec 5, 2012 at 1:14 PM, Bob Camp li...@rtty.us wrote: Hi Just about any of the high speed CMOS parts should work. A 74AC86 is about the earliest part I would trust. Any of the fast logic families that came after that should do equally well. Bob On Dec 5, 2012, at 7:03 AM, Hans Rosenberg hrosenb...@catena.nl wrote: Hello Time-nuts, I have to do a phase noise measurement and I'm wondering if anyone here has any ideas on that. We have to measure the phase noise of a 125kHz carrier (5Vp-p signal level). The measurement system should have a noise floor that is -164dBc/Hz at a distance of 1kHz to 8kHz away from the carrier. Our current plan is to use 2 of these sources, have one in free running mode and lock the other one to the first one using an XOR gate and then use the output of the XOR gate as an output signal. However, we are wondering if any of you know a better idea. Maybe there is an off-the-shelf piece of equipment that can do that that we could rent. Or maybe we could increase the frequency to a few megahertz using a pll, which means the signal comes into the measurement range of our FSUP phase-noise analyzer. Problem is, the phase detector would then need to have an insanely low noise-floor (in our idea the XOR also has to have this insanely low noise floor as well off course) so does anyone have experience with anything like this? Does anyone know an XOR with these good specs? I don't have a clue what a standard 74lvc1g86 would do. Needless to say the supply of this XOR would have to be ridiculously clean, but I do have a solution for that problem. Any help is greatly appreciated! Best regards, Hans Rosenberg ___ 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] PTTI 2012
Hi Tom, there are two that sound very interesting: the M12/uBlox one and the Time-Nuts one :) Do you have any other info, or could you give us a 1 minute overview of what was shown please? I also heard that there were scheduled to be more CSAC type papers, but they did not get DARPA approval for publishing in time (no pun intended). Those hopefully will be published at a later date. Thanks, Said In a message dated 12/1/2012 17:10:27 Pacific Standard Time, t...@leapsecond.com writes: - Neutrino time-of-flight update - UTCr/Rapid UTC - USNO rubidium fountains - WWVB/Xtendwave - Loran/UrsaNav - Vendor presentations/Symmetricom/Miles - M12/uBlox GPS board - Quartz in space - ION/PTTI 2013 in Bellevue, WA (!) - The state of Time-Nuts /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] pulse height
Didier, Oh, ok that makes sense, but that is a non-standard output, so not sure that you want to use such an output as a sample case for generic applications. Alternatively maybe rename the page to Trimble CMOS-output Coax Cable Impedance Matching to make that clear. It would be better to put a 45 Ohms series resistor in that system to give you a 50 Ohms standard output, and redo the tests. BTW: we have had to put up with that (in my opinion) stupid output impedance, on our Mini-JLT boards we are also driving the 1PPS with very low impedance to be compatible to the discontinued Mini-T. I wish Trimble had heard of incident-wave switching when they designed all of their units, and used a proper 50 Ohms output impedance. bye, Said In a message dated 11/26/2012 11:12:32 Pacific Standard Time, shali...@gmail.com writes: Said, in the text I indicated the source was not a 50 ohm terminated signal generator, but the 1 pps output of a Thunderbolt with about 5 ohm impedance, hence the ringing. Didier ___ 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] pulse height
Hi Didier, yes, if you put a 50 Ohm termination at the far end all looks good, but you are still driving a 91mA DC current through the cable during the high times, and that will have rippling effects on the driver board by loading the 5V power supply down with a 1Hz period. And if you forget to switch on the 50 Ohms end-termination, you get ~10V as shown in your plots, and you might just blow up your expensive instrument :) One reason I don't like fast edges being driven by 50 Ohms series resistance. Also, if you use 50 Ohms series termination, AND 50 Ohms end-termination, you still get a 2.5V pulse, enough voltage to cleanly switch most of today's logic inputs (either TTL or 3.3V LVCMOS). There are just so many things wrong with the 5 Ohms termination, for example what happens if you short that output to ground? What happens if you feed a parasitic pulse into the line, say from a nearby lightning strike or EMI or ESD event etc? With proper 50 Ohms series termination the pulse should simply be absorbed if it is not unreasonably high and the resistor is large enough. With 5 Ohms, the driver will likely fly off the PCB.. In terms of the incident wave switching issue that Hal mentioned, the wave will stay at about 2.5V for a while, then go to 5V, - again enough voltage to switch TTL and LVCMOS logic inputs cleanly. But then again it is never a good idea to daisy-chain inputs via BNC-T's anyway's. bye, Said In a message dated 11/26/2012 13:11:21 Pacific Standard Time, shali...@gmail.com writes: Said, I agree. I intended to complete the page by doing more tests, but the interesting point of the demonstration is that it is sufficient to match the cable at the far end, and in doing so, you preserve the full amplitude of the pulse. If you put 45 ohms in series and terminate in 50 ohms at the other end, you end up with half the signal. However you do not need to do that. That was the reason why I wrote the page in the first place. I will try to clarify that when I get a chance. Didier ___ 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] Wavecrest DTS 2077 Service Manual?
There is one calibration that can only be started by a GPIB command. I ran into that, my unit constantly said something like xxx calibration required or similar during power on. No way to do it with the front panel buttons. It is easy to start that cal using Visi, or via sending a GPIB command if I remember correctly. Unfortunately I lost my Visi CD.. bye, Said In a message dated 11/19/2012 01:47:55 Pacific Standard Time, h...@deriesp.demon.nl writes: Hi, The Wavecrest DTS 207X has a number of proms and also battery back-up devices. I think it will be wise to check these first. Or are you sure that it is hardware? How old is your DTS? Henk In the meantime I heard that Wavecrest is not distributing service manuals. All repair is depot.repair. This makes me considering if I should take the chance on a second unit, hoping to get one working out of two, or simply to give up and accept that these boxes are only intended to be used as door stops of land fill once defective... I've never been confronted with such a poor customer sevice attitude before. Nevertheless... is there anyone who has acquired some experience with the DTS-series innards who would be willing to share his knowledge? Adrian Adrian schrieb: Anyone have a Wavecrest DTS 2075/77/79 service manual? I've recently got a DTS 2077 that however turned out to be defective. There was a power supply failure that I could fix, but there is still a power-up selftest error message and calibratin fails. Adrian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS receiver testing
John, thanks for your email, I am replying to Time Nuts as well as there is a lot of knowledgeable folks here that can help. In terms of a GPSDO tutorial, take a look at the HP papers linked on the JLT website under the Links Of Interest and Related Whitepaper sections: _http://www.jackson-labs.com/index.php/support_ (http://www.jackson-labs.com/index.php/support) In terms of how to measure the 1PPS accuracy and how to set up the equipment, see the paper labeled Critical evaluation of the Motorola M12+ receiver on that page. Explains how to set up the Agilent counter I mention below. There is a lot of threads in the time nuts archives discussing the pro's and con's of different equipment, but let me give you a quick guide to what worked well for me: For 1PPS measurements and frequency stability down to the ~2E-010 level per second you can get a low-cost Agilent 53132A counter. In order to check GPS position accuracy, you may want to get a timing GPS receiver that can do position-averaging using Auto Survey features. Such as the Trimble Thunderbolts, the JLT Mini-JLT GPSDO, or the HP58503A units. The JLT unit is the only unit using WAAS augmentation, so it probably has a much quicker and more accurate position indication than the other units mentioned. Let it average the position of your antenna for a day or two, and you will likely have an accuracy at the centimeter level (horizontal) and at the foot level vertical. Beware of different GPS datums, e.g. MSL versus GPS height indications etc. You can use those GPSDO as a reference for your counter as well. The above equipment can be had with a couple of days shipping time from Ebay, at around $1500 to $2000 total and will serve you well for a very long time, and the resolution of the counter (150ps) is likely much higher than the GPS sawtooth error from the GPS you mentioned. If you need much more accuracy and resolution, get a Wavecrest DTS time interval analyzer from Ebay for around $800, those have picosecond averaged noise floors, femtosecond hardware resolution, and 10ps single shot resolution. In order to measure the 1PPS stability and accuracy, you would input the GPSDO reference 1PPS and your GPS 1PPS into the counter, and set it to T1 to T2 time interval measurement can capture that data. You may or may not use an external 10MHz reference for the counter doing this measurement, it shouldn't make a difference to your results.Then download Ulrich Bangerts excellent freeware Plotter program to do the time-stability analysis (search Google for Bangert Plotter and you will find his website). Please note that you may or may not want to use the GPS receiver sawtooth correction data on your dataset, either manually (using Excel to subtract the offset error), via a delay line, or other mechanism in your system. It will make a significant difference in your stability. To measure frequency, feed the GPSDO reference into the ref-in port of the counter, your DUT to the A input, then use the offset feature to remove the carrier frequency, then capture the frequency offset of your source to a file, and again use Ulrich's plotter to give you the time-stability info etc. Be warned, once you start on above path, you are likely never to stop searching for the holy grail of references, and measurement equipment.. Hope that helps, Said In a message dated 10/31/2012 12:36:55 Pacific Daylight Time, jlofg...@lsr.com writes: Hello Said, I'm familiar with your postings on the Time Nuts list, so I thought I'd ask your advice. I searched the Time Nuts archive, but didn't come up with what I was looking for (reference to a good GPS tutotial). We have a GPS project in-house that requires us to characterize receiver module performance. We have a Litepoint IQ-Nav box with several stored scenarios, but no other signal generators with GPS personalities in them. We need to measure position accuracy and time accuracy. We may also need to get some characterization of the 1 PPS output. I know that you do these types of measurements frequently. Could you point me to a good reference on correctly performing these tests and, maybe, describe the equipment you are using? We're checking through Agilent and RS application papers, but you seem to have a lot of the required knowledge readily available. Any help you could provide would be appreciated. Best regards, John ___ 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] Hp 58503A
No problem, happens to me too some times, usually the 10MHz Sine should be loaded with 50 Ohms, and the CMOS/TTL 1PPS pulses should be run open-ended (1M or higher).. I say usually.. because there are cases where proper termination is critical such as LVDS 1PPS outputs.. and where the 10MHz does not necessarily need to be loaded with 50 Ohms, resulting in a higher sine wave voltage - such as on our JLT GPSDO products.. bye, Said In a message dated 10/16/2012 09:36:25 Pacific Daylight Time, mdan...@gmail.com writes: I guess this it what they would call a rookie move? WOW, i feel like an idiot. I just loaded it down with a 50 ohm load and looks perfect. Thanks for enlightening me. ___ 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] HP Z3805A com port and monitoring questions
I think the Z3801A has the 6 channel receiver, the Z3805A seems to have the 16 channel GPS. Otherwise very similar I think.. both have the 10811 DOCXO, and very similar looking PCB's.. Rick, do you know of any other differences by any chance? Said In a message dated 10/14/2012 16:20:47 Pacific Daylight Time, jg...@zianet.com writes: Just cuious, of the two 58503A versions that yixunhk sells (Z3801A and Z3805A), which one has the better performance? I see that the Z3805A version has two 10 MHz outputs and one PPS. Joe Gray W5JG ___ 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] HP Z3805A com port and monitoring questions
Hi Edgardo, I think the Z3805A and 58503A are identical, except in the rubber bumpers, maybe the power supply voltage setting, and the ID string.. I don't really care, the three units I have perform much better than anything else I have, so that satisfies my requirements.. In fact one of the units' ADEV can only be qualified by the BVA 8600 o scillator I have, and I don't know if I am measuring the BVA performance or the 58503A because I am measuring right at the specification of the BVA unit.. Wish I had two BVA's :) bye, Said In a message dated 10/14/2012 15:41:25 Pacific Daylight Time, xe1...@amsat.org writes: Derived question: Will I get better GPSDO performance if I use a 58503A receiver? Or do you think our units match those 58503A GPSDOs out there? Again, thanks to everybody who helped me to figure out about my receivers and their inner workings. As always, you all made my day. Best regards, Edgardo Molina Dirección IPTEL ___ 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] Best counter setting for ADEV?
Very nice plot Tom! Did you thermally insulate the CSAC to get this kind of performance? bye, Said In a message dated 10/3/2012 09:24:54 Pacific Daylight Time, t...@leapsecond.com writes: Many thanks and for all of your help thoughts over the years. I'll look forward to the day and I can afford a GPS disciplined CSAC. Best, Kevin The CSAC is cheap compared to the reference you need to measure it... http://www.leapsecond.com/pages/csac/log96872v.gif /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best counter setting for ADEV?
Yes, very easy: 1) calibrate the internal 100MHz vectron OCXO using a small screwdriver, this is not really critical though as the unit does not really function as a frequency counter. 2) Calibrate the power supplies for proper voltages if necessary with same screwdriver, I found that is really not necessary usually 3) Auto-calibrate all the timing circuits using the built-in calibration feature and two external SMA cables, and two SMA shorts. The button to do that is on the front panel, and the unit does not have to be opened for this. You can also use their VISI application to do some more intensive long-term-averaging calibrations that are started via GPIB commands. There are user/service manuals floating around the web. Item 3) above is really the only thing that needs to be done from time to time I think. bye, Said In a message dated 10/2/2012 12:30:34 Pacific Daylight Time, jster...@att.net writes: Are these easily calibrated? I contacted Wavecrest earlier today and they want $750 for the annual calibration. Not exactly 'hobby' friendly :-) jerry -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Said Jackson Sent: Tuesday, October 02, 2012 9:06 AM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? There are two on ebay now, $600 and $700... Buy it now.. I would ask the seller to connect the 100MHz ref output to both inputs one at a time and to measure jitter to make sure they work before buying though.. Dts-2075 recommended due to higher performance. On Oct 2, 2012, at 5:49, Azelio Boriani azelio.bori...@screen.it wrote: Wavecrest DTS for $600? Interesting... On Tue, Oct 2, 2012 at 2:43 PM, Adrian rfn...@arcor.de wrote: Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian __**_ 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/listi nfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] RFX GPSDO - Anybody played with one of these?
Thanks much Didier! Those are kind words for the JLT team :) bye, Said In a message dated 10/2/2012 14:28:13 Pacific Daylight Time, shali...@gmail.com writes: Well Said, it looks like you have been busy! Congrats for an amazing product. Didier Sent from my Droid Razr 4G LTE wireless tracker. ___ 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] RFX GPSDO - Anybody played with one of these?
Hello Paul, thanks much for the feedback! Yes, we think we have identified a nice combination of oscillators, GPS, and firmware that seems to work pretty well. The GPSTCXO units cannot be compared to a lower cost $150 Thunderbolt in terms of phase noise or stability of course, and they have CMOS 10MHz outputs, but then the TB's cost around $1500 new I guess. We think the GPSTCXO's and LC_XO type units will work quite well wherever standard OCXO's are used today, and power/size/weight are an issue. Bye, Said In a message dated 10/2/2012 14:21:47 Pacific Daylight Time, paulsw...@gmail.com writes: Said I have to say I was looking through the list of modules that are available. I guess a couple of things really jump out. The low power consumption and what you get in terms of behaviors. It is pretty amazing actually. Though I have my power sucking Tbolt and 3801. But I could easily see for a Amateur radio operator just getting into time nuttery that these might be a nice way to go. I guess that would open an interesting debate. Getting the used RBs at Hamfest of questionable quality for $200 or far less. Or something modern and simply works. Regards Paul. ___ 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] Hi Power LED --- Thread Overload
Fellow Time Nuts, in the last week we had more than 50 emails concerning Fedex versus UPS shipping and how to package something, now we have a similar number of emails about LED lighting. I hope we can end this thread soon, or move it to another discussion group. I for one am getting really tired of deleting 50+ emails every day that are not related to time or frequency metrology. Thanks, Said That is a very fun prank to do. Show someone an o'scope with a flat line on it and hand them a pretzel or carrot. Tell them that you have implanted several sensors into their brain and you want to calibrate them starting with mandibular vibration. I have seriously freaked some people out with this one. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of gary Sent: Tuesday, September 18, 2012 12:28 To: time-nuts@febo.com Subject: Re: [time-nuts] Hi Power LED Light power supply... There are ways for the flicker to be more evident. Don't laugh, but chewing something hard like a pretzel can bring out the flicker. Basically you can get beat patterns between the vibration of your eye and the light flicker. There is a common problem with DLP projectors that use color wheels. You will see reviewers shaking their heads and eat crunchy food in order to see rainbows on the screen. A similar problem occurs with matrixed LED displays mounted on machinery that has vibration. Very common in industrial controls since they like LEDs for readability. When I designed the 2nd generation LED display drivers, I bumped the refresh rate to 500Hz min. That was about 2x the frequency where I ran out of convoluted experiments to detect flicker. On an analog scope, you can display a flat line and have it wiggle by eating something crunchy. I don't have an analog scope on the bench at the moment, otherwise I would figure out the right circumstances to make that happen. ___ 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] GPSDO control loops and correcting quantization error
Hi M. welcome to the world of GPSDO optimization, one thing you will find is that there never is a time when there is no chance to improve something :) On the 1PPS sawtooth correction, the usual convention is for the following 1PPS. The easiest thing to do rather than trying to guess the GPS unit's behavior is to try it out on both pulses, and also try adding and subtracting the number from your raw phase measurement, then you get four streams of values, and it will be instantly obvious which one is the one that reduces the noise most. The other three will increase the noise over your raw, uncorrected measurements. On the DAC resolution, it depends on the OCXO control range, and the ADEV performance you want to achieve. For example if your OCXO has +/-2Hz control range, then a 16 bit DAC will only give you an LSB resolution of about 61 microhertz, or 6.1E-012 (4Hz divided by 2^16). This may or may not be acceptable to you. If your OCXO has a more typical +/-20Hz control range, then this would go up to 6.1E-011 per LSB, which will definitely affect your ADEV. Usually, GPSDO's use at least 20 bit control range due to this quantization effect. But in the end it may also be limited by your time-interval-counter resolution, because every tick in your counter will equal to so many steps in your DAC (depending on what gains you use for your loop prediction). Also, make sure to put filtering for errand pulses into your code, every GPS WILL generate an errand pulse from time to time in my experience, and these can be off by 10's of microseconds.. if you don't filter these properly, they will lead to jumps in your frequency. Hope that helps, Said In a message dated 9/14/2012 11:21:57 Pacific Daylight Time, g...@partiallystapled.com writes: First off a technical question. I'm using a Trimble Resolution SMT as the pulse-per-second source. It sends a supplemental timing packet that contains an estimate of the quantization error in its pulse output. But the manual isn't clear on whether that applies to the next pulse or to the previous one. I've seen people correct the delay by using a programmable delay line which seems like it would only be possible if the measurement was for the next pulse. But on the other hand there is a pulse was not generated alarm that definitely applies to the previous (non)-pulse which suggests that maybe other fields refer exclusively to the previous pulse. I can handle either way since the pulses are timestamped asynchronously and can be post-processed at any time but from some preliminary data collection it's not clear which way it's meant to go. Does anyone know for sure whether the quantization error is for the next or preceding pulse? ___ 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] HP Z3805A
Hello Edgardo, glad you received them well, and within 48 hours from China! Hopefully they will work as well for you as for me. I noticed that some of the 60Hz/120Hz artifacts can come through the power supply into the 10MHz, so pick a power supply that has a case-ground connection, not just two pins like the normal wall-warts have. That will help reduce the supply noise. On the antenna, we are feeding them from a very low cost 5V automotive antenna, and a Symmetricom 1-to-4 splitter with lightning protection (that's important!). Works very well for us. I am sure most 5V antenna will work just fine. Hopefully they will work well for you too. BTW: try Ulrich Bangerts Z38xx, that program can be used to initiate the auto survey and monitor progress. Bye, Said In a message dated 9/14/2012 11:49:32 Pacific Daylight Time, edga...@iptel.net.mx writes: Dear Said, Good afternoon. I bit the bullet and ordered two HP Z3805A GPS units from the asian source you kindly advised. The units are really nice and brand new looking! The deal was smooth as silk and via DHL, the delivery took less than 48 hours to my door. I preferred to buy two bare units to compare them side by side, instead of buying the complete kit. Now I will have to search for a decent power supply and antennas for them. I plan to use a single GPS antenna and an HP RF splitter to feed both units. I have two questions regarding this and your experience will be certainly appreciated. a. What kind of antenna should I use for them? Any GPS antenna matching the instrument`s output voltage should do the job? b. I am thinking of picking a 24VDC 2.5A power supply. From an HP Z3801A manual (I can not locate the manual for the Z3805A) it reads that in terms of voltage and current consumption I should be fine. c. How critical is the power supply design in terms of noise to feed the Z3805As? I am planning for a well regulated source but I find the switched power supplies interesting for this purpose. Thank you beforehand for your time and comments. Please be sure I will be grateful for that. Regards, Edgardo ___ 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] Recommendations for a newbie?
Charles, maybe I did read your email wrong, I apologize for that. To me it came across as negative toward the seller and the listings, and it seems this is not how it was meant, my appologies. Bye, Said In a message dated 9/8/2012 23:05:30 Pacific Daylight Time, charles_steinm...@lavabit.com writes: I reiterate that I said (and certainly, I meant) nothing negative about the seller, and made no negative assumptions and no negative comments. In fact, I do have experience with him and have no complaints. My point was not that one might not get what was described; rather, it was that I cannot tell from the 58503A listings exactly what is being described, or how what is described in one listing differs from what is described in other listings that vary considerably in price. Nothing more. The End, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Recommendations for a newbie?
Hello Robert, your question is like asking which car you should buy, or which airline you should fly :) Everyone will have a different answer. But I do not recommend the Thunderbolts, it's a crab-shoot with them (different versions have different performance, the new ones are actually worse than older versions because of the temperature chip issue, the GPS is known to have lock issues, they don't work well until you spend a lot of time fine-tuning the parameters, etc etc) - that has all been discussed here ad-infinitum and you can find it in the archives. I recommend you search Ebay for HP 58503A. I just bought a number of them from a very well known seller in China, and they are absolutely superb, much better than any Rubidium unit I have tested. Much better than the Thunderbolt I have, and just slightly more expensive. He sells an entire kit for around $500, and it arrived here in less than a week (Northern California). This seller starts those units at around $260 I think. Performance you can get from these if you get a good one is: phase noise floor of around -163dBc, ADEV of 7E-013 to about 1E-012 to over 100s. Leapsecond.com has a number of test papers on these units. Caveat-emptor: there are significant unit-to-unit variations as with all GPSDO, Tom on leapsecond.com discusses this in detail. BTW: these are essentially the same unit as the Z3801A, just different software (ID string). I also have a Z3815A, and it is not even in the same class as the Z3801A/58503A. It is very noisy compared to the 58503A unit. I do not recommend the Z3815A, but it is a unique oscillator design,and some folks collect it for that oscillator. The 58503A uses a double oven version of the HP 10811A, which is a fantastic oscillator if you get a well-working one. If you want something low-cost with reasonable performance, brand new with warranty, antenna, and accessories, Jackson Labs Technologies, Inc. has the GPSTCXO eval kit for Time-Nuts special academic pricing of $300, which we believe is the lowest-cost true GPSDO (not NCO) in current production. Disclaimer: I work for them. bye, Said In a message dated 9/7/2012 13:09:24 Pacific Daylight Time, azelio.bori...@screen.it writes: Welcome aboard, yes, there is no FAQ about how to start in this hobby... should I try to implement one? Anyway, start with a Trimble Thunderbolt (aka TBolt), later you will know why it is highly recommended (direct OCXO disciplining and LH software support, mainly). I have a Z3815A with the famous (or infamous) E1938A hockey puck OCXO. They are all GPSDOs and there should not be any difference among them but, yes, there are differences in their performance and being a time-nut means test and find out. Then there are GPS disciplined Rubidiums, but take this step after the first GPSDO is correctly installed and stabilized. Start with the antenna: find a suitable place, with a 360 deg clear view of the sky, a satellite TV cable (sounds unusual, but works great). On Fri, Sep 7, 2012 at 8:52 PM, Robert Darlington rdarling...@gmail.comwrote: You want to start with a GPSDO. I like the Trimble Thunderbolt. The price is right and they're readily available. I have no experience with the HP units but they seem to be highly regarded. Rb oscillators are great for some things, but need to be calibrated. That's where the GPSDO comes in. Also, don't forget the antenna. You'll want something along these lines: http://www.ebay.com/itm/lucent-GPS-Timing-Reference-Antenna-antenne-40db-N-/230848464732?pt=GPS_Antennashash=item35bfa4075c#ht_2199wt_1404 Welcome aboard, and I'm apologizing in advance for how much money you'll be spending on new toys. -Bob ___ 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] Recommendations for a newbie?
Robert, my bad, that seller offers 58503A units based on both Z3801A and Z3805A. The latter has a 16 channel GPS receiver, so seems to me much more desirable than the Z3801A. $50 difference. I have been testing the latter, not the former. bye, Said In a message dated 9/7/2012 13:37:52 Pacific Daylight Time, saidj...@aol.com writes: BTW: these are essentially the same unit as the Z3801A, just different software (ID string). ___ 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] Recommendations for a newbie?
Hi Edgardo, they work well for me, look brand-new, and came with power supply, rs-232 cable, and antenna. I think it's a 5V antenna. The unit had about 37000 on the lifetime. The seller has close up photos, that's what the units look like. I plugged in the power, ran GPSCon to start an Auto-Survey, and they just worked. I now get less than 3us predicted drift over 24 hours from one of the units, which is quite good according to others. I think these are pretty good for the money (free shipping on mine) but there are differences between the three units I have just like the Z3801A plots on leapsecond.com. Hope that helps, Said In a message dated 9/7/2012 17:13:22 Pacific Daylight Time, xe1...@amsat.org writes: Dear Said, Good afternoon. How is the service and cosmetic condition of the HP GPS products you have bought from this source? I am considering a Z3805A just for the sake of owning one and the versatility of plug and play. Still afraid to take the plunge. Did you buy a raw unit? Or as a kit with antenna. Is that a 5V or 12V antenna? I am integrating a TBolt into a 1U rack case which also has space for a Rb oscillator for future disciplining. Got a nice TBolt monitor and would love to also include a frequency divider to get 5 and 1MHz from the TBolt. Your kind comments are welcome. Thank you. Regards, Edgardo Molina Dirección IPTEL ___ 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] Recommendations for a newbie?
Hi Jerry, I am not familiar with those, sorry. The only complaint I would have about the 58503A units I have is that they have a bit of power supply spurs at about -130dBc. Running them from batteries would probably take care of that. Otherwise they work great for me and provide both great ADEV and very good phase noise at the same time, what else can one ask for $550.. But again, there may be large unit-to-unit variations as Tom has found out, and I may have been lucky with the units I received.. bye, Said In a message dated 9/7/2012 15:55:04 Pacific Daylight Time, jster...@att.net writes: Said, Where do you rank the Samsung GCRU-D among these? Jerry ___ 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] ublox chip sets - what GPS device should I buy?
Dave, that depends on which uBlox the unit supports. There are basically three different sizes: AMY, LEA, and NEO. They also sell chip-sets, but only to very large volume customers. Any of the uBlox-6 will be excellent, the choice will depend on form-factor, and also if you need a timing-version that supports position-hold mode (denoted as a -T) or not. Even the uBlox-5 units are already extremely good. This assumes you can solder the uBlox module onto a PC board inside the analyzer yourself. bye, Said In a message dated 8/31/2012 12:14:09 Pacific Daylight Time, david.kir...@onetel.net writes: I've bought an Agilent N9923A portable 2 MHz to 6 GHz vector network analyzer which supports GPS. I assumed it had the GPS bought it, but later found it it needs a GPS unit with a ublox chip set. Are there any ones to avoid, or which are good? Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] oscillators
There are some drawbacks to this type of SC-cut MCXO I would think, and it could possibly be replaced by a much higher performance Symmetricom CSAC, probably at a lower cost and higher availability: * Q-tech MCXO is ITAR controlled, CSAC is not * MCXO has 20ppb over temp stability, CSAC has 1ppb spec, typical units can be much lower than that. Our GPSTCXO has 75ppb over temp, not much more than the MCXO, but probably at 1/10th the cost. * The G-sensitivity of CSAC is at least 50x better than the MCXO (its so low, its very hard to measure) * Aging of MCXO is much higher (order of magnitude) * Symmetricom is a big player, Q-tech is relatively small and unknown * I remember that there are patents on the MCXO held by FEI? * Power consumption is very similar, future CSAC units will have much lower power than the MCXO. The MCXO does have lower phase noise, it's an SC-cut cyrstal after all. But with CSAC's now becoming available from multiple sources, why use an MCXO? bye, Said In a message dated 8/30/2012 10:35:56 Pacific Daylight Time, rich...@karlquist.com writes: First, it has to have no activity dips over the full operating temperature range. OCXO crystals only have to work at the oven temperature. Activity dips, according to John Vig, are the reason whey they don't use mode B to sense temperature. Second, it has to be cut correctly so that the beat note between the fundamental times 3 and 3rd overtone modes is a useful indicator of temperature. ___ 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] Trimble Mini-T end of life
Hello everyone, please send suggestions for the following new product we are working on: Trimble recently announced that the Mini-T is end of life, and is giving a last time buy of August 1st 2012. It does not seem that Trimble plans to offer a replacement unit. The Mini-t enjoyed a relatively short lifetime, and it seems Trimble has left it's customers hanging in the air, as when it discontinued the Thunderbolt some time ago. Jackson Labs Tech is in the process of designing a replacement unit for the Mini-T that customers will be able to use as a direct replacement so that they don't have to order more units than they need and don't have to cancel running projects, but this unit will have much higher performance and significantly more features and options to chose from. Availability of evaluation units is early next month, and it will not be discontinued as long as there is demand. There is still a window of opportunity to suggest added useful features, so please do send your suggestions to me as to what you would like to see in a perfect Mini-T replacement unit. We will consider all reasonable suggestions and requests. Thanks much in advance, Said ___ 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] Trimble Mini-T end of life
Hi guys, thanks so much for all the great suggestions on how to make this product better! Yes, cost targets are a very important goal here, and we are looking into adding options that make sense for most customers and don't add excessive cost or delay to the schedule. We definitely will improve the performance of the unit over the original Mini-T though, because we feel that the Mini-T had sub-par performance on many fronts, and don't want to make the same mistakes. Some of the improvement items we have already decided upon are: * 50 channels GPS with WAAS/EGNOS/MSAS and Position-Hold mode with automatic initialization of the Auto-Survey process by default. Alternatively, the unit can be put into mobile mode, with Auto-Kalman filter optimization depending on vehicle velocity. -160dBm GPS tracking capability * A secondary 10MHz output (SMA or SMB connector, only the connector needs to be stuffed onto the PCB) to have access to the +13dBm output signal * Internal +3.3V antenna supply, that is automatically over-driven by the externally applied antenna supply * USB connector for command/control, RS-232 option, and TTL serial port for legacy compatibility * RoHs 6/6 for compatibility, and RoHs 5/6 option for much longer life and better MTBF than Mini-T * more than 3x better thermal stability, and at the same time more than double the temperature range (+/-5ppb over -40C to +85C versus +/-10ppb from only 0C to +60C) standard, and DOCXO option for even higher thermal stability performance and low-g sensitivity/ruggedized crystal options. * Better phase noise * Status LED's on board * TTL lock/ALARM indicator * External 1PPS input option on unused pin 1 of the main connector * Fully field-upgradable firmware, no FPGA programmer needed * Support for NMEA and SCPI commands * 3-axis accelerometer built-in * lower height: 0.47 inches OCXO height versus 0.75 inches * Much better ADEV performance * Factory-testing for crystal-jumps on every unit We also had several folks ask for alternative frequency outputs, and are currently investigating if we could use the secondary 10MHz connector to add another VCXO to generate any output frequency from 10MHz to 120+MHz such as is done on our ULN-1100 boards. This would add some cost though, and may just end up in a secondary version of the board so that customers who don't need it won't have to pay for it.. The most important item to get feedback on is the TSIP port, we cannot implement the entire TSIP command set as this is quite complex, most customers probably only use a handful of actual commands, and we believe the SCPI/NMEA command/control/status interface is much superior over the proprietary binary TSIP port. We are however open to implement a couple of useful and common TSIP outputs, and would greatly appreciate feedback and suggestions on this, for example a minimum set to make Lady Heather work..? Thanks, Said In a message dated 7/19/2012 13:41:07 Pacific Daylight Time, wb6...@cox.net writes: Hi Said, I know everyone is going to ask for the kitchen sink to be thrown in. BUT, how about just making a replacement that does exactly the same job with no added thrills ? That way your spending the least amount to produce a product and keeps the cost down to the customer which may cause them to want to keep designing with that particular product. just saying BillWB6BNQ ___ 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] FTS125 GPS Module
Yes, I am sure, depends on the firmware revision and configuration settings. Don't want to name any names here though. Secondary firmware can detect, and prevent this behavior once you know it exists, and what makes it happen. That's part of what makes the difference between an NCO and a real GPSDO. With an NCO such as the FTS parts, you get a simple analog PLL that has no smarts or intelligence, and a GPS receiver that can get hung up when in holdover for excessive amounts of time. There is ample evidence in the time nuts archives that the Trimble GPS have problems getting a fix in the first place after power-on. Several users reported that here, and in other places. Also, now we are being told that Trimble discontinued the Mini-T, and we see lot's of customers panicking and looking for replacement solutions as Trimble seems to not want to offer a replacement product and is giving a last-time-buy notice. Sorry for those customers, gives an opportunity for others to move in. bye, Said In a message dated 6/28/2012 12:21:27 Pacific Daylight Time, azelio.bori...@screen.it writes: other GPS receivers have the same exact problems when left in holdover for hours or more Are you sure? Never seen that behavior on a Trimble, Motorola/iLotus, uBlox, Sanav or SkyTraq receiver, only on NavSync. The locking algorithm of the FTS250 (and maybe the FTS125 too) is a National LMX series PLL chip (I can't remember the exact part number, have to check with the FTS250 COO we have). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Morion MV89A pics
FEI did not own Morion, they owned a number of shares. Some time ago the Russian government forced them to sell all, or almost all of their shares to keep Morion fully Russian-owned. Unfortunately they are not easy to deal with on a commercial level (to put it into objective terms), and thus probably only FEI is using them in their products. bye, Said In a message dated 6/9/2012 06:20:57 Pacific Daylight Time, li...@rtty.us writes: Hi They certainly own a co-production facility located inside the Morion factory in St. Petersburg. It's a *big* 1930's era building with lots of space. Bob On Jun 9, 2012, at 5:37 AM, Rob Kimberley wrote: Bob, FEI as far as I know do own Morion. That's certainly what I was told when I worked for Zyfer (also owned by FEI). Rob K -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: 09 June 2012 02:15 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Morion MV89A pics Hi ___ 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] GPS and Rubidium frequency standards and noise question (new...
Jerry, Chris, it's all relative, while the Lpro may be a good Rb standard, it's phase noise is not that good really. You list: -96dBc/Hz @ 10Hz, -138dBc/Hz @ 100Hz, -152dBc/Hz @ 1KHz offsets For the Lpro. The new Jackson Labs Technologies LN CSAC GPSDO with SC-cut phase noise and ADEV filter achieves the following: -138dBc/Hz @ 10Hz, -148dBc/Hz @ 100Hz, -152dBc/Hz @ 1KHz offsets. At 1Hz offset we see -105dBc/Hz and better on that unit. The FEI-5680A Rubidium that we discussed here some time ago has a much worse phase noise plot of course, because the 10MHz is generated digitally through a DDS, not a 10MHz crystal oscillator.. It all depends on your requirements, and your budget.. I think the Z3801A (or it's brother the 58503A) is still one of the lowest phase noise and best ADEV GPSDO on the surplus market if you get a typical unit, and if you can locate one. bye, Said From: Jerry Mulchin _jmulchin@cox.net_ (mailto:jmulc...@cox.net) Date: June 2, 2012 16:44:14 PDT To: Discussion of precise time and frequency measurement _time-nuts@febo.com_ (mailto:time-nuts@febo.com) Subject: Re: [time-nuts] GPS and Rubidium frequency standards and noise question (newbie). Reply-To: Discussion of precise time and frequency measurement _time-nuts@febo.com_ (mailto:time-nuts@febo.com) Chris, To answer your question regarding using a Rubidium standard as a frequency reference for your Transverters. GPS really has nothing to do the main requirement regarding Phase Noise and your Transceivers. But the 10MHz oscillator inside the Rubidium standard is the item that will be the Phase Noise problem if you get the wrong Rubidium standard. There are cheap Rubidiums and there are good Rubidium standards to consider. An LPRO-101 is actually a very good Rubidium standard, and exhibits Phase Noise values of -96dBc/Hz @ 10Hz, -138dBc/Hz @ 100Hz, -152dBc/Hz @ 1KHz offsets from carrier. This is what I use for my 10GHz Transverter reference, but I don't lock it to GPS when in the field. LPRO-101's can be gotten pretty reasonably. Locking the LPRO-101 to a GPS will require more support circuitry, and most of the folks on this list can help you with that. Also, Thunderbolt GPS disciplined units are nice, but I do not know the Phase Noise numbers of a typical Thunderbolt unit. Others here probably know the answer to that. The important thing to remember is you don't what to use 10MHz oscillators that have poor Phase Noise performance as it will effect your weak signal capability if you use a poor Phase Noise oscillator. Jerry At 03:05 PM 6/2/2012, you wrote: If you want a frequency reference. There is nothing better than GPS. In fact it you bought a Rubidium you would still need the GPS so you could calibrate its frequency. Some GPSes might be noisy but then you can lock a good double oven crystal oscillator to it and have what they call a GPS disciplined crystal oscillator or GPSDO. On Sat, Jun 2, 2012 at 2:57 PM, Chris Wilson _chris@chriswilson.tv_ (mailto:ch...@chriswilson.tv) wrote: I am looking to get a frequency standard for my amateur radio shack, initially for verifying test gear readings, but later as a standard to lock receiver and transmitter oscillators to. I was going to buy a GPS frequency standard but a friend warned me these may have noise issues when I come to use it with an oscillator in RX / TX applications. It's not something I had considered, so what's the score here please? Should I not buy a GPS standard? Thanks. Any links to known safe suitable purchase sources from personal experience welcome, either here or by PM or e-mail. I am in the UK. -- Best regards, Chris Wilson _mailto:chris@chriswilson.tv_ (mailto:ch...@chriswilson.tv) ___ time-nuts mailing list -- _time-nuts@febo.com_ (mailto:time-nuts@febo.com) To unsubscribe, go to _https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts_ (https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts) and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- _time-nuts@febo.com_ (mailto:time-nuts@febo.com) To unsubscribe, go to _https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts_ (https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts) and follow the instructions there. Jerry Mulchin ___ time-nuts mailing list -- _time-nuts@febo.com_ (mailto:time-nuts@febo.com) To unsubscribe, go to _https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts_ (https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts) and follow the instructions there. = ___ time-nuts
Re: [time-nuts] Why are 1PPS signals so skinny?
Yes, but the point is to not use end-termination for all the reasons mentioned by others in this thread, such as massive spike in power consumption once per second, over-voltage spikes if the termination is faulty or missing, higher ADEV due to power supply modulation, etc etc.. Your test clearly shows the ringing when the transmission line is left open, and it shows the massive current (5V into 50 Ohms) when end-terminating the cable. It also shows that the cable is ringing up to 7V or more! Which could actually kill your driver circuit by overvoltage if you forget to enable the 50 Ohms termination on your counter or scope for example. The voltage could theoretically spike all the way up to 10V as long as the pulse is traveling back on the coax. All more reasons why this is an undesirable mode of operation. To make this work without the unnecessary power consumption simply remove the end-termination resistor, and use it as the series termination resistor (R1 in your schematic)! Done. Attached are two plots of a series terminated (~55 Ohms) high-speed 1PPS transmission from our CSAC GPSDO board zoomed-in and zoomed-out to show the actual rise-time, and a longer time frame view. The 1PPS pulse was run through about 30 feet of LMR-195 cable, directly connected to the CSAC GPSDO 1PPS CMOS 5V output. There is no massive voltage over-shoot, the output is short-circuit protected, and no matching resistor is required, just a 50 Ohms coax cable. Use an additional 25 Ohm series resistance for 75 Ohms cables. The output rise time is 1.25ns at the end of the 30 foot cable, and the signal fully settles within 800ns, and never goes below 4V after the initial 1.25ns rise. The current spike on the power supply is only there during the time that the cable is being charged up, which is about 30 feet * 2 * 1.5ns/foot = ~100ns. That is short enough for the power supply caps to filter the current spike. In short, one could easily modify the Thunderbolt 1PPS output circuit which is probably a bunch of parallel AC240 gates with some low value series resistors, and modify these resistors to have the equivalent of 50 Ohms impedance. That would alleviate the need for end-termination on the coax, and provide very clean rise time, fall time, and no ringing. BTW: one advantage of this in the lab is that you can connect multiple instruments to one 1PPS output. The signal will take slightly longer to settle as it has to traverse and charge more cable hubs, but in the end there will be 5V on the cable with no DC current flowing, and there won't be any positive ringing above 5V. You cannot drive more than one input if you are using 50 Ohm end-termination without possibly over-loading the driver, and causing massive impedance mismatch, and getting the associated cable ringing etc. bye, Said In a message dated 5/15/2012 11:49:14 Pacific Daylight Time, shali...@gmail.com writes: The Thunderbolt's output impedance is much less than 10 ohms. However, it is only necessary to filter the end of the line for a clean pulse. See http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.php I used the Thunderbolt's PPS output as a source in those measurements. CSAC_risetime.GIFCSAC_risetime_zoom.GIF___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why are 1PPS signals so skinny?
Not really, your setup requires all inputs except the very last one to be high-impedance to work, and to have a trigger point of 1.25V as well to work properly (when used with a proper 50 Ohms source). So no difference there. So it doesn't make any difference, since the same exact inputs will work just as well with the open-ended circuit if the trigger point is set to 1.25V on those inputs. Same requirement for both setups. Daisy-chaining is a bad idea because you are getting the propagation delay between the different hubs as mentioned. Using a simple T with open-ended cables would make all inputs switch simultaneously if the cable lengths after the T are the same. Daisy chaining also creates stubs along the way due to the capacitive loading on the cable at the inputs, and the small amount of additional wiring at the stub, and these stubs will cause reflections going wild due to impedance mismatch at the stub, and run amok between stubs and between the ends of the cable. BTW: when setting the threshold to 2.5V and tapping-off somewhere in the cable, this is called reflected wave switching, as opposed to incident wave switching, which is what happens when you set the threshold to 1.25V. Also, the Thunderbolt has less than 5 Ohms output impedance, so you get a reflection going back from the 50 Ohms end-termination anyway because the impedance is mismatched! The signal won't stop at 2.5V, it will go all the way up to 5V in static conditions just the same as in my scenario. This can be seen in the plots that Didier had sent earlier. But worst of all: if your 50 Ohms end-termination falls off, or goes away because you turn-off that piece of equipment providing that termination, then almost sudden all of your inputs can see 10 Volts on the line, and could blow up due to overload. Having a 1.25V threshold input seeing a 10V signal is not a good idea.. You get all the drawbacks and more, and no real advantage. At least when connecting to e.g. a Thunderbolt output that has 50 Ohms series impedance. bye, Said In a message dated 5/15/2012 13:44:42 Pacific Daylight Time, dave.martind...@gmail.com writes: It is worth noting that skipping the end termination is probably a bad idea when daisy-chaining a signal from one output to more than one device input. The input at the end of the cable will see a clean rise from zero to 5 V (or whatever the driver's open-circuit voltage is), but the other inputs along the length of the cable will not. They will see an initial rise from 0 to 2.5 V as the series termination at the driver and the cable impedance act as a voltage divider while the cable is being charged. Later, they will see another step change from 2.5 V to 5 V as the reflection returns from the open-circuit far end of the cable. If the input threshold is automatically set at half the input voltage swing, the input could trigger on the outbound or the reflected pulse, or even somewhere in between. This is in contrast to having a 50 ohm termination at the end of the cable (plus the 50 ohm series termination at the source), where all inputs along the length of the cable see a single edge transition from 0 to 2.5 V. They will each see the edge at a different time due to propagation delay, but all will see a clean edge. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why are 1PPS signals so skinny?
Mike, Attila is trying to explain that the leading edge is not what we are concerned about in this thread (its subject to discussion in other email threads), it is the effect of what follows after that leading edge, and propagates down the power supplies to cause side effects that is being discussed here. Tom mentioned he can measure this as 10's of Watts of increased power consumption spikes on the AC line when the 1PPS goes high. This won't happen with short pulses, only with long ones that are end-terminated. In a message dated 5/15/2012 13:51:43 Pacific Daylight Time, mi...@flatsurface.com writes: On 5/15/2012 4:19 PM, Attila Kinali wrote: If the PPS pulse is short, it contains very little energy, which means the energy can be supplied by the small capacitors at the output driver. The longer the pulse gets, the more energy it needs. The pulse is meaningless. It's only the leading edge that matters. I understand how shorter pulses may make for marginally cheaper electronics. Which might have a negative effect on their performance. I might win the lotto. The question is exactly _how_ does it effect their performance, especially if they're synchronizing to the PPS signal. it's no use of having a fast rising edge, if the pulse colapses a couple ns later. Huh? If ns is too short, and ms is too long, what makes us just right? And why are there so many timing receivers that only output on the order of 20 us, when there are so many inputs which may require a few ms? PPS is edge triggered, not level triggered. Once the leading edge is transmitted (and it by necessity has a very fast rise time, so it looks to capacitors, transformers, etc. as a high frequency signal), the shape of the pulse really doesn't matter much. Some devices need more than a minimum above some threshold, but what ones need less than a maximum? If it doesn't look like a flat topped pulse, so what? As long as the decay is basically monotonic, and the receiver has some hysteresis (reasonable assumptions), it makes no difference. ___ 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] Why are 1PPS signals so skinny?
QED: here is a phase noise plot of a 200ms 1PPS pulse showing up in the phase noise spectrum of a 10MHz source (at 1Hz to 10Hz offsets) because the unit was providing a 100mA current pulses into the cable, and power supply modulation of the 10MHz output happened inside the unit. The pulses would likely not be visible if they had been only microseconds long, or the cable was not incorrectly end-terminated and causing the massive DC current to flow. Yes, yes, the unit could have been designed to handle that scenario, but the point is: modulation is going to happen, and could be 10's of Watts, and it will likely have some effect in one way or another. The discussion started with the question of why one would design short 1PPS pulses versus long pulses. This is one reason why. In a message dated 5/15/2012 14:24:07 Pacific Daylight Time, mi...@flatsurface.com writes: On 5/15/2012 5:14 PM, saidj...@aol.com wrote: it is the effect of what follows after that leading edge, and propagates down the power supplies to cause side effects that is being discussed here. I'm asking What side effects? I haven't seen any mentioned. And really, if an increase in power draw of 10 watts for an entire lab environment causes any problems, I'd question the quality of the power supplies, and ask what happens when you simply turn on the light? run94019-spec.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why are 1PPS signals so skinny?
Forgot to mention, on this list we are often concerned with noise floors of -170dBc or lower, and stabilities of 1E-013 or lower. At that level, your scenario of stepping into the room and turning on the light will likely cause a measurable effect just because of the mechanical vibration you are inducing into the crystal by walking into the room.. In a message dated 5/15/2012 14:24:07 Pacific Daylight Time, mi...@flatsurface.com writes: On 5/15/2012 5:14 PM, saidj...@aol.com wrote: it is the effect of what follows after that leading edge, and propagates down the power supplies to cause side effects that is being discussed here. I'm asking What side effects? I haven't seen any mentioned. And really, if an increase in power draw of 10 watts for an entire lab environment causes any problems, I'd question the quality of the power supplies, and ask what happens when you simply turn on the light? ___ 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] Why are 1PPS signals so skinny?
Yes, you are right of course. My bad. This should have been written as: The Thunderbolt has less than 5 Ohms output impedance, so if you get a reflection coming from the cable stubs or non-end-terminated cable back into the Thunderbolt, then you get ringing on the cable because the impedance is mismatched! On a properly series terminated device, any reflections on the open-ended cable coming back to the source will end in the sources' 50 Ohms terminator, and be removed. One more advantage I didn't mention for series termination versus the Thunderbolt used with end-termination. In a message dated 5/15/2012 15:03:12 Pacific Daylight Time, hmur...@megapathdsl.net writes: saidj...@aol.com said: Also, the Thunderbolt has less than 5 Ohms output impedance, so you get a reflection going back from the 50 Ohms end-termination anyway because the impedance is mismatched! I think that's a different problem. If the far end termination matches the cable there won't be any reflection. If the far end isn't terminated correctly, there will be reflections from the far end. There may also be reflections from joints in cables or a Tee and input load if you are daisy chaining multiple instruments. When those reflections get back to the typical low impedance driver, they will get reflected back again. It's not uncommon to use both source/series and end/parallel terminations. The series terminator drops the signal level by 2 but minimizes reflections if you are working in a less than ideal setup. It also provides a current limit on the driver in case something gets shorted. ___ 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] Why are 1PPS signals so skinny?
Hi Rick, one reason why we happy blink at 1/2Hz :) There are other offendors as well, such as the processor and GPS going through the hoops once per second, but the 100mA surge from the 1PPS output driver trumps all else. bye, Said In a message dated 5/15/2012 16:44:08 Pacific Daylight Time, rich...@karlquist.com writes: saidj...@aol.com wrote: Yes, but the point is to not use end-termination for all the reasons mentioned by others in this thread, such as massive spike in power consumption once per second, over-voltage spikes if the termination is faulty or FWIW, the E1938A oscillator control board had a happy light LED that flashed 1 time per second, and sure enough this corrupted the power supply and affected some applications. We added a command to turn it off. 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] Why are 1PPS signals so skinny?
I met Jenny in 1987 - not that skinny at the time :) That was after she sold the company already. In a message dated 5/15/2012 16:41:34 Pacific Daylight Time, b...@iaxs.net writes: Jenny Craig? ___ 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] Calculating phase jitter from phase noise - appnote by silabs
Hi, here is a very nice and easy to use online calculator for doing exactly this: _http://jittertime.com/resources/pncalc.shtml_ (http://jittertime.com/resources/pncalc.shtml) bye, Said In a message dated 5/11/2012 09:17:30 Pacific Daylight Time, li...@rtty.us writes: Hi Be very careful with all these phase noise to jitter conversions. They make some assumptions about the noise that are likely true, but may not be. The gotcha is that a normal noise measurement does not take phase data. Without the phase data you really can't properly do the reconstruction. You have to assume that it's random in the phase domain. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani Sent: Friday, May 11, 2012 11:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Calculating phase jitter from phase noise - appnote by silabs And one from HP/Agilent (taking into account the colored noise too: http://cp.literature.agilent.com/litweb/pdf/5990-3108EN.pdf And one from Fordahl, with the random zero cross consideration: http://www.metatech.com.tw/doc/appnote-fordahl/e-AN-02-3.pdf On Fri, May 11, 2012 at 4:00 PM, Jim Lux jim...@earthlink.net wrote: ___ 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] Improved timing through simple dish
Hugo's idea of using a Sat dish to zoom in on a WAAS Sat as discussed in the below paper is quite brilliant I think, and it seems one should be able to make use of it by disabling the GPS sats (via mask angle for example) in receivers that support WAAS, and that are used in position hold mode. According to their plots the WAAS-only setup gave them a huge improvement in timing accuracy. One should be able to make a much smaller dish, as all that gain is useful but probably not needed. bye, Said From: Sam _li...@digitalelectric.com.au_ (mailto:li...@digitalelectric.com.au) Date: May 11, 2012 5:14:24 PDT To: Discussion of precise time and frequency measurement _time-nuts@febo.com_ (mailto:time-nuts@febo.com) Subject: Re: [time-nuts] Trimble Resolution SMT - good/bad/indifferent? Reply-To: Discussion of precise time and frequency measurement _time-nuts@febo.com_ (mailto:time-nuts@febo.com) I uploaded the FEI-Zyfer WAAS papers to zippyshare if anyone is interested. _http://www32.zippyshare.com/v/66696070/file.html_ (http://www32.zippyshare.com/v/66696070/file.html) Sam. ___ 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] Trimble Resolution SMT - good/bad/indifferent?
Hi Holrum, how do you re-configure the SMT unit? Using Trimble GPS studio? Thanks, Said In a message dated 5/9/2012 15:17:21 Pacific Daylight Time, hol...@hotmail.com writes: I have it running now. It turns out that the units from fluke.l come shipped with TEP format messages enabled (it outputs @@Cf on power up). You have to re-configure them for TSIP protocol and save the configuration back to the unit. Hope to have Lady Heather taking to it. It does come up with several of the messages working. Sat info is not one of them. ___ 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] Trimble Resolution SMT - good/bad/indifferent?
Ok, I figured out that the unit fluke.l sells is running firmware to emulate the Motrola M12+ receiver or similar. So WinOncore 12 does work, and I can get the following receiver ID: COPYRIGHT 2008 Trimble Navigation Ltd. SFTW P/N # SOFTWARE VER # 0.03.0 SOFTWARE REV # 00 SOFTWARE DATE 04/27/2009 MODEL #3011 HDWR P/N # SERIAL # 20393136 MANUFACTUR DATE 06/05/2009 OPTIONS LIST Does anyone know what the command is to configure this for NMEA or TSIP? Thanks, Said In a message dated 5/10/2012 12:15:56 Pacific Daylight Time, saidj...@aol.com writes: Hi Holrum, how do you re-configure the SMT unit? Using Trimble GPS studio? Thanks, Said In a message dated 5/9/2012 15:17:21 Pacific Daylight Time, hol...@hotmail.com writes: I have it running now. It turns out that the units from fluke.l come shipped with TEP format messages enabled (it outputs @@Cf on power up). You have to re-configure them for TSIP protocol and save the configuration back to the unit. Hope to have Lady Heather taking to it. It does come up with several of the messages working. Sat info is not one of them. ___ 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] Trimble Resolution SMT - good/bad/indifferent?
The first problem is, I didn't even know that was the command set the unit had, the @@Cf looked familiar though. I wasted an hour trying to get the Trimble application to work, until I tried WinOncore12 and the unit responded. Can't use TeraTerm to send commands, and the user manual doesn't document which Motorola commands are supported, some I found are not, and it doesn't send PVT sentences by default, it requires the user to initialize the GPS every time the power is cycled. I never got that, why would Motorola assume the receiver should be muted until enabled via software command? That doesn't make any sense to me. By default, send some useful PVT messages (Ha, Hn, for example) and allow the user to set up the unit to be mute when so desired. I wonder how many folks have pulled out their hair trying to get their Motorola units talking at the right baud rate etc etc. Maybe using it in products makes sense when one has time to learn and program for the binary messages, but debugging and development are a hassle.. Lastly, can't use the host of NMEA compatible applications that are out there, the Motorola-aware apps are pretty limited. Again uBlox has it right in my opinion: support for a huge host of binary commands if so desired, and standard NMEA output by default without any user interaction required. bye, Said In a message dated 5/10/2012 14:07:55 Pacific Daylight Time, azelio.bori...@screen.it writes: What's bad with the Motorola binary protocol? In my opinion it is superior to the NMEA one... On Thu, May 10, 2012 at 9:55 PM, saidj...@aol.com wrote: Ok, ___ 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] Trimble Resolution SMT - good/bad/indifferent?
There is the problem: I used the Trimble GPS Studio application that was posted here yesterday, that does not support the TEP protocol.. Will try with GPS Monitor.. Is the TrimbleMon available somewhere safe on the web? Can't seem to find it with Google. I got it working with Oncore12, and I am capturing 1PPS raw data already. Already noticed that while the signal strengths look good, there are way less Sats being seen than on the 50 channel receivers, and none of the WAAS ones are being decoded. thanks, Said In a message dated 5/10/2012 14:07:38 Pacific Daylight Time, hol...@hotmail.com writes: The receivers from fluke.l are the TEP version that emulates Motorola protocols by default. I used Trimble GPS Monitor V1.05 to set it for TSIP. Select the Initialize Menu, Detect Receiver, click TEP protocol button. It then found the receiver and offered to enable it for TSIP. Then clicked SAVE CONFIG (so some such). I set it up for 9600,8,N,1 to make it easier to use with Lady Heather (default is 9600,8,Odd,1) using the Recever Configuration menu. ___ 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] Oh dear - can we please close this thread
Guys, this thread and the un-countable emails it has generated so far is the exact type of discussion that TVB just sent out an email about that should not be on time nuts. bye, Said In a message dated 5/7/2012 16:00:54 Pacific Daylight Time, mbla...@satx.rr.com writes: Wow! $1260 for a 4' power cord, but wait, there's more... It was named 'Power Cord of the Year'. Mike On 5/7/2012 9:39 AM, Burt I. Weiner wrote: A friend of mine signed me up for a catalog from the Audio Advisor. He said I deserved this - I was afraid to ask what he meant by that! Spend a few minutes looking over this site: http://www.audioadvisor.com/ Be sure to check out their Power cords at: http://home-audio.audioadvisor.com/search?w=Power+Cords Burt, K6OQK From: Rob Kimberley robkimber...@btinternet.com To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] Oh dear An old saying: a fool and his money are often parted. Sums things up nicely I feel. Rob Kimberley Burt I. Weiner Associates Broadcast Technical Services Glendale, California U.S.A. b...@att.net www.biwa.cc ___ 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] 5370B and 10544 OCXO
No necessarily. It could also mean the 5370B likes the output signal of the 10544 fed internally better than the other two, maybe due to a higher signal level or less noise in the internal PLL bandwidth? You could verify this by feeding in the 10544 into the front jack while the 10811 sits inside the unit itself, then reversing (switching) the two oscillators with each other and comparing results. Theoretically the result of both measurements would be identical, except if your 5370B somehow likes one over the other, possibly due to the way it multiplies the 10MHz up to 200MHz. One oscillator may have a better noise spectrum in the loop bandwidth of that 20x multiplication PLL etc. Your measurement is basically using the following: full noise bandwidth on the external A input, and possibly only limited noise bandwidth in the internal connection due to the internal 10MHz to 200MHz up-conversion PLL which has a smaller noise bandwidth than the A input. Hope that makes sense, bye, Said In a message dated 5/4/2012 15:06:37 Pacific Daylight Time, iov...@inwind.it writes: Recently I bought for cheap a nice looking latest production but not working 5370B. It turned out to be missing the 10811, its power supply card, and the relay. I borrowed these parts from my 5370A, and the 5370B worked fine. For some reasons today I've been swapping OCXO's between various counters. What I noticed on the 5370B is a different behavior in the test made feeding the time base output (rear panel) to the front panel input and the counter set to frequency. As we know (already discussed here), the readout in this condition is not 10 MHz (which would appear logical as the oscillator measures itself), but something like 9,999,999,xyx, with xyz varying continuously. Well, in my case, I noticed that: -with the 10811 all of the three rightmost digits (xyz) were varying randomly; -with a Piezo Crystal clone, same result as with 10811; -with a 10544, only the two rightmost digits were varying. I repeated the test several times. This would mean to me that the 10544 is less noisy, at least mine. Am I right? Antonio I8IOV ___ 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] thunderbolt no UTC offset
Incorrect, the UTC offset should be sent in the Almanac, the Almanac having a period of 12.5 minutes max. Not one hour. It should take no more than 12.5 minutes to get the UTC offset when sats are properly being received. bye, Said In a message dated 5/1/2012 11:45:06 Pacific Daylight Time, francesco.messi...@gmail.com writes: Hi Hal, On 5/1/12, Hal Murray hmur...@megapathdsl.net wrote: francesco.messi...@gmail.com said: I just powered on again my trimble thunderbolt after some time without antenna. All alarms are green but the obvious leap second pending. BUT: I can't use UTC time as both tboltmon and lady heather display a No UTC offset message. I don't remember having seen this in the past. What's wrong with the thunderbolt now? How long has it been on? The UTC offset comes from the satellites. I think it is only sent every hour. yes indeed, it was ok after about 1 hour of the power up. Sorry but I didn't remember I had ever waited so long for the UTC to come on. I'm now plotting the signal strength vs AZ/EL map, I'll post the result tomorrow so maybe someone can tell me how the new antenna is working. Thanks Frank IZ8DWF ___ 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] Symmetricom TimeSource 2700
Hello Mark, you could connect the Fury 1PPS output to the 1PPS external sync input of the PRS-10 Rb and let is self-discipline to GPS. Set the Fury 1PPS jumper JP4 to raw-1PPS (pins 2 and 3), and that will make the Fury GPSDO generate the raw 1PPS signal from the Motorola GPS receiver albeit without sawtooth correction. You won't need sawtooth correction if you set the PRS-10 time constant to say 10,000 seconds. bye, Said In a message dated 5/1/2012 10:55:34 Pacific Daylight Time, mspencer12...@yahoo.ca writes: Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer ___ 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] Trimble recommends RG-59 Antenna Cable.
Make sure to buy the quadrouple shielded 75 Ohms RG-6 cable from Home Depot etc, it's much better than the standard single or double shielded RG-6 and works wonders for GPS signals, and it's quite inexpensive. Impedance mismatch loss can be neglected, and long cable runs can be made. bye, Said In a message dated 4/30/2012 13:14:15 Pacific Daylight Time, azelio.bori...@screen.it writes: Yes, I use the regular satellite TV cable: low loss, easy to find and cheap. On Mon, Apr 30, 2012 at 8:22 PM, Don Latham d...@montana.com wrote: My TrueTime gps rcvr uses rg-59 as well. Don Robert Atkinson Hi Ken, This is correct. Some other documents explain the rationale. Basically for long runs the loss caused by the mismatch is less than the higher loss per foot of 50R coax of a similar size. Even better than RG59 is the high performance cable used for cable TV and satellite installations. This is cheap and low loss at 1.5GHz. This also also explains the F connector on the Thunderbolt. It would also be intersting to measure the actual impedance of some GPS receivers and antennas. Robert G8RPI. ___ 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.
