Re: [time-nuts] Power supply for OCXO using "USB power blocks"
Nortel GPTM operates on 24 or 48V DC. Internally, there is a step down dc/dc converter and 3 terminal regulators. It creates whatever it needs internally. So it can be done. It does have quite a bit of filtering though. I have run Oven oscillators with a regular cheap switcher. Spec says ripple is 150mV p-p. I really didn't have problems using it as a reference clock. If I were to multiply it to GHz range, it would likely not work. According to spec for Wenzel Streamline, it says 15V or 12V 2.2 watts. Warm up is 5 watts at 5 minutes. Seem like one can simply get 12V battery of sufficient capacity and run with that. If I were to consider a portable operation, I would rather have gell cell batteries. It's a simple and proven technology with no catastrophic failures. I would also have it large enough so it can be started ahead of time and keep it running. --- (Mr.) Taka Kamiya I'm stuck in a wormhole Hello, worms! On Saturday, March 9, 2019, 11:03:45 PM EST, Gerhard Hoffmann wrote: Am 10.03.19 um 01:38 schrieb jimlux: > Has anyone tried a +5V to +15V DC/DC to run an OCXO, getting the 5V > from one of those rechargeable USB power bricks. I was thinking about > portable operation. > > In my case, the OCXO is something like a Wenzel streamline. I would > think that the DC/DC probably has some noise, but maybe DC/DC to a > higher voltage, then a good linear regulator to clean it up (or would > the radiated noise just leak around). > > How quiet is the output from those USB battery things..I've used one > to run a RTL-SDR, but that's hardly a ultimate low noise receiver. > That's impossible to predict. These boxes normally contain one Lithium cell and a DC/DC converter to 5V. Its output noise depends on the skill of the designer and the mood of the bean counter. It is probably not a high priority. Also, there my be "effects" from the interaction of their switcher and your's. And the efficiencies multiply. BUT: 3 of these Li cells deliver 12V in ultimate quality: < https://www.flickr.com/photos/137684711@N07/39972841815/in/album-72157662535945536/ > The squares on the paper are 5mm. Noise density is better than 1nV / rtHz above 100 Hz. You definitely need a fuse. Ishort is >> 30A. This Panasonic type is OK. There are lots of others on the market that claim twice the power capacity but it's a blatant lie. regards, Gerhard (who thinks about using a dozen of these for portable EME tests on 432 :-) ) ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for OCXO using "USB power blocks"
Am 10.03.19 um 01:38 schrieb jimlux: Has anyone tried a +5V to +15V DC/DC to run an OCXO, getting the 5V from one of those rechargeable USB power bricks. I was thinking about portable operation. In my case, the OCXO is something like a Wenzel streamline. I would think that the DC/DC probably has some noise, but maybe DC/DC to a higher voltage, then a good linear regulator to clean it up (or would the radiated noise just leak around). How quiet is the output from those USB battery things..I've used one to run a RTL-SDR, but that's hardly a ultimate low noise receiver. That's impossible to predict. These boxes normally contain one Lithium cell and a DC/DC converter to 5V. Its output noise depends on the skill of the designer and the mood of the bean counter. It is probably not a high priority. Also, there my be "effects" from the interaction of their switcher and your's. And the efficiencies multiply. BUT: 3 of these Li cells deliver 12V in ultimate quality: < https://www.flickr.com/photos/137684711@N07/39972841815/in/album-72157662535945536/ > The squares on the paper are 5mm. Noise density is better than 1nV / rtHz above 100 Hz. You definitely need a fuse. Ishort is >> 30A. This Panasonic type is OK. There are lots of others on the market that claim twice the power capacity but it's a blatant lie. regards, Gerhard (who thinks about using a dozen of these for portable EME tests on 432 :-) ) ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Power supply for OCXO using "USB power blocks"
Usually they are very noisy, with the noise rising rapidly with load current. goughlui.com, lygte-info.dk, and a few others have published some tests. I think bigclive has also done some tests. -- > How quiet is the output from those USB battery things..I've used one to run a RTL-SDR, but that's hardly a ultimate low noise receiver. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Power supply for OCXO using "USB power blocks"
Has anyone tried a +5V to +15V DC/DC to run an OCXO, getting the 5V from one of those rechargeable USB power bricks. I was thinking about portable operation. In my case, the OCXO is something like a Wenzel streamline. I would think that the DC/DC probably has some noise, but maybe DC/DC to a higher voltage, then a good linear regulator to clean it up (or would the radiated noise just leak around). How quiet is the output from those USB battery things..I've used one to run a RTL-SDR, but that's hardly a ultimate low noise receiver. jim ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Helium leaks
Jim, The He and H2 can depart from inside the device just as easily as they entered, so if put back in a normal environment, the diffusion will reverse and eventually stop at a new equilibrium point. If the parts are exposed to the nice high vacuum of free space, they should ultimately be "cleaner" inside, than when in our atmosphere. I could picture that a temporary excess of some species may upset operation, but eventually it should return to normal, unless some irreversible change or damage has occurred. I think I'd worry more about H2 (or even D2) leaking into an ionized-gas mix type of device (like Cs or Rb), and maybe reacting chemically. The He should remain inert and not leave any reaction products, and will depart eventually. In a device like a MEMS, there would be no opportunity for chemical reactions, and any excess H2 or He should return to background levels, with no harm done. I suppose it's possible for some H2 to "stick" in/on some MEMS structure parts, depending on what they're made of, and increase their mass, but it seems probably a very tiny effect if any. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] PRS-10 Warm-up Time, Calibrating/Adjusting, and long-term poweron
Hi Ok, if you are concerned about 1 us and not to concerned about 100 ns, then there’s not a lot to set up. A standard that is good to 10 ns / s will do just fine. That’s 10 ppb and a “typical” OCXO in a counter will do just fine. Leave it on for a few days and set it to frequency. There are maybe a few hundred GPS module manufacturers out there. Going through all the in’s and out’s to fiddle with each one is a major task. There *are* timing grade GPS modules out there They are “good” in the 10’s of ns without any real crazy stuff. They are good in the single digit ns with some effort. Unless this is a very large volume product, just use one of the well known parts and move on. The uBlox M8T is a modern part that will easily meet your needs. Furuno and others make parts that are at least as good. Cost wise, you are <$50 for small volume and much less in large volume. I would not bother with a part that has not been designed to do timing. They can have bugs in them that only manifest at the worst moments. (like two months later in the field). At the very least, start with a known good part to get your setup going before you mess with any thing else. These devices (at least the timing ones) all have delay adjustments on them. You can zero out any cable delays. The same is true of a TBolt. You can set it’s PPS pulse to be early or late relative to GPS time (= no leap seconds, UTC has leap seconds). This adjustment also lets you come up with a *much* easier way to test your modules. Take the TBolt and set it to be 1 us early. Put the TBolt into channel A and the device you are testing into channel B on your counter. Measure the time between the two channels. You now don’t have to worry about the standard on the counter, it’s only running for one us. The TBolt is spec’d to be < +/- 100 ns of GPS all the time. They normally wobble around by < 10 ns. Lots of fun !!! Bob > On Mar 9, 2019, at 2:04 AM, Forrest Christian (List Account) > wrote: > > This seems like as good of a message to reply to as any. Thanks to > everyone who has replied so far - lots of good information, which is > right in the category of what I was looking for. > > Let me clarify what I'm hoping to measure. I apologize if some of > the terminology below is wrong, I'm still learning correct use of some > of the terms - I've tried to explain in a way where it is obvious what > I'm talking about even if the terms are slightly wrong. > > The GPS receivers I'm hoping to measure are used in an application > where the 1PPS is used to synchronize radio transmissions. Generally > one wants the pulse to be within a couple uS or so of the top of the > second.Older radios cared less, newer ones want it to be more > precise. Sorry about the soft spec, it unfortunately is what it is. > One note is that there is some expectation that there will be be > some fixed offset from the UTC second due to cable delays and the > like, so I'm less worried about a reasonably low fixed offset and > more about the variable (jitter) offset.I.E. 1uS +-100nS is > perfectly fine, 1uS +-1uS isn't so hot. > > In evaluating a new set of GPS receivers for this application, I'm > hoping to gather Pulse-to-Pulse delay figures for every pulse the GPS > receiver outputs over a week or so. I might end up repeating it in > various forms, including moving the GPS receiver into an > "environmental chamber" (aka modified chest freezer) to verify that > they still behave in low or high temperature - or if I can figure out > a reliable way to do so, to simulate various signal impairments such > as partial sky view. > > My intent is to then process the raw data to get a feeling for the > statistical nature of the 1PPS out of that particular GPS receiver. > For instance, how many pulses were outside the +-ns spec for the > receiver. What did the histogram of the in-spec pulses look like? > And so on. For some of the processing it's pretty obvious that I need > a clock source for the TICC which is going to be stable over the > entire period or else I'll end up measuring errors in the clock source > instead of the GPS receiver.It seems to me that if I'm looking for > a histogram supposedly confined to +-100nS, I'm probably going to want > to be able to measure around +-1nS with confidence. Much more than > that (0.1nS) seems a bit excessive, less than that (10nS) is too > coarse. > > Intuition and past experience implies that if I want to measure +-1nS > with confidence, I really need a slightly more accurate clock source > than the measurement itself. 0.1ppb over the measurement period seems > reasonable, 0.2ppb is probably good enough. I don't think I need > 0.02ppb. > > I replied in particular to Bob's message below since it seems to > confirm what I was thinking, even without me being verbose enough > about my application. It also sounds like powering this on for a day > or so before I start (or
[time-nuts] US DST change proposals and WWVB radio clocks
Some US states are mulling proposals to adopt Daylight Saving Time year round -- I'm aware of California and Florida, for example. It occurs to me that if states in the Eastern time zone (UTC-5; UTC-4 in summer) adopt year-round DST, this will break WWVB-based "atomic clocks" in those states during the winter (November through early March). WWVB-based clocks currently on the market in the US offer four time zones (Pacific, Mountain, Central, and Eastern), plus an option either to move between standard and daylight time per the US-wide rules or else stay permanently on standard time. These option settings do not provide any way to specify Eastern time during winter, so in an east-coast state which moves to year-round DST, these clocks will be an hour off. Two possible solutions would be either to add a third DST setting (i.e., DST always on), or else to add a fifth time zone (Atlantic) and tell consumers in the affected states to select Atlantic time with no DST. Affected consumers would, of course, need to buy new clocks, since it's impossible to upgrade existing clocks. -- *Rich Wales* ri...@richw.org ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] PRS-10 Warm-up Time, Calibrating/Adjusting, and long-term poweron
This seems like as good of a message to reply to as any. Thanks to everyone who has replied so far - lots of good information, which is right in the category of what I was looking for. Let me clarify what I'm hoping to measure. I apologize if some of the terminology below is wrong, I'm still learning correct use of some of the terms - I've tried to explain in a way where it is obvious what I'm talking about even if the terms are slightly wrong. The GPS receivers I'm hoping to measure are used in an application where the 1PPS is used to synchronize radio transmissions. Generally one wants the pulse to be within a couple uS or so of the top of the second.Older radios cared less, newer ones want it to be more precise. Sorry about the soft spec, it unfortunately is what it is. One note is that there is some expectation that there will be be some fixed offset from the UTC second due to cable delays and the like, so I'm less worried about a reasonably low fixed offset and more about the variable (jitter) offset.I.E. 1uS +-100nS is perfectly fine, 1uS +-1uS isn't so hot. In evaluating a new set of GPS receivers for this application, I'm hoping to gather Pulse-to-Pulse delay figures for every pulse the GPS receiver outputs over a week or so. I might end up repeating it in various forms, including moving the GPS receiver into an "environmental chamber" (aka modified chest freezer) to verify that they still behave in low or high temperature - or if I can figure out a reliable way to do so, to simulate various signal impairments such as partial sky view. My intent is to then process the raw data to get a feeling for the statistical nature of the 1PPS out of that particular GPS receiver. For instance, how many pulses were outside the +-ns spec for the receiver. What did the histogram of the in-spec pulses look like? And so on. For some of the processing it's pretty obvious that I need a clock source for the TICC which is going to be stable over the entire period or else I'll end up measuring errors in the clock source instead of the GPS receiver.It seems to me that if I'm looking for a histogram supposedly confined to +-100nS, I'm probably going to want to be able to measure around +-1nS with confidence. Much more than that (0.1nS) seems a bit excessive, less than that (10nS) is too coarse. Intuition and past experience implies that if I want to measure +-1nS with confidence, I really need a slightly more accurate clock source than the measurement itself. 0.1ppb over the measurement period seems reasonable, 0.2ppb is probably good enough. I don't think I need 0.02ppb. I replied in particular to Bob's message below since it seems to confirm what I was thinking, even without me being verbose enough about my application. It also sounds like powering this on for a day or so before I start (or getting started and just throwing the first day's data away) might be reasonable to do and I don't need to let this thing run for months ahead of time to get to the accuracy I need. Of course, I'll do a bit of analysis on the data to try to verify that the unit isn't drifting. Out of curiosity, I'm also going to do some measurements on the couple of standalone OCXO's in my collection to see if either would be accurate enough for this particular measurement. The best one in my (admittedly limited) collection seems to be spec'd worse than I'd need, although I'm not sure how much aging it's done. None of them have seen any meaningful poweron time just because I've been too busy to play with them. I guess that at some point I should also up my game as far as good quality OCXO's since I do see how the right well-aged low-drift OCXO would probably be fine for this measurement. After reading everyone's response I'm still considering what to do as far as long-term runtime on the PRS10. I do know that I'm going to need this off and on for the next few months so once I get it in a permanent enclosure and get it powered up it will probably stay on continuously at least until I am done with this round of experiments, at which point it might get turned off with the hopes of extending it's service life. On Fri, Mar 8, 2019 at 8:06 AM Bob kb8tq wrote: > > Hi > > Some of this gets into just what you are trying to do. Cycle to cycle jitter > on the > PPS output of most GPS modules is in the “many ns” range. If sawtooth > correction > is not being applied, a measurement that is good to an accuracy of 1 ns / 5 = > 200 ps > would be plenty good enough. That is a 2x10^-10 (0.2 ppb) sort of accuracy. > > If you are looking at longer term effects, you may need better accuracy / > lower drift. > You can easily get past what a nice new 5071 can do heading down this road … > For > now let’s assume the target above is correct. > > The PRS-10 should be within 0.2 ppb within a few minutes after locking up. It > should > hold this sort of accuracy “on the shelf / power off” pretty much forever and > ever.
