Re: [time-nuts] Switching 1 pps signal
I should have mentioned this clearly earlier, but all converting and switching, then measuring happens in ONE 2U rack case. Length of each cable is minimal. I thought mention of TICC would make it sort of clear but it didn't. I have LOTS of coax relays. I'll use them. It's a gross overkill but I've seen 80s HP equipment have overly generous parts selections, too. It's hard to explain EXACTLY as the contraption isn't built yet. That made it necessary to use generic terms. I apologize for causing confusion. --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Sunday, July 7, 2019, 12:00:52 AM EDT, Glen English VK1XX wrote: Hal, Good point. and I have never seen a spec for phase stability for Cat-7 cable ! for RG58, OR OTHER polyethylene, might be up to 150ppm /deg C. maybe as good as 10 ppm/deg C for some LMR. With 1000 feet of cable might be an issue for fine stuff. a few nano seconds each way over temperature might not matter for his project... I forget it is not a microwave RF VNA application. Easy to resolve anyway with a difference balance term somewhere. g On 7/07/2019 11:23 AM, Hal Murray wrote: >> coax cables are in general NOT PHASE STABLE with temperature, either. > Is twisted pair any better? > > > ___ 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] Switching 1 pps signal
--- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Sunday, July 7, 2019, 12:00:52 AM EDT, Glen English VK1XX wrote: Hal, Good point. and I have never seen a spec for phase stability for Cat-7 cable ! for RG58, OR OTHER polyethylene, might be up to 150ppm /deg C. maybe as good as 10 ppm/deg C for some LMR. With 1000 feet of cable might be an issue for fine stuff. a few nano seconds each way over temperature might not matter for his project... I forget it is not a microwave RF VNA application. Easy to resolve anyway with a difference balance term somewhere. g On 7/07/2019 11:23 AM, Hal Murray wrote: >> coax cables are in general NOT PHASE STABLE with temperature, either. > Is twisted pair any better? > > > ___ 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] Switching 1 pps signal
Hal, Good point. and I have never seen a spec for phase stability for Cat-7 cable ! for RG58, OR OTHER polyethylene, might be up to 150ppm /deg C. maybe as good as 10 ppm/deg C for some LMR. With 1000 feet of cable might be an issue for fine stuff. a few nano seconds each way over temperature might not matter for his project... I forget it is not a microwave RF VNA application. Easy to resolve anyway with a difference balance term somewhere. g On 7/07/2019 11:23 AM, Hal Murray wrote: coax cables are in general NOT PHASE STABLE with temperature, either. Is twisted pair any better? ___ 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] FEI 405B oscillators
Hi, I have one of these FEI405 oscillators from this list auction 4 years ago. While it dives nicely down deep into E-13 land over some seconds, it only delivers -2.5 dBm output power and has a lot of phase noise and spurs far out. That does not look healthy. Is there a real data sheet out there in the wild, or has someone even re-engineered this thing? If you google for it, you get links to Fender guitar bags, fertilizers and electron microscopes, but nothing on oscillators apart of the time nuts thread from 4 years ago. If the data sheet really says -2 dBm, then I could get rid of the spurii and life would be OK. Yes, I have found the Frequency Electronics web site, but it seems they deny parenthood. Gerhard ___ 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] Switching 1 pps signal
> coax cables are in general NOT PHASE STABLE with temperature, either. Is twisted pair any better? -- These are my opinions. I hate spam. ___ 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] 60Khz received on Wide-band WebSDR
The SD keyboard command in the latest versions of Lady Heather will give you the distance and bearing from your antenna to a specified location along with an estimate of the prop delay and number of ionospheric hops. You can specify the location either as lat/lon or the station name... the command prompt shows a list of supported VLF time stations. -- > For SDR transmitters all over the world... ___ 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] E1938A source code/ firmware
Hi The gotcha with averaging multiple GPS modules is that there are a lot of common mode issues present. The averaging will help with the random noise stuff, but will not do much for the atmosphere, ephemeris, and other “external” limits. Unfortunately those limits are pretty significant contributors. More or less: Sawtooth you can (and should) take care of with the correction information from the module. No need to average there. Random “I pick this / you pick that” stuff as constellations change will average out. ( = different signal to noise numbers will be present in the voting process on each module). You can see nanosecond level bumps from this. Since they are transient, exactly how much they contribute to a long term average is debatable. Ionosphere modeling errors will be the same for any rational group of modules running on the same system in the same area. The same is true of troposphere related issues. These can (but don’t always) get into the 10’s of nanosecond range. They can last long enough to pass through normal long averaging filters. The solutions are based on orbit and clock data broadcast in the ephemeris. Both can be off by nanoseconds. Again, they are long term so they pas through averaging filters. Probably better to focus on an ensemble of OCXO’s to lower the “local” noise floor: As you sum independent devices, it is reasonable to expect things like ADEV to improve by the square root of the number of devices. One limit to this is (as mentioned above) common mode issues. With OCXO’s temperature would be a common mode item. Controlling or correcting it would be a good idea. A group of 4 OCXO’s in some sort of controlled enclosure could indeed be 2X better than a single OCXO. Going up to 16 might get you 4X better. That range probably covers the range (even at eBay prices) that one would be working in. Improvements of this sort have been demonstrated in various (expensive) systems. The same principle would apply to things like telecom Rb’s, but at a bit higher price. I do not know of any commercial system doing that. Bob > On Jul 6, 2019, at 7:00 PM, Glen English VK1XX > wrote: > > OK, good info, thanks. > > Well I have bought 7 x E1938As, with the intention of building a better GPSDO. > > My interest in the E1938A firmware hex was if I had to replace any of the > PICs at sometime in the future. > > My intention is to use the average of multiple stationary mode GPS 1PPS > signals to drive a single OCXO, the idea to be a better 1pps estimate. I'll > upsample the inputs to get the control sample rate up. > > Eventually I want to explore the use multiple OCXOs, but not until I think of > a good way to take an average of multiple OCXOs, or, even if that is a useful > idea. > > FPGA based, I'll put the OCXO drive and the 1ppS to the FPGA differentially > into maybe 8 FPGA inputs (that is each signal into 8 different FPGA pin > pairs) , and use IDELAY blocks to delay the 8 different inputs to provide > more edge resolution for each signal . The IDELAY blocks can be dynamic but > I'll probably use then fixed. output of the FPGA can be sigma-delta > converter, which can provide almost arbritary number of bits. LVDS output of > the 1 bit FPGA converter signal will go to an outboard LVDS buffer with its > own power supply so bumps on FPGA VCCIO dont affect the output. > > So first, I'll need to build a frequency/period counter in the same ilk > (same PCB) > > I'll make these PCBs loaded available to all. > > I have a protoype built and output at the moment is HD44780 LCD drive 8 bit > bus to surplus 40x4 char displays I have around here. and also a serial > stream output. best to do only what is necessary on the FPGA (rudimentary > time/frequency output onto the LCD) , and feed data to an analysis machine, > RPI, PC whatever for analysis and display in Python 2.7X. > > comments welcome. > > -glen VK1XX / AI6UM > > On 6/07/2019 10:06 PM, Adrian Godwin wrote: >> I would agree that antiwindup is important when you have integrators. They >> always seem to cause trouble without it, in applications as diverse as car >> throttle control and time-domain filtering of respiratory data. I would >> also recommend, sometimes, the use of feed-forward control to provide an >> estimate of power demand without relying on the integrator : although most >> useful for speeding the response, it can also reduce th > > > > ___ > 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.
[time-nuts] Advantages of GNSS ???
Here is screen grab of an F9T tracking GPS/GLONASS/GALILEO/BEIDOU. In the max sig level display the sats that the F9T says do L2 ionospheric corrections are shown in GREEN. Note that the F9T thinks that it is seeing signals from PRNs 192..202 These are the Japanese QZSS sat PRNs. Obviously, these are not visible from the USA. I'm not sure why it thinks it sees signals from these. Perhaps its correlators ate tricked by signals from other sats. It never actually tracks them. --- > On the F9P you have the specific issue of L1 / L2 with older GPS satellites. > The device only does L2C. That cuts the “population” roughly in half.___ 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] It is possible to "recharge" a hydrogen maser?
Hi Luis, I have experience with the NASA NR series if that’s what you have. Blue and about the size of a household fridge, wth lovely 80s red LEDS on the front. If it is this model, I’d expect it is more likely that your ion pump(s) need replacing. I can send all the documentation you need. Jim On Sat, 6 Jul 2019 at 3:01 am, Luiz Paulo Damaceno < luizpauloeletric...@gmail.com> wrote: > Hi friends, > > We have a hydrogen maser here at the university that i work. It seems the > hydrogen is over. This is possible? If yes, It is possible to recharge It? > > Best regards, > > Luiz. > ___ > 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] Switching 1 pps signal
I thoroughly agree with Bob. Suggest converting 1pps into something hardy like LVDS or LVPECL and using twisted pair , Cat 7 (individually shielded pairs and controlled skew cable) , or a pair of coax (balanced coax). The balanced signals will deal with the chance of power supply differences, and attach the shields of the balanced pairs to local ground with 10nF caps of something If there are different earth potentials at each end (different power circuits), where the differential receivers end up running out of common mode headroom, the balanced signals will work nicely with ethernet transformers . (LF caveat) . coax cables are in general NOT PHASE STABLE with temperature, either. or if lightning is a problem, convert and drive a fibre optic . that's another story, you can use the SFP modules that have GHz of bandwidth but be wary of their internal optical AGC and thus may not extend to DC. glen. On 7/07/2019 8:52 AM, Bob kb8tq wrote: Hi Indeed the fast rise time of just about any modern digital signal gets energy up into the GHz region. Isolation wise, the simple answer is often to just disable the signal when not in use. In a one at a time system, that takes care of cross talk / feed through. There are a lot of “always on" devices out there that suffer from blips on (say) the 10 MHz output each time the (maybe) 1 pps edge goes out …. disabling signals at the sourcre isn’t always an option. The other half of the problem is how to get the signal to its destination when it *is* in use. Coax (with some sort of drive that will handle a 50 ohm load) is usually the answer for long runs. For shorter runs simple twisted pair works ok. For very short runs a trace on a board or a jumper wire may be all you need. So now, what are the dimensions on all those really vague terms? Long (as in coax) is up into the 10’s of feet and down range. Shorter (as in twisted pair is in the 5 feet and down range, with a foot or two being pretty safe. Anything in the “couple inches” range is territory for a wire or simple trace on a board. The two issues (isolation and integrity ) are not completely independent of each other. In many cases you both need isolation *and* a good signal. In those cases, the mumble mumble mumble lengths above get a bit shorter. Just how short depends on just how good the isolation needs to be. Coax runs in the “under a foot” range are not unheard of. Further complicating this is the fact that you can get fancy twisted pair setups that are fine for longer runs. You can get really crummy coax that isn’t good for anything. There are always ways to route traces or bundle wires that will get you in trouble. Lots of fun and lots of rabbit holes to wander down …. Bob ___ 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] E1938A source code/ firmware
OK, good info, thanks. Well I have bought 7 x E1938As, with the intention of building a better GPSDO. My interest in the E1938A firmware hex was if I had to replace any of the PICs at sometime in the future. My intention is to use the average of multiple stationary mode GPS 1PPS signals to drive a single OCXO, the idea to be a better 1pps estimate. I'll upsample the inputs to get the control sample rate up. Eventually I want to explore the use multiple OCXOs, but not until I think of a good way to take an average of multiple OCXOs, or, even if that is a useful idea. FPGA based, I'll put the OCXO drive and the 1ppS to the FPGA differentially into maybe 8 FPGA inputs (that is each signal into 8 different FPGA pin pairs) , and use IDELAY blocks to delay the 8 different inputs to provide more edge resolution for each signal . The IDELAY blocks can be dynamic but I'll probably use then fixed. output of the FPGA can be sigma-delta converter, which can provide almost arbritary number of bits. LVDS output of the 1 bit FPGA converter signal will go to an outboard LVDS buffer with its own power supply so bumps on FPGA VCCIO dont affect the output. So first, I'll need to build a frequency/period counter in the same ilk (same PCB) I'll make these PCBs loaded available to all. I have a protoype built and output at the moment is HD44780 LCD drive 8 bit bus to surplus 40x4 char displays I have around here. and also a serial stream output. best to do only what is necessary on the FPGA (rudimentary time/frequency output onto the LCD) , and feed data to an analysis machine, RPI, PC whatever for analysis and display in Python 2.7X. comments welcome. -glen VK1XX / AI6UM On 6/07/2019 10:06 PM, Adrian Godwin wrote: I would agree that antiwindup is important when you have integrators. They always seem to cause trouble without it, in applications as diverse as car throttle control and time-domain filtering of respiratory data. I would also recommend, sometimes, the use of feed-forward control to provide an estimate of power demand without relying on the integrator : although most useful for speeding the response, it can also reduce th ___ 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] Switching 1 pps signal
Taka, It depends on the edge rate of the driver. You wont need an 18 GHz relay. The edge rate of the driver depends on many things, but it is likely not to be any faster than 1V/nS Now in all the trimbles I worked with, the falling edge , actively pulled to ground was the line with the deterministic transition time. Using 0.35 = Btr, the bandwidth is approx 350 MHz . the likelyhood is, with the way things are connected, the lack of any termination from the single ended pps signal etc, the bandwidth is unlikely to exceed 50 MHz. You may be well advised to atttempt to terminate the 1pps signal to provide a deterministic edge rate and control crosstalk and reflections. If you have short cables, the reflection bouncing around may cause jitter if the edge rate was low enough. . However, do be mindful of crosstalk from the alternate switch contact. The cross talk will be extremely low for signals up to 500 MHz for a good coaxial relay, especially into a high Z load. The high Z load will permit crosstalk due to the capacitance ont he relay contacts, so another good reason to hold the input resistance of the load of the 1pps down to less than a few hundred ohms You do have to be careful of rising crosstalk using ADG901 etc solid state switches . A logic multiplexer might be a good choice if the jitter introduced is not an issue. glen On 7/07/2019 4:06 AM, Taka Kamiya via time-nuts wrote: I am trying to come up with a viable design to encase TICC along with 10MHz -> 1 pps converter. My plan is to share the input connector and switch in/out the converter. 1 pps, although technically a 1Hz signal, rise time and duration is awfully short on some sources. I'm sure constituent signal will go way into RF range. I am not capable of calculating this. But, that means I really have to treat it as an RF signal, correct? Otherwise, slower rise will cause error as it will cross the threshold later than initiation of the pulse. Question is, how careful do I need to be? My plan is to use two 18GHz microwave relay per channel to bypass/place-in the converter. I know this would be OK but am I over-doing this? I also have a miniature relay in DIP size but I'm afraid it may not be sufficient. There is not a frequency spec, and consistency may be an issue. Advise, please? --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG ___ 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] Switching 1 pps signal
Hi Indeed the fast rise time of just about any modern digital signal gets energy up into the GHz region. Isolation wise, the simple answer is often to just disable the signal when not in use. In a one at a time system, that takes care of cross talk / feed through. There are a lot of “always on" devices out there that suffer from blips on (say) the 10 MHz output each time the (maybe) 1 pps edge goes out …. disabling signals at the sourcre isn’t always an option. The other half of the problem is how to get the signal to its destination when it *is* in use. Coax (with some sort of drive that will handle a 50 ohm load) is usually the answer for long runs. For shorter runs simple twisted pair works ok. For very short runs a trace on a board or a jumper wire may be all you need. So now, what are the dimensions on all those really vague terms? Long (as in coax) is up into the 10’s of feet and down range. Shorter (as in twisted pair is in the 5 feet and down range, with a foot or two being pretty safe. Anything in the “couple inches” range is territory for a wire or simple trace on a board. The two issues (isolation and integrity ) are not completely independent of each other. In many cases you both need isolation *and* a good signal. In those cases, the mumble mumble mumble lengths above get a bit shorter. Just how short depends on just how good the isolation needs to be. Coax runs in the “under a foot” range are not unheard of. Further complicating this is the fact that you can get fancy twisted pair setups that are fine for longer runs. You can get really crummy coax that isn’t good for anything. There are always ways to route traces or bundle wires that will get you in trouble. Lots of fun and lots of rabbit holes to wander down …. Bob > On Jul 6, 2019, at 2:06 PM, Taka Kamiya via time-nuts > wrote: > > I am trying to come up with a viable design to encase TICC along with 10MHz > -> 1 pps converter. My plan is to share the input connector and switch > in/out the converter. > > 1 pps, although technically a 1Hz signal, rise time and duration is awfully > short on some sources. I'm sure constituent signal will go way into RF > range. I am not capable of calculating this. But, that means I really have > to treat it as an RF signal, correct? Otherwise, slower rise will cause > error as it will cross the threshold later than initiation of the pulse. > Question is, how careful do I need to be? > My plan is to use two 18GHz microwave relay per channel to bypass/place-in > the converter. I know this would be OK but am I over-doing this? I also > have a miniature relay in DIP size but I'm afraid it may not be sufficient. > There is not a frequency spec, and consistency may be an issue. > Advise, please? > > --- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > ___ > 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] Are there any company selling refurbished/reconditioned Cesium tubes?
thanks Corby, and all, for their beam tube buying advice. On 7/07/2019 4:34 AM, cdel...@juno.com wrote: When evaluating an instrument with a used tube the beam current is not the best indicator to look at! For an HP instrument If the tube label has the EM voltage listed then with the beam current set to it's proper level check the current EM voltage. As the tube ages you will require more and more EM voltage to bring the gain back to nominal. Also performing a SN test on the tube or even a quick look at the peak/valley/background levels is helpful. Cheers, Corby ___ 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] Advantages of GNSS ???
Hello Luiz, (Did we meet at IFCS-EFTF in Orlando? If so, my apologies for not remembering your name, and for repeating here what you know). I presented some preliminary time-transfer data for the F9P at IFCS and wrote a short paper for the proceedings; if you’d like a copy, I am happy to send you one. For any other time-nuts interested in post processed GNSS time -transfer: Since the conference, I have been working on and off on adding dual frequency support to OpenTTP ( www.openttp.org), principally for the F9P/T and have four F9P receivers under test. The aim is to have a nice long data set for EFTF next year. Cheers Michael On Sat, 6 Jul 2019 at 2:02 pm, Luiz Paulo Damaceno < luizpauloeletric...@gmail.com> wrote: > Hey Graham, > > I'm gonna start a project soon to evaluate a F9P as a Time Transfer GNSS > receiver. For now i haven't too much answers for you but only i know is: > the BIPM uses all labs that participate from UTC to make corrections of > GNSS satellites frequency, also for the TAI use. I think GNNS T&F is a good > and reliable source for many projects. Here in my lab with Septentrio's > Pola RX 3 Tr we have a very low Time Dilution Of Precision when the Glonass > and all anothers becomes enabled, so our frequency if compared to all GNSS > constallations is good, i think the same logic can be applied for frequency > generation / distribution. What i want to say is: with more satellites of > different constellations you can have a better end signal (more stable and > reliable). Tests should be done. I hope can help more in the future. > > Best regards, > > Luiz > > Em sex, 5 de jul de 2019 às 23:00, Graham / KE9H > escreveu: > > > I have several questions for the group, since there are several members > > that have been able to start evaluating the uBlox F9P and perhaps the F9T > > GNSS receivers. > > > > For the purposes of time and frequency determination, is there an > advantage > > to using the GNSS receivers, relative to just the US GPS? > > > > It appears that a really good GPS (only) based GPSDO can get into the > 1e-11 > > and perhaps the 1e-12 accuracy range. > > > > Does using the signals from GPS (USA), plus GLONASS (Russia), plus Beidou > > (China), and plus Galileo (Europe), actually provide any improvement in > > time/frequency accuracy? > > > > Is that what the F9P actually does, or only some sub-combinations of the > > above? > > > > Down at that level of accuracy, do the four systems agree within 1 e-12, > > anyway? > > > > Is there any advantage to using the GNSS for time/frequency? > > > > Does using the RTCM Corrections, needed to achieve the ~ 1 cm positioning > > accuracy also improve time/frequency accuracy? > > > > The underlying question I am trying to get at is: Will a GNSS based GPSDO > > have any advantage over a GPS-only, or a dual band L1/L2 GPS-only GPSDO? > > > > Thanks, > > --- Graham > > > > == > > ___ > > 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. > ___ 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] Advantages of GNSS ???
On Fri, 5 Jul 2019 19:49:59 -0500 "Graham / KE9H" wrote: > Does using the signals from GPS (USA), plus GLONASS (Russia), plus Beidou > (China), and plus Galileo (Europe), actually provide any improvement in > time/frequency accuracy? There are multiple angles to this: 1) Galileo offers the widest bandwidth signal (E5a+b) of all the currently fully operational GNSS services. This brings huge advantages when it comes to mitigating multi-path (the largest contributor to uncertainty, even before ionospheric delay if you have a non-optimal antenna position). GPS, as far as I am aware of, has no plans for any such wide bandwith signal. 2) Galileo is currently the only service that has full L1+L5 coverage. It will take GPS a couple of years until there are enough block III birds up there to offer a similar coverage on L5. Where a couple is probably in the order of 10-20 years, if not longer (GPS satellites are too well made and don't die quickly enough). While L1+L2 works similarly well for ionospheric free solutions, L2 is not a protected GNSS band (it's even secondary user in some ITU regions) and may get interference from radar systems and microwave links. L5 is a protected GNSS band. Additionally, L2C (the civil L2 GPS signal) is currently only broadcast from 19 satellites. While this should probably be enough for a lot of cases, it does not provide full coverage of earth yet. My guess for full coverage (ie 24 birds with L2C) is in the order of 3-8 years. 3) If you are doing common-view time transfer, then you want to have as many visible satellites as possible to decrease errors due to noise and atmospheric disturbances. Thus having GPS+Galileo+Glonass+Beidu helps. Similar things apply for all-in-view time transfer. 4) Only GPS and Glonass are sofar in the standard IGS products. Galileo is only in the experimental MGES products. There aren't enough Beidu receivers out there to reasonably use Beidu for IGS yet. 5) Galileo has hydrogen masers as clocks, which offer improved stability compared to the rubidium masers (which all other GNSS use). But whether this actually results in better performance, I do not know. I'm sure there are studies on this out there, but I have not read any yet. 6) All but GPS and Glonass are fairly new systems and have not all kinks ironed out yet. While the Galileo quaterly performance reports look good, that does not mean that there aren't any hickups that might or might not trip up your receiver. Similar concerns can be raised for Beidu, which has the additional disadvantage, that it has been developed with a lot of secrecy around it. Ie a lot of the potential system performance analysis that scientists performed for GPS, Glonass and Galileo is missing for Beidu. 7) Local satellite based augmentation systems like QZSS, IRNSS, Beidu (the China-only part) give additional satellites that are high up in the sky, thus allowing to see additional satellites in urban areas (eg QZSS has one satellite at elevations >60° at all times). Attila Kinali -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ 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] Is it possible to "recharge" hydrogen maser?
An H-maser works by continuously bleeding a beam of monatomic hydrogen into the system. This gas has to be continuously 'pumped' out. The ion pumps used don't have an outlet port. They work by burying the H2 gas in titanium plates. Thus as Ole Ronningen says the pumps have a finite working life which is reached when they are swollen with gas. If you need to replace old plates you must find someone who can manufacture them for you if the original supplier no longer exists. I think the new plates must be 'activated' by heating them as hot as possible in ultra-high vacuum until they no longer outgas and then of course allowing them to cool to room temeprature whilst still under vacuum. I guess it is possible, though I've never heard of it being done, to revive old plates by the same treatment. The hydrogen coming into the system may come from a standard 'lecture bottle' of ordinary molecular H2. Alternatively it may come from heating a can of H2 stored in solid solution in a metal hydride. It can also come from electrolysis of water. One can run an H-maser on water! These two latter options may be used on masers intended for air transportation as the airlines are understandably scared of cylinders of hydrogen gas. The hydrogen gas is reduced in pressure to perhaps twice atmospheric by an ordinary pressure indicating regulator, and is then further regulated and purified by passing it through a membrane of either palladium-silver alloy or perhaps nickle. I think most western masers use palladium-silver but the KVARZ masers use nickel. I only have experience of palladium-silver. At room temperature it is a complete barrier to hydrogen but when heated it allows hydrogen to diffuse through. I understand that it allows H2 and only H2 to diffuse through: actually as free protons. So it acts as a purifier keeping out all other gasses and is even as an isotopic filter blocking deuterium. Thus ordinary commercial grade H2 can be used. It doesn't have to be isotopically pure or especially free of contaminants. The flow rate is controlled smoothly and without hysteresis by varying the temperature of the palladium 'leak/valve'. One uses a miniature thermistor as a Pirani gauge on the low pressure side of the membrane to sense the pressure. This may be used as an arm in a wheatstone bridge run at constant voltage, in which case the out-of-balance voltage is a measure of the H2 pressure, or as I did, run the thermistor at constant temperature by varying the bridge voltage to keep it balanced so that the bridge voltage becomes the measure of the pressure: the lower the pressure the lower the bridge voltage. The low pressure (~1torr) H2 then passes to the RF 'dissociator' which turns the H2 to monatomic H which is what actually powers the maser proper. Blind ended thin walled Palladium-silver tubes about 1.5mm OD and about 40mm long, described by Vanier and Audoin* as 'glove fingers', can be conveniently used. Something like 1A passed through them heats them to produces a suitable H2 flow rate (~10E^16 atoms per sec) . The high pressure hydrogen is applied to the inside and the low pressure or vacuum side is the outside. Anders Wallin describes a procedure involving cooling the new hydrogen bottle in liquid nitrogen. I think this would be an extremely dangerous as well as a pointless thing to do with an ordinary cast-iron 'lecture bottle' of high pressure gas. I think what he describes may be appropriate to changing a can of metal hydride. Dana Whitlow is correct is saying that getting a new ion pump to start is a lengthy process. One needs to get the vacuum pressure down to about 10E^-6 torr by other means. Then on turning on the ion pump very soon the pressure will rise as the titanium plates heat up and outgas. Once the pressure has fallen one tries again. This time it takes a bit longer before the outgassing makes the pressure rise. One has to go on doing this for an hour or several hours before the pressure no longer rises but instead falls. The pressure should get to about 10E^-8 torr with the hydrogen beam turned off. I hope this helps. Regards John P * The Quantum Physics of Atomic Frequency Standards. Jacques Vanier and Claude Audoin. ___ 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] 60Khz received on Wide-band WebSDR
No longer at Rugby, now at Anthorn: GBR: longitude -3.28latitude 54.91 "Poul-Henning Kamp" wrote: > In message > , > "D. Resor" writes: > > > > From another list I was directed to this link for those who do not > > > have a > > shortwave radio. > > > > http://websdr.ewi.utwente.nl:8901/ > > > > I entered the frequency of 60Khz and am curious to know if this the WWVB > > transmission I am hearing or something else? > > No, that is the UK Rugby transmitter. > > For SDR transmitters all over the world, mainly John's KiwiSDR, visit > http://sdr.hu > -- Brian Duffell YarmEngland ___ 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] Switching 1 pps signal
I am trying to come up with a viable design to encase TICC along with 10MHz -> 1 pps converter. My plan is to share the input connector and switch in/out the converter. 1 pps, although technically a 1Hz signal, rise time and duration is awfully short on some sources. I'm sure constituent signal will go way into RF range. I am not capable of calculating this. But, that means I really have to treat it as an RF signal, correct? Otherwise, slower rise will cause error as it will cross the threshold later than initiation of the pulse. Question is, how careful do I need to be? My plan is to use two 18GHz microwave relay per channel to bypass/place-in the converter. I know this would be OK but am I over-doing this? I also have a miniature relay in DIP size but I'm afraid it may not be sufficient. There is not a frequency spec, and consistency may be an issue. Advise, please? --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG ___ 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] Are there any company selling refurbished/reconditioned Cesium tubes?
When evaluating an instrument with a used tube the beam current is not the best indicator to look at! For an HP instrument If the tube label has the EM voltage listed then with the beam current set to it's proper level check the current EM voltage. As the tube ages you will require more and more EM voltage to bring the gain back to nominal. Also performing a SN test on the tube or even a quick look at the peak/valley/background levels is helpful. Cheers, Corby ___ 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] It is possible to "recharge" a hydrogen maser?
The Applied Science YouTube channel had an episode where he described building a molecular sieve vacuum pump. (IIRC) On Sat, Jul 6, 2019 at 12:06 PM EB4APL wrote: > The H maser that we had at NASA-DSN in the 80´s had a small H2 bottle > which supplied it to the palladium valve, so it could be refilled. We > never needed a refill but once we had to open the plumbing, it was > necessary to reestablish the vacuum before opening the H2 valve. it was > done using a mechanical pump and then a (then unknown to me) "molecular > sieves" pump that was chilled with a bucket of liquid N2. The procedure > was quite convoluted. > > Regards, > > Ignacio > > > El 05/07/2019 a las 16:11, Luiz Paulo Damaceno escribió: > Hi friends, > > We have a hydrogen maser here at the university that i work. It seems the > hydrogen is over. This is possible? If yes, It is possible to recharge It? > > Best regards, > > Luiz. > ___ > 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. > > > > --- > El software de antivirus Avast ha analizado este correo electrónico en > busca de virus. > https://www.avast.com/antivirus > > > ___ > 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.
[time-nuts] It is possible to "recharge" a hydrogen maser?
Luiz, Once I know the model number of the Maser I can give some advice. I recharged the Hydrogen bottle of the EFOS2 Maser 4 times in the past with no problem. Really depends on the method of Hydrogen storage and if they made provision for field repair, I.E. threaded fittings vice welded joints. Cheers, Corby ___ 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] 60Khz received on Wide-band WebSDR
Would likely be the UK MSF signal. /Björn Sent from my iPhone > On 6 Jul 2019, at 14:39, D. Resor wrote: > > From another list I was directed to this link for those who do not have a > shortwave radio. > > http://websdr.ewi.utwente.nl:8901/ > > I entered the frequency of 60Khz and am curious to know if this the WWVB > transmission I am hearing or something else? > > > Donald Resor > N6KAW > > > ___ > 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] 60Khz received on Wide-band WebSDR
Hello Donald, That website is in the Netherlands (aka Holland), and so no, what it hears on 60Khz is the English MSF transmission from Anthorn in Cumbria, in the north-west of England. See the National Physical Laboratory's website page at: https://www.npl.co.uk/msf-signal Regards, Peter Vince On Sat, 6 Jul 2019 at 17:06, D. Resor wrote: > From another list I was directed to this link for those who do not have a > shortwave radio. > > http://websdr.ewi.utwente.nl:8901/ > > I entered the frequency of 60Khz and am curious to know if this the WWVB > transmission I am hearing or something else? > > > Donald Resor > N6KAW > > > ___ > 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] 60Khz received on Wide-band WebSDR
Don I think I have used that site and radio also. However its in Europe and the 60 KHz you are hearing is Rugby England. Go up to 77.5, if a signal is there (DCF) then you are receiving European signals. Regards Paul WB8TSL On Sat, Jul 6, 2019 at 12:06 PM D. Resor wrote: > From another list I was directed to this link for those who do not have a > shortwave radio. > > http://websdr.ewi.utwente.nl:8901/ > > I entered the frequency of 60Khz and am curious to know if this the WWVB > transmission I am hearing or something else? > > > Donald Resor > N6KAW > > > ___ > 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] 60Khz received on Wide-band WebSDR
In message , "D. Resor" writes: >>From another list I was directed to this link for those who do not have a >shortwave radio. > >http://websdr.ewi.utwente.nl:8901/ > >I entered the frequency of 60Khz and am curious to know if this the WWVB >transmission I am hearing or something else? No, that is the UK Rugby transmitter. For SDR transmitters all over the world, mainly John's KiwiSDR, visit http://sdr.hu -- 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@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] 60Khz received on Wide-band WebSDR
From another list I was directed to this link for those who do not have a shortwave radio. http://websdr.ewi.utwente.nl:8901/ I entered the frequency of 60Khz and am curious to know if this the WWVB transmission I am hearing or something else? Donald Resor N6KAW Donald, Given the location, most likely 60 kHz MSF: https://www.npl.co.uk/msf-signal There's a German signal on 77.5 kHz which can be heard on that receiver too. 73, David GM8ARV -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ 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] It is possible to "recharge" a hydrogen maser?
The H maser that we had at NASA-DSN in the 80´s had a small H2 bottle which supplied it to the palladium valve, so it could be refilled. We never needed a refill but once we had to open the plumbing, it was necessary to reestablish the vacuum before opening the H2 valve. it was done using a mechanical pump and then a (then unknown to me) "molecular sieves" pump that was chilled with a bucket of liquid N2. The procedure was quite convoluted. Regards, Ignacio El 05/07/2019 a las 16:11, Luiz Paulo Damaceno escribió: Hi friends, We have a hydrogen maser here at the university that i work. It seems the hydrogen is over. This is possible? If yes, It is possible to recharge It? Best regards, Luiz. ___ 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. --- El software de antivirus Avast ha analizado este correo electrónico en busca de virus. https://www.avast.com/antivirus ___ 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] E1938A source code/ firmware
I would agree that antiwindup is important when you have integrators. They always seem to cause trouble without it, in applications as diverse as car throttle control and time-domain filtering of respiratory data. I would also recommend, sometimes, the use of feed-forward control to provide an estimate of power demand without relying on the integrator : although most useful for speeding the response, it can also reduce the expected integrator term and hence allow more aggressive antiwindup. On Sat, Jul 6, 2019 at 9:00 AM Glen English VK1XX < glenl...@pacificmedia.com.au> wrote: > Hi Rick > > Thank you very much for the reply and the suggested leads. I think your > work on the balanced bridge oscillator was both preeminant and seminal . > > I have read all the papers on it, and there are few other things in my > 30 years of this field professionally that really impress me as much in > the new approaches and new thinking on the entire unit. Agreed on the > PII^2D control system. > > I've built a few OCXOs back in the 90s, the best I did on (inner) oven > control was using dual glass bead thermistors in a bridge configuration > with lots of gain driving a simple opamp integrator. The opamp was > chopper stabilized and I ensured the op amp never operated in the > crossover region of the opamp output driver. These were on AT cuts at > 97 deg C ... > > cheers > > Glen. AI6UM / VK1XX > > > > On 6/07/2019 2:37 PM, Richard (Rick) Karlquist wrote: > > On 7/5/2019 8:20 PM, Glen English VK1XX wrote: > >> Has anyone got this , is the PIC read data prohibited ? > >> > >> Is it still a closely guarded secret?, there were some very clever > >> and novel ideas used in that slab, in my opinion. > >> > >> Glen > >> > > > > Hi Glen. I worked on this project, but am an RF/Analog > > guy. The product line was sold to Symmetricom 20 years > > ago and they didn't continue the E1938A. At that point, > > there were no closely guarded secrets. I don't know what > > happened to the source code. The last contract manufacturer > > for the E1938A was Scotts Valley Magnetics. You could > > contact them and see if they have the PIC info. In theory, > > they would have had to have it to program the PIC's. > > > > The most clever thing in the PIC (AFAIK) is the oven > > controller with the double integrator. "P, I, I^2, D". > > Len Cutler was the mastermind behind this. I believe > > he leveraged his experience with double integrators used > > in Cs control loops. I remember him telling me that the > > secret was to have an "anti-windup" algorithm. Whatever > > he did, the results were phenomenal. I spent countless > > days in the lab exercising the loop and it always worked > > perfectly. > > > > Rick Karlquist, N6RK > > > > > > ___ > 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] Advantages of GNSS ???
Hi On the F9P you have the specific issue of L1 / L2 with older GPS satellites. The device only does L2C. That cuts the “population” roughly in half. This is not a great thing for a “GPS only” setup with that device. BIPM does not directly control or feed timing into the various GNSS systems. They do use highly specialized gear to do time transfer. Some of that is via GNSS sats. What they do is a bit different than what a typical timing user would do. Frequency of any GNSS output on the F9P is limited by the accuracy of the time pulse. Correction is only done once a second. The same “fraction of a nanosecond” sort of wobble you see in time gets you a “fraction of a PPB” frequency wobble. You will need a local standard to discipline in order to do very well. A commercial GPSDO is one way to do this. There are other approaches. Indeed this is just the first layer or two of the list of fun you are going to have :) Bob > On Jul 5, 2019, at 11:19 PM, Luiz Paulo Damaceno > wrote: > > Hey Graham, > > I'm gonna start a project soon to evaluate a F9P as a Time Transfer GNSS > receiver. For now i haven't too much answers for you but only i know is: > the BIPM uses all labs that participate from UTC to make corrections of > GNSS satellites frequency, also for the TAI use. I think GNNS T&F is a good > and reliable source for many projects. Here in my lab with Septentrio's > Pola RX 3 Tr we have a very low Time Dilution Of Precision when the Glonass > and all anothers becomes enabled, so our frequency if compared to all GNSS > constallations is good, i think the same logic can be applied for frequency > generation / distribution. What i want to say is: with more satellites of > different constellations you can have a better end signal (more stable and > reliable). Tests should be done. I hope can help more in the future. > > Best regards, > > Luiz > > Em sex, 5 de jul de 2019 às 23:00, Graham / KE9H > escreveu: > >> I have several questions for the group, since there are several members >> that have been able to start evaluating the uBlox F9P and perhaps the F9T >> GNSS receivers. >> >> For the purposes of time and frequency determination, is there an advantage >> to using the GNSS receivers, relative to just the US GPS? >> >> It appears that a really good GPS (only) based GPSDO can get into the 1e-11 >> and perhaps the 1e-12 accuracy range. >> >> Does using the signals from GPS (USA), plus GLONASS (Russia), plus Beidou >> (China), and plus Galileo (Europe), actually provide any improvement in >> time/frequency accuracy? >> >> Is that what the F9P actually does, or only some sub-combinations of the >> above? >> >> Down at that level of accuracy, do the four systems agree within 1 e-12, >> anyway? >> >> Is there any advantage to using the GNSS for time/frequency? >> >> Does using the RTCM Corrections, needed to achieve the ~ 1 cm positioning >> accuracy also improve time/frequency accuracy? >> >> The underlying question I am trying to get at is: Will a GNSS based GPSDO >> have any advantage over a GPS-only, or a dual band L1/L2 GPS-only GPSDO? >> >> Thanks, >> --- Graham >> >> == >> ___ >> 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. ___ 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] 60Khz received on Wide-band WebSDR
>From another list I was directed to this link for those who do not have a shortwave radio. http://websdr.ewi.utwente.nl:8901/ I entered the frequency of 60Khz and am curious to know if this the WWVB transmission I am hearing or something else? Donald Resor N6KAW ___ 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] E1938A source code/ firmware
On 7/5/2019 8:20 PM, Glen English VK1XX wrote: Has anyone got this , is the PIC read data prohibited ? Is it still a closely guarded secret?, there were some very clever and novel ideas used in that slab, in my opinion. Glen Hi Glen. I worked on this project, but am an RF/Analog guy. The product line was sold to Symmetricom 20 years ago and they didn't continue the E1938A. At that point, there were no closely guarded secrets. I don't know what happened to the source code. The last contract manufacturer for the E1938A was Scotts Valley Magnetics. You could contact them and see if they have the PIC info. In theory, they would have had to have it to program the PIC's. The most clever thing in the PIC (AFAIK) is the oven controller with the double integrator. "P, I, I^2, D". Len Cutler was the mastermind behind this. I believe he leveraged his experience with double integrators used in Cs control loops. I remember him telling me that the secret was to have an "anti-windup" algorithm. Whatever he did, the results were phenomenal. I spent countless days in the lab exercising the loop and it always worked perfectly. Rick Karlquist, N6RK ___ 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] E1938A source code/ firmware
Hi Rick Thank you very much for the reply and the suggested leads. I think your work on the balanced bridge oscillator was both preeminant and seminal . I have read all the papers on it, and there are few other things in my 30 years of this field professionally that really impress me as much in the new approaches and new thinking on the entire unit. Agreed on the PII^2D control system. I've built a few OCXOs back in the 90s, the best I did on (inner) oven control was using dual glass bead thermistors in a bridge configuration with lots of gain driving a simple opamp integrator. The opamp was chopper stabilized and I ensured the op amp never operated in the crossover region of the opamp output driver. These were on AT cuts at 97 deg C ... cheers Glen. AI6UM / VK1XX On 6/07/2019 2:37 PM, Richard (Rick) Karlquist wrote: On 7/5/2019 8:20 PM, Glen English VK1XX wrote: Has anyone got this , is the PIC read data prohibited ? Is it still a closely guarded secret?, there were some very clever and novel ideas used in that slab, in my opinion. Glen Hi Glen. I worked on this project, but am an RF/Analog guy. The product line was sold to Symmetricom 20 years ago and they didn't continue the E1938A. At that point, there were no closely guarded secrets. I don't know what happened to the source code. The last contract manufacturer for the E1938A was Scotts Valley Magnetics. You could contact them and see if they have the PIC info. In theory, they would have had to have it to program the PIC's. The most clever thing in the PIC (AFAIK) is the oven controller with the double integrator. "P, I, I^2, D". Len Cutler was the mastermind behind this. I believe he leveraged his experience with double integrators used in Cs control loops. I remember him telling me that the secret was to have an "anti-windup" algorithm. Whatever he did, the results were phenomenal. I spent countless days in the lab exercising the loop and it always worked perfectly. Rick Karlquist, N6RK ___ 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.
