Re: [time-nuts] time-nut conferences.
HI, I also will attend the EFTF this year in Noordwijk, for sure. I was attending the EFTF since the late 80s/early 90s, but then missed several conferences after 2000. I had attended the IFCS regularly since 1978 (!), but again very occasionally after 2000. It will be great if we can a common time slot for a time-nuts meeting. Best regards Bernd -Ursprüngliche Nachricht- Von: time-nuts [mailto:time-nuts-boun...@lists.febo.com] Im Auftrag von Attila Kinali Gesendet: Freitag, 3. Januar 2020 23:54 An: Discussion of precise time and frequency measurement Betreff: [time-nuts] time-nut conferences. On Fri, 3 Jan 2020 10:01:45 -0800 Jeffrey Pawlan wrote: > I am a very long time IEEE member of UFFS and I plan to go to the EFTF > at the ESA center in Holland in April. For some strange reason I also > see that UFFS is having a EFTS conference in Besancon, France. and > then there will be a IFCS - ISAF conference in Keystone, Colorado in July. Neither EFTF nor EFTS are UFFC or even IEEE events. EFTF is the European Frequency and Time Forum. Kind of the European counter part to PTTI. EFTF and IFCS have a joint converence every second year (in odd years). EFTS (European Frequency and Time Seminar) is a seminar/summer school organized by Enrico Rubiola. It's a one week seminar on the basics of time keeping and time/freuquency measurements. IFCS (International Frequency Control Symposium) is an IEEE converence organised by the UFFC chapter. And for completeness, there is also the NIST Time and Frequency Seminar, which is very similar to EFTS. IFCS, PTTI and EFTF overlap quite a bit and you will find mostly the same people at all three conferences, with a few differences. For whatever reason US scientists tend to stick to conferences held in the US and don't travel abroad as much as others. So IFCS/EFTF outside of the US gets smaller attendance from US people. On the other hand, conferences in the US are so expensive that a lot of people tend to prefer other conferences if IFCS is in the US. (To give you an idea how expensive: If the conference would be moved to a major city in Europe and all non-US participants would pay the airplane tickets for the US people, they would still pay less than if the conference would be held in the US) > I will come to Holland (Netherlands) in April to attend the conference > at the ESA center in Noordwijk. If you or others will be attending, > then we must meet in person. The usual supects at EFTF and IFCS are Magnus Danielson, Anders Walin, Enrico Rubiola and me. Marek Peca also used to come to EFTF, but I haven't seen or heard of him in a while. Other time-nuts that have been at IFCS/EFTF are Ole Petter Ronningen and Javier Serano. Javier usually comes, when he has something to present and Ole if his wife permits it ;-) Attila Kinali -- Science is made up of so many things that appear obvious after they are explained. -- Pardot Kynes ___ 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] u-Blox ZED-F9T block diagram or timing knowledge available here?
Hello Tim, There’s a TDEV plot here: http://www.openttp.org/scripts/blog.php PPS measurements were post -processed using the sawtooth corrections. Cheers Michael On Tue, 7 Jan 2020 at 1:07 pm, Tim S wrote: > Hi, first time poster, just getting into the time rabbit-hole. > > I'm looking at building my own 10MHz double-oven + Rubidium standard > for home-lab use, and I wanted to investigate GPS disciplining. I read > some remarkable work using Jupiter engines and a simple N/1000 and PLL, but > with those receivers becoming much more outdated and higher precision GPS > receivers now fairly cheap - I thought I'd try something new from uBlox to > not repeat prior efforts. I've gone all through every resource I can find > online and on the uBlox forums, but there is a general lack of public > information about the time and clock features of the u-Blox F9 engine. > > Suffice it to say, there is a section in the integration manual where > they elude the 1PPS signal is set to the closest one of 1023 edges - which > seems to suggest a possible sawtooth phase noise creation. Talking with a > person "clive1" on the uBlox forum it sounds like the internal GPS engine > >>MAY<< now running at 384MHz there sounds like a possibility to align a > 1PPS edge to a much finer resolution clock which is closer tied to the GPS > solution and thus less digital divider phase noise might be possible. > > Does it sound like I'm way out in left field here? Anyone have the > luxury of more insight into the construction of the uBlox F9 GPS engine? I > don't mind spending a few grand on some factory new components to get a > decent 10MHz standard, but I'm less interested in doing so if I'm not going > to understand what's going on inside. > > Thanks in advance for responses, > > -Tim Strommen > ___ > 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] u-Blox ZED-F9T block diagram or timing knowledge available here?
On 1/6/20 6:25 PM, Bob kb8tq wrote: Hi If you go back in the list archives, there is a lot of info on doing this and that with the F9P and the F9T. For a while, there was speculation that the price on them would come down quite a bit. So far that does not seem to be happening. How to search archives effectively with Google.. "site:febo.com" Bottom line is that both the F9P and F9T have roughly a +/- 4 ns sawtooth range. The sawtooth error correction information out of the device will take this down a bit, but not quite as far as some of us hoped. Since both devices are dual band, you can easily post process the data against various services. I put out some plots suggesting a pretty good level of performance doing this. (sub nanosecond at short tau). I have not revisited the project since then. As far as either device tagging an input to better than 4 ns …not so much. Same thing with the PPS doing better than that. At the moment, the Furuno modules have the smallest sawtooth window that I know of. Bob On Jan 6, 2020, at 8:56 PM, Tim S wrote: Hi, first time poster, just getting into the time rabbit-hole. I'm looking at building my own 10MHz double-oven + Rubidium standard for home-lab use, and I wanted to investigate GPS disciplining. I read some remarkable work using Jupiter engines and a simple N/1000 and PLL, but with those receivers becoming much more outdated and higher precision GPS receivers now fairly cheap - I thought I'd try something new from uBlox to not repeat prior efforts. I've gone all through every resource I can find online and on the uBlox forums, but there is a general lack of public information about the time and clock features of the u-Blox F9 engine. Suffice it to say, there is a section in the integration manual where they elude the 1PPS signal is set to the closest one of 1023 edges - which seems to suggest a possible sawtooth phase noise creation. Talking with a person "clive1" on the uBlox forum it sounds like the internal GPS engine MAY<< now running at 384MHz there sounds like a possibility to align a 1PPS edge to a much finer resolution clock which is closer tied to the GPS solution and thus less digital divider phase noise might be possible. Does it sound like I'm way out in left field here? Anyone have the luxury of more insight into the construction of the uBlox F9 GPS engine? I don't mind spending a few grand on some factory new components to get a decent 10MHz standard, but I'm less interested in doing so if I'm not going to understand what's going on inside. Thanks in advance for responses, -Tim Strommen ___ 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] u-Blox ZED-F9T block diagram or timing knowledge available here?
Forrest Christian said: > One thing which it took me a while to wrap my head around is that for > frequency, sawtooth error generally dissappears for a lot of definitions of > reasonable accuracy. You're averaging for such a long period that what seems > like horrible accuracy is very usable. Check out hanging bridges. :) > For instance say your gps 1PPS source is accurate to +-1uS. Over 1 second > this is 1e-6. But over 1000 seconds this is 1e-9. Over 10 seconds > you're at 1e-11. For a 10MHz clock adjusted using this long of averaging, > this error is only +-.0001Hz That only works if the device you are controlling is stable over that time period. -- 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.
Re: [time-nuts] u-Blox ZED-F9T block diagram or timing knowledge available here?
For a few grand you can get an off the shelf fs740 or something similar, probably with a rubidium timebase. But I get the impression this is more of a learning experience. One thing which it took me a while to wrap my head around is that for frequency, sawtooth error generally dissappears for a lot of definitions of reasonable accuracy. You're averaging for such a long period that what seems like horrible accuracy is very usable. Hopefully some of the more experienced time nuts will correct the following if my math is faulty. For instance say your gps 1PPS source is accurate to +-1uS. Over 1 second this is 1e-6. But over 1000 seconds this is 1e-9. Over 10 seconds you're at 1e-11. For a 10MHz clock adjusted using this long of averaging, this error is only +-.0001Hz Of course this is somewhat simplified and the devil is in the implementation details. As I'm sure others will point out, if you're using certain receivers, then sawtooth correction data is available to you which will enable further correction, which makes the internal clock frequency which the 1PPS edges are aligned to less of interest as the receiver outputs both the 1PPS and data indicating how far the receiver believes the 1PPS edge is out of alignment with ideal. On Mon, Jan 6, 2020, 6:07 PM Tim S wrote: > Hi, first time poster, just getting into the time rabbit-hole. > > I'm looking at building my own 10MHz double-oven + Rubidium standard > for home-lab use, and I wanted to investigate GPS disciplining. I read > some remarkable work using Jupiter engines and a simple N/1000 and PLL, but > with those receivers becoming much more outdated and higher precision GPS > receivers now fairly cheap - I thought I'd try something new from uBlox to > not repeat prior efforts. I've gone all through every resource I can find > online and on the uBlox forums, but there is a general lack of public > information about the time and clock features of the u-Blox F9 engine. > > Suffice it to say, there is a section in the integration manual where > they elude the 1PPS signal is set to the closest one of 1023 edges - which > seems to suggest a possible sawtooth phase noise creation. Talking with a > person "clive1" on the uBlox forum it sounds like the internal GPS engine > >>MAY<< now running at 384MHz there sounds like a possibility to align a > 1PPS edge to a much finer resolution clock which is closer tied to the GPS > solution and thus less digital divider phase noise might be possible. > > Does it sound like I'm way out in left field here? Anyone have the > luxury of more insight into the construction of the uBlox F9 GPS engine? I > don't mind spending a few grand on some factory new components to get a > decent 10MHz standard, but I'm less interested in doing so if I'm not going > to understand what's going on inside. > > Thanks in advance for responses, > > -Tim Strommen > ___ > 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] u-Blox ZED-F9T block diagram or timing knowledge available here?
Hi If you go back in the list archives, there is a lot of info on doing this and that with the F9P and the F9T. For a while, there was speculation that the price on them would come down quite a bit. So far that does not seem to be happening. Bottom line is that both the F9P and F9T have roughly a +/- 4 ns sawtooth range. The sawtooth error correction information out of the device will take this down a bit, but not quite as far as some of us hoped. Since both devices are dual band, you can easily post process the data against various services. I put out some plots suggesting a pretty good level of performance doing this. (sub nanosecond at short tau). I have not revisited the project since then. As far as either device tagging an input to better than 4 ns …not so much. Same thing with the PPS doing better than that. At the moment, the Furuno modules have the smallest sawtooth window that I know of. Bob > On Jan 6, 2020, at 8:56 PM, Tim S wrote: > > Hi, first time poster, just getting into the time rabbit-hole. > >I'm looking at building my own 10MHz double-oven + Rubidium standard > for home-lab use, and I wanted to investigate GPS disciplining. I read > some remarkable work using Jupiter engines and a simple N/1000 and PLL, but > with those receivers becoming much more outdated and higher precision GPS > receivers now fairly cheap - I thought I'd try something new from uBlox to > not repeat prior efforts. I've gone all through every resource I can find > online and on the uBlox forums, but there is a general lack of public > information about the time and clock features of the u-Blox F9 engine. > >Suffice it to say, there is a section in the integration manual where > they elude the 1PPS signal is set to the closest one of 1023 edges - which > seems to suggest a possible sawtooth phase noise creation. Talking with a > person "clive1" on the uBlox forum it sounds like the internal GPS engine >>> MAY<< now running at 384MHz there sounds like a possibility to align a > 1PPS edge to a much finer resolution clock which is closer tied to the GPS > solution and thus less digital divider phase noise might be possible. > >Does it sound like I'm way out in left field here? Anyone have the > luxury of more insight into the construction of the uBlox F9 GPS engine? I > don't mind spending a few grand on some factory new components to get a > decent 10MHz standard, but I'm less interested in doing so if I'm not going > to understand what's going on inside. > > Thanks in advance for responses, > > -Tim Strommen > ___ > 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] u-Blox ZED-F9T block diagram or timing knowledge available here?
Hi, first time poster, just getting into the time rabbit-hole. I'm looking at building my own 10MHz double-oven + Rubidium standard for home-lab use, and I wanted to investigate GPS disciplining. I read some remarkable work using Jupiter engines and a simple N/1000 and PLL, but with those receivers becoming much more outdated and higher precision GPS receivers now fairly cheap - I thought I'd try something new from uBlox to not repeat prior efforts. I've gone all through every resource I can find online and on the uBlox forums, but there is a general lack of public information about the time and clock features of the u-Blox F9 engine. Suffice it to say, there is a section in the integration manual where they elude the 1PPS signal is set to the closest one of 1023 edges - which seems to suggest a possible sawtooth phase noise creation. Talking with a person "clive1" on the uBlox forum it sounds like the internal GPS engine >>MAY<< now running at 384MHz there sounds like a possibility to align a 1PPS edge to a much finer resolution clock which is closer tied to the GPS solution and thus less digital divider phase noise might be possible. Does it sound like I'm way out in left field here? Anyone have the luxury of more insight into the construction of the uBlox F9 GPS engine? I don't mind spending a few grand on some factory new components to get a decent 10MHz standard, but I'm less interested in doing so if I'm not going to understand what's going on inside. Thanks in advance for responses, -Tim Strommen ___ 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] signal transit time through WWV receiver
It turns out Adam Farson has posted the appropriate measurements at https://www.ab4oj.com/icom/ic7300/7300notes.pdf The radio in question is an ICOM IC-7300. For lower sideband, the latency of the radio is about 3.7 ms. By my calculation, the propagation delay (computed with the great circle distance and speed of light in a vacuum) is about 8.8 ms, so the total is about 12.5 ms. So my first conclusion is this is negligible for any manual use. If/when I develop any automated use I can decide what delays in the automation are negligible, and which aren't. ___ 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] signal transit time through WWV receiver
On 1/6/20 11:08 AM, GERRY ASHTON wrote: I am aware that WWV signals are intended to reflect the correct time at the instant the signal leaves WWV's antenna. It's up to me to allow for propagation through air and space to my antenna, and transit through my receiver. With newer direct-sampling receivers, the processing time in the receiver's computer circuitry may greater than we are accustomed to. Are there any simple tricks to measuring the transit time. My thought is to create a pulsed 10 MHz source, with AM modulation when the signal is on, and compare a path directly into one channel of an oscilloscope with the audio output of the receiver feeding into the other channel. Any easier or better suggestions? My test equipment is much more limited than many other members of this list. That's the sort of approach that works. A *lot* depends on the implementation of your SDR. If your processing chain is deterministic in delay (for instance, it's doing all the DSP in a FPGA in logic) then you can directly measure the number of clocks between RF signal coming in and demodulated signal coming out. That's what I did on a HF receiver for a satellite - we time stamp the ADC "start sampling" instant (when samples start to flow into the chain) with a counter that also snaps the count when we get a 1pps from GPS or onboard atomic reference. I triggered a arbitrary waveform generator with the 1pps - so I have a RF signal that begins at a known time, and a sampling epoch that begins at a known time, so I can line it up. If your SDR is done mostly in software in the CPU, then you have to worry about interrupts, etc. This was a huge problem for the early FlexRadio SDRs - people are used to operating CW with a delay (from propagation and analog electronics) but NOT used to having a variable delay, and the comments on the forums were copious and hostile. Over the years they fixed their buffering strategies, etc. Unfortunately, most software radio folks, especially people doing implementations for their thesis or dissertation, just care about moving the bits through a virtual wire, and don't care about absolute timing. As long as the bits in the recorded data are correct, they're happy. Most SDR software running on PCs (e.g. gnuradio) just doesn't care. There's no real attempt to try and have deterministic timing, just that you don't drop samples. People who need a constant delay implement some scheme of a FIFO buffer, run the front end ahead to make sure the FIFO has enough samples in it, and then start the playback from the FIFO using the media player API of the host OS to make sure that samples come out synchronously (the problem is identical to making sure that the audio and video tracks line up). ___ 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] 5065 photo/lamp problem
Hi Corby, On 2020-01-06 23:02, cdel...@juno.com wrote: > Magnus, > > If you apply a +20V supply to the lamp connector you should see 125-150ma > unlit and it drops bit when it lights. I see about 1,23 V over the 10 Ohm resistor, matching up with that current. > Also measure from the lamp connector center pin to the outside conductor > with an Ohmmeter. > > You should have around 3.33K. The 1.33K resistor (in series with a 2.0K) > is a common problem. it can open up or rise in value. > > I usually replace this resistor in units I service even if it measures > good. > > I use a 1.3K 2% MOX resistor. > > Also check the approx. 12 Ohm resistor on the standoffs to see if it > opened up. Both these resistors where good, but fractured. I already replaced the 10 Ohm resistor (put a pair of 22 Ohm resistors in parallel so they can handle the power better) and is about to replace the 1.33k resistor. Nothing else looked terrible bad and as far as I was able to quick-measure the resistor did not seem broken, but I consider replacing that regardless, but I will check it again. > > If you pull the lamp assy. you can place a spec-A lead and see the RF. > Should be approx 88Mhz. (not critical) Before opening up the assembly I sniffed the J16 connector for something in that neighborhood, but no. I forgot to sniff again with the hood off. However, I let it sit there for some time without any actual light from the lamp. I did see light coming in from the side and thought that this was the lamp, but no. > Once power is applied the lamp should start (cold) within a minute or > so, warm it starts fast. > > If you place a scope on A7 TP2 and with the lamp assy removed allow some > florescent lighting to fall into the interior you should see a large 50 > or 60Hz signal from the light falling on the photocell. I was considering doing exactly that, but I concluded that the lamp does not lit so I thought I would want to start with that anyway. Thank you for your input so far. It seems like I'm not completely off the mark even if I have yet to find the real fault of that rubidium lamp. I borrowed the A15 board over to the other broken 5065 in order to support another measurement campaign, and while that second 5065 is noisier that the 5065 that is operational (on its own) it was quieter than the OSA 3210 and 5071A cesiums. The aim is to repair both 5065s that is broken so I have three operational. Once they are all working, I will do a trim campaign on them. I was amazed at how much noisier (factor of 3-4 times) the older unit was compared to the newer. Phase-noise of the synthesizers is not stellar by any means, my 3325B is cleaner by far, and I only used a spectrum analyzer to compare them while the TimePod was busy doing other things. Right now the main goal is to get as much as possible online to see just what set of devices is able to make the TimePod eat into the noise and characterize the EFOS10... because it's a fun challenge and a chance to characterize things. It is also good to have those curves as reference as one measure things. Currently my best 5065A and a BVA is given a shot, but since the BVAs was brought online the other day, it is clearly drift-limited. I have 5 large rubidiums, it would be nice to have them all operational and see how they behave. Then I have cesiums to test... and OCXOs, and GPSDOs... yes, lab-time is fun again. Talking about GPSDOs, I have two home-brew GPSDOs that I've been firing up, one is build by late Lars Wallenius, and another by AE6RV GFS-6A GPSDO. The Trimble Thunderbolt seems happy right now, but my Trimble NetRS is not seeing any satellites. Cheers, Magnus ___ 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] 5065 photo/lamp problem
Magnus, If you apply a +20V supply to the lamp connector you should see 125-150ma unlit and it drops bit when it lights. Also measure from the lamp connector center pin to the outside conductor with an Ohmmeter. You should have around 3.33K. The 1.33K resistor (in series with a 2.0K) is a common problem. it can open up or rise in value. I usually replace this resistor in units I service even if it measures good. I use a 1.3K 2% MOX resistor. Also check the approx. 12 Ohm resistor on the standoffs to see if it opened up. If you pull the lamp assy. you can place a spec-A lead and see the RF. Should be approx 88Mhz. (not critical) Once power is applied the lamp should start (cold) within a minute or so, warm it starts fast. If you place a scope on A7 TP2 and with the lamp assy removed allow some florescent lighting to fall into the interior you should see a large 50 or 60Hz signal from the light falling on the photocell. That is a quick check of the A7! Cheers, Corby 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] signal transit time through WWV receiver
I can tell you, that with say a 10kHz bandwidth AM receive filter on an analog receiver, the transit time through that filter will be ballpark 100 microseconds. Possibly more if it's a high-order filter. I have used DSP-based (non-PC) SDR's for WWV reception and characterized them as you suggest. I found that for a 6kHz SDR receive filter, 200 microseconds was the delay between RF in and audio out. I suspect a PC-based SDR will be more delay than the pure-DSP solution. For comparison, the propagation distance from Colorado to my home in Maryland is about 1560 miles. That right there is a 8.3 millisecond delay. The few hundred microseconds delay in the SDR was negligible compared to the 8.3 millisecond delay. Dave Mills, the developer of NTP, tells me that he could see the night vs day ionospheric path difference (circa 30 miles out of 1560?) by doing extended analysis on the data. I looked for that in my data, and it might have been there, but was kinda in the noise. Tim N3QE On Mon, Jan 6, 2020 at 3:24 PM GERRY ASHTON wrote: > I am aware that WWV signals are intended to reflect the correct time at > the instant the signal leaves WWV's antenna. It's up to me to allow for > propagation through air and space to my antenna, and transit through my > receiver. With newer direct-sampling receivers, the processing time in the > receiver's computer circuitry may greater than we are accustomed to. > > Are there any simple tricks to measuring the transit time. My thought is > to create a pulsed 10 MHz source, with AM modulation when the signal is on, > and compare a path directly into one channel of an oscilloscope with the > audio output of the receiver feeding into the other channel. Any easier or > better suggestions? My test equipment is much more limited than many other > members of this list. > > ___ > 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] signal transit time through WWV receiver
Hi, On 2020-01-06 22:11, Hal Murray wrote: > ashto...@comcast.net said: >> Are there any simple tricks to measuring the transit time. My thought is to >> create a pulsed 10 MHz source, with AM modulation when the signal is on, and >> compare a path directly into one channel of an oscilloscope with the audio >> output of the receiver feeding into the other channel. Any easier or better >> suggestions? My test equipment is much more limited than many other members >> of this list. > You will need a filter to detect the AM modulation. That filter will have a > delay. > > Is there any difference in delay between an analog filter and a digital > filter? > > How do the wizards that use common view GPS time transfer calibrate the delay > through their filters? > It is common to calibrate and compensate for at least the input of the receiver, so whatever offsets the receiver introduces is removed in presented time. There will be a residue offset which is often measured and compensated for by other means. Then, antenna and antenna cable similarly needs compensation. For GPS, the phase center of the antenna becomes compensated by the positioning, but this isn't perfect that that is ironed out in post-processing typically. Quality of antenna, receiver and installation is know to affect things, especially due to multi-path. For WWV type of receivers, there is no in-system compensation of propagation delay, so that will have to be done using other means, such as GPS or as in the old days, phase is transported by means of a stable atomic clock. Once arrived home, the delay is jotted down and wheeled into the delay compensation of the clock. Regardless, with GPS most of this comes with decent enough compensation as it is and if you care about phase to the ns you calibrate everything and then calibrate again. Oh, phase-stable cables becomes an issue then. Cheers, Magnus ___ 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] signal transit time through WWV receiver
ashto...@comcast.net said: > Are there any simple tricks to measuring the transit time. My thought is to > create a pulsed 10 MHz source, with AM modulation when the signal is on, and > compare a path directly into one channel of an oscilloscope with the audio > output of the receiver feeding into the other channel. Any easier or better > suggestions? My test equipment is much more limited than many other members > of this list. You will need a filter to detect the AM modulation. That filter will have a delay. Is there any difference in delay between an analog filter and a digital filter? How do the wizards that use common view GPS time transfer calibrate the delay through their filters? -- 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] signal transit time through WWV receiver
I am aware that WWV signals are intended to reflect the correct time at the instant the signal leaves WWV's antenna. It's up to me to allow for propagation through air and space to my antenna, and transit through my receiver. With newer direct-sampling receivers, the processing time in the receiver's computer circuitry may greater than we are accustomed to. Are there any simple tricks to measuring the transit time. My thought is to create a pulsed 10 MHz source, with AM modulation when the signal is on, and compare a path directly into one channel of an oscilloscope with the audio output of the receiver feeding into the other channel. Any easier or better suggestions? My test equipment is much more limited than many other members of this list. ___ 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.
