Re: [time-nuts] HP 58503A
Peter Bell bell.peter@... writes: If it is, then you should see a pulse every 2 seconds, lined up with the even seconds in GPS time. This might seem a rather strange signal to provide, but it's what the IS-95 derived CDMA systems use to trigger the start of another 100 block signalling frame. It also tends to suggest that the unit you have was originally being used as part of a CDMA system. Regards, Pete Hi Pete, I snapped on the osci probe and see no 1 PPS or 2 PPS signal. It seems like a noise signal with several positive and negative spikes with an peak to peak value of 50 to 60 mV... disapointing... Next is to analyze the rest with a logicprobe but the signal level seems to be too small for beeing a logic signal... TTL should be at 15 V, CMOS 5 V... but 50 mV ? Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
I ran into a wiki description of GPS using WGS84 a couple days ago. It included a mention of ESEC and it was something like: Earth Static, Earth Centric. I think I was following a link about the Z3801A. It referred to the fact that lat-lon is referenced to a static grid on the Earth and doesn't change as the Earth rotates on its axis or around the sun. Earth static and Earth centric. 73, Doug Reed, N0NAS. Christoph Kopetzky wrote: But now I am cleaning my devices and I am reading the label ESEC again on the back. So the question comes up again, what is ESEC? Google knows nothing about the signal or protocol... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
On 8/2/12 6:24 PM, Doug Reed wrote: I ran into a wiki description of GPS using WGS84 a couple days ago. It included a mention of ESEC and it was something like: Earth Static, Earth Centric. I think I was following a link about the Z3801A. It referred to the fact that lat-lon is referenced to a static grid on the Earth and doesn't change as the Earth rotates on its axis or around the sun. Earth static and Earth centric. Earth Centered Inertial - ECI centered on the earth, doesn't rotate with earth - very popular with earth orbiting satellites, because their center of rotation is at the center of the earth but their orbital plane is fixed in celestial terms. like RA/Decl Earth Centered Earth Fixed - ECEF (or ECF) centered on earth, rotates with earth. More like conventional lat/lon. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Doug, I ran into a wiki description of GPS using WGS84 a couple days ago. It included a mention of ESEC and it was something like: Earth Static, Earth Centric. I think I was following a link about the Z3801A. It referred to the fact that lat-lon is referenced to a static grid on the Earth and doesn't change as the Earth rotates on its axis or around the sun. Earth static and Earth centric. That reference frame is called Earth Centered Earth Fixed (ECEF). And that is what GPS is using internally. However it is not lat/lon/h, but cartesian with origo in the earth center, xy in the equatorial plane and z pointing towards the north pole. http://en.wikipedia.org/wiki/ECEF -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
What 'scope are you using (brand and model)? TLL is 5V, CMOS 4000 series can be 15V but runs starting at 3V. Set the scope vertical (channel 1) at 1V/div (probe at 10:1), use NORMAL for the trigger and set the trigger (for the channel 1) *slowly* from 0V to +200mV (assuming that the trigger isn't aware of the 10:1) trying to follow the trigger indicator or the trace appearing on the screen. On Fri, Aug 3, 2012 at 3:31 PM, b...@lysator.liu.se wrote: Doug, I ran into a wiki description of GPS using WGS84 a couple days ago. It included a mention of ESEC and it was something like: Earth Static, Earth Centric. I think I was following a link about the Z3801A. It referred to the fact that lat-lon is referenced to a static grid on the Earth and doesn't change as the Earth rotates on its axis or around the sun. Earth static and Earth centric. That reference frame is called Earth Centered Earth Fixed (ECEF). And that is what GPS is using internally. However it is not lat/lon/h, but cartesian with origo in the earth center, xy in the equatorial plane and z pointing towards the north pole. http://en.wikipedia.org/wiki/ECEF -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Azelio Boriani azelio.boriani@... writes: What 'scope are you using (brand and model)? TLL is 5V, CMOS 4000 series can be 15V but runs starting at 3V. Set the scope vertical (channel 1) at 1V/div (probe at 10:1), use NORMAL for the trigger and set the trigger (for the channel 1) *slowly* from 0V to +200mV (assuming that the trigger isn't aware of the 10:1) trying to follow the trigger indicator or the trace appearing on the screen. On Fri, Aug 3, 2012 at 3:31 PM, bg@... wrote: Azelio, I tried my two HAMEG Scopes for this job, a digital variant HMO3524 and my analog HM2005-2 scope... I am quite familiar with scope measurements :-) so there are definitely no PPS signals on the output... Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Hal Murray hmurray@... writes: We discussed this area a week or three ago. You don't need a digital scope to determine if there is a pulse. A digital scope may help to see the pulse and figure out what it looks like. With an analog scope, you can either look at the blinking light that tells you it's triggering, or you can reduce the sweep speed until you can easily see the (flat) line from the beam each time it triggers. I can see a 10 microsecond pulse with my old Tek 465. It blinks and I roughly remember what the picture looks like. If I want to know a detail, I have to look at the right spot and wait for the next pulse. Hi Hal, with my analog scope (Hameg HM2005-2) I can trigger a low level voltage spike signal with a p-p voltage of 30 mV and a frequency of 52,6 kHz. Could that be real? The signal level is very low, 30 mV... Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Doug Reed n0nas@... writes: I ran into a wiki description of GPS using WGS84 a couple days ago. It included a mention of ESEC and it was something like: Earth Static, Earth Centric. I think I was following a link about the Z3801A. It referred to the fact that lat-lon is referenced to a static grid on the Earth and doesn't change as the Earth rotates on its axis or around the sun. Earth static and Earth centric. 73, Doug Reed, N0NAS. Hi Doug, do you have more infos about the signal type of that Earth static, Earth centric? is it a digital or analog signal? Thanks Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Here: www.leap*second*.com/museum/*hp58503*a/097-58503-12-iss-1.pdf you can find that there is the option 002 for the even second but they call it PP2S... Try to discover if your 58503 has this option 002. On Fri, Aug 3, 2012 at 5:09 PM, Christoph Kopetzky dekag...@gmail.comwrote: Hal Murray hmurray@... writes: We discussed this area a week or three ago. You don't need a digital scope to determine if there is a pulse. A digital scope may help to see the pulse and figure out what it looks like. With an analog scope, you can either look at the blinking light that tells you it's triggering, or you can reduce the sweep speed until you can easily see the (flat) line from the beam each time it triggers. I can see a 10 microsecond pulse with my old Tek 465. It blinks and I roughly remember what the picture looks like. If I want to know a detail, I have to look at the right spot and wait for the next pulse. Hi Hal, with my analog scope (Hameg HM2005-2) I can trigger a low level voltage spike signal with a p-p voltage of 30 mV and a frequency of 52,6 kHz. Could that be real? The signal level is very low, 30 mV... Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
OK, that's what I get for working from memory. :-) I got the idea more or less right but it has nothing to do with the abbreviation under discussion Thanks for the correction. 73, Doug. b...@lysator.liu.se wrote: Doug, I ran into a wiki description of GPS using WGS84 a couple days ago. It included a mention of ESEC and it was something like: Earth Static, Earth Centric. I think I was following a link about the Z3801A. It referred to the fact that lat-lon is referenced to a static grid on the Earth and doesn't change as the Earth rotates on its axis or around the sun. Earth static and Earth centric. That reference frame is called Earth Centered Earth Fixed (ECEF). And that is what GPS is using internally. However it is not lat/lon/h, but cartesian with origo in the earth center, xy in the equatorial plane and z pointing towards the north pole. http://en.wikipedia.org/wiki/ECEF -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Azelio Boriani azelio.boriani@... writes: Here: www.leap*second*.com/museum/*hp58503*a/097-58503-12-iss-1.pdf you can find that there is the option 002 for the even second but they call it PP2S... Try to discover if your 58503 has this option 002. Azelio, thanks for the link but I already know this manual. And for remembering I was talking about my 58503A Receiver. This receiver do not have a PP2S Output. Only the TTL Alarm and the ESEC (?) And as I wrote in my posting above, I only can see with my analog scope a little periodic signal with a level of approximately 28-30 mV and a triggered frequency of 56,3 kHz at a timebase setting of 5µs/div. If I am changing my timebase to 10µs/div and measuring the frequency I am getting 65,4 kHz. This is a little bit confusing and seems to be reasoned from the little signal level... So now I am more curious what signal the ESEC seems to be ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Hello followers, I can state that my measuring of the signal (30 mV, 65,2 kHz) was caused by the serial line of the com port of the receiver... :-) After looking for sources of the noisy signal I disconnected my first the GPS antenna signal from the 58512A GPS amplifier. - Signal intact Then I disconnect my frequency meter from the 10 MHz output - signal intact Now I disconnected the serial connection to my notebook - signal gone! So it was an interspersed signal from the serial connector ... But at the end the question what the ESEC output may be is still mysterious... Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Crosscorrelation phase noise measurements
On 08/03/2012 04:20 AM, John Miles wrote: Cross correlation is one of life's few free lunches, but you do have to wait for it to work. Magnus is correct in that you can get a 3 dB advantage in noise reduction per sweep, but that only applies to the first sweep. Agreed. Did not mean to say anything else. The actual improvement in the instrument noise is related to the square root of the number of averages taken. This means that a cross-correlating phase noise analyzer is very effective for broadband noise, where minimal decimation has to be done prior to the FFT. The input buffers fill up very rapidly in that case, and you can get hundreds of thousands of averages in just a few minutes. But measurement of low levels of 1/f^n noise close to the carrier can take a lot longer. I have mostly done 1 hour measure runs, so the gain is limited. One can view the gain for the various sections, which helps to illustrate the above statement. As an example, one customer just sent me a plot of the residual noise of a high-quality distribution amplifier. The indicated PN was below -160 dBc/Hz at 10 Hz, but the instrument floor at 10 Hz was still -165 dBc/Hz after a 50-hour run! Over that time, the 10 kHz-100 kHz FFT segment had undergone almost 30 million averages, improving the instrument floor in that region by over 35 dB. But the segment containing 10 Hz had been averaged only 17000 times for a 21 dB improvement. Interesting. When more data has been received, the more interesting it would be to spend processing time on the closed in noise rather than getting more data on far out noise, as they come quickly. Pondering if some overlapping strategy could be be used with succsess, similar to what we do to ADEV and friends in the overlapping, total and theo strategies to improve long tau measurement quality. As far as concrete examples go, in addition to Magnus's suggestion of the NIST documents, I'd recommend this one: http://www.congrex.nl/EFTF_Proceedings/Papers/Session_14_Oscillators_and_Noi se/14_04_Bale.pdf Here, the authors use a pair of 1980s-vintage HP 3048A phase noise measurement systems with a newer signal analyzer that performs cross-correlation. They are measuring additive noise from two-port devices, rather than oscillator noise, but the same principles apply to both. http://cp.literature.agilent.com/litweb/pdf/5989-1617EN.pdf The modern E5052A/B signal analyzers do the same thing in one box, basically. http://arxiv.org/pdf/1003.0113v1.pdf A good introductory article by Enrico Rubiola, with more specific math than the other two links. Enrico has been using cross-correlation and averaging for quite a while, in combination with interferometric setups. Do read the article! For the buffer-amplifier, they would make good use of an interferometric front-end to the TimePod in order to reach deeper into the noise. I haven't built one yet. Something to do in the fall. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FTS1200, OSA8600, OSA8601 phase noise and ADEV measures
Hi John, On 08/03/2012 05:18 AM, John Miles wrote: The benefit is that I can de-correlate the reference oscillator noise, and measure near or even below it. I have just started doing this, so this is really my first sloppy measurements for you to see where I am heading. I expect John to chime in and comments on all my mistakes. Nope, you've pretty much got it. :) Great! :) The idea is to fool TimeLab into thinking that the signal at the TimePod Ch0 and Ch2 inputs is the 'reference,' and the signal at the hardwired Ch1 and Ch3 splitter is the 'input.' That is the reasoning behind swapping the channels in the subtraction expression. I forgot to mention that, as I knew it was the point about that move. You then connect two uncorrelated oscillators of similar frequency to the Ch0 and Ch2 SMA input jacks. The noise contribution from each oscillator is removed by the same cross correlation process that gets rid of the ADC noise. Indeed. Technically it's not necessary for the two oscillators to be at exactly the same frequency, and it's also OK if they phase-wrap during the measurement. OK. Good to know. In theory they could be as much as a couple kHz apart, but certain calculations that the TimePod driver makes to cancel internal clock drift may be confused if they are more than a couple of Hz apart. I also have not looked carefully for instrument spurs and artifacts that might show up in that case, so I usually tell people to tune the two references as closely together as possible. OK. Good to know. It would help if the frequency between the reference oscillators could be monitored one way or another. They do need to have the same amplitude, within a dB or two, for the same reason (to avoid triggering some error-detection code.) Good to know. Need to look at that then. What is critical is that there is no crosstalk between the two oscillators. If so, it will show up as a beatnote. All of the warnings in the manual about using double-shielded cables at the input and reference ports apply to the use of uncorrelated references as well. I have good cables, but can improve separation, as several of the OCXOs hang of the same +24V source and is physically close to each other. In the case of your FTS measurement, there's a very clear beatnote or other artifact at about 3 Hz. You can see this in the frequency difference view by zooming in (see attached), in the ADEV plot at t=0.33s, and in the phase noise plot as the dominant spur, reported at 2.9 Hz. There is also a spur at half that frequency. The AM plot says that the 1.4 Hz spur and 2.9 Hz spurs are about equal in magnitude, while the phase noise plot says that the 2.9 Hz spur is about 20 dB stronger. (That's why it dominates the ADEV and frequency-difference views.) The FTS1200 is about 1.5 Hz below the reference, so maybe that reflects around the reference? I will fiddle with that in a moment. So you should look for any possible differences in frequency between either your two reference sources *or* between the reference source(s) and the FTS 1200. In the presence of crosstalk between RF cables or power supplies, either of these scenarios could happen. Cross-talk on the power-supply is highly suspected in this case. I'll toss in a spare power-supply for separation. Given perfect isolation between your DUT and reference, you should not see any PN spurs or ADEV artifacts at their difference frequency. If you do, they should be so faint as to be barely noticeable. (I can say that fairly confidently because I spent a lot of time chasing beatnote problems during the RD process. However, I have *not* spent much time looking at what happens when you use 2 reference oscillators that are not very close to the same frequency, so I can't guarantee what might happen then, spur-wise.) I'll have a look at how they are tuned and see if I can improve on the situation. Meanwhile the oscillators remains heated. :) Bottom line, the large low-frequency spurs in the FTS plot at 1.4 and 2.9 Hz will be caused by one of these conditions: 1) A problem with the reference source(s) 2) A problem with the FTS oscillator itself 3) A normal characteristic of the FTS oscillator (maybe its spur specs weren't very good to begin with?) It's interesting to note that these spurs is unique to the FTS1200 measurement. Maybe it need some service. Schematic anyone? 4) An RF crosstalk or leakage problem with the cables/adapters used 5) A power-supply regulation issue Would not explain why only the FTS1200 experience this, while it shares supply with other oscillator not having this property. 6) Coupling between inadequately-bypassed power leads. This is a big problem with some OCXOs where they apparently forgot to use bypass capacitors inside the can. I usually solder a 0.1 uF ceramic chip cap right at the point of entry, if in doubt. Doable. 7) Some as-yet-unexplored effect related to beatnotes in dual-reference
Re: [time-nuts] HP 58503A
dekag...@gmail.com said: with my analog scope (Hameg HM2005-2) I can trigger a low level voltage spike signal with a p-p voltage of 30 mV and a frequency of 52,6 kHz. Could that be real? The signal level is very low, 30 mV... That sounds like junk pickup. My guess would be from a switching power supply. Any real signal that I've seen is at least several volts. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 58503A
Hal Murray hmurray@... writes: dekagoon@... said: with my analog scope (Hameg HM2005-2) I can trigger a low level voltage spike signal with a p-p voltage of 30 mV and a frequency of 52,6 kHz. Could that be real? The signal level is very low, 30 mV... That sounds like junk pickup. My guess would be from a switching power supply. Any real signal that I've seen is at least several volts. Hal, you are very right, in the meantime I found that the junk came over the serial connection from my notebook to the 58503A... Regards Chris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
