Re: [time-nuts] New TIC test run
Do you have the schematic for this online somewhere? what is the range of the interpolator? which TIC is the red/blue points? the blue data looks like it is aliased somehow, perhaps a number that is truncated/rounded badly? On Sat, Mar 8, 2014 at 9:46 PM, Bob Stewart b...@evoria.net wrote: I put my TIC to hardware, and have started testing it. Here is a sample run comparing it against the 5334B with an off frequency OCXO. I've scaled and rotated to tried to cancel out the length of the cables to the 5334B. Still early days with it, yet. http://www.evoria.net/AE6RV/TIC/TICvs5334B.png Bob - AE6RV ___ 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] New TIC test run
Hi Anders, I just put the schematic up at http://www.evoria.net/AE6RV/TIC/TIC2.bmp However, there are some caveats: I did not have to use the level shifter Q1/Q2. I am not yet using VR1. (Actually the one I bought failed for some reason.) R4 is actually 2.4K, and C1 is not being used. The capacitors in the 18F2220 PIC are sufficient without C1. I'm not sure what you mean by what is the range. The ADC is 10 bits wide. The output varies from about 150 to about 500 units over 360 degrees of phase error without the Voltage Ref. It should be twice that when I get that in and working; though I am worried that it might clip on the high side so... The red data, as it says on the plot, is the 53345B. The blue data is from the TIC. The transfer function is nonlinear, and I have made no effort to correct for this. I've had a day to play with it, and I'm amazed at the precision of this thing. It's like taking the 5334B and adjusting the focus knob. Of course it's not as accurate, due to the way it works, but it will fit my needs well in my GPSDO. Bob - AE6RV From: Anders Wallin anders.e.e.wal...@gmail.com To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, March 9, 2014 3:19 AM Subject: Re: [time-nuts] New TIC test run Do you have the schematic for this online somewhere? what is the range of the interpolator? which TIC is the red/blue points? the blue data looks like it is aliased somehow, perhaps a number that is truncated/rounded badly? On Sat, Mar 8, 2014 at 9:46 PM, Bob Stewart b...@evoria.net wrote: I put my TIC to hardware, and have started testing it. Here is a sample run comparing it against the 5334B with an off frequency OCXO. I've scaled and rotated to tried to cancel out the length of the cables to the 5334B. Still early days with it, yet. http://www.evoria.net/AE6RV/TIC/TICvs5334B.png Bob - AE6RV ___ 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] New TIC test run
The link seems garbled for some reason with it inline so let me try again. http://www.evoria.net/AE6RV/TIC/TIC2.bmp From: Bob Stewart b...@evoria.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, March 9, 2014 10:40 AM Subject: Re: [time-nuts] New TIC test run Hi Anders, I just put the schematic up at http://www.evoria.net/AE6RV/TIC/TIC2.bmp However, there are some caveats: I did not have to use the level shifter Q1/Q2. I am not yet using VR1. (Actually the one I bought failed for some reason.) R4 is actually 2.4K, and C1 is not being used. The capacitors in the 18F2220 PIC are sufficient without C1. I'm not sure what you mean by what is the range. The ADC is 10 bits wide. The output varies from about 150 to about 500 units over 360 degrees of phase error without the Voltage Ref. It should be twice that when I get that in and working; though I am worried that it might clip on the high side so... The red data, as it says on the plot, is the 53345B. The blue data is from the TIC. The transfer function is nonlinear, and I have made no effort to correct for this. I've had a day to play with it, and I'm amazed at the precision of this thing. It's like taking the 5334B and adjusting the focus knob. Of course it's not as accurate, due to the way it works, but it will fit my needs well in my GPSDO. Bob - AE6RV From: Anders Wallin anders.e.e.wal...@gmail.com To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, March 9, 2014 3:19 AM Subject: Re: [time-nuts] New TIC test run Do you have the schematic for this online somewhere? what is the range of the interpolator? which TIC is the red/blue points? the blue data looks like it is aliased somehow, perhaps a number that is truncated/rounded badly? On Sat, Mar 8, 2014 at 9:46 PM, Bob Stewart b...@evoria.net wrote: I put my TIC to hardware, and have started testing it. Here is a sample run comparing it against the 5334B with an off frequency OCXO. I've scaled and rotated to tried to cancel out the length of the cables to the 5334B. Still early days with it, yet. http://www.evoria.net/AE6RV/TIC/TICvs5334B.png Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] SR620 binary dump
Hi Tom, On 08/03/14 22:12, Tom Van Baak wrote: You make me curious. Any specific issue you're having? I haven't tried doing any programming to the SR620 yet, but I have some plans to do it. Cheers, Magnus Hi Magnus, Thanks for asking. Here's an update. I was curious why time interval or period measurements give slightly different results than frequency measurements on a SR620. Maybe the 5370 too. We often advise people to use time interval mode and not frequency mode. Volker's posting got me to dig further. His frequency-data ADEV plots looked too different from his phase-data ADEV plots. It's not just that frequency introduces dead time, but frequency also gives less precise results. But why is this. Ignoring other sources of noise, the 620 interpolator has 2.7 ps numerical granularity (1 / 90 MHz / 4096). It seemed to me that regardless of time interval, period, or frequency mode selection, the identical quantization and noise levels should be evident regardless how one measures an external source(s). Almost. The frequency measurement gate (page 86-87) creates a different insertion delay than any of the TI modes, and therefore requires a separate insertion delay calibration, as found in cal byte 50 (page 75 and 78). According to the manual no manual calibration is needed, but I assume that autocal handles it. Typical time-errors will scale with time-base, which is a great way to discover it's presence. It is actually fairly common that counters have separate signal path for TI and frequency modes, and hence different needs in this regard. However, you are getting at the conversions, and that can indeed be a factor too. I've seen this before with one counter. So there are two tempting commands to explore. One is BDMP (binary dump) which avoids ascii conversion and gives raw 64-bit binary values. Some people use it to dramatically increase measurement speed over GPIB. The other is EXPD (x1000 expanded resolution). My plan was to use two different exceptionally pure but drifting 10 MHz sources and see to what extent the 620 could measure/compare them. For this systematic effect you might start with just measuring the time-base at various times and with various methods and see where it gets you. Make sure to read out byte 50 and see if it makes sense for compensation. Also see what Autocal does to it and the result. The bad news is that EXPD is not allowed with frequencies above 5 digits (= 1 MHz) so it doesn't apply to 10 MHz inputs. That experiment waits while I make a clean 1 MHz source (e.g., 10 MHz/12 = 833. kHz). The built-in 1 kHz source is a good start. TADD-2 100 kHz next. In a true time-stamping counter one continuously counts events and continuously counts time. The 620 isn't continuous but it does have two registers, which the manual refers to as the event or cycle counter and the time interval counter. This is typical of the reciprocal counter principle. You clear the counters for the next measurement interval. Zero Dead-time counters like the 5371/5372 has continuous running counters and on a event they are sampled and stored while the counters keeps ticking away. Better yet, page 97 also refers to them as the top and bottom counter. Hint, hint. Your page numbering does not match my hardcopy of the manual. The binary dump data matches my expectations for period and interval. But for frequency, the 620 does not return the binary values of either the top or bottom counters. Instead it does a fixed point division and returns a scaled top/bottom binary quotient. It gives you the frequency in binary format. It's not the raw format of the HP537x counters. The net effect is that the ideal BDMP value for a 1 second 10 MHz measurements would be 0x001C71C71C71C71C. (note 0x1C7 / 4095 = 455 / 4095 = 10 / 90, as in 90 MHz). But you never actually get this hex value with a 10 MHz input. With a couple hundred 1-second measurements I saw only one of three values each time: 0x1c71c71c721bf3 = 8006399337569267 = 1000.27126 Hz 0x1c71c71c7270c9 = 8006399337590985 = 1000.54251 Hz 0x1c71c71c72c5a0 = 8006399337612704 = 1000.81379 Hz The delta among these values is 21718 or 21719 counts. So the lower ~16-bits isn't really noise, it's just deterministic quantized residuals from the long-division. And that explains why when the scaled binary values are converted to decimal Hz you get the odd-looking values above. The granularity, or resolution is 27 uHz / 10 MHz = 2.7e-12 = 2.7 ps. Nice, yes? To be expected. The bias is there. Of hundreds of samples, they were all +1 +2 and +3 times 2.7 ps above nominal. A +0 would give 1000.0 Hz. These BDMP readings have (much) greater resolution that what you get with plain strt;*wai;xall? values. What one normally sees over RS232 or GPIB are ascii readings like: 1.000E7 1.002E7 1.001E7 1.001E7
Re: [time-nuts] ADEV from phase or frequency measurement
On 04/03/14 01:05, Volker Esper wrote: Am 03.03.2014 23:04, schrieb Magnus Danielson: Volker, On 03/03/14 00:50, Volker Esper wrote: Sorry for the time delay... TIC: SR620 with Z3805 as external reference; signal source Nortel/Trimble GPSTM (GPSDO) 10MHz output Enclosed two plots (SW: Plotter): - one is sigma(tau) calculated from phase samples (SR620 TIME mode), - the other one is sigma(tau) from frequency data (SR620 FREQ mode) Whole equipment had a power up time of several days/weeks. Room temperature was stable over both measurements (within about 2 degrees C). The SR620 uses a bit different path through the logic when doing TI and FREQ measurements. The frequency measurement has a feature that means that the time error between start and stop signal needs to be calibrated out. This can be done using the calibration routines given in the manual. This should not affect the ADEV measure, but as a precaution. Try doing a pair of noise-floor measurements. That is, feed the reference 10 MHz to the A input for the frequency noise measurement. Then, for the TI noise-floor measurement, put a T on the A input, put it in high-Z mode and then use a 1 m cable to put the signal onto the B input which is terminating. You indeed have a higher level. Your initial shape makes me wonder. I would really like to get the TimeLab measurement files and eye-ball them closer. If you plot the phase or frequency, it may be easier to spot systematic wobbles. TDEV would also help, as it provides a general *tau scaling to the ADEV plot. 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. I already did these measurements, I stick the plots at this posting. - The plot with the long file name shows frequency mode measurement: 10MHz external reference put into channel A. - ...Plot2 shows a phase measurement, where I fed the reference signal via a home made 50 ohms splitter into both input channels. (I prefer feeding the channels symmetrically) Both plots show linear negative gradients, but the phase plot is steeper. The frequency plot transitions into a horizontal at about 1000s. The 1/sqrt(tau) curve is higher than the background noise of the counter. That flicker phase noise is more typical of a buffer or source than of the counter. For shorter taus I would expect the white noise to dominate. I'm just surprised about the level of flicker phase noise. What is the source? 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] ADEV from phase or frequency measurement
Am 09.03.2014 19:46, schrieb Magnus Danielson: On 04/03/14 01:05, Volker Esper wrote: Am 03.03.2014 23:04, schrieb Magnus Danielson: Volker, On 03/03/14 00:50, Volker Esper wrote: Sorry for the time delay... TIC: SR620 with Z3805 as external reference; signal source Nortel/Trimble GPSTM (GPSDO) 10MHz output Enclosed two plots (SW: Plotter): - one is sigma(tau) calculated from phase samples (SR620 TIME mode), - the other one is sigma(tau) from frequency data (SR620 FREQ mode) Whole equipment had a power up time of several days/weeks. Room temperature was stable over both measurements (within about 2 degrees C). The SR620 uses a bit different path through the logic when doing TI and FREQ measurements. The frequency measurement has a feature that means that the time error between start and stop signal needs to be calibrated out. This can be done using the calibration routines given in the manual. This should not affect the ADEV measure, but as a precaution. Try doing a pair of noise-floor measurements. That is, feed the reference 10 MHz to the A input for the frequency noise measurement. Then, for the TI noise-floor measurement, put a T on the A input, put it in high-Z mode and then use a 1 m cable to put the signal onto the B input which is terminating. You indeed have a higher level. Your initial shape makes me wonder. I would really like to get the TimeLab measurement files and eye-ball them closer. If you plot the phase or frequency, it may be easier to spot systematic wobbles. TDEV would also help, as it provides a general *tau scaling to the ADEV plot. 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. I already did these measurements, I stick the plots at this posting. - The plot with the long file name shows frequency mode measurement: 10MHz external reference put into channel A. - ...Plot2 shows a phase measurement, where I fed the reference signal via a home made 50 ohms splitter into both input channels. (I prefer feeding the channels symmetrically) Both plots show linear negative gradients, but the phase plot is steeper. The frequency plot transitions into a horizontal at about 1000s. The 1/sqrt(tau) curve is higher than the background noise of the counter. That flicker phase noise is more typical of a buffer or source than of the counter. For shorter taus I would expect the white noise to dominate. I'm just surprised about the level of flicker phase noise. What is the source? 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. Source in both cases is an HP Z3805 GPSDO. I didn't insert an additional buffer, however, the Z3805 has two (buffered) outputs. I used one for counter reference, the other one for counter input. Volker ___ 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] ADEV from phase or frequency measurement
On 09/03/14 22:36, Volker Esper wrote: Am 09.03.2014 19:46, schrieb Magnus Danielson: On 04/03/14 01:05, Volker Esper wrote: Am 03.03.2014 23:04, schrieb Magnus Danielson: Volker, On 03/03/14 00:50, Volker Esper wrote: Sorry for the time delay... TIC: SR620 with Z3805 as external reference; signal source Nortel/Trimble GPSTM (GPSDO) 10MHz output Enclosed two plots (SW: Plotter): - one is sigma(tau) calculated from phase samples (SR620 TIME mode), - the other one is sigma(tau) from frequency data (SR620 FREQ mode) Whole equipment had a power up time of several days/weeks. Room temperature was stable over both measurements (within about 2 degrees C). The SR620 uses a bit different path through the logic when doing TI and FREQ measurements. The frequency measurement has a feature that means that the time error between start and stop signal needs to be calibrated out. This can be done using the calibration routines given in the manual. This should not affect the ADEV measure, but as a precaution. Try doing a pair of noise-floor measurements. That is, feed the reference 10 MHz to the A input for the frequency noise measurement. Then, for the TI noise-floor measurement, put a T on the A input, put it in high-Z mode and then use a 1 m cable to put the signal onto the B input which is terminating. You indeed have a higher level. Your initial shape makes me wonder. I would really like to get the TimeLab measurement files and eye-ball them closer. If you plot the phase or frequency, it may be easier to spot systematic wobbles. TDEV would also help, as it provides a general *tau scaling to the ADEV plot. 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. I already did these measurements, I stick the plots at this posting. - The plot with the long file name shows frequency mode measurement: 10MHz external reference put into channel A. - ...Plot2 shows a phase measurement, where I fed the reference signal via a home made 50 ohms splitter into both input channels. (I prefer feeding the channels symmetrically) Both plots show linear negative gradients, but the phase plot is steeper. The frequency plot transitions into a horizontal at about 1000s. The 1/sqrt(tau) curve is higher than the background noise of the counter. That flicker phase noise is more typical of a buffer or source than of the counter. For shorter taus I would expect the white noise to dominate. I'm just surprised about the level of flicker phase noise. What is the source? 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. Source in both cases is an HP Z3805 GPSDO. I didn't insert an additional buffer, however, the Z3805 has two (buffered) outputs. I used one for counter reference, the other one for counter input. Hmm... what is the noise when you measure it on the SR620 itself? It seems a little high here. 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] ADEV from phase or frequency measurement
Hi Do you routinely do arc welding while waiting for an ADEV plot to finish :)… (I drink beer, but not everybody is into that …) You might consider trying a passive splitter on one of the outputs of the GPSDO. There aren’t many ways they will mess up a signal other than by dropping it’s level. If level is a concern then indeed they could be an issue. Bob On Mar 9, 2014, at 6:17 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 09/03/14 22:36, Volker Esper wrote: Am 09.03.2014 19:46, schrieb Magnus Danielson: On 04/03/14 01:05, Volker Esper wrote: Am 03.03.2014 23:04, schrieb Magnus Danielson: Volker, On 03/03/14 00:50, Volker Esper wrote: Sorry for the time delay... TIC: SR620 with Z3805 as external reference; signal source Nortel/Trimble GPSTM (GPSDO) 10MHz output Enclosed two plots (SW: Plotter): - one is sigma(tau) calculated from phase samples (SR620 TIME mode), - the other one is sigma(tau) from frequency data (SR620 FREQ mode) Whole equipment had a power up time of several days/weeks. Room temperature was stable over both measurements (within about 2 degrees C). The SR620 uses a bit different path through the logic when doing TI and FREQ measurements. The frequency measurement has a feature that means that the time error between start and stop signal needs to be calibrated out. This can be done using the calibration routines given in the manual. This should not affect the ADEV measure, but as a precaution. Try doing a pair of noise-floor measurements. That is, feed the reference 10 MHz to the A input for the frequency noise measurement. Then, for the TI noise-floor measurement, put a T on the A input, put it in high-Z mode and then use a 1 m cable to put the signal onto the B input which is terminating. You indeed have a higher level. Your initial shape makes me wonder. I would really like to get the TimeLab measurement files and eye-ball them closer. If you plot the phase or frequency, it may be easier to spot systematic wobbles. TDEV would also help, as it provides a general *tau scaling to the ADEV plot. 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. I already did these measurements, I stick the plots at this posting. - The plot with the long file name shows frequency mode measurement: 10MHz external reference put into channel A. - ...Plot2 shows a phase measurement, where I fed the reference signal via a home made 50 ohms splitter into both input channels. (I prefer feeding the channels symmetrically) Both plots show linear negative gradients, but the phase plot is steeper. The frequency plot transitions into a horizontal at about 1000s. The 1/sqrt(tau) curve is higher than the background noise of the counter. That flicker phase noise is more typical of a buffer or source than of the counter. For shorter taus I would expect the white noise to dominate. I'm just surprised about the level of flicker phase noise. What is the source? 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. Source in both cases is an HP Z3805 GPSDO. I didn't insert an additional buffer, however, the Z3805 has two (buffered) outputs. I used one for counter reference, the other one for counter input. Hmm... what is the noise when you measure it on the SR620 itself? It seems a little high here. 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. ___ 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] ADEV from phase or frequency measurement
Bob, I sometimes indeed do arc welding, as well as forging... But that's another story. When waiting for an ADEV measurement I sit still, trying not to move a millimeter. Seriously, I try to avoid any rf noise, e.g. ham radio, any airflow, any temperature change. I log supply voltages and check, if there's anything odd. I avoid any switching supply. I regularely check, if any switching voltage regulator (TV, monitors, PC,...) disturbs my rf ether... As the legends of my plots tell, I do use a passive splitter to get two similar signals (start and stop) for phase measurement. But I haven't used it for splitting the 10MHz for frequency measurement (reference and input). Lower level is a concern, since it increases phase jitter. Volker Am 09.03.2014 23:32, schrieb Bob Camp: Hi Do you routinely do arc welding while waiting for an ADEV plot to finish :)… (I drink beer, but not everybody is into that …) You might consider trying a passive splitter on one of the outputs of the GPSDO. There aren’t many ways they will mess up a signal other than by dropping it’s level. If level is a concern then indeed they could be an issue. Bob On Mar 9, 2014, at 6:17 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 09/03/14 22:36, Volker Esper wrote: Am 09.03.2014 19:46, schrieb Magnus Danielson: On 04/03/14 01:05, Volker Esper wrote: Am 03.03.2014 23:04, schrieb Magnus Danielson: Volker, On 03/03/14 00:50, Volker Esper wrote: Sorry for the time delay... TIC: SR620 with Z3805 as external reference; signal source Nortel/Trimble GPSTM (GPSDO) 10MHz output Enclosed two plots (SW: Plotter): - one is sigma(tau) calculated from phase samples (SR620 TIME mode), - the other one is sigma(tau) from frequency data (SR620 FREQ mode) Whole equipment had a power up time of several days/weeks. Room temperature was stable over both measurements (within about 2 degrees C). The SR620 uses a bit different path through the logic when doing TI and FREQ measurements. The frequency measurement has a feature that means that the time error between start and stop signal needs to be calibrated out. This can be done using the calibration routines given in the manual. This should not affect the ADEV measure, but as a precaution. Try doing a pair of noise-floor measurements. That is, feed the reference 10 MHz to the A input for the frequency noise measurement. Then, for the TI noise-floor measurement, put a T on the A input, put it in high-Z mode and then use a 1 m cable to put the signal onto the B input which is terminating. You indeed have a higher level. Your initial shape makes me wonder. I would really like to get the TimeLab measurement files and eye-ball them closer. If you plot the phase or frequency, it may be easier to spot systematic wobbles. TDEV would also help, as it provides a general *tau scaling to the ADEV plot. 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. I already did these measurements, I stick the plots at this posting. - The plot with the long file name shows frequency mode measurement: 10MHz external reference put into channel A. - ...Plot2 shows a phase measurement, where I fed the reference signal via a home made 50 ohms splitter into both input channels. (I prefer feeding the channels symmetrically) Both plots show linear negative gradients, but the phase plot is steeper. The frequency plot transitions into a horizontal at about 1000s. The 1/sqrt(tau) curve is higher than the background noise of the counter. That flicker phase noise is more typical of a buffer or source than of the counter. For shorter taus I would expect the white noise to dominate. I'm just surprised about the level of flicker phase noise. What is the source? 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. Source in both cases is an HP Z3805 GPSDO. I didn't insert an additional buffer, however, the Z3805 has two (buffered) outputs. I used one for counter reference, the other one for counter input. Hmm... what is the noise when you measure it on the SR620 itself? It seems a little high here. 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. ___ 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 --
Re: [time-nuts] ADEV from phase or frequency measurement
Hi So far, I have not found the 3db lost in a a passive splitter to be a problem with anything I have played with. With proper termination , they seem to be a good thing to use. Bob On Mar 9, 2014, at 7:55 PM, Volker Esper ail...@t-online.de wrote: Bob, I sometimes indeed do arc welding, as well as forging... But that's another story. When waiting for an ADEV measurement I sit still, trying not to move a millimeter. Seriously, I try to avoid any rf noise, e.g. ham radio, any airflow, any temperature change. I log supply voltages and check, if there's anything odd. I avoid any switching supply. I regularely check, if any switching voltage regulator (TV, monitors, PC,...) disturbs my rf ether... As the legends of my plots tell, I do use a passive splitter to get two similar signals (start and stop) for phase measurement. But I haven't used it for splitting the 10MHz for frequency measurement (reference and input). Lower level is a concern, since it increases phase jitter. Volker Am 09.03.2014 23:32, schrieb Bob Camp: Hi Do you routinely do arc welding while waiting for an ADEV plot to finish :)… (I drink beer, but not everybody is into that …) You might consider trying a passive splitter on one of the outputs of the GPSDO. There aren’t many ways they will mess up a signal other than by dropping it’s level. If level is a concern then indeed they could be an issue. Bob On Mar 9, 2014, at 6:17 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 09/03/14 22:36, Volker Esper wrote: Am 09.03.2014 19:46, schrieb Magnus Danielson: On 04/03/14 01:05, Volker Esper wrote: Am 03.03.2014 23:04, schrieb Magnus Danielson: Volker, On 03/03/14 00:50, Volker Esper wrote: Sorry for the time delay... TIC: SR620 with Z3805 as external reference; signal source Nortel/Trimble GPSTM (GPSDO) 10MHz output Enclosed two plots (SW: Plotter): - one is sigma(tau) calculated from phase samples (SR620 TIME mode), - the other one is sigma(tau) from frequency data (SR620 FREQ mode) Whole equipment had a power up time of several days/weeks. Room temperature was stable over both measurements (within about 2 degrees C). The SR620 uses a bit different path through the logic when doing TI and FREQ measurements. The frequency measurement has a feature that means that the time error between start and stop signal needs to be calibrated out. This can be done using the calibration routines given in the manual. This should not affect the ADEV measure, but as a precaution. Try doing a pair of noise-floor measurements. That is, feed the reference 10 MHz to the A input for the frequency noise measurement. Then, for the TI noise-floor measurement, put a T on the A input, put it in high-Z mode and then use a 1 m cable to put the signal onto the B input which is terminating. You indeed have a higher level. Your initial shape makes me wonder. I would really like to get the TimeLab measurement files and eye-ball them closer. If you plot the phase or frequency, it may be easier to spot systematic wobbles. TDEV would also help, as it provides a general *tau scaling to the ADEV plot. 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. I already did these measurements, I stick the plots at this posting. - The plot with the long file name shows frequency mode measurement: 10MHz external reference put into channel A. - ...Plot2 shows a phase measurement, where I fed the reference signal via a home made 50 ohms splitter into both input channels. (I prefer feeding the channels symmetrically) Both plots show linear negative gradients, but the phase plot is steeper. The frequency plot transitions into a horizontal at about 1000s. The 1/sqrt(tau) curve is higher than the background noise of the counter. That flicker phase noise is more typical of a buffer or source than of the counter. For shorter taus I would expect the white noise to dominate. I'm just surprised about the level of flicker phase noise. What is the source? 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. Source in both cases is an HP Z3805 GPSDO. I didn't insert an additional buffer, however, the Z3805 has two (buffered) outputs. I used one for counter reference, the other one for counter input. Hmm... what is the noise when you measure it on the SR620 itself? It seems a little high here. 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
[time-nuts] Range of Sawtooth values?
Just curious as to the range of sawtooth values that are typical for timing receivers. What's the maximum correction needed? Thanks jim ab3cv ___ 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] Range of Sawtooth values?
Just curious as to the range of sawtooth values that are typical for timing receivers. What's the maximum correction needed? Thanks jim ab3cv It depends very much on the receiver. It's easy to measure, though. http://www.febo.com/pipermail/time-nuts/2005-April/018114.html http://leapsecond.com/pages/gps4/cns-1pps.gif http://www.febo.com/pipermail/time-nuts/2005-January/017677.html http://leapsecond.com/pages/vp/sawtooth.htm http://leapsecond.com/pages/m12/sawtooth.htm http://leapsecond.com/pages/MG1613S/ This picture is worth eighty six thousand words: http://leapsecond.com/pages/MG1613S/tic-day2.gif /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Range of Sawtooth values?
On Sun, Mar 9, 2014 at 7:11 PM, Jim Miller j...@jtmiller.com wrote: Just curious as to the range of sawtooth values that are typical for timing receivers. What's the maximum correction needed? I just recently looked at this at least for the Oncore series of receivers. The magnitude of the sawtooth seems to scale with the accuracy of the PPS. In other words the newer and better receivers have both a more accurate PPS and a smaller sawtooth correction.It makes sense. If less correction is needed the magnitude of the correction is less. The M12 user manual hints at why, they say the newer receiver runs on a faster internal clock. I think the sawtooth correction is always larger than the one sigma error. In other words if you ignore it, then that is the major error in the PPS. Beware of some very old data on this, made back when the UT was new. They still had SA turned on back then. -- Chris Albertson Redondo Beach, California ___ 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.
