Re: [time-nuts] ADEV from phase or frequency measurement
Even if the -3dB were an issue, I'd have much more faith in a clear, passive resistor network than in a complex amplifier with all it's unknown non linear characteristics, temperature dependent time delays, noise sources, etc., etc. This simple home made network is a useful, manageable gadget. Volker Bob Camp li...@rtty.us hat am 10. März 2014 um 01:47 geschrieben: 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
Re: [time-nuts] ADEV from phase or frequency measurement
Hi I’ve played with both the 6 db loss resistive splitters and the transformer based 3 db loss splitters. They both seem to be fine for splitting precision 10 MHz signals. For a while I avoided the transformer based parts, but not for any reason I could prove. Bob On Mar 10, 2014, at 7:41 AM, Volker Esper ail...@t-online.de wrote: Even if the -3dB were an issue, I'd have much more faith in a clear, passive resistor network than in a complex amplifier with all it's unknown non linear characteristics, temperature dependent time delays, noise sources, etc., etc. This simple home made network is a useful, manageable gadget. Volker Bob Camp li...@rtty.us hat am 10. März 2014 um 01:47 geschrieben: 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
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
Re: [time-nuts] ADEV from phase or frequency measurement
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.
Re: [time-nuts] ADEV from phase or frequency measurement
Hi Volker, Either phase or frequency raw data can be used to generate an ADEV plot, but you have to use different methods depending on the data type. See the two formulas for Allan Variance in: http://www.wriley.com/paper2ht.htm Usually we use the x form of the formula, where x is an array of phase samples. But if you have frequency samples then use the y form instead, where y is an array of frequency samples. Note you can also convert phase data to frequency data (by differentiating) and use the y form. Or convert frequency data to phase data (by integrating) and use the x form. /tvb - Original Message - From: Volker Esper ail...@t-online.de To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, March 01, 2014 3:15 AM Subject: [time-nuts] ADEV from phase or frequency measurement Hello dear fellow time-nuts, I stumbled over a question that may sound stupid to you: Is the usual ADEV plot the result of a phase or a frequency measurement? I get totally different results when comparing a phase and a frequency measurement of the same source. Or am I doing something totally wrong? Thanks a lot 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
Thank you, Tom, so far. Yes, I know that I have to use different formulas, but - of course - I didn't calculate the ADEV curves myself, I let some software do the job, namely Ulrich's Plotter and TimeLab as well. Plotter has a menu item, where you have to check if you deal with phase or frequency data, so I assumed the software would do right. I am confused. The ADEVs of the phase data are about 10 times better and have a different shape... Volker Am 01.03.2014 12:37, schrieb Tom Van Baak: Hi Volker, Either phase or frequency raw data can be used to generate an ADEV plot, but you have to use different methods depending on the data type. See the two formulas for Allan Variance in: http://www.wriley.com/paper2ht.htm Usually we use the x form of the formula, where x is an array of phase samples. But if you have frequency samples then use the y form instead, where y is an array of frequency samples. Note you can also convert phase data to frequency data (by differentiating) and use the y form. Or convert frequency data to phase data (by integrating) and use the x form. /tvb - Original Message - From: Volker Esper ail...@t-online.de To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, March 01, 2014 3:15 AM Subject: [time-nuts] ADEV from phase or frequency measurement Hello dear fellow time-nuts, I stumbled over a question that may sound stupid to you: Is the usual ADEV plot the result of a phase or a frequency measurement? I get totally different results when comparing a phase and a frequency measurement of the same source. Or am I doing something totally wrong? Thanks a lot 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. ___ 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
Here is python code for the most common deviations https://github.com/aewallin/allantools/blob/master/allantools/allantools.py each statistic (ADEV, MDEV, TDEV, and so on) has two functions. one takes fractional frequency data, the other phase data. frequency2phase() and phase2freqeuncy() show how the conversions are done. Your patches are welcome! Anders On Sat, Mar 1, 2014 at 1:37 PM, Tom Van Baak t...@leapsecond.com wrote: Hi Volker, Either phase or frequency raw data can be used to generate an ADEV plot, but you have to use different methods depending on the data type. See the two formulas for Allan Variance in: http://www.wriley.com/paper2ht.htm Usually we use the x form of the formula, where x is an array of phase samples. But if you have frequency samples then use the y form instead, where y is an array of frequency samples. Note you can also convert phase data to frequency data (by differentiating) and use the y form. Or convert frequency data to phase data (by integrating) and use the x form. /tvb - Original Message - From: Volker Esper ail...@t-online.de To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, March 01, 2014 3:15 AM Subject: [time-nuts] ADEV from phase or frequency measurement Hello dear fellow time-nuts, I stumbled over a question that may sound stupid to you: Is the usual ADEV plot the result of a phase or a frequency measurement? I get totally different results when comparing a phase and a frequency measurement of the same source. Or am I doing something totally wrong? Thanks a lot 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. ___ 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
Volker, On 01/03/14 12:15, Volker Esper wrote: Hello dear fellow time-nuts, I stumbled over a question that may sound stupid to you: Is the usual ADEV plot the result of a phase or a frequency measurement? I get totally different results when comparing a phase and a frequency measurement of the same source. Or am I doing something totally wrong? The core of the ADEV is the square of the second degree derivate of phase, where the phase measures are tau seconds away from each other. You can use frequency measures, but it is likely that the start-point of the next measure is not the end point of the previous frequency measure. Then you have dead-time. Dead-time causes a bias in the ADEV measure and you need to use the dead-time bias function to compensate for this effect. This was explained by Dave Allan in his Feb 1966 article, as the 2-point dead-time free variance was the unification of a large range of different measures, and he supplied the bias functions to unify them. Now that there was one variance to forge them all, they kept referring to it as Allan's variance and well, it's now history. Another aspect is that your counter may do some smart filtering on the measures it makes. This reduces the bandwidth of the counter as the averaging removes noise. This also causes low-tau values that has white-phase noise to be lower than expected. This improvement is however not helping you to get better ADEV, it just fools you, as the ADEV of white phase noise will depend on the measurement bandwidth, known for a long time but ignored my many measurement setups. I've tried to cover these topics on the Allan Variance Wikipedia article. I would avoid using frequency measures from counters if phase measures can be made, as you can avoid both these issues rather than requiring to measure their effect and compensate for it. It is tricky to maintain valid numbers that way. There are cases where ADEV is better calculated from frequency measures, so it is a valid tool, but care always needs to be taken to make sure the numbers remains scaled properly. 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
On 01/03/14 13:25, Volker Esper wrote: Thank you, Tom, so far. Yes, I know that I have to use different formulas, but - of course - I didn't calculate the ADEV curves myself, I let some software do the job, namely Ulrich's Plotter and TimeLab as well. Plotter has a menu item, where you have to check if you deal with phase or frequency data, so I assumed the software would do right. I am confused. The ADEVs of the phase data are about 10 times better and have a different shape... Can you supply the TimeLab plots or even measurement files? What was your counter and setup? 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
This is because usually a counter that has the time interval feature behaves better in time interval mode. As already pointed out here, use always the time interval mode to take samples for the Allan deviation. In frequency mode the counter uses average or various tricks to smooth readings, so better to switch to time interval mode in order to take clean samples for the post processing. On Sat, Mar 1, 2014 at 1:25 PM, Volker Esper ail...@t-online.de wrote: Thank you, Tom, so far. Yes, I know that I have to use different formulas, but - of course - I didn't calculate the ADEV curves myself, I let some software do the job, namely Ulrich's Plotter and TimeLab as well. Plotter has a menu item, where you have to check if you deal with phase or frequency data, so I assumed the software would do right. I am confused. The ADEVs of the phase data are about 10 times better and have a different shape... Volker Am 01.03.2014 12:37, schrieb Tom Van Baak: Hi Volker, Either phase or frequency raw data can be used to generate an ADEV plot, but you have to use different methods depending on the data type. See the two formulas for Allan Variance in: http://www.wriley.com/paper2ht.htm Usually we use the x form of the formula, where x is an array of phase samples. But if you have frequency samples then use the y form instead, where y is an array of frequency samples. Note you can also convert phase data to frequency data (by differentiating) and use the y form. Or convert frequency data to phase data (by integrating) and use the x form. /tvb - Original Message - From: Volker Esper ail...@t-online.de To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, March 01, 2014 3:15 AM Subject: [time-nuts] ADEV from phase or frequency measurement Hello dear fellow time-nuts, I stumbled over a question that may sound stupid to you: Is the usual ADEV plot the result of a phase or a frequency measurement? I get totally different results when comparing a phase and a frequency measurement of the same source. Or am I doing something totally wrong? Thanks a lot 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. ___ 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.
