Re: [time-nuts] Z3805 two frequency maxima
I agree. Please, Paul, start a new thread, and we'll be there. Volker Am 28.11.2012 08:10, schrieb Hal Murray: You might get better answers by starting a new thread rather than hiding your question in an existing thread. (Use your New message button rather than Reply, and cut-paste the To address from an old message, then type in the new Subject.) Using a useful Subject also helps people find things in the archives. paul.destef...@willamettealumni.com said: We have an application in which we plan to travel 7 hours with an SR620 turned off, then turn it on for 1 hour and take measurements we expect to be accurate to less than 1ns. I would appreciate more information about how to get reliable data out of this instrument. What do you mean by accurate to less than 1ns? What are you trying to measure? The internal clock in the SR620 may be off a bit. The specs should be in the users manual. In general, you have to wait a while for it to warm up and it will depend on which options you have. (Some units have good crystals. Some have low cost crystals to save $$ if they will normally run off an in-house reference clock.) Suppose it's worst case 1 part in 1E9, just to pick a handy number to work with. If you measure the width of a 1 microsecond pulse, the error from the clock will be 1E-15 seconds or 1E-6 ns. If you measure the time between 2 consecutive PPS pulses, the error from the clock will be 1E-9 seconds or 1 ns. ___ 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] Z3805 two frequency maxima
...and I found a very interesting article on that topic: http://www.micrel.com/_PDF/App-Notes/clk/PAN1202291%20-%20AFM%20Period%20Jitter.pdf It's written by Eddy van Keulen (Micrel): Relation between Harmonics and Deterministic Jitter. His approach is the assumption, that frequency modulationt causes a spectrum with 10MHz and 5MHz (and of course 15MHz). Using the FM thesis and formulas give us a very graphic description of the observed two-maxima-histograms (a.k.a. bimodal or double peak). I'll do more experiments and calculations at the weekend. Volker Am 28.11.2012 01:36, schrieb Volker Esper: Now, that you ask: the measurements are in that range, yes, though it's not exactly the values. time shift 12ns - spacing 10ns 28ns 35ns 66ns 55ns 0ns 8ns and yes, the peaks get closer while reducing the amplitude of the 5MHz, it's almost exactly linear: With the 10MHz at 200mV and a time shift of 66ns, I measured the following spacings: 5MHz voltage in mV spacing in ns 200 55 100 27.5 50 13.0 25 6.5 12.5 3.3 6.3 1.6 3.2 0.86 1.6 0.44 0.8 0,24 The functional relation of voltage ratio and spacing is quite obvious. I have to admit, that my counter is not at it's optimal calibration. I will adjust it first before I can tell you more. To be precise: all these findings were made while trying to adjust the trigger circuits of the counter. To do that I needed a well designed 180 degrees power splitter - but I didn't have one at the time. I've received a Mini Circuits ZSCJ-2-2 recently, now I can go on with my adjustments. Though the SR620 TIC is a great instrument when hunting the pico seconds we have to realize, that it's a thermal design desaster (I have to apologize to all sr620 friends). I have to run it for at least 12 hours if not 24 to be shure, that every single part is at a more or less stationary thermal state. Some (NERC) say ...never switch it off. I can't do that during the week, we have to wait till weekend. Thanks for your response Volker Am 28.11.2012 00:25, schrieb Azelio Boriani: Very interesting indeed. Two questions: after adding the 66nS phase shift, were the two peaks at 66nS when at the same amplitude? Then, while reducing the amplitude of the 5MHz, were they getting closer (until the 240pS)? On Tue, Nov 27, 2012 at 9:21 PM, Bob Campli...@rtty.us wrote: Hi Phase does indeed matter, it just messes up the math. Most multiplier / filter combinations have significant phase shift between the sub-harmonic and the carrier. You rarely know what the phase shift is, but you can read the sub-harmonic. The simple db to jitter ratio gets you close enough to make rational decisions on how much filtering you need. You could play with filter phase but I've never seen that done in practice. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: Tuesday, November 27, 2012 2:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Z3805 two frequency maxima I followed your argument and tried to synthesize such a signal. I built a simple power combiner (3 times 18 ohms resistors) and combined the 10 MHz reference output of my signal generator with a 5 MHz signal from the same generators regular output at the same amplitude. My oscilloscope showed the locked phase of the two signals. I applied this combo signal to the SR620 and observed a wonderful two-maxima histogram. When reducing the amplitude of the 5 MHz signal (while keeping the 10 MHz amplitude) the peaks distance decreased linearly with the voltage reduction, until the peaks melted togehter at about -20dBc. On the one hand it was a success, but why only 20dBc? My experiences with the Z3805 showed a 5 MHz subharmonic at 62dBc and the peaks spaced at 60 ps. So I startet to add phase delay to the 5 MHz signal by looping-in some meters of coax cable. When coming to a delay time of 66 ns I could distinguish the two peaks at a spacing of 240 ps down to an amplitude ratio of about 1000, that is, 60dB. Volker Am 18.11.2012 03:36, schrieb Bob Camp: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's
Re: [time-nuts] Z3805 two frequency maxima
Hi The gotcha there is that most oscillators have a low pass filter on the output. There is an observable 5 MHz component, but the 15 MHz is much further down. The synthesis is useful. It's just tough to convince anybody it's correct when they can't see the 15 MHz. Bob On Nov 28, 2012, at 4:19 AM, Volker Esper ail...@t-online.de wrote: ...and I found a very interesting article on that topic: http://www.micrel.com/_PDF/App-Notes/clk/PAN1202291%20-%20AFM%20Period%20Jitter.pdf It's written by Eddy van Keulen (Micrel): Relation between Harmonics and Deterministic Jitter. His approach is the assumption, that frequency modulationt causes a spectrum with 10MHz and 5MHz (and of course 15MHz). Using the FM thesis and formulas give us a very graphic description of the observed two-maxima-histograms (a.k.a. bimodal or double peak). I'll do more experiments and calculations at the weekend. Volker Am 28.11.2012 01:36, schrieb Volker Esper: Now, that you ask: the measurements are in that range, yes, though it's not exactly the values. time shift 12ns - spacing 10ns 28ns 35ns 66ns 55ns 0ns 8ns and yes, the peaks get closer while reducing the amplitude of the 5MHz, it's almost exactly linear: With the 10MHz at 200mV and a time shift of 66ns, I measured the following spacings: 5MHz voltage in mV spacing in ns 200 55 100 27.5 50 13.0 25 6.5 12.5 3.3 6.3 1.6 3.2 0.86 1.6 0.44 0.8 0,24 The functional relation of voltage ratio and spacing is quite obvious. I have to admit, that my counter is not at it's optimal calibration. I will adjust it first before I can tell you more. To be precise: all these findings were made while trying to adjust the trigger circuits of the counter. To do that I needed a well designed 180 degrees power splitter - but I didn't have one at the time. I've received a Mini Circuits ZSCJ-2-2 recently, now I can go on with my adjustments. Though the SR620 TIC is a great instrument when hunting the pico seconds we have to realize, that it's a thermal design desaster (I have to apologize to all sr620 friends). I have to run it for at least 12 hours if not 24 to be shure, that every single part is at a more or less stationary thermal state. Some (NERC) say ...never switch it off. I can't do that during the week, we have to wait till weekend. Thanks for your response Volker Am 28.11.2012 00:25, schrieb Azelio Boriani: Very interesting indeed. Two questions: after adding the 66nS phase shift, were the two peaks at 66nS when at the same amplitude? Then, while reducing the amplitude of the 5MHz, were they getting closer (until the 240pS)? On Tue, Nov 27, 2012 at 9:21 PM, Bob Campli...@rtty.us wrote: Hi Phase does indeed matter, it just messes up the math. Most multiplier / filter combinations have significant phase shift between the sub-harmonic and the carrier. You rarely know what the phase shift is, but you can read the sub-harmonic. The simple db to jitter ratio gets you close enough to make rational decisions on how much filtering you need. You could play with filter phase but I've never seen that done in practice. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: Tuesday, November 27, 2012 2:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Z3805 two frequency maxima I followed your argument and tried to synthesize such a signal. I built a simple power combiner (3 times 18 ohms resistors) and combined the 10 MHz reference output of my signal generator with a 5 MHz signal from the same generators regular output at the same amplitude. My oscilloscope showed the locked phase of the two signals. I applied this combo signal to the SR620 and observed a wonderful two-maxima histogram. When reducing the amplitude of the 5 MHz signal (while keeping the 10 MHz amplitude) the peaks distance decreased linearly with the voltage reduction, until the peaks melted togehter at about -20dBc. On the one hand it was a success, but why only 20dBc? My experiences with the Z3805 showed a 5 MHz subharmonic at 62dBc and the peaks spaced at 60 ps. So I startet to add phase delay to the 5 MHz signal by looping-in some meters of coax cable. When coming to a delay time of 66 ns I could distinguish the two peaks at a spacing of 240 ps down to an amplitude ratio of about 1000, that is, 60dB. Volker Am 18.11.2012 03:36, schrieb Bob Camp: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might
Re: [time-nuts] Z3805 two frequency maxima
I followed your argument and tried to synthesize such a signal. I built a simple power combiner (3 times 18 ohms resistors) and combined the 10 MHz reference output of my signal generator with a 5 MHz signal from the same generators regular output at the same amplitude. My oscilloscope showed the locked phase of the two signals. I applied this combo signal to the SR620 and observed a wonderful two-maxima histogram. When reducing the amplitude of the 5 MHz signal (while keeping the 10 MHz amplitude) the peaks distance decreased linearly with the voltage reduction, until the peaks melted togehter at about -20dBc. On the one hand it was a success, but why only 20dBc? My experiences with the Z3805 showed a 5 MHz subharmonic at 62dBc and the peaks spaced at 60 ps. So I startet to add phase delay to the 5 MHz signal by looping-in some meters of coax cable. When coming to a delay time of 66 ns I could distinguish the two peaks at a spacing of 240 ps down to an amplitude ratio of about 1000, that is, 60dB. Volker Am 18.11.2012 03:36, schrieb Bob Camp: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.dewrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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. ___ 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] Z3805 two frequency maxima
Hi Phase does indeed matter, it just messes up the math. Most multiplier / filter combinations have significant phase shift between the sub-harmonic and the carrier. You rarely know what the phase shift is, but you can read the sub-harmonic. The simple db to jitter ratio gets you close enough to make rational decisions on how much filtering you need. You could play with filter phase but I've never seen that done in practice. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: Tuesday, November 27, 2012 2:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Z3805 two frequency maxima I followed your argument and tried to synthesize such a signal. I built a simple power combiner (3 times 18 ohms resistors) and combined the 10 MHz reference output of my signal generator with a 5 MHz signal from the same generators regular output at the same amplitude. My oscilloscope showed the locked phase of the two signals. I applied this combo signal to the SR620 and observed a wonderful two-maxima histogram. When reducing the amplitude of the 5 MHz signal (while keeping the 10 MHz amplitude) the peaks distance decreased linearly with the voltage reduction, until the peaks melted togehter at about -20dBc. On the one hand it was a success, but why only 20dBc? My experiences with the Z3805 showed a 5 MHz subharmonic at 62dBc and the peaks spaced at 60 ps. So I startet to add phase delay to the 5 MHz signal by looping-in some meters of coax cable. When coming to a delay time of 66 ns I could distinguish the two peaks at a spacing of 240 ps down to an amplitude ratio of about 1000, that is, 60dB. Volker Am 18.11.2012 03:36, schrieb Bob Camp: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg ___ 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. ___ 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
Re: [time-nuts] Z3805 two frequency maxima
Very interesting indeed. Two questions: after adding the 66nS phase shift, were the two peaks at 66nS when at the same amplitude? Then, while reducing the amplitude of the 5MHz, were they getting closer (until the 240pS)? On Tue, Nov 27, 2012 at 9:21 PM, Bob Camp li...@rtty.us wrote: Hi Phase does indeed matter, it just messes up the math. Most multiplier / filter combinations have significant phase shift between the sub-harmonic and the carrier. You rarely know what the phase shift is, but you can read the sub-harmonic. The simple db to jitter ratio gets you close enough to make rational decisions on how much filtering you need. You could play with filter phase but I've never seen that done in practice. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: Tuesday, November 27, 2012 2:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Z3805 two frequency maxima I followed your argument and tried to synthesize such a signal. I built a simple power combiner (3 times 18 ohms resistors) and combined the 10 MHz reference output of my signal generator with a 5 MHz signal from the same generators regular output at the same amplitude. My oscilloscope showed the locked phase of the two signals. I applied this combo signal to the SR620 and observed a wonderful two-maxima histogram. When reducing the amplitude of the 5 MHz signal (while keeping the 10 MHz amplitude) the peaks distance decreased linearly with the voltage reduction, until the peaks melted togehter at about -20dBc. On the one hand it was a success, but why only 20dBc? My experiences with the Z3805 showed a 5 MHz subharmonic at 62dBc and the peaks spaced at 60 ps. So I startet to add phase delay to the 5 MHz signal by looping-in some meters of coax cable. When coming to a delay time of 66 ns I could distinguish the two peaks at a spacing of 240 ps down to an amplitude ratio of about 1000, that is, 60dB. Volker Am 18.11.2012 03:36, schrieb Bob Camp: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg ___ 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
Re: [time-nuts] Z3805 two frequency maxima
Now, that you ask: the measurements are in that range, yes, though it's not exactly the values. time shift 12ns - spacing 10ns 28ns35ns 66ns55ns 0ns 8ns and yes, the peaks get closer while reducing the amplitude of the 5MHz, it's almost exactly linear: With the 10MHz at 200mV and a time shift of 66ns, I measured the following spacings: 5MHz voltage in mV spacing in ns 20055 10027.5 5013.0 25 6.5 12.5 3.3 6.3 1.6 3.2 0.86 1.6 0.44 0.8 0,24 The functional relation of voltage ratio and spacing is quite obvious. I have to admit, that my counter is not at it's optimal calibration. I will adjust it first before I can tell you more. To be precise: all these findings were made while trying to adjust the trigger circuits of the counter. To do that I needed a well designed 180 degrees power splitter - but I didn't have one at the time. I've received a Mini Circuits ZSCJ-2-2 recently, now I can go on with my adjustments. Though the SR620 TIC is a great instrument when hunting the pico seconds we have to realize, that it's a thermal design desaster (I have to apologize to all sr620 friends). I have to run it for at least 12 hours if not 24 to be shure, that every single part is at a more or less stationary thermal state. Some (NERC) say ...never switch it off. I can't do that during the week, we have to wait till weekend. Thanks for your response Volker Am 28.11.2012 00:25, schrieb Azelio Boriani: Very interesting indeed. Two questions: after adding the 66nS phase shift, were the two peaks at 66nS when at the same amplitude? Then, while reducing the amplitude of the 5MHz, were they getting closer (until the 240pS)? On Tue, Nov 27, 2012 at 9:21 PM, Bob Campli...@rtty.us wrote: Hi Phase does indeed matter, it just messes up the math. Most multiplier / filter combinations have significant phase shift between the sub-harmonic and the carrier. You rarely know what the phase shift is, but you can read the sub-harmonic. The simple db to jitter ratio gets you close enough to make rational decisions on how much filtering you need. You could play with filter phase but I've never seen that done in practice. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper Sent: Tuesday, November 27, 2012 2:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Z3805 two frequency maxima I followed your argument and tried to synthesize such a signal. I built a simple power combiner (3 times 18 ohms resistors) and combined the 10 MHz reference output of my signal generator with a 5 MHz signal from the same generators regular output at the same amplitude. My oscilloscope showed the locked phase of the two signals. I applied this combo signal to the SR620 and observed a wonderful two-maxima histogram. When reducing the amplitude of the 5 MHz signal (while keeping the 10 MHz amplitude) the peaks distance decreased linearly with the voltage reduction, until the peaks melted togehter at about -20dBc. On the one hand it was a success, but why only 20dBc? My experiences with the Z3805 showed a 5 MHz subharmonic at 62dBc and the peaks spaced at 60 ps. So I startet to add phase delay to the 5 MHz signal by looping-in some meters of coax cable. When coming to a delay time of 66 ns I could distinguish the two peaks at a spacing of 240 ps down to an amplitude ratio of about 1000, that is, 60dB. Volker Am 18.11.2012 03:36, schrieb Bob Camp: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns -100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI
Re: [time-nuts] Z3805 two frequency maxima
Greetings! I just joined the list a few hours ago and you have already peeked my interest in this aside: On Tuesday, 27 November 2012, Volker Esper wrote: Though the SR620 TIC is a great instrument when hunting the pico seconds we have to realize, that it's a thermal design desaster (I have to apologize to all sr620 friends). I have to run it for at least 12 hours if not 24 to be shure, that every single part is at a more or less stationary thermal state. Some (NERC) say ...never switch it off. We have an application in which we plan to travel 7 hours with an SR620 turned off, then turn it on for 1 hour and take measurements we expect to be accurate to less than 1ns. I would appreciate more information about how to get reliable data out of this instrument. Thanks, Paul ___ 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] Z3805 two frequency maxima
You might get better answers by starting a new thread rather than hiding your question in an existing thread. (Use your New message button rather than Reply, and cut-paste the To address from an old message, then type in the new Subject.) Using a useful Subject also helps people find things in the archives. paul.destef...@willamettealumni.com said: We have an application in which we plan to travel 7 hours with an SR620 turned off, then turn it on for 1 hour and take measurements we expect to be accurate to less than 1ns. I would appreciate more information about how to get reliable data out of this instrument. What do you mean by accurate to less than 1ns? What are you trying to measure? The internal clock in the SR620 may be off a bit. The specs should be in the users manual. In general, you have to wait a while for it to warm up and it will depend on which options you have. (Some units have good crystals. Some have low cost crystals to save $$ if they will normally run off an in-house reference clock.) Suppose it's worst case 1 part in 1E9, just to pick a handy number to work with. If you measure the width of a 1 microsecond pulse, the error from the clock will be 1E-15 seconds or 1E-6 ns. If you measure the time between 2 consecutive PPS pulses, the error from the clock will be 1E-9 seconds or 1 ns. -- 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] Z3805 two frequency maxima
Hi I've always wondered if the magic A1U1 1820-2312 in the 5380A has a frequency multiplier of some sort in it. I've never dug into it far enough to answer the question though. Bob On Nov 18, 2012, at 8:12 PM, Volker Esper ail...@t-online.de wrote: As far as I can see the PLL loop filter (SR620) has a corner frequency of about 33Hz. My HP counter 5385A has simply a switch to toggle between the external source and the internal osc. Am 18.11.2012 22:45, schrieb Bob Camp: Hi Most modern counters have an internal oscillator that they lock up to the external reference. The PLL bandwidth is (hopefully) chosen to optimize the noise contribution of the internal oscillator (quiet broad band) and the external reference (quiet close in). It will reject anything MHz away from the reference. Even if the reference signal is used directly, it would only be a problem if divided by an odd number. Even number division will wipe out the jitter. The most likely gate times are all a power of 10, so the division should always be even in a counter. Bottom line - you are unlikely to run into trouble using 10 MHz out of a Z3805 as reference signal. Crazy stuff…. Bob On Nov 18, 2012, at 4:35 PM, Volker Esperail...@t-online.de wrote: ...A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter... Yes, I wondered what the histogram would show when using the 2-maxima-Z3805 signal as a reference for the SR620 counter. Would the PLL filter it or would I get a mixer-like result with two maxima in the histogram? I applied the Z3805 to the reference input and the SMX signal generator to the counter input. The histogram looked equal to that I got when using the internal oscillator of the counter for reference. That obviously confirms Bob's statement. Volker Am 18.11.2012 21:23, schrieb Bob Camp: Hi This is one of those interesting areas where a broadband measurement (like a counter) and a narrowband measurement (like a DMTD) will give very different results. The counter will see the sub-harmonic, and call it jitter. It can show up in an ADEV calculation. A DMTD will ignore the sub-harmonic, and show no added jitter. With a DMTD, the ADEV will look fine. A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter. Which one's right / does it matter - as always, that depends on what you are trying to do with the signal. Bob On Nov 18, 2012, at 1:26 PM, Volker Esperail...@t-online.de wrote: @Azelio: Yes, (like Bob told) it's the phase lock, that locks the two maxima. Actually the counter is able to look between the 60ps spaced towers, have a look at the pictures in the first mail of this thread. However, there is a smallest time value the counter can determine, but it is much smaller than 60ps. Volker Am 18.11.2012 17:11, schrieb Bob Camp: Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Borianiazelio.bori...@screen.it wrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Campli...@rtty.uswrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Campli...@rtty.uswrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100
Re: [time-nuts] Z3805 two frequency maxima
Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Camp li...@rtty.us wrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Camp li...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esper ail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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. ___ 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
Re: [time-nuts] Z3805 two frequency maxima
Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Boriani azelio.bori...@screen.it wrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Camp li...@rtty.us wrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Camp li...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esper ail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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
Re: [time-nuts] Z3805 two frequency maxima
@Azelio: Yes, (like Bob told) it's the phase lock, that locks the two maxima. Actually the counter is able to look between the 60ps spaced towers, have a look at the pictures in the first mail of this thread. However, there is a smallest time value the counter can determine, but it is much smaller than 60ps. Volker Am 18.11.2012 17:11, schrieb Bob Camp: Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Borianiazelio.bori...@screen.it wrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Campli...@rtty.us wrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Campli...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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] Z3805 two frequency maxima
Hi This is one of those interesting areas where a broadband measurement (like a counter) and a narrowband measurement (like a DMTD) will give very different results. The counter will see the sub-harmonic, and call it jitter. It can show up in an ADEV calculation. A DMTD will ignore the sub-harmonic, and show no added jitter. With a DMTD, the ADEV will look fine. A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter. Which one's right / does it matter - as always, that depends on what you are trying to do with the signal. Bob On Nov 18, 2012, at 1:26 PM, Volker Esper ail...@t-online.de wrote: @Azelio: Yes, (like Bob told) it's the phase lock, that locks the two maxima. Actually the counter is able to look between the 60ps spaced towers, have a look at the pictures in the first mail of this thread. However, there is a smallest time value the counter can determine, but it is much smaller than 60ps. Volker Am 18.11.2012 17:11, schrieb Bob Camp: Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Borianiazelio.bori...@screen.it wrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Campli...@rtty.us wrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Campli...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ time-nuts mailing list -- time-nuts@febo.com
Re: [time-nuts] Z3805 two frequency maxima
...A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter... Yes, I wondered what the histogram would show when using the 2-maxima-Z3805 signal as a reference for the SR620 counter. Would the PLL filter it or would I get a mixer-like result with two maxima in the histogram? I applied the Z3805 to the reference input and the SMX signal generator to the counter input. The histogram looked equal to that I got when using the internal oscillator of the counter for reference. That obviously confirms Bob's statement. Volker Am 18.11.2012 21:23, schrieb Bob Camp: Hi This is one of those interesting areas where a broadband measurement (like a counter) and a narrowband measurement (like a DMTD) will give very different results. The counter will see the sub-harmonic, and call it jitter. It can show up in an ADEV calculation. A DMTD will ignore the sub-harmonic, and show no added jitter. With a DMTD, the ADEV will look fine. A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter. Which one's right / does it matter - as always, that depends on what you are trying to do with the signal. Bob On Nov 18, 2012, at 1:26 PM, Volker Esperail...@t-online.de wrote: @Azelio: Yes, (like Bob told) it's the phase lock, that locks the two maxima. Actually the counter is able to look between the 60ps spaced towers, have a look at the pictures in the first mail of this thread. However, there is a smallest time value the counter can determine, but it is much smaller than 60ps. Volker Am 18.11.2012 17:11, schrieb Bob Camp: Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Borianiazelio.bori...@screen.it wrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Campli...@rtty.us wrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Campli...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns -100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.dewrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the
Re: [time-nuts] Z3805 two frequency maxima
Hi Most modern counters have an internal oscillator that they lock up to the external reference. The PLL bandwidth is (hopefully) chosen to optimize the noise contribution of the internal oscillator (quiet broad band) and the external reference (quiet close in). It will reject anything MHz away from the reference. Even if the reference signal is used directly, it would only be a problem if divided by an odd number. Even number division will wipe out the jitter. The most likely gate times are all a power of 10, so the division should always be even in a counter. Bottom line - you are unlikely to run into trouble using 10 MHz out of a Z3805 as reference signal. Crazy stuff…. Bob On Nov 18, 2012, at 4:35 PM, Volker Esper ail...@t-online.de wrote: ...A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter... Yes, I wondered what the histogram would show when using the 2-maxima-Z3805 signal as a reference for the SR620 counter. Would the PLL filter it or would I get a mixer-like result with two maxima in the histogram? I applied the Z3805 to the reference input and the SMX signal generator to the counter input. The histogram looked equal to that I got when using the internal oscillator of the counter for reference. That obviously confirms Bob's statement. Volker Am 18.11.2012 21:23, schrieb Bob Camp: Hi This is one of those interesting areas where a broadband measurement (like a counter) and a narrowband measurement (like a DMTD) will give very different results. The counter will see the sub-harmonic, and call it jitter. It can show up in an ADEV calculation. A DMTD will ignore the sub-harmonic, and show no added jitter. With a DMTD, the ADEV will look fine. A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter. Which one's right / does it matter - as always, that depends on what you are trying to do with the signal. Bob On Nov 18, 2012, at 1:26 PM, Volker Esperail...@t-online.de wrote: @Azelio: Yes, (like Bob told) it's the phase lock, that locks the two maxima. Actually the counter is able to look between the 60ps spaced towers, have a look at the pictures in the first mail of this thread. However, there is a smallest time value the counter can determine, but it is much smaller than 60ps. Volker Am 18.11.2012 17:11, schrieb Bob Camp: Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Borianiazelio.bori...@screen.it wrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Campli...@rtty.us wrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Campli...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns -100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the
Re: [time-nuts] Z3805 two frequency maxima
As far as I can see the PLL loop filter (SR620) has a corner frequency of about 33Hz. My HP counter 5385A has simply a switch to toggle between the external source and the internal osc. Am 18.11.2012 22:45, schrieb Bob Camp: Hi Most modern counters have an internal oscillator that they lock up to the external reference. The PLL bandwidth is (hopefully) chosen to optimize the noise contribution of the internal oscillator (quiet broad band) and the external reference (quiet close in). It will reject anything MHz away from the reference. Even if the reference signal is used directly, it would only be a problem if divided by an odd number. Even number division will wipe out the jitter. The most likely gate times are all a power of 10, so the division should always be even in a counter. Bottom line - you are unlikely to run into trouble using 10 MHz out of a Z3805 as reference signal. Crazy stuff…. Bob On Nov 18, 2012, at 4:35 PM, Volker Esperail...@t-online.de wrote: ...A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter... Yes, I wondered what the histogram would show when using the 2-maxima-Z3805 signal as a reference for the SR620 counter. Would the PLL filter it or would I get a mixer-like result with two maxima in the histogram? I applied the Z3805 to the reference input and the SMX signal generator to the counter input. The histogram looked equal to that I got when using the internal oscillator of the counter for reference. That obviously confirms Bob's statement. Volker Am 18.11.2012 21:23, schrieb Bob Camp: Hi This is one of those interesting areas where a broadband measurement (like a counter) and a narrowband measurement (like a DMTD) will give very different results. The counter will see the sub-harmonic, and call it jitter. It can show up in an ADEV calculation. A DMTD will ignore the sub-harmonic, and show no added jitter. With a DMTD, the ADEV will look fine. A PLL multiplier will (likely) also ignore the sub-harmonic, the jitter will not show up if you use the 10 MHz as a counter timebase in a HP counter. Which one's right / does it matter - as always, that depends on what you are trying to do with the signal. Bob On Nov 18, 2012, at 1:26 PM, Volker Esperail...@t-online.de wrote: @Azelio: Yes, (like Bob told) it's the phase lock, that locks the two maxima. Actually the counter is able to look between the 60ps spaced towers, have a look at the pictures in the first mail of this thread. However, there is a smallest time value the counter can determine, but it is much smaller than 60ps. Volker Am 18.11.2012 17:11, schrieb Bob Camp: Hi The 5 MHz and 10 MHz are locked together by the multiplier. Their relative phase is fixed. The 5 MHz component is not free to wander independently relative to the 10 MHz. Since it's a doubler, you get a two peak plot. If it was a X3 you would get three peaks. It really only makes sense if you look at it on a scope. Of course at 60 ps, it would have to be a mighty good scope. Much easier to see when the sub-harmonic is a bit stronger... Bob On Nov 18, 2012, at 9:53 AM, Azelio Borianiazelio.bori...@screen.itwrote: Interesting this, but why exactly 60pS? I would expect also something in-between. That is, to have the 5MHz energy 64dB below, in my opinion nothing prevents to have the edge to wander not only at 60pS but continuously between 0 and 60pS. Maybe the SR620, being a 25pS resolution counter, simply doesn't see what's going on in-between and the resulting histogram looks that way. On Sun, Nov 18, 2012 at 3:51 AM, Bob Campli...@rtty.uswrote: Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Campli...@rtty.uswrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esperail...@t-online.dewrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little
Re: [time-nuts] Z3805 two frequency maxima
Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esper ail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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] Z3805 two frequency maxima
So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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] Z3805 two frequency maxima
Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esper ail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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] Z3805 two frequency maxima
I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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] Z3805 two frequency maxima
Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esper ail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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] Z3805 two frequency maxima
Hi A little more detail: What's going on is more clear if you trigger a scope on the positive edge of the 5 MHz and look at the 10 MHz. With an ideal multiplier, both the positive and negative edges of the 5 MHz should line up exactly with a positive edge of the 10 MHz. In reality, negative edge (the one not triggered) does not quite line up. It's a bit ahead (or behind) the ideal location. Since it's a small angle, the delta in phase and delta in amplitude both follow the same basic law. Bob On Nov 17, 2012, at 9:36 PM, Bob Camp li...@rtty.us wrote: Hi Just good old Fourier series. Bob On Nov 17, 2012, at 9:12 PM, Volker Esper ail...@t-online.de wrote: I'm impressed - but what law is behind this? Am 17.11.2012 21:26, schrieb Bob Camp: Hi 60 db isn't to bad a number. More or less: 100 ns - 100 ps is 1000:1. 20 log of that is 60 db. 100 ps to 60 ps is about 4.4 db. That would sum up to -64.4 dbc. The main gotcha is that you *might* also have some 15 MHz (and higher) energy in the signal as well. Also phase gets into the calculation. Still, pretty close. Bob On Nov 17, 2012, at 12:50 PM, Volker Esperail...@t-online.de wrote: So let's have a look into the machine... and what do we see? There's a nice little Symmetrcom oven, with the sign reading 5.000 MHz - bingo! May be there's a time saving way to determine the energie of the sub harmonic: using my spectrum analyzer. It tells me, that there's a 5 MHz subharmonic at the level of -62dBc. How would you have calculated the energy? What would be your ansatz? Thanks so far Volker Am 17.11.2012 17:55, schrieb Bob Camp: Hi That's what you get if you have sub harmonic energy in the output of your OCXO. I'd bet you a warm glass of beer that you have a 5 MHz / doubled to 10 MHz MTI OCXO in your Z3805. If you have a lot of time on your hands, you can calculate the likely level of the energy from the amount of jitter (spacing between the two peaks) you get. Bob On Nov 17, 2012, at 11:41 AM, Volker Esperail...@t-online.de wrote: Hi, while playing with my recently aquired TIC (SR620) and measuring the period time of some oscillators I discovered something I hadn't expect at all: The output of my GPSDO (Z3805) writes two maxima in the period histogram (at a spacing of 60ps). I didn't believe that result and assumed an inherent error in my measuring setup or the counter itself. So I plugged another oscillator, the reference TCXO of my signal generator (RS SMX), and that result made me happy and uneasy at once: The TCXO hat only one maximum. I havn't calculated the ADEV curve, yet. See pictures. Why does my GPSDO produce such a weird result? Cheers Volker - DF9PL DSCF1437_bbb.jpgDSCF1439_bbb.jpg___ 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. ___ 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. ___ 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.
