Re: [time-nuts] Termination talk
Simon, ...which prefers to remain anonymous... sounds as if it were a group of criminals or so. Best regards Ulrich Bangert > -Ursprüngliche Nachricht- > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] Im Auftrag von M. Simon > Gesendet: Mittwoch, 28. November 2012 23:53 > An: time-nuts@febo.com > Betreff: [time-nuts] Termination talk > > > I was going to post an anecdote about termination to the list > and then thought that the piece would make a great column. It > did. My magazine featured it in one of its daily mailings. > > If you want to check it out: > http://www.ecnmag.com/blogs/2012/11/long-lines-pcb > > Simon > > > Engineering is the art of making what you want from what you > can get at a profit. ___ > 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 incident
Volker, please note that much of the clear text in the status information is generated by Z38XX itself to make it easier to read. > 2012-11-28 10:01:40: The last Smartclock Status is undefined > 2012-11-28 10:01:40: Starting with status LOCK for example means that Z38XX is unaware of the receiver status and assumes that the status is locked. 73s de Ulli, DF6JB > -Ursprüngliche Nachricht- > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] Im Auftrag von Volker Esper > Gesendet: Mittwoch, 28. November 2012 22:24 > An: Discussion of precise time and frequency measurement > Betreff: [time-nuts] Z3805 incident > > > When looking at the PPS TI vs. time curve today I felt kind > of appalled > - a big incident peak (not an outlier) on the curve! See picture. > > What happened to my Z3805? Any idea? > > No entry in the error log, the staus log says > > 2012-11-28 10:01:30: The Smartclock Status has changed to LOC > 2012-11-28 10:01:40: The last Smartclock Status is undefined > 2012-11-28 10:01:40: Starting with status LOCK > > Thanks > > 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] Z3805 incident
Volker, This is a classic crystal jump. The crystal changed its frequency magically from one second to the next and the software compensated for it You can nicely see the time constant of the loop.. Bye Said Sent From iPhone On Nov 28, 2012, at 13:24, Volker Esper wrote: > When looking at the PPS TI vs. time curve today I felt kind of appalled - a > big incident peak (not an outlier) on the curve! See picture. > > What happened to my Z3805? Any idea? > > No entry in the error log, the staus log says > > 2012-11-28 10:01:30: The Smartclock Status has changed to LOC > 2012-11-28 10:01:40: The last Smartclock Status is undefined > 2012-11-28 10:01:40: Starting with status LOCK > > Thanks > > 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] Poor termination effects?
I am pretty sure you are right on the mark there. I made a habit of listening to the tone modulated seismic transmitters in southern California and with experience, they definitely sounded like you would expect if a source was reflecting off of various impedance discontinuities in the crust which of course the hilly southern California and San Francisco areas have. On Wed, 28 Nov 2012 16:08:57 -0800, Rex wrote: >I live in the San Francisco bay area. You may recall that back in 1989 >we had a big earthquake that did a lot of damage. > >The epicenter was near Loma Prieta, which became the name for this >earthquake. That is about 60 miles south of San Francisco, yet a lot of >the bad damage occurred there, at the tip of the peninsula. My twisted >engineer's mind caused me to think that such a locus of damage so far >from the source may have been due to a poor termination of the peninsula >into the ocean/bay. ___ 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] Poor termination effects?
I live in the San Francisco bay area. You may recall that back in 1989 we had a big earthquake that did a lot of damage. The epicenter was near Loma Prieta, which became the name for this earthquake. That is about 60 miles south of San Francisco, yet a lot of the bad damage occurred there, at the tip of the peninsula. My twisted engineer's mind caused me to think that such a locus of damage so far from the source may have been due to a poor termination of the peninsula into the ocean/bay. ___ 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 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 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 Camp 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,
[time-nuts] Termination talk
I was going to post an anecdote about termination to the list and then thought that the piece would make a great column. It did. My magazine featured it in one of its daily mailings. If you want to check it out: http://www.ecnmag.com/blogs/2012/11/long-lines-pcb Simon Engineering is the art of making what you want from what you can get at a profit. ___ 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] SR620 is sold!
Thanks for the interest the SR620 is sold. Corby Woman is 53 But Looks 25 Mom reveals 1 simple wrinkle trick that has angered doctors... http://thirdpartyoffers.juno.com/TGL3141/50b68d00e6768d0043bast03duc ___ 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 incident
Not Rb but OCXO vs GPS... Am 28.11.2012 22:47, schrieb Azelio Boriani: Ops, I missed the EFC value... On Wed, Nov 28, 2012 at 10:43 PM, Azelio Boriani wrote: The reference is still the Rb? Then how you can tell which of the two is doing that... On Wed, Nov 28, 2012 at 10:24 PM, Volker Esper wrote: When looking at the PPS TI vs. time curve today I felt kind of appalled - a big incident peak (not an outlier) on the curve! See picture. What happened to my Z3805? Any idea? No entry in the error log, the staus log says 2012-11-28 10:01:30: The Smartclock Status has changed to LOC 2012-11-28 10:01:40: The last Smartclock Status is undefined 2012-11-28 10:01:40: Starting with status LOCK Thanks 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.
Re: [time-nuts] Z3805 incident
Ops, I missed the EFC value... On Wed, Nov 28, 2012 at 10:43 PM, Azelio Boriani wrote: > The reference is still the Rb? Then how you can tell which of the two is > doing that... > > On Wed, Nov 28, 2012 at 10:24 PM, Volker Esper wrote: > >> When looking at the PPS TI vs. time curve today I felt kind of appalled - >> a big incident peak (not an outlier) on the curve! See picture. >> >> What happened to my Z3805? Any idea? >> >> No entry in the error log, the staus log says >> >> 2012-11-28 10:01:30: The Smartclock Status has changed to LOC >> 2012-11-28 10:01:40: The last Smartclock Status is undefined >> 2012-11-28 10:01:40: Starting with status LOCK >> >> Thanks >> >> 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] Z3805 incident
The reference is still the Rb? Then how you can tell which of the two is doing that... On Wed, Nov 28, 2012 at 10:24 PM, Volker Esper wrote: > When looking at the PPS TI vs. time curve today I felt kind of appalled - > a big incident peak (not an outlier) on the curve! See picture. > > What happened to my Z3805? Any idea? > > No entry in the error log, the staus log says > > 2012-11-28 10:01:30: The Smartclock Status has changed to LOC > 2012-11-28 10:01:40: The last Smartclock Status is undefined > 2012-11-28 10:01:40: Starting with status LOCK > > Thanks > > 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] Z3805 incident
When looking at the PPS TI vs. time curve today I felt kind of appalled - a big incident peak (not an outlier) on the curve! See picture. What happened to my Z3805? Any idea? No entry in the error log, the staus log says 2012-11-28 10:01:30: The Smartclock Status has changed to LOC 2012-11-28 10:01:40: The last Smartclock Status is undefined 2012-11-28 10:01:40: Starting with status LOCK Thanks 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] Stanford Research SR620
Hi Everyone, I'm selling my SR620 and thought to offer it here first before the eBay. The only problem I know about is an error 3 on power up. This equates to the battery backed up RAM not holding its load. The battery checks good so it's probably the RAM chip itself. You can then select a function and the counter will function fine. (It loads the factory defaults from ROM) I have been using it for over a year this way in the time interval mode with no problems. I can email a set of pictures to intrerested parties. It has an SC10 oscillator inside. (I plotted its short term stability and can provide it with the PIX.) Includes an original factory manual with schematics. I'm asking $975.00 + shipping for it. Questions welcome! Thanks, Corby Dawson cdel...@juno.com Woman is 53 But Looks 25 Mom reveals 1 simple wrinkle trick that has angered doctors... http://thirdpartyoffers.juno.com/TGL3141/50b66e51b19b76e51555dst02duc ___ 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] Best phase detector / mixer for 100MHz?
Support HpW-Works.com wrote: Hi Bruce, The equivalent phase noise (measured in dBc/Hz) is essentially independent of the sample size. The dBc/Hz normalization is based on this (also the sample rate). While the sample rate& sample size = FFT Bin size (resolution or filter band width) is used to get the required correction factor of the spectrum to get the dBc / (1Hz) Y scaling back. So increasing the sample size isnt particularly useful for reducing the phase noise floor. By theory, yes... but we use a sound card with a lot of flicker noise on the lower end, also we have the 10...20Hz low freq. cutoff due the usage of a servo / single 5V power. Also the raising noise below 100Hz (ADC serve& noise on the ADC power / input circuit) limits the performance. In my simple test increase of the sample size reduced the noise floor in better way than just using sample size with 1-2K and large averaging cycles. Keep in mind, Bin resolution is sample rate / sample size: Example: - 32khz / 32678 = about 1Hz - 32khz / 1024 = about 31 Hz Your sample sizes are far too small to be particularly useful in measuring phase noise down to offsets of 1-10Hz or so, Phase noise is highly coloured at such offsets necessitating the use of bin sizes substantially smaller than the lowest offset frequency of interest. However decreasing the bin size beyond a small fraction of the lowest frequency of interest is counter productive in that one forgoes the effect of averaging to reduce the variance of the noise signal power within each bin. There is a NIST paper on the effect of equivalent filter bandwidth on the accuracy of coloured noise measurements. Indeed one can break the frequency range into a set of bands, the higher frequency bands having larger bin sizes and greater averaging and hence (lower bin noise signal power variance) than the lower frequency bands. However for the purposes of spur identification using as small a bin size as possible can be useful. However with a sound card plus a mixer a somewhat lower number of samples should suffice since there is no carrier. Ideally the input circuit& ADC of the 3562A would be nice but with much larger RAM buffer and ASIO interface O:) Hanspeter Using a high end PC should allow real time signal processing with 200ksps or greater, this is certainly the case for some external USB instruments. Bruce ___ 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] Best phase detector / mixer for 100MHz?
Hi Bruce, >> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >> the sample size. The dBc/Hz normalization is based on this (also the sample rate). While the sample rate & sample size = FFT Bin size (resolution or filter band width) is used to get the required correction factor of the spectrum to get the dBc / (1Hz) Y scaling back. >> So increasing the sample size isnt particularly useful for reducing the phase >> noise floor. By theory, yes... but we use a sound card with a lot of flicker noise on the lower end, also we have the 10...20Hz low freq. cutoff due the usage of a servo / single 5V power. Also the raising noise below 100Hz (ADC serve & noise on the ADC power / input circuit) limits the performance. In my simple test increase of the sample size reduced the noise floor in better way than just using sample size with 1-2K and large averaging cycles. Keep in mind, Bin resolution is sample rate / sample size: Example: - 32khz / 32678 = about 1Hz - 32khz / 1024 = about 31 Hz >> However with a sound card plus a mixer a somewhat lower number of samples >> should suffice since there is no carrier. Ideally the input circuit & ADC of the 3562A would be nice but with much larger RAM buffer and ASIO interface O:) Hanspeter >> -Original Message- >> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >> Behalf >> Of Bruce Griffiths >> Sent: Dienstag, 27. November 2012 12:31 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Best phase detector / mixer for 100MHz? >> >> Support HpW-Works.com wrote: >> > Bruce, >> > >> > >> >>> There's no evidence of a cross power spectrum function in this suite. >> >>> One needs to be able to average at least 10,000 cross power spectra >> >>> for some applications. >> >>> >> > In the PSD (power density)& PSP (power spectrum) there are cross >> > power and cross power complex average implemented (selectable using the >> spectrum channel mixer)! >> > Additional to this you may apply / add averaging of the resulting >> > spectrum or use additional peak hold. >> > >> > Average of 10'000 cross points is a large count and often seen on 1-4k >> sample size. >> > Better in my opinion is to use a higher sample size 32k-64k and then >> > less averaging is required. >> > >> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >> the sample size. >> So increasing the sample size isnt particularly useful for reducing the phase >> noise floor. >> The increased frequency resolution achieved by increasing the sample size is >> only useful for measuring spurs. >> In the direct digital method of measuring phase noise a few terasamples (a >> few >> gigasamples at baseband) need to be processed to achieve a sufficiently low >> instrument noise floor. >> However with a sound card plus a mixer a somewhat lower number of samples >> should suffice since there is no carrier. >> > Just download the evaluation version with fully feature set. >> > >> > HpW >> > >> > >> > >> Bruce >> >> >> ___ >> 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
...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 Camp 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 Esper 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 Esper 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.
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.
