Hi There are indeed “issues” with converting the reference to 1 pps. If you use a modern D flip flop at the output of the divider these issues are quite small. There are similar issues with coax cable, buffer amplifiers, and even the input on the counter. Eliminating / characterizing them is “fun”. Even the counter’s conversion of the reference to 1 KHz is also likely to have issues ….
Bob > On Mar 3, 2022, at 9:16 AM, Mete Balci <meteba...@gmail.com> wrote: > > Thanks Bob. I was also thinking something similar but on the SRS pdf I > mentioned (high res. freq. measurements), it also mentions Allan variance > and as an example the noise floor data is collected also with a sample size > of 1000. The setup is not like I mentioned but normal ChA/start ChB/stop > driven from the same source but with REF OUT as EXT trigger and I guess > because REF OUT is 1kHz, sample size is set to 1000 to get 1 sample per > second. > > I also wonder if there is no effect of converting 10MHz to 1 PPS in order > to measure Allan variance (when the reference is GPSDO PPS). Isnt it at > least conceptually the same thing if not exactly the same (that it > eliminates the variations in a 10MHz signal) ? > > Mete > > From the pdf mentioned: "(This data was collected by connecting one 10MHz > out of an FS725 to the SR620 reference > input. A second 10MHz output from the FS725 went to the input of an RF > splitter (Minicircuits > 15542 Splitter ZSCJ-2-1). The two splitter outputs were connected with > identical 3 inch BNC > cables to channel A and B of the SR620. The 1kHz REF out of the SR620 was > connected to the > EXT input of the SR620. The SR620 was set up for time interval > measurements, starting on > channel A using EXT +/-time gate/arm, with a sample size of 1000. 57600 > 1-second > measurements were collected, starting on 3/2/04 4:15pm The modified root > Allan variance was > computed to give the graph shown above.)" > > On Thu, Mar 3, 2022 at 2:17 PM Bob kb8tq <kb...@n1k.org> wrote: > >> Hi >> >> The main disadvantage (if you are after ADEV) is the pre-processing >> that takes out the noise you are trying to measure. Getting the repeat >> rate so that you actually got samples once a second (after all the overhead >> and processing) would be a challenge. >> >> Bob >> >>> On Mar 3, 2022, at 2:28 AM, Mete Balci <meteba...@gmail.com> wrote: >>> >>> Hello, >>> >>> Is there any disadvantage of using SR620 with TimeLab as described in >> high >>> res freq. measurement document of SRS ? >>> >>> 1) DUT (10MHz) is connected to External Clock In >>> 2) REF OUT (1kHz) is connected to ChA >>> 3) GPS receiver PPS output configured as 1kHz and is connected to ChB. >>> 4) Sample size 1000 >>> >>> Can this value be used in the same sense as in a (normal) single >>> measurement (Ch A: GPS PPS vs. Ch B: DUT output converted to PPS) ? >>> >>> If not, is there still a benefit of maybe converting REF OUT (not DUT) to >>> PPS and using it still like the above configuration but with sample size >> 1 ? >>> >>> Mete >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >> send an email to time-nuts-le...@lists.febo.com >>> To unsubscribe, go to and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >> an email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.