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 <[email protected]> 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 Esper<[email protected]> 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 Esper<[email protected]> 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 Boriani<[email protected]> >>>>>> 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<[email protected]> 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<[email protected]> wrote: >>>>>>>> >>>>>>>>> Hi >>>>>>>>> >>>>>>>>> Just good old Fourier series. >>>>>>>>> >>>>>>>>> Bob >>>>>>>>> >>>>>>>>> On Nov 17, 2012, at 9:12 PM, Volker Esper<[email protected]> >>>>>>>>> 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<[email protected]> >>>>>>>>>>> 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 Esper<[email protected]> >>>>>>>> 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 (R&S 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.jpg><DSCF1439_bbb.jpg>_______________________________________________ >>>>>>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>>>>>> and follow the instructions there. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>>>>> and follow the instructions there. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> _______________________________________________ >>>>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>>>> and follow the instructions there. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> _______________________________________________ >>>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>>> and follow the instructions there. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> _______________________________________________ >>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>> and follow the instructions there. >>>>>>>>> >>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>> and follow the instructions there. >>>>>>>> >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>> and follow the instructions there. >>>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- [email protected] >>>>>>> To unsubscribe, go to >>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- [email protected] >>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
