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 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 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 (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 -- 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 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.