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.
