Hi I would pretty much ignore any 60 / 120 / 180 Hz spurs in a US phase noise plot. The same thing would be true of 50 / 100 / 150 Hz spurs from a country that uses 50 Hz power. Unless everything is running in the middle of a corn field on batteries, there is no way to be *sure* that they are not part of the measurement setup.
If you happen to be on a circuit with heavy rotary machinery, you can see artifacts at 1/2 or 1/3 or 1/4 the power line frequency. I doubt that in that case the bearings on the equipment are going to last very long. They rarely are strong enough to bother a phase noise plot, but I have had it happen. Bob > On Nov 17, 2014, at 3:01 PM, Tom Miller <[email protected]> wrote: > > That first spike falls right at 60 Hz. I wonder if your test setup is picking > up some hum? > > Tom > > ----- Original Message ----- From: "S. Jackson via time-nuts" > <[email protected]> > To: <[email protected]>; <[email protected]> > Sent: Monday, November 17, 2014 2:26 PM > Subject: Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, > Z3810A,Z3811A, Z3812... > > > Hi Bob, > > yes, the 10MHz plot is rotten, no doubt. The 15MHz plot is quite good till > about 40Hz offset, then it becomes pretty rotten too. > > Here is one of my 58503A units (using the 10811 OCXO) as a comparison.. > measured against our DROR-IIA (this plot was actually done to show the > DROR-IIA PN, but since that unit actually has less noise and spurs than the > 58503A we can simply use it as the reference for this purpose). > > The good news is that getting the close-in phase noise to be good is very > hard to do and the unit delivers that out-of-the box already. Filtering out > the noise and spurs above 40Hz offset is pretty easy to do. It should be > fairly straight forward to cobble up a small PN filter for those units to get > rid of the noise and spurs above 40Hz offset. > > bye, > Said > > > In a message dated 11/17/2014 09:31:46 Pacific Standard Time, [email protected] > writes: > > Hi > > Here’s the phase noise on the 15 MHz. There are a few spurs, and an very > real hump out at the likely frequency of the Lucent switcher. The 15 MHz is > pretty clean compared to most /all of the other units I’ve seen on the > surplus market. > > I would not multiply this up to 40 GHz with a broadband multiplier. I > would be quite happy to run it into a PLL with a rational bandwidth. You will > beat the noise on the output with a fairly simple VHF VCXO past 100 Hz. No > reason to have a bandwidth outside the 20 to 80 Hz range. > > Math: > > 15 MHz to 150 MHz -> 20 log (N) -> 20 db. > > -140 dbc / Hz shown below at 100 Hz offset -> -120 dbc/Hz > > You can get numbers better than -120 dbc/Hz at 100 Hz offset out of a > number of pretty simple VHF VCXO circuits. Bert has one that seems to work > fine > for him. > > Bob > > > > > > -------------------------------------------------------------------------------- > > >> _______________________________________________ >> 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.
