Hi Bottom line:
This is why you often see spur specs stated with a lower frequency limit (like 250Hz) or an exclusion for line related spurs. One really fun one not (yet) mentioned: All of those motors in the building are rotating at line frequency. You don’t just have an electromagnetic field. You can have an acoustic / vibration field as well. Probably not a big deal, but it’s there …. Bob > On Jul 12, 2016, at 6:45 PM, Alan Melia <[email protected]> wrote: > > Bob the VLF guys in Europe can receive the 60Hz signal over here! so you > probably needed a test site on the far side of the Moon :-)) > Alan > G3NYK > > ----- Original Message ----- From: "Bob Camp" <[email protected]> > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Sent: Tuesday, July 12, 2016 10:53 PM > Subject: Re: [time-nuts] OXCO Spurious Output at Line Frequencies > > >> Hi >> >> The “practical” solution often is to ship it to an office of the same >> company that happens >> to have 60 Hz power. The spur moves to 60 / 120 / 180 and they move on with >> their >> evaluation. >> >> I have also played the “let’s do it with batteries" approach. Screen rooms >> were of little benefit. >> Simply running test gear on batteries did not do the job. Ultimately we >> wound up in the >> middle of an Illinois corn field with a bunch of gear modified to run purely >> on batteries. The >> spur did go down, but it never fully went away. It’s been 40 years since >> that adventure so I >> really could not say just how far down we got it …. >> >> Anything past -120 db at line frequency is in the “don’t bother” category. >> >> Bob >> >> >>> On Jul 12, 2016, at 6:44 AM, Martyn Smith <[email protected]> wrote: >>> >>> Hello, >>> >>> I have a customer who is measuring the phase noise of my 10 MHz ultra-low >>> phase noise frequency standard. >>> >>> He is seeing spurious signals at line frequencies (50 and 100 Hz as we are >>> in Europe) at a level around -130 dBc. >>> >>> My opinion is that it's impossible to get much better than that. Even >>> running on batteries make little difference, since the equipment is in a >>> test rack with AC signals everywhere. >>> >>> Even the £50k R&S test set he is using only quotes a spurious spec of -90 >>> dBc. >>> >>> What experience does anyone have here? >>> >>> Best Regards >>> >>> Martyn >>> >>> >>> _______________________________________________ >>> 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.
