Hi None of the GPSDO’s out there are great for multiplying direct to microwaves. It’s not so much the phase noise as all the spurs (though phase noise does vary a bit). For an instrument frequency source, they *assume* the input will be dirty and clean it up inside the device. So again, pretty much any of the gizmos likely will do ok.
As you go to longer gate times than one second, the accuracy changes a bit on most GPSDO’s. Just how much is a “that depends” sort of thing. If you get out around 200 seconds it’s a good bet that your 0.1 ppb is more like 0.01 ppb. Bob > On Feb 12, 2019, at 4:30 PM, Jeff Blaine <[email protected]> wrote: > > Hi Bob, > > Thanks for your comments. The highest precision thing in my lab is a 5338a > and that's only if I set the gate time to something really long so that it > renders a full 12 digits of info. Other than a "I wanna be a time nut so > let's see what it will do" - I never need anything near that in reality. So > let's say what I want to be able to see is 0.1 Hz resolution on a 50 Mhz test > frequency. So your 0.1 ppb is a good observation. > > Do you have any thoughts on PN of the 3? Ive not found plots yet for the > Lucent boxes but know the NT I have is middling on a good day. > > 73/jeff/ac0c > alpha-charlie-zero-charlie > www.ac0c.com > > On 12-Feb-19 9:17 AM, Bob kb8tq wrote: >> Hi >> >> Pretty much all of these big old telecom beasts are “good enough” for >> “typical use”. The gotcha >> is that both of those terms are very much lacking in precision. Since this >> is a precision sort of >> thing, that may not be ideal :) >> >> If 0.1 ppb is good enough for what you are doing, then they all should be >> fine. If you need 0.001 ppb, >> then none of them are likely to do what you need to do. Between those two >> limits, things like antennas, >> survey locations, lab temperature, and the accuracy definition you use all >> get into play. Yes, you *can* >> have some unusual cases (your lab goes from -20 to +90 (F of course …) on a >> daily basis. For anything >> reasonable, the limits above are pretty good. >> >> If time rather than frequency *is* the goal, then one of these GPSDO's is >> not really what you want. >> The time pulse output from a good GPS module is likely closer to UTC (after >> some math) than the >> output of the GPSDO. >> >> Bob >> >>> On Feb 11, 2019, at 9:57 PM, Jeff Blaine <[email protected]> wrote: >>> >>> I have these 3 systems operational here and wonder what is the "best" of >>> the sources? >>> >>> The local use for the reference is as a time base for test equipment. >>> Nothing hyper critical in the way of end-use requirements - but after >>> running the NT GPSDO for a few years and watching the Lucent box collect >>> dust, I wonder if I have got that backward? >>> >>> The lucent has a 10 Mhz output on the front panel of the RB but the XO >>> would need a tiny bit of modification to have 10 Mhz instead of the current >>> 15 Mhz. >>> >>> There is a lot of data on http://leapsecond.com/u/sims/gpsdo17/ but I don't >>> see the RFTG XO on there - which I assume is due to it's native 15 Mhz Fo >>> vs. 10 Mhz for the rest of the field. >>> >>> Appreciate any advice you may have for a (very) novice 'nut. >>> >>> 73/jeff/ac0c >>> alpha-charlie-zero-charlie >>> www.ac0c.com >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
