Not to junk up the mailboxes, but I have the multiple GPSDOs. Don’t know what you mean by L1/L2 GPSDO, is that a quality statement?
Also, what would the next step cost me for a Cesium Beam? Roughly? And what order of magnitude improvement would that be for the cost? Have to do a cost/benefit analysis for the wife... > On Nov 20, 2017, at 4:09 PM, Bob kb8tq <kb...@n1k.org> wrote: > > Hi > > Ummm ….. errrr ….. multiple GPSDO’s …. L1/L2 GPSDO(s) …. Cs standard (s) … > Maser(s) …. Ensembles of all of the above …. > > There’s *lots* of steps still to take …. > > Bob > >> On Nov 20, 2017, at 6:31 PM, Jerry Hancock <je...@hanler.com> wrote: >> >> One step at a time. >> >> 2yrs ago when the time-bug hit, I had a crystal oscillator. 6 months later, >> DOCXO then GPSDO then Rubidium soon to be with GPSDO and there aren’t too >> many steps after that… >> >> I also gave my brother the bug the other day… >> >> >> >>> On Nov 20, 2017, at 3:05 PM, Bob kb8tq <kb...@n1k.org> wrote: >>> >>> Hi >>> >>> It’s very much a “somewhere near that number” sort of thing with an Rb. The >>> “thing” you are looking at is quantum mechanical in nature. Unfortunately >>> that >>> by its self does not make it perfect. A beam tube (as opposed to a gas >>> cell) >>> isolates things better. >>> >>> A 5061 is a beam tube device. A 5065 is gas cell based. It is very >>> important to note that >>> accuracy and stability are two different things …. The beam tube is more >>> accurate. >>> The gas cell is more stable (over some range of tau). >>> >>> A normal Rb standard has a bit of this and that in the bulb. These other >>> gasses >>> help in various ways. They each also add a bit of “pull” to the frequency >>> one way >>> or the other. They get you away from your “magic number” but the benefits >>> they >>> deliver are worth the trouble. The exact gas mix gets into the “secret >>> sauce” of >>> the Rb manufacturer. They each optimize things a bit differently. The walls >>> of the bulb get into the act …. >>> >>> Beam standards are actually a bit old these days. The more modern approach >>> would be a fountain (toss the ion straight up and let it fall back to you). >>> An even >>> more modern approach would be a trapped ion standard. The amount of money >>> involved goes up dramatically with each of those steps. You get rid of this >>> and >>> that subtle effect with each improvement. Accuracy gets better and better. >>> >>> Lots of choices !!! >>> >>> Bob >>> >>>> On Nov 20, 2017, at 3:28 PM, Jerry Hancock <je...@hanler.com> wrote: >>>> >>>> Bob, I was referring to the rubidium standard of 6834682610.904 Hz. For >>>> some reason I thought it was closer to 9Ghz. >>>> >>>> I assume then rubidium standards oscillate (if that is the correct term) >>>> somewhere around that number but not exact or is it in the detection where >>>> things fall down? >>>> >>>> >>>> >>>>> On Nov 20, 2017, at 11:40 AM, Bob kb8tq <kb...@n1k.org> wrote: >>>>> >>>>> Hi >>>>> >>>>> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what >>>>> have a direct relation. >>>>> Even then, the qualifier is “under standard conditions”. They are >>>>> sensitive to magnetic field. Rb’s >>>>> also are sensitive to magnetic field. Both can be tuned by varying the >>>>> field. In the case of an Rb >>>>> that also takes care of a multitude of other issues. >>>>> >>>>> In the case of Rb, there is a distribution of cells coming out of the >>>>> manufacturing process. Some >>>>> are pretty close to the “right” frequency. Others are way off (as in >>>>> 100’s of KHz or more). All of them >>>>> are capable of meeting the required specs. DDS techniques allow those >>>>> cells to be used in a >>>>> production part. That increases the yield and thus drops the production >>>>> cost. >>>>> >>>>> Since you now magically have a DDS in the Rb, you can do all sorts of >>>>> interesting things. If you >>>>> suddenly need a 9.99900 MHz standard …. here it is … If you need to do >>>>> temperature compensation >>>>> via a lookup table … it just takes a bit of testing and some code to make >>>>> it happen. Indeed, the DDS >>>>> does also give you some issues. Without some sort of cleanup oscillator, >>>>> you will have spurs and >>>>> phase noise on the output. >>>>> >>>>> Lots of fun …. >>>>> >>>>> Bob >>>>> >>>>> >>>>>> On Nov 20, 2017, at 1:34 PM, Jerry Hancock <je...@hanler.com> wrote: >>>>>> >>>>>> I know this is going to sound dumb as I know many GPSDOs had rubidium >>>>>> oscillators in them. I can see why, in that during holdover, they would >>>>>> tend to be more stable vs others, but given that there is a direct >>>>>> mathematical relationship between the rubidium frequency and potentially >>>>>> the 10Mhz desired output frequency, why do they have to be disciplined >>>>>> or better yet, what advantage does it bring? Also, I can see how you >>>>>> discipline a DOCXO with the external voltage, how do you discipline a >>>>>> rubidium? Pulse stretching? >>>>>> >>>>>> I guess I don’t understand how the technology works, but it seems like >>>>>> an RF signal is swept that would be used to detect a dip at a pretty >>>>>> well defined frequency. This dip can be used to discipline the >>>>>> oscillator to something like 9Ghz or a factor of what, 900+ times better >>>>>> than 10Mhz. So wouldn’t that be able to get your desired 10Mhz to >>>>>> 10,000,000.001 or pretty much my level of measurement? Or does is the >>>>>> dip not quite that precise? If you can point me to a write-up on this >>>>>> I’ll go away. >>>>>> >>>>>> Thanks to Gilbert for providing me with at least one rubidium oscillator >>>>>> that is working out of 5 though 2 others seems to stay locked for a few >>>>>> hours during my testing. >>>>>> >>>>>> Jerry >>>>>> _______________________________________________ >>>>>> 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.
