Here's an app note from NASA on what they did for controlling, or filtering, phase noise, and it can get complicated.
http://ipnpr.jpl.nasa.gov/progress_report2/XII/XIIK.PDF Best, Will *********** REPLY SEPARATOR *********** On 7/12/2011 at 1:44 AM WB6BNQ wrote: >Hi David, > >Just to clear the AIR, all Rubidium frequency standards have a crystal oscillator as >the primary signal source within the Rubidium device. The Rubidium portion of the >standard is just a very high Q filter whose properties can be controlled such that >it's filter's center frequency has extremely small drift. That small drift factor is, >typically, way less then the resulting factors that control drift in a Quartz >resonator. > >In order to gain the properties of the Rubidium's longer term stability and the short >term noise properties of a very good Quartz oscillator you would need both items. You >select a very good Quartz device and phase lock it to a really good Rubidium (with its >own Quartz oscillator). You would adjust the loop constants to correct at a very slow >pace consistent with the quality of the very good Quartz oscillator. > >To get to the next level (connection to the Nation's reference), you would discipline >the Rubidium against a GPS device with an even slower loop. So, in the end you have >two separate loops with three separate devices. This is not your "Nickel & Dime >store" plug-and-play set up. It would have to be set up with care and some >experimentation to get it right. > >For a reference on the basic process, you should read the QST article on Brooke >Shera's GPS disciplined oscillator system. Contained within it is a description of >the loop process I referred to above. To utilize his method would require upgrading >his circuit design (some parts not available any longer) and some software upgrading >as well to account for those changes. > >To obtain the QST article go to Shera's web site at http://www.rt66.com/~shera/ >Also click on the "more information line" for further reading. > >Bill....WB6BNQ > > >"Dr. David Kirkby" wrote: > >> On 07/12/11 02:15 AM, Tim Tuck wrote: >> > Hi all, >> > >> > Just wondering how many people have used John Miles work @ >> > http://www.ke5fx.com/tbolt.htm, or similar, to discipline a rubidium >> > oscillator and if so... >> > >> > 1. what was the RB of choice ? >> > 2.have any measurements of phase noise etc. been published on such a rig ? >> > 3. Are there any published how-to's etc. available ? >> > >> > I'd like to build such a beast as my lab standard so any help appreciated. >> > >> > thanks >> > >> > Tim >> >> I'm no expert on this, but I believe that the rubidiums have poorer phase noise >> than crystals, so unless holdover performance is an issue, there is no advantage >> in using a rubidium over a crystal as long as GPS lock is maintained at all times. >> >> The Stanford PRS-10 rubidium looks to be quite nice, as it has a 10 MHz crystal >> to give good phase noise and also the rubidium for medium term stability. It can >> be disciplined easily, as it has a 1 pps input. >> >> Alas the PRS-10 is not as plentiful (i.e. cheap) as some other rubidiums. >> >> There may be better ways, but a PRS-10 and a timing receiver which outputs 1 pps >> looks to be a relatively easy way to get the short term peformance of a crystal, >> the medium term performance of a rubidium should the GPS get unlocked and the >> long term stability of GPS. >> >> I'm looking for a lab standard too, so I'd be interested in what other replies >> you get. For me personally, for a short term solution, I'm thinking of using an >> undisciplined rubidium. >> >> -- >> A: Because it messes up the order in which people normally read text. >> Q: Why is top-posting such a bad thing? >> A: Top-posting. >> Q: What is the most annoying thing in e-mail? >> >> _______________________________________________ >> 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. > >__________ Information from ESET Smart Security, version of virus signature database 5851 (20110206) __________ > >The message was checked by ESET Smart Security. > >http://www.eset.com _______________________________________________ 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.
