Hi Never ever say never to this group when it's an oscillator with an outlandish short term stability ...
If you do, somebody is *bound* to turn up with one. Bob On Feb 6, 2010, at 8:32 PM, WarrenS wrote: > > I've never heard of a 1e-13 at 1sec HP 10811, so it may be MORE than hard to > find. > (again not so hard to fine one at 1e-12 and 0.1 sec) > Agree, a tight PLL is Not as flexible as a heterodyne or a DMTV, and has > other limitations. > Always those darn tradeoffs when you want simple and low cost. > > One trick I've done using the Tight PLL method, if the reference does NOT > have a EFC or it is already used elsewhere such as a GPSDO. > That is to put the feedback on the Device under test, assuming it has a > unused EFC input. > Get same simple block and results, Just need to correct for the Tuning gain > of the tested Osc. > > ws > > ****************** > ----- Original Message ----- From: "Bob Camp" <[email protected]> > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Sent: Saturday, February 06, 2010 4:26 PM > Subject: Re: [time-nuts] ADEV vs MDEV > > > Hi > > I believe the statement: > > "Both systems are equally limited by the reference oscillator" > > was part of the same paragraph as the comment on 10811 short term stability. > > Neither system, no matter how well set up will get below the stability of the > reference oscillator. > > I have indeed read a lot of threads here. I've also tested a *lot* of > oscillators. Finding a 10811 that consistently does <=1.0x10-^13 at 1 second > is *not* an easy task. > > Far more to the point - the tight loop requires a voltage controlled > reference. Weather it's a 10811 or something else, it needs voltage control. > The heterodyne approach does not. You do need to get luck with your > frequencies if the heterodyne reference is not tunable. Something like a > 10811 is indeed needed in a tight lock system. > > Bob > > > On Feb 6, 2010, at 6:55 PM, WarrenS wrote: > >> >> >>> "An ADEV noise floor of 1E-13 isn't likely when using an HP10811A as the >>> VCXO for example." >> >> How quickly one forgets and gets lost on these long topics. >>>> "If you accept that the measurement is going to limited by the Reference >>>> Osc, >>>> for Low COST and SIMPLE, Can't beat a simple analog version of NIST's >>>> "Tight Phase-Lock Loop" " >> >> And which method are you saying is NOT limited by the Reference Osc?? >> Correct, not going to get to 1e-13 at one sec with a HP10811A, >> nor likely with any other Ref Osc that most Freq nuts have. >> SO Seems like that is GOOD enough noise floor limit to use for a "low cost & >> simple" configuration. >> >> BTW >> A well setup "Tight Phase-Lock Loop" method will go below that.. >> and a good HP 10811A can go below 1e-12 at 0.1 sec. (at a bandwidth of 30 Hz) >> >> >> ws >> >> *************** >> Bruce Griffiths said: >> >>> The noise of the OCXO used as a VCXO will limit the noise floor. >>> An ADEV noise floor of 1E-13 isnt likely when using an HP10811A as the >>> VCXO for example. >> >> Bruce >> >> ***** Original Topic ************* >>>> I would appreciate any comments or observations on this topic. >>>> My motivation is to discover the simplest scheme for making >>>> stability measurements at this performance level; this is NOT >>>> even close to the state-of-the-art, but can still be useful. >>>> >>>> Pete Rawson >> >> >> _______________________________________________ >> 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.
