Hello Ernie, please allow me to correct your use of my first name. It is "Ulrich" and not "Ulbrich". I attach great importance to this difference because a certain Walter Ulbricht was one of the leading politicians in the communist terror regime of the former so called "German Democratic Republic" and I do not want my name to sound even similar to his one.
> Understand that the key point is the PLL or the phase > comparator circuit.........if you want to build you own GPS-DO..... As far as I remember I had understood this when I started my DIY GPSDO project. If you have not read about it yet take it as an indication that I did not want to publish it. Nevertheless you can see some pictures of it in the photo gallery http://www.ulrich-bangert.de/html/photo_gallery_1.html of my homepage. > can you please be a more specific.... namely to show > us the pre filter and other circuit....if you do not mind. The Pll as well as the pre filter is SOFTWARE and not hardware as your question may imply. Again I have to use the P-word because the software was written in PASCAL. The pre filter and the PLL part reads like: procedure ComputePreFilter; begin; PrefilterValue:=PrefilterValue*PreFilterTimeconstant +PhaseDelay*(1-PrefilterTimeConstant); Str(PreFilterValue,PreFilterValue_S); end; procedure DoPll; var count:integer; flag:boolean; sum:Extended; begin; if DoPrefilter then PllPhaseValue:=PrefilterValue else PllPhaseValue:=PhaseDelay; TimeConstant:=Sqr(NaturalTimeConstant)*(KDet*KVco); If NeueZeitKonstante then begin; NeueZeitKonstante:=False; Sum:=PropValue+IntegralValue; PropFactor:=2.0*StabilityFactor/Sqrt(KDet*KVco*TimeConstant); PropValue:=PropFactor*PLLPhaseValue*1.0E-9*KDet; IntegralValue:=Sum-PropValue; end; PropFactor:=2.0*StabilityFactor/Sqrt(KDet*KVco*TimeConstant); PropValue:=PropFactor*PLLPhaseValue*1.0E-9*KDet; IntegralValue:=IntegralValue+PllPhaseValue*1.0E-9/TimeConstant*KDet; begin; TuningWord:=SollTuningWord-(PropValue+Integralvalue)*KVco/PllFactor; FiltTuningWord:=(1-0.2)*FiltTuningWord+0.2*TuningWord; TuningWord:=FiltTuningWord; StoreTuningword:=TuningWord; MakeTuningBinary(TuningWord); count:=0; repeat SetFrequency_9852; flag:=GetFrequency_9852; if flag=false then Inc(DDSRWError); inc(count); until flag or (count>9); str(DDSRWError,DDSRWError_S); Strip(DDSRWError_S); if count>1 then MessageLog('DDS Read/Write Error'); if flag=false then ErrorLog('Unable to set DDS frequency'); StoreM41T56_TW; end; end; The initialization is: PreFilterTimeConstant:=1-6/NaturalTimeConstant; Both procedures are executed once per second. Read "If NeueZeitKonstante then" as "If the user has set a new PLL time constant then do". If you can gain a certain understanding for the source then terms like "SetFrequency_9852;" or "flag:=GetFrequency_9852;" will indicate you that instead of an analogue steering of the OCXO my project used a AD9852 DDS circuit to steer the output frequency the digital way. For that reason it could steer anything from simple xtals to rubidiums and cesiums without the slightest interaction with the circuitry of the oscillator itself which made me call the device AOS (Arbitrary Oscillator Synchronizer). The "microcontroller" used was a BECK SC12 and you can read more about it here: http://www.beck-ipc.com/en/products/index.asp For a lot of people this may seem a strange choice but beware: If you want to handle 48 bit tuning words you should take care that your micro/compiler combination is able to handle 64 bit entities. Before I gained access to the IAR C compiler for the AVR range of microcontrollers the Turbo Pascal that I could run on the Beck was the only environment available for me which featured 64 bit "extended" floating point entities and 64 bit "cardinal" integer entities. The phase comparator was a simple TIC with a delay line interpolation to 56 ps resolution in an ALTERA EPF10K10 cpld. This cpld (although specified with some ns pin to pin delay) had a very fast internal "carry chain" logic (neccessary for multi byte adders for example) and the carry chain elements could be used as a fast delay line for the time interpolator. > Understand that the key point is the PLL or the phase > comparator circuit.........if you want to build you own GPS-DO..... Among the key points for a good GPSDO are some things that have never been discussed here, for example how to detect and reject outliers in the phase measurements. Outliers are anything else then extraordinary and a single outlier may push the pll's integrator value into outer space so we MUST detect them before the can fire up a desaster. Unfortunately detecting outliers is anything else than trivial and a science of it's own called "robust statistics" tells us how to do. For that reason be prepared to learn more than you really want. Best regards Ulrich > -----Ursprungliche Nachricht----- > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] Im Auftrag von Erno Peres > Gesendet: Samstag, 31. Marz 2012 15:10 > An: time-nuts@febo.com > Betreff: Re: [time-nuts] CW12-TIM vs M12M and the world > > > > Hi Ulbrich, > > Sorry but not everybody a digital and/or a professional > guru... can you please be a more specific.... namely to show > us the pre filter and other circuit....if you do not mind. > Understand that the key point is the PLL or the phase > comparator circuit.........if you want to build you own GPS-DO..... > > Many thanks and best regards, > > Ernie. > > > > > -----Original Message----- > From: Ulrich Bangert <df...@ulrich-bangert.de> > To: 'Discussion of precise time and frequency measurement' > <time-nuts@febo.com> > Sent: Sat, Mar 31, 2012 2:53 pm > Subject: Re: [time-nuts] CW12-TIM vs M12M and the world > > > Bert, > sometimes a manual can be a true treasure chest! Just > download the PRS-10 anual at > http://www.thinksrs.com/downloads/PDFs/Manuals/PRS10m.pdf > and find starting on page 13 the complete instructions on how > to build your wn GPSDO. A basic knowledge of math, > programming and control theory is eeded to understand the > manual but then: It works. I have constructed my own DIY > GPSDO on the base of the information that I have found there, > ncluding the pre-filter. Best regards lrich > > -----Ursprungliche Nachricht----- > Von: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] Im Auftrag von ewkeh...@aol.com > Gesendet: Samstag, 31. Marz 2012 13:46 > An: time-nuts@febo.com > Betreff: Re: [time-nuts] CW12-TIM vs M12M and the world > > > Ulrich > can you tell us more about your pre filter? > Thank you > Bert Kehren > > > In a message dated 3/31/2012 6:23:49 A.M. Eastern Daylight Time, > df...@ulrich-bangert.de writes: > > Thomas, > > > Has anyone compared the M12M to the M12+? > > I have done some measurements on the M12+ with typical > results as shown in > > http://www.ulrich-bangert.de/M12Performance.jpg > > The red line is the raw phase data of the M12's PPS against > a PPS derived from a local FRK-L rubidium. Note that you do > not observe an overall difference frequency (and a resulting > drift in phase) because the FRK-L is disciplined by the GPS. > The blue line is the sawtooth corrected phase data and it > becomes immediatly clear HOW IMPORTANT applying the > correction is. The yellow line show you what happens if the > sawtooth corrected phase data is sent through a pre-filter > (lowpass with 1/3 the time constant of the > main > pll loop) before entering the loop itself. That is something > that I learned from the PRS-10 manual. You may decide on > your own which data you would > like > to work on in a GPSDO. > > Best regards > Ulrich Bangert > > > -----Ursprungliche Nachricht----- > > Von: time-nuts-boun...@febo.com > > [mailto:time-nuts-boun...@febo.com] Im Auftrag von Tom > Knox > Gesendet: Freitag, 30. Marz 2012 22:19 > An: > Time-Nuts > Betreff: Re: [time-nuts] CW12-TIM vs M12M and > the world > > > > > > > Has anyone compared the M12M to the M12+? > > Thanks for all the input, it is really appreciated. > > best wishes; > > Thomas Knox > > > > > > > > > CC: time-nuts@febo.com > > > From: saidj...@aol.com > > > Date: Fri, 30 Mar 2012 09:53:17 -0700 > > > To: time-nuts@febo.com > > > Subject: Re: [time-nuts] CW12-TIM vs M12M and the world > > > > > > Hello Ed, Azelio, > > > > > > We should also compare the same parameters. Sawtooth > error > of the m12+ > > of +/-25ns is not its standard > deviation, it's max/min. > Compare that > > number to your > 30ns max/min measurement on the 5372a. > > > > > Standard deviation of the m12+ is around 2ns with > correction. That > > > needs to be compared to the 5ns you measure on the 5372a > as that is > > > the best performance you will get from the CW12. Yes the > > uncorrected > > > 1pps of the m12 is worse, but it is designed to be used > with > > correction. So in the end the m12m still performs better > than the > > > CW12. > > > > > > Bye, > > > Said > > > > > > Sent From iPhone > > > > > > On Mar 29, 2012, at 1:56, Azelio Boriani > <azelio.bori...@screen.it> > > > wrote: > > > > > > > We (that is my company) use the CW12-TIM (NMEA > version) > and its PPS > > > > wonders as usual, nothing different from a uBlox > LEA-5T > or the M12M. > > > > > > > On Thu, Mar 29, 2012 at 9:32 AM, Hal Murray > > > > <hmur...@megapathdsl.net> wrote: > > > > > > > >> > > > >>>> The sawtooth error on the Motorola M12+ is about > +/- > 25ns, while > > >>>> the CW12-TIM has a sawtooth > error of +/- 2 ns, so > correcting for > > >>>> the > sawtooth error is not as critical with the CW12-TIM. > > >> > > > >>> The first claim > > > >>>> The sawtooth error on the Motorola M12+ is about > +/- 25ns > > >>> is correct but are you absolutely sure that the > second claim is > > > >>> correct too????? > > > >> > > > >>> It would mean a factor >10 improvement of the > CW12-TIM > against the > > >>> M12 > > >> which > > >>> > is hardly believeable. > > >> > > > >> The 25 ns probably comes from period of the the free > > running clock > > > >> they are using. It doesn't seem unreasonable to me > to get 10x > > > >> better if they use a GPSDO for the local clock so > they > can get the > > >> PPS edge right where they want > it. > > >> > > > >> > > > >> > > > >> -- > > > >> These are my opinions, not necessarily my > employer's. I > hate spam. > > >> > > > >> > > > >> > > > >> > > > >> _______________________________________________ > > > >> 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. > > ______________________________________________ > ime-nuts mailing list -- time-nuts@febo.com > o unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > nd 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.