On Sun, Apr 10, 2016 at 01:16:11AM +0000, Bruce Griffiths wrote: > It can easily be done using a variant of the dual conjugate > regenerative divider.
> Feed the 24 MHz signal into the LO port of a mixer.Use a dual > bandpass filters centred on 14MHz and 10MHz to filter the IF > port amplify the outputs of the bandpass filters and drive the > mixer RF port with the combined 10MHz and 14MHz signals. > The 10MHz signal can be extracted from the amplified 10MHz > output via a splitter. > When the loop gain and phasing is correct for both the 10MHz > and 14MHz signals the circuit will produce the required output. > Excess gain is eliminated by the mixers compression of the IF > signal. > The circuitry is all analog with no digital components whatsoever. Thanks Bruce! That is something I do understand, although the original idea was to go from 8MHz to 10MHz, but I presume the 24MHz can be filtered out from the overtones after running the 8MHz signal through a comparator. Cheers, Herbert > Bruce > On Sunday, 10 April 2016 12:10 PM, Will <zl1...@gmx.com> wrote: > Hi all, > I'm fairly new here and might not fully understand things. > Earlier in this thread it was suggested that one lock an 8Mhz > signal to a 10 Mhz signal by analogue methods. > To quote A Plummer: > "and it is relative easy to make 10MHz from 8MHz with analog > frequency manipulation, which generates less jitter > 73" > and H Poetzl asked the same thing as I am: > "On Mon, Apr 04, 2016 at 06:07:54PM -0700, Alexander Pummer wrote: >> and it is relative easy to make 10MHz from 8MHz with analog >> frequency manipulation, which generates less jitter > Could you elaborate on this a little if time permits? > I'm more a 'digital person' but it sounds interesting. > Thanks in advance, > Herbert" > I have not seen how that is done as suddenly the signals are 24Mhz and 10 Mhz > and digital dividers and multipliers are used. > One other point. Attila mentioned using "LEA-M8T". I assume the T suffix > relates to Time rather than the plain GPS. What is the difference? Apart from > 50% higher cost. > Cheers > Will > ZL1TAO >> Sent: Sunday, April 10, 2016 at 7:00 AM >> From: "Bob Camp" <kb...@n1k.org> >> To: ewkeh...@aol.com, "Discussion of precise time and frequency measurement" >> <time-nuts@febo.com> >> Subject: Re: [time-nuts] Advise on building a DIY GPSDO? >> Hi >> Averaged over a long enough time (and without any hanging bridges) the >> frequency accuracy >> will be fine. The frequency accuracy of a 1 pps output on a GPS is “fine” on >> the same basis. Since >> 200 KHz is a “round division” off of any of the likely TCXO’s you will not >> have any jitter or spurs in the “static” >> case. >> Bob >>> On Apr 9, 2016, at 10:07 AM, Bert Kehren via time-nuts <time-nuts@febo.com> >>> wrote: >>> I do not know what U blox does but I know when we use 200 KHz out of the 1 >>> pps output on a $ 10 ublox 6 we consistently get better than 1 E-10 closer >>> to 1 E-11 out of the Morion have the data >>> Bert Kehren >>> In a message dated 4/9/2016 10:01:05 A.M. Eastern Daylight Time, >>> kb...@n1k.org writes: >>> Hi >>>> On Apr 8, 2016, at 9:39 PM, time...@metachaos.net wrote: >>>> Hello Bob, >>>> Friday, April 8, 2016, 6:13:07 PM, you wrote: >>>>> Hi >>>>> If you start from a 24 MHz TCXO (different modules use different TCXO’ >>> s): >>>>> On an 8 MHz output, most of the time you divide by three. >>>>> On a 10 MHz output, you need to divide by 2.4. The net result is that >>> you >>>>> divide by 2 sometimes and 3 other times. >>>>> In the 10 MHz case, there is a *lot* of energy at 12 MHz and 8 MHz, >>> along with >>>>> the 10 MHz output. >>>>> In the 8 MHz case, most of the RF energy is at 8 MHz. >>>>> ==== >>>>> To correct the output by 1 ppm on the 8 MHz output, you need to either >>> drop or >>>>> add one pulse out of every million pulses. Effectively you divide the >>> 24 MHz by >>>>> 2 or by 4 when you do that. You get a bit of 12 MHz or a bit of 6 MHz >>> as a result. >>>> If you know you are doing a 24Mhz and a 10Mhz, why not divide the first >>> by 12 >>>> and the second by 5 and then phase lock the resulting 2Mhz? Or divide by >>> 24 >>>> and 10, respectively and lock the 1Mhz? That way, everything is exact. >>> The bigger problem is that the 24 MHz is *not* exact. It is simply a free >>> running TCXO >>> that happens to be in a GPS module. It has a basic accuracy of +/- 1 ppm >>> or something >>> similar. It is no better or worse than any other TCXO you could buy. >>> To make it accurate they have two choices: >>> 1) Put a voltage control input on the TCXO and turn it into a TCVCXO, then >>> lock it up >>> with a loop. >>> 2) Let the oscillator free run and “fix up” the output. >>> For a variety of reasons, none of the small GPS modules go with option >>> number 1. They >>> all go with option number 2. The 24 Hz error on the (maybe) 24 MHz gets >>> taken out by dropping >>> 24 edges every second. That’s not a lot of edges, it’s not going to turn >>> the output into absolute >>> garbage you can see on a scope. It is plenty of nonsense to mess up a >>> radio or a piece of test gear. >>> One easy way to look at it: You have ~1 ppm jitter on the output (in the >>> example of 1 ppm of error). A >>> phase locked GPSDO with only simple filtering of a 1 pps would get you >>> down to 0.01 ppm of jitter. >>> A sawtooth corrected 1 pps would get you to 0.01 ppm. A good filter would >>> get you to <0.00001 ppm. >>> Yes, I’m using a very hand waving definition of jitter here, but it does >>> illustrate the point. You could >>> look at the jitter on the pulse drop as 0.04 ppm. >>> Bob >>>> Mike >>>>> That can be filtered out with a RF filter. The same is true with a >>> (somewhat more >>>>> complex) filter on the 10 MHz output. >>>>> In addition to the “big” RF spurs, you get a low frequency component >>> to the output >>>>> modulation. You are “phase hitting” the output eight times a second. >>> That gives you >>>>> an 8 Hz sideband along with the further removed stuff. Since it’s not >>> simple / clean >>>>> phase modulation, there are more sidebands than just the few mentioned >>> above. >>>>> What messes things up even more is that you never are quite doing one >>> ppm. You are doing >>>>> corrections like 0.12356 ppm this second and 0.120201 ppm the next >>> second. >>>>> The pattern of pulse drop and add is not as simple as you might hope. >>> The low >>>>> frequency part of the jitter (and it will be there) is no different >>> than the noise on >>>>> a 1 pps output. You still need to do very long time constant (or very >>> narrow band) >>>>> filtering to take it out. >>>>> Bob >>>>>> On Apr 8, 2016, at 7:06 AM, Herbert Poetzl <herb...@13thfloor.at> >>> wrote: >>>>>> On Mon, Apr 04, 2016 at 06:07:54PM -0700, Alexander Pummer wrote: >>>>>>> and it is relative easy to make 10MHz from 8MHz with analog >>>>>>> frequency manipulation, which generates less jitter >>>>>> Could you elaborate on this a little if time permits? >>>>>> I'm more a 'digital person' but it sounds interesting. >>>>>> Thanks in advance, >>>>>> Herbert >>>>>>> 73 >>>>>>> On 4/4/2016 4:27 PM, Attila Kinali wrote: >>>>>>>> On Mon, 4 Apr 2016 17:56:29 -0400 >>>>>>>> Bob Camp <kb...@n1k.org> wrote: >>>>>>>>> The variable frequency output on the uBlox (and other) GPS >>>>>>>>> receivers has come up many times in the past. >>>>>>>>> If you dig into the archives you can find quite a bit of >>>>>>>>> data on the (lack of) performance of the high(er) frequency >>>>>>>>> outputs from the various GPS modules. They all depend on >>>>>>>>> cycle add / drop at the frequency of their free running TCXO. >>>>>>>>> Regardless of the output frequency, that will put a *lot* of >>>>>>>>> jitter into the output. >>>>>>>> That's why you should put the output frequency of the ublox modules >>>>>>>> to an integer divisor of 24MHz. Ie 8MHz works but not 10MHz. >>>>>>>> Attila Kinali >>>>>>> _______________________________________________ >>>>>>> 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. >>>> -- >>>> Best regards, >>>> Timenut mailto:time...@metachaos.net >>>> _______________________________________________ >>>> 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.