Dear Ole, Very interesting comments, thanks. I am currently servoing a home brewed local 162kHz oscillator to the incoming radio signal. The phase difference looks quite clean during day time (ground wave propagation), but quite dirty at night, (additional fading of such long wave signals at night ?). Allows me to remove the time phase modulation, and reach reasonable results.
What i am planning to do with the 81 divider, is to compare current output with a « good » 10MHz OCXO (10811) to check with a TIC. I am (was) also, indeed, planning to try direct HF signal division to servo the 10 MHz OCXO. But this may not work well, as you experienced... Best, Gilles. > Le 21 juin 2020 à 16:14, Ole Stender Nielsen via time-nuts > <[email protected]> a écrit : > > Dear Gilles, > > If I understand you correctly you will take the French time signal at 162 kHz > and divide the frequency with 81 in an attempt to compare two 2 kHz signals, > one originating from the time signal, and another from an OCXO. > > However, I would advice not to take the 162 kHz signal and try to divide it > with 81. The 162 kHz signal you pick off the air is an analog signal, and it > will suffer from all kinds of unwanted noise, dips and multipath phenomena. I > assume you plan to condition the signal so that you can feed it to a digital > divider. However, this is an invitation to cycle slips and jumps. > > An off-air frequency reference receiver like the Halcyon OFS-1 fed an > amplified and filtered 162 kHz signal directly to a divider, and the > resulting performance was awful. Take a look at > https://dabbledoo.weebly.com/halcyon-ofs-1.html > > If you live very close to the transmitter site, it may work to condition and > then divide the 162 kHz signal, but if not, you will not be happy. > > Best regards > Ole > >> Den 21-06-2020 kl. 09:30 skrev Gilles Clement: >> Hi, >> Comparing a reference signal at 162kHz with local 10MHz ocxo. Expected Adev >> 10E-11 at 10sec. >> 162kHz / 81 = 2kHz = 10MHz / 5000 >> GC >> >>>> Le 21 juin 2020 à 05:49, Bob kb8tq <[email protected]> a écrit : >>> >>> Hi >>> >>> *Any* divide approach followed by a flip flop clocked by the input clock >>> will meet >>> that same basic requirement. While it *sounds* like it would improve >>> things, it >>> very much depends on the details. >>> >>> What are you trying to do? What is the input frequency? What is the phase >>> noise >>> requirement? >>> >>> Bob >>> >>>> On Jun 20, 2020, at 2:22 PM, Gilles Clement <[email protected]> wrote: >>>> >>>> Hi Robert, >>>> You are right, its the lambda divider that was discussed. Need to better >>>> understand this approach.... >>>> 74HC40103 could also do the 81 Pi-divide easily, but I tend to prefer the >>>> PICDIV concept where the controller is clocked by the signal to divide (So >>>> limited or no noise is added). AVR family could do it, as most of the >>>> instructions take only one clock. >>>> Gilles. >>>> >>>> >>>>>> Le 20 juin 2020 à 19:48, Robert LaJeunesse <[email protected]> a écrit >>>>>> : >>>>> Gilles, if I read the Calosso-Rubiola paper correctly a Pi divider is >>>>> pretty much your standard square-wave producing digital divider, such as >>>>> a 74163 (for even divides). There's odd-value (3,5,7) Pi dividers shown >>>>> at >>>>> https://www.theremin.us/Circuit_Library/symmetrical_digital_dividers.html. >>>>> What the Calosso-Rubiola paper promotes is the Lambda divider, which is >>>>> depicted in figure 2 of the paper. >>>>> >>>>> Bob L. >>>>> >>>>>> Sent: Friday, June 19, 2020 at 10:27 AM >>>>>> From: "Gilles Clement" <[email protected]> >>>>>> To: "Poul-Henning Kamp" <[email protected]> >>>>>> Cc: "Discussion of precise time and frequency measurement" >>>>>> <[email protected]> >>>>>> Subject: Re: [time-nuts] Frequency division by 81 >>>>>> >>>>>> Hi, >>>>>> Could you point me to a practical design example of a Pi divider ? >>>>>> >>>>>> >>>>>> Envoyé de mon iPad >>>>>> >>>>>>>> Le 19 juin 2020 à 08:56, Poul-Henning Kamp <[email protected]> a >>>>>>>> écrit : >>>>>>> -------- >>>>>>> >>>>>>>> I need to divide the output of an OCXO by a factor D=81 for testing >>>>>>>> purposes. So with minimum added phase noise. >>>>>>> Two stages of divide by 9 PI-dividers ? >>>>>>> >>>>>>> http://rubiola.org/pdf-articles/conference/2013-ifcs-Frequency-dividers.pdf >>>>>>> >>>>>>> -- >>>>>>> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >>>>>>> [email protected] | TCP/IP since RFC 956 >>>>>>> FreeBSD committer | BSD since 4.3-tahoe >>>>>>> Never attribute to malice what can adequately be explained by >>>>>>> incompetence. >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- [email protected] >>>>>> To unsubscribe, go to >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>> and follow the instructions there. >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
