It's a custom LF receiver I put together, a direct conversion downconverter to 1kHz. Then bandpass sampling to an I/Q data steam, at 12 bit resolution sent using RS422 o a PC. All frequency conversion and sampling is locked to a master 10MHz clock. The interface also includes time stamping from a GPS module.
PC software takes the data steam, applies a small optional frequency offset, needed to take out DDS frequency setting resolution, displays raw input on a vector scope. It then decimated filters the data down to sampling rate in teh Hz to sub-Hz region for storage and further analysis of display. I originally designed the S/W for use with the Ebnaut LF data comms work, hence the reference to .WAV files with time stamped file names but its more use as a general tool for monitoroing LF signals. You can find details here http://g4jnt.com/Coherent_LF_Receiver.pdf and there's a better write up in Jan 2021 edition of RadCom (RSGB Members' magazine) Andy www.g4jnt.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Fri, 15 Jan 2021 at 23:55, paul swed <[email protected]> wrote: > What was the program that you used for the plot please? > Regards > Paul > WB8TSL > > On Fri, Jan 15, 2021 at 5:54 PM Andy Talbot <[email protected]> wrote: > > > I did a plot of the phase of the UK 198kHz longwave transmission to me, a > > path of about 150km, compared against an HP5061A Caesium standard > > N > > > > early 24 hours duration, covering night time and day time propagation in > > October. > > > > You can observe the wild wandering of both phase and amplitude during > > night time due to skywave/groundwave interaction as the ionosphere shifts > > around. > > > > Plot also at > > http://www.g4jnt.com/DropF/droitwichplot2a.bmp > > if the attachment doesn't get through > > > > > > [image: DroitwichPlot2a.bmp] > > Andy > > www.g4jnt.com > > > > > > > > < > > > http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail > > > > > Virus-free. > > www.avg.com > > < > > > http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail > > > > > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > > > On Fri, 15 Jan 2021 at 21:55, Gilles Clement <[email protected]> wrote: > > > > > Hi JF, > > > DCF77 is more distant, less powerful and probably more polluted > (77kHz). > > > Anyhow I would probably not be able to measure better than 10e-11 with > > > current setup (need a better reference) > > > Indeed a good and stable phase lock was not easy to reach. > > > I experienced the day and night huge differences (as documented in > post) > > > but nothing specific to phase shifts during sunrise or sunset. > > > No big difficulties with the ferrite antenna and the receiver design > > > either (thanks to good stuff from the old radio days probably). > > > Found that magnetic field antenna (ie: ferrite) appeared much less > > > sensitive to pollution than electric field antennas. > > > Naturally bad experience with Led bulbs and vapor gas lamps. You have > to > > > chase them all and change to old filament lamps in and around the lab. > No > > > issues with computers though. > > > What I found most challenging (and hence interesting) was the > following : > > > - Temperature control, high resolution and high stability (Crystal > > > oscillator but also for the controller parts, ADC, DAC… ) > > > - PI loop stability (very tricky) > > > - Matching theory with practice (still work in progress…!) > > > - Understanding the logic and physics behind behaviors, the real root > > > cause of problems, > > > and especially why a « really clever » enhancement - more than often - > > > actually leads to… performance degradation... > > > Gilles. > > > > > > > > > > > > > Le 15 janv. 2021 à 16:57, JF PICARD via time-nuts < > > > [email protected]> a écrit : > > > > > > > > Hi, > > > > 800Kw according to the press release of ANFR. I doubt it is the best > > > choice : DCF77 is more precise (active hydrogen maser) but a little bit > > > more distant... > > > > But the phase lock of a quartz on a VLF signal is not as easy. There > is > > > a considerable phase shift in the evening and in the morning with the > sun > > > position, big instabilities at these moments and you have a hudge > > > difference between day and night (10 e-9/8)... Have a look at the Adret > > > receiver 4101 with its step motor phase lock...The engineering of the > > > ferrite road antenna is very tricky : temperature coefficient of the > > > ferrite, subtle tiny out of resonnace tuning, problem of the > > interferences > > > from domestic electrnic pollution (computers with sync of monitors, led > > > drivers...). The archiyecture of the receiver is also tricky : no AGC > > > (introduces phaseshift), heavy filtering (where : antenna, receiver...) > > > > On Friday, January 15, 2021, 03:54:40 PM GMT+1, Gilles Clement < > > > [email protected]> wrote: > > > > > > > > Hi, > > > > > > > > This is to share current results on a "Long Wave RadioFrequency > > > Standard" project I have been pursuing for a while. > > > > Attached are typical ADEV plots and a block diagram of the system. > > > > > > > > I live in a crowded city (Paris, France) with no - or very limited - > > > access to open sky. Not good for GPS. > > > > However a long wave broadcasting public service is (still) available, > > > broadcasting time signal for clocks. > > > > The transmitter is located in Allouis, central France (200km for > > Paris). > > > > The signal is quite powerful (1MW) and the carrier (162kHz ) is > > > stabilized with a Cesium-standard. > > > > > > > > I decided to test how far I could go in disciplining a local VCO with > > > this signal. > > > > > > > > As well known, long wave RF has interesting features: > > > > - Signal is available (almost) everywhere, anytime, in the country > > > especially inside buildings (even underground !) > > > > - Quite stable and strong ground wave in day time. > > > > - Relatively easy antenna and RF signal processing (ferrite rod) > > > > And there are naturally a number of drawbacks (especially with the > > > Allouis signal) such as: > > > > - Much more unstable signal at night (interferences with ionospheric > > > path) > > > > - Large phase modulation of the carrier (time signals bits +/- 1 rad > > > phase modulated). > > > > - RF perturbations on the signal path. > > > > -Stop broadcasting for maintenance every Tuesday morning…. > > > > > > > > Design of the « LWRFDO » was derived and inspired from many > references > > > (including this list naturally). > > > > Principles are summarized in the attached pdf, with the following > > > specific feature to get rid of the phase modulation: > > > > The incoming signal has large sections of « un-modulated » segments > > > between the time signal bits. > > > > (Including a whole quiet section during the 59th second) > > > > Such « quiet zones » are detected - where the 162kHz base carrier is > > > untouched - and measurement of phase difference > > > > with a local OCXO is then performed inside these quiet zones. Then PI > > > controller to a 20bits DAC (see picture). > > > > > > > > Latest results show ADEV approaching 10E-11 at 1000 seconds on the « > D2 > > > » graph (day time only). > > > > « DN123 » is a three days uninterrupted run, combining day and night > > > signals, showing the impact of night instabilities. > > > > The frequency standard stability at the transmitter site is given > for > > > 10e-12. > > > > LWRFDO PPS is measured against an HP10811A PPS (about 10e-11 > stability > > a > > > 100s) with a TICC, > > > > So I believe 10-11 is not far from the best one could get. > > > > Which is actually not too bad, isn’t it ? > > > > > > > > Still working on improving the OCXCO (currently home brewed) > > > > > > > > Comment and suggestions welcomed, > > > > Gilles. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > 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. > > > > > > > < > > > http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail > > > > > Virus-free. > > www.avg.com > > < > > > http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail > > > > > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > _______________________________________________ > > 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. > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> _______________________________________________ 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.
