Jim mentioned the teensy earlier. This led to a couple of interesting links :
This thread describes using the internal trim adjustment to lock the cpu clock frequency onto a VLF transmission https://forum.pjrc.com/threads/35397-Teensy3-1-as-a-precision-Frequency-Standard Two SDR implementations on teensy 3 https://hackaday.com/2014/04/25/building-a-software-defined-radio-with-a-teensy/ https://forum.pjrc.com/printthread.php?t=40590&pp=25 and, not teensy but another sdr for MSF https://www.armms.org/media/uploads/s_day_implementation_of_a_software_defined_radio_for_the_60khz_msf_time_signal.pdf On Wed, Dec 5, 2018 at 11:05 PM Dana Whitlow <[email protected]> wrote: > Here is my capture of a few minutes of WWVB amplitude and phase from last > fall. > It's somewhat larger of a file than I had remembered, more like 3.5MB, and > it has > lots of fine detail. So be prepared for it to take half a minute or so > (maybe more, > depending) before it starts to plot. > > The data was recorded with an SDR-14 SDR, using a DXE broadband loop > antenna. I had to wait until the wee hours to get a decent-looking signal > in > my high-line-noise area (Kerrville, TX). > > The demodulation was done after the capture was complete, in 'C' SW that > I've written to make this kind of signal analysis fairly easy and regular. > Basically > I examine the spectrum of the raw signal using an FFT, and manually pick > the > band limits within which I want to work. Then I shift that band to roughly > zero- > center frequency, and take an IFFT to return to time domain. At this point > the > frequency is invariably a bit off, and I have an interactive graphical > means of > correcting the frequency error pretty accurately. Hence, my "Costas loop" > is > really a manual process to de-tilt the phase versus time plot. > > Normally I quit there, but realized that I needed a better way to plot such > a > long record, so I developed a little program to plot the data in spiral > form to > an EasyCAD file, to which I manually added explanatory text. > > Thanks to TVB for converting my oversize pdf plot to something reasonable. > > Enjoy, > > Dana > > > On Wed, Dec 5, 2018 at 4:29 PM Dana Whitlow <[email protected]> wrote: > > > Here is my capture of a few minutes of WWVB amplitude and phase from last > > fall. > > It's somewhat larger of a file than I had remembered, more like 3.5MB, > and > > it has > > lots of fine detail. So be prepared for it to take half a minute or so > > (maybe more, > > depending) before it starts to plot. > > > > The data was recorded with an SDR-14 SDR, using a DXE broadband loop > > antenna. I had to wait until the wee hours to get a decent-looking > signal > > in > > my high-line-noise area (Kerrville, TX). > > > > The demodulation was done after the capture was complete, in 'C' SW that > > I've written to make this kind of signal analysis fairly easy and > > regular. Basically > > I examine the spectrum of the raw signal using an FFT, and manually pick > > the > > band limits within which I want to work. Then I shift that band to > > roughly zero- > > center frequency, and take an IFFT to return to time domain. At this > > point the > > frequency is invariably a bit off, and I have an interactive graphical > > means of > > correcting the frequency error pretty accurately. Hence, my "Costas > loop" > > is > > really a manual process to de-tilt the phase versus time plot. > > > > Normally I quit there, but realized that I needed a better way to plot > > such a > > long record, so I developed a little program to plot the data in spiral > > form to > > an EasyCAD file, to which I manually added explanatory text. > > > > Enjoy, > > > > Dana > > > > > > On Wed, Dec 5, 2018 at 8:56 AM jimlux <[email protected]> wrote: > > > >> https://www.rtl-sdr.com/tag/vlf/ > >> > >> a fair number of examples - > >> > >> As I speculated, the 8 bit RTL-SDR has a problem with strong broadcast > >> band AM, so you need some sort of LPF. > >> > >> There are some examples of "amplified whip into sound card into Rpi" > >> implementations. > >> > >> I didn't see anybody actually decoding or measuring the phase though - > >> lots of waterfall plots showing the existence of a signal. > >> > >> > >> _______________________________________________ > >> 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.
