Well John perhaps there is some interest in your receiver. I see the vcTCXO is down by 5 devices from yesterday. Make that 6 now. For anyone else usps is cheapest at $4.99. Regards Paul
On Thu, Jul 30, 2020 at 10:29 AM paul swed <paulsw...@gmail.com> wrote: > Hello to the group. > Poul has done some very fine work and you can learn a lot from him. > But several comments that will help. Its easy to create all kinds of > solutions that look for phase shifts. I spent quite a bit of time doing > that. But the nasty reality is without accounting for the noise, signal > fades, and delay shifts they generally fail. Or work for short periods of > times. > Simplistically if you have a 1 second image of the incoming signal its > easy to see the phase shift. > With respect to zero crossings it works really poorly. Thats why on Loran > C they were very clear the slice point was as I recall 30% up the envelope. > > Humor on the d-psk-r. The new unit does not have an output that contains > the phase shifts of wwvb. The units intention is to remove all phase shifts > so that all old style phase tracking receivers and clocks work. They all > do. Have 7 of them. > So to experiment with Johns fine KB2DB receiver I need the raw phase > flipping wwvb signal. > I have built his receiver and now that there is an answer to the TCXO > issue I need a raw feed. Chuckle. When I built the new unit I really > debated adding that BNC. Hindsight is always really clear. > Best regards > Paul > WB8TSL > > > On Thu, Jul 30, 2020 at 4:48 AM Poul-Henning Kamp <p...@phk.freebsd.dk> > wrote: > >> -------- >> rcb...@atcelectronics.com writes: >> > Paul, >> > "The new de-psk-r I built has no raw wwvb outputs." What do you mean by >> > raw? >> > >> > I have been thinking about how the phase shift could be detected in >> > software instead of hardware. Could something like this maybe work: >> >> Back when I played with VLF, I did this on DCF77/Rugby etc. >> >> In my case I used a 12 bit 1MSPS ADC, and (exponentially) averaged >> the RF signal into per-station circular buffer, this is very cheap >> and fast to do in an interrupt handler. >> >> In your main code you can demodulate that buffer to DC by multiplying >> and summing with precomputed sin&cos tables. >> >> That gives you baseband I & Q from which you can trivially calculate >> phase and amplitude. >> >> You can make the buffer as short or long as you want, I did the >> trivial thing and made it a full second long: >> >> http://phk.freebsd.dk/loran-c/CW/ >> >> The trick to that is that you can recover many stations from the >> same circular buffer, by using different sin&cos tables. All the >> above plots came out of the same single 1sec buffer snapshot. >> >> This obviously works for any buffer length which is a full number >> of carrier cycles for all the stations you are interested in, in >> principle you can recover all stations on N*kHz, N << 500 from from >> a single 1000 sample buffer at 1MSPS. >> >> The advantage of using a 1second buffer was that I could extract >> what the stations thought was top of the second from their modulation. >> >> (I actually calculated my position based on DCF77, Rugby, HBG, >> France Inter and the strange 200/3 kHz station in Moscow, the result >> I got was about half a kilometer wrong.) >> >> To recover the per-second modulation you simply need to shorten the >> buffer so it resolves the modulation, which probably means no longer >> than 1/20 second for WWVB, but 1/100, if you have the S/N for it, >> is much easier in terms of signal analysis code. >> >> An alternative strategy, which I used for DCF77 phase recovery, is >> to detect the duration of the AM pulse and pick one of two 1-second >> long buffers based on that. >> >> And you don't need much CPU power at all, I did Loran-C time/freq >> on a Analog Devices Aduc7206: >> >> http://phk.freebsd.dk/AducLoran/ >> >> And that included a graphical display, (watch the animation.gif :-) >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> p...@freebsd.org | 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 -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.