Re: [time-nuts] WWVB phase modulation format?
On Mar 9, 2012, at 4:28 PM, Peter Monta wrote: Interesting that WWVB is running a phase-modulation test---thanks for the links. Is the signal format known? A quick search shows nothing specific, just we're testing. Could someone record a few minutes of the broadband signal so that those of us without ready-to-hand LF receivers can have a look? Cheers, Peter I took a look at this. Pictures and video here: http://jks.com I believe what they were doing is applying a simple 180 deg phase shift to the carrier (BPSK) during certain one second timecode intervals. Whether there was anything fancier going on or not (like what DCF77 does) I couldn't tell immediately, although I did make a 192 ksps sound card recording for future analysis. Apologies for the crude measurement and presentation. I had to throw this together in a hurry. ___ 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.
Re: [time-nuts] WWVB phase modulation format?
On Mar 11, 2012, at 12:53 PM, John Seamons wrote: I took a look at this. Pictures and video here: http://jks.com I believe what they were doing is applying a simple 180 deg phase shift to the carrier (BPSK) during certain one second timecode intervals. Whether there was anything fancier going on or not (like what DCF77 does) I couldn't tell immediately, although I did make a 192 ksps sound card recording for future analysis. Okay, so I did a little analysis of the data. See the website for details. For the few minutes I recorded there was a fixed pattern of phase changes that repeated each minute. They did not seem related to the changing timecode. I tried interpreting the bits as various things, including ascii characters, but no luck. Maybe one of you will figure it out, or I suppose we could ask. ___ 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.
Re: [time-nuts] WWVB phase modulation format?
I believe what they were doing is applying a simple 180 deg phase shift to the carrier (BPSK) during certain one second timecode intervals. I suppose this will help coherent receivers somewhat, but I was expecting something DCF77-like. A pity. Thanks for posting your data. You certainly have good WWVB reception. Attached is a plot of the real part of the demodulated signal after carrier estimation. They change the phase 100 ms after the second marker, halfway between the second marker and a potential change in amplitude back to full power. So the phase transition always occurs in the middle of a low-power interval. Cheers, Peter attachment: wwvb-phase.png___ 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.
Re: [time-nuts] WWVB phase modulation format?
... or I suppose we could ask. I did ask, using the contact email on the NIST page (John Lowe). I'll forward any replies to the list. Perhaps we could encourage a more ambitious DCF77-like scheme, if that's really not in the current plans for WWVB. Especially given the recent demise of Loran-C, a WWVB service with greater timing precision would certainly be welcome as a backup for GPS. Cheers, Peter ___ 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.
