Try looking up the "Costas Loop" and the "frequency doubling loop". They should give you some ideas of how to generate a stable local reference.
Dana On Tue, Jul 21, 2020 at 7:47 PM <rcb...@atcelectronics.com> wrote: > I want to decode the WWVB time information using the BPSK information > that is broadcast. I will use a STM32 to do the actual decoding of the > bit stream. This is just an exercise in "can I do it?" as I know I can > buy clocks for $30 that use the BPSK method. At one time you could buy > an IC that output the data stream but I believe there is nothing > currently available to do that. > > I read the document "Enhanced WWVB Broadcast Format" by John Lowe from > NIST. One thing that is confusing to me is this paragraph: "Although the > phase representing the information in each symbol is shown to be > available before the amplitude in it transitions from VH to VL, it is > recommended that receivers extract it only from the high amplitude > portion of the symbol. This is not only because of the higher power > there, allowing for more robust phase demodulation, but also because the > low amplitude portion may be used in the future for additional (higher > rate) phase modulation." > > How would you detect the phase had changed if you don't detect it when > it changes at 100 msec after the carrier level drops? After the signal > reverses phase wouldn't any reference you are using then be in lock with > the current phase of the signal after it has changed? > > Or would you use a locally generated 60 kHz ultra stable signal as the > phase reference? If so, how would you keep your local source locked to > the 0 degree phase signal of WWVB and have it ignore the 180 degree > phase shift? > > I have done a lot of searching and reading from various sources. But I > haven't really found a good explanation of the hardware that would be > used to detect the phase changes. Is there a block diagram somewhere > that would illustrate the steps needed to detect the change during the > high power portion of the WWVB signal? > > I am going to put together a 60 kHz amplifier using a couple of > FET/transistors and a couple of high speed opamps. Then I can observe > the signal on my scope. Using the output of the amp I can then try to > figure out the best way to detect the phase changes. I can use my AWG to > supply the local 60 kHz signal source. > > I have found two articles that give me some ideas. One is the Nov/Dec > QEX article by John, KD2BD and the other is an article titled WWV > de-PSK-r by Paul, WB8TSL. Paul is a member of this list. > > Can someone make other suggestions that will get me pointed in the > correct direction? > > Thanks, > Ray, AB7HE > > _______________________________________________ > 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.