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 -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
