[time-nuts] WWVB PM Time Questions

[Ben Bradley]

I saw this the other day but not sure if this was answered:

> 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."

I interpret this as saying when you're syncing with the transmitted
signal, you only do so while it's at the high amplitude. At other
times you're generating the signal without external sync, and using
this locally generated signal to compare with the phase of the
received signal.

This is similar to how the color-burst of the (now-obsolete analog)
NTSC TV color signal works.

I'm thinking this would all be done in software on an ARM
microcontroller. The local 60kHz would be generated using a software
DDS. I recall others discussed at least some aspects of this.