[time-nuts] WWVB SDR discussion

[Graham / KE9H]

What would the optimum bandwidth for a WWVB receiver be?

For the AM signal, there are three different symbols, 0.8 seconds on/0.2
sec off; 0.5 sec on/0.5 sec off; and 0.2 sec on, 0.8 seconds off.
This suggests to me that the two non-symmetrical symbols have strong
modulation sidebands at +/- 2.5 Hz, or a minimum (AM-DSB) bandwidth of 5
Hz, plus any frequency tuning error requirements.
This would give me a soft edge with a 100 ms rise and fall time.

The next stop for significant improvement would be to catch the third
harmonic of the AM modulation component, which would require a 15 Hz total
filter bandwidth, plus any frequency tuning errors, and an edge rise and
fall time in the 33 ms range.

 Am I looking at this correctly?

I am assuming that any phase modulation sidebands would fit inside the AM
filter requirements.

--- Graham

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