[time-nuts] WWVB PM Time Questions

[rcbuck at atcelectronics.com]

I have been playing with the 74HCT4046 PLL over the last couple of days.
I have the VCO running at 90 Hz and my AWG running at 90 Hz as the input
source to lock the loop. The AWG is modulating the 90 Hz sine wave with
a PSK signal at a 9 Hz rate.

I slowed the signals down from 60 kHz to 90 Hz to better observe the
phase reversal. I could see the reversal at 60 kHz but could not capture
it for a single sequence photo. Attached is the jpg of what the signal
looks like when it performs a 180 degree reversal. With my AWG the
reversal always occurs at the top or the bottom of the sine wave instead
of at the center like John Lowe shows in the WWVB document.

I ordered parts from Mouser this morning to build the RF front end.
Hopefully I will be able to get a clean enough sine wave from WWVB to
see what their phase reversal actually looks like. Then I will have to
come of with the best/simplest way to detect the change. As was
previously mentioned, the normal phase needs to be detected at the top
of the minute. That means it will take at least 2 and probably 3 minutes
to obtain a valid date/time data transmission.

Ray,
AB7HE

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