[time-nuts] Re: SDR radios - Loran-C & WWV

[Tom Van Baak]

 > Has anyone played around with SDR radios ability to see and use 
Loran-C and WWV signals?

Hi John,

What a coincidence. In the past few days (post 2/29) I've been working 
with another time-nut to debug a vintage WWV clock that messed up the 
leap year and now seems permanently one day ahead. One theory was that 
the clock doesn't do DOY calculations correctly in the 21st century. 
Another is that WWV forgot to set the leap year bit. The latter is easy 
to check, yes?

As it turns out it's only WWVB that has the leap year bit and WWV does 
not. That means WWV receivers must handle leap years on their own, 
checking the low 2 bits of the BCD year. That's not strictly correct, 
and implies WWV will fail in the year 2100. WWVB, on the other hand, 
includes a specific leap year bit so the circuit doesn't need to look at 
BCD year data. As a result it will handle the year 2100 correctly.

As part of this rabbit hole I wanted to see what WWV was actually 
outputting so I connected a portable Sony S/W radio phone-out to my 
laptop rec-in, found 15 MHz was best, turned off my laptop switching 
power supply, recorded a minute of data at 44.1 kHz, fed that into 
Stable32, clicked on "Filter", picked 80 to 120 Hz bandpass, and Voila, 
I got the WWV subcode loud and clear. All 60 bits of data [1] were correct.

Stable32 image attached. After all that hassle, I made a mental note to 
add SDR to my Christmas list. ;-) It sounds like someone could make a 
cool 24x7 logging project using all the WWV frequencies, dynamically 
tracking amplitude and phase, etc.

/tvb

[1] https://en.wikipedia.org/wiki/WWV_(radio_station)

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