Has anyone on the list worked on a WWVB demodulator?
They basically use a type of ON/OFF keying, with the resulting “pulse
width” used to encode 1s and 0s.
–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
On 12/26/2010 09:54 PM, Michael O. wrote:
I started to years ago but never got very far. It looked like
starting with goertzel was going to work. I think I planned to dump
goertzel output into M&M clock recovery with a 10 Hz symbol rate and
then count the number of .1 second chunks per pulse.mossmann
I’m not too worried about computational efficiency, so I hadn’t
considered Goertzel. My current approach
(that I’ve just developed this evening 
), is to assume a 192KHz
sound card input (which is congruent with
the approach I’m currently using for VLF signal processing for
ionospheric measurements), bandpass filter at
60KHz (+/- 100Hz), then detect the result and data slice into 1s and
0s at 10Hz–the data slicing is driven by
computing a longer-term signal level average (since WWVB basically
uses ON/OFF (well ON, and 10dB down)
keying.
Having a variable that tracks the medium-term average allows the
receiver to track fading and tweak the data slicer
appropriately.
Haven’t decided how I’ll turn the PWM into actual 1s and 0s yet.
–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium