On 12/26/2010 09:54 PM, Michael Ossmann 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 Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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